// Copyright 1995-2016 The OpenSSL Project Authors. All Rights Reserved.
// Copyright (c) 2002, Oracle and/or its affiliates. All rights reserved.
// Copyright 2005 Nokia. All rights reserved.
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
//     https://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.

#ifndef OPENSSL_HEADER_SSL_H
#define OPENSSL_HEADER_SSL_H

#include <openssl/base.h>  // IWYU pragma: export

#include <openssl/bio.h>
#include <openssl/buf.h>
#include <openssl/pem.h>
#include <openssl/span.h>
#include <openssl/ssl3.h>  // IWYU pragma: export
#include <openssl/tls1.h>  // IWYU pragma: export
#include <openssl/x509.h>

#if !defined(OPENSSL_WINDOWS)
#include <sys/time.h>
#endif

// Forward-declare struct timeval. On Windows, it is defined in winsock2.h and
// Windows headers define too many macros to be included in public headers.
// However, only a forward declaration is needed.
struct timeval;

#if defined(__cplusplus)
extern "C" {
#endif


// SSL implementation.


// SSL contexts.
//
// `SSL_CTX` objects manage shared state and configuration between multiple TLS
// or DTLS connections. Whether the connections are TLS or DTLS is selected by
// an `SSL_METHOD` on creation.
//
// `SSL_CTX` are reference-counted and may be shared by connections across
// multiple threads. Once shared, functions which change the `SSL_CTX`'s
// configuration may not be used.

// TLS_method is the `SSL_METHOD` used for TLS connections.
OPENSSL_EXPORT const SSL_METHOD *TLS_method(void);

// DTLS_method is the `SSL_METHOD` used for DTLS connections.
OPENSSL_EXPORT const SSL_METHOD *DTLS_method(void);

// TLS_with_buffers_method is like `TLS_method`, but avoids all use of
// crypto/x509. All client connections created with `TLS_with_buffers_method`
// will fail unless a certificate verifier is installed with
// `SSL_set_custom_verify` or `SSL_CTX_set_custom_verify`.
OPENSSL_EXPORT const SSL_METHOD *TLS_with_buffers_method(void);

// DTLS_with_buffers_method is like `DTLS_method`, but avoids all use of
// crypto/x509.
OPENSSL_EXPORT const SSL_METHOD *DTLS_with_buffers_method(void);

// SSL_CTX_new returns a newly-allocated `SSL_CTX` with default settings or NULL
// on error.
OPENSSL_EXPORT SSL_CTX *SSL_CTX_new(const SSL_METHOD *method);

// SSL_CTX_up_ref increments the reference count of `ctx`. It returns one.
OPENSSL_EXPORT int SSL_CTX_up_ref(SSL_CTX *ctx);

// SSL_CTX_dup_ref increments the reference count of `ctx` and returns the same
// handle.
OPENSSL_EXPORT SSL_CTX *SSL_CTX_dup_ref(const SSL_CTX *ctx);

// SSL_CTX_free releases memory associated with `ctx`.
OPENSSL_EXPORT void SSL_CTX_free(SSL_CTX *ctx);


// SSL connections.
//
// An `SSL` object represents a single TLS or DTLS connection. Although the
// shared `SSL_CTX` is thread-safe, an `SSL` is not thread-safe and may only be
// used on one thread at a time.

// SSL_new returns a newly-allocated `SSL` using `ctx` or NULL on error. The new
// connection inherits settings from `ctx` at the time of creation. Settings may
// also be individually configured on the connection.
//
// On creation, an `SSL` is not configured to be either a client or server. Call
// `SSL_set_connect_state` or `SSL_set_accept_state` to set this.
OPENSSL_EXPORT SSL *SSL_new(SSL_CTX *ctx);

// SSL_free releases memory associated with `ssl`.
OPENSSL_EXPORT void SSL_free(SSL *ssl);

// SSL_get_SSL_CTX returns the `SSL_CTX` associated with `ssl`. If
// `SSL_set_SSL_CTX` is called, it returns the new `SSL_CTX`, not the initial
// one.
OPENSSL_EXPORT SSL_CTX *SSL_get_SSL_CTX(const SSL *ssl);

// SSL_set_connect_state configures `ssl` to be a client.
OPENSSL_EXPORT void SSL_set_connect_state(SSL *ssl);

// SSL_set_accept_state configures `ssl` to be a server.
OPENSSL_EXPORT void SSL_set_accept_state(SSL *ssl);

// SSL_is_server returns one if `ssl` is configured as a server and zero
// otherwise.
OPENSSL_EXPORT int SSL_is_server(const SSL *ssl);

// SSL_is_dtls returns one if `ssl` is a DTLS connection and zero otherwise.
OPENSSL_EXPORT int SSL_is_dtls(const SSL *ssl);

// SSL_is_quic returns one if `ssl` is a QUIC connection and zero otherwise.
OPENSSL_EXPORT int SSL_is_quic(const SSL *ssl);

// SSL_set_bio configures `ssl` to read from `rbio` and write to `wbio`. `ssl`
// takes ownership of the two `BIO`s. If `rbio` and `wbio` are the same, `ssl`
// only takes ownership of one reference. See `SSL_set0_rbio` and
// `SSL_set0_wbio` for requirements on `rbio` and `wbio`, respectively.
//
// If `rbio` is the same as the currently configured `BIO` for reading, that
// side is left untouched and is not freed.
//
// If `wbio` is the same as the currently configured `BIO` for writing AND `ssl`
// is not currently configured to read from and write to the same `BIO`, that
// side is left untouched and is not freed. This asymmetry is present for
// historical reasons.
//
// Due to the very complex historical behavior of this function, calling this
// function if `ssl` already has `BIO`s configured is deprecated. Prefer
// `SSL_set0_rbio` and `SSL_set0_wbio` instead.
OPENSSL_EXPORT void SSL_set_bio(SSL *ssl, BIO *rbio, BIO *wbio);

// SSL_set0_rbio configures `ssl` to read from `rbio`. It takes ownership of
// `rbio`. `rbio` may be a custom `BIO`, in which case it must implement
// `BIO_read` with `BIO_meth_set_read`. In DTLS, `rbio` must be non-blocking to
// properly handle timeouts and retransmits.
//
// Note that, although this function and `SSL_set0_wbio` may be called on the
// same `BIO`, each call takes a reference. Use `BIO_up_ref` to balance this.
OPENSSL_EXPORT void SSL_set0_rbio(SSL *ssl, BIO *rbio);

// SSL_set0_wbio configures `ssl` to write to `wbio`. It takes ownership of
// `wbio`. `wbio` may be a custom `BIO`, in which case it must implement
// `BIO_write` with `BIO_meth_set_write`. It must additionally implement
// `BIO_flush` with `BIO_meth_set_ctrl` and `BIO_CTRL_FLUSH`. If flushing is
// unnecessary with `wbio`, `BIO_flush` should return one and do nothing.
//
// Note that, although this function and `SSL_set0_rbio` may be called on the
// same `BIO`, each call takes a reference. Use `BIO_up_ref` to balance this.
OPENSSL_EXPORT void SSL_set0_wbio(SSL *ssl, BIO *wbio);

// SSL_get_rbio returns the `BIO` that `ssl` reads from.
OPENSSL_EXPORT BIO *SSL_get_rbio(const SSL *ssl);

// SSL_get_wbio returns the `BIO` that `ssl` writes to.
OPENSSL_EXPORT BIO *SSL_get_wbio(const SSL *ssl);

// SSL_get_fd calls `SSL_get_rfd`.
OPENSSL_EXPORT int SSL_get_fd(const SSL *ssl);

// SSL_get_rfd returns the file descriptor that `ssl` is configured to read
// from. If `ssl`'s read `BIO` is not configured or doesn't wrap a file
// descriptor then it returns -1.
//
// Note: On Windows, this may return either a file descriptor or a socket (cast
// to int), depending on whether `ssl` was configured with a file descriptor or
// socket `BIO`.
OPENSSL_EXPORT int SSL_get_rfd(const SSL *ssl);

// SSL_get_wfd returns the file descriptor that `ssl` is configured to write
// to. If `ssl`'s write `BIO` is not configured or doesn't wrap a file
// descriptor then it returns -1.
//
// Note: On Windows, this may return either a file descriptor or a socket (cast
// to int), depending on whether `ssl` was configured with a file descriptor or
// socket `BIO`.
OPENSSL_EXPORT int SSL_get_wfd(const SSL *ssl);

#if !defined(OPENSSL_NO_SOCK)
// SSL_set_fd configures `ssl` to read from and write to `fd`. It returns one
// on success and zero on allocation error. The caller retains ownership of
// `fd`.
//
// On Windows, `fd` is cast to a `SOCKET` and used with Winsock APIs.
OPENSSL_EXPORT int SSL_set_fd(SSL *ssl, int fd);

// SSL_set_rfd configures `ssl` to read from `fd`. It returns one on success and
// zero on allocation error. The caller retains ownership of `fd`.
//
// On Windows, `fd` is cast to a `SOCKET` and used with Winsock APIs.
OPENSSL_EXPORT int SSL_set_rfd(SSL *ssl, int fd);

// SSL_set_wfd configures `ssl` to write to `fd`. It returns one on success and
// zero on allocation error. The caller retains ownership of `fd`.
//
// On Windows, `fd` is cast to a `SOCKET` and used with Winsock APIs.
OPENSSL_EXPORT int SSL_set_wfd(SSL *ssl, int fd);
#endif  // !OPENSSL_NO_SOCK

// SSL_do_handshake continues the current handshake. If there is none or the
// handshake has completed, it returns one. Otherwise, it returns zero if the
// handshake was interrupted by EOF and -1 on error. If the return value was not
// one, the caller should pass the value into `SSL_get_error` to determine how
// to proceed.
//
// Both a TLS-level EOF (the close_notify alert) and a transport-level EOF
// result in a zero return. `SSL_get_error` can be used to distinguish the two.
//
// TODO(crbug.com/42290000): Replace the two EOF cases with -1 and some error in
// the error queue. Unlike in `SSL_read`, these are both error conditions
// because we were expecting a handshake.
//
// When some features are enabled (TLS 1.2 False Start and TLS 1.3 Early Data),
// application data may be sent or received before the handshake is fully
// complete. In those modes, `SSL_do_handshake` will return one early to signal
// that `ssl` is usable. These features are opt-in. See the corresponding
// features for details on how they impact API behavior.
//
// In DTLS, the caller must drive retransmissions and timeouts. After calling
// this function, the caller must use `DTLSv1_get_timeout` to determine the
// current timeout, if any. If it expires before the application next calls into
// `ssl`, call `DTLSv1_handle_timeout`. Note that DTLS handshake retransmissions
// use fresh sequence numbers, so it is not sufficient to replay packets at the
// transport.
//
// After the DTLS handshake, some retransmissions may remain. If `ssl` wrote
// last in the handshake, it may need to retransmit the final flight in case of
// packet loss. Additionally, in DTLS 1.3, it may need to retransmit
// post-handshake messages. To handle these, the caller must always be prepared
// to receive packets and process them with `SSL_read`, even when the
// application protocol would otherwise not read from the connection.
OPENSSL_EXPORT int SSL_do_handshake(SSL *ssl);

// SSL_connect configures `ssl` as a client, if unconfigured, and calls
// `SSL_do_handshake`.
OPENSSL_EXPORT int SSL_connect(SSL *ssl);

// SSL_accept configures `ssl` as a server, if unconfigured, and calls
// `SSL_do_handshake`.
OPENSSL_EXPORT int SSL_accept(SSL *ssl);

// SSL_read reads up to `num` bytes from `ssl` into `buf`. It implicitly runs
// any pending handshakes, including renegotiations when enabled. On success, it
// returns the number of bytes read. Otherwise, it returns zero on EOF and -1 on
// error. In the latter two cases, the caller should pass the value into
// `SSL_get_error` to determine how to proceed.
//
// Both a TLS-level EOF (the close_notify alert) and a transport-level EOF
// result in a zero return. `SSL_get_error` can be used to distinguish the two.
// Transport-level EOFs are unauthenticated and may be injected by a network
// attacker. However, some ecosystems, such as HTTPS, do not reliably send
// close_notify in practice.
//
// WARNING: If `num` is zero, the success and EOF cases are ambiguous. Callers
// attempting to seek to the next record, without consuming data, should instead
// call `SSL_peek` with a one-byte buffer.
//
// In DTLS 1.3, the caller must also drive timeouts from retransmitting the
// final flight of the handshake, as well as post-handshake messages. After
// calling this function, the caller must use `DTLSv1_get_timeout` to determine
// the current timeout, if any. If it expires before the application next calls
// into `ssl`, call `DTLSv1_handle_timeout`.
OPENSSL_EXPORT int SSL_read(SSL *ssl, void *buf, int num);

// SSL_peek behaves like `SSL_read` but does not consume any bytes returned. A
// subsequent call to `SSL_read` or `SSL_peek` will return the same data.
OPENSSL_EXPORT int SSL_peek(SSL *ssl, void *buf, int num);

// SSL_pending returns the number of buffered, decrypted bytes available for
// read in `ssl`. It does not read from the transport.
//
// In DTLS, it is possible for this function to return zero while there is
// buffered, undecrypted data from the transport in `ssl`. For example,
// `SSL_read` may read a datagram with two records, decrypt the first, and leave
// the second buffered for a subsequent call to `SSL_read`. Callers that wish to
// detect this case can use `SSL_has_pending`.
OPENSSL_EXPORT int SSL_pending(const SSL *ssl);

// SSL_has_pending returns one if `ssl` has buffered, decrypted bytes available
// for read, or if `ssl` has buffered data from the transport that has not yet
// been decrypted. If `ssl` has neither, this function returns zero.
//
// In TLS, BoringSSL does not implement read-ahead, so this function returns one
// if and only if `SSL_pending` would return a non-zero value. In DTLS, it is
// possible for this function to return one while `SSL_pending` returns zero.
// For example, `SSL_read` may read a datagram with two records, decrypt the
// first, and leave the second buffered for a subsequent call to `SSL_read`.
//
// As a result, if this function returns one, the next call to `SSL_read` may
// still fail, read from the transport, or both. The buffered, undecrypted data
// may be invalid or incomplete.
OPENSSL_EXPORT int SSL_has_pending(const SSL *ssl);

// SSL_write writes up to `num` bytes from `buf` into `ssl`. It implicitly runs
// any pending handshakes, including renegotiations when enabled. On success, it
// returns the number of bytes written. Otherwise, it returns -1. In the latter
// case, the caller should pass the value into `SSL_get_error` to determine how
// to proceed.
//
// A zero return is only possible if `num` is zero. If `num` is zero, this
// function will flush any pending control messages, such as NewSessionTicket or
// KeyUpdate, otherwise do nothing, and return zero on success. If `num` is
// greater than zero, it will either successfully write a greater than zero
// number of bytes, or -1 to indicate failure.
//
// In TLS, a non-blocking `SSL_write` differs from non-blocking `write` in that
// a failed `SSL_write` still commits to the data passed in. When retrying, the
// caller must supply the original write buffer (or a larger one containing the
// original as a prefix). By default, retries will fail if they also do not
// reuse the same `buf` pointer. This may be relaxed with
// `SSL_MODE_ACCEPT_MOVING_WRITE_BUFFER`, but the buffer contents still must be
// unchanged.
//
// By default, in TLS, `SSL_write` will not return success until all `num` bytes
// are written. This may be relaxed with `SSL_MODE_ENABLE_PARTIAL_WRITE`. It
// allows `SSL_write` to complete with a partial result when only part of the
// input was written in a single record.
//
// In DTLS, neither `SSL_MODE_ACCEPT_MOVING_WRITE_BUFFER` and
// `SSL_MODE_ENABLE_PARTIAL_WRITE` do anything. The caller may retry with a
// different buffer freely. A single call to `SSL_write` only ever writes a
// single record in a single packet, so `num` must be at most
// `SSL3_RT_MAX_PLAIN_LENGTH`.
OPENSSL_EXPORT int SSL_write(SSL *ssl, const void *buf, int num);

// SSL_KEY_UPDATE_REQUESTED indicates that the peer should reply to a KeyUpdate
// message with its own, thus updating traffic secrets for both directions on
// the connection.
#define SSL_KEY_UPDATE_REQUESTED 1

// SSL_KEY_UPDATE_NOT_REQUESTED indicates that the peer should not reply with
// it's own KeyUpdate message.
#define SSL_KEY_UPDATE_NOT_REQUESTED 0

// SSL_key_update queues a TLS 1.3 KeyUpdate message to be sent on `ssl`
// if one is not already queued. The `request_type` argument must one of the
// `SSL_KEY_UPDATE_*` values. This function requires that `ssl` have completed a
// TLS >= 1.3 handshake. It returns one on success or zero on error.
//
// Note that this function does not _send_ the message itself. The next call to
// `SSL_write` will cause the message to be sent. `SSL_write` may be called with
// a zero length to flush a KeyUpdate message when no application data is
// pending.
OPENSSL_EXPORT int SSL_key_update(SSL *ssl, int request_type);

// SSL_shutdown shuts down `ssl`. It runs in two stages. First, it sends
// close_notify and returns zero or one on success or -1 on failure. Zero
// indicates that close_notify was sent, but not received, and one additionally
// indicates that the peer's close_notify had already been received.
//
// To then wait for the peer's close_notify, run `SSL_shutdown` to completion a
// second time. This returns 1 on success and -1 on failure. Application data
// is considered a fatal error at this point. To process or discard it, read
// until close_notify with `SSL_read` instead.
//
// In both cases, on failure, pass the return value into `SSL_get_error` to
// determine how to proceed.
//
// Most callers should stop at the first stage. Reading for close_notify is
// primarily used for uncommon protocols where the underlying transport is
// reused after TLS completes. Additionally, DTLS uses an unordered transport
// and is unordered, so the second stage is a no-op in DTLS.
OPENSSL_EXPORT int SSL_shutdown(SSL *ssl);

// SSL_CTX_set_quiet_shutdown sets quiet shutdown on `ctx` to `mode`. If
// enabled, `SSL_shutdown` will not send a close_notify alert or wait for one
// from the peer. It will instead synchronously return one.
OPENSSL_EXPORT void SSL_CTX_set_quiet_shutdown(SSL_CTX *ctx, int mode);

// SSL_CTX_get_quiet_shutdown returns whether quiet shutdown is enabled for
// `ctx`.
OPENSSL_EXPORT int SSL_CTX_get_quiet_shutdown(const SSL_CTX *ctx);

// SSL_set_quiet_shutdown sets quiet shutdown on `ssl` to `mode`. If enabled,
// `SSL_shutdown` will not send a close_notify alert or wait for one from the
// peer. It will instead synchronously return one.
OPENSSL_EXPORT void SSL_set_quiet_shutdown(SSL *ssl, int mode);

// SSL_get_quiet_shutdown returns whether quiet shutdown is enabled for
// `ssl`.
OPENSSL_EXPORT int SSL_get_quiet_shutdown(const SSL *ssl);

// SSL_get_error returns a `SSL_ERROR_*` value for the most recent operation on
// `ssl`. It should be called after an operation failed to determine whether the
// error was fatal and, if not, when to retry.
OPENSSL_EXPORT int SSL_get_error(const SSL *ssl, int ret_code);

// SSL_ERROR_NONE indicates the operation succeeded.
#define SSL_ERROR_NONE 0

// SSL_ERROR_SSL indicates the operation failed within the library. The caller
// may inspect the error queue (see `ERR_get_error`) for more information.
#define SSL_ERROR_SSL 1

// SSL_ERROR_WANT_READ indicates the operation failed attempting to read from
// the transport. The caller may retry the operation when the transport is ready
// for reading.
#define SSL_ERROR_WANT_READ 2

// SSL_ERROR_WANT_WRITE indicates the operation failed attempting to write to
// the transport. The caller may retry the operation when the transport is ready
// for writing.
#define SSL_ERROR_WANT_WRITE 3

// SSL_ERROR_WANT_X509_LOOKUP indicates the operation failed in calling the
// `cert_cb` or `client_cert_cb`. The caller may retry the operation when the
// callback is ready to return a certificate or one has been configured
// externally.
//
// See also `SSL_CTX_set_cert_cb` and `SSL_CTX_set_client_cert_cb`.
#define SSL_ERROR_WANT_X509_LOOKUP 4

// SSL_ERROR_SYSCALL indicates the operation failed externally to the library.
// The caller should consult the system-specific error mechanism. This is
// typically `errno` but may be something custom if using a custom `BIO`. It
// may also be signaled if the transport returned EOF, in which case the
// operation's return value will be zero.
#define SSL_ERROR_SYSCALL 5

// SSL_ERROR_ZERO_RETURN indicates the operation failed because the connection
// was cleanly shut down with a close_notify alert.
#define SSL_ERROR_ZERO_RETURN 6

// SSL_ERROR_WANT_CONNECT indicates the operation failed attempting to connect
// the transport (the `BIO` signaled `BIO_RR_CONNECT`). The caller may retry the
// operation when the transport is ready.
#define SSL_ERROR_WANT_CONNECT 7

// SSL_ERROR_WANT_ACCEPT indicates the operation failed attempting to accept a
// connection from the transport (the `BIO` signaled `BIO_RR_ACCEPT`). The
// caller may retry the operation when the transport is ready.
//
// TODO(davidben): Remove this. It's used by accept BIOs which are bizarre.
#define SSL_ERROR_WANT_ACCEPT 8

// SSL_ERROR_WANT_CHANNEL_ID_LOOKUP is never used.
//
// TODO(davidben): Remove this. Some callers reference it when stringifying
// errors. They should use `SSL_error_description` instead.
#define SSL_ERROR_WANT_CHANNEL_ID_LOOKUP 9

// SSL_ERROR_PENDING_SESSION indicates the operation failed because the session
// lookup callback indicated the session was unavailable. The caller may retry
// the operation when lookup has completed.
//
// See also `SSL_CTX_sess_set_get_cb` and `SSL_magic_pending_session_ptr`.
#define SSL_ERROR_PENDING_SESSION 11

// SSL_ERROR_PENDING_CERTIFICATE indicates the operation failed because the
// early callback indicated certificate lookup was incomplete. The caller may
// retry the operation when lookup has completed.
//
// See also `SSL_CTX_set_select_certificate_cb`.
#define SSL_ERROR_PENDING_CERTIFICATE 12

// SSL_ERROR_WANT_PRIVATE_KEY_OPERATION indicates the operation failed because
// a private key operation was unfinished. The caller may retry the operation
// when the private key operation is complete.
//
// See also `SSL_set_private_key_method`, `SSL_CTX_set_private_key_method`, and
// `SSL_CREDENTIAL_set_private_key_method`.
#define SSL_ERROR_WANT_PRIVATE_KEY_OPERATION 13

// SSL_ERROR_PENDING_TICKET indicates that a ticket decryption is pending. The
// caller may retry the operation when the decryption is ready.
//
// See also `SSL_CTX_set_ticket_aead_method`.
#define SSL_ERROR_PENDING_TICKET 14

// SSL_ERROR_EARLY_DATA_REJECTED indicates that early data was rejected. The
// caller should treat this as a connection failure and retry any operations
// associated with the rejected early data. `SSL_reset_early_data_reject` may be
// used to reuse the underlying connection for the retry.
#define SSL_ERROR_EARLY_DATA_REJECTED 15

// SSL_ERROR_WANT_CERTIFICATE_VERIFY indicates the operation failed because
// certificate verification was incomplete. The caller may retry the operation
// when certificate verification is complete.
//
// See also `SSL_CTX_set_custom_verify`.
#define SSL_ERROR_WANT_CERTIFICATE_VERIFY 16

// SSL_ERROR_WANT_RENEGOTIATE indicates the operation is pending a response to
// a renegotiation request from the server. The caller may call
// `SSL_renegotiate` to schedule a renegotiation and retry the operation.
//
// See also `ssl_renegotiate_explicit`.
#define SSL_ERROR_WANT_RENEGOTIATE 19

// SSL_ERROR_HANDSHAKE_HINTS_READY indicates the handshake has progressed enough
// for `SSL_serialize_handshake_hints` to be called. See also
// `SSL_request_handshake_hints`.
#define SSL_ERROR_HANDSHAKE_HINTS_READY 20

// SSL_error_description returns a string representation of `err`, where `err`
// is one of the `SSL_ERROR_*` constants returned by `SSL_get_error`, or NULL
// if the value is unrecognized.
OPENSSL_EXPORT const char *SSL_error_description(int err);

// SSL_set_mtu sets the `ssl`'s MTU in DTLS to `mtu`. It returns one on success
// and zero on failure.
OPENSSL_EXPORT int SSL_set_mtu(SSL *ssl, unsigned mtu);

// DTLSv1_set_initial_timeout_duration sets the initial duration for a DTLS
// handshake timeout.
//
// This duration overrides the default of 400 milliseconds, which is
// recommendation of RFC 9147 for real-time protocols.
//
// If `ssl` is an open connection, this function may update currently running
// timers and may make them expire. Callers should call
// `DTLSv1_get_timeout` for an updated timeout and reschedule accordingly.
OPENSSL_EXPORT void DTLSv1_set_initial_timeout_duration(SSL *ssl,
                                                        uint32_t duration_ms);

// DTLSv1_get_timeout queries the running DTLS timers. If there are any in
// progress, it sets `*out` to the time remaining until the first timer expires
// and returns one. Otherwise, it returns zero. Timers may be scheduled both
// during and after the handshake.
//
// When the timeout expires, call `DTLSv1_handle_timeout` to handle the
// retransmit behavior.
//
// NOTE: This function must be queried again whenever the state machine changes,
// including when `DTLSv1_handle_timeout` is called.
OPENSSL_EXPORT int DTLSv1_get_timeout(const SSL *ssl, struct timeval *out);

// DTLSv1_handle_timeout is called when a DTLS timeout expires. If no timeout
// had expired, it returns 0. Otherwise, it handles the timeout and returns 1 on
// success or -1 on error.
//
// This function may write to the transport (e.g. to retransmit messages) or
// update `ssl`'s internal state and schedule an updated timer.
//
// The caller's external timer should be compatible with the one `ssl` queries
// within some fudge factor. Otherwise, the call will be a no-op, but
// `DTLSv1_get_timeout` will return an updated timeout.
//
// If the function returns -1, checking if `SSL_get_error` returns
// `SSL_ERROR_WANT_WRITE` may be used to determine if the retransmit failed due
// to a non-fatal error at the write `BIO`. In this case, when the `BIO` is
// writable, the operation may be retried by calling the original function,
// `SSL_do_handshake` or `SSL_read`.
//
// WARNING: This function breaks the usual return value convention.
//
// TODO(davidben): We can make this function entirely optional by just checking
// the timers in `SSL_do_handshake` or `SSL_read`. Then timers behave like any
// other retry condition: rerun the operation and the library will make what
// progress it can.
OPENSSL_EXPORT int DTLSv1_handle_timeout(SSL *ssl);


// Protocol versions.

#define DTLS1_VERSION_MAJOR 0xfe
#define SSL3_VERSION_MAJOR 0x03

#define SSL3_VERSION 0x0300
#define TLS1_VERSION 0x0301
#define TLS1_1_VERSION 0x0302
#define TLS1_2_VERSION 0x0303
#define TLS1_3_VERSION 0x0304

#define DTLS1_VERSION 0xfeff
#define DTLS1_2_VERSION 0xfefd
#define DTLS1_3_VERSION 0xfefc

// SSL_CTX_set_min_proto_version sets the minimum protocol version for `ctx` to
// `version`. If `version` is zero, the default minimum version is used. It
// returns one on success and zero if `version` is invalid.
OPENSSL_EXPORT int SSL_CTX_set_min_proto_version(SSL_CTX *ctx,
                                                 uint16_t version);

// SSL_CTX_set_max_proto_version sets the maximum protocol version for `ctx` to
// `version`. If `version` is zero, the default maximum version is used. It
// returns one on success and zero if `version` is invalid.
OPENSSL_EXPORT int SSL_CTX_set_max_proto_version(SSL_CTX *ctx,
                                                 uint16_t version);

// SSL_CTX_get_min_proto_version returns the minimum protocol version for `ctx`
OPENSSL_EXPORT uint16_t SSL_CTX_get_min_proto_version(const SSL_CTX *ctx);

// SSL_CTX_get_max_proto_version returns the maximum protocol version for `ctx`
OPENSSL_EXPORT uint16_t SSL_CTX_get_max_proto_version(const SSL_CTX *ctx);

// SSL_set_min_proto_version sets the minimum protocol version for `ssl` to
// `version`. If `version` is zero, the default minimum version is used. It
// returns one on success and zero if `version` is invalid.
OPENSSL_EXPORT int SSL_set_min_proto_version(SSL *ssl, uint16_t version);

// SSL_set_max_proto_version sets the maximum protocol version for `ssl` to
// `version`. If `version` is zero, the default maximum version is used. It
// returns one on success and zero if `version` is invalid.
OPENSSL_EXPORT int SSL_set_max_proto_version(SSL *ssl, uint16_t version);

// SSL_get_min_proto_version returns the minimum protocol version for `ssl`. If
// the connection's configuration has been shed, 0 is returned.
OPENSSL_EXPORT uint16_t SSL_get_min_proto_version(const SSL *ssl);

// SSL_get_max_proto_version returns the maximum protocol version for `ssl`. If
// the connection's configuration has been shed, 0 is returned.
OPENSSL_EXPORT uint16_t SSL_get_max_proto_version(const SSL *ssl);

// SSL_version returns the TLS or DTLS protocol version used by `ssl`, which is
// one of the `*_VERSION` values. (E.g. `TLS1_2_VERSION`.) Before the version
// is negotiated, the result is undefined.
OPENSSL_EXPORT int SSL_version(const SSL *ssl);


// Options.
//
// Options configure protocol behavior.

// SSL_OP_LEGACY_SERVER_CONNECT configures a client to permit connecting to
// legacy servers that do not implement renegotiation_info (RFC 5746). If
// disabled, connections to such servers will fail. This option is enabled by
// default, but may be disabled with `SSL_CTX_clear_options`.
#define SSL_OP_LEGACY_SERVER_CONNECT 0x00000004L

// SSL_OP_NO_QUERY_MTU, in DTLS, disables querying the MTU from the underlying
// `BIO`. Instead, the MTU is configured with `SSL_set_mtu`.
#define SSL_OP_NO_QUERY_MTU 0x00001000L

// SSL_OP_NO_TICKET disables session ticket support (RFC 5077).
#define SSL_OP_NO_TICKET 0x00004000L

// SSL_OP_CIPHER_SERVER_PREFERENCE configures servers to select ciphers and
// ECDHE curves according to the server's preferences instead of the
// client's.
#define SSL_OP_CIPHER_SERVER_PREFERENCE 0x00400000L

// SSL_OP_ALL is the set of options that are enabled by default. It is safe, but
// not necessary, to pass this value to `SSL_CTX_set_options`.
// TODO(crbug.com/41393419): Disable SSL_OP_LEGACY_SERVER_CONNECT by default.
#define SSL_OP_ALL SSL_OP_LEGACY_SERVER_CONNECT

// The following flags toggle individual protocol versions. This is deprecated.
// Use `SSL_CTX_set_min_proto_version` and `SSL_CTX_set_max_proto_version`
// instead.
#define SSL_OP_NO_TLSv1 0x04000000L
#define SSL_OP_NO_TLSv1_2 0x08000000L
#define SSL_OP_NO_TLSv1_1 0x10000000L
#define SSL_OP_NO_TLSv1_3 0x20000000L
#define SSL_OP_NO_DTLSv1 SSL_OP_NO_TLSv1
#define SSL_OP_NO_DTLSv1_2 SSL_OP_NO_TLSv1_2

// SSL_CTX_set_options enables all options set in `options` (which should be one
// or more of the `SSL_OP_*` values, ORed together) in `ctx`. It returns a
// bitmask representing the resulting enabled options.
OPENSSL_EXPORT uint32_t SSL_CTX_set_options(SSL_CTX *ctx, uint32_t options);

// SSL_CTX_clear_options disables all options set in `options` (which should be
// one or more of the `SSL_OP_*` values, ORed together) in `ctx`. It returns a
// bitmask representing the resulting enabled options.
OPENSSL_EXPORT uint32_t SSL_CTX_clear_options(SSL_CTX *ctx, uint32_t options);

// SSL_CTX_get_options returns a bitmask of `SSL_OP_*` values that represent all
// the options enabled for `ctx`.
OPENSSL_EXPORT uint32_t SSL_CTX_get_options(const SSL_CTX *ctx);

// SSL_set_options enables all options set in `options` (which should be one or
// more of the `SSL_OP_*` values, ORed together) in `ssl`. It returns a bitmask
// representing the resulting enabled options.
OPENSSL_EXPORT uint32_t SSL_set_options(SSL *ssl, uint32_t options);

// SSL_clear_options disables all options set in `options` (which should be one
// or more of the `SSL_OP_*` values, ORed together) in `ssl`. It returns a
// bitmask representing the resulting enabled options.
OPENSSL_EXPORT uint32_t SSL_clear_options(SSL *ssl, uint32_t options);

// SSL_get_options returns a bitmask of `SSL_OP_*` values that represent all the
// options enabled for `ssl`.
OPENSSL_EXPORT uint32_t SSL_get_options(const SSL *ssl);


// Modes.
//
// Modes configure API behavior.

// SSL_MODE_ENABLE_PARTIAL_WRITE, in TLS, allows `SSL_write` to complete with a
// partial result when the only part of the input was written in a single
// record. In DTLS, it does nothing.
#define SSL_MODE_ENABLE_PARTIAL_WRITE 0x00000001L

// SSL_MODE_ACCEPT_MOVING_WRITE_BUFFER, in TLS, allows retrying an incomplete
// `SSL_write` with a different buffer. However, `SSL_write` still assumes the
// buffer contents are unchanged. This is not the default to avoid the
// misconception that non-blocking `SSL_write` behaves like non-blocking
// `write`. In DTLS, it does nothing.
#define SSL_MODE_ACCEPT_MOVING_WRITE_BUFFER 0x00000002L

// SSL_MODE_NO_AUTO_CHAIN disables automatically building a certificate chain
// before sending certificates to the peer. This flag is set (and the feature
// disabled) by default.
// TODO(davidben): Remove this behavior. https://crbug.com/boringssl/42.
#define SSL_MODE_NO_AUTO_CHAIN 0x00000008L

// SSL_MODE_ENABLE_FALSE_START allows clients to send application data before
// receipt of ChangeCipherSpec and Finished. This mode enables full handshakes
// to 'complete' in one RTT. See RFC 7918.
//
// When False Start is enabled, `SSL_do_handshake` may succeed before the
// handshake has completely finished. `SSL_write` will function at this point,
// and `SSL_read` will transparently wait for the final handshake leg before
// returning application data. To determine if False Start occurred or when the
// handshake is completely finished, see `SSL_in_false_start`, `SSL_in_init`,
// and `SSL_CB_HANDSHAKE_DONE` from `SSL_CTX_set_info_callback`.
#define SSL_MODE_ENABLE_FALSE_START 0x00000080L

// SSL_MODE_CBC_RECORD_SPLITTING causes multi-byte CBC records in TLS 1.0 to be
// split in two: the first record will contain a single byte and the second will
// contain the remainder. This effectively randomises the IV and prevents BEAST
// attacks.
#define SSL_MODE_CBC_RECORD_SPLITTING 0x00000100L

// SSL_MODE_NO_SESSION_CREATION will cause any attempts to create a session to
// fail with SSL_R_SESSION_MAY_NOT_BE_CREATED. This can be used to enforce that
// session resumption is used for a given SSL*.
#define SSL_MODE_NO_SESSION_CREATION 0x00000200L

// SSL_MODE_SEND_FALLBACK_SCSV sends TLS_FALLBACK_SCSV in the ClientHello.
// To be set only by applications that reconnect with a downgraded protocol
// version; see RFC 7507 for details.
//
// DO NOT ENABLE THIS if your application attempts a normal handshake. Only use
// this in explicit fallback retries, following the guidance in RFC 7507.
#define SSL_MODE_SEND_FALLBACK_SCSV 0x00000400L

// SSL_CTX_set_mode enables all modes set in `mode` (which should be one or more
// of the `SSL_MODE_*` values, ORed together) in `ctx`. It returns a bitmask
// representing the resulting enabled modes.
OPENSSL_EXPORT uint32_t SSL_CTX_set_mode(SSL_CTX *ctx, uint32_t mode);

// SSL_CTX_clear_mode disables all modes set in `mode` (which should be one or
// more of the `SSL_MODE_*` values, ORed together) in `ctx`. It returns a
// bitmask representing the resulting enabled modes.
OPENSSL_EXPORT uint32_t SSL_CTX_clear_mode(SSL_CTX *ctx, uint32_t mode);

// SSL_CTX_get_mode returns a bitmask of `SSL_MODE_*` values that represent all
// the modes enabled for `ssl`.
OPENSSL_EXPORT uint32_t SSL_CTX_get_mode(const SSL_CTX *ctx);

// SSL_set_mode enables all modes set in `mode` (which should be one or more of
// the `SSL_MODE_*` values, ORed together) in `ssl`. It returns a bitmask
// representing the resulting enabled modes.
OPENSSL_EXPORT uint32_t SSL_set_mode(SSL *ssl, uint32_t mode);

// SSL_clear_mode disables all modes set in `mode` (which should be one or more
// of the `SSL_MODE_*` values, ORed together) in `ssl`. It returns a bitmask
// representing the resulting enabled modes.
OPENSSL_EXPORT uint32_t SSL_clear_mode(SSL *ssl, uint32_t mode);

// SSL_get_mode returns a bitmask of `SSL_MODE_*` values that represent all the
// modes enabled for `ssl`.
OPENSSL_EXPORT uint32_t SSL_get_mode(const SSL *ssl);

// SSL_CTX_set1_buffer_pool sets a `CRYPTO_BUFFER_POOL` that will be used to
// store certificates. This can allow multiple connections to share
// certificates and thus save memory.
OPENSSL_EXPORT void SSL_CTX_set1_buffer_pool(SSL_CTX *ctx,
                                             CRYPTO_BUFFER_POOL *pool);


// Credentials.
//
// TLS endpoints may present authentication during the handshake, usually using
// X.509 certificates. This is typically required for servers and optional for
// clients. BoringSSL uses the `SSL_CREDENTIAL` object to abstract between
// different kinds of credentials, as well as configure automatic selection
// between multiple credentials. This may be used to select between ECDSA and
// RSA certificates.
//
// `SSL_CTX` and `SSL` objects maintain lists of credentials in preference
// order. During the handshake, BoringSSL will select the first usable
// credential from the list. Non-credential APIs, such as
// `SSL_CTX_use_certificate`, configure a "legacy credential", which is
// appended to this list if configured. Using the legacy credential is the same
// as configuring an equivalent credential with the `SSL_CREDENTIAL` API.
//
// When selecting credentials, BoringSSL considers the credential's type, its
// cryptographic capabilities, and capabilities advertised by the peer. This
// varies between TLS versions but includes:
//
// - Whether the peer supports the leaf certificate key
// - Whether there is a common signature algorithm that is compatible with the
//   credential
// - Whether there is a common cipher suite that is compatible with the
//   credential
//
// WARNING: In TLS 1.2 and below, there is no mechanism for servers to advertise
// supported ECDSA curves to the client. BoringSSL clients will assume the
// server accepts all ECDSA curves in client certificates.
//
// By default, BoringSSL does not check the following, though we may add APIs
// in the future to enable them on a per-credential basis.
//
// - Whether the peer supports the signature algorithms in the certificate chain
// - Whether the a server certificate is compatible with the server_name
//   extension (SNI)
//
// Credentials may be configured before the handshake or dynamically in the
// early callback (see `SSL_CTX_set_select_certificate_cb`) and certificate
// callback (see `SSL_CTX_set_cert_cb`). These callbacks allow applications to
// use BoringSSL's built-in selection logic in tandem with custom logic. For
// example, a callback could evaluate application-specific SNI rules to filter
// down to an ECDSA and RSA credential, then configure both for BoringSSL to
// select between the two.
//
// On the server, the credential is selected before resumption. By default,
// sessions established when using one credential can be resumed on other
// credentials. Callers can partition sessions with
// `SSL_CREDENTIAL_set1_session_id_context`.

