// Copyright 2014 The BoringSSL Authors
//
// 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_AEAD_H
#define OPENSSL_HEADER_AEAD_H

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

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


// Authenticated Encryption with Additional Data.
//
// AEAD couples confidentiality and integrity in a single primitive. AEAD
// algorithms take a key and then can seal and open individual messages. Each
// message has a unique, per-message nonce and, optionally, additional data
// which is authenticated but not included in the ciphertext.
//
// The `EVP_AEAD_CTX_init` function initialises an `EVP_AEAD_CTX` structure and
// performs any precomputation needed to use `aead` with `key`. The length of
// the key, `key_len`, is given in bytes.
//
// The `tag_len` argument contains the length of the tags, in bytes, and allows
// for the processing of truncated authenticators. A zero value indicates that
// the default tag length should be used and this is defined as
// `EVP_AEAD_DEFAULT_TAG_LENGTH` in order to make the code clear. Using
// truncated tags increases an attacker's chance of creating a valid forgery.
// Be aware that the attacker's chance may increase more than exponentially as
// would naively be expected.
//
// When no longer needed, the initialised `EVP_AEAD_CTX` structure must be
// passed to `EVP_AEAD_CTX_cleanup`, which will deallocate any memory used.
//
// With an `EVP_AEAD_CTX` in hand, one can seal and open messages. These
// operations are intended to meet the standard notions of privacy and
// authenticity for authenticated encryption. For formal definitions see
// Bellare and Namprempre, "Authenticated encryption: relations among notions
// and analysis of the generic composition paradigm," Lecture Notes in Computer
// Science B<1976> (2000), 531–545,
// http://www-cse.ucsd.edu/~mihir/papers/oem.html.
//
// When sealing messages, a nonce must be given. The length of the nonce is
// fixed by the AEAD in use and is returned by `EVP_AEAD_nonce_length`. *The
// nonce must be unique for all messages with the same key*. This is critically
// important - nonce reuse may completely undermine the security of the AEAD.
// Nonces may be predictable and public, so long as they are unique. Uniqueness
// may be achieved with a simple counter or, if large enough, may be generated
// randomly. The nonce must be passed into the "open" operation by the receiver
// so must either be implicit (e.g. a counter), or must be transmitted along
// with the sealed message.
//
// The "seal" and "open" operations are atomic - an entire message must be
// encrypted or decrypted in a single call. Large messages may have to be split
// up in order to accommodate this. When doing so, be mindful of the need not to
// repeat nonces and the possibility that an attacker could duplicate, reorder
// or drop message chunks. For example, using a single key for a given (large)
// message and sealing chunks with nonces counting from zero would be secure as
// long as the number of chunks was securely transmitted. (Otherwise an
// attacker could truncate the message by dropping chunks from the end.)
//
// The number of chunks could be transmitted by prefixing it to the plaintext,
// for example. This also assumes that no other message would ever use the same
// key otherwise the rule that nonces must be unique for a given key would be
// violated.
//
// The "seal" and "open" operations also permit additional data to be
// authenticated via the `ad` parameter. This data is not included in the
// ciphertext and must be identical for both the "seal" and "open" call. This
// permits implicit context to be authenticated but may be empty if not needed.
//
// The "seal" and "open" operations may work in-place if the `out` and `in`
// arguments are equal. Otherwise, if `out` and `in` alias, input data may be
// overwritten before it is read. This situation will cause an error.
//
// The "seal" and "open" operations return one on success and zero on error.


// AEAD algorithms.

// EVP_aead_aes_128_gcm is AES-128 in Galois Counter Mode.
//
// Note: AES-GCM should only be used with 12-byte (96-bit) nonces. Although it
// is specified to take a variable-length nonce, nonces with other lengths are
// effectively randomized, which means one must consider collisions. Unless
// implementing an existing protocol which has already specified incorrect
// parameters, only use 12-byte nonces.
OPENSSL_EXPORT const EVP_AEAD *EVP_aead_aes_128_gcm(void);

