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/* Copyright (c) 2016, Google Inc.
*
* Permission to use, copy, modify, and/or distribute this software for any
* purpose with or without fee is hereby granted, provided that the above
* copyright notice and this permission notice appear in all copies.
*
* THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
* WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
* MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY
* SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
* WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN ACTION
* OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF OR IN
* CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE. */
#include <openssl/ssl.h>
#include <assert.h>
#include <string.h>
#include <utility>
#include <openssl/aead.h>
#include <openssl/bytestring.h>
#include <openssl/digest.h>
#include <openssl/hkdf.h>
#include <openssl/hmac.h>
#include <openssl/mem.h>
#include "../crypto/internal.h"
#include "internal.h"
namespace bssl {
static int init_key_schedule(SSL_HANDSHAKE *hs, uint16_t version,
const SSL_CIPHER *cipher) {
if (!hs->transcript.InitHash(version, cipher)) {
return 0;
}
hs->hash_len = hs->transcript.DigestLen();
// Initialize the secret to the zero key.
OPENSSL_memset(hs->secret, 0, hs->hash_len);
return 1;
}
int tls13_init_key_schedule(SSL_HANDSHAKE *hs, const uint8_t *psk,
size_t psk_len) {
if (!init_key_schedule(hs, ssl_protocol_version(hs->ssl), hs->new_cipher)) {
return 0;
}
hs->transcript.FreeBuffer();
return HKDF_extract(hs->secret, &hs->hash_len, hs->transcript.Digest(), psk,
psk_len, hs->secret, hs->hash_len);
}
int tls13_init_early_key_schedule(SSL_HANDSHAKE *hs, const uint8_t *psk,
size_t psk_len) {
SSL *const ssl = hs->ssl;
return init_key_schedule(hs, ssl_session_protocol_version(ssl->session),
ssl->session->cipher) &&
HKDF_extract(hs->secret, &hs->hash_len, hs->transcript.Digest(), psk,
psk_len, hs->secret, hs->hash_len);
}
static int hkdf_expand_label(uint8_t *out, const EVP_MD *digest,
const uint8_t *secret, size_t secret_len,
const char *label, size_t label_len,
const uint8_t *hash, size_t hash_len, size_t len) {
static const char kTLS13LabelVersion[] = "tls13 ";
ScopedCBB cbb;
CBB child;
uint8_t *hkdf_label;
size_t hkdf_label_len;
if (!CBB_init(cbb.get(), 2 + 1 + strlen(kTLS13LabelVersion) + label_len + 1 +
hash_len) ||
!CBB_add_u16(cbb.get(), len) ||
!CBB_add_u8_length_prefixed(cbb.get(), &child) ||
!CBB_add_bytes(&child, (const uint8_t *)kTLS13LabelVersion,
strlen(kTLS13LabelVersion)) ||
!CBB_add_bytes(&child, (const uint8_t *)label, label_len) ||
!CBB_add_u8_length_prefixed(cbb.get(), &child) ||
!CBB_add_bytes(&child, hash, hash_len) ||
!CBB_finish(cbb.get(), &hkdf_label, &hkdf_label_len)) {
return 0;
}
int ret = HKDF_expand(out, len, digest, secret, secret_len, hkdf_label,
hkdf_label_len);
OPENSSL_free(hkdf_label);
return ret;
}
static const char kTLS13LabelDerived[] = "derived";
int tls13_advance_key_schedule(SSL_HANDSHAKE *hs, const uint8_t *in,
size_t len) {
uint8_t derive_context[EVP_MAX_MD_SIZE];
unsigned derive_context_len;
if (!EVP_Digest(nullptr, 0, derive_context, &derive_context_len,
hs->transcript.Digest(), nullptr)) {
return 0;
}
if (!hkdf_expand_label(hs->secret, hs->transcript.Digest(), hs->secret,
hs->hash_len, kTLS13LabelDerived,
strlen(kTLS13LabelDerived), derive_context,
derive_context_len, hs->hash_len)) {
return 0;
}
return HKDF_extract(hs->secret, &hs->hash_len, hs->transcript.Digest(), in,
len, hs->secret, hs->hash_len);
}
// derive_secret derives a secret of length |len| and writes the result in |out|
// with the given label and the current base secret and most recently-saved
// handshake context. It returns one on success and zero on error.