// SSL_CREDENTIAL_new_x509 returns a new, empty X.509 credential, or NULL on
// error. Callers should release the result with `SSL_CREDENTIAL_free` when
// done.
//
// Callers should configure a certificate chain and private key on the
// credential, along with other properties, then add it with
// `SSL_CTX_add1_credential`.
OPENSSL_EXPORT SSL_CREDENTIAL *SSL_CREDENTIAL_new_x509(void);

// SSL_CREDENTIAL_up_ref increments the reference count of `cred`.
OPENSSL_EXPORT void SSL_CREDENTIAL_up_ref(SSL_CREDENTIAL *cred);

// SSL_CREDENTIAL_dup_ref increments the reference count of `cred` and returns
// `cred`. The caller must call `SSL_CREDENTIAL_free` on the result to release
// the reference.
//
// WARNING: Although the result is non-const for use with `SSL_CREDENTIAL_free`,
// it is still shared with other parts of the application that share the same
// object. Avoid mutating shared `SSL_CREDENTIAL`s.
OPENSSL_EXPORT SSL_CREDENTIAL *SSL_CREDENTIAL_dup_ref(
    const SSL_CREDENTIAL *cred);

// SSL_CREDENTIAL_free decrements the reference count of `cred`. If it reaches
// zero, all data referenced by `cred` and `cred` itself are released.
OPENSSL_EXPORT void SSL_CREDENTIAL_free(SSL_CREDENTIAL *cred);

// SSL_CREDENTIAL_is_complete returns one if the returns one if `cred` has all
// required properties configured, and zero otherwise.
//
// This includes checks on whether the public key is present in a X.509
// credential and whether a private key or private key method has been set up
// for such.
OPENSSL_EXPORT int SSL_CREDENTIAL_is_complete(const SSL_CREDENTIAL *cred);

// SSL_CREDENTIAL_set1_private_key sets `cred`'s private key to `cred`. It
// returns one on success and zero on failure.
OPENSSL_EXPORT int SSL_CREDENTIAL_set1_private_key(SSL_CREDENTIAL *cred,
                                                   EVP_PKEY *key);

// SSL_CREDENTIAL_set1_signing_algorithm_prefs configures `cred` to use `prefs`
// as the preference list when signing with `cred`'s private key. It returns one
// on success and zero on error. `prefs` should not include the internal-only
// value `SSL_SIGN_RSA_PKCS1_MD5_SHA1`.
//
// It is an error to call this function with delegated credentials (see
// `SSL_CREDENTIAL_new_delegated`) because delegated credentials already
// constrain the key to a single algorithm.
OPENSSL_EXPORT int SSL_CREDENTIAL_set1_signing_algorithm_prefs(
    SSL_CREDENTIAL *cred, const uint16_t *prefs, size_t num_prefs);

// SSL_CREDENTIAL_set1_cert_chain sets `cred`'s certificate chain, starting from
// the leaf, to `num_cert`s certificates from `certs`. It returns one on success
// and zero on error.
OPENSSL_EXPORT int SSL_CREDENTIAL_set1_cert_chain(SSL_CREDENTIAL *cred,
                                                  CRYPTO_BUFFER *const *certs,
                                                  size_t num_certs);

// SSL_CREDENTIAL_set1_ocsp_response sets `cred`'s stapled OCSP response to
// `ocsp`. It returns one on success and zero on error.
OPENSSL_EXPORT int SSL_CREDENTIAL_set1_ocsp_response(SSL_CREDENTIAL *cred,
                                                     CRYPTO_BUFFER *ocsp);

// SSL_CREDENTIAL_set1_certificate_properties parses
// `certificate_property_list` as a CertificatePropertyList (see Section 7 of
// draft-ietf-tls-trust-anchor-ids-06) and applies recognized properties to
// `cred`. It returns one on success and zero on error. It is an error if
// `certificate_property_list` does not parse correctly, or if any recognized
// properties from `certificate_property_list` cannot be applied to `cred`.
//
// CertificatePropertyList is an extensible structure which allows serving
// properties of a certificate chain to be passed from a CA, through an
// application's issuance and configuration pipeline, and to the TLS serving
// logic, without requiring application changes for each property defined.
//
// BoringSSL currently supports the following properties:
// * trust_anchor_id (see `SSL_CREDENTIAL_set1_trust_anchor_id`)
// * trust_anchor_groups (see `SSL_CREDENTIAL_add1_trust_anchor_group`)
//
// Note this function does not automatically enable issuer matching. Callers
// must separately call `SSL_CREDENTIAL_set_must_match_issuer` if desired.
OPENSSL_EXPORT int SSL_CREDENTIAL_set1_certificate_properties(
    SSL_CREDENTIAL *cred, CRYPTO_BUFFER *cert_property_list);

// SSL_CREDENTIAL_set1_signed_cert_timestamp_list sets `cred`'s list of signed
// certificate timestamps `sct_list`. `sct_list` must contain one or more SCT
// structures serialised as a SignedCertificateTimestampList (see
// https://tools.ietf.org/html/rfc6962#section-3.3) – i.e. each SCT is prefixed
// by a big-endian, uint16 length and the concatenation of one or more such
// prefixed SCTs are themselves also prefixed by a uint16 length. It returns one
// on success and zero on error.
OPENSSL_EXPORT int SSL_CREDENTIAL_set1_signed_cert_timestamp_list(
    SSL_CREDENTIAL *cred, CRYPTO_BUFFER *sct_list);

// SSL_CREDENTIAL_set_must_match_issuer configures whether `cred` should check
// if the peer supports the certificate chain's issuer.
//
// If `match` is non-zero, `cred` will only be applicable when the certificate
// chain is issued by some CA requested by the peer in the
// certificate_authorities extension or, if `cred` has a trust anchor ID (see
// `SSL_CREDENTIAL_set1_trust_anchor_id`), the trust_anchors extension. `cred`'s
// certificate chain must then be a correctly ordered certification path.
//
// If `match` is zero (default), `cred` will not be conditioned on the peer's
// requested CAs. This can be used for certificate chains that are assumed to be
// usable by most peers.
//
// This setting can be used for certificate chains that may not be usable by all
// peers, e.g. chains with fewer cross-signs or issued from a newer CA. The
// credential list is tried in order, so more specific credentials that enable
// issuer matching should generally be ordered before less specific credentials
// that do not.
OPENSSL_EXPORT void SSL_CREDENTIAL_set_must_match_issuer(SSL_CREDENTIAL *cred,
                                                         int match);

// SSL_CREDENTIAL_set1_session_id_context sets `cred`'s session ID context to
// `sid_ctx`. It returns one on success and zero on error. The session ID
// context is an application-defined opaque byte string used to partition
// session resumption. A session will not be used in a connection without a
// matching session ID context.
//
// If unset on a server credential, the session ID context configured on the
// `SSL` (or `SSL_CTX`) will be used. See `SSL_CTX_set_session_id_context`.
//
// This setting is only applicable to server credentials.
OPENSSL_EXPORT int SSL_CREDENTIAL_set1_session_id_context(
    SSL_CREDENTIAL *cred, const uint8_t *sid_ctx, size_t sid_ctx_len);

// SSL_CTX_add1_credential appends `cred` to `ctx`'s credential list. It returns
// one on success and zero on error. The credential list is maintained in order
// of decreasing preference, so earlier calls are preferred over later calls.
//
// After calling this function, it is an error to modify `cred`. Doing so may
// result in inconsistent handshake behavior or race conditions.
OPENSSL_EXPORT int SSL_CTX_add1_credential(SSL_CTX *ctx,
                                           const SSL_CREDENTIAL *cred);

// SSL_add1_credential appends `cred` to `ssl`'s credential list. It returns one
// on success and zero on error. The credential list is maintained in order of
// decreasing preference, so earlier calls are preferred over later calls.
//
// After calling this function, it is an error to modify `cred`. Doing so may
// result in inconsistent handshake behavior or race conditions.
OPENSSL_EXPORT int SSL_add1_credential(SSL *ssl, const SSL_CREDENTIAL *cred);

// SSL_certs_clear removes all credentials configured on `ssl`. It also removes
// the certificate chain and private key on the legacy credential.
OPENSSL_EXPORT void SSL_certs_clear(SSL *ssl);

// SSL_get0_selected_credential returns the credential in use in the current
// handshake on `ssl`. If there is current handshake on `ssl` or if the
// handshake has not progressed to this point, it returns NULL.
//
// This function is intended for use with `SSL_CREDENTIAL_get_ex_data`. It may
// be called from handshake callbacks, such as those in
// `SSL_PRIVATE_KEY_METHOD`, to trigger credential-specific behavior.
//
// In applications that use the older APIs, such as `SSL_use_certificate`, this
// function may return an internal `SSL_CREDENTIAL` object. This internal object
// will have no ex_data installed. To avoid this, it is recommended that callers
// moving to `SSL_CREDENTIAL` use the new APIs consistently.
OPENSSL_EXPORT const SSL_CREDENTIAL *SSL_get0_selected_credential(
    const SSL *ssl);


// Configuring certificates and private keys.
//
// These functions configure the connection's leaf certificate, private key, and
// certificate chain. The certificate chain is ordered leaf to root (as sent on
// the wire) but does not include the leaf. Both client and server certificates
// use these functions.
//
// Prefer to configure the certificate before the private key. If configured in
// the other order, inconsistent private keys will be silently dropped, rather
// than return an error. Additionally, overwriting a previously-configured
// certificate and key pair only works if the certificate is configured first.
//
// Each of these functions configures the single "legacy credential" on the
// `SSL_CTX` or `SSL`. To select between multiple certificates, use
// `SSL_CREDENTIAL_new_x509` and other APIs to configure a list of credentials.

// SSL_CTX_use_certificate sets `ctx`'s leaf certificate to `x509`. It returns
// one on success and zero on failure. If `ctx` has a private key which is
// inconsistent with `x509`, the private key is silently dropped.
OPENSSL_EXPORT int SSL_CTX_use_certificate(SSL_CTX *ctx, X509 *x509);

// SSL_use_certificate sets `ssl`'s leaf certificate to `x509`. It returns one
// on success and zero on failure. If `ssl` has a private key which is
// inconsistent with `x509`, the private key is silently dropped.
OPENSSL_EXPORT int SSL_use_certificate(SSL *ssl, X509 *x509);

// SSL_CTX_use_PrivateKey sets `ctx`'s private key to `pkey`. It returns one on
// success and zero on failure. If `ctx` had a private key or
// `SSL_PRIVATE_KEY_METHOD` previously configured, it is replaced.
OPENSSL_EXPORT int SSL_CTX_use_PrivateKey(SSL_CTX *ctx, EVP_PKEY *pkey);

// SSL_use_PrivateKey sets `ssl`'s private key to `pkey`. It returns one on
// success and zero on failure. If `ssl` had a private key or
// `SSL_PRIVATE_KEY_METHOD` previously configured, it is replaced.
OPENSSL_EXPORT int SSL_use_PrivateKey(SSL *ssl, EVP_PKEY *pkey);

// SSL_CTX_set0_chain sets `ctx`'s certificate chain, excluding the leaf, to
// `chain`. On success, it returns one and takes ownership of `chain`.
// Otherwise, it returns zero.
OPENSSL_EXPORT int SSL_CTX_set0_chain(SSL_CTX *ctx, STACK_OF(X509) *chain);

// SSL_CTX_set1_chain sets `ctx`'s certificate chain, excluding the leaf, to
// `chain`. It returns one on success and zero on failure. The caller retains
// ownership of `chain` and may release it freely.
OPENSSL_EXPORT int SSL_CTX_set1_chain(SSL_CTX *ctx, STACK_OF(X509) *chain);

// SSL_set0_chain sets `ssl`'s certificate chain, excluding the leaf, to
// `chain`. On success, it returns one and takes ownership of `chain`.
// Otherwise, it returns zero.
OPENSSL_EXPORT int SSL_set0_chain(SSL *ssl, STACK_OF(X509) *chain);

// SSL_set1_chain sets `ssl`'s certificate chain, excluding the leaf, to
// `chain`. It returns one on success and zero on failure. The caller retains
// ownership of `chain` and may release it freely.
OPENSSL_EXPORT int SSL_set1_chain(SSL *ssl, STACK_OF(X509) *chain);

// SSL_CTX_add0_chain_cert appends `x509` to `ctx`'s certificate chain. On
// success, it returns one and takes ownership of `x509`. Otherwise, it returns
// zero.
OPENSSL_EXPORT int SSL_CTX_add0_chain_cert(SSL_CTX *ctx, X509 *x509);

// SSL_CTX_add1_chain_cert appends `x509` to `ctx`'s certificate chain. It
// returns one on success and zero on failure. The caller retains ownership of
// `x509` and may release it freely.
OPENSSL_EXPORT int SSL_CTX_add1_chain_cert(SSL_CTX *ctx, X509 *x509);

// SSL_add0_chain_cert appends `x509` to `ctx`'s certificate chain. On success,
// it returns one and takes ownership of `x509`. Otherwise, it returns zero.
OPENSSL_EXPORT int SSL_add0_chain_cert(SSL *ssl, X509 *x509);

// SSL_CTX_add_extra_chain_cert calls `SSL_CTX_add0_chain_cert`.
OPENSSL_EXPORT int SSL_CTX_add_extra_chain_cert(SSL_CTX *ctx, X509 *x509);

// SSL_add1_chain_cert appends `x509` to `ctx`'s certificate chain. It returns
// one on success and zero on failure. The caller retains ownership of `x509`
// and may release it freely.
OPENSSL_EXPORT int SSL_add1_chain_cert(SSL *ssl, X509 *x509);

// SSL_CTX_clear_chain_certs clears `ctx`'s certificate chain and returns
// one.
OPENSSL_EXPORT int SSL_CTX_clear_chain_certs(SSL_CTX *ctx);

// SSL_CTX_clear_extra_chain_certs calls `SSL_CTX_clear_chain_certs`.
OPENSSL_EXPORT int SSL_CTX_clear_extra_chain_certs(SSL_CTX *ctx);

// SSL_clear_chain_certs clears `ssl`'s certificate chain and returns one.
OPENSSL_EXPORT int SSL_clear_chain_certs(SSL *ssl);

// SSL_CTX_set_cert_cb sets a callback that is called to select a certificate.
// The callback returns one on success, zero on internal error, and a negative
// number on failure or to pause the handshake. If the handshake is paused,
// `SSL_get_error` will return `SSL_ERROR_WANT_X509_LOOKUP`.
//
// On the client, the callback may call `SSL_get0_certificate_types` and
// `SSL_get_client_CA_list` for information on the server's certificate
// request.
//
// On the server, the callback will be called after extensions have been
// processed, but before the resumption decision has been made. This differs
// from OpenSSL which handles resumption before selecting the certificate.
OPENSSL_EXPORT void SSL_CTX_set_cert_cb(SSL_CTX *ctx,
                                        int (*cb)(SSL *ssl, void *arg),
                                        void *arg);

// SSL_CTX_set_cert_cb_ex sets a callback that is called to select a certificate
// like `SSL_CTX_set_cert_cb` with an additional argument to allow the callback
// to select the fatal alert to send.
// If `cb` returns zero, it should set `*out_alert` to one of `SSL_AD_*` to
// specify the alert. If unset, it defaults to `SSL_AD_INTERNAL_ERROR`.
// `SSL_AD_HANDSHAKE_FAILURE` is an appropriate alert if the caller and peer do
// not have parameters in common.
OPENSSL_EXPORT void SSL_CTX_set_cert_cb_ex(SSL_CTX *ctx,
                                           int (*cb)(SSL *ssl, void *arg,
                                                     uint8_t *out_alert),
                                           void *arg);

// SSL_set_cert_cb sets a callback that is called to select a certificate. The
// callback returns one on success, zero on internal error, and a negative
// number on failure or to pause the handshake. If the handshake is paused,
// `SSL_get_error` will return `SSL_ERROR_WANT_X509_LOOKUP`.
//
// On the client, the callback may call `SSL_get0_certificate_types` and
// `SSL_get_client_CA_list` for information on the server's certificate
// request.
//
// On the server, the callback will be called after extensions have been
// processed, but before the resumption decision has been made. This differs
// from OpenSSL which handles resumption before selecting the certificate.
OPENSSL_EXPORT void SSL_set_cert_cb(SSL *ssl, int (*cb)(SSL *ssl, void *arg),
                                    void *arg);

// SSL_set_cert_cb_ex sets a callback that is called to select a certificate
// like `SSL_CTX_set_cert_cb` with an additional argument to allow the callback
// to select the fatal alert to send.
// If `cb` returns zero, it should set `*out_alert` to one of `SSL_AD_*` to
// specify the alert. If unset, it defaults to `SSL_AD_INTERNAL_ERROR`.
// `SSL_AD_HANDSHAKE_FAILURE` is an appropriate alert if the caller and peer do
// not have parameters in common.
OPENSSL_EXPORT void SSL_set_cert_cb_ex(
    SSL *ssl, int (*cb)(SSL *ssl, void *arg, uint8_t *out_alert), void *arg);

// SSL_get0_certificate_types, for a client, sets `*out_types` to an array
// containing the client certificate types requested by a server. It returns the
// length of the array. Note this list is always empty in TLS 1.3. The server
// will instead send signature algorithms. See
// `SSL_get0_peer_verify_algorithms`.
//
// The behavior of this function is undefined except during the callbacks set by
// by `SSL_CTX_set_cert_cb` and `SSL_CTX_set_client_cert_cb` or when the
// handshake is paused because of them.
OPENSSL_EXPORT size_t SSL_get0_certificate_types(const SSL *ssl,
                                                 const uint8_t **out_types);

// SSL_get0_peer_verify_algorithms sets `*out_sigalgs` to an array containing
// the signature algorithms the peer is able to verify. It returns the length of
// the array. Note these values are only sent starting TLS 1.2 and only
// mandatory starting TLS 1.3. If not sent, the empty array is returned. For the
// historical client certificate types list, see `SSL_get0_certificate_types`.
//
// The behavior of this function is undefined except during the callbacks set by
// by `SSL_CTX_set_cert_cb` and `SSL_CTX_set_client_cert_cb` or when the
// handshake is paused because of them.
OPENSSL_EXPORT size_t
SSL_get0_peer_verify_algorithms(const SSL *ssl, const uint16_t **out_sigalgs);

// SSL_get0_peer_delegation_algorithms sets `*out_sigalgs` to an array
// containing the signature algorithms the peer is willing to use with delegated
// credentials.  It returns the length of the array. If not sent, the empty
// array is returned.
//
// The behavior of this function is undefined except during the callbacks set by
// by `SSL_CTX_set_cert_cb` and `SSL_CTX_set_client_cert_cb` or when the
// handshake is paused because of them.
OPENSSL_EXPORT size_t SSL_get0_peer_delegation_algorithms(
    const SSL *ssl, const uint16_t **out_sigalgs);

// SSL_CTX_get0_certificate returns `ctx`'s leaf certificate.
OPENSSL_EXPORT X509 *SSL_CTX_get0_certificate(const SSL_CTX *ctx);

// SSL_get_certificate returns `ssl`'s leaf certificate.
OPENSSL_EXPORT X509 *SSL_get_certificate(const SSL *ssl);

// SSL_CTX_get0_privatekey returns `ctx`'s private key.
OPENSSL_EXPORT EVP_PKEY *SSL_CTX_get0_privatekey(const SSL_CTX *ctx);

// SSL_get_privatekey returns `ssl`'s private key.
OPENSSL_EXPORT EVP_PKEY *SSL_get_privatekey(const SSL *ssl);

// SSL_CTX_get0_chain_certs sets `*out_chain` to `ctx`'s certificate chain and
// returns one.
OPENSSL_EXPORT int SSL_CTX_get0_chain_certs(const SSL_CTX *ctx,
                                            STACK_OF(X509) **out_chain);

// SSL_CTX_get_extra_chain_certs calls `SSL_CTX_get0_chain_certs`.
OPENSSL_EXPORT int SSL_CTX_get_extra_chain_certs(const SSL_CTX *ctx,
                                                 STACK_OF(X509) **out_chain);

// SSL_get0_chain_certs sets `*out_chain` to `ssl`'s certificate chain and
// returns one.
OPENSSL_EXPORT int SSL_get0_chain_certs(const SSL *ssl,
                                        STACK_OF(X509) **out_chain);

// SSL_CTX_set_signed_cert_timestamp_list sets the list of signed certificate
// timestamps that is sent to clients that request it. The `list` argument must
// contain one or more SCT structures serialised as a SignedCertificateTimestamp
// List (see https://tools.ietf.org/html/rfc6962#section-3.3) – i.e. each SCT
// is prefixed by a big-endian, uint16 length and the concatenation of one or
// more such prefixed SCTs are themselves also prefixed by a uint16 length. It
// returns one on success and zero on error. The caller retains ownership of
// `list`.
OPENSSL_EXPORT int SSL_CTX_set_signed_cert_timestamp_list(SSL_CTX *ctx,
                                                          const uint8_t *list,
                                                          size_t list_len);

// SSL_set_signed_cert_timestamp_list sets the list of signed certificate
// timestamps that is sent to clients that request is. The same format as the
// one used for `SSL_CTX_set_signed_cert_timestamp_list` applies. The caller
// retains ownership of `list`.
OPENSSL_EXPORT int SSL_set_signed_cert_timestamp_list(SSL *ctx,
                                                      const uint8_t *list,
                                                      size_t list_len);

// SSL_CTX_set_ocsp_response sets the OCSP response that is sent to clients
// which request it. It returns one on success and zero on error. The caller
// retains ownership of `response`.
OPENSSL_EXPORT int SSL_CTX_set_ocsp_response(SSL_CTX *ctx,
                                             const uint8_t *response,
                                             size_t response_len);

// SSL_set_ocsp_response sets the OCSP response that is sent to clients which
// request it. It returns one on success and zero on error. The caller retains
// ownership of `response`.
OPENSSL_EXPORT int SSL_set_ocsp_response(SSL *ssl, const uint8_t *response,
                                         size_t response_len);

// SSL_SIGN_* are signature algorithm values as defined in TLS 1.3.
#define SSL_SIGN_RSA_PKCS1_SHA1 0x0201
#define SSL_SIGN_RSA_PKCS1_SHA256 0x0401
#define SSL_SIGN_RSA_PKCS1_SHA384 0x0501
#define SSL_SIGN_RSA_PKCS1_SHA512 0x0601
#define SSL_SIGN_ECDSA_SHA1 0x0203
#define SSL_SIGN_ECDSA_SECP256R1_SHA256 0x0403
#define SSL_SIGN_ECDSA_SECP384R1_SHA384 0x0503
#define SSL_SIGN_ECDSA_SECP521R1_SHA512 0x0603
#define SSL_SIGN_RSA_PSS_RSAE_SHA256 0x0804
#define SSL_SIGN_RSA_PSS_RSAE_SHA384 0x0805
#define SSL_SIGN_RSA_PSS_RSAE_SHA512 0x0806
#define SSL_SIGN_ED25519 0x0807
#define SSL_SIGN_ML_DSA_44 0x0904
#define SSL_SIGN_ML_DSA_65 0x0905
#define SSL_SIGN_ML_DSA_87 0x0906

// SSL_SIGN_RSA_PKCS1_SHA256_LEGACY is a backport of RSASSA-PKCS1-v1_5 with
// SHA-256 to TLS 1.3. It is disabled by default and only defined for client
// certificates.
#define SSL_SIGN_RSA_PKCS1_SHA256_LEGACY 0x0420

// SSL_SIGN_RSA_PKCS1_MD5_SHA1 is an internal signature algorithm used to
// specify raw RSASSA-PKCS1-v1_5 with an MD5/SHA-1 concatenation, as used in TLS
// before TLS 1.2.
#define SSL_SIGN_RSA_PKCS1_MD5_SHA1 0xff01

// SSL_get_signature_algorithm_name returns a human-readable name for `sigalg`,
// or NULL if unknown. If `include_curve` is one, the curve for ECDSA algorithms
// is included as in TLS 1.3. Otherwise, it is excluded as in TLS 1.2.
// This string is always an ASCII string.
OPENSSL_EXPORT const char *SSL_get_signature_algorithm_name(uint16_t sigalg,
                                                            int include_curve);

// SSL_get_all_signature_algorithm_names outputs a list of possible strings
// `SSL_get_signature_algorithm_name` may return in this version of BoringSSL.
// It writes at most `max_out` entries to `out` and returns the total number it
// would have written, if `max_out` had been large enough. `max_out` may be
// initially set to zero to size the output.
//
// This function is only intended to help initialize tables in callers that want
// possible strings pre-declared. This list would not be suitable to set a list
// of supported features. It is in no particular order, and may contain
// placeholder, experimental, or deprecated values that do not apply to every
// caller. Future versions of BoringSSL may also return strings not in this
// list, so this does not apply if, say, sending strings across services.
// The strings are always ASCII-encoded.
OPENSSL_EXPORT size_t SSL_get_all_signature_algorithm_names(const char **out,
                                                            size_t max_out);

// SSL_get_signature_algorithm_key_type returns the key type associated with
// `sigalg` as an `EVP_PKEY_*` constant or `EVP_PKEY_NONE` if unknown.
OPENSSL_EXPORT int SSL_get_signature_algorithm_key_type(uint16_t sigalg);

// SSL_get_signature_algorithm_digest returns the digest function associated
// with `sigalg` or `NULL` if `sigalg` has no prehash (Ed25519) or is unknown.
OPENSSL_EXPORT const EVP_MD *SSL_get_signature_algorithm_digest(
    uint16_t sigalg);

// SSL_is_signature_algorithm_rsa_pss returns one if `sigalg` is an RSA-PSS
// signature algorithm and zero otherwise.
OPENSSL_EXPORT int SSL_is_signature_algorithm_rsa_pss(uint16_t sigalg);

// SSL_CTX_set_signing_algorithm_prefs configures `ctx` to use `prefs` as the
// preference list when signing with `ctx`'s private key in TLS 1.2 and up. It
// returns one on success and zero on error. `prefs` should not include the
// internal-only TLS 1.0 value `SSL_SIGN_RSA_PKCS1_MD5_SHA1`.
//
// This setting is not used in TLS 1.0 and 1.1. Those protocols always sign a
// hardcoded algorithm (an MD5/SHA-1 concatenation for RSA, and SHA-1 for
// ECDSA). BoringSSL will use those algorithms if and only if those versions are
// used. To disable them, set the minimum version to TLS 1.2 (default) or
// higher.
OPENSSL_EXPORT int SSL_CTX_set_signing_algorithm_prefs(SSL_CTX *ctx,
                                                       const uint16_t *prefs,
                                                       size_t num_prefs);

// SSL_set_signing_algorithm_prefs configures `ssl` to use `prefs` as the
// preference list when signing with `ssl`'s private key in TLS 1.2 and up. It
// returns one on success and zero on error. `prefs` should not include the
// internal-only TLS 1.0 value `SSL_SIGN_RSA_PKCS1_MD5_SHA1`.
//
// This setting is not used in TLS 1.0 and 1.1. Those protocols always sign a
// hardcoded algorithm (an MD5/SHA-1 concatenation for RSA, and SHA-1 for
// ECDSA). BoringSSL will use those algorithms if and only if those versions are
// used. To disable them, set the minimum version to TLS 1.2 (default) or
// higher.
OPENSSL_EXPORT int SSL_set_signing_algorithm_prefs(SSL *ssl,
                                                   const uint16_t *prefs,
                                                   size_t num_prefs);


// Certificate and private key convenience functions.

// SSL_CTX_set_chain_and_key sets the certificate chain and private key for a
// TLS client or server. References to the given `CRYPTO_BUFFER` and `EVP_PKEY`
// objects are added as needed. Exactly one of `privkey` or `privkey_method`
// may be non-NULL. Returns one on success and zero on error.
OPENSSL_EXPORT int SSL_CTX_set_chain_and_key(
    SSL_CTX *ctx, CRYPTO_BUFFER *const *certs, size_t num_certs,
    EVP_PKEY *privkey, const SSL_PRIVATE_KEY_METHOD *privkey_method);

// SSL_set_chain_and_key sets the certificate chain and private key for a TLS
// client or server. References to the given `CRYPTO_BUFFER` and `EVP_PKEY`
// objects are added as needed. Exactly one of `privkey` or `privkey_method`
// may be non-NULL. Returns one on success and zero on error.
OPENSSL_EXPORT int SSL_set_chain_and_key(
    SSL *ssl, CRYPTO_BUFFER *const *certs, size_t num_certs, EVP_PKEY *privkey,
    const SSL_PRIVATE_KEY_METHOD *privkey_method);

// SSL_CTX_get0_chain returns the list of `CRYPTO_BUFFER`s that were set by
// `SSL_CTX_set_chain_and_key`. Reference counts are not incremented by this
// call. The return value may be `NULL` if no chain has been set.
//
// (Note: if a chain was configured by non-`CRYPTO_BUFFER`-based functions then
// the return value is undefined and, even if not NULL, the stack itself may
// contain nullptrs. Thus you shouldn't mix this function with
// non-`CRYPTO_BUFFER` functions for manipulating the chain.)
OPENSSL_EXPORT const STACK_OF(CRYPTO_BUFFER) *SSL_CTX_get0_chain(
    const SSL_CTX *ctx);

// SSL_get0_chain returns the list of `CRYPTO_BUFFER`s that were set by
// `SSL_set_chain_and_key`, unless they have been discarded. Reference counts
// are not incremented by this call. The return value may be `NULL` if no chain
// has been set.
//
// (Note: if a chain was configured by non-`CRYPTO_BUFFER`-based functions then
// the return value is undefined and, even if not NULL, the stack itself may
// contain nullptrs. Thus you shouldn't mix this function with
// non-`CRYPTO_BUFFER` functions for manipulating the chain.)
//
// This function may return nullptr if a handshake has completed even if
// `SSL_set_chain_and_key` was previously called, since the configuration
// containing the certificates is typically cleared after handshake completion.
OPENSSL_EXPORT const STACK_OF(CRYPTO_BUFFER) *SSL_get0_chain(const SSL *ssl);

// SSL_CTX_use_RSAPrivateKey sets `ctx`'s private key to `rsa`. It returns one
// on success and zero on failure.
OPENSSL_EXPORT int SSL_CTX_use_RSAPrivateKey(SSL_CTX *ctx, RSA *rsa);

// SSL_use_RSAPrivateKey sets `ctx`'s private key to `rsa`. It returns one on
// success and zero on failure.
OPENSSL_EXPORT int SSL_use_RSAPrivateKey(SSL *ssl, RSA *rsa);

// The following functions configure certificates or private keys but take as
// input DER-encoded structures. They return one on success and zero on
// failure.

OPENSSL_EXPORT int SSL_CTX_use_certificate_ASN1(SSL_CTX *ctx, size_t der_len,
                                                const uint8_t *der);
OPENSSL_EXPORT int SSL_use_certificate_ASN1(SSL *ssl, const uint8_t *der,
                                            size_t der_len);

OPENSSL_EXPORT int SSL_CTX_use_PrivateKey_ASN1(int pk, SSL_CTX *ctx,
                                               const uint8_t *der,
                                               size_t der_len);
OPENSSL_EXPORT int SSL_use_PrivateKey_ASN1(int type, SSL *ssl,
                                           const uint8_t *der, size_t der_len);

OPENSSL_EXPORT int SSL_CTX_use_RSAPrivateKey_ASN1(SSL_CTX *ctx,
                                                  const uint8_t *der,
                                                  size_t der_len);
OPENSSL_EXPORT int SSL_use_RSAPrivateKey_ASN1(SSL *ssl, const uint8_t *der,
                                              size_t der_len);

// The following functions configure certificates or private keys but take as
// input files to read from. They return one on success and zero on failure. The
// `type` parameter is one of the `SSL_FILETYPE_*` values and determines whether
// the file's contents are read as PEM or DER.

#define SSL_FILETYPE_PEM 1
#define SSL_FILETYPE_ASN1 2

OPENSSL_EXPORT int SSL_CTX_use_RSAPrivateKey_file(SSL_CTX *ctx,
                                                  const char *file, int type);
OPENSSL_EXPORT int SSL_use_RSAPrivateKey_file(SSL *ssl, const char *file,
                                              int type);

OPENSSL_EXPORT int SSL_CTX_use_certificate_file(SSL_CTX *ctx, const char *file,
                                                int type);
OPENSSL_EXPORT int SSL_use_certificate_file(SSL *ssl, const char *file,
                                            int type);

OPENSSL_EXPORT int SSL_CTX_use_PrivateKey_file(SSL_CTX *ctx, const char *file,
                                               int type);
OPENSSL_EXPORT int SSL_use_PrivateKey_file(SSL *ssl, const char *file,
                                           int type);

// SSL_CTX_use_certificate_chain_file configures certificates for `ctx`. It
// reads the contents of `file` as a PEM-encoded leaf certificate followed
// optionally by the certificate chain to send to the peer. It returns one on
// success and zero on failure.
//
// WARNING: If the input contains "TRUSTED CERTIFICATE" PEM blocks, this
// function parses auxiliary properties as in `d2i_X509_AUX`. Passing untrusted
// input to this function allows an attacker to influence those properties. See
// `d2i_X509_AUX` for details.
OPENSSL_EXPORT int SSL_CTX_use_certificate_chain_file(SSL_CTX *ctx,
                                                      const char *file);

// SSL_CTX_set_default_passwd_cb sets the password callback for PEM-based
// convenience functions called on `ctx`.
OPENSSL_EXPORT void SSL_CTX_set_default_passwd_cb(SSL_CTX *ctx,
                                                  pem_password_cb *cb);

// SSL_CTX_get_default_passwd_cb returns the callback set by
// `SSL_CTX_set_default_passwd_cb`.
OPENSSL_EXPORT pem_password_cb *SSL_CTX_get_default_passwd_cb(
    const SSL_CTX *ctx);

// SSL_CTX_set_default_passwd_cb_userdata sets the userdata parameter for
// `ctx`'s password callback.
OPENSSL_EXPORT void SSL_CTX_set_default_passwd_cb_userdata(SSL_CTX *ctx,
                                                           void *data);

// SSL_CTX_get_default_passwd_cb_userdata returns the userdata parameter set by
// `SSL_CTX_set_default_passwd_cb_userdata`.
OPENSSL_EXPORT void *SSL_CTX_get_default_passwd_cb_userdata(const SSL_CTX *ctx);


// Custom private keys.

enum ssl_private_key_result_t BORINGSSL_ENUM_INT {
  ssl_private_key_success,
  ssl_private_key_retry,
  ssl_private_key_failure,
};

// ssl_private_key_method_st (aka `SSL_PRIVATE_KEY_METHOD`) describes private
// key hooks. This is used to off-load signing operations to a custom,
// potentially asynchronous, backend. Metadata about the key such as the type
// and size are parsed out of the certificate.
struct ssl_private_key_method_st {
  // sign signs the message `in` in using the specified signature algorithm. On
  // success, it returns `ssl_private_key_success` and writes at most `max_out`
  // bytes of signature data to `out` and sets `*out_len` to the number of bytes
  // written. On failure, it returns `ssl_private_key_failure`. If the operation
  // has not completed, it returns `ssl_private_key_retry`. `sign` should
  // arrange for the high-level operation on `ssl` to be retried when the
  // operation is completed. This will result in a call to `complete`.
  //
  // `signature_algorithm` is one of the `SSL_SIGN_*` values, as defined in TLS
  // 1.3. Note that, in TLS 1.2, ECDSA algorithms do not require that curve
  // sizes match hash sizes, so the curve portion of `SSL_SIGN_ECDSA_*` values
  // must be ignored. BoringSSL will internally handle the curve matching logic
  // where appropriate.
  //
  // It is an error to call `sign` while another private key operation is in
  // progress on `ssl`.
  enum ssl_private_key_result_t (*sign)(SSL *ssl, uint8_t *out, size_t *out_len,
                                        size_t max_out,
                                        uint16_t signature_algorithm,
                                        const uint8_t *in, size_t in_len);

  // decrypt decrypts `in_len` bytes of encrypted data from `in`. On success it
  // returns `ssl_private_key_success`, writes at most `max_out` bytes of
  // decrypted data to `out` and sets `*out_len` to the actual number of bytes
  // written. On failure it returns `ssl_private_key_failure`. If the operation
  // has not completed, it returns `ssl_private_key_retry`. The caller should
  // arrange for the high-level operation on `ssl` to be retried when the
  // operation is completed, which will result in a call to `complete`. This
  // function only works with RSA keys and should perform a raw RSA decryption
  // operation with no padding.
  //
  // It is an error to call `decrypt` while another private key operation is in
  // progress on `ssl`.
  enum ssl_private_key_result_t (*decrypt)(SSL *ssl, uint8_t *out,
                                           size_t *out_len, size_t max_out,
                                           const uint8_t *in, size_t in_len);

  // complete completes a pending operation. If the operation has completed, it
  // returns `ssl_private_key_success` and writes the result to `out` as in
  // `sign`. Otherwise, it returns `ssl_private_key_failure` on failure and
  // `ssl_private_key_retry` if the operation is still in progress.
  //
  // `complete` may be called arbitrarily many times before completion, but it
  // is an error to call `complete` if there is no pending operation in progress
  // on `ssl`.
  enum ssl_private_key_result_t (*complete)(SSL *ssl, uint8_t *out,
                                            size_t *out_len, size_t max_out);
};

// SSL_set_private_key_method configures a custom private key on `ssl`.
// `key_method` must remain valid for the lifetime of `ssl`.
//
// If using an RSA or ECDSA key, callers should configure signing capabilities
// with `SSL_set_signing_algorithm_prefs`. Otherwise, BoringSSL may select a
// signature algorithm that `key_method` does not support.
OPENSSL_EXPORT void SSL_set_private_key_method(
    SSL *ssl, const SSL_PRIVATE_KEY_METHOD *key_method);

// SSL_CTX_set_private_key_method configures a custom private key on `ctx`.
// `key_method` must remain valid for the lifetime of `ctx`.
//
// If using an RSA or ECDSA key, callers should configure signing capabilities
// with `SSL_CTX_set_signing_algorithm_prefs`. Otherwise, BoringSSL may select a
// signature algorithm that `key_method` does not support.
OPENSSL_EXPORT void SSL_CTX_set_private_key_method(
    SSL_CTX *ctx, const SSL_PRIVATE_KEY_METHOD *key_method);

// SSL_CREDENTIAL_set_private_key_method configures a custom private key on
// `cred`. `key_method` must remain valid for the lifetime of `cred`. It returns
// one on success and zero if `cred` does not use private keys.
//
// If using an RSA or ECDSA key, callers should configure signing capabilities
// with `SSL_CREDENTIAL_set1_signing_algorithm_prefs`. Otherwise, BoringSSL may
// select a signature algorithm that `key_method` does not support. This is not
// necessary for delegated credentials (see `SSL_CREDENTIAL_new_delegated`)
// because delegated credentials only support a single signature algorithm.
//
// Functions in `key_method` will be passed an `SSL` object, but not `cred`
// directly. Use `SSL_get0_selected_credential` to determine the selected
// credential. From there, `SSL_CREDENTIAL_get_ex_data` can be used to look up
// credential-specific state, such as a handle to the private key.
OPENSSL_EXPORT int SSL_CREDENTIAL_set_private_key_method(
    SSL_CREDENTIAL *cred, const SSL_PRIVATE_KEY_METHOD *key_method);

// SSL_can_release_private_key returns one if `ssl` will no longer call into the
// private key and zero otherwise. If the function returns one, the caller can
// release state associated with the private key.
//
// NOTE: This function assumes the caller does not use `SSL_clear` to reuse
// `ssl` for a second connection. If `SSL_clear` is used, BoringSSL may still
// use the private key on the second connection.
OPENSSL_EXPORT int SSL_can_release_private_key(const SSL *ssl);


// Cipher suites.
//
// `SSL_CIPHER` objects represent cipher suites.