// EVP_aead_aes_192_gcm is AES-192 in Galois Counter Mode.
//
// WARNING: AES-192 is superfluous and shouldn't exist. NIST should never have
// defined it. Use only when interop with another system requires it, never
// de novo.
//
// Note: AES-GCM should only be used with 12-byte (96-bit) nonces. Although it
// is specified to take a variable-length nonce, nonces with other lengths are
// effectively randomized, which means one must consider collisions. Unless
// implementing an existing protocol which has already specified incorrect
// parameters, only use 12-byte nonces.
OPENSSL_EXPORT const EVP_AEAD *EVP_aead_aes_192_gcm(void);

// EVP_aead_aes_256_gcm is AES-256 in Galois Counter Mode.
//
// Note: AES-GCM should only be used with 12-byte (96-bit) nonces. Although it
// is specified to take a variable-length nonce, nonces with other lengths are
// effectively randomized, which means one must consider collisions. Unless
// implementing an existing protocol which has already specified incorrect
// parameters, only use 12-byte nonces.
OPENSSL_EXPORT const EVP_AEAD *EVP_aead_aes_256_gcm(void);

// EVP_aead_chacha20_poly1305 is the AEAD built from ChaCha20 and
// Poly1305 as described in RFC 8439.
OPENSSL_EXPORT const EVP_AEAD *EVP_aead_chacha20_poly1305(void);

// EVP_aead_xchacha20_poly1305 is ChaCha20-Poly1305 with an extended nonce that
// makes random generation of nonces safe.
OPENSSL_EXPORT const EVP_AEAD *EVP_aead_xchacha20_poly1305(void);

// EVP_aead_aes_128_ctr_hmac_sha256 is AES-128 in CTR mode with HMAC-SHA256 for
// authentication. The nonce is 12 bytes; the bottom 32-bits are used as the
// block counter, thus the maximum plaintext size is 64GB.
OPENSSL_EXPORT const EVP_AEAD *EVP_aead_aes_128_ctr_hmac_sha256(void);

// EVP_aead_aes_256_ctr_hmac_sha256 is AES-256 in CTR mode with HMAC-SHA256 for
// authentication. See `EVP_aead_aes_128_ctr_hmac_sha256` for details.
OPENSSL_EXPORT const EVP_AEAD *EVP_aead_aes_256_ctr_hmac_sha256(void);

// EVP_aead_aes_128_gcm_siv is AES-128 in GCM-SIV mode. See RFC 8452.
OPENSSL_EXPORT const EVP_AEAD *EVP_aead_aes_128_gcm_siv(void);

// EVP_aead_aes_256_gcm_siv is AES-256 in GCM-SIV mode. See RFC 8452.
OPENSSL_EXPORT const EVP_AEAD *EVP_aead_aes_256_gcm_siv(void);

// EVP_aead_aes_128_gcm_randnonce is AES-128 in Galois Counter Mode with
// internal nonce generation. The 12-byte nonce is appended to the tag
// and is generated internally. The "tag", for the purpurses of the API, is thus
// 12 bytes larger. The nonce parameter when using this AEAD must be
// zero-length. Since the nonce is random, a single key should not be used for
// more than 2^32 seal operations.
//
// Warning: this is for use for FIPS compliance only. It is probably not
// suitable for other uses. Using standard AES-GCM AEADs allows one to achieve
// the same effect, but gives more control over nonce storage.
OPENSSL_EXPORT const EVP_AEAD *EVP_aead_aes_128_gcm_randnonce(void);

// EVP_aead_aes_256_gcm_randnonce is AES-256 in Galois Counter Mode with
// internal nonce generation. The 12-byte nonce is appended to the tag
// and is generated internally. The "tag", for the purpurses of the API, is thus
// 12 bytes larger. The nonce parameter when using this AEAD must be
// zero-length. Since the nonce is random, a single key should not be used for
// more than 2^32 seal operations.
//
// Warning: this is for use for FIPS compliance only. It is probably not
// suitable for other uses. Using standard AES-GCM AEADs allows one to achieve
// the same effect, but gives more control over nonce storage.
OPENSSL_EXPORT const EVP_AEAD *EVP_aead_aes_256_gcm_randnonce(void);

// EVP_aead_aes_128_ccm_bluetooth is AES-128-CCM with M=4 and L=2 (4-byte tags
// and 13-byte nonces), as described in the Bluetooth Core Specification v5.0,
// Volume 6, Part E, Section 1.
OPENSSL_EXPORT const EVP_AEAD *EVP_aead_aes_128_ccm_bluetooth(void);