static int derive_secret(SSL_HANDSHAKE *hs, uint8_t *out, size_t len,
const char *label, size_t label_len) {
uint8_t context_hash[EVP_MAX_MD_SIZE];
size_t context_hash_len;
if (!hs->transcript.GetHash(context_hash, &context_hash_len)) {
return 0;
}
return hkdf_expand_label(out, hs->transcript.Digest(), hs->secret,
hs->hash_len, label, label_len, context_hash,
context_hash_len, len);
}
int tls13_set_traffic_key(SSL *ssl, enum evp_aead_direction_t direction,
const uint8_t *traffic_secret,
size_t traffic_secret_len) {
const SSL_SESSION *session = SSL_get_session(ssl);
uint16_t version = ssl_session_protocol_version(session);
if (traffic_secret_len > 0xff) {
OPENSSL_PUT_ERROR(SSL, ERR_R_OVERFLOW);
return 0;
}
// Look up cipher suite properties.
const EVP_AEAD *aead;
size_t discard;
if (!ssl_cipher_get_evp_aead(&aead, &discard, &discard, session->cipher,
version, SSL_is_dtls(ssl))) {
return 0;
}
const EVP_MD *digest = ssl_session_get_digest(session);
// Derive the key.
size_t key_len = EVP_AEAD_key_length(aead);
uint8_t key[EVP_AEAD_MAX_KEY_LENGTH];
if (!hkdf_expand_label(key, digest, traffic_secret, traffic_secret_len, "key",
3, NULL, 0, key_len)) {
return 0;
}
// Derive the IV.
size_t iv_len = EVP_AEAD_nonce_length(aead);
uint8_t iv[EVP_AEAD_MAX_NONCE_LENGTH];
if (!hkdf_expand_label(iv, digest, traffic_secret, traffic_secret_len, "iv",
2, NULL, 0, iv_len)) {
return 0;
}
UniquePtr<SSLAEADContext> traffic_aead =
SSLAEADContext::Create(direction, session->ssl_version, SSL_is_dtls(ssl),
session->cipher, MakeConstSpan(key, key_len),
Span<const uint8_t>(), MakeConstSpan(iv, iv_len));
if (!traffic_aead) {
return 0;
}
if (direction == evp_aead_open) {
if (!ssl->method->set_read_state(ssl, std::move(traffic_aead))) {
return 0;
}
} else {
if (!ssl->method->set_write_state(ssl, std::move(traffic_aead))) {
return 0;
}
}
// Save the traffic secret.
if (direction == evp_aead_open) {
OPENSSL_memmove(ssl->s3->read_traffic_secret, traffic_secret,
traffic_secret_len);
ssl->s3->read_traffic_secret_len = traffic_secret_len;
} else {
OPENSSL_memmove(ssl->s3->write_traffic_secret, traffic_secret,
traffic_secret_len);
ssl->s3->write_traffic_secret_len = traffic_secret_len;
}
return 1;
}
static const char kTLS13LabelExporter[] = "exp master";
static const char kTLS13LabelEarlyExporter[] = "e exp master";
static const char kTLS13LabelClientEarlyTraffic[] = "c e traffic";
static const char kTLS13LabelClientHandshakeTraffic[] = "c hs traffic";
static const char kTLS13LabelServerHandshakeTraffic[] = "s hs traffic";
static const char kTLS13LabelClientApplicationTraffic[] = "c ap traffic";
static const char kTLS13LabelServerApplicationTraffic[] = "s ap traffic";
int tls13_derive_early_secrets(SSL_HANDSHAKE *hs) {
SSL *const ssl = hs->ssl;
if (!derive_secret(hs, hs->early_traffic_secret, hs->hash_len,
kTLS13LabelClientEarlyTraffic,
strlen(kTLS13LabelClientEarlyTraffic)) ||
!ssl_log_secret(ssl, "CLIENT_EARLY_TRAFFIC_SECRET",
hs->early_traffic_secret, hs->hash_len) ||
!derive_secret(hs, ssl->s3->early_exporter_secret, hs->hash_len,
kTLS13LabelEarlyExporter,
strlen(kTLS13LabelEarlyExporter))) {
return 0;
}
ssl->s3->early_exporter_secret_len = hs->hash_len;
return 1;
}
int tls13_derive_handshake_secrets(SSL_HANDSHAKE *hs) {