DEFINE_CONST_STACK_OF(SSL_CIPHER)

// The following constants are TLS cipher suite protocol IDs, as returned from
// `SSL_CIPHER_get_protocol_id`.
#define SSL_CIPHER_AES_128_GCM_SHA256 0x1301
#define SSL_CIPHER_AES_256_GCM_SHA384 0x1302
#define SSL_CIPHER_CHACHA20_POLY1305_SHA256 0x1303
#define SSL_CIPHER_ECDHE_ECDSA_WITH_AES_128_GCM_SHA256 0xc02b
#define SSL_CIPHER_ECDHE_ECDSA_WITH_AES_256_GCM_SHA384 0xc02c
#define SSL_CIPHER_ECDHE_RSA_WITH_AES_128_GCM_SHA256 0xc02f
#define SSL_CIPHER_ECDHE_RSA_WITH_AES_256_GCM_SHA384 0xc030
#define SSL_CIPHER_ECDHE_RSA_WITH_CHACHA20_POLY1305_SHA256 0xcca8
#define SSL_CIPHER_ECDHE_ECDSA_WITH_CHACHA20_POLY1305_SHA256 0xcca9
#define SSL_CIPHER_ECDHE_PSK_WITH_CHACHA20_POLY1305_SHA256 0xccac
#define SSL_CIPHER_ECDHE_ECDSA_WITH_AES_128_CBC_SHA 0xc009
#define SSL_CIPHER_ECDHE_ECDSA_WITH_AES_256_CBC_SHA 0xc00a
#define SSL_CIPHER_ECDHE_RSA_WITH_AES_128_CBC_SHA 0xc013
#define SSL_CIPHER_ECDHE_RSA_WITH_AES_256_CBC_SHA 0xc014
#define SSL_CIPHER_ECDHE_PSK_WITH_AES_128_CBC_SHA 0xc035
#define SSL_CIPHER_ECDHE_PSK_WITH_AES_256_CBC_SHA 0xc036
#define SSL_CIPHER_ECDHE_ECDSA_WITH_AES_128_CBC_SHA256 0xc023
#define SSL_CIPHER_ECDHE_RSA_WITH_AES_128_CBC_SHA256 0xc027
#define SSL_CIPHER_RSA_WITH_AES_128_GCM_SHA256 0x009c
#define SSL_CIPHER_RSA_WITH_AES_256_GCM_SHA384 0x009d
#define SSL_CIPHER_RSA_WITH_AES_128_CBC_SHA 0x002f
#define SSL_CIPHER_RSA_WITH_AES_256_CBC_SHA 0x0035
#define SSL_CIPHER_PSK_WITH_AES_128_CBC_SHA 0x008c
#define SSL_CIPHER_PSK_WITH_AES_256_CBC_SHA 0x008d
#define SSL_CIPHER_RSA_WITH_3DES_EDE_CBC_SHA 0x000a

// The following constants are not cipher suites, but are used in the protocol
// as signalling values.
#define SSL_CIPHER_EMPTY_RENEGOTIATION_INFO_SCSV 0x00ff
#define SSL_CIPHER_FALLBACK_SCSV 0x5600

// SSL_get_cipher_by_value returns the structure representing a TLS cipher
// suite based on its assigned number, or NULL if unknown. See
// https://www.iana.org/assignments/tls-parameters/tls-parameters.xhtml#tls-parameters-4.
OPENSSL_EXPORT const SSL_CIPHER *SSL_get_cipher_by_value(uint16_t value);

// SSL_CIPHER_get_protocol_id returns `cipher`'s two-byte protocol ID.
OPENSSL_EXPORT uint16_t SSL_CIPHER_get_protocol_id(const SSL_CIPHER *cipher);

// SSL_CIPHER_is_aead returns one if `cipher` uses an AEAD cipher.
OPENSSL_EXPORT int SSL_CIPHER_is_aead(const SSL_CIPHER *cipher);

// SSL_CIPHER_is_block_cipher returns one if `cipher` is a block cipher.
OPENSSL_EXPORT int SSL_CIPHER_is_block_cipher(const SSL_CIPHER *cipher);

// SSL_CIPHER_get_cipher_nid returns the NID for `cipher`'s bulk
// cipher. Possible values are `NID_aes_128_gcm`, `NID_aes_256_gcm`,
// `NID_chacha20_poly1305`, `NID_aes_128_cbc`, `NID_aes_256_cbc`, and
// `NID_des_ede3_cbc`.
OPENSSL_EXPORT int SSL_CIPHER_get_cipher_nid(const SSL_CIPHER *cipher);

// SSL_CIPHER_get_digest_nid returns the NID for `cipher`'s HMAC if it is a
// legacy cipher suite. For modern AEAD-based ciphers (see
// `SSL_CIPHER_is_aead`), it returns `NID_undef`.
//
// Note this function only returns the legacy HMAC digest, not the PRF hash.
OPENSSL_EXPORT int SSL_CIPHER_get_digest_nid(const SSL_CIPHER *cipher);

// SSL_CIPHER_get_kx_nid returns the NID for `cipher`'s key exchange. This may
// be `NID_kx_rsa`, `NID_kx_ecdhe`, or `NID_kx_psk` for TLS 1.2. In TLS 1.3,
// cipher suites do not specify the key exchange, so this function returns
// `NID_kx_any`.
OPENSSL_EXPORT int SSL_CIPHER_get_kx_nid(const SSL_CIPHER *cipher);

// SSL_CIPHER_get_auth_nid returns the NID for `cipher`'s authentication
// type. This may be `NID_auth_rsa`, `NID_auth_ecdsa`, or `NID_auth_psk` for TLS
// 1.2. In TLS 1.3, cipher suites do not specify authentication, so this
// function returns `NID_auth_any`.
OPENSSL_EXPORT int SSL_CIPHER_get_auth_nid(const SSL_CIPHER *cipher);

// SSL_CIPHER_get_handshake_digest returns `cipher`'s PRF hash. If `cipher`
// is a pre-TLS-1.2 cipher, it returns `EVP_md5_sha1` but note these ciphers use
// SHA-256 in TLS 1.2. Other return values may be treated uniformly in all
// applicable versions.
OPENSSL_EXPORT const EVP_MD *SSL_CIPHER_get_handshake_digest(
    const SSL_CIPHER *cipher);

// SSL_CIPHER_get_prf_nid behaves like `SSL_CIPHER_get_handshake_digest` but
// returns the NID constant. Use `SSL_CIPHER_get_handshake_digest` instead.
OPENSSL_EXPORT int SSL_CIPHER_get_prf_nid(const SSL_CIPHER *cipher);

// SSL_CIPHER_get_min_version returns the minimum protocol version required
// for `cipher`.
OPENSSL_EXPORT uint16_t SSL_CIPHER_get_min_version(const SSL_CIPHER *cipher);

// SSL_CIPHER_get_max_version returns the maximum protocol version that
// supports `cipher`.
OPENSSL_EXPORT uint16_t SSL_CIPHER_get_max_version(const SSL_CIPHER *cipher);

// SSL_CIPHER_standard_name returns the standard IETF name for `cipher`. For
// example, "TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256".
// The standard name is always an ASCII string.
OPENSSL_EXPORT const char *SSL_CIPHER_standard_name(const SSL_CIPHER *cipher);

// SSL_CIPHER_get_kx_name returns a string that describes the key-exchange
// method used by `cipher`. For example, "ECDHE_ECDSA". TLS 1.3 AEAD-only
// ciphers return the string "GENERIC".
// The key-exchange method name is always an ASCII string.
OPENSSL_EXPORT const char *SSL_CIPHER_get_kx_name(const SSL_CIPHER *cipher);

// SSL_CIPHER_get_bits returns the strength, in bits, of `cipher`. If
// `out_alg_bits` is not NULL, it writes the number of bits consumed by the
// symmetric algorithm to `*out_alg_bits`.
OPENSSL_EXPORT int SSL_CIPHER_get_bits(const SSL_CIPHER *cipher,
                                       int *out_alg_bits);

// SSL_get_all_cipher_names outputs a list of possible strings
// `SSL_CIPHER_get_name` may return in this version of BoringSSL. It writes at
// most `max_out` entries to `out` and returns the total number it would have
// written, if `max_out` had been large enough. `max_out` may be initially set
// to zero to size the output.
//
// This function is only intended to help initialize tables in callers that want
// possible strings pre-declared. This list would not be suitable to set a list
// of supported features. It is in no particular order, and may contain
// placeholder, experimental, or deprecated values that do not apply to every
// caller. Future versions of BoringSSL may also return strings not in this
// list, so this does not apply if, say, sending strings across services.
// The strings are always ASCII-encoded.
OPENSSL_EXPORT size_t SSL_get_all_cipher_names(const char **out,
                                               size_t max_out);


// SSL_get_all_standard_cipher_names outputs a list of possible strings
// `SSL_CIPHER_standard_name` may return in this version of BoringSSL. It writes
// at most `max_out` entries to `out` and returns the total number it would have
// written, if `max_out` had been large enough. `max_out` may be initially set
// to zero to size the output.
//
// This function is only intended to help initialize tables in callers that want
// possible strings pre-declared. This list would not be suitable to set a list
// of supported features. It is in no particular order, and may contain
// placeholder, experimental, or deprecated values that do not apply to every
// caller. Future versions of BoringSSL may also return strings not in this
// list, so this does not apply if, say, sending strings across services.
// The strings are always ASCII-encoded.
OPENSSL_EXPORT size_t SSL_get_all_standard_cipher_names(const char **out,
                                                        size_t max_out);


// Cipher suite configuration.
//
// OpenSSL uses a mini-language to configure cipher suites. The language
// maintains an ordered list of enabled ciphers, along with an ordered list of
// disabled but available ciphers. Initially, all ciphers are disabled with a
// default ordering. The cipher string is then interpreted as a sequence of
// directives, separated by colons, each of which modifies this state.
//
// Most directives consist of a one character or empty opcode followed by a
// selector which matches a subset of available ciphers.
//
// Available opcodes are:
//
// - The empty opcode enables and appends all matching disabled ciphers to the
//   end of the enabled list. The newly appended ciphers are ordered relative to
//   each other matching their order in the disabled list.
//
// - `-` disables all matching enabled ciphers and prepends them to the disabled
//   list, with relative order from the enabled list preserved. This means the
//   most recently disabled ciphers get highest preference relative to other
//   disabled ciphers if re-enabled.
//
// - `+` moves all matching enabled ciphers to the end of the enabled list, with
//   relative order preserved.
//
// - `!` deletes all matching ciphers, enabled or not, from either list. Deleted
//   ciphers will not matched by future operations.
//
// A selector may be a specific cipher (using either the standard or OpenSSL
// name for the cipher) or one or more rules separated by |+|. The final
// selector matches the intersection of each rule. For instance, `AESGCM+aECDSA`
// matches ECDSA-authenticated AES-GCM ciphers.
//
// Available cipher rules are:
//
// - `ALL` matches all ciphers, except for deprecated ciphers which must be
//   named explicitly.
//
// - `kRSA`, `kDHE`, `kECDHE`, and `kPSK` match ciphers using plain RSA, DHE,
//   ECDHE, and plain PSK key exchanges, respectively. Note that ECDHE_PSK is
//   matched by `kECDHE` and not `kPSK`.
//
// - `aRSA`, `aECDSA`, and `aPSK` match ciphers authenticated by RSA, ECDSA, and
//   a pre-shared key, respectively.
//
// - `RSA`, `DHE`, `ECDHE`, `PSK`, `ECDSA`, and `PSK` are aliases for the
//   corresponding `k*` or `a*` cipher rule. `RSA` is an alias for `kRSA`, not
//   `aRSA`.
//
// - `3DES`, `AES128`, `AES256`, `AES`, `AESGCM`, `CHACHA20` match ciphers
//   whose bulk cipher use the corresponding encryption scheme. Note that
//   `AES`, `AES128`, and `AES256` match both CBC and GCM ciphers.
//
// - `SHA1`, and its alias `SHA`, match legacy cipher suites using HMAC-SHA1.
//
// Deprecated cipher rules:
//
// - `kEDH`, `EDH`, `kEECDH`, and `EECDH` are legacy aliases for `kDHE`, `DHE`,
//   `kECDHE`, and `ECDHE`, respectively.
//
// - `HIGH` is an alias for `ALL`.
//
// - `FIPS` is an alias for `HIGH`.
//
// - `SSLv3` and `TLSv1` match ciphers available in TLS 1.1 or earlier.
//   `TLSv1.2` matches ciphers new in TLS 1.2. This is confusing and should not
//   be used.
//
// Unknown rules are silently ignored by legacy APIs, and rejected by APIs with
// "strict" in the name, which should be preferred. Cipher lists can be long
// and it's easy to commit typos. Strict functions will also reject the use of
// spaces, semi-colons and commas as alternative separators.
//
// The special `@STRENGTH` directive will sort all enabled ciphers by strength.
//
// The `DEFAULT` directive, when appearing at the front of the string, expands
// to the default ordering of available ciphers.
//
// If configuring a server, one may also configure equal-preference groups to
// partially respect the client's preferences when
// `SSL_OP_CIPHER_SERVER_PREFERENCE` is enabled. Ciphers in an equal-preference
// group have equal priority and use the client order. This may be used to
// enforce that AEADs are preferred but select AES-GCM vs. ChaCha20-Poly1305
// based on client preferences. An equal-preference is specified with square
// brackets, combining multiple selectors separated by |. For example:
//
//   [TLS_ECDHE_ECDSA_WITH_CHACHA20_POLY1305_SHA256|TLS_ECDHE_ECDSA_WITH_AES_128_GCM_SHA256]
//
// Once an equal-preference group is used, future directives must be
// opcode-less. Inside an equal-preference group, spaces are not allowed.
//
// TLS 1.3 ciphers do not participate in this mechanism and are instead
// configured by the functions in the next section. Functions to set cipher
// lists do not affect TLS 1.3, and functions to query the cipher list do not
// include TLS 1.3 ciphers.

// SSL_DEFAULT_CIPHER_LIST is the default cipher suite configuration. It is
// substituted when a cipher string starts with 'DEFAULT'.
#define SSL_DEFAULT_CIPHER_LIST "ALL"

// SSL_CTX_set_strict_cipher_list configures the cipher list for `ctx`,
// evaluating `str` as a cipher string and returning error if `str` contains
// anything meaningless. It returns one on success and zero on failure.
OPENSSL_EXPORT int SSL_CTX_set_strict_cipher_list(SSL_CTX *ctx,
                                                  const char *str);

// SSL_CTX_set_cipher_list configures the cipher list for `ctx`, evaluating
// `str` as a cipher string. It returns one on success and zero on failure.
//
// Prefer to use `SSL_CTX_set_strict_cipher_list`. This function tolerates
// garbage inputs, unless an empty cipher list results.
OPENSSL_EXPORT int SSL_CTX_set_cipher_list(SSL_CTX *ctx, const char *str);

// SSL_set_strict_cipher_list configures the cipher list for `ssl`, evaluating
// `str` as a cipher string and returning error if `str` contains anything
// meaningless. It returns one on success and zero on failure.
OPENSSL_EXPORT int SSL_set_strict_cipher_list(SSL *ssl, const char *str);

// SSL_set_cipher_list configures the cipher list for `ssl`, evaluating `str` as
// a cipher string. It returns one on success and zero on failure.
//
// Prefer to use `SSL_set_strict_cipher_list`. This function tolerates garbage
// inputs, unless an empty cipher list results.
OPENSSL_EXPORT int SSL_set_cipher_list(SSL *ssl, const char *str);

// SSL_CTX_get_ciphers returns the cipher list for `ctx`, in order of
// preference.
// TODO(crbug.com/550501994): This should return a const pointer.
OPENSSL_EXPORT STACK_OF(SSL_CIPHER) *SSL_CTX_get_ciphers(const SSL_CTX *ctx);

// SSL_CTX_cipher_in_group returns one if the `i`th cipher (see
// `SSL_CTX_get_ciphers`) is in the same equipreference group as the one
// following it and zero otherwise.
OPENSSL_EXPORT int SSL_CTX_cipher_in_group(const SSL_CTX *ctx, size_t i);

// SSL_get_ciphers returns the cipher list for `ssl`, in order of preference.
// TODO(crbug.com/550501994): This should return a const pointer.
OPENSSL_EXPORT STACK_OF(SSL_CIPHER) *SSL_get_ciphers(const SSL *ssl);


// TLS 1.3 Ciphers.

// SSL_CIPHER_FLAG_* define flags used with `SSL_CTX_set1_tls13_ciphers` and
// `SSL_set1_tls13_ciphers`.
//
// If configuring a server, SSL_CIPHER_FLAG_EQUAL_PREFERENCE_WITH_NEXT indicates
// that the corresponding cipher suite has equal preference with the next member
// of the list of ciphers being configured. Assigning equal preference to a
// range of consecutively listed cipher suites allows a server to partially
// respect the client's preferences.
#define SSL_CIPHER_FLAG_EQUAL_PREFERENCE_WITH_NEXT 0x01

// SSL_CTX_set1_tls13_ciphers sets the preferred TLS 1.3 cipher suites for `ctx`
// to `cipher_ids`. If `flags` is non-null, the preference list is modified by
// the corresponding `flags` for each element, which is a set of
// `SSL_CIPHER_FLAG_*` values ORed together. Each element of `cipher_ids` should
// be a unique one of the `SSL_CIPHER_*` constants corresponding to the protocol
// ID of a TLS 1.3 cipher suite. If `cipher_ids` is empty, TLS 1.3 cipher suites
// will instead be determined by a built-in preference order. `cipher_ids` and
// `flags` (if non-null) should both have `num_cipher_ids` elements. This
// function returns one on success and zero on failure.
OPENSSL_EXPORT int SSL_CTX_set1_tls13_ciphers(SSL_CTX *ctx,
                                              const uint16_t *cipher_ids,
                                              const uint32_t *flags,
                                              size_t num_cipher_ids);

// SSL_set1_tls13_ciphers behaves like `SSL_CTX_set1_tls13_ciphers` except that
// it configures the preferred TLS 1.3 ciphers on `ssl`.
OPENSSL_EXPORT int SSL_set1_tls13_ciphers(SSL *ssl, const uint16_t *cipher_ids,
                                          const uint32_t *flags,
                                          size_t num_cipher_ids);


// Connection information.

// SSL_is_init_finished returns one if `ssl` has completed its initial handshake
// and has no pending handshake. It returns zero otherwise.
OPENSSL_EXPORT int SSL_is_init_finished(const SSL *ssl);

// SSL_in_init returns one if `ssl` has a pending handshake and zero
// otherwise.
OPENSSL_EXPORT int SSL_in_init(const SSL *ssl);

// SSL_in_false_start returns one if `ssl` has a pending handshake that is in
// False Start. `SSL_write` may be called at this point without waiting for the
// peer, but `SSL_read` will complete the handshake before accepting application
// data.
//
// See also `SSL_MODE_ENABLE_FALSE_START`.
OPENSSL_EXPORT int SSL_in_false_start(const SSL *ssl);

// SSL_get_peer_certificate returns the peer's leaf certificate or NULL if the
// peer did not use certificates. The caller must call `X509_free` on the
// result to release it.
OPENSSL_EXPORT X509 *SSL_get_peer_certificate(const SSL *ssl);

// SSL_get_peer_cert_chain returns the peer's certificate chain or NULL if
// unavailable or the peer did not use certificates. This is the unverified list
// of certificates as sent by the peer, not the final chain built during
// verification. The caller does not take ownership of the result.
//
// WARNING: This function behaves differently between client and server. If
// `ssl` is a server, the returned chain does not include the leaf certificate.
// If a client, it does.
OPENSSL_EXPORT STACK_OF(X509) *SSL_get_peer_cert_chain(const SSL *ssl);

// SSL_get_peer_full_cert_chain returns the peer's certificate chain, or NULL if
// unavailable or the peer did not use certificates. This is the unverified list
// of certificates as sent by the peer, not the final chain built during
// verification. The caller does not take ownership of the result.
//
// This is the same as `SSL_get_peer_cert_chain` except that this function
// always returns the full chain, i.e. the first element of the return value
// (if any) will be the leaf certificate. In contrast, `SSL_get_peer_cert_chain`
// returns only the intermediate certificates if the `ssl` is a server.
OPENSSL_EXPORT STACK_OF(X509) *SSL_get_peer_full_cert_chain(const SSL *ssl);

// SSL_get0_peer_certificates returns the peer's certificate chain, or NULL if
// unavailable or the peer did not use certificates. This is the unverified list
// of certificates as sent by the peer, not the final chain built during
// verification. The caller does not take ownership of the result.
//
// This is the `CRYPTO_BUFFER` variant of `SSL_get_peer_full_cert_chain`.
OPENSSL_EXPORT const STACK_OF(CRYPTO_BUFFER) *SSL_get0_peer_certificates(
    const SSL *ssl);

// SSL_get0_signed_cert_timestamp_list sets `*out` and `*out_len` to point to
// `*out_len` bytes of SCT information from the server. This is only valid if
// `ssl` is a client. The SCT information is a SignedCertificateTimestampList
// (including the two leading length bytes).
// See https://tools.ietf.org/html/rfc6962#section-3.3
// If no SCT was received then `*out_len` will be zero on return.
//
// WARNING: the returned data is not guaranteed to be well formed.
OPENSSL_EXPORT void SSL_get0_signed_cert_timestamp_list(const SSL *ssl,
                                                        const uint8_t **out,
                                                        size_t *out_len);

// SSL_get0_ocsp_response sets `*out` and `*out_len` to point to `*out_len`
// bytes of an OCSP response from the server. This is the DER encoding of an
// OCSPResponse type as defined in RFC 2560.
//
// WARNING: the returned data is not guaranteed to be well formed.
OPENSSL_EXPORT void SSL_get0_ocsp_response(const SSL *ssl, const uint8_t **out,
                                           size_t *out_len);

// SSL_get_tls_unique writes at most `max_out` bytes of the tls-unique value
// for `ssl` to `out` and sets `*out_len` to the number of bytes written. It
// returns one on success or zero on error. In general `max_out` should be at
// least 12.
//
// This function will always fail if the initial handshake has not completed.
// The tls-unique value will change after a renegotiation but, since
// renegotiations can be initiated by the server at any point, the higher-level
// protocol must either leave them disabled or define states in which the
// tls-unique value can be read.
//
// The tls-unique value is defined by
// https://tools.ietf.org/html/rfc5929#section-3.1. Due to a weakness in the
// TLS protocol, tls-unique is broken for resumed connections unless the
// Extended Master Secret extension is negotiated. Thus this function will
// return zero if `ssl` performed session resumption unless EMS was used when
// negotiating the original session.
OPENSSL_EXPORT int SSL_get_tls_unique(const SSL *ssl, uint8_t *out,
                                      size_t *out_len, size_t max_out);

// SSL_get_extms_support returns one if the Extended Master Secret extension or
// TLS 1.3 was negotiated. Otherwise, it returns zero.
OPENSSL_EXPORT int SSL_get_extms_support(const SSL *ssl);

// SSL_get_current_cipher returns cipher suite used by `ssl`, or NULL if it has
// not been negotiated yet.
OPENSSL_EXPORT const SSL_CIPHER *SSL_get_current_cipher(const SSL *ssl);

// SSL_session_reused returns one if `ssl` performed an abbreviated handshake
// and zero otherwise.
//
// TODO(davidben): Hammer down the semantics of this API while a handshake,
// initial or renego, is in progress.
OPENSSL_EXPORT int SSL_session_reused(const SSL *ssl);

// SSL_get_secure_renegotiation_support returns one if the peer supports secure
// renegotiation (RFC 5746) or TLS 1.3. Otherwise, it returns zero.
OPENSSL_EXPORT int SSL_get_secure_renegotiation_support(const SSL *ssl);

// SSL_export_keying_material exports a connection-specific secret from `ssl`,
// as specified in RFC 5705. It writes `out_len` bytes to `out` given a label
// and optional context. If `use_context` is zero, the `context` parameter is
// ignored.
//
// To derive the same value, both sides of a connection must use the same output
// length, label, and context. In TLS 1.2 and earlier, using a zero-length
// context and using no context would give different output. In TLS 1.3 and
// later, the output length impacts the derivation, so a truncated longer export
// will not match a shorter export.
//
// It returns one on success and zero otherwise.
OPENSSL_EXPORT int SSL_export_keying_material(const SSL *ssl, uint8_t *out,
                                              size_t out_len, const char *label,
                                              size_t label_len,
                                              const uint8_t *context,
                                              size_t context_len,
                                              int use_context);


// Sessions.
//
// An `SSL_SESSION` represents an SSL session that may be resumed in an
// abbreviated handshake. It is reference-counted and immutable. Once
// established, an `SSL_SESSION` may be shared by multiple `SSL` objects on
// different threads and must not be modified.
//
// Note the TLS notion of "session" is not suitable for application-level
// session state. It is an optional caching mechanism for the handshake. Not all
// connections within an application-level session will reuse TLS sessions. TLS
// sessions may be dropped by the client or ignored by the server at any time.

// SSL_SESSION_new returns a newly-allocated blank `SSL_SESSION` or NULL on
// error. This may be useful when writing tests but should otherwise not be
// used.
OPENSSL_EXPORT SSL_SESSION *SSL_SESSION_new(const SSL_CTX *ctx);

// SSL_SESSION_up_ref increments the reference count of `session` and returns
// one.
OPENSSL_EXPORT int SSL_SESSION_up_ref(SSL_SESSION *session);

// SSL_SESSION_dup_ref increments the reference count of `session` and returns
// the same handle.
OPENSSL_EXPORT SSL_SESSION *SSL_SESSION_dup_ref(const SSL_SESSION *session);

// SSL_SESSION_free decrements the reference count of `session`. If it reaches
// zero, all data referenced by `session` and `session` itself are released.
OPENSSL_EXPORT void SSL_SESSION_free(SSL_SESSION *session);

// SSL_SESSION_to_bytes serializes `in` into a newly allocated buffer and sets
// `*out_data` to that buffer and `*out_len` to its length. The caller takes
// ownership of the buffer and must call `OPENSSL_free` when done. It returns
// one on success and zero on error.
OPENSSL_EXPORT int SSL_SESSION_to_bytes(const SSL_SESSION *in,
                                        uint8_t **out_data, size_t *out_len);

// SSL_SESSION_to_bytes_for_ticket serializes `in`, but excludes the session
// identification information, namely the session ID and ticket.
OPENSSL_EXPORT int SSL_SESSION_to_bytes_for_ticket(const SSL_SESSION *in,
                                                   uint8_t **out_data,
                                                   size_t *out_len);

// SSL_SESSION_from_bytes parses `in_len` bytes from `in` as an SSL_SESSION. It
// returns a newly-allocated `SSL_SESSION` on success or NULL on error.
OPENSSL_EXPORT SSL_SESSION *SSL_SESSION_from_bytes(const uint8_t *in,
                                                   size_t in_len,
                                                   const SSL_CTX *ctx);

// PEM_read_bio_SSL_SESSION reads an `SSL_SESSION` as a PEM block of type "SSL
// SESSION PARAMETERS", as described in `PEM_read_bio_SAMPLE`.
OPENSSL_EXPORT SSL_SESSION *PEM_read_bio_SSL_SESSION(BIO *bio,
                                                     SSL_SESSION **out,
                                                     pem_password_cb *cb,
                                                     void *userdata);

// PEM_read_SSL_SESSION behaves like `PEM_read_bio_SSL_SESSION` but reads from
// `fp`.
OPENSSL_EXPORT SSL_SESSION *PEM_read_SSL_SESSION(FILE *fp, SSL_SESSION **out,
                                                 pem_password_cb *cb,
                                                 void *userdata);

// PEM_write_bio_SSL_SESSION writes `in` to `bio` as a PEM block of type "SSL
// SESSION PARAMETERS", as described in `PEM_write_bio_SAMPLE`.
OPENSSL_EXPORT int PEM_write_bio_SSL_SESSION(BIO *bio, const SSL_SESSION *in);

// PEM_write_SSL_SESSION behaves like `PEM_write_bio_SSL_SESSION` but writes to
// `fp`.
OPENSSL_EXPORT int PEM_write_SSL_SESSION(FILE *fp, const SSL_SESSION *in);

// SSL_SESSION_get_version returns a string describing the TLS or DTLS version
// `session` was established at. For example, "TLSv1.2" or "DTLSv1".
// The version string is always an ASCII string.
OPENSSL_EXPORT const char *SSL_SESSION_get_version(const SSL_SESSION *session);

// SSL_SESSION_get_protocol_version returns the TLS or DTLS version `session`
// was established at.
OPENSSL_EXPORT uint16_t
SSL_SESSION_get_protocol_version(const SSL_SESSION *session);

// SSL_SESSION_set_protocol_version sets `session`'s TLS or DTLS version to
// `version`. This may be useful when writing tests but should otherwise not be
// used. It returns one on success and zero on error.
OPENSSL_EXPORT int SSL_SESSION_set_protocol_version(SSL_SESSION *session,
                                                    uint16_t version);

// SSL_MAX_SSL_SESSION_ID_LENGTH is the maximum length of an SSL session ID.
#define SSL_MAX_SSL_SESSION_ID_LENGTH 32

// SSL_SESSION_get_id returns a pointer to a buffer containing `session`'s
// session ID and sets `*out_len` to its length.
//
// This function should only be used for implementing a TLS session cache. TLS
// sessions are not suitable for application-level session state, and a session
// ID is an implementation detail of the TLS resumption handshake mechanism. Not
// all resumption flows use session IDs, and not all connections within an
// application-level session will reuse TLS sessions.
//
// To determine if resumption occurred, use `SSL_session_reused` instead.
// Comparing session IDs will not give the right result in all cases.
//
// As a workaround for some broken applications, BoringSSL sometimes synthesizes
// arbitrary session IDs for non-ID-based sessions. This behavior may be
// removed in the future.
OPENSSL_EXPORT const uint8_t *SSL_SESSION_get_id(const SSL_SESSION *session,
                                                 unsigned *out_len);

// SSL_SESSION_set1_id sets `session`'s session ID to `sid`, It returns one on
// success and zero on error. This function may be useful in writing tests but
// otherwise should not be used.
OPENSSL_EXPORT int SSL_SESSION_set1_id(SSL_SESSION *session, const uint8_t *sid,
                                       size_t sid_len);

// SSL_SESSION_get_time returns the time at which `session` was established in
// seconds since the UNIX epoch.
OPENSSL_EXPORT uint64_t SSL_SESSION_get_time(const SSL_SESSION *session);

// SSL_SESSION_get_timeout returns the lifetime of `session` in seconds.
OPENSSL_EXPORT uint32_t SSL_SESSION_get_timeout(const SSL_SESSION *session);

// SSL_SESSION_get0_peer returns the peer leaf certificate stored in
// `session`.
//
// TODO(davidben): This should return a const X509 *.
OPENSSL_EXPORT X509 *SSL_SESSION_get0_peer(const SSL_SESSION *session);

// SSL_SESSION_get0_peer_certificates returns the peer certificate chain stored
// in `session`, or NULL if the peer did not use certificates. This is the
// unverified list of certificates as sent by the peer, not the final chain
// built during verification. The caller does not take ownership of the result.
OPENSSL_EXPORT const STACK_OF(CRYPTO_BUFFER) *
SSL_SESSION_get0_peer_certificates(const SSL_SESSION *session);

// SSL_SESSION_get0_peer_rpk returns the peer raw public key stored in
// `session`, or NULL if the peer did not send a raw public key.
OPENSSL_EXPORT EVP_PKEY *SSL_SESSION_get0_peer_rpk(const SSL_SESSION *session);

// SSL_SESSION_get0_signed_cert_timestamp_list sets `*out` and `*out_len` to
// point to `*out_len` bytes of SCT information stored in `session`. This is
// only valid for client sessions. The SCT information is a
// SignedCertificateTimestampList (including the two leading length bytes). See
// https://tools.ietf.org/html/rfc6962#section-3.3 If no SCT was received then
// `*out_len` will be zero on return.
//
// WARNING: the returned data is not guaranteed to be well formed.
OPENSSL_EXPORT void SSL_SESSION_get0_signed_cert_timestamp_list(
    const SSL_SESSION *session, const uint8_t **out, size_t *out_len);

// SSL_SESSION_get0_ocsp_response sets `*out` and `*out_len` to point to
// `*out_len` bytes of an OCSP response from the server. This is the DER
// encoding of an OCSPResponse type as defined in RFC 2560.
//
// WARNING: the returned data is not guaranteed to be well formed.
OPENSSL_EXPORT void SSL_SESSION_get0_ocsp_response(const SSL_SESSION *session,
                                                   const uint8_t **out,
                                                   size_t *out_len);

// SSL_MAX_MASTER_KEY_LENGTH is the maximum length of a master secret.
#define SSL_MAX_MASTER_KEY_LENGTH 48

// SSL_SESSION_get_master_key writes up to `max_out` bytes of `session`'s secret
// to `out` and returns the number of bytes written. If `max_out` is zero, it
// returns the size of the secret.
OPENSSL_EXPORT size_t SSL_SESSION_get_master_key(const SSL_SESSION *session,
                                                 uint8_t *out, size_t max_out);

// SSL_SESSION_set_time sets `session`'s creation time to `time` and returns
// `time`. This function may be useful in writing tests but otherwise should not
// be used.
OPENSSL_EXPORT uint64_t SSL_SESSION_set_time(SSL_SESSION *session,
                                             uint64_t time);

// SSL_SESSION_set_timeout sets `session`'s timeout to `timeout` and returns
// one. This function may be useful in writing tests but otherwise should not
// be used.
OPENSSL_EXPORT uint32_t SSL_SESSION_set_timeout(SSL_SESSION *session,
                                                uint32_t timeout);

// SSL_SESSION_get0_id_context returns a pointer to a buffer containing
// `session`'s session ID context (see `SSL_CTX_set_session_id_context`) and
// sets `*out_len` to its length.
OPENSSL_EXPORT const uint8_t *SSL_SESSION_get0_id_context(
    const SSL_SESSION *session, unsigned *out_len);

// SSL_SESSION_set1_id_context sets `session`'s session ID context (see
// `SSL_CTX_set_session_id_context`) to `sid_ctx`. It returns one on success and
// zero on error. This function may be useful in writing tests but otherwise
// should not be used.
OPENSSL_EXPORT int SSL_SESSION_set1_id_context(SSL_SESSION *session,
                                               const uint8_t *sid_ctx,
                                               size_t sid_ctx_len);

// SSL_SESSION_should_be_single_use returns one if `session` should be
// single-use (TLS 1.3 and later) and zero otherwise.
//
// If this function returns one, clients retain multiple sessions and use each
// only once. This prevents passive observers from correlating connections with
// tickets. See RFC 8446, appendix C.4. If it returns zero, `session` cannot be
// used without leaking a correlator.
OPENSSL_EXPORT int SSL_SESSION_should_be_single_use(const SSL_SESSION *session);

// SSL_SESSION_is_resumable returns one if `session` is complete and contains a
// session ID or ticket. It returns zero otherwise. Note this function does not
// ensure `session` will be resumed. It may be expired, dropped by the server,
// or associated with incompatible parameters.
OPENSSL_EXPORT int SSL_SESSION_is_resumable(const SSL_SESSION *session);

// SSL_SESSION_has_ticket returns one if `session` has a ticket and zero
// otherwise.
OPENSSL_EXPORT int SSL_SESSION_has_ticket(const SSL_SESSION *session);

// SSL_SESSION_get0_ticket sets `*out_ticket` and `*out_len` to `session`'s
// ticket, or NULL and zero if it does not have one. `out_ticket` may be NULL
// if only the ticket length is needed.
OPENSSL_EXPORT void SSL_SESSION_get0_ticket(const SSL_SESSION *session,
                                            const uint8_t **out_ticket,
                                            size_t *out_len);

// SSL_SESSION_set_ticket sets `session`'s ticket to `ticket`. It returns one on
// success and zero on error. This function may be useful in writing tests but
// otherwise should not be used.
OPENSSL_EXPORT int SSL_SESSION_set_ticket(SSL_SESSION *session,
                                          const uint8_t *ticket,
                                          size_t ticket_len);

// SSL_SESSION_get_ticket_lifetime_hint returns ticket lifetime hint of
// `session` in seconds or zero if none was set.
OPENSSL_EXPORT uint32_t
SSL_SESSION_get_ticket_lifetime_hint(const SSL_SESSION *session);

// SSL_SESSION_get0_cipher returns the cipher negotiated by the connection which
// established `session`.
//
// Note that, in TLS 1.3, there is no guarantee that resumptions with `session`
// will use that cipher. Prefer calling `SSL_get_current_cipher` on the `SSL`
// instead.
OPENSSL_EXPORT const SSL_CIPHER *SSL_SESSION_get0_cipher(
    const SSL_SESSION *session);

// SSL_SESSION_has_peer_sha256 returns one if `session` has a SHA-256 hash of
// the peer's certificate retained and zero if the peer did not present a
// certificate or if this was not enabled when `session` was created. See also
// `SSL_CTX_set_retain_only_sha256_of_client_certs`.
OPENSSL_EXPORT int SSL_SESSION_has_peer_sha256(const SSL_SESSION *session);

// SSL_SESSION_get0_peer_sha256 sets `*out_ptr` and `*out_len` to the SHA-256
// hash of the peer certificate retained in `session`, or NULL and zero if it
// does not have one. See also `SSL_CTX_set_retain_only_sha256_of_client_certs`.
OPENSSL_EXPORT void SSL_SESSION_get0_peer_sha256(const SSL_SESSION *session,
                                                 const uint8_t **out_ptr,
                                                 size_t *out_len);

// SSL_SESSION_is_resumable_across_names returns one if `session` may be resumed
// with any identity in the server certificate and zero otherwise. See
// draft-ietf-tls-cross-sni-resumption.
OPENSSL_EXPORT int SSL_SESSION_is_resumable_across_names(
    const SSL_SESSION *session);


// Session caching.
//
// Session caching allows connections to be established more efficiently based
// on saved parameters from a previous connection, called a session (see
// `SSL_SESSION`). The client offers a saved session, using an opaque identifier
// from a previous connection. The server may accept the session, if it has the
// parameters available. Otherwise, it will decline and continue with a full
// handshake.
//
// This requires both the client and the server to retain session state. A
// client does so with a stateful session cache. A server may do the same or, if
// supported by both sides, statelessly using session tickets. For more
// information on the latter, see the next section.
//
// For a server, the library implements a built-in internal session cache as an
// in-memory hash table. Servers may also use `SSL_CTX_sess_set_get_cb` and
// `SSL_CTX_sess_set_new_cb` to implement a custom external session cache. In
// particular, this may be used to share a session cache between multiple
// servers in a large deployment. An external cache may be used in addition to
// or instead of the internal one. Use `SSL_CTX_set_session_cache_mode` to
// toggle the internal cache.
//
// For a client, the only option is an external session cache. Clients may use
// `SSL_CTX_sess_set_new_cb` to register a callback for when new sessions are
// available. These may be cached and, in subsequent compatible connections,
// configured with `SSL_set_session`.
//
// Note that offering or accepting a session short-circuits certificate
// verification and most parameter negotiation. Resuming sessions across
// different contexts may result in security failures and surprising
// behavior. For a typical client, this means sessions for different hosts must
// be cached under different keys. A client that connects to the same host with,
// e.g., different cipher suite settings or client certificates should also use
// separate session caches between those contexts. Servers should also partition
// session caches between SNI hosts with `SSL_CTX_set_session_id_context` or
// `SSL_CREDENTIAL_set1_session_id_context`.
//
// Note also, in TLS 1.2 and earlier, offering sessions allows passive observers
// to correlate different client connections. TLS 1.3 and later fix this,
// provided clients use sessions at most once. Session caches are managed by the
// caller in BoringSSL, so this must be implemented externally. See
// `SSL_SESSION_should_be_single_use` for details.

// SSL_SESS_CACHE_OFF disables all session caching.
#define SSL_SESS_CACHE_OFF 0x0000

// SSL_SESS_CACHE_CLIENT enables session caching for a client. The internal
// cache is never used on a client, so this only enables the callbacks.
#define SSL_SESS_CACHE_CLIENT 0x0001

// SSL_SESS_CACHE_SERVER enables session caching for a server.
#define SSL_SESS_CACHE_SERVER 0x0002

// SSL_SESS_CACHE_BOTH enables session caching for both client and server.
#define SSL_SESS_CACHE_BOTH (SSL_SESS_CACHE_CLIENT | SSL_SESS_CACHE_SERVER)

// SSL_SESS_CACHE_NO_AUTO_CLEAR disables automatically calling
// `SSL_CTX_flush_sessions` every 255 connections.
#define SSL_SESS_CACHE_NO_AUTO_CLEAR 0x0080

// SSL_SESS_CACHE_NO_INTERNAL_LOOKUP, on a server, disables looking up a session
// from the internal session cache.
#define SSL_SESS_CACHE_NO_INTERNAL_LOOKUP 0x0100

// SSL_SESS_CACHE_NO_INTERNAL_STORE, on a server, disables storing sessions in
// the internal session cache.
#define SSL_SESS_CACHE_NO_INTERNAL_STORE 0x0200

// SSL_SESS_CACHE_NO_INTERNAL, on a server, disables the internal session
// cache.
#define SSL_SESS_CACHE_NO_INTERNAL \
  (SSL_SESS_CACHE_NO_INTERNAL_LOOKUP | SSL_SESS_CACHE_NO_INTERNAL_STORE)

// SSL_CTX_set_session_cache_mode sets the session cache mode bits for `ctx` to
// `mode`. It returns the previous value.
OPENSSL_EXPORT int SSL_CTX_set_session_cache_mode(SSL_CTX *ctx, int mode);

// SSL_CTX_get_session_cache_mode returns the session cache mode bits for
// `ctx`
OPENSSL_EXPORT int SSL_CTX_get_session_cache_mode(const SSL_CTX *ctx);

// SSL_set_session, for a client, configures `ssl` to offer to resume `session`
// in the initial handshake and returns one. The caller retains ownership of
// `session`. Note that configuring a session assumes the authentication in the
// session is valid. For callers that wish to revalidate the session before
// offering, see `SSL_SESSION_get0_peer_certificates`,
// `SSL_SESSION_get0_signed_cert_timestamp_list`, and
// `SSL_SESSION_get0_ocsp_response`.
//
// It is an error to call this function after the handshake has begun.
OPENSSL_EXPORT int SSL_set_session(SSL *ssl, SSL_SESSION *session);

// SSL_DEFAULT_SESSION_TIMEOUT is the default lifetime, in seconds, of a
// session in TLS 1.2 or earlier. This is how long we are willing to use the
// secret to encrypt traffic without fresh key material.
#define SSL_DEFAULT_SESSION_TIMEOUT (2 * 60 * 60)

// SSL_DEFAULT_SESSION_PSK_DHE_TIMEOUT is the default lifetime, in seconds, of a
// session for TLS 1.3 psk_dhe_ke. This is how long we are willing to use the
// secret as an authenticator.
#define SSL_DEFAULT_SESSION_PSK_DHE_TIMEOUT (2 * 24 * 60 * 60)

// SSL_DEFAULT_SESSION_AUTH_TIMEOUT is the default non-renewable lifetime, in
// seconds, of a TLS 1.3 session. This is how long we are willing to trust the
// signature in the initial handshake.
#define SSL_DEFAULT_SESSION_AUTH_TIMEOUT (7 * 24 * 60 * 60)

// SSL_CTX_set_timeout sets the lifetime, in seconds, of TLS 1.2 (or earlier)
// sessions created in `ctx` to `timeout`.
OPENSSL_EXPORT uint32_t SSL_CTX_set_timeout(SSL_CTX *ctx, uint32_t timeout);

// SSL_CTX_set_session_psk_dhe_timeout sets the lifetime, in seconds, of TLS 1.3
// sessions created in `ctx` to `timeout`.
OPENSSL_EXPORT void SSL_CTX_set_session_psk_dhe_timeout(SSL_CTX *ctx,
                                                        uint32_t timeout);

// SSL_CTX_get_timeout returns the lifetime, in seconds, of TLS 1.2 (or earlier)
// sessions created in `ctx`.
OPENSSL_EXPORT uint32_t SSL_CTX_get_timeout(const SSL_CTX *ctx);

// SSL_MAX_SID_CTX_LENGTH is the maximum length of a session ID context.
#define SSL_MAX_SID_CTX_LENGTH 32

// SSL_CTX_set_session_id_context sets `ctx`'s session ID context to `sid_ctx`.
// It returns one on success and zero on error. The session ID context is an
// application-defined opaque byte string used to partition session resumption.
// A session will not be used in a connection without a matching session ID
// context.
//
// See also `SSL_CREDENTIAL_set1_session_id_context`.
OPENSSL_EXPORT int SSL_CTX_set_session_id_context(SSL_CTX *ctx,
                                                  const uint8_t *sid_ctx,
                                                  size_t sid_ctx_len);

// SSL_set_session_id_context sets `ssl`'s session ID context to `sid_ctx`. It
// returns one on success and zero on error. See also
// `SSL_CTX_set_session_id_context`.
OPENSSL_EXPORT int SSL_set_session_id_context(SSL *ssl, const uint8_t *sid_ctx,
                                              size_t sid_ctx_len);

// SSL_get0_session_id_context returns a pointer to `ssl`'s session ID context
// and sets `*out_len` to its length.  It returns NULL on error.
OPENSSL_EXPORT const uint8_t *SSL_get0_session_id_context(const SSL *ssl,
                                                          size_t *out_len);

// SSL_SESSION_CACHE_MAX_SIZE_DEFAULT is the default maximum size of a session
// cache.
#define SSL_SESSION_CACHE_MAX_SIZE_DEFAULT (1024 * 20)

// SSL_CTX_sess_set_cache_size sets the maximum size of `ctx`'s internal session
// cache to `size`. It returns the previous value.
OPENSSL_EXPORT unsigned long SSL_CTX_sess_set_cache_size(SSL_CTX *ctx,
                                                         unsigned long size);

// SSL_CTX_sess_get_cache_size returns the maximum size of `ctx`'s internal
// session cache.
OPENSSL_EXPORT unsigned long SSL_CTX_sess_get_cache_size(const SSL_CTX *ctx);

// SSL_CTX_sess_number returns the number of sessions in `ctx`'s internal
// session cache.
OPENSSL_EXPORT size_t SSL_CTX_sess_number(const SSL_CTX *ctx);

// SSL_CTX_add_session inserts `session` into `ctx`'s internal session cache. It
// returns one on success and zero on error or if `session` is already in the
// cache. The caller retains its reference to `session`. A `session` can be
// only in one `ctx` at any given time; it is an error to add it to more.
//
// TODO(crbug.com/527997772): Remove this restriction.
OPENSSL_EXPORT int SSL_CTX_add_session(SSL_CTX *ctx, SSL_SESSION *session);

// SSL_CTX_remove_session removes `session` from `ctx`'s internal session cache.
// It returns one on success and zero if `session` was not in the cache.
OPENSSL_EXPORT int SSL_CTX_remove_session(SSL_CTX *ctx, SSL_SESSION *session);

// SSL_CTX_flush_sessions removes all sessions from `ctx` which have expired as
// of time `time`. If `time` is zero, all sessions are removed.
OPENSSL_EXPORT void SSL_CTX_flush_sessions(SSL_CTX *ctx, uint64_t time);

// SSL_new_session_cb is the type of the callback that is called when a new
// session is established and ready to be cached.
typedef int (*SSL_new_session_cb)(SSL *ssl, SSL_SESSION *session);

// SSL_CTX_sess_set_new_cb sets the callback to be called when a new session is
// established and ready to be cached. If the session cache is disabled (the
// appropriate one of `SSL_SESS_CACHE_CLIENT` or `SSL_SESS_CACHE_SERVER` is
// unset), the callback is not called.
//
// The callback is passed a reference to `session`. It returns one if it takes
// ownership (and then calls `SSL_SESSION_free` when done) and zero otherwise. A
// consumer which places `session` into an in-memory cache will likely return
// one, with the cache calling `SSL_SESSION_free`. A consumer which serializes
// `session` with `SSL_SESSION_to_bytes` may not need to retain `session` and
// will likely return zero. Returning one is equivalent to calling
// `SSL_SESSION_up_ref` and then returning zero.
//
// Note: For a client, the callback may be called on abbreviated handshakes if a
// ticket is renewed. Further, it may not be called until some time after
// `SSL_do_handshake` or `SSL_connect` completes if False Start is enabled. Thus
// it's recommended to use this callback over calling `SSL_get_session` on
// handshake completion.
OPENSSL_EXPORT void SSL_CTX_sess_set_new_cb(SSL_CTX *ctx,
                                            SSL_new_session_cb new_session_cb);

// SSL_CTX_sess_get_new_cb returns the callback set by
// `SSL_CTX_sess_set_new_cb`.
OPENSSL_EXPORT SSL_new_session_cb SSL_CTX_sess_get_new_cb(SSL_CTX *ctx);

// SSL_remove_session_cb is the type of the callback that is called when a
// session is removed from the internal session cache.
typedef void (*SSL_remove_session_cb)(SSL_CTX *ctx, SSL_SESSION *session);

// SSL_CTX_sess_set_remove_cb sets a callback which is called when a session is
// removed from the internal session cache.
//
// TODO(davidben): What is the point of this callback? It seems useless since it
// only fires on sessions in the internal cache.
OPENSSL_EXPORT void SSL_CTX_sess_set_remove_cb(
    SSL_CTX *ctx, SSL_remove_session_cb remove_session_cb);

// SSL_CTX_sess_get_remove_cb returns the callback set by
// `SSL_CTX_sess_set_remove_cb`.
OPENSSL_EXPORT SSL_remove_session_cb SSL_CTX_sess_get_remove_cb(SSL_CTX *ctx);

// SSL_get_session_cb is the type of the callback that is called to look up a
// session by ID for a server.
typedef SSL_SESSION *(*SSL_get_session_cb)(SSL *ssl, const uint8_t *id,
                                           int id_len, int *out_copy);

// SSL_CTX_sess_set_get_cb sets a callback to look up a session by ID for a
// server. The callback is passed the session ID and should return a matching
// `SSL_SESSION` or NULL if not found. It should set `*out_copy` to zero and
// return a new reference to the session. This callback is not used for a
// client.
//
// For historical reasons, if `*out_copy` is set to one (default), the SSL
// library will take a new reference to the returned `SSL_SESSION`, expecting
// the callback to return a non-owning pointer. This is not recommended. If
// `ctx` and thus the callback is used on multiple threads, the session may be
// removed and invalidated before the SSL library calls `SSL_SESSION_up_ref`,
// whereas the callback may synchronize internally.
//
// To look up a session asynchronously, the callback may return
// `SSL_magic_pending_session_ptr`. See the documentation for that function and
// `SSL_ERROR_PENDING_SESSION`.
//
// If the internal session cache is enabled, the callback is only consulted if
// the internal cache does not return a match.
OPENSSL_EXPORT void SSL_CTX_sess_set_get_cb(SSL_CTX *ctx,
                                            SSL_get_session_cb get_session_cb);

// SSL_CTX_sess_get_get_cb returns the callback set by
// `SSL_CTX_sess_set_get_cb`.
OPENSSL_EXPORT SSL_get_session_cb SSL_CTX_sess_get_get_cb(SSL_CTX *ctx);

// SSL_magic_pending_session_ptr returns a magic `SSL_SESSION`* which indicates
// that the session isn't currently unavailable. `SSL_get_error` will then
// return `SSL_ERROR_PENDING_SESSION` and the handshake can be retried later
// when the lookup has completed.
OPENSSL_EXPORT SSL_SESSION *SSL_magic_pending_session_ptr(void);

// SSL_CTX_set_resumption_across_names_enabled configures whether `ctx`, as a
// TLS 1.3 server, signals its sessions are compatible with any identity in the
// server certificate, e.g. all DNS names in the subjectAlternateNames list.
// This does not change BoringSSL's resumption behavior, only whether it signals
// this to the client. See draft-ietf-tls-cross-sni-resumption.
//
// When this is enabled, all identities in the server certificate should by
// hosted by servers that accept TLS 1.3 tickets issued by `ctx`. The connection
// will otherwise function, but performance may suffer from clients wasting
// single-use tickets.
OPENSSL_EXPORT void SSL_CTX_set_resumption_across_names_enabled(SSL_CTX *ctx,
                                                                int enabled);

// SSL_set_resumption_across_names_enabled configures whether `ssl`, as a
// TLS 1.3 server, signals its sessions are compatible with any identity in the
// server certificate, e.g. all DNS names in the subjectAlternateNames list.
// This does not change BoringSSL's resumption behavior, only whether it signals
// this to the client. See draft-ietf-tls-cross-sni-resumption.
//
// When this is enabled, all identities in the server certificate should by
// hosted by servers that accept TLS 1.3 tickets issued by `ssl`. The connection
// will otherwise function, but performance may suffer from clients wasting
// single-use tickets.
OPENSSL_EXPORT void SSL_set_resumption_across_names_enabled(SSL *ssl,
                                                            int enabled);


// Session tickets.
//
// Session tickets, from RFC 5077, allow session resumption without server-side
// state. The server maintains a secret ticket key and sends the client opaque
// encrypted session parameters, called a ticket. When offering the session, the
// client sends the ticket which the server decrypts to recover session state.
// Session tickets are enabled by default but may be disabled with
// `SSL_OP_NO_TICKET`.
//
// On the client, ticket-based sessions use the same APIs as ID-based tickets.
// Callers do not need to handle them differently.
//
// On the server, tickets are encrypted and authenticated with a secret key.
// By default, an `SSL_CTX` will manage session ticket encryption keys by
// generating them internally and rotating every 48 hours. Tickets are minted
// and processed transparently. The following functions may be used to configure
// a persistent key or implement more custom behavior, including key rotation
// and sharing keys between multiple servers in a large deployment. There are
// three levels of customisation possible:
//
// 1) One can simply set the keys with `SSL_CTX_set_tlsext_ticket_keys`.
// 2) One can configure an `EVP_CIPHER_CTX` and `HMAC_CTX` directly for
//    encryption and authentication.
// 3) One can configure an `SSL_TICKET_AEAD_METHOD` to have more control
//    and the option of asynchronous decryption.
//
// An attacker that compromises a server's session ticket key can impersonate
// the server and, prior to TLS 1.3, retroactively decrypt all application
// traffic from sessions using that ticket key. Thus ticket keys must be
// regularly rotated for forward secrecy. Note the default key is rotated
// automatically once every 48 hours but manually configured keys are not.