// EVP_aead_aes_128_ccm_bluetooth_8 is AES-128-CCM with M=8 and L=2 (8-byte tags
// and 13-byte nonces), as used in the Bluetooth Mesh Networking Specification
// v1.0.
OPENSSL_EXPORT const EVP_AEAD *EVP_aead_aes_128_ccm_bluetooth_8(void);

// EVP_aead_aes_128_ccm_matter is AES-128-CCM with M=16 and L=2 (16-byte tags
// and 13-byte nonces), as used in the Matter specification.
OPENSSL_EXPORT const EVP_AEAD *EVP_aead_aes_128_ccm_matter(void);

// EVP_has_aes_hardware returns one if we enable hardware support for fast and
// constant-time AES-GCM.
OPENSSL_EXPORT int EVP_has_aes_hardware(void);

// EVP_aead_aes_128_eax is AES-128 in EAX mode. Nonce size is either 12 or 16
// bytes, tag length is 16 bytes.
// See https://doi.org/10.1007/978-3-540-25937-4_25.
OPENSSL_EXPORT const EVP_AEAD *EVP_aead_aes_128_eax(void);

// EVP_aead_aes_256_eax is AES-256 in EAX mode. Nonce size is either 12 or 16
// bytes, tag length is 16 bytes.
// See https://doi.org/10.1007/978-3-540-25937-4_25.
OPENSSL_EXPORT const EVP_AEAD *EVP_aead_aes_256_eax(void);


// Utility functions.

// EVP_AEAD_key_length returns the length, in bytes, of the keys used by
// `aead`.
OPENSSL_EXPORT size_t EVP_AEAD_key_length(const EVP_AEAD *aead);

// EVP_AEAD_nonce_length returns the length, in bytes, of the per-message nonce
// for `aead`.
OPENSSL_EXPORT size_t EVP_AEAD_nonce_length(const EVP_AEAD *aead);

// EVP_AEAD_max_overhead returns the maximum number of additional bytes added
// by the act of sealing data with `aead`.
OPENSSL_EXPORT size_t EVP_AEAD_max_overhead(const EVP_AEAD *aead);

// EVP_AEAD_max_tag_len returns the maximum tag length when using `aead`. This
// is the largest value that can be passed as `tag_len` to
// `EVP_AEAD_CTX_init`.
OPENSSL_EXPORT size_t EVP_AEAD_max_tag_len(const EVP_AEAD *aead);


// AEAD operations.

union evp_aead_ctx_st_state {
  uint8_t opaque[560];
  uint64_t alignment;
};

// An evp_aead_ctx_st (typedefed as `EVP_AEAD_CTX` in base.h) represents an AEAD
// algorithm configured with a specific key and message-independent IV.
struct evp_aead_ctx_st {
  const EVP_AEAD *aead;
  union evp_aead_ctx_st_state state;
  // tag_len may contain the actual length of the authentication tag if it is
  // known at initialization time.
  uint8_t tag_len;
};

// EVP_AEAD_MAX_KEY_LENGTH contains the maximum key length used by
// any AEAD defined in this header.
#define EVP_AEAD_MAX_KEY_LENGTH 80

// EVP_AEAD_MAX_NONCE_LENGTH contains the maximum nonce length used by
// any AEAD defined in this header.
#define EVP_AEAD_MAX_NONCE_LENGTH 24

// EVP_AEAD_MAX_OVERHEAD contains the maximum overhead used by any AEAD
// defined in this header.
#define EVP_AEAD_MAX_OVERHEAD 64

// EVP_AEAD_MAX_OPEN_OVERHEAD contains the maximum overhead that any AEAD
// defined in this header can remove - even if no AEAD actually generates that
// much, as non-canonical paddings exist (such as in TLS which allows 256 bytes
// padding + 64 bytes MAC).
#define EVP_AEAD_MAX_OPEN_OVERHEAD 320

// EVP_AEAD_DEFAULT_TAG_LENGTH is a magic value that can be passed to
// EVP_AEAD_CTX_init to indicate that the default tag length for an AEAD should
// be used.
#define EVP_AEAD_DEFAULT_TAG_LENGTH 0