// SSL_DEFAULT_TICKET_KEY_ROTATION_INTERVAL is the interval with which the
// default session ticket encryption key is rotated, if in use. If any
// non-default ticket encryption mechanism is configured, automatic rotation is
// disabled.
#define SSL_DEFAULT_TICKET_KEY_ROTATION_INTERVAL (2 * 24 * 60 * 60)

// SSL_CTX_get_tlsext_ticket_keys writes `ctx`'s session ticket key material to
// `len` bytes of `out`. It returns one on success and zero if `len` is not
// 48. If `out` is NULL, it returns 48 instead.
OPENSSL_EXPORT int SSL_CTX_get_tlsext_ticket_keys(SSL_CTX *ctx, void *out,
                                                  size_t len);

// SSL_CTX_set_tlsext_ticket_keys sets `ctx`'s session ticket key material to
// `len` bytes of `in`. It returns one on success and zero if `len` is not
// 48. If `in` is NULL, it returns 48 instead.
OPENSSL_EXPORT int SSL_CTX_set_tlsext_ticket_keys(SSL_CTX *ctx, const void *in,
                                                  size_t len);

// SSL_TICKET_KEY_NAME_LEN is the length of the key name prefix of a session
// ticket.
#define SSL_TICKET_KEY_NAME_LEN 16

// SSL_CTX_set_tlsext_ticket_key_cb sets the ticket callback to `callback` and
// returns one. `callback` will be called when encrypting a new ticket and when
// decrypting a ticket from the client.
//
// In both modes, `ctx` and `hmac_ctx` will already have been initialized with
// `EVP_CIPHER_CTX_init` and `HMAC_CTX_init`, respectively. `callback`
// configures `hmac_ctx` with an HMAC digest and key, and configures `ctx`
// for encryption or decryption, based on the mode.
//
// When encrypting a new ticket, `encrypt` will be one. It writes a public
// 16-byte key name to `key_name` and a fresh IV to `iv`. The output IV length
// must match `EVP_CIPHER_CTX_iv_length` of the cipher selected. In this mode,
// `callback` returns 1 on success, 0 to decline sending a ticket, and -1 on
// error.
//
// When decrypting a ticket, `encrypt` will be zero. `key_name` will point to a
// 16-byte key name and `iv` points to an IV. The length of the IV consumed must
// match `EVP_CIPHER_CTX_iv_length` of the cipher selected. In this mode,
// `callback` returns -1 to abort the handshake, 0 if the ticket key was
// unrecognized, and 1 or 2 on success. If it returns 2, the ticket will be
// renewed. This may be used to re-key the ticket.
//
// WARNING: `callback` wildly breaks the usual return value convention and is
// called in two different modes.
OPENSSL_EXPORT int SSL_CTX_set_tlsext_ticket_key_cb(
    SSL_CTX *ctx,
    int (*callback)(SSL *ssl, uint8_t *key_name, uint8_t *iv,
                    EVP_CIPHER_CTX *ctx, HMAC_CTX *hmac_ctx, int encrypt));

// ssl_ticket_aead_result_t enumerates the possible results from decrypting a
// ticket with an `SSL_TICKET_AEAD_METHOD`.
enum ssl_ticket_aead_result_t BORINGSSL_ENUM_INT {
  // ssl_ticket_aead_success indicates that the ticket was successfully
  // decrypted.
  ssl_ticket_aead_success,
  // ssl_ticket_aead_retry indicates that the operation could not be
  // immediately completed and must be reattempted, via `open`, at a later
  // point.
  ssl_ticket_aead_retry,
  // ssl_ticket_aead_ignore_ticket indicates that the ticket should be ignored
  // (i.e. is corrupt or otherwise undecryptable).
  ssl_ticket_aead_ignore_ticket,
  // ssl_ticket_aead_error indicates that a fatal error occurred and the
  // handshake should be terminated.
  ssl_ticket_aead_error,
};

// ssl_ticket_aead_method_st (aka `SSL_TICKET_AEAD_METHOD`) contains methods
// for encrypting and decrypting session tickets.
struct ssl_ticket_aead_method_st {
  // max_overhead returns the maximum number of bytes of overhead that `seal`
  // may add.
  size_t (*max_overhead)(SSL *ssl);

  // seal encrypts and authenticates `in_len` bytes from `in`, writes, at most,
  // `max_out_len` bytes to `out`, and puts the number of bytes written in
  // `*out_len`. The `in` and `out` buffers may be equal but will not otherwise
  // alias. It returns one on success or zero on error. If the function returns
  // but `*out_len` is zero, BoringSSL will skip sending a ticket.
  int (*seal)(SSL *ssl, uint8_t *out, size_t *out_len, size_t max_out_len,
              const uint8_t *in, size_t in_len);

  // open authenticates and decrypts `in_len` bytes from `in`, writes, at most,
  // `max_out_len` bytes of plaintext to `out`, and puts the number of bytes
  // written in `*out_len`. The `in` and `out` buffers may be equal but will
  // not otherwise alias. See `ssl_ticket_aead_result_t` for details of the
  // return values. In the case that a retry is indicated, the caller should
  // arrange for the high-level operation on `ssl` to be retried when the
  // operation is completed, which will result in another call to `open`.
  enum ssl_ticket_aead_result_t (*open)(SSL *ssl, uint8_t *out, size_t *out_len,
                                        size_t max_out_len, const uint8_t *in,
                                        size_t in_len);
};

// SSL_CTX_set_ticket_aead_method configures a custom ticket AEAD method table
// on `ctx`. `aead_method` must remain valid for the lifetime of `ctx`.
OPENSSL_EXPORT void SSL_CTX_set_ticket_aead_method(
    SSL_CTX *ctx, const SSL_TICKET_AEAD_METHOD *aead_method);

// SSL_process_tls13_new_session_ticket processes an unencrypted TLS 1.3
// NewSessionTicket message from `buf` and returns a resumable `SSL_SESSION`,
// or NULL on error. The caller takes ownership of the returned session and
// must call `SSL_SESSION_free` to free it.
//
// `buf` contains `buf_len` bytes that represents a complete NewSessionTicket
// message including its header, i.e., one byte for the type (0x04) and three
// bytes for the length. `buf` must contain only one such message.
//
// This function may be used to process NewSessionTicket messages in TLS 1.3
// clients that are handling the record layer externally.
OPENSSL_EXPORT SSL_SESSION *SSL_process_tls13_new_session_ticket(
    SSL *ssl, const uint8_t *buf, size_t buf_len);

// SSL_CTX_set_num_tickets configures `ctx` to send `num_tickets` immediately
// after a successful TLS 1.3 handshake as a server. It returns one. Large
// values of `num_tickets` will be capped within the library.
//
// By default, BoringSSL sends two tickets.
OPENSSL_EXPORT int SSL_CTX_set_num_tickets(SSL_CTX *ctx, size_t num_tickets);

// SSL_CTX_get_num_tickets returns the number of tickets `ctx` will send
// immediately after a successful TLS 1.3 handshake as a server.
OPENSSL_EXPORT size_t SSL_CTX_get_num_tickets(const SSL_CTX *ctx);


// Diffie-Hellman groups and ephemeral key exchanges.
//
// Most TLS handshakes (ECDHE cipher suites in TLS 1.2, and all supported TLS
// 1.3 modes) incorporate an ephemeral key exchange, most commonly using
// Elliptic Curve Diffie-Hellman (ECDH), as described in RFC 8422. The key
// exchange algorithm is negotiated separately from the cipher suite, using
// NamedGroup values, which define Diffie-Hellman groups.
//
// Historically, these values were known as "curves", in reference to ECDH, and
// some APIs refer to the original name. RFC 7919 renamed them to "groups" in
// reference to Diffie-Hellman in general. These values are also used to select
// experimental post-quantum KEMs. Though not Diffie-Hellman groups, KEMs can
// fill a similar role in TLS, so they use the same codepoints.
//
// In TLS 1.2, the ECDH values also negotiate elliptic curves used in ECDSA. In
// TLS 1.3 and later, ECDSA curves are part of the signature algorithm. See
// `SSL_SIGN_*`.

// SSL_GROUP_* define TLS group IDs.
#define SSL_GROUP_SECP256R1 23
#define SSL_GROUP_SECP384R1 24
#define SSL_GROUP_SECP521R1 25
#define SSL_GROUP_X25519 29
#define SSL_GROUP_X25519_MLKEM768 0x11ec
#define SSL_GROUP_MLKEM1024 0x0202

// SSL_CTX_set1_group_ids sets the preferred groups for `ctx` to `group_ids`.
// Each element of `group_ids` should be a unique one of the `SSL_GROUP_*`
// constants. If `group_ids` is empty, a default list will be set instead. It
// returns one on success and zero on failure.
OPENSSL_EXPORT int SSL_CTX_set1_group_ids(SSL_CTX *ctx,
                                          const uint16_t *group_ids,
                                          size_t num_group_ids);

// SSL_set1_group_ids sets the preferred groups for `ssl` to `group_ids`. Each
// element of `group_ids` should be a unique one of the `SSL_GROUP_*` constants.
// If `group_ids` is empty, a default list will be set instead. It returns one
// on success and zero on failure.
OPENSSL_EXPORT int SSL_set1_group_ids(SSL *ssl, const uint16_t *group_ids,
                                      size_t num_group_ids);

// SSL_GROUP_FLAG_* define flags used with SSL_CTX_set1_group_ids_with_flags
// and SSL_set1_group_ids_with_flags.
//
// If configuring a server, SSL_GROUP_FLAG_EQUAL_PREFERENCE_WITH_NEXT indicates
// that the corresponding group has equal preference with the next member of the
// list of groups being configured. Assigning equal preference to a range of
// consecutively listed groups allows a server to partially respect the
// client's preferences when `SSL_OP_CIPHER_SERVER_PREFERENCE` is enabled.
#define SSL_GROUP_FLAG_EQUAL_PREFERENCE_WITH_NEXT 0x01

// SSL_CTX_set1_group_ids_with_flags sets the preferred groups for `ctx` to
// `group_ids`, using the corresponding `flags` for each element, which is a set
// of SSL_GROUP_FLAG_* values ORed together. Each element of `group_ids` should
// be a unique one of the `SSL_GROUP_*` constants. If `group_ids` is empty, a
// default list of groups and flags defaulting to zero will be set instead.
// `group_ids` and `flags` should both have `num_group_ids` elements. It returns
// one on success and zero on failure.
OPENSSL_EXPORT int SSL_CTX_set1_group_ids_with_flags(SSL_CTX *ctx,
                                                     const uint16_t *group_ids,
                                                     const uint32_t *flags,
                                                     size_t num_group_ids);

// SSL_set1_group_ids_with_flags sets the preferred groups for `ssl` to
// `group_ids`, using the corresponding `flags` for each element, which is a set
// of SSL_GROUP_FLAG_* values ORed together. Each element of `group_ids` should
// be a unique one of the `SSL_GROUP_*` constants. If `group_ids` is empty, a
// default list of groups and flags defaulting to zero will be set instead.
// `group_ids` and `flags` should both have `num_group_ids` elements.  It
// returns one on success and zero on failure.
OPENSSL_EXPORT int SSL_set1_group_ids_with_flags(SSL *ssl,
                                                 const uint16_t *group_ids,
                                                 const uint32_t *flags,
                                                 size_t num_group_ids);

// SSL_get_group_id returns the ID of the group used by `ssl`'s most recently
// completed handshake, or 0 if not applicable.
OPENSSL_EXPORT uint16_t SSL_get_group_id(const SSL *ssl);

// SSL_get_group_name returns a human-readable name for the group specified by
// the given TLS group ID, or NULL if the group is unknown.
// The group name is always an ASCII string.
OPENSSL_EXPORT const char *SSL_get_group_name(uint16_t group_id);

// SSL_get_all_group_names outputs a list of possible strings
// `SSL_get_group_name` may return in this version of BoringSSL. It writes at
// most `max_out` entries to `out` and returns the total number it would have
// written, if `max_out` had been large enough. `max_out` may be initially set
// to zero to size the output.
//
// This function is only intended to help initialize tables in callers that want
// possible strings pre-declared. This list would not be suitable to set a list
// of supported features. It is in no particular order, and may contain
// placeholder, experimental, or deprecated values that do not apply to every
// caller. Future versions of BoringSSL may also return strings not in this
// list, so this does not apply if, say, sending strings across services.
// The strings are always ASCII-encoded.
OPENSSL_EXPORT size_t SSL_get_all_group_names(const char **out, size_t max_out);

// The following APIs also configure Diffie-Hellman groups, but use `NID_*`
// constants instead of `SSL_GROUP_*` constants. These are provided for OpenSSL
// compatibility. Where NIDs are unstable constants specific to OpenSSL and
// BoringSSL, group IDs are defined by the TLS protocol. Prefer the group ID
// representation if storing persistently, or exporting to another process or
// library.

// SSL_CTX_set1_groups sets the preferred groups for `ctx` to be `groups`. Each
// element of `groups` should be a unique `NID_*` constant from nid.h. If
// `groups` is empty, a default list will be set instead. It returns one on
// success and zero on failure.
OPENSSL_EXPORT int SSL_CTX_set1_groups(SSL_CTX *ctx, const int *groups,
                                       size_t num_groups);

// SSL_set1_groups sets the preferred groups for `ssl` to be `groups`. Each
// element of `groups` should be a unique `NID_*` constant from nid.h. If
// `groups` is empty, a default list will be set instead. It returns one on
// success and zero on failure.
OPENSSL_EXPORT int SSL_set1_groups(SSL *ssl, const int *groups,
                                   size_t num_groups);

// SSL_CTX_set1_groups_list decodes `groups` as a non-empty colon-separated list
// of group names (e.g. "X25519" or "P-256") and sets `ctx`'s preferred groups
// to the result. The list must not contain duplicates. It returns one on
// success and zero on failure.
OPENSSL_EXPORT int SSL_CTX_set1_groups_list(SSL_CTX *ctx, const char *groups);

// SSL_set1_groups_list decodes `groups` as a non-empty colon-separated list of
// group names (e.g. "X25519" or "P-256") and sets `ssl`'s preferred groups to
// the result. The list must not contain duplicates. It returns one on success
// and zero on failure.
OPENSSL_EXPORT int SSL_set1_groups_list(SSL *ssl, const char *groups);

// SSL_get_negotiated_group returns the NID of the group used by `ssl`'s most
// recently completed handshake, or `NID_undef` if not applicable.
OPENSSL_EXPORT int SSL_get_negotiated_group(const SSL *ssl);


// Client key shares.
//
// The key_share extension in TLS 1.3 (RFC 8446 section 4.2.8) may be sent in
// the initial ClientHello to provide key exchange parameters for a subset of
// the groups offered in the client's supported_groups extension, in hopes of
// saving a round-trip by having proactively started a key exchange for the
// ultimately-negotiated group.
//
// If not otherwise configured, the default client key share selection logic
// outputs key shares for up to two supported groups, at most one of which is
// post-quantum.

// SSL_set1_client_key_shares, when called by a client before the handshake,
// configures `ssl` to send a key_share extension in the initial ClientHello
// containing exactly the groups given by `group_ids`, in the order given. Each
// member of `group_ids` should be one of the `SSL_GROUP_*` constants, and they
// must be unique. This function returns one on success and zero on failure.
//
// If non-empty, the sequence of `group_ids` must be a (not necessarily
// contiguous) subsequence of the groups supported by `ssl`, which may have been
// configured explicitly on `ssl` or its context, or populated by default.
// Caller should finish configuring the group list before calling this function.
// Changing the supported groups for `ssl` after having set client key shares
// will result in the key share selections being reset if this constraint no
// longer holds.
//
// Setting an empty sequence of `group_ids` results in an empty client
// key_share, which will cause the handshake to always take an extra round-trip
// for HelloRetryRequest.
//
// An extra round-trip will be needed if the server's choice of group is not
// among the key shares sent; conversely, sending any key shares other than the
// server's choice wastes CPU and bandwidth (the latter is particularly costly
// for post-quantum key exchanges). To avoid these sub-optimal outcomes,
// key shares should be chosen such that they are likely to be supported by the
// peer server.
OPENSSL_EXPORT int SSL_set1_client_key_shares(SSL *ssl,
                                              const uint16_t *group_ids,
                                              size_t num_group_ids);

// SSL_set1_server_supported_groups_hint, when `ssl` is a client, indicates that
// the server is likely to support groups listed in `server_groups`, in order of
// decreasing server preference. This function returns one on success and zero
// on error. This may be used when receiving a server hint, such as described in
// draft-ietf-tls-key-share-prediction.
//
// If called, `ssl` will try to predict the server's selected named group based
// on `ssl`'s local preferences and `server_groups`. If it predicts a group, it
// will then send an initial ClientHello with key_share extension containing
// only this prediction. In this case, the prediction will supersede any
// configuration from `SSL_set1_client_key_shares`. This is a convenience
// function so that callers do not need to process the server preference list
// themselves.
//
// Groups listed in `server_groups` should be identified by their TLS group IDs,
// such as the `SSL_GROUP_*` constants. A server may implement groups not known
// to BoringSSL, so `server_groups` may contain unrecognized group IDs. If so,
// this function will ignore them.
OPENSSL_EXPORT int SSL_set1_server_supported_groups_hint(
    SSL *ssl, const uint16_t *server_groups, size_t num_server_groups);


// Certificate verification.
//
// SSL may authenticate either endpoint with an X.509 certificate. Typically
// this is used to authenticate the server to the client. These functions
// configure certificate verification.
//
// WARNING: By default, certificate verification errors on a client are not
// fatal. See `SSL_VERIFY_NONE` This may be configured with
// `SSL_CTX_set_verify`.
//
// By default clients are anonymous but a server may request a certificate from
// the client by setting `SSL_VERIFY_PEER`.
//
// Many of these functions use OpenSSL's legacy X.509 stack which is
// underdocumented and deprecated, but the replacement isn't ready yet. For
// now, consumers may use the existing stack or bypass it by performing
// certificate verification externally. This may be done with
// `SSL_CTX_set_cert_verify_callback` or by extracting the chain with
// `SSL_get_peer_cert_chain` after the handshake. In the future, functions will
// be added to use the SSL stack without dependency on any part of the legacy
// X.509 and ASN.1 stack.
//
// To augment certificate verification, a client may also enable OCSP stapling
// (RFC 6066) and Certificate Transparency (RFC 6962) extensions.

// SSL_VERIFY_NONE, on a client, verifies the server certificate but does not
// make errors fatal. The result may be checked with `SSL_get_verify_result`. On
// a server it does not request a client certificate. This is the default.
#define SSL_VERIFY_NONE 0x00

// SSL_VERIFY_PEER, on a client, makes server certificate errors fatal. On a
// server it requests a client certificate and makes errors fatal. However,
// anonymous clients are still allowed. See
// `SSL_VERIFY_FAIL_IF_NO_PEER_CERT`.
#define SSL_VERIFY_PEER 0x01

// SSL_VERIFY_FAIL_IF_NO_PEER_CERT configures a server to reject connections if
// the client declines to send a certificate. This flag must be used together
// with `SSL_VERIFY_PEER`, otherwise it won't work.
#define SSL_VERIFY_FAIL_IF_NO_PEER_CERT 0x02

// SSL_CTX_set_verify configures certificate verification behavior. `mode` is
// one of the `SSL_VERIFY_*` values defined above. `callback` should be NULL.
//
// If `callback` is non-NULL, it is called as in `X509_STORE_CTX_set_verify_cb`,
// which is a deprecated and fragile mechanism to run the default certificate
// verification process, but suppress individual errors in it. See
// `X509_STORE_CTX_set_verify_cb` for details, If set, the callback may use
// `SSL_get_ex_data_X509_STORE_CTX_idx` with `X509_STORE_CTX_get_ex_data` to
// look up the `SSL` from `store_ctx`.
//
// WARNING: `callback` is not suitable for implementing custom certificate
// check, accepting all certificates, or extracting the certificate after
// verification. It does not replace the default process and is called multiple
// times throughout that process. It is also very difficult to implement this
// callback safely, without inadvertently relying on implementation details or
// making incorrect assumptions about when the callback is called.
//
// Instead, use `SSL_CTX_set_custom_verify` or
// `SSL_CTX_set_cert_verify_callback` to customize certificate verification.
// Those callbacks can inspect the peer-sent chain, call `X509_verify_cert` and
// inspect the result, or perform other operations more straightforwardly.
OPENSSL_EXPORT void SSL_CTX_set_verify(
    SSL_CTX *ctx, int mode, int (*callback)(int ok, X509_STORE_CTX *store_ctx));

// SSL_set_verify configures certificate verification behavior. `mode` is one of
// the `SSL_VERIFY_*` values defined above. `callback` should be NULL.
//
// If `callback` is non-NULL, it is called as in `X509_STORE_CTX_set_verify_cb`,
// which is a deprecated and fragile mechanism to run the default certificate
// verification process, but suppress individual errors in it. See
// `X509_STORE_CTX_set_verify_cb` for details, If set, the callback may use
// `SSL_get_ex_data_X509_STORE_CTX_idx` with `X509_STORE_CTX_get_ex_data` to
// look up the `SSL` from `store_ctx`.
//
// WARNING: `callback` is not suitable for implementing custom certificate
// check, accepting all certificates, or extracting the certificate after
// verification. It does not replace the default process and is called multiple
// times throughout that process. It is also very difficult to implement this
// callback safely, without inadvertently relying on implementation details or
// making incorrect assumptions about when the callback is called.
//
// Instead, use `SSL_set_custom_verify` or `SSL_set_cert_verify_callback` to
// customize certificate verification. Those callbacks can inspect the peer-sent
// chain, call `X509_verify_cert` and inspect the result, or perform other
// operations more straightforwardly.
OPENSSL_EXPORT void SSL_set_verify(SSL *ssl, int mode,
                                   int (*callback)(int ok,
                                                   X509_STORE_CTX *store_ctx));

enum ssl_verify_result_t BORINGSSL_ENUM_INT {
  ssl_verify_ok,
  ssl_verify_invalid,
  ssl_verify_retry,
};

// SSL_CTX_set_custom_verify configures certificate verification. `mode` is one
// of the `SSL_VERIFY_*` values defined above. `callback` performs the
// certificate verification.
//
// The callback may call `SSL_get0_peer_certificates` for the certificate chain
// to validate. The callback should return `ssl_verify_ok` if the certificate is
// valid. If the certificate is invalid, the callback should return
// `ssl_verify_invalid` and optionally set `*out_alert` to an alert to send to
// the peer. Some useful alerts include `SSL_AD_CERTIFICATE_EXPIRED`,
// `SSL_AD_CERTIFICATE_REVOKED`, `SSL_AD_UNKNOWN_CA`, `SSL_AD_BAD_CERTIFICATE`,
// `SSL_AD_CERTIFICATE_UNKNOWN`, and `SSL_AD_INTERNAL_ERROR`. See RFC 5246
// section 7.2.2 for their precise meanings. If unspecified,
// `SSL_AD_CERTIFICATE_UNKNOWN` will be sent by default.
//
// To verify a certificate asynchronously, the callback may return
// `ssl_verify_retry`. The handshake will then pause with `SSL_get_error`
// returning `SSL_ERROR_WANT_CERTIFICATE_VERIFY`.
OPENSSL_EXPORT void SSL_CTX_set_custom_verify(
    SSL_CTX *ctx, int mode,
    enum ssl_verify_result_t (*callback)(SSL *ssl, uint8_t *out_alert));

// SSL_set_custom_verify behaves like `SSL_CTX_set_custom_verify` but configures
// an individual `SSL`.
OPENSSL_EXPORT void SSL_set_custom_verify(
    SSL *ssl, int mode,
    enum ssl_verify_result_t (*callback)(SSL *ssl, uint8_t *out_alert));

// SSL_CTX_get_verify_mode returns `ctx`'s verify mode, set by
// `SSL_CTX_set_verify`.
OPENSSL_EXPORT int SSL_CTX_get_verify_mode(const SSL_CTX *ctx);

// SSL_get_verify_mode returns `ssl`'s verify mode, set by `SSL_CTX_set_verify`
// or `SSL_set_verify`.  It returns -1 on error.
OPENSSL_EXPORT int SSL_get_verify_mode(const SSL *ssl);

// SSL_CTX_get_verify_callback returns the callback set by
// `SSL_CTX_set_verify`.
OPENSSL_EXPORT int (*SSL_CTX_get_verify_callback(const SSL_CTX *ctx))(
    int ok, X509_STORE_CTX *store_ctx);

// SSL_get_verify_callback returns the callback set by `SSL_CTX_set_verify` or
// `SSL_set_verify`.
OPENSSL_EXPORT int (*SSL_get_verify_callback(const SSL *ssl))(
    int ok, X509_STORE_CTX *store_ctx);

// SSL_set1_host sets a DNS name that will be required to be present in the
// verified leaf certificate. It returns one on success and zero on error.
//
// Note: unless _some_ name checking is performed, certificate validation is
// ineffective. Simply checking that a host has some certificate from a CA is
// rarely meaningful—you have to check that the CA believed that the host was
// who you expect to be talking to.
//
// By default, both subject alternative names and the subject's common name
// attribute are checked. The latter has long been deprecated, so callers should
// call `SSL_set_hostflags` with `X509_CHECK_FLAG_NEVER_CHECK_SUBJECT` to use
// the standard behavior. https://crbug.com/boringssl/464 tracks fixing the
// default.
OPENSSL_EXPORT int SSL_set1_host(SSL *ssl, const char *hostname);

// SSL_set_hostflags calls `X509_VERIFY_PARAM_set_hostflags` on the
// `X509_VERIFY_PARAM` associated with this `SSL*`. `flags` should be some
// combination of the `X509_CHECK_*` constants.
OPENSSL_EXPORT void SSL_set_hostflags(SSL *ssl, unsigned flags);

// SSL_CTX_set_verify_depth sets the maximum depth of a certificate chain
// accepted in verification. This count excludes both the target certificate and
// the trust anchor (root certificate).
OPENSSL_EXPORT void SSL_CTX_set_verify_depth(SSL_CTX *ctx, int depth);

// SSL_set_verify_depth sets the maximum depth of a certificate chain accepted
// in verification. This count excludes both the target certificate and the
// trust anchor (root certificate).
OPENSSL_EXPORT void SSL_set_verify_depth(SSL *ssl, int depth);

// SSL_CTX_get_verify_depth returns the maximum depth of a certificate accepted
// in verification.
OPENSSL_EXPORT int SSL_CTX_get_verify_depth(const SSL_CTX *ctx);

// SSL_get_verify_depth returns the maximum depth of a certificate accepted in
// verification.
OPENSSL_EXPORT int SSL_get_verify_depth(const SSL *ssl);

// SSL_CTX_set1_param sets verification parameters from `param`. It returns one
// on success and zero on failure. The caller retains ownership of `param`.
OPENSSL_EXPORT int SSL_CTX_set1_param(SSL_CTX *ctx,
                                      const X509_VERIFY_PARAM *param);

// SSL_set1_param sets verification parameters from `param`. It returns one on
// success and zero on failure. The caller retains ownership of `param`.
OPENSSL_EXPORT int SSL_set1_param(SSL *ssl, const X509_VERIFY_PARAM *param);

// SSL_CTX_get0_param returns `ctx`'s `X509_VERIFY_PARAM` for certificate
// verification. The caller must not release the returned pointer but may call
// functions on it to configure it.
OPENSSL_EXPORT X509_VERIFY_PARAM *SSL_CTX_get0_param(SSL_CTX *ctx);

// SSL_get0_param returns `ssl`'s `X509_VERIFY_PARAM` for certificate
// verification. The caller must not release the returned pointer but may call
// functions on it to configure it.
OPENSSL_EXPORT X509_VERIFY_PARAM *SSL_get0_param(SSL *ssl);

// SSL_CTX_set_purpose sets `ctx`'s `X509_VERIFY_PARAM`'s 'purpose' parameter to
// `purpose`. It returns one on success and zero on error.
OPENSSL_EXPORT int SSL_CTX_set_purpose(SSL_CTX *ctx, int purpose);

// SSL_set_purpose sets `ssl`'s `X509_VERIFY_PARAM`'s 'purpose' parameter to
// `purpose`. It returns one on success and zero on error.
OPENSSL_EXPORT int SSL_set_purpose(SSL *ssl, int purpose);

// SSL_CTX_set_trust sets `ctx`'s `X509_VERIFY_PARAM`'s 'trust' parameter to
// `trust`. It returns one on success and zero on error.
OPENSSL_EXPORT int SSL_CTX_set_trust(SSL_CTX *ctx, int trust);

// SSL_set_trust sets `ssl`'s `X509_VERIFY_PARAM`'s 'trust' parameter to
// `trust`. It returns one on success and zero on error.
OPENSSL_EXPORT int SSL_set_trust(SSL *ssl, int trust);

// SSL_CTX_set_cert_store sets `ctx`'s certificate store to `store`. It takes
// ownership of `store`. The store is used for certificate verification.
//
// The store is also used for the auto-chaining feature, but this is deprecated.
// See also `SSL_MODE_NO_AUTO_CHAIN`.
OPENSSL_EXPORT void SSL_CTX_set_cert_store(SSL_CTX *ctx, X509_STORE *store);

// SSL_CTX_get_cert_store returns `ctx`'s certificate store.
OPENSSL_EXPORT X509_STORE *SSL_CTX_get_cert_store(const SSL_CTX *ctx);

// SSL_CTX_set_default_verify_paths calls `X509_STORE_set_default_paths` on
// `ctx`'s store. See that function for details.
//
// Using this function is not recommended. In OpenSSL, these defaults are
// determined by OpenSSL's install prefix. There is no corresponding concept for
// BoringSSL. Future versions of BoringSSL may change or remove this
// functionality.
OPENSSL_EXPORT int SSL_CTX_set_default_verify_paths(SSL_CTX *ctx);

// SSL_CTX_load_verify_locations calls `X509_STORE_load_locations` on `ctx`'s
// store. See that function for details.
OPENSSL_EXPORT int SSL_CTX_load_verify_locations(SSL_CTX *ctx,
                                                 const char *ca_file,
                                                 const char *ca_dir);

// SSL_get_verify_result returns the result of certificate verification. It is
// either `X509_V_OK` or a `X509_V_ERR_*` value.
OPENSSL_EXPORT long SSL_get_verify_result(const SSL *ssl);

// SSL_alert_from_verify_result returns the SSL alert code, such as
// `SSL_AD_CERTIFICATE_EXPIRED`, that corresponds to an `X509_V_ERR_*` value.
// The return value is always an alert, even when `result` is `X509_V_OK`.
OPENSSL_EXPORT int SSL_alert_from_verify_result(long result);

// SSL_get_ex_data_X509_STORE_CTX_idx returns the ex_data index used to look up
// the `SSL` associated with an `X509_STORE_CTX` in the verify callback.
OPENSSL_EXPORT int SSL_get_ex_data_X509_STORE_CTX_idx(void);

// SSL_CTX_set_cert_verify_callback sets a custom callback to be called on
// certificate verification rather than `X509_verify_cert`. `store_ctx` contains
// the verification parameters. The callback should return one on success and
// zero on fatal error. It may use `X509_STORE_CTX_set_error` to set a
// verification result.
//
// The callback may use `SSL_get_ex_data_X509_STORE_CTX_idx` to recover the
// `SSL` object from `store_ctx`.
OPENSSL_EXPORT void SSL_CTX_set_cert_verify_callback(
    SSL_CTX *ctx, int (*callback)(X509_STORE_CTX *store_ctx, void *arg),
    void *arg);

// SSL_enable_signed_cert_timestamps causes `ssl` (which must be the client end
// of a connection) to request SCTs from the server. See
// https://tools.ietf.org/html/rfc6962.
//
// Call `SSL_get0_signed_cert_timestamp_list` to recover the SCT after the
// handshake.
OPENSSL_EXPORT void SSL_enable_signed_cert_timestamps(SSL *ssl);

// SSL_CTX_enable_signed_cert_timestamps enables SCT requests on all client SSL
// objects created from `ctx`.
//
// Call `SSL_get0_signed_cert_timestamp_list` to recover the SCT after the
// handshake.
OPENSSL_EXPORT void SSL_CTX_enable_signed_cert_timestamps(SSL_CTX *ctx);

// SSL_enable_ocsp_stapling causes `ssl` (which must be the client end of a
// connection) to request a stapled OCSP response from the server.
//
// Call `SSL_get0_ocsp_response` to recover the OCSP response after the
// handshake.
OPENSSL_EXPORT void SSL_enable_ocsp_stapling(SSL *ssl);

// SSL_CTX_enable_ocsp_stapling enables OCSP stapling on all client SSL objects
// created from `ctx`.
//
// Call `SSL_get0_ocsp_response` to recover the OCSP response after the
// handshake.
OPENSSL_EXPORT void SSL_CTX_enable_ocsp_stapling(SSL_CTX *ctx);

// SSL_CTX_set0_verify_cert_store sets an `X509_STORE` that will be used
// exclusively for certificate verification and returns one. Ownership of
// `store` is transferred to the `SSL_CTX`.
OPENSSL_EXPORT int SSL_CTX_set0_verify_cert_store(SSL_CTX *ctx,
                                                  X509_STORE *store);

// SSL_CTX_set1_verify_cert_store sets an `X509_STORE` that will be used
// exclusively for certificate verification and returns one. An additional
// reference to `store` will be taken.
OPENSSL_EXPORT int SSL_CTX_set1_verify_cert_store(SSL_CTX *ctx,
                                                  X509_STORE *store);

// SSL_set0_verify_cert_store sets an `X509_STORE` that will be used
// exclusively for certificate verification and returns one. Ownership of
// `store` is transferred to the `SSL`.
OPENSSL_EXPORT int SSL_set0_verify_cert_store(SSL *ssl, X509_STORE *store);

// SSL_set1_verify_cert_store sets an `X509_STORE` that will be used
// exclusively for certificate verification and returns one. An additional
// reference to `store` will be taken.
OPENSSL_EXPORT int SSL_set1_verify_cert_store(SSL *ssl, X509_STORE *store);

// SSL_CTX_set_verify_algorithm_prefs configures `ctx` to use `prefs` as the
// preference list when verifying signatures from the peer's long-term key in
// TLS 1.2 and up. It returns one on zero on error. `prefs` should not include
// the internal-only TLS 1.0 value `SSL_SIGN_RSA_PKCS1_MD5_SHA1`.
//
// This setting is not used in TLS 1.0 and 1.1. Those protocols always sign a
// hardcoded algorithm (an MD5/SHA-1 concatenation for RSA, and SHA-1 for
// ECDSA). BoringSSL will accept those algorithms if and only if those versions
// are used. To disable them, set the minimum version to TLS 1.2 (default) or
// higher.
OPENSSL_EXPORT int SSL_CTX_set_verify_algorithm_prefs(SSL_CTX *ctx,
                                                      const uint16_t *prefs,
                                                      size_t num_prefs);

// SSL_set_verify_algorithm_prefs configures `ssl` to use `prefs` as the
// preference list when verifying signatures from the peer's long-term key in
// TLS 1.2 and up. It returns one on zero on error. `prefs` should not include
// the internal-only TLS 1.0 value `SSL_SIGN_RSA_PKCS1_MD5_SHA1`.
//
// This setting is not used in TLS 1.0 and 1.1. Those protocols always sign a
// hardcoded algorithm (an MD5/SHA-1 concatenation for RSA, and SHA-1 for
// ECDSA). BoringSSL will accept those algorithms if and only if those versions
// are used. To disable them, set the minimum version to TLS 1.2 (default) or
// higher.
OPENSSL_EXPORT int SSL_set_verify_algorithm_prefs(SSL *ssl,
                                                  const uint16_t *prefs,
                                                  size_t num_prefs);


// Certificate authorities.
//
// TLS implementations can send a list of supported certificate authorities to
// guide the peer in selecting a certificate. This was originally defined for
// servers requesting client certificates, but TLS 1.3 generalized it to server
// certificates with the certificate_authorities extension.
//
// The following functions can be used to configure and query this list. They do
// not directly impact certificate verification, only the list of certificate
// authorities sent to the peer.