// EVP_AEAD_CTX_zero sets an uninitialized `ctx` to the zero state. It must be
// initialized with `EVP_AEAD_CTX_init` before use. It is safe, but not
// necessary, to call `EVP_AEAD_CTX_cleanup` in this state. This may be used for
// more uniform cleanup of `EVP_AEAD_CTX`.
OPENSSL_EXPORT void EVP_AEAD_CTX_zero(EVP_AEAD_CTX *ctx);

// EVP_AEAD_CTX_new allocates an `EVP_AEAD_CTX`, calls `EVP_AEAD_CTX_init` and
// returns the `EVP_AEAD_CTX`, or NULL on error.
OPENSSL_EXPORT EVP_AEAD_CTX *EVP_AEAD_CTX_new(const EVP_AEAD *aead,
                                              const uint8_t *key,
                                              size_t key_len, size_t tag_len);

// EVP_AEAD_CTX_free calls `EVP_AEAD_CTX_cleanup` and `OPENSSL_free` on
// `ctx`.
OPENSSL_EXPORT void EVP_AEAD_CTX_free(EVP_AEAD_CTX *ctx);

// EVP_AEAD_CTX_init initializes `ctx` for the given AEAD algorithm. The `impl`
// argument is ignored and should be NULL. Authentication tags may be truncated
// by passing a size as `tag_len`. A `tag_len` of zero indicates the default
// tag length and this is defined as EVP_AEAD_DEFAULT_TAG_LENGTH for
// readability.
//
// Returns 1 on success. Otherwise returns 0 and pushes to the error stack. In
// the error case, you do not need to call `EVP_AEAD_CTX_cleanup`, but it's
// harmless to do so.
OPENSSL_EXPORT int EVP_AEAD_CTX_init(EVP_AEAD_CTX *ctx, const EVP_AEAD *aead,
                                     const uint8_t *key, size_t key_len,
                                     size_t tag_len, ENGINE *impl);

// EVP_AEAD_CTX_cleanup frees any data allocated by `ctx`. It is a no-op to
// call `EVP_AEAD_CTX_cleanup` on a `EVP_AEAD_CTX` that has been `memset` to
// all zeros.
OPENSSL_EXPORT void EVP_AEAD_CTX_cleanup(EVP_AEAD_CTX *ctx);

// EVP_AEAD_CTX_seal encrypts and authenticates `in_len` bytes from `in` and
// authenticates `ad_len` bytes from `ad` and writes the result to `out`. It
// returns one on success and zero otherwise.
//
// This function may be called concurrently with itself or any other seal/open
// function on the same `EVP_AEAD_CTX`.
//
// At most `max_out_len` bytes are written to `out` and, in order to ensure
// success, `max_out_len` should be `in_len` plus the result of
// `EVP_AEAD_max_overhead`. On successful return, `*out_len` is set to the
// actual number of bytes written.
//
// The length of `nonce`, `nonce_len`, must be equal to the result of
// `EVP_AEAD_nonce_length` for this AEAD.
//
// `EVP_AEAD_CTX_seal` never results in a partial output. If `max_out_len` is
// insufficient, zero will be returned. If any error occurs, `out` will be
// filled with zero bytes and `*out_len` set to zero.
//
// If `in` and `out` alias then `out` must be == `in`.
OPENSSL_EXPORT int EVP_AEAD_CTX_seal(const EVP_AEAD_CTX *ctx, uint8_t *out,
                                     size_t *out_len, size_t max_out_len,
                                     const uint8_t *nonce, size_t nonce_len,
                                     const uint8_t *in, size_t in_len,
                                     const uint8_t *ad, size_t ad_len);

// EVP_AEAD_CTX_open authenticates `in_len` bytes from `in` and `ad_len` bytes
// from `ad` and decrypts at most `in_len` bytes into `out`. It returns one on
// success and zero otherwise.
//
// This function may be called concurrently with itself or any other seal/open
// function on the same `EVP_AEAD_CTX`.
//
// At most `in_len` bytes are written to `out`. In order to ensure success,
// `max_out_len` should be at least `in_len`. On successful return, `*out_len`
// is set to the actual number of bytes written.
//
// The length of `nonce`, `nonce_len`, must be equal to the result of
// `EVP_AEAD_nonce_length` for this AEAD.
//
// `EVP_AEAD_CTX_open` never results in a partial output. If `max_out_len` is
// insufficient, zero will be returned. If any error occurs, `out` will be
// filled with zero bytes and `*out_len` set to zero.
//
// If `in` and `out` alias then `out` must be == `in`.
OPENSSL_EXPORT int EVP_AEAD_CTX_open(const EVP_AEAD_CTX *ctx, uint8_t *out,
                                     size_t *out_len, size_t max_out_len,
                                     const uint8_t *nonce, size_t nonce_len,
                                     const uint8_t *in, size_t in_len,
                                     const uint8_t *ad, size_t ad_len);