// SSL_set_client_CA_list sets `ssl`'s client certificate CA list to
// `name_list`. It takes ownership of `name_list`.
OPENSSL_EXPORT void SSL_set_client_CA_list(SSL *ssl,
                                           STACK_OF(X509_NAME) *name_list);

// SSL_CTX_set_client_CA_list sets `ctx`'s client certificate CA list to
// `name_list`. It takes ownership of `name_list`.
OPENSSL_EXPORT void SSL_CTX_set_client_CA_list(SSL_CTX *ctx,
                                               STACK_OF(X509_NAME) *name_list);

// SSL_set0_client_CAs sets `ssl`'s client certificate CA list to `name_list`,
// which should contain DER-encoded distinguished names (RFC 5280). It takes
// ownership of `name_list`.
OPENSSL_EXPORT void SSL_set0_client_CAs(SSL *ssl,
                                        STACK_OF(CRYPTO_BUFFER) *name_list);

// SSL_set0_CA_names sets `ssl`'s CA name list for the certificate authorities
// extension to `name_list`, which should contain DER-encoded distinguished
// names (RFC 5280). It takes ownership of `name_list`.
OPENSSL_EXPORT void SSL_set0_CA_names(SSL *ssl,
                                      STACK_OF(CRYPTO_BUFFER) *name_list);

// SSL_CTX_set0_client_CAs sets `ctx`'s client certificate CA list to
// `name_list`, which should contain DER-encoded distinguished names (RFC 5280).
// It takes ownership of `name_list`.
OPENSSL_EXPORT void SSL_CTX_set0_client_CAs(SSL_CTX *ctx,
                                            STACK_OF(CRYPTO_BUFFER) *name_list);

// SSL_get_client_CA_list returns `ssl`'s client certificate CA list. If `ssl`
// has not been configured as a client, this is the list configured by
// `SSL_CTX_set_client_CA_list`.
//
// If configured as a client, it returns the client certificate CA list sent by
// the server. In this mode, the behavior is undefined except during the
// callbacks set by `SSL_CTX_set_cert_cb` and `SSL_CTX_set_client_cert_cb` or
// when the handshake is paused because of them.
OPENSSL_EXPORT STACK_OF(X509_NAME) *SSL_get_client_CA_list(const SSL *ssl);

// SSL_get0_server_requested_CAs returns the CAs sent by a server to guide a
// client in certificate selection. They are a series of DER-encoded X.509
// names. This function may only be called during a callback set by
// `SSL_CTX_set_cert_cb` or when the handshake is paused because of it.
//
// The returned stack is owned by `ssl`, as are its contents. It should not be
// used past the point where the handshake is restarted after the callback.
OPENSSL_EXPORT const STACK_OF(CRYPTO_BUFFER) *SSL_get0_server_requested_CAs(
    const SSL *ssl);

// SSL_CTX_get_client_CA_list returns `ctx`'s client certificate CA list.
OPENSSL_EXPORT STACK_OF(X509_NAME) *SSL_CTX_get_client_CA_list(
    const SSL_CTX *ctx);

// SSL_add_client_CA appends `x509`'s subject to the client certificate CA list.
// It returns one on success or zero on error. The caller retains ownership of
// `x509`.
OPENSSL_EXPORT int SSL_add_client_CA(SSL *ssl, X509 *x509);

// SSL_CTX_add_client_CA appends `x509`'s subject to the client certificate CA
// list. It returns one on success or zero on error. The caller retains
// ownership of `x509`.
OPENSSL_EXPORT int SSL_CTX_add_client_CA(SSL_CTX *ctx, X509 *x509);

// SSL_load_client_CA_file opens `file` and reads PEM-encoded certificates from
// it. It returns a newly-allocated stack of the certificate subjects or NULL
// on error. Duplicates in `file` are ignored.
OPENSSL_EXPORT STACK_OF(X509_NAME) *SSL_load_client_CA_file(const char *file);

// SSL_dup_CA_list makes a deep copy of `list`. It returns the new list on
// success or NULL on allocation error.
OPENSSL_EXPORT STACK_OF(X509_NAME) *SSL_dup_CA_list(STACK_OF(X509_NAME) *list);

// SSL_add_file_cert_subjects_to_stack behaves like `SSL_load_client_CA_file`
// but appends the result to `out`. It returns one on success or zero on
// error.
OPENSSL_EXPORT int SSL_add_file_cert_subjects_to_stack(STACK_OF(X509_NAME) *out,
                                                       const char *file);

// SSL_add_bio_cert_subjects_to_stack behaves like
// `SSL_add_file_cert_subjects_to_stack` but reads from `bio`.
OPENSSL_EXPORT int SSL_add_bio_cert_subjects_to_stack(STACK_OF(X509_NAME) *out,
                                                      BIO *bio);


// Trust Anchor Identifiers.
//
// The trust_anchors extension, like certificate_authorities, allows clients to
// communicate supported CAs to guide server certificate selection, or vice
// versa. It better supports larger PKIs by referring to CAs by short "trust
// anchor IDs" and, in the server certificate direction, allowing a client to
// advertise only a subset of its full list, with DNS hinting and a retry
// mechanism to manage the subset.
//
// See https://datatracker.ietf.org/doc/draft-ietf-tls-trust-anchor-ids/
//
// BoringSSL currently only implements this for server certificates, and not yet
// client certificates.

// SSL_CREDENTIAL_set1_trust_anchor_id sets `cred`'s trust anchor ID to `id`, or
// clears it if `id_len` is zero. It returns one on success and zero on
// error. If not clearing, `id` must be in binary format (Section 4 of
// draft-ietf-tls-trust-anchor-ids-06) of length `id_len`, and describe the
// issuer of the final certificate in `cred`'s certificate chain.
//
// Additionally, `cred` must enable issuer matching (see
// `SSL_CREDENTIAL_set_must_match_issuer`) for this value to take effect.
//
// For extensibility, callers are recommended to configure this information with
// a CertificatePropertyList. See `SSL_CREDENTIAL_set1_certificate_properties`.
OPENSSL_EXPORT int SSL_CREDENTIAL_set1_trust_anchor_id(SSL_CREDENTIAL *cred,
                                                       const uint8_t *id,
                                                       size_t id_len);

// SSL_CREDENTIAL_add1_trust_anchor_group specifies that `cred` matches all
// trust anchor IDs that match `pattern`. It returns one on success and zero on
// error. This function may be called multiple times to register multiple group
// patterns.
//
// `pattern` is interpreted as the byte representation of a trust anchor ID
// pattern, as described in draft-ietf-tls-trust-anchor-ids.
//
// For extensibility, callers are recommended to configure this information with
// a CertificatePropertyList. See `SSL_CREDENTIAL_set1_certificate_properties`.
OPENSSL_EXPORT int SSL_CREDENTIAL_add1_trust_anchor_group(
    SSL_CREDENTIAL *cred, const uint8_t *pattern, size_t pattern_len);

// SSL_CTX_set1_requested_trust_anchors configures `ctx` to request a
// certificate issued by one of the trust anchors or trust anchor groups in
// `ids`. It returns one on success and zero on error. `ids` must be a list of
// trust anchor IDs in wire-format (a series of non-empty, 8-bit length-prefixed
// strings).
//
// See Section 5.2 of draft-ietf-tls-trust-anchor-ids-06 for guidance on
// determining this list. If applicable, client applications can use
// `SSL_get0_peer_available_trust_anchors` to implement the recovery flow from
// Section 5.6 of draft-ietf-tls-trust-anchor-ids-06.
//
// If empty (`ids_len` is zero), the trust_anchors extension will still be sent
// in ClientHello. This may be used by a client application to signal support
// for the retry flow without requesting specific trust anchors.
//
// This function does not directly impact certificate verification, only the
// list of trust anchors sent to the peer.
OPENSSL_EXPORT int SSL_CTX_set1_requested_trust_anchors(SSL_CTX *ctx,
                                                        const uint8_t *ids,
                                                        size_t ids_len);

// SSL_set1_requested_trust_anchors behaves like
// `SSL_CTX_set1_requested_trust_anchors` but configures the value on `ssl`.
OPENSSL_EXPORT int SSL_set1_requested_trust_anchors(SSL *ssl,
                                                    const uint8_t *ids,
                                                    size_t ids_len);

// SSL_peer_matched_trust_anchor returns one if the peer reported that its
// certificate chain matched one of the trust anchor IDs requested by `ssl`, and
// zero otherwise.
//
// This value is only available during the handshake and is expected to be
// called during certificate verification, e.g. during `SSL_set_custom_verify`
// or `SSL_CTX_set_cert_verify_callback` callbacks. If the value is one, callers
// can safely treat the peer's certificate chain as a pre-built path and skip
// path-building in certificate verification.
OPENSSL_EXPORT int SSL_peer_matched_trust_anchor(const SSL *ssl);

// SSL_get0_peer_available_trust_anchors gets the peer's available trust anchor
// IDs. It sets `*out` and `*out_len` so that `*out` points to `*out_len` bytes
// containing the list in wire format (i.e. a series of non-empty
// 8-bit-length-prefixed strings). If the peer did not provide a list, the
// function will output zero bytes. Only servers can provide available trust
// anchor IDs, so this API will only output a list when `ssl` is a client.
//
// This value is only available during the handshake and is expected to be
// called in the event of certificate verification failure. Client applications
// can use it to retry the connection, requesting different trust anchors. See
// Section 5.6 of draft-ietf-tls-trust-anchor-ids-06 for details.
// `CBS_get_u8_length_prefixed` may be used to iterate over the format.
//
// If needed in other contexts, callers may save the value during certificate
// verification, or at `SSL_CB_HANDSHAKE_DONE` with `SSL_CTX_set_info_callback`.
OPENSSL_EXPORT void SSL_get0_peer_available_trust_anchors(const SSL *ssl,
                                                          const uint8_t **out,
                                                          size_t *out_len);

// SSL_CTX_set1_available_trust_anchors configures `ctx`, as a server, to send
// `ids` as the list of available trust anchors alongside the certificate. It
// returns one on success and zero on error. This list is used to allow the peer
// to retry the connection and request a different trust anchor, if the
// presented certificate is unacceptable. `ids` must be a non-empty list of
// trust anchor IDs in wire-format (a series of non-empty, 8-bit length-prefixed
// strings), in order of decreasing preference.
//
// Most applications will not need to call this. If not configured, BoringSSL
// derives available trust anchors from the credential list (see
// `SSL_CTX_add1_credential`). This function may be used if, for example, the
// caller filters the available credentials by trust anchor in
// `SSL_CTX_set_select_certificate_cb`, such that the credential list visible to
// BoringSSL is incomplete.
OPENSSL_EXPORT int SSL_CTX_set1_available_trust_anchors(SSL_CTX *ctx,
                                                        const uint8_t *ids,
                                                        size_t ids_len);

// SSL_set1_available_trust_anchors behaves like
// `SSL_CTX_set1_available_trust_anchors` but configures the value on `ssl`.
OPENSSL_EXPORT int SSL_set1_available_trust_anchors(SSL *ssl,
                                                    const uint8_t *ids,
                                                    size_t ids_len);


// Server name indication.
//
// The server_name extension (RFC 3546) allows the client to advertise the name
// of the server it is connecting to. This is used in virtual hosting
// deployments to select one of a several certificates on a single IP. Only the
// host_name name type is supported.

#define TLSEXT_NAMETYPE_host_name 0

// SSL_set_tlsext_host_name, for a client, configures `ssl` to advertise `name`
// in the server_name extension. It returns one on success and zero on error.
OPENSSL_EXPORT int SSL_set_tlsext_host_name(SSL *ssl, const char *name);

// SSL_get_servername, for a server, returns the hostname supplied by the
// client or NULL if there was none. The `type` argument must be
// `TLSEXT_NAMETYPE_host_name`.
OPENSSL_EXPORT const char *SSL_get_servername(const SSL *ssl, const int type);

// SSL_get_servername_type, for a server, returns `TLSEXT_NAMETYPE_host_name`
// if the client sent a hostname and -1 otherwise.
OPENSSL_EXPORT int SSL_get_servername_type(const SSL *ssl);

// SSL_CTX_set_tlsext_servername_callback configures `callback` to be called on
// the server after ClientHello extensions have been parsed and returns one.
// The callback may use `SSL_get_servername` to examine the server_name
// extension and returns a `SSL_TLSEXT_ERR_*` value. The value of `arg` may be
// set by calling `SSL_CTX_set_tlsext_servername_arg`.
//
// If the callback returns `SSL_TLSEXT_ERR_NOACK`, the server_name extension is
// not acknowledged in the ServerHello. If the return value is
// `SSL_TLSEXT_ERR_ALERT_FATAL`, then `*out_alert` is the alert to send,
// defaulting to `SSL_AD_UNRECOGNIZED_NAME`. `SSL_TLSEXT_ERR_ALERT_WARNING` is
// ignored and treated as `SSL_TLSEXT_ERR_OK`.
OPENSSL_EXPORT int SSL_CTX_set_tlsext_servername_callback(
    SSL_CTX *ctx, int (*callback)(SSL *ssl, int *out_alert, void *arg));

// SSL_CTX_set_tlsext_servername_arg sets the argument to the servername
// callback and returns one. See `SSL_CTX_set_tlsext_servername_callback`.
OPENSSL_EXPORT int SSL_CTX_set_tlsext_servername_arg(SSL_CTX *ctx, void *arg);

// SSL_TLSEXT_ERR_* are values returned by some extension-related callbacks.
#define SSL_TLSEXT_ERR_OK 0
#define SSL_TLSEXT_ERR_ALERT_WARNING 1
#define SSL_TLSEXT_ERR_ALERT_FATAL 2
#define SSL_TLSEXT_ERR_NOACK 3

// SSL_set_SSL_CTX changes `ssl`'s `SSL_CTX`. `ssl` will use the
// certificate-related settings from `ctx`, and `SSL_get_SSL_CTX` will report
// `ctx`. This function may be used during the callbacks registered by
// `SSL_CTX_set_select_certificate_cb`,
// `SSL_CTX_set_tlsext_servername_callback`, and `SSL_CTX_set_cert_cb` or when
// the handshake is paused from them. It is typically used to switch
// certificates based on SNI.
//
// Note the session cache and related settings will continue to use the initial
// `SSL_CTX`. Callers should use `SSL_CTX_set_session_id_context` to partition
// the session cache between different domains.
//
// TODO(davidben): Should other settings change after this call?
OPENSSL_EXPORT SSL_CTX *SSL_set_SSL_CTX(SSL *ssl, SSL_CTX *ctx);


// Application-layer protocol negotiation.
//
// The ALPN extension (RFC 7301) allows negotiating different application-layer
// protocols over a single port. This is used, for example, to negotiate
// HTTP/2.

// SSL_CTX_set_alpn_protos sets the client ALPN protocol list on `ctx` to
// `protos`. `protos` must be in wire-format (i.e. a series of non-empty, 8-bit
// length-prefixed strings), or the empty string to disable ALPN. It returns
// zero on success and one on failure. Configuring a non-empty string enables
// ALPN on a client. On a client, it will advertise these protocols. On a
// server, it will use them to automatically select a protocol if the client
// supports ALPN and no select callback is set.
//
// Those configuring HTTP/2 must also configure the cipher suite set on the
// SSL_CTX so that the selected cipher is compliant with RFC 7540 Section 9.2.
// Servers should install their own ALPN callback to comply with the RFC.
//
// WARNING: this function is dangerous because it breaks the usual return value
// convention.
OPENSSL_EXPORT int SSL_CTX_set_alpn_protos(SSL_CTX *ctx, const uint8_t *protos,
                                           size_t protos_len);

// SSL_set_alpn_protos sets the client ALPN protocol list on `ssl` to `protos`.
// `protos` must be in wire-format (i.e. a series of non-empty, 8-bit
// length-prefixed strings), or the empty string to disable ALPN. It returns
// zero on success and one on failure. Configuring a non-empty string enables
// ALPN on a client. On a client, it will advertise these protocols. On a
// server, it will use them to automatically select a protocol if the client
// supports ALPN and no select callback is set.
//
// Those configuring HTTP/2 must also configure the cipher suite set on the
// SSL_CTX so that the selected cipher is compliant with RFC 7540 Section 9.2.
// Servers should install their own ALPN callback to comply with the RFC.
//
// WARNING: this function is dangerous because it breaks the usual return value
// convention.
OPENSSL_EXPORT int SSL_set_alpn_protos(SSL *ssl, const uint8_t *protos,
                                       size_t protos_len);

// SSL_CTX_set_alpn_select_cb sets a callback function on `ctx` that is called
// during ClientHello processing in order to select an ALPN protocol from the
// client's list of offered protocols. `SSL_select_next_proto` is an optional
// utility function which may be useful in implementing this callback.
//
// The callback is passed a wire-format (i.e. a series of non-empty, 8-bit
// length-prefixed strings) ALPN protocol list in `in`. To select a protocol,
// the callback should set `*out` and `*out_len` to the selected protocol and
// return `SSL_TLSEXT_ERR_OK` on success. It does not pass ownership of the
// buffer, so `*out` should point to a static string, a buffer that outlives the
// callback call, or the corresponding entry in `in`.
//
// If the server supports ALPN, but there are no protocols in common, the
// callback should return `SSL_TLSEXT_ERR_ALERT_FATAL` to abort the connection
// with a no_application_protocol alert.
//
// If the server does not support ALPN, it can return `SSL_TLSEXT_ERR_NOACK` to
// continue the handshake without negotiating a protocol. This may be useful if
// multiple server configurations share an `SSL_CTX`, only some of which have
// ALPN protocols configured.
//
// `SSL_TLSEXT_ERR_ALERT_WARNING` is ignored and will be treated as
// `SSL_TLSEXT_ERR_NOACK`.
//
// The callback will only be called if the client supports ALPN. Callers that
// wish to require ALPN for all clients must check `SSL_get0_alpn_selected`
// after the handshake. In QUIC connections, this is done automatically.
//
// The cipher suite is selected before negotiating ALPN. The callback may use
// `SSL_get_pending_cipher` to query the cipher suite. This may be used to
// implement HTTP/2's cipher suite constraints.
OPENSSL_EXPORT void SSL_CTX_set_alpn_select_cb(
    SSL_CTX *ctx,
    int (*cb)(SSL *ssl, const uint8_t **out, uint8_t *out_len,
              const uint8_t *in, unsigned in_len, void *arg),
    void *arg);

// SSL_get0_alpn_selected gets the selected ALPN protocol (if any) from `ssl`.
// On return it sets `*out_data` to point to `*out_len` bytes of protocol name
// (not including the leading length-prefix byte). If the server didn't respond
// with a negotiated protocol then `*out_len` will be zero.
OPENSSL_EXPORT void SSL_get0_alpn_selected(const SSL *ssl,
                                           const uint8_t **out_data,
                                           unsigned *out_len);

// SSL_CTX_set_allow_unknown_alpn_protos configures client connections on `ctx`
// to allow unknown ALPN protocols from the server. Otherwise, by default, the
// client will require that the protocol be advertised in
// `SSL_CTX_set_alpn_protos`.
OPENSSL_EXPORT void SSL_CTX_set_allow_unknown_alpn_protos(SSL_CTX *ctx,
                                                          int enabled);


// Application-layer protocol settings
//
// The ALPS extension (draft-vvv-tls-alps) allows exchanging application-layer
// settings in the TLS handshake for applications negotiated with ALPN. Note
// that, when ALPS is negotiated, the client and server each advertise their own
// settings, so there are functions to both configure setting to send and query
// received settings.

// SSL_add_application_settings configures `ssl` to enable ALPS with ALPN
// protocol `proto`, sending an ALPS value of `settings`. It returns one on
// success and zero on error. If `proto` is negotiated via ALPN and the peer
// supports ALPS, `settings` will be sent to the peer. The peer's ALPS value can
// be retrieved with `SSL_get0_peer_application_settings`.
//
// On the client, this function should be called before the handshake, once for
// each supported ALPN protocol which uses ALPS. `proto` must be included in the
// client's ALPN configuration (see `SSL_CTX_set_alpn_protos` and
// `SSL_set_alpn_protos`). On the server, ALPS can be preconfigured for each
// protocol as in the client, or configuration can be deferred to the ALPN
// callback (see `SSL_CTX_set_alpn_select_cb`), in which case only the selected
// protocol needs to be configured.
//
// ALPS can be independently configured from 0-RTT, however changes in protocol
// settings will fallback to 1-RTT to negotiate the new value, so it is
// recommended for `settings` to be relatively stable.
OPENSSL_EXPORT int SSL_add_application_settings(SSL *ssl, const uint8_t *proto,
                                                size_t proto_len,
                                                const uint8_t *settings,
                                                size_t settings_len);

// SSL_get0_peer_application_settings sets `*out_data` and `*out_len` to a
// buffer containing the peer's ALPS value, or the empty string if ALPS was not
// negotiated. Note an empty string could also indicate the peer sent an empty
// settings value. Use `SSL_has_application_settings` to check if ALPS was
// negotiated. The output buffer is owned by `ssl` and is valid until the next
// time `ssl` is modified.
OPENSSL_EXPORT void SSL_get0_peer_application_settings(const SSL *ssl,
                                                       const uint8_t **out_data,
                                                       size_t *out_len);

// SSL_has_application_settings returns one if ALPS was negotiated on this
// connection and zero otherwise.
OPENSSL_EXPORT int SSL_has_application_settings(const SSL *ssl);

// SSL_set_alps_use_new_codepoint configures whether to use the new ALPS
// codepoint. By default, the new codepoint is used.
OPENSSL_EXPORT void SSL_set_alps_use_new_codepoint(SSL *ssl, int use_new);


// Certificate compression.
//
// Certificates in TLS 1.3 can be compressed (RFC 8879). BoringSSL supports this
// as both a client and a server, but does not link against any specific
// compression libraries in order to keep dependencies to a minimum. Instead,
// hooks for compression and decompression can be installed in an `SSL_CTX` to
// enable support.

// ssl_cert_compression_func_t is a pointer to a function that performs
// compression. It must write the compressed representation of `in` to `out`,
// returning one on success and zero on error. The results of compressing
// certificates are not cached internally. Implementations may wish to implement
// their own cache if they expect it to be useful given the certificates that
// they serve.
typedef int (*ssl_cert_compression_func_t)(SSL *ssl, CBB *out,
                                           const uint8_t *in, size_t in_len);

// ssl_cert_decompression_func_t is a pointer to a function that performs
// decompression. The compressed data from the peer is passed as `in` and the
// decompressed result must be exactly `uncompressed_len` bytes long. It returns
// one on success, in which case `*out` must be set to the result of
// decompressing `in`, or zero on error. Setting `*out` transfers ownership,
// i.e. `CRYPTO_BUFFER_free` will be called on `*out` at some point in the
// future. The results of decompressions are not cached internally.
// Implementations may wish to implement their own cache if they expect it to be
// useful.
typedef int (*ssl_cert_decompression_func_t)(SSL *ssl, CRYPTO_BUFFER **out,
                                             size_t uncompressed_len,
                                             const uint8_t *in, size_t in_len);

// SSL_CTX_add_cert_compression_alg registers a certificate compression
// algorithm on `ctx` with ID `alg_id`. (The value of `alg_id` should be an IANA
// assigned value and each can only be registered once.)
//
// One of the function pointers may be NULL to avoid having to implement both
// sides of a compression algorithm if you're only going to use it in one
// direction. In this case, the unimplemented direction acts like it was never
// configured.
//
// For a server, algorithms are registered in preference order with the most
// preferable first. It returns one on success or zero on error.
OPENSSL_EXPORT int SSL_CTX_add_cert_compression_alg(
    SSL_CTX *ctx, uint16_t alg_id, ssl_cert_compression_func_t compress,
    ssl_cert_decompression_func_t decompress);


// Next protocol negotiation.
//
// The NPN extension (draft-agl-tls-nextprotoneg-03) is the predecessor to ALPN
// and deprecated in favor of it.

// SSL_CTX_set_next_protos_advertised_cb sets a callback that is called when a
// TLS server needs a list of supported protocols for Next Protocol Negotiation.
//
// If the callback wishes to advertise NPN to the client, it should return
// `SSL_TLSEXT_ERR_OK` and then set `*out` and `*out_len` to describe to a
// buffer containing a (possibly empty) list of supported protocols in wire
// format. That is, each protocol is prefixed with a 1-byte length, then
// concatenated. From there, the client will select a protocol, possibly one not
// on the server's list. The caller can use `SSL_get0_next_proto_negotiated`
// after the handshake completes to query the final protocol.
//
// The returned buffer must remain valid and unmodified for at least the
// duration of the `SSL` operation (e.g. `SSL_do_handshake`) that triggered the
// callback.
//
// If the caller wishes not to advertise NPN, it should return
// `SSL_TLSEXT_ERR_NOACK`. No NPN extension will be included in the ServerHello,
// and the TLS server will behave as if it does not implement NPN.
OPENSSL_EXPORT void SSL_CTX_set_next_protos_advertised_cb(
    SSL_CTX *ctx,
    int (*cb)(SSL *ssl, const uint8_t **out, unsigned *out_len, void *arg),
    void *arg);

// SSL_CTX_set_next_proto_select_cb sets a callback that is called when a client
// needs to select a protocol from the server's provided list, passed in wire
// format in `in_len` bytes from `in`. The callback can assume that `in` is
// syntactically valid. `SSL_select_next_proto` is an optional utility function
// which may be useful in implementing this callback.
//
// On success, the callback should return `SSL_TLSEXT_ERR_OK` and set `*out` and
// `*out_len` to describe a buffer containing the selected protocol, or an
// empty buffer to select no protocol. The returned buffer may point within
// `in`, or it may point to some other buffer that remains valid and unmodified
// for at least the duration of the `SSL` operation (e.g. `SSL_do_handshake`)
// that triggered the callback.
//
// Returning any other value indicates a fatal error and will terminate the TLS
// connection. To proceed without selecting a protocol, the callback must return
// `SSL_TLSEXT_ERR_OK` and set `*out` and `*out_len` to an empty buffer. (E.g.
// NULL and zero, respectively.)
//
// Configuring this callback enables NPN on a client. Although the callback can
// then decline to negotiate a protocol, merely configuring the callback causes
// the client to offer NPN in the ClientHello. Callers thus should not configure
// this callback in TLS client contexts that are not intended to use NPN.
OPENSSL_EXPORT void SSL_CTX_set_next_proto_select_cb(
    SSL_CTX *ctx,
    int (*cb)(SSL *ssl, uint8_t **out, uint8_t *out_len, const uint8_t *in,
              unsigned in_len, void *arg),
    void *arg);

// SSL_get0_next_proto_negotiated sets `*out_data` and `*out_len` to point to
// the client's requested protocol for this connection. If the client didn't
// request any protocol, then `*out_len` is set to zero.
//
// Note that the client can request any protocol it chooses. The value returned
// from this function need not be a member of the list of supported protocols
// provided by the server.
OPENSSL_EXPORT void SSL_get0_next_proto_negotiated(const SSL *ssl,
                                                   const uint8_t **out_data,
                                                   unsigned *out_len);

// SSL_select_next_proto implements the standard protocol selection for either
// ALPN servers or NPN clients. It is expected that this function is called from
// the callback set by `SSL_CTX_set_alpn_select_cb` or
// `SSL_CTX_set_next_proto_select_cb`.
//
// `peer` and `supported` contain the peer and locally-configured protocols,
// respectively. This function finds the first protocol in `peer` which is also
// in `supported`. If one was found, it sets `*out` and `*out_len` to point to
// it and returns `OPENSSL_NPN_NEGOTIATED`. Otherwise, it returns
// `OPENSSL_NPN_NO_OVERLAP` and sets `*out` and `*out_len` to the first
// supported protocol.
//
// In ALPN, the server should only select protocols among those that the client
// offered. Thus, if this function returns `OPENSSL_NPN_NO_OVERLAP`, the caller
// should ignore `*out` and return `SSL_TLSEXT_ERR_ALERT_FATAL` from
// `SSL_CTX_set_alpn_select_cb`'s callback to indicate there was no match.
//
// In NPN, the client may either select one of the server's protocols, or an
// "opportunistic" protocol as described in Section 6 of
// draft-agl-tls-nextprotoneg-03. When this function returns
// `OPENSSL_NPN_NO_OVERLAP`, `*out` implicitly selects the first supported
// protocol for use as the opportunistic protocol. The caller may use it,
// ignore it and select a different opportunistic protocol, or ignore it and
// select no protocol (empty string).
//
// `peer` and `supported` must be vectors of 8-bit, length-prefixed byte
// strings. The length byte itself is not included in the length. A byte string
// of length 0 is invalid. No byte string may be truncated. `supported` must be
// non-empty; a caller that supports no ALPN/NPN protocols should skip
// negotiating the extension, rather than calling this function. If any of these
// preconditions do not hold, this function will return `OPENSSL_NPN_NO_OVERLAP`
// and set `*out` and `*out_len` to an empty buffer for robustness, but callers
// are not recommended to rely on this. An empty buffer is not a valid output
// for `SSL_CTX_set_alpn_select_cb`'s callback.
//
// WARNING: `*out` and `*out_len` may alias either `peer` or `supported` and may
// not be used after one of those buffers is modified or released. Additionally,
// this function is not const-correct for compatibility reasons. Although `*out`
// is a non-const pointer, callers may not modify the buffer though `*out`.
OPENSSL_EXPORT int SSL_select_next_proto(uint8_t **out, uint8_t *out_len,
                                         const uint8_t *peer, unsigned peer_len,
                                         const uint8_t *supported,
                                         unsigned supported_len);

#define OPENSSL_NPN_UNSUPPORTED 0
#define OPENSSL_NPN_NEGOTIATED 1
#define OPENSSL_NPN_NO_OVERLAP 2


// Channel ID.
//
// See draft-balfanz-tls-channelid-01. This is an old, experimental mechanism
// and should not be used in new code.

// SSL_CTX_set_tls_channel_id_enabled configures whether connections associated
// with `ctx` should enable Channel ID as a server.
OPENSSL_EXPORT void SSL_CTX_set_tls_channel_id_enabled(SSL_CTX *ctx,
                                                       int enabled);

// SSL_set_tls_channel_id_enabled configures whether `ssl` should enable Channel
// ID as a server.
OPENSSL_EXPORT void SSL_set_tls_channel_id_enabled(SSL *ssl, int enabled);

// SSL_CTX_set1_tls_channel_id configures a TLS client to send a TLS Channel ID
// to compatible servers. `private_key` must be a P-256 EC key. It returns one
// on success and zero on error.
OPENSSL_EXPORT int SSL_CTX_set1_tls_channel_id(SSL_CTX *ctx,
                                               EVP_PKEY *private_key);

// SSL_set1_tls_channel_id configures a TLS client to send a TLS Channel ID to
// compatible servers. `private_key` must be a P-256 EC key. It returns one on
// success and zero on error.
OPENSSL_EXPORT int SSL_set1_tls_channel_id(SSL *ssl, EVP_PKEY *private_key);

// SSL_get_tls_channel_id gets the client's TLS Channel ID from a server `SSL`
// and copies up to the first `max_out` bytes into `out`. The Channel ID
// consists of the client's P-256 public key as an (x,y) pair where each is a
// 32-byte, big-endian field element. It returns 0 if the client didn't offer a
// Channel ID and the length of the complete Channel ID otherwise. This function
// always returns zero if `ssl` is a client.
OPENSSL_EXPORT size_t SSL_get_tls_channel_id(SSL *ssl, uint8_t *out,
                                             size_t max_out);


// DTLS-SRTP.
//
// See RFC 5764.

// srtp_protection_profile_st (aka `SRTP_PROTECTION_PROFILE`) is an SRTP
// profile for use with the use_srtp extension.
struct srtp_protection_profile_st {
  const char *name;
  unsigned long id;
} /* SRTP_PROTECTION_PROFILE */;

DEFINE_CONST_STACK_OF(SRTP_PROTECTION_PROFILE)

// SRTP_* define constants for SRTP profiles.
#define SRTP_AES128_CM_SHA1_80 0x0001
#define SRTP_AES128_CM_SHA1_32 0x0002
#define SRTP_AES128_F8_SHA1_80 0x0003
#define SRTP_AES128_F8_SHA1_32 0x0004
#define SRTP_NULL_SHA1_80 0x0005
#define SRTP_NULL_SHA1_32 0x0006
#define SRTP_AEAD_AES_128_GCM 0x0007
#define SRTP_AEAD_AES_256_GCM 0x0008

// SSL_CTX_set_srtp_profiles enables SRTP for all SSL objects created from
// `ctx`. `profile` contains a colon-separated list of profile names. It returns
// one on success and zero on failure.
OPENSSL_EXPORT int SSL_CTX_set_srtp_profiles(SSL_CTX *ctx,
                                             const char *profiles);

// SSL_set_srtp_profiles enables SRTP for `ssl`.  `profile` contains a
// colon-separated list of profile names. It returns one on success and zero on
// failure.
OPENSSL_EXPORT int SSL_set_srtp_profiles(SSL *ssl, const char *profiles);

// SSL_get_srtp_profiles returns the SRTP profiles supported by `ssl`.
OPENSSL_EXPORT const STACK_OF(SRTP_PROTECTION_PROFILE) *SSL_get_srtp_profiles(
    const SSL *ssl);

// SSL_get_selected_srtp_profile returns the selected SRTP profile, or NULL if
// SRTP was not negotiated.
OPENSSL_EXPORT const SRTP_PROTECTION_PROFILE *SSL_get_selected_srtp_profile(
    SSL *ssl);


// TLS 1.3 pre-shared keys.
//
// TLS 1.3 connections can be authenticated using external pre-shared keys
// (PSKs), as described in RFC 9258. These are represented in BoringSSL with
// `SSL_CREDENTIAL` objects.
//
// BoringSSL only implements the PSK importer interface from RFC 9258. The
// underlying protocol- and cipher-specific TLS 1.3 PSK mechanism is not exposed
// directly.

// SSL_CREDENTIAL_new_pre_shared_key returns a newly-allocated `SSL_CREDENTIAL`
// representing an external pre-shared key, as described in RFC 9258, or NULL on
// error. `key` is the base key, `id` is the external identity, and `md` is the
// hash function. The result may be added to the credential list with
// `SSL_CTX_add1_credential` or `SSL_add1_credential`. `context` is the context
// string to use when importing to TLS.
//
// WARNING: An attacker with knowledge of `key` can impersonate either side of
// the connection. Additionally, using a pre-shared key exposes `key` to offline
// brute force attacks. `key` must thus be a high-entropy, secret value.
// Passwords or short PINs, for example, would not be safe to use as `key`.
//
// Callers can configure the credential list with multiple PSKs, or a mix of
// PSKs and other credentials, in some preference order. Due to protocol
// differences, clients and servers evaluate PSKs in the credential list
// differently:
//
// - As a server, PSK credentials behave similarly to other credentials. Callers
//   can configure them dynamically in the certificate callbacks (see
//   `SSL_CTX_set_select_certificate_cb` and `SSL_CTX_set_cert_cb`). After those
//   callbacks run, BoringSSL will select a credential to use from the list.
//
// - As a client, PSK credentials are offered in the ClientHello and selected by
//   the server. This means all PSK credentials must be configured before
//   starting the handshake, and the order between PSK and non-PSK credentials
//   will be ignored. PSK credentials cannot be configured dynamically in
//   callbacks such as `SSL_CTX_set_cert_cb`.
//
// A single connection may be configured to accept only certificate-based
// handshakes, only PSK-based handshakes, or both. The server credential
// determines the kind of handshake, so this is implicitly controlled by the
// credential list as a server:
//
// - If the credential list only contains PSKs, BoringSSL will only consider
//   PSK-based handshakes.
//
// - If the credential list contains PSKs and certificates, BoringSSL will
//   consider both, depending on the client.
//
// As a client, if any PSK credentials are configured, BoringSSL will only
// accept PSK-based handshakes by default. Setting the verify mode to
// `SSL_VERIFY_PEER` (see `SSL_CTX_set_verify` and `SSL_CTX_set_custom_verify`)
// overrides this behavior and causes BoringSSL to accept either.
//
// In both clients and servers, if a caller configures one or more PSK
// credentials, and calls no certificate-related functions, the connection will
// only accept one of those PSKs.
OPENSSL_EXPORT SSL_CREDENTIAL *SSL_CREDENTIAL_new_pre_shared_key(
    const uint8_t *key, size_t key_len, const uint8_t *id, size_t id_len,
    const EVP_MD *md, const uint8_t *context, size_t context_len);

// SSL_CREDENTIAL_get0_pre_shared_key_id returns the external identity of this
// pre-shared key credential, or NULL if `cred` is not a pre-shared key
// credential or `id_len` is NULL.
OPENSSL_EXPORT const uint8_t *SSL_CREDENTIAL_get0_pre_shared_key_id(
    const SSL_CREDENTIAL *cred, size_t *id_len);


// TLS 1.2 pre-shared keys.
//
// TLS 1.2 connections may be configured with PSK (Pre-Shared Key) cipher
// suites. These authenticate using out-of-band pre-shared keys rather than
// certificates. See RFC 4279.
//
// This implementation uses NUL-terminated C strings for identities and identity
// hints, so values with a NUL character are not supported. (RFC 4279 does not
// specify the format of an identity.)
//
// Functions in this section only relate to PSKs in TLS 1.2 or earlier. New
// PSK-based applications likely do not need this functionality and instead
// should use TLS 1.3. See `SSL_CREDENTIAL_new_pre_shared_key` for TLS 1.3 PSKs.

// PSK_MAX_IDENTITY_LEN is the maximum supported length of a TLS 1.2 PSK
// identity, excluding the NUL terminator.
#define PSK_MAX_IDENTITY_LEN 128

// PSK_MAX_PSK_LEN is the maximum supported length of a TLS 1.2 pre-shared key.
#define PSK_MAX_PSK_LEN 256

// SSL_CTX_set_psk_client_callback sets the callback to be called when TLS 1.2
// PSK is negotiated on the client. This callback must be set to enable PSK
// cipher suites on the client.
//
// The callback is passed the identity hint in `hint` or NULL if none was
// provided. It should select a PSK identity and write the identity and the
// corresponding PSK to `identity` and `psk`, respectively. The identity is
// written as a NUL-terminated C string of length (excluding the NUL terminator)
// at most `max_identity_len`. The PSK's length must be at most `max_psk_len`.
// The callback returns the length of the PSK or 0 if no suitable identity was
// found.
OPENSSL_EXPORT void SSL_CTX_set_psk_client_callback(
    SSL_CTX *ctx, unsigned (*cb)(SSL *ssl, const char *hint, char *identity,
                                 unsigned max_identity_len, uint8_t *psk,
                                 unsigned max_psk_len));

// SSL_set_psk_client_callback sets the callback to be called when TLS 1.2 PSK
// is negotiated on the client. This callback must be set to enable PSK cipher
// suites on the client. See also `SSL_CTX_set_psk_client_callback`.
OPENSSL_EXPORT void SSL_set_psk_client_callback(
    SSL *ssl, unsigned (*cb)(SSL *ssl, const char *hint, char *identity,
                             unsigned max_identity_len, uint8_t *psk,
                             unsigned max_psk_len));

// SSL_CTX_set_psk_server_callback sets the callback to be called when TLS 1.2
// PSK is negotiated on the server. This callback must be set to enable PSK
// cipher suites on the server.
//
// The callback is passed the identity in `identity`. It should write a PSK of
// length at most `max_psk_len` to `psk` and return the number of bytes written
// or zero if the PSK identity is unknown.
OPENSSL_EXPORT void SSL_CTX_set_psk_server_callback(
    SSL_CTX *ctx, unsigned (*cb)(SSL *ssl, const char *identity, uint8_t *psk,
                                 unsigned max_psk_len));

// SSL_set_psk_server_callback sets the callback to be called when TLS 1.2 PSK
// is negotiated on the server. This callback must be set to enable PSK cipher
// suites on the server. See also `SSL_CTX_set_psk_server_callback`.
OPENSSL_EXPORT void SSL_set_psk_server_callback(
    SSL *ssl, unsigned (*cb)(SSL *ssl, const char *identity, uint8_t *psk,
                             unsigned max_psk_len));

// SSL_CTX_use_psk_identity_hint configures server connections to advertise an
// identity hint of `identity_hint`. It returns one on success and zero on
// error.
OPENSSL_EXPORT int SSL_CTX_use_psk_identity_hint(SSL_CTX *ctx,
                                                 const char *identity_hint);

// SSL_use_psk_identity_hint configures server connections to advertise an
// identity hint of `identity_hint`. It returns one on success and zero on
// error.
OPENSSL_EXPORT int SSL_use_psk_identity_hint(SSL *ssl,
                                             const char *identity_hint);

// SSL_get_psk_identity_hint returns the TLS 1.2 PSK identity hint advertised
// for `ssl` or NULL if there is none.
OPENSSL_EXPORT const char *SSL_get_psk_identity_hint(const SSL *ssl);

// SSL_get_psk_identity, after the handshake completes, returns the TLS 1.2 PSK
// identity that was negotiated by `ssl` or NULL if PSK was not used.
OPENSSL_EXPORT const char *SSL_get_psk_identity(const SSL *ssl);


// Delegated credentials.
//
// Delegated credentials (RFC 9345) allow a TLS 1.3 endpoint to use its
// certificate to issue new credentials for authentication. Once issued,
// credentials can't be revoked. In order to mitigate the damage in case the
// credential secret key is compromised, the credential is only valid for a
// short time (days, hours, or even minutes).
//
// Currently only the authenticating side, as a server, is implemented. To
// authenticate with delegated credentials, construct an `SSL_CREDENTIAL` with
// `SSL_CREDENTIAL_new_delegated` and add it to the credential list. See also
// `SSL_CTX_add1_credential`. Callers may configure a mix of delegated
// credentials and X.509 credentials on the same `SSL` or `SSL_CTX` to support a
// range of clients.

// SSL_CREDENTIAL_new_delegated returns a new, empty delegated credential, or
// NULL on error. Callers should release the result with `SSL_CREDENTIAL_free`
// when done.
//
// Callers should configure a delegated credential, certificate chain and
// private key on the credential, along with other properties, then add it with
// `SSL_CTX_add1_credential`.
OPENSSL_EXPORT SSL_CREDENTIAL *SSL_CREDENTIAL_new_delegated(void);

// SSL_CREDENTIAL_set1_delegated_credential sets `cred`'s delegated credentials
// structure to `dc`. It returns one on success and zero on error, including if
// `dc` is malformed. This should be a DelegatedCredential structure, signed by
// the end-entity certificate, as described in RFC 9345.
OPENSSL_EXPORT int SSL_CREDENTIAL_set1_delegated_credential(
    SSL_CREDENTIAL *cred, CRYPTO_BUFFER *dc);


// Raw Public Keys (RFC 7250).
//
// Raw public keys can be used (e.g., instead of X.509 certificates) to
// authenticate a TLS connection, assuming an out-of-band mechanism has been
// used to bind the public keys to their presenting entities.
//
// A caller wishing to authenticate using a raw public key must construct an
// `SSL_CREDENTIAL` with `SSL_CREDENTIAL_new_raw_public_key` and add it to the
// credential list (see `SSL_CTX_add1_credential`). Callers may configure a mix
// of raw public keys and other credentials on the same `SSL` or `SSL_CTX` to
// support a range of peers.
//
// When raw public keys are in use, the client_certificate_type and
// server_certificate_type extensions are sent in the handshake to indicate to
// the peer which type(s) of certificate(s) can be exchanged.
//
// To verify a received raw public key, the caller must set a custom
// verification callback (see `SSL_CTX_set_custom_verify`). If no callback is
// configured, raw public keys will be rejected by default.

// TLSEXT_cert_type_* are certificate types with values taken from the "TLS
// Certificate Types" subregistry of the TLS Extensions registry.
#define TLSEXT_cert_type_x509 0x00
#define TLSEXT_cert_type_rpk 0x02

// SSL_CREDENTIAL_new_raw_public_key returns a new raw public key credential
// using `pkey` as the public and private key, or nullptr on error. `pkey` must
// have both a private and public key.
//
// Callers should then add the returned credential with
// `SSL_CTX_add1_credential` and release it with `SSL_CREDENTIAL_free` when
// done.
//
// This credential may be configured before the handshake or dynamically in the
// early callback (see `SSL_CTX_set_select_certificate_cb`) and certificate
// callback (see `SSL_CTX_set_cert_cb`).
OPENSSL_EXPORT SSL_CREDENTIAL *SSL_CREDENTIAL_new_raw_public_key(
    EVP_PKEY *pkey);

// SSL_CREDENTIAL_new_raw_public_key_custom returns a new raw public key
// credential using `pubkey` as the public key and `method` as the custom
// private key method, or nullptr on error. `pkey` must have a public key.
// `method` must remain valid for the lifetime of the returned credential. See
// `SSL_CREDENTIAL_set_private_key_method` for how the custom private key method
// is used.
//
// Callers should then add the returned credential with
// `SSL_CTX_add1_credential` and release it with `SSL_CREDENTIAL_free` when
// done.
//
// This credential may be configured before the handshake or dynamically in the
// early callback (see `SSL_CTX_set_select_certificate_cb`) and certificate
// callback (see `SSL_CTX_set_cert_cb`).
OPENSSL_EXPORT SSL_CREDENTIAL *SSL_CREDENTIAL_new_raw_public_key_custom(
    EVP_PKEY *pubkey, const SSL_PRIVATE_KEY_METHOD *method);

// SSL_CTX_set1_accepted_peer_cert_types sets the types of certificates that the
// caller wishes to accept from the peer, for `ctx`. `values` is a nonempty list
// of `num_values` certificate types (`TLSEXT_cert_type_*` values) in preference
// order. If a valid list is not configured explicitly, only X.509 certificates
// are accepted by default. This function returns one on success or zero on
// failure.
OPENSSL_EXPORT int SSL_CTX_set1_accepted_peer_cert_types(SSL_CTX *ctx,
                                                         const uint8_t *values,
                                                         size_t num_values);

// SSL_set1_accepted_peer_cert_types behaves like
// `SSL_CTX_set1_accepted_peer_cert_types`, but configures the values on `ssl`.
OPENSSL_EXPORT int SSL_set1_accepted_peer_cert_types(SSL *ssl,
                                                     const uint8_t *values,
                                                     size_t num_values);

// SSL_CTX_set1_available_client_cert_types sets the types of certificates that
// the caller, as a client, wishes to advertise in order to authenticate itself
// to the server, for `ctx`. `values` is a nonempty list of `num_values`
// certificate types (`TLSEXT_cert_type_*` values) in preference order. Any
// values configured via this function will be sent in the
// client_certificate_type extension in ClientHello. `values` may be empty to
// indicate omission of the client_certificate_extension.
//
// Calling this function is optional: by default, the client_certificate_type
// extension for a client will be determined implicitly by the types of
// `SSL_CREDENTIAL`s present in the credential list. This function should only
// be used if the caller configures client credentials late (after the handshake
// begins), or wishes to override the default order derived from the credential
// list. This returns one on success or zero on failure.
OPENSSL_EXPORT int SSL_CTX_set1_available_client_cert_types(
    SSL_CTX *ctx, const uint8_t *values, size_t num_values);

// SSL_set1_available_client_cert_types behaves like
// `SSL_CTX_set1_available_client_cert_types`, but configures the values on
// `ssl`.
OPENSSL_EXPORT int SSL_set1_available_client_cert_types(SSL *ssl,
                                                        const uint8_t *values,
                                                        size_t num_values);

// SSL_get_peer_cert_type returns a `TLSEXT_cert_type_*` value describing the
// type of the peer's certificate.  If the peer has no certificate, or it is too
// early in the handshake to receive one, this function returns
// `TLSEXT_cert_type_x509`.
OPENSSL_EXPORT int SSL_get_peer_cert_type(const SSL *ssl);

// SSL_get0_peer_rpk returns the peer's raw public key from `ssl`, if the peer
// has sent one in the handshake. It returns nullptr otherwise.
OPENSSL_EXPORT EVP_PKEY *SSL_get0_peer_rpk(const SSL *ssl);


// Password Authenticated Key Exchange (PAKE).
//
// Password Authenticated Key Exchange protocols allow client and server to
// mutually authenticate one another using knowledge of a password or other
// low-entropy secret. While the TLS 1.3 pre-shared key (PSK) mechanism can
// authenticate a high-entropy secret, it cannot be used with low-entropy
// secrets as the PSK binder values can be used to mount a dictionary attack on
// a low-entropy PSK. Using TLS 1.3 with a PAKE limits an attacker to confirming
// one password guess per handshake attempt.
//
// WARNING: The PAKE mode in TLS is not a general-purpose authentication scheme.
// As the underlying secret is still low-entropy, callers must limit brute force
// attacks across multiple connections, especially in multi-connection protocols
// such as HTTP. The `error_limit` and `rate_limit` parameters in the functions
// below may be used to implement this, provided the same `SSL_CREDENTIAL`
// object is used across connections. Applications using multiple connections
// should use the PAKE credential only once to authenticate a high-entropy
// secret. For example, an application may export a PSK from a PAKE connection
// with `SSL_export_keying_material`, and then pass the result to
// `SSL_CREDENTIAL_new_pre_shared_key` to authenticate subsequent connections.
//
// WARNING: PAKE support in TLS is still experimental and may change as the
// standard evolves. See
// https://chris-wood.github.io/draft-bmw-tls-pake13/draft-bmw-tls-pake13.html
//
// Currently, only the SPAKE2PLUS_V1 named PAKE algorithm is implemented; see
// https://chris-wood.github.io/draft-bmw-tls-pake13/draft-bmw-tls-pake13.html#section-8.1.

// SSL_PAKE_SPAKE2PLUSV1 is the codepoint for SPAKE2PLUS_V1. See
// https://chris-wood.github.io/draft-bmw-tls-pake13/draft-bmw-tls-pake13.html#name-named-pake-registry.
#define SSL_PAKE_SPAKE2PLUSV1 0x7d96

// SSL_spake2plusv1_register computes the values that the client (w0,
// w1) and server (w0, registration_record) require to run SPAKE2+. These values
// can be used when calling `SSL_CREDENTIAL_new_spake2plusv1_client` and
// `SSL_CREDENTIAL_new_spake2plusv1_server`. The client and server identities
// must match the values passed to those functions.
//
// Returns one on success and zero on error.
OPENSSL_EXPORT int SSL_spake2plusv1_register(
    uint8_t out_w0[32], uint8_t out_w1[32], uint8_t out_registration_record[65],
    const uint8_t *password, size_t password_len,
    const uint8_t *client_identity, size_t client_identity_len,
    const uint8_t *server_identity, size_t server_identity_len);

// SSL_CREDENTIAL_new_spake2plusv1_client creates a new `SSL_CREDENTIAL` that
// authenticates using SPAKE2+. It is to be used with a TLS client.
//
// The `context`, `client_identity`, and `server_identity` fields serve to
// identity the SPAKE2+ settings and both sides of a connection must agree on
// these values. If `context` is `NULL`, a default value will be used.
//
// `error_limit` is the number of failed handshakes allowed on the credential.
// After the limit is reached, using the credential will fail. Ideally this
// value is set to 1. Setting it to a higher value allows an attacker to have
// that many attempts at guessing the password using this `SSL_CREDENTIAL`.
// (Assuming that multiple TLS connections are allowed.)
//
// `w0` and `w1` come from calling `SSL_spake2plusv1_register`.
//
// Unlike most `SSL_CREDENTIAL`s, PAKE client credentials must be the only
// credential configured on the connection. BoringSSL does not currently support
// configuring multiple PAKE credentials as a client, or configuring a mix of
// PAKE and non-PAKE credentials. Once a PAKE credential is configured, the
// connection will require the server to authenticate with the same secret, so a
// successful connection then implies that the server supported the PAKE and
// knew the password.
OPENSSL_EXPORT SSL_CREDENTIAL *SSL_CREDENTIAL_new_spake2plusv1_client(
    const uint8_t *context, size_t context_len, const uint8_t *client_identity,
    size_t client_identity_len, const uint8_t *server_identity,
    size_t server_identity_len, uint32_t error_limit, const uint8_t *w0,
    size_t w0_len, const uint8_t *w1, size_t w1_len);

// SSL_CREDENTIAL_new_spake2plusv1_server creates a new `SSL_CREDENTIAL` that
// authenticates using SPAKE2+. It is to be used with a TLS server.
//
// The `context`, `client_identity`, and `server_identity` fields serve to
// identity the SPAKE2+ settings and both sides of a connection must agree on
// these values. If `context` is `NULL`, a default value will be used.
//
// `rate_limit` is the number of failed or unfinished handshakes allowed on the
// credential. After the limit is reached, using the credential will fail.
// Ideally this value is set to 1. Setting it to a higher value allows an
// attacker to have that many attempts at guessing the password using this
// `SSL_CREDENTIAL`. (Assuming that multiple TLS connections are allowed.)
//
// WARNING: `rate_limit` differs from the client's `error_limit` parameter.
// Server PAKE credentials must temporarily deduct incomplete handshakes from
// the limit, until the peer completes the handshake correctly. Thus
// applications that use multiple connections in parallel may need a higher
// limit, and thus higher attacker exposure, to avoid failures. Such
// applications should instead use one PAKE-based connection to established a
// high-entropy secret (e.g. with `SSL_export_keying_material`) instead of
// repeating the PAKE exchange for each connection.
//
// `w0` and `registration_record` come from calling `SSL_spake2plusv1_register`,
// which may be computed externally so that the server does not know the
// password, or a password-equivalent secret.
//
// A server wishing to support a PAKE should install one of these credentials.
// It is also possible to install certificate-based credentials, in which case
// both PAKE and non-PAKE clients can be supported. However, if only a PAKE
// credential is installed then the server knows that any successfully-connected
// clients also knows the password. Otherwise, the server must be careful to
// inspect the credential used for a connection before assuming that.
OPENSSL_EXPORT SSL_CREDENTIAL *SSL_CREDENTIAL_new_spake2plusv1_server(
    const uint8_t *context, size_t context_len, const uint8_t *client_identity,
    size_t client_identity_len, const uint8_t *server_identity,
    size_t server_identity_len, uint32_t rate_limit, const uint8_t *w0,
    size_t w0_len, const uint8_t *registration_record,
    size_t registration_record_len);


// QUIC integration.
//
// QUIC acts as an underlying transport for the TLS 1.3 handshake. The following
// functions allow a QUIC implementation to serve as the underlying transport as
// described in RFC 9001.
//
// When configured for QUIC, `SSL_do_handshake` will drive the handshake as
// before, but it will not use the configured `BIO`. It will call functions on
// `SSL_QUIC_METHOD` to configure secrets and send data. If data is needed from
// the peer, it will return `SSL_ERROR_WANT_READ`. As the caller receives data
// it can decrypt, it calls `SSL_provide_quic_data`. Subsequent
// `SSL_do_handshake` calls will then consume that data and progress the
// handshake. After the handshake is complete, the caller should continue to
// call `SSL_provide_quic_data` for any post-handshake data, followed by
// `SSL_process_quic_post_handshake` to process it. It is an error to call
// `SSL_read` and `SSL_write` in QUIC.
//
// 0-RTT behaves similarly to `TLS_method`'s usual behavior. `SSL_do_handshake`
// returns early as soon as the client (respectively, server) is allowed to send
// 0-RTT (respectively, half-RTT) data. The caller should then call
// `SSL_do_handshake` again to consume the remaining handshake messages and
// confirm the handshake. As a client, `SSL_ERROR_EARLY_DATA_REJECTED` and
// `SSL_reset_early_data_reject` behave as usual.
//
// See https://www.rfc-editor.org/rfc/rfc9001.html#section-4.1 for more details.
//
// To avoid DoS attacks, the QUIC implementation must limit the amount of data
// being queued up. The implementation can call
// `SSL_quic_max_handshake_flight_len` to get the maximum buffer length at each
// encryption level.
//
// QUIC implementations must additionally configure transport parameters with
// `SSL_set_quic_transport_params`. `SSL_get_peer_quic_transport_params` may be
// used to query the value received from the peer. BoringSSL handles this
// extension as an opaque byte string. The caller is responsible for serializing
// and parsing them. See https://www.rfc-editor.org/rfc/rfc9000#section-7.4 for
// details.
//
// QUIC additionally imposes restrictions on 0-RTT. In particular, the QUIC
// transport layer requires that if a server accepts 0-RTT data, then the
// transport parameters sent on the resumed connection must not lower any limits
// compared to the transport parameters that the server sent on the connection
// where the ticket for 0-RTT was issued. In effect, the server must remember
// the transport parameters with the ticket. Application protocols running on
// QUIC may impose similar restrictions, for example HTTP/3's restrictions on
// SETTINGS frames.
//
// BoringSSL implements this check by doing a byte-for-byte comparison of an
// opaque context passed in by the server. This context must be the same on the
// connection where the ticket was issued and the connection where that ticket
// is used for 0-RTT. If there is a mismatch, or the context was not set,
// BoringSSL will reject early data (but not reject the resumption attempt).
// This context is set via `SSL_set_quic_early_data_context` and should cover
// both transport parameters and any application state.
// `SSL_set_quic_early_data_context` must be called on the server with a
// non-empty context if the server is to support 0-RTT in QUIC.
//
// BoringSSL does not perform any client-side checks on the transport
// parameters received from a server that also accepted early data. It is up to
// the caller to verify that the received transport parameters do not lower any
// limits, and to close the QUIC connection if that is not the case. The same
// holds for any application protocol state remembered for 0-RTT, e.g. HTTP/3
// SETTINGS.

// ssl_encryption_level_t represents an encryption level in TLS 1.3. Values in
// this enum match the first 4 epochs used in DTLS 1.3 (section 6.1).
enum ssl_encryption_level_t BORINGSSL_ENUM_INT {
  ssl_encryption_initial = 0,
  ssl_encryption_early_data = 1,
  ssl_encryption_handshake = 2,
  ssl_encryption_application = 3,
};

// ssl_quic_method_st (aka `SSL_QUIC_METHOD`) describes custom QUIC hooks.
struct ssl_quic_method_st {
  // set_read_secret configures the read secret and cipher suite for the given
  // encryption level. It returns one on success and zero to terminate the
  // handshake with an error. It will be called at most once per encryption
  // level.
  //
  // BoringSSL will not release read keys before QUIC may use them. Once a level
  // has been initialized, QUIC may begin processing data from it. Handshake
  // data should be passed to `SSL_provide_quic_data` and application data (if
  // `level` is `ssl_encryption_early_data` or `ssl_encryption_application`) may
  // be processed according to the rules of the QUIC protocol.
  //
  // QUIC ACKs packets at the same encryption level they were received at,
  // except that client `ssl_encryption_early_data` (0-RTT) packets trigger
  // server `ssl_encryption_application` (1-RTT) ACKs. BoringSSL will always
  // install ACK-writing keys with `set_write_secret` before the packet-reading
  // keys with `set_read_secret`. This ensures the caller can always ACK any
  // packet it decrypts. Note this means the server installs 1-RTT write keys
  // before 0-RTT read keys.
  //
  // The converse is not true. An encryption level may be configured with write
  // secrets a roundtrip before the corresponding secrets for reading ACKs is
  // available.
  int (*set_read_secret)(SSL *ssl, enum ssl_encryption_level_t level,
                         const SSL_CIPHER *cipher, const uint8_t *secret,
                         size_t secret_len);
  // set_write_secret behaves like `set_read_secret` but configures the write
  // secret and cipher suite for the given encryption level. It will be called
  // at most once per encryption level.
  //
  // BoringSSL will not release write keys before QUIC may use them. If `level`
  // is `ssl_encryption_early_data` or `ssl_encryption_application`, QUIC may
  // begin sending application data at `level`. However, note that BoringSSL
  // configures server `ssl_encryption_application` write keys before the client
  // Finished. This allows QUIC to send half-RTT data, but the handshake is not
  // confirmed at this point and, if requesting client certificates, the client
  // is not yet authenticated.
  //
  // See `set_read_secret` for additional invariants between packets and their
  // ACKs.
  //
  // Note that, on 0-RTT reject, the `ssl_encryption_early_data` write secret
  // may use a different cipher suite from the other keys.
  int (*set_write_secret)(SSL *ssl, enum ssl_encryption_level_t level,
                          const SSL_CIPHER *cipher, const uint8_t *secret,
                          size_t secret_len);
  // add_handshake_data adds handshake data to the current flight at the given
  // encryption level. It returns one on success and zero on error.
  //
  // BoringSSL will pack data from a single encryption level together, but a
  // single handshake flight may include multiple encryption levels. Callers
  // should defer writing data to the network until `flush_flight` to better
  // pack QUIC packets into transport datagrams.
  //
  // If `level` is not `ssl_encryption_initial`, this function will not be
  // called before `level` is initialized with `set_write_secret`.
  int (*add_handshake_data)(SSL *ssl, enum ssl_encryption_level_t level,
                            const uint8_t *data, size_t len);
  // flush_flight is called when the current flight is complete and should be
  // written to the transport. Note a flight may contain data at several
  // encryption levels. It returns one on success and zero on error.
  int (*flush_flight)(SSL *ssl);
  // send_alert sends a fatal alert at the specified encryption level. It
  // returns one on success and zero on error.
  //
  // If `level` is not `ssl_encryption_initial`, this function will not be
  // called before `level` is initialized with `set_write_secret`.
  int (*send_alert)(SSL *ssl, enum ssl_encryption_level_t level, uint8_t alert);
};

// SSL_quic_max_handshake_flight_len returns the maximum number of bytes
// that may be received at the given encryption level. This function should be
// used to limit buffering in the QUIC implementation.
//
// See https://www.rfc-editor.org/rfc/rfc9000#section-7.5
OPENSSL_EXPORT size_t SSL_quic_max_handshake_flight_len(
    const SSL *ssl, enum ssl_encryption_level_t level);

// SSL_quic_read_level returns the current read encryption level.
//
// TODO(davidben): Is it still necessary to expose this function to callers?
// QUICHE does not use it.
OPENSSL_EXPORT enum ssl_encryption_level_t SSL_quic_read_level(const SSL *ssl);

// SSL_quic_write_level returns the current write encryption level.
//
// TODO(davidben): Is it still necessary to expose this function to callers?
// QUICHE does not use it.
OPENSSL_EXPORT enum ssl_encryption_level_t SSL_quic_write_level(const SSL *ssl);

// SSL_provide_quic_data provides data from QUIC at a particular encryption
// level `level`. It returns one on success and zero on error. Note this
// function will return zero if the handshake is not expecting data from `level`
// at this time. The QUIC implementation should then close the connection with
// an error.
OPENSSL_EXPORT int SSL_provide_quic_data(SSL *ssl,
                                         enum ssl_encryption_level_t level,
                                         const uint8_t *data, size_t len);


// SSL_process_quic_post_handshake processes any data that QUIC has provided
// after the handshake has completed. This includes NewSessionTicket messages
// sent by the server. It returns one on success and zero on error.
OPENSSL_EXPORT int SSL_process_quic_post_handshake(SSL *ssl);

// SSL_CTX_set_quic_method configures the QUIC hooks. This should only be
// configured with a minimum version of TLS 1.3. `quic_method` must remain valid
// for the lifetime of `ctx`. It returns one on success and zero on error.
OPENSSL_EXPORT int SSL_CTX_set_quic_method(SSL_CTX *ctx,
                                           const SSL_QUIC_METHOD *quic_method);

// SSL_set_quic_method configures the QUIC hooks. This should only be
// configured with a minimum version of TLS 1.3. `quic_method` must remain valid
// for the lifetime of `ssl`. It returns one on success and zero on error.
OPENSSL_EXPORT int SSL_set_quic_method(SSL *ssl,
                                       const SSL_QUIC_METHOD *quic_method);

// SSL_set_quic_transport_params configures `ssl` to send `params` (of length
// `params_len`) in the quic_transport_parameters extension in either the
// ClientHello or EncryptedExtensions handshake message. It is an error to set
// transport parameters if `ssl` is not configured for QUIC. The buffer pointed
// to by `params` only need be valid for the duration of the call to this
// function. This function returns 1 on success and 0 on failure.
OPENSSL_EXPORT int SSL_set_quic_transport_params(SSL *ssl,
                                                 const uint8_t *params,
                                                 size_t params_len);

// SSL_get_peer_quic_transport_params provides the caller with the value of the
// quic_transport_parameters extension sent by the peer. A pointer to the buffer
// containing the TransportParameters will be put in `*out_params`, and its
// length in `*params_len`. This buffer will be valid for the lifetime of the
// `SSL`. If no params were received from the peer, `*out_params_len` will be 0.
OPENSSL_EXPORT void SSL_get_peer_quic_transport_params(
    const SSL *ssl, const uint8_t **out_params, size_t *out_params_len);

// SSL_set_quic_use_legacy_codepoint configures whether to use the legacy QUIC
// extension codepoint 0xffa5 as opposed to the official value 57. Call with
// `use_legacy` set to 1 to use 0xffa5 and call with 0 to use 57. By default,
// the standard code point is used.
OPENSSL_EXPORT void SSL_set_quic_use_legacy_codepoint(SSL *ssl, int use_legacy);

// SSL_set_quic_early_data_context configures a context string in QUIC servers
// for accepting early data. If a resumption connection offers early data, the
// server will check if the value matches that of the connection which minted
// the ticket. If not, resumption still succeeds but early data is rejected.
// This should include all QUIC Transport Parameters except ones specified that
// the client MUST NOT remember. This should also include any application
// protocol-specific state. For HTTP/3, this should be the serialized server
// SETTINGS frame and the QUIC Transport Parameters (except the stateless reset
// token).
//
// This function may be called before `SSL_do_handshake` or during server
// certificate selection. It returns 1 on success and 0 on failure.
OPENSSL_EXPORT int SSL_set_quic_early_data_context(SSL *ssl,
                                                   const uint8_t *context,
                                                   size_t context_len);


// Early data.
//
// WARNING: 0-RTT support in BoringSSL is currently experimental and not fully
// implemented. It may cause interoperability or security failures when used.
//
// Early data, or 0-RTT, is a feature in TLS 1.3 which allows clients to send
// data on the first flight during a resumption handshake. This can save a
// round-trip in some application protocols.
//
// WARNING: A 0-RTT handshake has different security properties from normal
// handshake, so it is off by default unless opted in. In particular, early data
// is replayable by a network attacker. Callers must account for this when
// sending or processing data before the handshake is confirmed. See RFC 8446
// for more information.
//
// As a server, if early data is accepted, `SSL_do_handshake` will complete as
// soon as the ClientHello is processed and server flight sent. `SSL_write` may
// be used to send half-RTT data. `SSL_read` will consume early data and
// transition to 1-RTT data as appropriate. Prior to the transition,
// `SSL_in_init` will report the handshake is still in progress. Callers may use
// it or `SSL_in_early_data` to defer or reject requests as needed.
//
// Early data as a client is more complex. If the offered session (see
// `SSL_set_session`) is 0-RTT-capable, the handshake will return after sending
// the ClientHello. The predicted peer certificates and ALPN protocol will be
// available via the usual APIs. `SSL_write` will write early data, up to the
// session's limit. Writes past this limit and `SSL_read` will complete the
// handshake before continuing. Callers may also call `SSL_do_handshake` again
// to complete the handshake sooner.
//
// If the server accepts early data, the handshake will succeed. `SSL_read` and
// `SSL_write` will then act as in a 1-RTT handshake. The peer certificates and
// ALPN protocol will be as predicted and need not be re-queried.
//
// If the server rejects early data, `SSL_do_handshake` (and thus `SSL_read` and
// `SSL_write`) will then fail with `SSL_get_error` returning
// `SSL_ERROR_EARLY_DATA_REJECTED`. The caller should treat this as a connection
// error and most likely perform a high-level retry. Note the server may still
// have processed the early data due to attacker replays.
//
// To then continue the handshake on the original connection, use
// `SSL_reset_early_data_reject`. The connection will then behave as one which
// had not yet completed the handshake. This allows a faster retry than making a
// fresh connection. `SSL_do_handshake` will complete the full handshake,
// possibly resulting in different peer certificates, ALPN protocol, and other
// properties. The caller must disregard any values from before the reset and
// query again.
//
// Finally, to implement the fallback described in RFC 8446 appendix D.3, retry
// on a fresh connection without 0-RTT if the handshake fails with
// `SSL_R_WRONG_VERSION_ON_EARLY_DATA`.

// SSL_CTX_set_early_data_enabled sets whether early data is allowed to be used
// with resumptions using `ctx`.
OPENSSL_EXPORT void SSL_CTX_set_early_data_enabled(SSL_CTX *ctx, int enabled);

// SSL_set_early_data_enabled sets whether early data is allowed to be used
// with resumptions using `ssl`. See `SSL_CTX_set_early_data_enabled` for more
// information.
OPENSSL_EXPORT void SSL_set_early_data_enabled(SSL *ssl, int enabled);

// SSL_in_early_data returns one if `ssl` has a pending handshake that has
// progressed enough to send or receive early data. Clients may call `SSL_write`
// to send early data, but `SSL_read` will complete the handshake before
// accepting application data. Servers may call `SSL_read` to read early data
// and `SSL_write` to send half-RTT data.
OPENSSL_EXPORT int SSL_in_early_data(const SSL *ssl);

// SSL_SESSION_early_data_capable returns whether early data would have been
// attempted with `session` if enabled.
OPENSSL_EXPORT int SSL_SESSION_early_data_capable(const SSL_SESSION *session);

// SSL_SESSION_copy_without_early_data returns a copy of `session` with early
// data disabled. If `session` already does not support early data, it returns
// `session` with the reference count increased. The caller takes ownership of
// the result and must release it with `SSL_SESSION_free`.
//
// This function may be used on the client to clear early data support from
// existing sessions when the server rejects early data. In particular,
// `SSL_R_WRONG_VERSION_ON_EARLY_DATA` requires a fresh connection to retry, and
// the client would not want 0-RTT enabled for the next connection attempt.
OPENSSL_EXPORT SSL_SESSION *SSL_SESSION_copy_without_early_data(
    SSL_SESSION *session);

// SSL_early_data_accepted returns whether early data was accepted on the
// handshake performed by `ssl`.
OPENSSL_EXPORT int SSL_early_data_accepted(const SSL *ssl);

// SSL_reset_early_data_reject resets `ssl` after an early data reject. All
// 0-RTT state is discarded, including any pending `SSL_write` calls. The caller
// should treat `ssl` as a logically fresh connection, usually by driving the
// handshake to completion using `SSL_do_handshake`.
//
// It is an error to call this function on an `SSL` object that is not signaling
// `SSL_ERROR_EARLY_DATA_REJECTED`.
OPENSSL_EXPORT void SSL_reset_early_data_reject(SSL *ssl);

// SSL_get_ticket_age_skew returns the difference, in seconds, between the
// client-sent ticket age and the server-computed value in TLS 1.3 server
// connections which resumed a session.
OPENSSL_EXPORT int32_t SSL_get_ticket_age_skew(const SSL *ssl);

// An ssl_early_data_reason_t describes why 0-RTT was accepted or rejected.
// These values are persisted to logs. Entries should not be renumbered and
// numeric values should never be reused.
enum ssl_early_data_reason_t BORINGSSL_ENUM_INT {
  // The handshake has not progressed far enough for the 0-RTT status to be
  // known.
  ssl_early_data_unknown = 0,
  // 0-RTT is disabled for this connection.
  ssl_early_data_disabled = 1,
  // 0-RTT was accepted.
  ssl_early_data_accepted = 2,
  // The negotiated protocol version does not support 0-RTT.
  ssl_early_data_protocol_version = 3,
  // The peer declined to offer or accept 0-RTT for an unknown reason.
  ssl_early_data_peer_declined = 4,
  // The client did not offer a session.
  ssl_early_data_no_session_offered = 5,
  // The server declined to resume the session.
  ssl_early_data_session_not_resumed = 6,
  // The session does not support 0-RTT.
  ssl_early_data_unsupported_for_session = 7,
  // The server sent a HelloRetryRequest.
  ssl_early_data_hello_retry_request = 8,
  // The negotiated ALPN protocol did not match the session.
  ssl_early_data_alpn_mismatch = 9,
  // The connection negotiated Channel ID, which is incompatible with 0-RTT.
  ssl_early_data_channel_id = 10,
  // Value 11 is reserved. (It has historically `ssl_early_data_token_binding`.)
  // The client and server ticket age were too far apart.
  ssl_early_data_ticket_age_skew = 12,
  // QUIC parameters differ between this connection and the original.
  ssl_early_data_quic_parameter_mismatch = 13,
  // The application settings did not match the session.
  ssl_early_data_alps_mismatch = 14,
  // The value of the largest entry.
  ssl_early_data_reason_max_value = ssl_early_data_alps_mismatch,
};

// SSL_get_early_data_reason returns details why 0-RTT was accepted or rejected
// on `ssl`. This is primarily useful on the server.
OPENSSL_EXPORT enum ssl_early_data_reason_t SSL_get_early_data_reason(
    const SSL *ssl);

// SSL_early_data_reason_string returns a string representation for `reason`, or
// NULL if `reason` is unknown. This function may be used for logging.
// This string is always ASCII-encoded.
OPENSSL_EXPORT const char *SSL_early_data_reason_string(
    enum ssl_early_data_reason_t reason);


// Encrypted ClientHello.
//
// ECH is a mechanism for encrypting the entire ClientHello message in TLS 1.3.
// This can prevent observers from seeing cleartext information about the
// connection, such as the server_name extension.
//
// By default, BoringSSL will treat the server name, session ticket, and client
// certificate as secret, but most other parameters, such as the ALPN protocol
// list will be treated as public and sent in the cleartext ClientHello. Other
// APIs may be added for applications with different secrecy requirements.
//
// ECH support in BoringSSL is still experimental and under development.
//
// See RFC 9849.

// SSL_set_enable_ech_grease configures whether the client will send a GREASE
// ECH extension when no supported ECHConfig is available.
OPENSSL_EXPORT void SSL_set_enable_ech_grease(SSL *ssl, int enable);

// SSL_set_reject_unusable_ech_config configures whether the client will fail
// the handshake if a valid, supported ECHConfig cannot be selected to offer
// ECH.
OPENSSL_EXPORT void SSL_set_reject_unusable_ech_config(SSL *ssl, int enable);

// SSL_set1_ech_config_list configures `ssl` to, as a client, offer ECH with the
// specified configuration. `ech_config_list` should contain a serialized
// ECHConfigList structure. It returns one on success and zero on error.
//
// This function returns an error if the input is malformed. If the input is
// valid but none of the ECHConfigs implement supported parameters, it will
// return success and proceed without ECH.
//
// If a supported ECHConfig is found, `ssl` will encrypt the true ClientHello
// parameters. If the server cannot decrypt it, e.g. due to a key mismatch, ECH
// has a recovery flow. `ssl` will handshake using the cleartext parameters,
// including a public name in the ECHConfig. If using
// `SSL_CTX_set_custom_verify`, callers should use `SSL_get0_ech_name_override`
// to verify the certificate with the public name. If using the built-in
// verifier, the `X509_STORE_CTX` will be configured automatically.
//
// If no other errors are found in this handshake, it will fail with
// `SSL_R_ECH_REJECTED`. Since it didn't use the true parameters, the connection
// cannot be used for application data. Instead, callers should handle this
// error by calling `SSL_get0_ech_retry_configs` and retrying the connection
// with updated ECH parameters. If the retry also fails with
// `SSL_R_ECH_REJECTED`, the caller should report a connection failure.
OPENSSL_EXPORT int SSL_set1_ech_config_list(SSL *ssl,
                                            const uint8_t *ech_config_list,
                                            size_t ech_config_list_len);

// SSL_get0_ech_name_override, if `ssl` is a client and the server rejected ECH,
// sets `*out_name` and `*out_name_len` to point to a buffer containing the ECH
// public name. Otherwise, the buffer will be empty.
//
// When offering ECH as a client, this function should be called during the
// certificate verification callback (see `SSL_CTX_set_custom_verify`). If
// `*out_name_len` is non-zero, the caller should verify the certificate against
// the result, interpreted as a DNS name, rather than the true server name. In
// this case, the handshake will never succeed and is only used to authenticate
// retry configs. See also `SSL_get0_ech_retry_configs`.
OPENSSL_EXPORT void SSL_get0_ech_name_override(const SSL *ssl,
                                               const char **out_name,
                                               size_t *out_name_len);

// SSL_get0_ech_retry_configs sets `*out_retry_configs` and
// `*out_retry_configs_len` to a buffer containing a serialized ECHConfigList.
// If the server did not provide an ECHConfigList, `*out_retry_configs_len` will
// be zero.
//
// When handling an `SSL_R_ECH_REJECTED` error code as a client, callers should
// use this function to recover from potential key mismatches. If the result is
// non-empty, the caller should retry the connection, passing this buffer to
// `SSL_set1_ech_config_list`. If the result is empty, the server has rolled
// back ECH support, and the caller should retry without ECH.
//
// This function must only be called in response to an `SSL_R_ECH_REJECTED`
// error code. Calling this function on `ssl`s that have not authenticated the
// rejection handshake will assert in debug builds and otherwise return an
// unparsable list.
OPENSSL_EXPORT void SSL_get0_ech_retry_configs(
    const SSL *ssl, const uint8_t **out_retry_configs,
    size_t *out_retry_configs_len);

// SSL_marshal_ech_config constructs a new serialized ECHConfig. On success, it
// sets `*out` to a newly-allocated buffer containing the result and `*out_len`
// to the size of the buffer. The caller must call `OPENSSL_free` on `*out` to
// release the memory. On failure, it returns zero.
//
// The `config_id` field is a single byte identifier for the ECHConfig. Reusing
// config IDs is allowed, but if multiple ECHConfigs with the same config ID are
// active at a time, server load may increase. See
// `SSL_ECH_KEYS_has_duplicate_config_id`.
//
// The public key and KEM algorithm are taken from `key`. `public_name` is the
// DNS name used to authenticate the recovery flow. `max_name_len` should be the
// length of the longest name in the ECHConfig's anonymity set and influences
// client padding decisions.
OPENSSL_EXPORT int SSL_marshal_ech_config(uint8_t **out, size_t *out_len,
                                          uint8_t config_id,
                                          const EVP_HPKE_KEY *key,
                                          const char *public_name,
                                          size_t max_name_len);

// SSL_ECH_KEYS_new returns a newly-allocated `SSL_ECH_KEYS` or NULL on error.
OPENSSL_EXPORT SSL_ECH_KEYS *SSL_ECH_KEYS_new(void);

// SSL_ECH_KEYS_up_ref increments the reference count of `keys`.
OPENSSL_EXPORT void SSL_ECH_KEYS_up_ref(SSL_ECH_KEYS *keys);

// SSL_ECH_KEYS_dup_ref increments the reference count of `keys` and returns the
// same handle.
OPENSSL_EXPORT SSL_ECH_KEYS *SSL_ECH_KEYS_dup_ref(const SSL_ECH_KEYS *keys);

// SSL_ECH_KEYS_free releases memory associated with `keys`.
OPENSSL_EXPORT void SSL_ECH_KEYS_free(SSL_ECH_KEYS *keys);

// SSL_ECH_KEYS_add decodes `ech_config` as an ECHConfig and appends it with
// `key` to `keys`. If `is_retry_config` is non-zero, this config will be
// returned to the client on configuration mismatch. It returns one on success
// and zero on error.
//
// This function should be called successively to register each ECHConfig in
// decreasing order of preference. This configuration must be completed before
// setting `keys` on an `SSL_CTX` with `SSL_CTX_set1_ech_keys`. After that
// point, `keys` is immutable; no more ECHConfig values may be added.
//
// See also `SSL_CTX_set1_ech_keys`.
OPENSSL_EXPORT int SSL_ECH_KEYS_add(SSL_ECH_KEYS *keys, int is_retry_config,
                                    const uint8_t *ech_config,
                                    size_t ech_config_len,
                                    const EVP_HPKE_KEY *key);

// SSL_ECH_KEYS_has_duplicate_config_id returns one if `keys` has duplicate
// config IDs or zero otherwise. Duplicate config IDs still work, but may
// increase server load due to trial decryption.
OPENSSL_EXPORT int SSL_ECH_KEYS_has_duplicate_config_id(
    const SSL_ECH_KEYS *keys);

// SSL_ECH_KEYS_marshal_retry_configs serializes the retry configs in `keys` as
// an ECHConfigList. On success, it sets `*out` to a newly-allocated buffer
// containing the result and `*out_len` to the size of the buffer. The caller
// must call `OPENSSL_free` on `*out` to release the memory. On failure, it
// returns zero.
//
// This output may be advertised to clients in DNS.
OPENSSL_EXPORT int SSL_ECH_KEYS_marshal_retry_configs(const SSL_ECH_KEYS *keys,
                                                      uint8_t **out,
                                                      size_t *out_len);

// SSL_CTX_set1_ech_keys configures `ctx` to use `keys` to decrypt encrypted
// ClientHellos. It returns one on success, and zero on failure. If `keys` does
// not contain any retry configs, this function will fail. Retry configs are
// marked as such when they are added to `keys` with `SSL_ECH_KEYS_add`.
//
// Once `keys` has been passed to this function, it is immutable. Unlike most
// `SSL_CTX` configuration functions, this function may be called even if `ctx`
// already has associated connections on multiple threads. This may be used to
// rotate keys in a long-lived server process.
//
// The configured ECHConfig values should also be advertised out-of-band via DNS
// (see RFC 9848). Before advertising an ECHConfig in DNS, deployments should
// ensure all instances of the service are configured with the ECHConfig and
// corresponding private key.
//
// Only the most recent fully-deployed ECHConfigs should be advertised in DNS.
// `keys` may contain a newer set if those ECHConfigs are mid-deployment. It
// should also contain older sets, until the DNS change has rolled out and the
// old records have expired from caches.
//
// If there is a mismatch, `SSL` objects associated with `ctx` will complete the
// handshake using the cleartext ClientHello and send updated ECHConfig values
// to the client. The client will then retry to recover, but with a latency
// penalty. This recovery flow depends on the public name in the ECHConfig.
// Before advertising an ECHConfig in DNS, deployments must ensure all instances
// of the service can present a valid certificate for the public name.
//
// BoringSSL negotiates ECH before certificate selection callbacks are called,
// including `SSL_CTX_set_select_certificate_cb`. If ECH is negotiated, the
// reported `SSL_CLIENT_HELLO` structure and `SSL_get_servername` function will
// transparently reflect the inner ClientHello. Callers should select parameters
// based on these values to correctly handle ECH as well as the recovery flow.
OPENSSL_EXPORT int SSL_CTX_set1_ech_keys(SSL_CTX *ctx, SSL_ECH_KEYS *keys);

// SSL_ech_accepted returns one if `ssl` negotiated ECH and zero otherwise.
OPENSSL_EXPORT int SSL_ech_accepted(const SSL *ssl);


// Alerts.
//
// TLS uses alerts to signal error conditions. Alerts have a type (warning or
// fatal) and description. OpenSSL internally handles fatal alerts with
// dedicated error codes (see `SSL_AD_REASON_OFFSET`). Except for close_notify,
// warning alerts are silently ignored and may only be surfaced with
// `SSL_CTX_set_info_callback`.