// EVP_AEAD_CTX_seal_scatter encrypts and authenticates `in_len` bytes from `in`
// and authenticates `ad_len` bytes from `ad`. It writes `in_len` bytes of
// ciphertext to `out` and the authentication tag to `out_tag`. It returns one
// on success and zero otherwise.
//
// This function may be called concurrently with itself or any other seal/open
// function on the same `EVP_AEAD_CTX`.
//
// Exactly `in_len` bytes are written to `out`, and up to
// `EVP_AEAD_max_overhead+extra_in_len` bytes to `out_tag`. On successful
// return, `*out_tag_len` is set to the actual number of bytes written to
// `out_tag`.
//
// `extra_in` may point to an additional plaintext input buffer if the cipher
// supports it. If present, `extra_in_len` additional bytes of plaintext are
// encrypted and authenticated, and the ciphertext is written (before the tag)
// to `out_tag`. `max_out_tag_len` must be sized to allow for the additional
// `extra_in_len` bytes.
//
// The length of `nonce`, `nonce_len`, must be equal to the result of
// `EVP_AEAD_nonce_length` for this AEAD.
//
// `EVP_AEAD_CTX_seal_scatter` never results in a partial output. If
// `max_out_tag_len` is insufficient, zero will be returned. If any error
// occurs, `out` and `out_tag` will be filled with zero bytes and `*out_tag_len`
// set to zero.
//
// If `in` and `out` alias then `out` must be == `in`. `out_tag` may not alias
// any other argument.
OPENSSL_EXPORT int EVP_AEAD_CTX_seal_scatter(
    const EVP_AEAD_CTX *ctx, uint8_t *out, uint8_t *out_tag,
    size_t *out_tag_len, size_t max_out_tag_len, const uint8_t *nonce,
    size_t nonce_len, const uint8_t *in, size_t in_len, const uint8_t *extra_in,
    size_t extra_in_len, const uint8_t *ad, size_t ad_len);

// EVP_AEAD_CTX_open_gather decrypts and authenticates `in_len` bytes from `in`
// and authenticates `ad_len` bytes from `ad` using `in_tag_len` bytes of
// authentication tag from `in_tag`. If successful, it writes `in_len` bytes of
// plaintext to `out`. It returns one on success and zero otherwise.
//
// This function may be called concurrently with itself or any other seal/open
// function on the same `EVP_AEAD_CTX`.
//
// The length of `nonce`, `nonce_len`, must be equal to the result of
// `EVP_AEAD_nonce_length` for this AEAD.
//
// `EVP_AEAD_CTX_open_gather` never results in a partial output. If any error
// occurs, `out` will be filled with zero bytes.
//
// If `in` and `out` alias then `out` must be == `in`.
OPENSSL_EXPORT int EVP_AEAD_CTX_open_gather(
    const EVP_AEAD_CTX *ctx, uint8_t *out, const uint8_t *nonce,
    size_t nonce_len, const uint8_t *in, size_t in_len, const uint8_t *in_tag,
    size_t in_tag_len, const uint8_t *ad, size_t ad_len);

// crypto_ivec_st (aka `CRYPTO_IVEC`) combines a pointer to input data with its
// length. It is usually passed as an array of length of at most
// `CRYPTO_IOVEC_MAX`.
struct crypto_ivec_st {
  const uint8_t *in;
  size_t len;
};

// crypto_iovec_st (aka `CRYPTO_IOVEC` combines a pointer to input data and a
// pointer to an output buffer with their common length. It is usually passed
// as an array of length of at most `CRYPTO_IOVEC_MAX`.
struct crypto_iovec_st {
  // `out` and `in` must be disjoint or equal
  uint8_t *out;
  const uint8_t *in;
  size_t len;
};

// CRYPTO_IOVEC_MAX is the maximum number of entries in an `CRYPTO_IOVEC` or
// `CRYPTO_IVEC` parameter.
#define CRYPTO_IOVEC_MAX 16

// EVP_AEAD_CTX_sealv encrypts and authenticates the `in` bytes from `iovec`
// and authenticates the `aadvec` bytes. It writes the same amount of
// ciphertext to the `out` pointers of `iovec` and the authentication tag to
// `out_tag`. It returns one on success and zero otherwise.
//
// This function computes the same output as `EVP_AEAD_CTX_seal_scatter`, but
// without requiring the input or output to be a contiguous buffer. The
// individual input and output pieces are logically concatenated for a single
// operation; their boundaries are not semantically significant and will not
// impact the output.
//
// This function may be called concurrently with itself or any other seal/open
// function on the same `EVP_AEAD_CTX`.
//
// Exactly `len` bytes are written to each `out` member of the `iovec`, and up
// to `EVP_AEAD_max_overhead+extra_in_len` bytes to `out_tag`. On successful
// return, `*out_tag_len` is set to the actual number of bytes written to
// `out_tag`.
//
// The length of `nonce`, `nonce_len`, must be equal to the result of
// `EVP_AEAD_nonce_length` for this AEAD.
//
// `EVP_AEAD_CTX_sealv` never results in a partial output. If `max_out_tag_len`
// is insufficient, zero will be returned. If any error occurs, the `out`
// members of the `iovec` and `out_tag` will be filled with zero bytes and
// `*out_tag_len` set to zero.
//
// No output pointer may alias any other pointer passed to this function either
// directly or via `iovec` and `aadvec`, with the one exception that it is
// permitted for the same `iovec` member's `in` and `out` members to be equal
// (in-place operation).
//
// `num_iovec` and `num_aadvec` must be <= `CRYPTO_IOVEC_MAX`.
OPENSSL_EXPORT
int EVP_AEAD_CTX_sealv(const EVP_AEAD_CTX *ctx, const CRYPTO_IOVEC *iovec,
                       size_t num_iovec, uint8_t *out_tag, size_t *out_tag_len,
                       size_t max_out_tag_len, const uint8_t *nonce,
                       size_t nonce_len, const CRYPTO_IVEC *aadvec,
                       size_t num_aadvec);

// EVP_AEAD_CTX_openv authenticates the `in` bytes from `iovec` and `aadvec`,
// and decrypts the `in` bytes to the `out` pointers of `iovec`. It returns one
// on success and zero otherwise.
//
// This function computes the same output as `EVP_AEAD_CTX_open`, but without
// requiring the input or output to be a contiguous buffer. The individual
// input and output pieces are logically concatenated for a single operation;
// their boundaries are not semantically significant and will not impact the
// output.
//
// This function may (and usually will) output less than the total length of
// `iovec`. In this case, it outputs to a prefix of `iovec`'s output space,
// then returns the length of what was actually written.
//
// In AEADs with a fixed-length authentication tag, the tag is treated as if it
// were appended to the ciphertext, and successful outputs will always be
// exactly the tag length shorter. To open with a separate, detached tag,
// either provide it as a separate `CRYPTO_IOVEC`, or use
// `EVP_AEAD_CTX_openv_detached`. The latter may be more convenient, one does
// not need consider the possibility of output to the final `CRYPTO_IOVEC`.
//
// This function may be called concurrently with itself or any other seal/open
// function on the same `EVP_AEAD_CTX`.
//
// The length of `nonce`, `nonce_len`, must be equal to the result of
// `EVP_AEAD_nonce_length` for this AEAD.
//
// `EVP_AEAD_CTX_openv` never results in a partial output. If any error occurs,
// `out` will be filled with zero bytes and `*out_len` set to zero.
//
// No output pointer may alias any other pointer passed to this function either
// directly or via `iovec` and `aadvec`, with the one exception that it is
// permitted for the same `iovec` member's `in` and `out` members to be equal
// (in-place operation).
//
// `num_iovec` and `num_aadvec` must be <= `CRYPTO_IOVEC_MAX`.
OPENSSL_EXPORT
int EVP_AEAD_CTX_openv(const EVP_AEAD_CTX *ctx, const CRYPTO_IOVEC *iovec,
                       size_t num_iovec, size_t *out_total_bytes,
                       const uint8_t *nonce, size_t nonce_len,
                       const CRYPTO_IVEC *aadvec, size_t num_aadvec);