// SSL_AD_REASON_OFFSET is the offset between error reasons and `SSL_AD_*`
// values. Any error code under `ERR_LIB_SSL` with an error reason above this
// value corresponds to an alert description. Consumers may add or subtract
// `SSL_AD_REASON_OFFSET` to convert between them.
//
// make_errors.go reserves error codes above 1000 for manually-assigned errors.
// This value must be kept in sync with reservedReasonCode in make_errors.h
#define SSL_AD_REASON_OFFSET 1000

// SSL_AD_* are alert descriptions.
#define SSL_AD_CLOSE_NOTIFY SSL3_AD_CLOSE_NOTIFY
#define SSL_AD_UNEXPECTED_MESSAGE SSL3_AD_UNEXPECTED_MESSAGE
#define SSL_AD_BAD_RECORD_MAC SSL3_AD_BAD_RECORD_MAC
#define SSL_AD_DECRYPTION_FAILED TLS1_AD_DECRYPTION_FAILED
#define SSL_AD_RECORD_OVERFLOW TLS1_AD_RECORD_OVERFLOW
#define SSL_AD_DECOMPRESSION_FAILURE SSL3_AD_DECOMPRESSION_FAILURE
#define SSL_AD_HANDSHAKE_FAILURE SSL3_AD_HANDSHAKE_FAILURE
#define SSL_AD_NO_CERTIFICATE SSL3_AD_NO_CERTIFICATE  // Legacy SSL 3.0 value
#define SSL_AD_BAD_CERTIFICATE SSL3_AD_BAD_CERTIFICATE
#define SSL_AD_UNSUPPORTED_CERTIFICATE SSL3_AD_UNSUPPORTED_CERTIFICATE
#define SSL_AD_CERTIFICATE_REVOKED SSL3_AD_CERTIFICATE_REVOKED
#define SSL_AD_CERTIFICATE_EXPIRED SSL3_AD_CERTIFICATE_EXPIRED
#define SSL_AD_CERTIFICATE_UNKNOWN SSL3_AD_CERTIFICATE_UNKNOWN
#define SSL_AD_ILLEGAL_PARAMETER SSL3_AD_ILLEGAL_PARAMETER
#define SSL_AD_UNKNOWN_CA TLS1_AD_UNKNOWN_CA
#define SSL_AD_ACCESS_DENIED TLS1_AD_ACCESS_DENIED
#define SSL_AD_DECODE_ERROR TLS1_AD_DECODE_ERROR
#define SSL_AD_DECRYPT_ERROR TLS1_AD_DECRYPT_ERROR
#define SSL_AD_EXPORT_RESTRICTION TLS1_AD_EXPORT_RESTRICTION
#define SSL_AD_PROTOCOL_VERSION TLS1_AD_PROTOCOL_VERSION
#define SSL_AD_INSUFFICIENT_SECURITY TLS1_AD_INSUFFICIENT_SECURITY
#define SSL_AD_INTERNAL_ERROR TLS1_AD_INTERNAL_ERROR
#define SSL_AD_INAPPROPRIATE_FALLBACK SSL3_AD_INAPPROPRIATE_FALLBACK
#define SSL_AD_USER_CANCELLED TLS1_AD_USER_CANCELLED
#define SSL_AD_NO_RENEGOTIATION TLS1_AD_NO_RENEGOTIATION
#define SSL_AD_MISSING_EXTENSION TLS1_AD_MISSING_EXTENSION
#define SSL_AD_UNSUPPORTED_EXTENSION TLS1_AD_UNSUPPORTED_EXTENSION
#define SSL_AD_CERTIFICATE_UNOBTAINABLE TLS1_AD_CERTIFICATE_UNOBTAINABLE
#define SSL_AD_UNRECOGNIZED_NAME TLS1_AD_UNRECOGNIZED_NAME
#define SSL_AD_BAD_CERTIFICATE_STATUS_RESPONSE \
  TLS1_AD_BAD_CERTIFICATE_STATUS_RESPONSE
#define SSL_AD_BAD_CERTIFICATE_HASH_VALUE TLS1_AD_BAD_CERTIFICATE_HASH_VALUE
#define SSL_AD_UNKNOWN_PSK_IDENTITY TLS1_AD_UNKNOWN_PSK_IDENTITY
#define SSL_AD_CERTIFICATE_REQUIRED TLS1_AD_CERTIFICATE_REQUIRED
#define SSL_AD_NO_APPLICATION_PROTOCOL TLS1_AD_NO_APPLICATION_PROTOCOL
#define SSL_AD_ECH_REQUIRED TLS1_AD_ECH_REQUIRED

// SSL_alert_type_string_long returns a string description of `value` as an
// alert type (warning or fatal).
// This string is always ASCII-encoded.
OPENSSL_EXPORT const char *SSL_alert_type_string_long(int value);

// SSL_alert_desc_string_long returns a string description of `value` as an
// alert description or "unknown" if unknown.
// This string is always ASCII-encoded.
OPENSSL_EXPORT const char *SSL_alert_desc_string_long(int value);

// SSL_send_fatal_alert sends a fatal alert over `ssl` of the specified type,
// which should be one of the `SSL_AD_*` constants. It returns one on success
// and <= 0 on error. The caller should pass the return value into
// `SSL_get_error` to determine how to proceed. Once this function has been
// called, future calls to `SSL_write` will fail.
//
// If retrying a failed operation due to `SSL_ERROR_WANT_WRITE`, subsequent
// calls must use the same `alert` parameter.
OPENSSL_EXPORT int SSL_send_fatal_alert(SSL *ssl, uint8_t alert);


// ex_data functions.
//
// See `ex_data.h` for details.

OPENSSL_EXPORT int SSL_set_ex_data(SSL *ssl, int idx, void *data);
OPENSSL_EXPORT void *SSL_get_ex_data(const SSL *ssl, int idx);
OPENSSL_EXPORT int SSL_get_ex_new_index(long argl, void *argp,
                                        CRYPTO_EX_unused *unused,
                                        CRYPTO_EX_dup *dup_unused,
                                        CRYPTO_EX_free *free_func);

OPENSSL_EXPORT int SSL_SESSION_set_ex_data(SSL_SESSION *session, int idx,
                                           void *data);
OPENSSL_EXPORT void *SSL_SESSION_get_ex_data(const SSL_SESSION *session,
                                             int idx);
OPENSSL_EXPORT int SSL_SESSION_get_ex_new_index(long argl, void *argp,
                                                CRYPTO_EX_unused *unused,
                                                CRYPTO_EX_dup *dup_unused,
                                                CRYPTO_EX_free *free_func);

OPENSSL_EXPORT int SSL_CTX_set_ex_data(SSL_CTX *ctx, int idx, void *data);
OPENSSL_EXPORT void *SSL_CTX_get_ex_data(const SSL_CTX *ctx, int idx);
OPENSSL_EXPORT int SSL_CTX_get_ex_new_index(long argl, void *argp,
                                            CRYPTO_EX_unused *unused,
                                            CRYPTO_EX_dup *dup_unused,
                                            CRYPTO_EX_free *free_func);

OPENSSL_EXPORT int SSL_CREDENTIAL_set_ex_data(SSL_CREDENTIAL *cred, int idx,
                                              void *data);
OPENSSL_EXPORT void *SSL_CREDENTIAL_get_ex_data(const SSL_CREDENTIAL *cred,
                                                int idx);
OPENSSL_EXPORT int SSL_CREDENTIAL_get_ex_new_index(long argl, void *argp,
                                                   CRYPTO_EX_unused *unused,
                                                   CRYPTO_EX_dup *dup_unused,
                                                   CRYPTO_EX_free *free_func);


// Low-level record-layer state.

// SSL_get_ivs sets `*out_iv_len` to the length of the IVs for the ciphers
// underlying `ssl` and sets `*out_read_iv` and `*out_write_iv` to point to the
// current IVs for the read and write directions. This is only meaningful for
// connections with implicit IVs (i.e. CBC mode with TLS 1.0).
//
// It returns one on success or zero on error.
OPENSSL_EXPORT int SSL_get_ivs(const SSL *ssl, const uint8_t **out_read_iv,
                               const uint8_t **out_write_iv,
                               size_t *out_iv_len);

// SSL_get_key_block_len returns the length of `ssl`'s key block, for TLS 1.2
// and below. It is an error to call this function during a handshake, or if
// `ssl` negotiated TLS 1.3.
OPENSSL_EXPORT size_t SSL_get_key_block_len(const SSL *ssl);

// SSL_generate_key_block generates `out_len` bytes of key material for `ssl`'s
// current connection state, for TLS 1.2 and below. It is an error to call this
// function during a handshake, or if `ssl` negotiated TLS 1.3.
OPENSSL_EXPORT int SSL_generate_key_block(const SSL *ssl, uint8_t *out,
                                          size_t out_len);

// SSL_get_read_sequence returns, in TLS, the expected sequence number of the
// next incoming record in the current epoch.
//
// TODO(crbug.com/42290608): In DTLS, it returns the maximum sequence number
// received in the current epoch (for some notion of "current" specific to
// BoringSSL) and includes the epoch number in the two most significant bytes,
// but this is deprecated. Use `SSL_get_dtls_read_sequence` instead.
OPENSSL_EXPORT uint64_t SSL_get_read_sequence(const SSL *ssl);

// SSL_get_write_sequence returns the sequence number of the next outgoing
// record in the current epoch.
//
// TODO(crbug.com/42290608): In DTLS, it includes the epoch number in the two
// most significant bytes, but this is deprecated. Use
// `SSL_get_dtls_write_sequence` instead.
OPENSSL_EXPORT uint64_t SSL_get_write_sequence(const SSL *ssl);

// SSL_CTX_set_record_protocol_version returns whether `version` is zero.
OPENSSL_EXPORT int SSL_CTX_set_record_protocol_version(SSL_CTX *ctx,
                                                       int version);

// SSL_is_dtls_handshake_idle returns one `ssl`'s handshake is idle and zero if
// it is busy. The handshake is considered idle if all of the following are
// true:
//
// - `ssl` is not mid handshake or post-handshake transaction.
// - In DTLS 1.3, all sent handshake messages have been acknowledged. That is,
//   `ssl` does not have data to retransmit.
// - All received handshake data has been processed. That is, `ssl` has no
//   buffered partial or out-of-order messages.
//
// If any condition is false, the handshake is considered busy. If this function
// reports the handshake is busy, it is expected that the handshake will become
// idle after short timers and a few roundtrips of successful communication.
// However, this is not guaranteed if, e.g., the peer misbehaves or sends many
// KeyUpdates.
//
// WARNING: In DTLS 1.3, this function may return one while multiple active read
// epochs exist in `ssl`.
//
// WARNING: In DTLS 1.2 (or earlier), if `ssl` is the role that speaks last, it
// retains its final flight for retransmission in case of loss. There is no
// explicit protocol signal for when this completes, though after receiving
// application data and/or a timeout it is likely that this is no longer needed.
// BoringSSL does not currently evaluate either condition and leaves it to
// the caller to determine whether this is now unnecessary. This applies when
// `ssl` is a server for full handshakes and when `ssl` is a client for full
// handshakes.
OPENSSL_EXPORT int SSL_is_dtls_handshake_idle(const SSL *ssl);

// SSL_get_dtls_handshake_read_seq returns the 16-bit sequence number of the
// next DTLS handshake message to be read, or 0x10000 if handshake message
// 0xffff (the maximum) has already been read.
OPENSSL_EXPORT uint32_t SSL_get_dtls_handshake_read_seq(const SSL *ssl);

// SSL_get_dtls_handshake_write_seq returns the 16-bit sequence number of the
// next DTLS handshake message to be written or 0x10000 if handshake message
// 0xffff (the maximum) has already been written.
OPENSSL_EXPORT uint32_t SSL_get_dtls_handshake_write_seq(const SSL *ssl);

// SSL_get_dtls_read_epoch returns the highest available DTLS read epoch in
// `ssl`. In DTLS 1.3, `ssl` may have earlier epochs also active, sometimes to
// optionally improve handling of reordered packets and sometimes as an
// important part of the protocol correctness in the face of packet loss.
//
// The failure conditions of `SSL_get_dtls_read_traffic_secret` and
// `SSL_get_dtls_read_sequence` can be used to determine if past epochs are
// active.
OPENSSL_EXPORT uint16_t SSL_get_dtls_read_epoch(const SSL *ssl);

// SSL_get_dtls_write_epoch returns the current DTLS write epoch. If the
// handshake is idle (see `SSL_is_dtls_handshake_idle`), no other write epochs
// will be active.
OPENSSL_EXPORT uint16_t SSL_get_dtls_write_epoch(const SSL *ssl);

// SSL_get_dtls_read_sequence returns one more than the sequence number of the
// highest record received in `epoch`. If no records have been received in
// `epoch`. If the epoch does not exist, it returns `UINT64_MAX`.
//
// It is safe to discard all sequence numbers less than the return value of this
// function. The sequence numbers returned by this function do not include the
// epoch number in the upper 16 bits.
OPENSSL_EXPORT uint64_t SSL_get_dtls_read_sequence(const SSL *ssl,
                                                   uint16_t epoch);

// SSL_get_dtls_write_sequence returns the sequence number of the next record to
// be sent in `epoch`. If the epoch does not exist, it returns `UINT64_MAX`.
//
// The sequence numbers returned by this function do not include the epoch
// number in the upper 16 bits.
OPENSSL_EXPORT uint64_t SSL_get_dtls_write_sequence(const SSL *ssl,
                                                    uint16_t epoch);

// SSL_get_dtls_read_traffic_secret looks up the traffic secret for read epoch
// `epoch`. If the epoch exists and is an encrypted (not epoch zero) DTLS 1.3
// epoch, it sets `*out_data` and `*out_len` to a buffer containing the secrets
// and returns one. Otherwise, it returns zero. The buffer is valid until the
// next operation on `ssl`.
OPENSSL_EXPORT int SSL_get_dtls_read_traffic_secret(const SSL *ssl,
                                                    const uint8_t **out_data,
                                                    size_t *out_len,
                                                    uint16_t epoch);

// SSL_get_dtls_write_traffic_secret looks up the traffic secret for write epoch
// `epoch`. If the epoch exists and is an encrypted (not epoch zero) DTLS 1.3
// epoch, it sets `*out_data` and `*out_len` to a buffer containing the secrets
// and returns one. Otherwise, it returns zero. The buffer is valid until the
// next operation on `ssl`.
OPENSSL_EXPORT int SSL_get_dtls_write_traffic_secret(const SSL *ssl,
                                                     const uint8_t **out_data,
                                                     size_t *out_len,
                                                     uint16_t epoch);


// Handshake hints.
//
// WARNING: Contact the BoringSSL team before using this API. While this
// mechanism was designed to gracefully recover from version skew and
// configuration mismatch, splitting a single TLS server into multiple services
// is complex.
//
// Some server deployments make asynchronous RPC calls in both ClientHello
// dispatch and private key operations. In TLS handshakes where the private key
// operation occurs in the first round-trip, this results in two consecutive RPC
// round-trips. Handshake hints allow the RPC service to predict a signature.
// If correctly predicted, this can skip the second RPC call.
//
// First, the server installs a certificate selection callback (see
// `SSL_CTX_set_select_certificate_cb`). When that is called, it performs the
// RPC as before, but includes the ClientHello and a capabilities string from
// `SSL_serialize_capabilities`.
//
// Next, the RPC service creates its own `SSL` object, applies the results of
// certificate selection, calls `SSL_request_handshake_hints`, and runs the
// handshake. If this successfully computes handshake hints (see
// `SSL_serialize_handshake_hints`), the RPC server should send the hints
// alongside any certificate selection results.
//
// Finally, the server calls `SSL_set_handshake_hints` and applies any
// configuration from the RPC server. It then completes the handshake as before.
// If the hints apply, BoringSSL will use the predicted signature and skip the
// private key callbacks. Otherwise, BoringSSL will call private key callbacks
// to generate a signature as before.
//
// Callers should synchronize configuration across the two services.
// Configuration mismatches and some cases of version skew are not fatal, but
// may result in the hints not applying. Additionally, some handshake flows use
// the private key in later round-trips, such as TLS 1.3 HelloRetryRequest. In
// those cases, BoringSSL will not predict a signature as there is no benefit.
// Callers must allow for handshakes to complete without a predicted signature.

// SSL_serialize_capabilities writes an opaque byte string to `out` describing
// some of `ssl`'s capabilities. It returns one on success and zero on error.
//
// This string is used by BoringSSL internally to reduce the impact of version
// skew.
OPENSSL_EXPORT int SSL_serialize_capabilities(const SSL *ssl, CBB *out);

// SSL_request_handshake_hints configures `ssl` to generate a handshake hint for
// `client_hello`. It returns one on success and zero on error. `client_hello`
// should contain a serialized ClientHello structure, from the `client_hello`
// and `client_hello_len` fields of the `SSL_CLIENT_HELLO` structure.
// `capabilities` should contain the output of `SSL_serialize_capabilities`.
//
// When configured, `ssl` will perform no I/O (so there is no need to configure
// `BIO`s). For QUIC, the caller should still configure an `SSL_QUIC_METHOD`,
// but the callbacks themselves will never be called and may be left NULL or
// report failure. `SSL_provide_quic_data` also should not be called.
//
// If hint generation is successful, `SSL_do_handshake` will stop the handshake
// early with `SSL_get_error` returning `SSL_ERROR_HANDSHAKE_HINTS_READY`. At
// this point, the caller should run `SSL_serialize_handshake_hints` to extract
// the resulting hints.
//
// Hint generation may fail if, e.g., `ssl` was unable to process the
// ClientHello. Callers should then complete the certificate selection RPC and
// continue the original handshake with no hint. It will likely fail, but this
// reports the correct alert to the client and is more robust in case of
// mismatch.
OPENSSL_EXPORT int SSL_request_handshake_hints(SSL *ssl,
                                               const uint8_t *client_hello,
                                               size_t client_hello_len,
                                               const uint8_t *capabilities,
                                               size_t capabilities_len);

// SSL_serialize_handshake_hints writes an opaque byte string to `out`
// containing the handshake hints computed by `out`. It returns one on success
// and zero on error. This function should only be called if
// `SSL_request_handshake_hints` was configured and the handshake terminated
// with `SSL_ERROR_HANDSHAKE_HINTS_READY`.
//
// This string may be passed to `SSL_set_handshake_hints` on another `SSL` to
// avoid an extra signature call.
OPENSSL_EXPORT int SSL_serialize_handshake_hints(const SSL *ssl, CBB *out);

// SSL_set_handshake_hints configures `ssl` to use `hints` as handshake hints.
// It returns one on success and zero on error. The handshake will then continue
// as before, but apply predicted values from `hints` where applicable.
//
// Hints may contain connection and session secrets, so they must not leak and
// must come from a source trusted to terminate the connection. However, they
// will not change `ssl`'s configuration. The caller is responsible for
// serializing and applying options from the RPC server as needed. This ensures
// `ssl`'s behavior is self-consistent and consistent with the caller's local
// decisions.
OPENSSL_EXPORT int SSL_set_handshake_hints(SSL *ssl, const uint8_t *hints,
                                           size_t hints_len);


// Obscure functions.

// SSL_CTX_set_msg_callback installs `cb` as the message callback for `ctx`.
// This callback will be called when sending or receiving low-level record
// headers, complete handshake messages, ChangeCipherSpec, alerts, and DTLS
// ACKs. `write_p` is one for outgoing messages and zero for incoming messages.
//
// For each record header, `cb` is called with `version` = 0 and `content_type`
// = `SSL3_RT_HEADER`. The `len` bytes from `buf` contain the header. Note that
// this does not include the record body. If the record is sealed, the length
// in the header is the length of the ciphertext.
//
// For each handshake message, ChangeCipherSpec, alert, and DTLS ACK, `version`
// is the protocol version and `content_type` is the corresponding record type.
// The `len` bytes from `buf` contain the handshake message, one-byte
// ChangeCipherSpec body, two-byte alert, and ACK respectively.
//
// In connections that enable ECH, `cb` is additionally called with
// `content_type` = `SSL3_RT_CLIENT_HELLO_INNER` for each ClientHelloInner that
// is encrypted or decrypted. The `len` bytes from `buf` contain the
// ClientHelloInner, including the reconstructed outer extensions and handshake
// header.
//
// For a V2ClientHello, `version` is `SSL2_VERSION`, `content_type` is zero, and
// the `len` bytes from `buf` contain the V2ClientHello structure.
OPENSSL_EXPORT void SSL_CTX_set_msg_callback(
    SSL_CTX *ctx, void (*cb)(int is_write, int version, int content_type,
                             const void *buf, size_t len, SSL *ssl, void *arg));

// SSL_CTX_set_msg_callback_arg sets the `arg` parameter of the message
// callback.
OPENSSL_EXPORT void SSL_CTX_set_msg_callback_arg(SSL_CTX *ctx, void *arg);

// SSL_set_msg_callback installs `cb` as the message callback of `ssl`. See
// `SSL_CTX_set_msg_callback` for when this callback is called.
OPENSSL_EXPORT void SSL_set_msg_callback(
    SSL *ssl, void (*cb)(int write_p, int version, int content_type,
                         const void *buf, size_t len, SSL *ssl, void *arg));

// SSL_set_msg_callback_arg sets the `arg` parameter of the message callback.
OPENSSL_EXPORT void SSL_set_msg_callback_arg(SSL *ssl, void *arg);

// SSL_CTX_set_keylog_callback configures a callback to log key material. This
// is intended for debugging use with tools like Wireshark. The `cb` function
// should log `line` followed by a newline, synchronizing with any concurrent
// access to the log.
//
// The format is described in RFC 9850.
//
// WARNING: The data in `line` allows an attacker to break security properties
// of the TLS protocol, including confidentiality, integrity, and forward
// secrecy. This impacts both the current connection, and, in TLS 1.2, future
// connections that resume a session from it. Both direct access to the data and
// side channel leaks from application code are possible attack vectors. This
// callback is intended for debugging and should not be used in production
// connections.
OPENSSL_EXPORT void SSL_CTX_set_keylog_callback(SSL_CTX *ctx,
                                                void (*cb)(const SSL *ssl,
                                                           const char *line));

// SSL_CTX_get_keylog_callback returns the callback configured by
// `SSL_CTX_set_keylog_callback`.
OPENSSL_EXPORT void (*SSL_CTX_get_keylog_callback(const SSL_CTX *ctx))(
    const SSL *ssl, const char *line);

// SSL_CTX_set_current_time_cb configures a callback to retrieve the current
// time, which should be set in `*out_clock`. This can be used for testing
// purposes; for example, a callback can be configured that returns a time
// set explicitly by the test. The `ssl` pointer passed to `cb` is always null.
OPENSSL_EXPORT void SSL_CTX_set_current_time_cb(
    SSL_CTX *ctx, void (*cb)(const SSL *ssl, struct timeval *out_clock));

// SSL_set_shed_handshake_config allows some of the configuration of `ssl` to be
// freed after its handshake completes.  Once configuration has been shed, APIs
// that query it may fail.  "Configuration" in this context means anything that
// was set by the caller, as distinct from information derived from the
// handshake.  For example, `SSL_get_ciphers` queries how the `SSL` was
// configured by the caller, and fails after configuration has been shed,
// whereas `SSL_get_cipher` queries the result of the handshake, and is
// unaffected by configuration shedding.
//
// If configuration shedding is enabled, it is an error to call `SSL_clear`.
//
// Note that configuration shedding as a client additionally depends on
// renegotiation being disabled (see `SSL_set_renegotiate_mode`). If
// renegotiation is possible, the configuration will be retained. If
// configuration shedding is enabled and renegotiation later disabled after the
// handshake, `SSL_set_renegotiate_mode` will shed configuration then. This may
// be useful for clients which support renegotiation with some ALPN protocols,
// such as HTTP/1.1, and not others, such as HTTP/2.
OPENSSL_EXPORT void SSL_set_shed_handshake_config(SSL *ssl, int enable);

enum ssl_renegotiate_mode_t BORINGSSL_ENUM_INT {
  ssl_renegotiate_never = 0,
  ssl_renegotiate_once,
  ssl_renegotiate_freely,
  ssl_renegotiate_ignore,
  ssl_renegotiate_explicit,
};

// SSL_set_renegotiate_mode configures how `ssl`, a client, reacts to
// renegotiation attempts by a server. If `ssl` is a server, peer-initiated
// renegotiations are *always* rejected and this function does nothing.
//
// WARNING: Renegotiation is error-prone, complicates TLS's security properties,
// and increases its attack surface. When enabled, many common assumptions about
// BoringSSL's behavior no longer hold, and the calling application must handle
// more cases. Renegotiation is also incompatible with many application
// protocols, e.g. section 9.2.1 of RFC 7540. Many functions behave in ambiguous
// or undefined ways during a renegotiation.
//
// The renegotiation mode defaults to `ssl_renegotiate_never`, but may be set
// at any point in a connection's lifetime. Set it to `ssl_renegotiate_once` to
// allow one renegotiation, `ssl_renegotiate_freely` to allow all
// renegotiations or `ssl_renegotiate_ignore` to ignore HelloRequest messages.
// Note that ignoring HelloRequest messages may cause the connection to stall
// if the server waits for the renegotiation to complete.
//
// If set to `ssl_renegotiate_explicit`, `SSL_read` and `SSL_peek` calls which
// encounter a HelloRequest will pause with `SSL_ERROR_WANT_RENEGOTIATE`.
// `SSL_write` will continue to work while paused. The caller may call
// `SSL_renegotiate` to begin the renegotiation at a later point. This mode may
// be used if callers wish to eagerly call `SSL_peek` without triggering a
// renegotiation.
//
// If configuration shedding is enabled (see `SSL_set_shed_handshake_config`),
// configuration is released if, at any point after the handshake, renegotiation
// is disabled. It is not possible to switch from disabling renegotiation to
// enabling it on a given connection. Callers that condition renegotiation on,
// e.g., ALPN must enable renegotiation before the handshake and conditionally
// disable it afterwards.
//
// When enabled, renegotiation can cause properties of `ssl`, such as the cipher
// suite, to change during the lifetime of the connection. More over, during a
// renegotiation, not all properties of the new handshake are available or fully
// established. In BoringSSL, most functions, such as `SSL_get_current_cipher`,
// report information from the most recently completed handshake, not the
// pending one. However, renegotiation may rerun handshake callbacks, such as
// `SSL_CTX_set_cert_cb`. Such callbacks must ensure they are acting on the
// desired versions of each property.
//
// BoringSSL does not reverify peer certificates on renegotiation and instead
// requires they match between handshakes, so certificate verification callbacks
// (see `SSL_CTX_set_custom_verify`) may assume `ssl` is in the initial
// handshake and use `SSL_get0_peer_certificates`, etc.
//
// There is no support in BoringSSL for initiating renegotiations as a client
// or server.
OPENSSL_EXPORT void SSL_set_renegotiate_mode(SSL *ssl,
                                             enum ssl_renegotiate_mode_t mode);

// SSL_renegotiate starts a deferred renegotiation on `ssl` if it was configured
// with `ssl_renegotiate_explicit` and has a pending HelloRequest. It returns
// one on success and zero on error.
//
// This function does not do perform any I/O. On success, a subsequent
// `SSL_do_handshake` call will run the handshake. `SSL_write` and
// `SSL_read` will also complete the handshake before sending or receiving
// application data.
OPENSSL_EXPORT int SSL_renegotiate(SSL *ssl);

// SSL_renegotiate_pending returns one if `ssl` is in the middle of a
// renegotiation.
OPENSSL_EXPORT int SSL_renegotiate_pending(SSL *ssl);

// SSL_total_renegotiations returns the total number of renegotiation handshakes
// performed by `ssl`. This includes the pending renegotiation, if any.
OPENSSL_EXPORT int SSL_total_renegotiations(const SSL *ssl);

// SSL_MAX_CERT_LIST_DEFAULT is the default maximum length, in bytes, of a peer
// certificate chain.
#define SSL_MAX_CERT_LIST_DEFAULT (1024 * 100)

// SSL_CTX_get_max_cert_list returns the maximum length, in bytes, of a peer
// certificate chain accepted by `ctx`.
OPENSSL_EXPORT size_t SSL_CTX_get_max_cert_list(const SSL_CTX *ctx);

// SSL_CTX_set_max_cert_list sets the maximum length, in bytes, of a peer
// certificate chain to `max_cert_list`. This affects how much memory may be
// consumed during the handshake.
OPENSSL_EXPORT void SSL_CTX_set_max_cert_list(SSL_CTX *ctx,
                                              size_t max_cert_list);

// SSL_get_max_cert_list returns the maximum length, in bytes, of a peer
// certificate chain accepted by `ssl`.
OPENSSL_EXPORT size_t SSL_get_max_cert_list(const SSL *ssl);

// SSL_set_max_cert_list sets the maximum length, in bytes, of a peer
// certificate chain to `max_cert_list`. This affects how much memory may be
// consumed during the handshake.
OPENSSL_EXPORT void SSL_set_max_cert_list(SSL *ssl, size_t max_cert_list);

// SSL_CTX_set_max_send_fragment sets the maximum length, in bytes, of records
// sent by `ctx`. Beyond this length, handshake messages and application data
// will be split into multiple records. It returns one on success or zero on
// error.
OPENSSL_EXPORT int SSL_CTX_set_max_send_fragment(SSL_CTX *ctx,
                                                 size_t max_send_fragment);

// SSL_set_max_send_fragment sets the maximum length, in bytes, of records sent
// by `ssl`. Beyond this length, handshake messages and application data will
// be split into multiple records. It returns one on success or zero on
// error.
OPENSSL_EXPORT int SSL_set_max_send_fragment(SSL *ssl,
                                             size_t max_send_fragment);

// ssl_early_callback_ctx (aka `SSL_CLIENT_HELLO`) is passed to certain
// callbacks that are called very early on during the server handshake. At this
// point, much of the SSL* hasn't been filled out and only the ClientHello can
// be depended on.
struct ssl_early_callback_ctx {
  SSL *ssl;
  const uint8_t *client_hello;
  size_t client_hello_len;
  uint16_t version;
  const uint8_t *random;
  size_t random_len;
  const uint8_t *session_id;
  size_t session_id_len;
  const uint8_t *dtls_cookie;
  size_t dtls_cookie_len;
  const uint8_t *cipher_suites;
  size_t cipher_suites_len;
  const uint8_t *compression_methods;
  size_t compression_methods_len;
  const uint8_t *extensions;
  size_t extensions_len;
} /* SSL_CLIENT_HELLO */;

// ssl_select_cert_result_t enumerates the possible results from selecting a
// certificate with `select_certificate_cb`.
enum ssl_select_cert_result_t BORINGSSL_ENUM_INT {
  // ssl_select_cert_success indicates that the certificate selection was
  // successful.
  ssl_select_cert_success = 1,
  // ssl_select_cert_retry indicates that the operation could not be
  // immediately completed and must be reattempted at a later point.
  ssl_select_cert_retry = 0,
  // ssl_select_cert_error indicates that a fatal error occurred and the
  // handshake should be terminated.
  ssl_select_cert_error = -1,
  // ssl_select_cert_disable_ech indicates that, although an encrypted
  // ClientHelloInner was decrypted, it should be discarded. The certificate
  // selection callback will then be called again, passing in the
  // ClientHelloOuter instead. From there, the handshake will proceed
  // without retry_configs, to signal to the client to disable ECH.
  //
  // This value may only be returned when `SSL_ech_accepted` returns one. It
  // may be useful if the ClientHelloInner indicated a service which does not
  // support ECH, e.g. if it is a TLS-1.2 only service.
  ssl_select_cert_disable_ech = -2,
};

// SSL_early_callback_ctx_extension_get searches the extensions in
// `client_hello` for an extension of the given type. If not found, it returns
// zero. Otherwise it sets `out_data` to point to the extension contents (not
// including the type and length bytes), sets `out_len` to the length of the
// extension contents and returns one.
OPENSSL_EXPORT int SSL_early_callback_ctx_extension_get(
    const SSL_CLIENT_HELLO *client_hello, uint16_t extension_type,
    const uint8_t **out_data, size_t *out_len);

// SSL_CTX_set_select_certificate_cb sets a callback that is called before most
// ClientHello processing and before the decision whether to resume a session
// is made. The callback may inspect the ClientHello and configure the
// connection. See `ssl_select_cert_result_t` for details of the return values.
//
// In the case that a retry is indicated, `SSL_get_error` will return
// `SSL_ERROR_PENDING_CERTIFICATE` and the caller should arrange for the
// high-level operation on `ssl` to be retried at a later time, which will
// result in another call to `cb`.
//
// `SSL_get_servername` may be used during this callback.
//
// Note: The `SSL_CLIENT_HELLO` is only valid for the duration of the callback
// and is not valid while the handshake is paused.
OPENSSL_EXPORT void SSL_CTX_set_select_certificate_cb(
    SSL_CTX *ctx,
    enum ssl_select_cert_result_t (*cb)(const SSL_CLIENT_HELLO *));

// SSL_CTX_set_dos_protection_cb sets a callback that is called once the
// resumption decision for a ClientHello has been made. It can return one to
// allow the handshake to continue or zero to cause the handshake to abort.
OPENSSL_EXPORT void SSL_CTX_set_dos_protection_cb(
    SSL_CTX *ctx, int (*cb)(const SSL_CLIENT_HELLO *));

// SSL_CTX_set_reverify_on_resume configures whether the certificate
// verification callback will be used to reverify stored certificates
// when resuming a session. This only works with `SSL_CTX_set_custom_verify`.
// For now, this is incompatible with `SSL_VERIFY_NONE` mode, and is only
// respected on clients.
OPENSSL_EXPORT void SSL_CTX_set_reverify_on_resume(SSL_CTX *ctx, int enabled);

// SSL_ST_* are possible values for `SSL_state`, the bitmasks that make them up,
// and some historical values for compatibility. Only `SSL_ST_INIT` and
// `SSL_ST_OK` are ever returned.
#define SSL_ST_CONNECT 0x1000
#define SSL_ST_ACCEPT 0x2000
#define SSL_ST_MASK 0x0FFF
#define SSL_ST_INIT (SSL_ST_CONNECT | SSL_ST_ACCEPT)
#define SSL_ST_OK 0x03
#define SSL_ST_RENEGOTIATE (0x04 | SSL_ST_INIT)
#define SSL_ST_BEFORE (0x05 | SSL_ST_INIT)

// TLS_ST_* are aliases for `SSL_ST_*` for OpenSSL 1.1.0 compatibility.
#define TLS_ST_OK SSL_ST_OK
#define TLS_ST_BEFORE SSL_ST_BEFORE

// SSL_CB_* are possible values for the `type` parameter in the info
// callback and the bitmasks that make them up.
#define SSL_CB_LOOP 0x01
#define SSL_CB_EXIT 0x02
#define SSL_CB_READ 0x04
#define SSL_CB_WRITE 0x08
#define SSL_CB_ALERT 0x4000
#define SSL_CB_READ_ALERT (SSL_CB_ALERT | SSL_CB_READ)
#define SSL_CB_WRITE_ALERT (SSL_CB_ALERT | SSL_CB_WRITE)
#define SSL_CB_ACCEPT_LOOP (SSL_ST_ACCEPT | SSL_CB_LOOP)
#define SSL_CB_ACCEPT_EXIT (SSL_ST_ACCEPT | SSL_CB_EXIT)
#define SSL_CB_CONNECT_LOOP (SSL_ST_CONNECT | SSL_CB_LOOP)
#define SSL_CB_CONNECT_EXIT (SSL_ST_CONNECT | SSL_CB_EXIT)
#define SSL_CB_HANDSHAKE_START 0x10
#define SSL_CB_HANDSHAKE_DONE 0x20

// SSL_CTX_set_info_callback configures a callback to be run when various
// events occur during a connection's lifetime. The `type` argument determines
// the type of event and the meaning of the `value` argument. Callbacks must
// ignore unexpected `type` values.
//
// `SSL_CB_READ_ALERT` is signaled for each alert received, warning or fatal.
// The `value` argument is a 16-bit value where the alert level (either
// `SSL3_AL_WARNING` or `SSL3_AL_FATAL`) is in the most-significant eight bits
// and the alert type (one of `SSL_AD_*`) is in the least-significant eight.
//
// `SSL_CB_WRITE_ALERT` is signaled for each alert sent. The `value` argument
// is constructed as with `SSL_CB_READ_ALERT`.
//
// `SSL_CB_HANDSHAKE_START` is signaled when a handshake begins. The `value`
// argument is always one.
//
// `SSL_CB_HANDSHAKE_DONE` is signaled when a handshake completes successfully.
// The `value` argument is always one. If a handshake False Starts, this event
// may be used to determine when the Finished message is received.
//
// The following event types expose implementation details of the handshake
// state machine. Consuming them is deprecated.
//
// `SSL_CB_ACCEPT_LOOP` (respectively, `SSL_CB_CONNECT_LOOP`) is signaled when
// a server (respectively, client) handshake progresses. The `value` argument
// is always one.
//
// `SSL_CB_ACCEPT_EXIT` (respectively, `SSL_CB_CONNECT_EXIT`) is signaled when
// a server (respectively, client) handshake completes, fails, or is paused.
// The `value` argument is one if the handshake succeeded and <= 0
// otherwise.
OPENSSL_EXPORT void SSL_CTX_set_info_callback(SSL_CTX *ctx,
                                              void (*cb)(const SSL *ssl,
                                                         int type, int value));

// SSL_CTX_get_info_callback returns the callback set by
// `SSL_CTX_set_info_callback`.
OPENSSL_EXPORT void (*SSL_CTX_get_info_callback(SSL_CTX *ctx))(const SSL *ssl,
                                                               int type,
                                                               int value);

// SSL_set_info_callback configures a callback to be run at various events
// during a connection's lifetime. See `SSL_CTX_set_info_callback`.
OPENSSL_EXPORT void SSL_set_info_callback(SSL *ssl,
                                          void (*cb)(const SSL *ssl, int type,
                                                     int value));

// SSL_get_info_callback returns the callback set by `SSL_set_info_callback`.
OPENSSL_EXPORT void (*SSL_get_info_callback(const SSL *ssl))(const SSL *ssl,
                                                             int type,
                                                             int value);

// SSL_state_string_long returns the current state of the handshake state
// machine as a string. This may be useful for debugging and logging.
// This string is always ASCII-encoded.
OPENSSL_EXPORT const char *SSL_state_string_long(const SSL *ssl);

#define SSL_SENT_SHUTDOWN 1
#define SSL_RECEIVED_SHUTDOWN 2

// SSL_get_shutdown returns a bitmask with a subset of `SSL_SENT_SHUTDOWN` and
// `SSL_RECEIVED_SHUTDOWN` to query whether close_notify was sent or received,
// respectively.
OPENSSL_EXPORT int SSL_get_shutdown(const SSL *ssl);

// SSL_get_peer_signature_algorithm returns the signature algorithm used by the
// peer. If not applicable, it returns zero.
OPENSSL_EXPORT uint16_t SSL_get_peer_signature_algorithm(const SSL *ssl);

// SSL_get_client_random writes up to `max_out` bytes of the most recent
// handshake's client_random to `out` and returns the number of bytes written.
// If `max_out` is zero, it returns the size of the client_random.
OPENSSL_EXPORT size_t SSL_get_client_random(const SSL *ssl, uint8_t *out,
                                            size_t max_out);

// SSL_get_server_random writes up to `max_out` bytes of the most recent
// handshake's server_random to `out` and returns the number of bytes written.
// If `max_out` is zero, it returns the size of the server_random.
OPENSSL_EXPORT size_t SSL_get_server_random(const SSL *ssl, uint8_t *out,
                                            size_t max_out);

// SSL_get_signature_algorithm_used returns the signature algorithm that `ssl`
// used, or will use, to generate a signature in the current handshake. If not
// applicable (e.g. if `ssl` did not authenticate itself with a certificate), it
// returns zero.
//
// This function only returns a value during the handshake. After the handshake
// is complete, the value is discarded. If needed after the handshake, callers
// may save the value at `SSL_CB_HANDSHAKE_DONE` with
// `SSL_CTX_set_info_callback`.
OPENSSL_EXPORT uint16_t SSL_get_signature_algorithm_used(const SSL *ssl);

// SSL_get_pending_cipher returns the cipher suite for the current handshake or
// NULL if one has not been negotiated yet or there is no pending handshake.
OPENSSL_EXPORT const SSL_CIPHER *SSL_get_pending_cipher(const SSL *ssl);

// SSL_set_retain_only_sha256_of_client_certs, on a server, sets whether only
// the SHA-256 hash of peer's certificate should be saved in memory and in the
// session. This can save memory, ticket size and session cache space. If
// enabled, `SSL_get_peer_certificate` will return NULL after the handshake
// completes. See `SSL_SESSION_has_peer_sha256` and
// `SSL_SESSION_get0_peer_sha256` to query the hash.
OPENSSL_EXPORT void SSL_set_retain_only_sha256_of_client_certs(SSL *ssl,
                                                               int enable);

// SSL_CTX_set_retain_only_sha256_of_client_certs, on a server, sets whether
// only the SHA-256 hash of peer's certificate should be saved in memory and in
// the session. This can save memory, ticket size and session cache space. If
// enabled, `SSL_get_peer_certificate` will return NULL after the handshake
// completes. See `SSL_SESSION_has_peer_sha256` and
// `SSL_SESSION_get0_peer_sha256` to query the hash.
OPENSSL_EXPORT void SSL_CTX_set_retain_only_sha256_of_client_certs(SSL_CTX *ctx,
                                                                   int enable);

// SSL_CTX_set_grease_enabled configures whether sockets on `ctx` should enable
// GREASE. See RFC 8701.
// TODO(crbug.com/529360100): signature_algorithms extensions in
// CertificateRequest messages should also be GREASE'd.
OPENSSL_EXPORT void SSL_CTX_set_grease_enabled(SSL_CTX *ctx, int enabled);

// SSL_CTX_set_permute_extensions configures whether sockets on `ctx` should
// permute extensions. For now, this is only implemented for the ClientHello.
OPENSSL_EXPORT void SSL_CTX_set_permute_extensions(SSL_CTX *ctx, int enabled);

// SSL_set_permute_extensions configures whether sockets on `ssl` should
// permute extensions. For now, this is only implemented for the ClientHello.
OPENSSL_EXPORT void SSL_set_permute_extensions(SSL *ssl, int enabled);

// SSL_max_seal_overhead returns the maximum overhead, in bytes, of sealing a
// record with `ssl`.
OPENSSL_EXPORT size_t SSL_max_seal_overhead(const SSL *ssl);

// SSL_CTX_set_false_start_allowed_without_alpn configures whether connections
// on `ctx` may use False Start (if `SSL_MODE_ENABLE_FALSE_START` is enabled)
// without negotiating ALPN.
OPENSSL_EXPORT void SSL_CTX_set_false_start_allowed_without_alpn(SSL_CTX *ctx,
                                                                 int allowed);

// SSL_used_hello_retry_request returns one if the TLS 1.3 HelloRetryRequest
// message has been either sent by the server or received by the client. It
// returns zero otherwise.
OPENSSL_EXPORT int SSL_used_hello_retry_request(const SSL *ssl);

// SSL_set_jdk11_workaround configures whether to workaround various bugs in
// JDK 11's TLS 1.3 implementation by disabling TLS 1.3 for such clients.
//
// https://bugs.openjdk.java.net/browse/JDK-8211806
// https://bugs.openjdk.java.net/browse/JDK-8212885
// https://bugs.openjdk.java.net/browse/JDK-8213202
OPENSSL_EXPORT void SSL_set_jdk11_workaround(SSL *ssl, int enable);

// SSL_parse_client_hello decodes a ClientHello structure from `len` bytes in
// `in`. On success, it returns one and writes the result to `*out`. Otherwise,
// it returns zero. `ssl` will be saved into `*out` and determines how the
// ClientHello is parsed, notably TLS vs DTLS. The fields in `*out` will alias
// `in` and are only valid as long as `in` is valid and unchanged.
//
// `in` should contain just the ClientHello structure (RFC 8446 and RFC 9147),
// excluding the handshake header and already reassembled from record layer.
// That is, `in` should begin with the legacy_version field, not the
// client_hello HandshakeType constant or the handshake ContentType constant.
OPENSSL_EXPORT int SSL_parse_client_hello(const SSL *ssl, SSL_CLIENT_HELLO *out,
                                          const uint8_t *in, size_t len);

// Compliance policy configurations
//
// A TLS connection has a large number of different parameters. Some are well
// known, like cipher suites, but many are obscure and configuration functions
// for them may not exist. These policy controls allow broad configuration
// goals to be specified so that they can flow down to all the different
// parameters of a TLS connection.

enum ssl_compliance_policy_t BORINGSSL_ENUM_INT {
  // ssl_compliance_policy_none does nothing. However, since setting this
  // doesn't undo other policies it's an error to try and set it.
  ssl_compliance_policy_none,

  // ssl_compliance_policy_fips_202205 configures a TLS connection to use:
  //   * TLS 1.2 or 1.3
  //   * For TLS 1.2, only ECDHE_[RSA|ECDSA]_WITH_AES_*_GCM_SHA*.
  //   * For TLS 1.3, only AES-GCM
  //   * P-256 or P-384 for key agreement.
  //   * For server signatures, only PKCS#1/PSS with SHA256/384/512, or ECDSA
  //     with P-256 or P-384 and SHA256/SHA384.
  //
  // Note: this policy can be configured even if BoringSSL has not been built in
  // FIPS mode. Call `FIPS_mode` to check that.
  //
  // Note: this setting aids with compliance with NIST requirements but does not
  // guarantee it. Careful reading of SP 800-52r2 is recommended.
  ssl_compliance_policy_fips_202205,

  // ssl_compliance_policy_fips_202609 configures a TLS connection to use:
  //   * TLS 1.2 or 1.3
  //   * For TLS 1.2, only ECDHE_[RSA|ECDSA]_WITH_AES_*_GCM_SHA*.
  //   * For TLS 1.3, only AES-GCM
  //   * X25519MLKEM768 or ML-KEM-1024, or P-256 or P-384 for key agreement,
  //     selecting X25519MLKEM768 or ML-KEM-1024 based on client preference.
  //   * For server signatures, only PKCS#1/PSS with SHA256/384/512, or ECDSA
  //     with P-256 or P-384 and SHA256/SHA384.
  //
  // Note: this policy can be configured even if BoringSSL has not been built in
  // FIPS mode. Call `FIPS_mode` to check that.
  //
  // Note: this setting aids with compliance with NIST requirements but does not
  // guarantee it. Careful reading of SP 800-52r2 is recommended.
  ssl_compliance_policy_fips_202609,

  // ssl_compliance_policy_wpa3_192_202304 configures a TLS connection to use:
  //   * TLS 1.2 or 1.3.
  //   * For TLS 1.2, only TLS_ECDHE_[ECDSA|RSA]_WITH_AES_256_GCM_SHA384.
  //   * For TLS 1.3, only AES-256-GCM.
  //   * P-384 for key agreement.
  //   * For handshake signatures, only ECDSA with P-384 and SHA-384, or RSA
  //     with SHA-384 or SHA-512.
  //
  // No limitations on the certificate chain nor leaf public key are imposed,
  // other than by the supported signature algorithms. But WPA3's "192-bit"
  // mode requires at least P-384 or 3072-bit along the chain. The caller must
  // enforce this themselves on the verified chain using functions such as
  // `X509_STORE_CTX_get0_chain`.
  //
  // Note that this setting is less secure than the default. The
  // implementation risks of using a more obscure primitive like P-384
  // dominate other considerations.
  ssl_compliance_policy_wpa3_192_202304,

  // ssl_compliance_policy_cnsa_202407 configures a TLS connection to use:
  //   * For TLS 1.3, AES-256-GCM over AES-128-GCM over ChaCha20-Poly1305.
  //
  // I.e. it ensures that AES-GCM will be used whenever the client supports it.
  // The cipher suite configuration mini-language can be used to similarly
  // configure prior TLS versions if they are enabled.
  ssl_compliance_policy_cnsa_202407,

  // ssl_compliance_policy_cnsa1_202603 configures a TLS connection to use:
  //   * TLS 1.2 or TLS 1.3.
  //   * For TLS 1.2, only TLS_ECDHE_[ECDSA|RSA]_WITH_AES_256_GCM_SHA384.
  //   * For TLS 1.3, only AES-256-GCM.
  //   * ML-KEM-1024 or P-384 for key agreement, preferring ML-KEM-1024 if the
  //     client supports it.
  //   * For handshake signatures, only ECDSA with P-384 and SHA-384, or RSA
  //     with SHA-384.
  //
  // Note: this setting aids with compliance with CNSA requirements but does not
  // guarantee it. Careful reading of RFC 9151 is recommended.
  ssl_compliance_policy_cnsa1_202603,

  // ssl_compliance_policy_cnsa2_202603 configures a TLS connection to use:
  //   * Only TLS 1.3, with AES-256-GCM.
  //   * Only ML-KEM-1024 for key agreement.
  //   * For handshake signatures, only ECDSA with P-384 and SHA-384, or RSA
  //     with SHA-384.
  //
  // Note: this setting aids with compliance with CNSA requirements but does not
  // guarantee it. Careful reading of draft-becker-cnsa2-tls-profile is
  // recommended.
  ssl_compliance_policy_cnsa2_202603,
};

// SSL_CTX_set_compliance_policy configures various aspects of `ctx` based on
// the given policy requirements. Subsequently calling other functions that
// configure `ctx` may override `policy`, or may not. This should be the final
// configuration function called in order to have defined behaviour matching the
// configuration profile documented for `policy` above. It's a fatal error if
// `policy` is `ssl_compliance_policy_none`.
OPENSSL_EXPORT int SSL_CTX_set_compliance_policy(
    SSL_CTX *ctx, enum ssl_compliance_policy_t policy);

// SSL_CTX_get_compliance_policy returns the compliance policy configured on
// `ctx`.
OPENSSL_EXPORT enum ssl_compliance_policy_t SSL_CTX_get_compliance_policy(
    const SSL_CTX *ctx);

// SSL_set_compliance_policy acts the same as `SSL_CTX_set_compliance_policy`,
// but only configures a single `SSL*`.
OPENSSL_EXPORT int SSL_set_compliance_policy(
    SSL *ssl, enum ssl_compliance_policy_t policy);

// SSL_get_compliance_policy returns the compliance policy configured on
// `ssl`.
OPENSSL_EXPORT enum ssl_compliance_policy_t SSL_get_compliance_policy(
    const SSL *ssl);


// Server Padding
//
// The Server Padding extension allows clients to request that servers add
// additional bytes of padding through EncryptedExtensions on the TLS handshake.
// This extension is only supported on TLS 1.3 connections. This is a temporary
// feature supporting an experiment, and will be removed on conclusion of the
// experiment.