// EVP_AEAD_CTX_openv_detached authenticates the `in` bytes from `iovec` and
// `aadvec` using `in_tag_len` bytes of authentication tag from `in_tag`. If
// successful, it writes the plaintext of the `in` bytes to the `out` pointers
// of `iovec`. It returns one on success and zero otherwise.
//
// This function is usable with AEADs whose output can be split into a
// ciphertext portion, with the same length as the plaintext, and a
// fixed-length authentication tag. If the AEAD has a variable-length overhead,
// this function will return zero. Such AEADs can only be used with
// `EVP_AEAD_CTX_openv`.
//
// This function computes the same output as `EVP_AEAD_CTX_open`, but with a
// detached tag and without requiring the input or output to be a contiguous
// buffer. The individual input and output pieces are logically concatenated
// for a single operation; their boundaries are not semantically significant
// and will not impact the output.
//
// This function may be called concurrently with itself or any other seal/open
// function on the same `EVP_AEAD_CTX`.
//
// The length of `nonce`, `nonce_len`, must be equal to the result of
// `EVP_AEAD_nonce_length` for this AEAD.
//
// `EVP_AEAD_CTX_openv_detached` never results in a partial output. If any
// error occurs, `out` will be filled with zero bytes.
//
// No output pointer may alias any other pointer passed to this function either
// directly or via `iovec` and `aadvec`, with the one exception that it is
// permitted for the same `iovec` member's `in` and `out` members to be equal
// (in-place operation).
//
// `num_iovec` and `num_aadvec` must be <= `CRYPTO_IOVEC_MAX`.
OPENSSL_EXPORT
int EVP_AEAD_CTX_openv_detached(const EVP_AEAD_CTX *ctx,
                                const CRYPTO_IOVEC *iovec, size_t num_iovec,
                                const uint8_t *nonce, size_t nonce_len,
                                const uint8_t *in_tag, size_t in_tag_len,
                                const CRYPTO_IVEC *aadvec, size_t num_aadvec);

// EVP_AEAD_CTX_aead returns the underlying AEAD for `ctx`, or NULL if one has
// not been set.
OPENSSL_EXPORT const EVP_AEAD *EVP_AEAD_CTX_aead(const EVP_AEAD_CTX *ctx);


// TLS-specific AEAD algorithms.
//
// WARNING: These `EVP_AEAD` objects primitives do not meet the definition of
// generic AEADs. They are all specific to TLS and should not be used outside of
// that context. They break the usual guarantees around `EVP_AEAD_CTX`,
// including statefulness, thread-safety, initialization conventions, and
// security requirements around the nonce parameter.

// The following functions implement legacy TLS CBC cipher suites.
//
// WARNING: These functions are effectively internal implementation details of
// libssl, not general-purpose constructions. They are not true AEADs and differ
// from a normal `EVP_AEAD` in many ways:
//
// * They must be initialized with `EVP_AEAD_CTX_init_with_direction`, not
//   `EVP_AEAD_CTX_init`.
//
// * The resulting `EVP_AEAD_CTX`s are stateful. Neither `EVP_AEAD_CTX_open*`
//   nor `EVP_AEAD_CTX_seal*` can be called concurrently.
//
// * The `ad` parameter must have length 11 (the standard TLS one with length
//   omitted).
//
// * The `nonce` parameter is used as a CBC IV and must be unpredictable, not
//   just unique.
//
// * The `*_implicit_iv` variants implicitly set the IV to the last block of the
//   previous message. They are vulnerable the BEAST attack unless the caller
//   applies record-splitting mitigations externally.
OPENSSL_EXPORT const EVP_AEAD *EVP_aead_aes_128_cbc_sha1_tls(void);
OPENSSL_EXPORT const EVP_AEAD *EVP_aead_aes_128_cbc_sha1_tls_implicit_iv(void);
OPENSSL_EXPORT const EVP_AEAD *EVP_aead_aes_128_cbc_sha256_tls(void);
OPENSSL_EXPORT const EVP_AEAD *EVP_aead_aes_256_cbc_sha1_tls(void);
OPENSSL_EXPORT const EVP_AEAD *EVP_aead_aes_256_cbc_sha1_tls_implicit_iv(void);
OPENSSL_EXPORT const EVP_AEAD *EVP_aead_des_ede3_cbc_sha1_tls(void);
OPENSSL_EXPORT const EVP_AEAD *EVP_aead_des_ede3_cbc_sha1_tls_implicit_iv(void);

// The following functions behave like `EVP_aead_aes_128_gcm` or
// `EVP_aead_aes_256_gcm`, except that seal operations fail if nonces do not
// match the TLS 1.2 or TLS 1.3 nonce construction.
//
// These functions are only applicable for callers that want an extra AEAD-level
// nonce check. `EVP_aead_aes_128_gcm` and `EVP_aead_aes_256_gcm` are otherwise
// suitable for implementing TLS and will produce the same output.
//
// WARNING: `EVP_AEAD_CTX` objects initialized with these `EVP_AEAD`s are
// stateful. `EVP_AEAD_CTX_seal*` cannot be called concurrently.
OPENSSL_EXPORT const EVP_AEAD *EVP_aead_aes_128_gcm_tls12(void);
OPENSSL_EXPORT const EVP_AEAD *EVP_aead_aes_256_gcm_tls12(void);
OPENSSL_EXPORT const EVP_AEAD *EVP_aead_aes_128_gcm_tls13(void);
OPENSSL_EXPORT const EVP_AEAD *EVP_aead_aes_256_gcm_tls13(void);


// Obscure functions.

// evp_aead_direction_t denotes the direction of an AEAD operation.
enum evp_aead_direction_t {
  evp_aead_open,
  evp_aead_seal,
};

// EVP_AEAD_CTX_init_with_direction calls `EVP_AEAD_CTX_init` for normal
// AEADs. For TLS-specific AEADs, it initializes `ctx` for a given direction.
OPENSSL_EXPORT int EVP_AEAD_CTX_init_with_direction(
    EVP_AEAD_CTX *ctx, const EVP_AEAD *aead, const uint8_t *key, size_t key_len,
    size_t tag_len, enum evp_aead_direction_t dir);

// EVP_AEAD_CTX_get_iv sets `*out_len` to the length of the IV for `ctx` and
// sets `*out_iv` to point to that many bytes of the current IV. This is only
// meaningful for AEADs with implicit IVs (i.e. CBC mode in TLS 1.0).
//
// It returns one on success or zero on error.
OPENSSL_EXPORT int EVP_AEAD_CTX_get_iv(const EVP_AEAD_CTX *ctx,
                                       const uint8_t **out_iv, size_t *out_len);

// EVP_AEAD_CTX_tag_len computes the exact byte length of the tag written by
// `EVP_AEAD_CTX_seal_scatter` and writes it to `*out_tag_len`. It returns one
// on success or zero on error. `in_len` and `extra_in_len` must equal the
// arguments of the same names passed to `EVP_AEAD_CTX_seal_scatter`.
//
// To compute the exact byte length of the output written by
// `EVP_AEAD_CTX_seal`, set `extra_in_len` to zero and add `in_len` to the
// result.
//
// To compute the exact byte length of the tag written by `EVP_AEAD_CTX_sealv`,
// set `in_len` to the sum of `len` over the entire `iovec`, and set
// `extra_in_len` to zero.
OPENSSL_EXPORT int EVP_AEAD_CTX_tag_len(const EVP_AEAD_CTX *ctx,
                                        size_t *out_tag_len,
                                        const size_t in_len,
                                        const size_t extra_in_len);


#if defined(__cplusplus)
}  // extern C

#if !defined(BORINGSSL_NO_CXX)
extern "C++" {

BSSL_NAMESPACE_BEGIN

using ScopedEVP_AEAD_CTX =
    internal::StackAllocated<EVP_AEAD_CTX, void, EVP_AEAD_CTX_zero,
                             EVP_AEAD_CTX_cleanup>;

BORINGSSL_MAKE_DELETER(EVP_AEAD_CTX, EVP_AEAD_CTX_free)

BSSL_NAMESPACE_END

}  // extern C++
#endif

#endif

#endif  // OPENSSL_HEADER_AEAD_H