// SSL_set_server_padding_request configures `ssl` as a client to request
// `num_bytes` of additional padding from servers on the TLS handshake. The
// client can confirm whether the server sent back the requested amount of
// padding in the handshake with `SSL_server_sent_requested_padding`.
OPENSSL_EXPORT void SSL_set_server_padding_request(SSL *ssl,
                                                   uint16_t num_bytes);

// SSL_set_server_padding_enabled configures `ssl` as a server to respond to
// the server padding extension with the padding requested by the client.
// Passing 0 disables support for the server padding extension, 1 enables
// support for the extension.
//
// By default, the extension is not enabled.
OPENSSL_EXPORT void SSL_set_server_padding_enabled(SSL *ssl, int enabled);

// SSL_server_sent_requested_padding returns 1 if `ssl`, as a client, received
// the requested amount of padding from the server as requested through
// `SSL_set_server_padding_request`. Otherwise, it returns 0.
OPENSSL_EXPORT int SSL_server_sent_requested_padding(const SSL *ssl);


// Preprocessor compatibility section (hidden).
//
// Historically, a number of APIs were implemented in OpenSSL as macros and
// constants to 'ctrl' functions. To avoid breaking #ifdefs in consumers, this
// section defines a number of legacy macros.
//
// Although using either the CTRL values or their wrapper macros in #ifdefs is
// still supported, the CTRL values may not be passed to `SSL_ctrl` and
// `SSL_CTX_ctrl`. Call the functions (previously wrapper macros) instead.
//
// See PORTING.md in the BoringSSL source tree for a table of corresponding
// functions.
// https://boringssl.googlesource.com/boringssl/+/main/PORTING.md#Replacements-for-values

#define DTLS_CTRL_GET_TIMEOUT doesnt_exist
#define DTLS_CTRL_HANDLE_TIMEOUT doesnt_exist
#define SSL_CTRL_CHAIN doesnt_exist
#define SSL_CTRL_CHAIN_CERT doesnt_exist
#define SSL_CTRL_CHANNEL_ID doesnt_exist
#define SSL_CTRL_CLEAR_EXTRA_CHAIN_CERTS doesnt_exist
#define SSL_CTRL_CLEAR_MODE doesnt_exist
#define SSL_CTRL_CLEAR_OPTIONS doesnt_exist
#define SSL_CTRL_EXTRA_CHAIN_CERT doesnt_exist
#define SSL_CTRL_GET_CHAIN_CERTS doesnt_exist
#define SSL_CTRL_GET_CHANNEL_ID doesnt_exist
#define SSL_CTRL_GET_CLIENT_CERT_TYPES doesnt_exist
#define SSL_CTRL_GET_EXTRA_CHAIN_CERTS doesnt_exist
#define SSL_CTRL_GET_MAX_CERT_LIST doesnt_exist
#define SSL_CTRL_GET_NEGOTIATED_GROUP doesnt_exist
#define SSL_CTRL_GET_NUM_RENEGOTIATIONS doesnt_exist
#define SSL_CTRL_GET_READ_AHEAD doesnt_exist
#define SSL_CTRL_GET_RI_SUPPORT doesnt_exist
#define SSL_CTRL_GET_SERVER_TMP_KEY doesnt_exist
#define SSL_CTRL_GET_SESSION_REUSED doesnt_exist
#define SSL_CTRL_GET_SESS_CACHE_MODE doesnt_exist
#define SSL_CTRL_GET_SESS_CACHE_SIZE doesnt_exist
#define SSL_CTRL_GET_TLSEXT_TICKET_KEYS doesnt_exist
#define SSL_CTRL_GET_TOTAL_RENEGOTIATIONS doesnt_exist
#define SSL_CTRL_MODE doesnt_exist
#define SSL_CTRL_NEED_TMP_RSA doesnt_exist
#define SSL_CTRL_OPTIONS doesnt_exist
#define SSL_CTRL_SESS_NUMBER doesnt_exist
#define SSL_CTRL_SET_CURVES doesnt_exist
#define SSL_CTRL_SET_CURVES_LIST doesnt_exist
#define SSL_CTRL_SET_ECDH_AUTO doesnt_exist
#define SSL_CTRL_SET_GROUPS doesnt_exist
#define SSL_CTRL_SET_GROUPS_LIST doesnt_exist
#define SSL_CTRL_SET_MAX_CERT_LIST doesnt_exist
#define SSL_CTRL_SET_MAX_SEND_FRAGMENT doesnt_exist
#define SSL_CTRL_SET_MSG_CALLBACK doesnt_exist
#define SSL_CTRL_SET_MSG_CALLBACK_ARG doesnt_exist
#define SSL_CTRL_SET_MTU doesnt_exist
#define SSL_CTRL_SET_READ_AHEAD doesnt_exist
#define SSL_CTRL_SET_SESS_CACHE_MODE doesnt_exist
#define SSL_CTRL_SET_SESS_CACHE_SIZE doesnt_exist
#define SSL_CTRL_SET_TLSEXT_HOSTNAME doesnt_exist
#define SSL_CTRL_SET_TLSEXT_SERVERNAME_ARG doesnt_exist
#define SSL_CTRL_SET_TLSEXT_SERVERNAME_CB doesnt_exist
#define SSL_CTRL_SET_TLSEXT_TICKET_KEYS doesnt_exist
#define SSL_CTRL_SET_TLSEXT_TICKET_KEY_CB doesnt_exist
#define SSL_CTRL_SET_TMP_DH doesnt_exist
#define SSL_CTRL_SET_TMP_DH_CB doesnt_exist
#define SSL_CTRL_SET_TMP_ECDH doesnt_exist
#define SSL_CTRL_SET_TMP_ECDH_CB doesnt_exist
#define SSL_CTRL_SET_TMP_RSA doesnt_exist
#define SSL_CTRL_SET_TMP_RSA_CB doesnt_exist

// `BORINGSSL_PREFIX` already makes some of these symbols into macros, so there
// is no need to define conflicting macros; however it is compiler specific
// which ones become macros.
#if !defined(DTLSv1_get_timeout)
#define DTLSv1_get_timeout DTLSv1_get_timeout
#endif
#if !defined(DTLSv1_handle_timeout)
#define DTLSv1_handle_timeout DTLSv1_handle_timeout
#endif
#if !defined(SSL_CTX_add0_chain_cert)
#define SSL_CTX_add0_chain_cert SSL_CTX_add0_chain_cert
#endif
#if !defined(SSL_CTX_add1_chain_cert)
#define SSL_CTX_add1_chain_cert SSL_CTX_add1_chain_cert
#endif
#if !defined(SSL_CTX_add_extra_chain_cert)
#define SSL_CTX_add_extra_chain_cert SSL_CTX_add_extra_chain_cert
#endif
#if !defined(SSL_CTX_clear_chain_certs)
#define SSL_CTX_clear_chain_certs SSL_CTX_clear_chain_certs
#endif
#if !defined(SSL_CTX_clear_extra_chain_certs)
#define SSL_CTX_clear_extra_chain_certs SSL_CTX_clear_extra_chain_certs
#endif
#if !defined(SSL_CTX_clear_mode)
#define SSL_CTX_clear_mode SSL_CTX_clear_mode
#endif
#if !defined(SSL_CTX_clear_options)
#define SSL_CTX_clear_options SSL_CTX_clear_options
#endif
#if !defined(SSL_CTX_get0_chain_certs)
#define SSL_CTX_get0_chain_certs SSL_CTX_get0_chain_certs
#endif
#if !defined(SSL_CTX_get_extra_chain_certs)
#define SSL_CTX_get_extra_chain_certs SSL_CTX_get_extra_chain_certs
#endif
#if !defined(SSL_CTX_get_max_cert_list)
#define SSL_CTX_get_max_cert_list SSL_CTX_get_max_cert_list
#endif
#if !defined(SSL_CTX_get_mode)
#define SSL_CTX_get_mode SSL_CTX_get_mode
#endif
#if !defined(SSL_CTX_get_options)
#define SSL_CTX_get_options SSL_CTX_get_options
#endif
#if !defined(SSL_CTX_get_read_ahead)
#define SSL_CTX_get_read_ahead SSL_CTX_get_read_ahead
#endif
#if !defined(SSL_CTX_get_session_cache_mode)
#define SSL_CTX_get_session_cache_mode SSL_CTX_get_session_cache_mode
#endif
#if !defined(SSL_CTX_get_tlsext_ticket_keys)
#define SSL_CTX_get_tlsext_ticket_keys SSL_CTX_get_tlsext_ticket_keys
#endif
#if !defined(SSL_CTX_need_tmp_RSA)
#define SSL_CTX_need_tmp_RSA SSL_CTX_need_tmp_RSA
#endif
#if !defined(SSL_CTX_sess_get_cache_size)
#define SSL_CTX_sess_get_cache_size SSL_CTX_sess_get_cache_size
#endif
#if !defined(SSL_CTX_sess_number)
#define SSL_CTX_sess_number SSL_CTX_sess_number
#endif
#if !defined(SSL_CTX_sess_set_cache_size)
#define SSL_CTX_sess_set_cache_size SSL_CTX_sess_set_cache_size
#endif
#if !defined(SSL_CTX_set0_chain)
#define SSL_CTX_set0_chain SSL_CTX_set0_chain
#endif
#if !defined(SSL_CTX_set1_chain)
#define SSL_CTX_set1_chain SSL_CTX_set1_chain
#endif
#if !defined(SSL_CTX_set1_curves)
#define SSL_CTX_set1_curves SSL_CTX_set1_curves
#endif
#if !defined(SSL_CTX_set1_groups)
#define SSL_CTX_set1_groups SSL_CTX_set1_groups
#endif
#if !defined(SSL_CTX_set_max_cert_list)
#define SSL_CTX_set_max_cert_list SSL_CTX_set_max_cert_list
#endif
#if !defined(SSL_CTX_set_max_send_fragment)
#define SSL_CTX_set_max_send_fragment SSL_CTX_set_max_send_fragment
#endif
#if !defined(SSL_CTX_set_mode)
#define SSL_CTX_set_mode SSL_CTX_set_mode
#endif
#if !defined(SSL_CTX_set_msg_callback_arg)
#define SSL_CTX_set_msg_callback_arg SSL_CTX_set_msg_callback_arg
#endif
#if !defined(SSL_CTX_set_options)
#define SSL_CTX_set_options SSL_CTX_set_options
#endif
#if !defined(SSL_CTX_set_read_ahead)
#define SSL_CTX_set_read_ahead SSL_CTX_set_read_ahead
#endif
#if !defined(SSL_CTX_set_session_cache_mode)
#define SSL_CTX_set_session_cache_mode SSL_CTX_set_session_cache_mode
#endif
#if !defined(SSL_CTX_set_tlsext_servername_arg)
#define SSL_CTX_set_tlsext_servername_arg SSL_CTX_set_tlsext_servername_arg
#endif
#if !defined(SSL_CTX_set_tlsext_servername_callback)
#define SSL_CTX_set_tlsext_servername_callback \
  SSL_CTX_set_tlsext_servername_callback
#endif
#if !defined(SSL_CTX_set_tlsext_ticket_key_cb)
#define SSL_CTX_set_tlsext_ticket_key_cb SSL_CTX_set_tlsext_ticket_key_cb
#endif
#if !defined(SSL_CTX_set_tlsext_ticket_keys)
#define SSL_CTX_set_tlsext_ticket_keys SSL_CTX_set_tlsext_ticket_keys
#endif
#if !defined(SSL_CTX_set_tmp_dh)
#define SSL_CTX_set_tmp_dh SSL_CTX_set_tmp_dh
#endif
#if !defined(SSL_CTX_set_tmp_ecdh)
#define SSL_CTX_set_tmp_ecdh SSL_CTX_set_tmp_ecdh
#endif
#if !defined(SSL_CTX_set_tmp_rsa)
#define SSL_CTX_set_tmp_rsa SSL_CTX_set_tmp_rsa
#endif
#if !defined(SSL_add0_chain_cert)
#define SSL_add0_chain_cert SSL_add0_chain_cert
#endif
#if !defined(SSL_add1_chain_cert)
#define SSL_add1_chain_cert SSL_add1_chain_cert
#endif
#if !defined(SSL_clear_chain_certs)
#define SSL_clear_chain_certs SSL_clear_chain_certs
#endif
#if !defined(SSL_clear_mode)
#define SSL_clear_mode SSL_clear_mode
#endif
#if !defined(SSL_clear_options)
#define SSL_clear_options SSL_clear_options
#endif
#if !defined(SSL_get0_certificate_types)
#define SSL_get0_certificate_types SSL_get0_certificate_types
#endif
#if !defined(SSL_get0_chain_certs)
#define SSL_get0_chain_certs SSL_get0_chain_certs
#endif
#if !defined(SSL_get_max_cert_list)
#define SSL_get_max_cert_list SSL_get_max_cert_list
#endif
#if !defined(SSL_get_mode)
#define SSL_get_mode SSL_get_mode
#endif
#if !defined(SSL_get_negotiated_group)
#define SSL_get_negotiated_group SSL_get_negotiated_group
#endif
#if !defined(SSL_get_options)
#define SSL_get_options SSL_get_options
#endif
#if !defined(SSL_get_secure_renegotiation_support)
#define SSL_get_secure_renegotiation_support \
  SSL_get_secure_renegotiation_support
#endif
#if !defined(SSL_need_tmp_RSA)
#define SSL_need_tmp_RSA SSL_need_tmp_RSA
#endif
#if !defined(SSL_num_renegotiations)
#define SSL_num_renegotiations SSL_num_renegotiations
#endif
#if !defined(SSL_session_reused)
#define SSL_session_reused SSL_session_reused
#endif
#if !defined(SSL_set0_chain)
#define SSL_set0_chain SSL_set0_chain
#endif
#if !defined(SSL_set1_chain)
#define SSL_set1_chain SSL_set1_chain
#endif
#if !defined(SSL_set1_curves)
#define SSL_set1_curves SSL_set1_curves
#endif
#if !defined(SSL_set1_groups)
#define SSL_set1_groups SSL_set1_groups
#endif
#if !defined(SSL_set_max_cert_list)
#define SSL_set_max_cert_list SSL_set_max_cert_list
#endif
#if !defined(SSL_set_max_send_fragment)
#define SSL_set_max_send_fragment SSL_set_max_send_fragment
#endif
#if !defined(SSL_set_mode)
#define SSL_set_mode SSL_set_mode
#endif
#if !defined(SSL_set_msg_callback_arg)
#define SSL_set_msg_callback_arg SSL_set_msg_callback_arg
#endif
#if !defined(SSL_set_mtu)
#define SSL_set_mtu SSL_set_mtu
#endif
#if !defined(SSL_set_options)
#define SSL_set_options SSL_set_options
#endif
#if !defined(SSL_set_tlsext_host_name)
#define SSL_set_tlsext_host_name SSL_set_tlsext_host_name
#endif
#if !defined(SSL_set_tmp_dh)
#define SSL_set_tmp_dh SSL_set_tmp_dh
#endif
#if !defined(SSL_set_tmp_ecdh)
#define SSL_set_tmp_ecdh SSL_set_tmp_ecdh
#endif
#if !defined(SSL_set_tmp_rsa)
#define SSL_set_tmp_rsa SSL_set_tmp_rsa
#endif
#if !defined(SSL_total_renegotiations)
#define SSL_total_renegotiations SSL_total_renegotiations
#endif


#if defined(__cplusplus)
}  // extern C
#endif

#include <openssl/ssl_deprecated.h>  // IWYU pragma: export

#if defined(__cplusplus)

#if !defined(BORINGSSL_NO_CXX)

extern "C++" {

BSSL_NAMESPACE_BEGIN

BORINGSSL_MAKE_DELETER(SSL, SSL_free)
BORINGSSL_MAKE_DELETER(SSL_CREDENTIAL, SSL_CREDENTIAL_free)
BORINGSSL_MAKE_UP_REF(SSL_CREDENTIAL, SSL_CREDENTIAL_up_ref)
BORINGSSL_MAKE_DELETER(SSL_CTX, SSL_CTX_free)
BORINGSSL_MAKE_UP_REF(SSL_CTX, SSL_CTX_up_ref)
BORINGSSL_MAKE_DELETER(SSL_ECH_KEYS, SSL_ECH_KEYS_free)
BORINGSSL_MAKE_UP_REF(SSL_ECH_KEYS, SSL_ECH_KEYS_up_ref)
BORINGSSL_MAKE_DELETER(SSL_SESSION, SSL_SESSION_free)
BORINGSSL_MAKE_UP_REF(SSL_SESSION, SSL_SESSION_up_ref)

// SSL_get_traffic_secrets sets `*out_read_traffic_secret` and
// `*out_write_traffic_secret` to reference the current TLS 1.3 traffic secrets
// for `ssl`. It returns true on success and false on error.
//
// This function is only valid on TLS 1.3 connections that have completed the
// handshake. It is not valid for QUIC or DTLS, where multiple traffic secrets
// may be active at a time.
OPENSSL_EXPORT bool SSL_get_traffic_secrets(
    const SSL *ssl, Span<const uint8_t> *out_read_traffic_secret,
    Span<const uint8_t> *out_write_traffic_secret);

BSSL_NAMESPACE_END

}  // extern C++

#endif  // !defined(BORINGSSL_NO_CXX)

#endif

#define SSL_R_APP_DATA_IN_HANDSHAKE 100
#define SSL_R_ATTEMPT_TO_REUSE_SESSION_IN_DIFFERENT_CONTEXT 101
#define SSL_R_BAD_ALERT 102
#define SSL_R_BAD_CHANGE_CIPHER_SPEC 103
#define SSL_R_BAD_DATA_RETURNED_BY_CALLBACK 104
#define SSL_R_BAD_DH_P_LENGTH 105
#define SSL_R_BAD_DIGEST_LENGTH 106
#define SSL_R_BAD_ECC_CERT 107
#define SSL_R_BAD_ECPOINT 108
#define SSL_R_BAD_HANDSHAKE_RECORD 109
#define SSL_R_BAD_HELLO_REQUEST 110
#define SSL_R_BAD_LENGTH 111
#define SSL_R_BAD_PACKET_LENGTH 112
#define SSL_R_BAD_RSA_ENCRYPT 113
#define SSL_R_BAD_SIGNATURE 114
#define SSL_R_BAD_SRTP_MKI_VALUE 115
#define SSL_R_BAD_SRTP_PROTECTION_PROFILE_LIST 116
#define SSL_R_BAD_SSL_FILETYPE 117
#define SSL_R_BAD_WRITE_RETRY 118
#define SSL_R_BIO_NOT_SET 119
#define SSL_R_BN_LIB 120
#define SSL_R_BUFFER_TOO_SMALL 121
#define SSL_R_CA_DN_LENGTH_MISMATCH 122
#define SSL_R_CA_DN_TOO_LONG 123
#define SSL_R_CCS_RECEIVED_EARLY 124
#define SSL_R_CERTIFICATE_VERIFY_FAILED 125
#define SSL_R_CERT_CB_ERROR 126
#define SSL_R_CERT_LENGTH_MISMATCH 127
#define SSL_R_CHANNEL_ID_NOT_P256 128
#define SSL_R_CHANNEL_ID_SIGNATURE_INVALID 129
#define SSL_R_CIPHER_OR_HASH_UNAVAILABLE 130
#define SSL_R_CLIENTHELLO_PARSE_FAILED 131
#define SSL_R_CLIENTHELLO_TLSEXT 132
#define SSL_R_CONNECTION_REJECTED 133
#define SSL_R_CONNECTION_TYPE_NOT_SET 134
#define SSL_R_CUSTOM_EXTENSION_ERROR 135
#define SSL_R_DATA_LENGTH_TOO_LONG 136
#define SSL_R_DECODE_ERROR 137
#define SSL_R_DECRYPTION_FAILED 138
#define SSL_R_DECRYPTION_FAILED_OR_BAD_RECORD_MAC 139
#define SSL_R_DH_PUBLIC_VALUE_LENGTH_IS_WRONG 140
#define SSL_R_DH_P_TOO_LONG 141
#define SSL_R_DIGEST_CHECK_FAILED 142
#define SSL_R_DTLS_MESSAGE_TOO_BIG 143
#define SSL_R_ECC_CERT_NOT_FOR_SIGNING 144
#define SSL_R_EMS_STATE_INCONSISTENT 145
#define SSL_R_ENCRYPTED_LENGTH_TOO_LONG 146
#define SSL_R_ERROR_ADDING_EXTENSION 147
#define SSL_R_ERROR_IN_RECEIVED_CIPHER_LIST 148
#define SSL_R_ERROR_PARSING_EXTENSION 149
#define SSL_R_EXCESSIVE_MESSAGE_SIZE 150
#define SSL_R_EXTRA_DATA_IN_MESSAGE 151
#define SSL_R_FRAGMENT_MISMATCH 152
#define SSL_R_GOT_NEXT_PROTO_WITHOUT_EXTENSION 153
#define SSL_R_HANDSHAKE_FAILURE_ON_CLIENT_HELLO 154
#define SSL_R_HTTPS_PROXY_REQUEST 155
#define SSL_R_HTTP_REQUEST 156
#define SSL_R_INAPPROPRIATE_FALLBACK 157
#define SSL_R_INVALID_COMMAND 158
#define SSL_R_INVALID_MESSAGE 159
#define SSL_R_INVALID_SSL_SESSION 160
#define SSL_R_INVALID_TICKET_KEYS_LENGTH 161
#define SSL_R_LENGTH_MISMATCH 162
#define SSL_R_MISSING_EXTENSION 164
#define SSL_R_MISSING_RSA_CERTIFICATE 165
#define SSL_R_MISSING_TMP_DH_KEY 166
#define SSL_R_MISSING_TMP_ECDH_KEY 167
#define SSL_R_MIXED_SPECIAL_OPERATOR_WITH_GROUPS 168
#define SSL_R_MTU_TOO_SMALL 169
#define SSL_R_NEGOTIATED_BOTH_NPN_AND_ALPN 170
#define SSL_R_NESTED_GROUP 171
#define SSL_R_NO_CERTIFICATES_RETURNED 172
#define SSL_R_NO_CERTIFICATE_ASSIGNED 173
#define SSL_R_NO_CERTIFICATE_SET 174
#define SSL_R_NO_CIPHERS_AVAILABLE 175
#define SSL_R_NO_CIPHERS_PASSED 176
#define SSL_R_NO_CIPHER_MATCH 177
#define SSL_R_NO_COMPRESSION_SPECIFIED 178
#define SSL_R_NO_METHOD_SPECIFIED 179
#define SSL_R_NO_PRIVATE_KEY_ASSIGNED 181
#define SSL_R_NO_RENEGOTIATION 182
#define SSL_R_NO_REQUIRED_DIGEST 183
#define SSL_R_NO_SHARED_CIPHER 184
#define SSL_R_NULL_SSL_CTX 185
#define SSL_R_NULL_SSL_METHOD_PASSED 186
#define SSL_R_OLD_SESSION_CIPHER_NOT_RETURNED 187
#define SSL_R_OLD_SESSION_VERSION_NOT_RETURNED 188
#define SSL_R_OUTPUT_ALIASES_INPUT 189
#define SSL_R_PARSE_TLSEXT 190
#define SSL_R_PATH_TOO_LONG 191
#define SSL_R_PEER_DID_NOT_RETURN_A_CERTIFICATE 192
#define SSL_R_PEER_ERROR_UNSUPPORTED_CERTIFICATE_TYPE 193
#define SSL_R_PROTOCOL_IS_SHUTDOWN 194
#define SSL_R_PSK_IDENTITY_NOT_FOUND 195
#define SSL_R_PSK_NO_CLIENT_CB 196
#define SSL_R_PSK_NO_SERVER_CB 197
#define SSL_R_READ_TIMEOUT_EXPIRED 198
#define SSL_R_RECORD_LENGTH_MISMATCH 199
#define SSL_R_RECORD_TOO_LARGE 200
#define SSL_R_RENEGOTIATION_ENCODING_ERR 201
#define SSL_R_RENEGOTIATION_MISMATCH 202
#define SSL_R_REQUIRED_CIPHER_MISSING 203
#define SSL_R_RESUMED_EMS_SESSION_WITHOUT_EMS_EXTENSION 204
#define SSL_R_RESUMED_NON_EMS_SESSION_WITH_EMS_EXTENSION 205
#define SSL_R_SCSV_RECEIVED_WHEN_RENEGOTIATING 206
#define SSL_R_SERVERHELLO_TLSEXT 207
#define SSL_R_SESSION_ID_CONTEXT_UNINITIALIZED 208
#define SSL_R_SESSION_MAY_NOT_BE_CREATED 209
#define SSL_R_SIGNATURE_ALGORITHMS_EXTENSION_SENT_BY_SERVER 210
#define SSL_R_SRTP_COULD_NOT_ALLOCATE_PROFILES 211
#define SSL_R_SRTP_UNKNOWN_PROTECTION_PROFILE 212
#define SSL_R_SSL3_EXT_INVALID_SERVERNAME 213
#define SSL_R_SSL_CTX_HAS_NO_DEFAULT_SSL_VERSION 214
#define SSL_R_SSL_HANDSHAKE_FAILURE 215
#define SSL_R_SSL_SESSION_ID_CONTEXT_TOO_LONG 216
#define SSL_R_TLS_PEER_DID_NOT_RESPOND_WITH_CERTIFICATE_LIST 217
#define SSL_R_TLS_RSA_ENCRYPTED_VALUE_LENGTH_IS_WRONG 218
#define SSL_R_TOO_MANY_EMPTY_FRAGMENTS 219
#define SSL_R_TOO_MANY_WARNING_ALERTS 220
#define SSL_R_UNABLE_TO_FIND_ECDH_PARAMETERS 221
#define SSL_R_UNEXPECTED_EXTENSION 222
#define SSL_R_UNEXPECTED_MESSAGE 223
#define SSL_R_UNEXPECTED_OPERATOR_IN_GROUP 224
#define SSL_R_UNEXPECTED_RECORD 225
#define SSL_R_UNINITIALIZED 226
#define SSL_R_UNKNOWN_ALERT_TYPE 227
#define SSL_R_UNKNOWN_CERTIFICATE_TYPE 228
#define SSL_R_UNKNOWN_CIPHER_RETURNED 229
#define SSL_R_UNKNOWN_CIPHER_TYPE 230
#define SSL_R_UNKNOWN_DIGEST 231
#define SSL_R_UNKNOWN_KEY_EXCHANGE_TYPE 232
#define SSL_R_UNKNOWN_PROTOCOL 233
#define SSL_R_UNKNOWN_SSL_VERSION 234
#define SSL_R_UNKNOWN_STATE 235
#define SSL_R_UNSAFE_LEGACY_RENEGOTIATION_DISABLED 236
#define SSL_R_UNSUPPORTED_CIPHER 237
#define SSL_R_UNSUPPORTED_COMPRESSION_ALGORITHM 238
#define SSL_R_UNSUPPORTED_ELLIPTIC_CURVE 239
#define SSL_R_UNSUPPORTED_PROTOCOL 240
#define SSL_R_WRONG_CERTIFICATE_TYPE 241
#define SSL_R_WRONG_CIPHER_RETURNED 242
#define SSL_R_WRONG_CURVE 243
#define SSL_R_WRONG_MESSAGE_TYPE 244
#define SSL_R_WRONG_SIGNATURE_TYPE 245
#define SSL_R_WRONG_SSL_VERSION 246
#define SSL_R_WRONG_VERSION_NUMBER 247
#define SSL_R_X509_LIB 248
#define SSL_R_X509_VERIFICATION_SETUP_PROBLEMS 249
#define SSL_R_SHUTDOWN_WHILE_IN_INIT 250
#define SSL_R_INVALID_OUTER_RECORD_TYPE 251
#define SSL_R_UNSUPPORTED_PROTOCOL_FOR_CUSTOM_KEY 252
#define SSL_R_NO_COMMON_SIGNATURE_ALGORITHMS 253
#define SSL_R_DOWNGRADE_DETECTED 254
#define SSL_R_EXCESS_HANDSHAKE_DATA 255
#define SSL_R_INVALID_COMPRESSION_LIST 256
#define SSL_R_DUPLICATE_EXTENSION 257
#define SSL_R_MISSING_KEY_SHARE 258
#define SSL_R_INVALID_ALPN_PROTOCOL 259
#define SSL_R_TOO_MANY_KEY_UPDATES 260
#define SSL_R_BLOCK_CIPHER_PAD_IS_WRONG 261
#define SSL_R_NO_CIPHERS_SPECIFIED 262
#define SSL_R_RENEGOTIATION_EMS_MISMATCH 263
#define SSL_R_DUPLICATE_KEY_SHARE 264
#define SSL_R_NO_GROUPS_SPECIFIED 265
#define SSL_R_NO_SHARED_GROUP 266
#define SSL_R_PRE_SHARED_KEY_MUST_BE_LAST 267
#define SSL_R_OLD_SESSION_PRF_HASH_MISMATCH 268
#define SSL_R_INVALID_SCT_LIST 269
#define SSL_R_TOO_MUCH_SKIPPED_EARLY_DATA 270
#define SSL_R_PSK_IDENTITY_BINDER_COUNT_MISMATCH 271
#define SSL_R_CANNOT_PARSE_LEAF_CERT 272
#define SSL_R_SERVER_CERT_CHANGED 273
#define SSL_R_CERTIFICATE_AND_PRIVATE_KEY_MISMATCH 274
#define SSL_R_CANNOT_HAVE_BOTH_PRIVKEY_AND_METHOD 275
#define SSL_R_TICKET_ENCRYPTION_FAILED 276
#define SSL_R_ALPN_MISMATCH_ON_EARLY_DATA 277
#define SSL_R_WRONG_VERSION_ON_EARLY_DATA 278
#define SSL_R_UNEXPECTED_EXTENSION_ON_EARLY_DATA 279
#define SSL_R_NO_SUPPORTED_VERSIONS_ENABLED 280
#define SSL_R_EMPTY_HELLO_RETRY_REQUEST 282
#define SSL_R_EARLY_DATA_NOT_IN_USE 283
#define SSL_R_HANDSHAKE_NOT_COMPLETE 284
#define SSL_R_NEGOTIATED_TB_WITHOUT_EMS_OR_RI 285
#define SSL_R_SERVER_ECHOED_INVALID_SESSION_ID 286
#define SSL_R_PRIVATE_KEY_OPERATION_FAILED 287
#define SSL_R_SECOND_SERVERHELLO_VERSION_MISMATCH 288
#define SSL_R_OCSP_CB_ERROR 289
#define SSL_R_SSL_SESSION_ID_TOO_LONG 290
#define SSL_R_APPLICATION_DATA_ON_SHUTDOWN 291
#define SSL_R_CERT_DECOMPRESSION_FAILED 292
#define SSL_R_UNCOMPRESSED_CERT_TOO_LARGE 293
#define SSL_R_UNKNOWN_CERT_COMPRESSION_ALG 294
#define SSL_R_INVALID_SIGNATURE_ALGORITHM 295
#define SSL_R_DUPLICATE_SIGNATURE_ALGORITHM 296
#define SSL_R_TLS13_DOWNGRADE 297
#define SSL_R_QUIC_INTERNAL_ERROR 298
#define SSL_R_WRONG_ENCRYPTION_LEVEL_RECEIVED 299
#define SSL_R_TOO_MUCH_READ_EARLY_DATA 300
#define SSL_R_INVALID_DELEGATED_CREDENTIAL 301
#define SSL_R_KEY_USAGE_BIT_INCORRECT 302
#define SSL_R_INCONSISTENT_CLIENT_HELLO 303
#define SSL_R_CIPHER_MISMATCH_ON_EARLY_DATA 304
#define SSL_R_QUIC_TRANSPORT_PARAMETERS_MISCONFIGURED 305
#define SSL_R_UNEXPECTED_COMPATIBILITY_MODE 306
#define SSL_R_NO_APPLICATION_PROTOCOL 307
#define SSL_R_NEGOTIATED_ALPS_WITHOUT_ALPN 308
#define SSL_R_ALPS_MISMATCH_ON_EARLY_DATA 309
#define SSL_R_ECH_SERVER_CONFIG_AND_PRIVATE_KEY_MISMATCH 310
#define SSL_R_ECH_SERVER_CONFIG_UNSUPPORTED_EXTENSION 311
#define SSL_R_UNSUPPORTED_ECH_SERVER_CONFIG 312
#define SSL_R_ECH_SERVER_WOULD_HAVE_NO_RETRY_CONFIGS 313
#define SSL_R_INVALID_CLIENT_HELLO_INNER 314
#define SSL_R_INVALID_ALPN_PROTOCOL_LIST 315
#define SSL_R_COULD_NOT_PARSE_HINTS 316
#define SSL_R_INVALID_ECH_PUBLIC_NAME 317
#define SSL_R_INVALID_ECH_CONFIG_LIST 318
#define SSL_R_ECH_REJECTED 319
#define SSL_R_INVALID_OUTER_EXTENSION 320
#define SSL_R_INCONSISTENT_ECH_NEGOTIATION 321
#define SSL_R_INVALID_ALPS_CODEPOINT 322
#define SSL_R_NO_MATCHING_ISSUER 323
#define SSL_R_INVALID_SPAKE2PLUSV1_VALUE 324
#define SSL_R_PAKE_EXHAUSTED 325
#define SSL_R_PEER_PAKE_MISMATCH 326
#define SSL_R_UNSUPPORTED_CREDENTIAL_LIST 327
#define SSL_R_INVALID_TRUST_ANCHOR_LIST 328
#define SSL_R_INVALID_CERTIFICATE_PROPERTY_LIST 329
#define SSL_R_DUPLICATE_GROUP 330
#define SSL_R_INVALID_PSK_FOR_CONNECTION 331
#define SSL_R_NO_SUPPORTED_PSK_MODE 332
#define SSL_R_INVALID_CERT_TYPES_LIST 333
#define SSL_R_UNSUPPORTED_CERTIFICATE 334
#define SSL_R_MISSING_KEY 335
#define SSL_R_INVALID_RAW_PUBLIC_KEY 336
#define SSL_R_UNUSABLE_ECH_CONFIG_LIST 337
#define SSL_R_INVALID_CIPHER_FLAGS 338
#define SSL_R_DUPLICATE_CIPHER 339
#define SSL_R_INVALID_TRUST_ANCHOR_ID 340
#define SSL_R_SSLV3_ALERT_CLOSE_NOTIFY 1000
#define SSL_R_SSLV3_ALERT_UNEXPECTED_MESSAGE 1010
#define SSL_R_SSLV3_ALERT_BAD_RECORD_MAC 1020
#define SSL_R_TLSV1_ALERT_DECRYPTION_FAILED 1021
#define SSL_R_TLSV1_ALERT_RECORD_OVERFLOW 1022
#define SSL_R_SSLV3_ALERT_DECOMPRESSION_FAILURE 1030
#define SSL_R_SSLV3_ALERT_HANDSHAKE_FAILURE 1040
#define SSL_R_SSLV3_ALERT_NO_CERTIFICATE 1041
#define SSL_R_SSLV3_ALERT_BAD_CERTIFICATE 1042
#define SSL_R_SSLV3_ALERT_UNSUPPORTED_CERTIFICATE 1043
#define SSL_R_SSLV3_ALERT_CERTIFICATE_REVOKED 1044
#define SSL_R_SSLV3_ALERT_CERTIFICATE_EXPIRED 1045
#define SSL_R_SSLV3_ALERT_CERTIFICATE_UNKNOWN 1046
#define SSL_R_SSLV3_ALERT_ILLEGAL_PARAMETER 1047
#define SSL_R_TLSV1_ALERT_UNKNOWN_CA 1048
#define SSL_R_TLSV1_ALERT_ACCESS_DENIED 1049
#define SSL_R_TLSV1_ALERT_DECODE_ERROR 1050
#define SSL_R_TLSV1_ALERT_DECRYPT_ERROR 1051
#define SSL_R_TLSV1_ALERT_EXPORT_RESTRICTION 1060
#define SSL_R_TLSV1_ALERT_PROTOCOL_VERSION 1070
#define SSL_R_TLSV1_ALERT_INSUFFICIENT_SECURITY 1071
#define SSL_R_TLSV1_ALERT_INTERNAL_ERROR 1080
#define SSL_R_TLSV1_ALERT_INAPPROPRIATE_FALLBACK 1086
#define SSL_R_TLSV1_ALERT_USER_CANCELLED 1090
#define SSL_R_TLSV1_ALERT_NO_RENEGOTIATION 1100
#define SSL_R_TLSV1_ALERT_UNSUPPORTED_EXTENSION 1110
#define SSL_R_TLSV1_ALERT_CERTIFICATE_UNOBTAINABLE 1111
#define SSL_R_TLSV1_ALERT_UNRECOGNIZED_NAME 1112
#define SSL_R_TLSV1_ALERT_BAD_CERTIFICATE_STATUS_RESPONSE 1113
#define SSL_R_TLSV1_ALERT_BAD_CERTIFICATE_HASH_VALUE 1114
#define SSL_R_TLSV1_ALERT_UNKNOWN_PSK_IDENTITY 1115
#define SSL_R_TLSV1_ALERT_CERTIFICATE_REQUIRED 1116
#define SSL_R_TLSV1_ALERT_NO_APPLICATION_PROTOCOL 1120
#define SSL_R_TLSV1_ALERT_ECH_REQUIRED 1121

#endif  // OPENSSL_HEADER_SSL_H