SSL *const ssl = hs->ssl;
return derive_secret(hs, hs->client_handshake_secret, hs->hash_len,
kTLS13LabelClientHandshakeTraffic,
strlen(kTLS13LabelClientHandshakeTraffic)) &&
ssl_log_secret(ssl, "CLIENT_HANDSHAKE_TRAFFIC_SECRET",
hs->client_handshake_secret, hs->hash_len) &&
derive_secret(hs, hs->server_handshake_secret, hs->hash_len,
kTLS13LabelServerHandshakeTraffic,
strlen(kTLS13LabelServerHandshakeTraffic)) &&
ssl_log_secret(ssl, "SERVER_HANDSHAKE_TRAFFIC_SECRET",
hs->server_handshake_secret, hs->hash_len);
}
int tls13_derive_application_secrets(SSL_HANDSHAKE *hs) {
SSL *const ssl = hs->ssl;
ssl->s3->exporter_secret_len = hs->hash_len;
return derive_secret(hs, hs->client_traffic_secret_0, hs->hash_len,
kTLS13LabelClientApplicationTraffic,
strlen(kTLS13LabelClientApplicationTraffic)) &&
ssl_log_secret(ssl, "CLIENT_TRAFFIC_SECRET_0",
hs->client_traffic_secret_0, hs->hash_len) &&
derive_secret(hs, hs->server_traffic_secret_0, hs->hash_len,
kTLS13LabelServerApplicationTraffic,
strlen(kTLS13LabelServerApplicationTraffic)) &&
ssl_log_secret(ssl, "SERVER_TRAFFIC_SECRET_0",
hs->server_traffic_secret_0, hs->hash_len) &&
derive_secret(hs, ssl->s3->exporter_secret, hs->hash_len,
kTLS13LabelExporter, strlen(kTLS13LabelExporter)) &&
ssl_log_secret(ssl, "EXPORTER_SECRET", ssl->s3->exporter_secret,
hs->hash_len);
}
static const char kTLS13LabelApplicationTraffic[] = "traffic upd";
int tls13_rotate_traffic_key(SSL *ssl, enum evp_aead_direction_t direction) {
uint8_t *secret;
size_t secret_len;
if (direction == evp_aead_open) {
secret = ssl->s3->read_traffic_secret;
secret_len = ssl->s3->read_traffic_secret_len;
} else {
secret = ssl->s3->write_traffic_secret;
secret_len = ssl->s3->write_traffic_secret_len;
}
const EVP_MD *digest = ssl_session_get_digest(SSL_get_session(ssl));
if (!hkdf_expand_label(
secret, digest, secret, secret_len, kTLS13LabelApplicationTraffic,
strlen(kTLS13LabelApplicationTraffic), NULL, 0, secret_len)) {
return 0;
}
return tls13_set_traffic_key(ssl, direction, secret, secret_len);
}
static const char kTLS13LabelResumption[] = "res master";
int tls13_derive_resumption_secret(SSL_HANDSHAKE *hs) {
if (hs->hash_len > SSL_MAX_MASTER_KEY_LENGTH) {
OPENSSL_PUT_ERROR(SSL, ERR_R_INTERNAL_ERROR);
return 0;
}
hs->new_session->master_key_length = hs->hash_len;
return derive_secret(hs, hs->new_session->master_key,
hs->new_session->master_key_length,
kTLS13LabelResumption, strlen(kTLS13LabelResumption));
}
static const char kTLS13LabelFinished[] = "finished";
// tls13_verify_data sets |out| to be the HMAC of |context| using a derived
// Finished key for both Finished messages and the PSK binder.
static int tls13_verify_data(const EVP_MD *digest, uint16_t version,
uint8_t *out, size_t *out_len,
const uint8_t *secret, size_t hash_len,
uint8_t *context, size_t context_len) {
uint8_t key[EVP_MAX_MD_SIZE];
unsigned len;
if (!hkdf_expand_label(key, digest, secret, hash_len, kTLS13LabelFinished,
strlen(kTLS13LabelFinished), NULL, 0, hash_len) ||
HMAC(digest, key, hash_len, context, context_len, out, &len) == NULL) {
return 0;
}
*out_len = len;
return 1;
}
int tls13_finished_mac(SSL_HANDSHAKE *hs, uint8_t *out, size_t *out_len,
int is_server) {
const uint8_t *traffic_secret;
if (is_server) {
traffic_secret = hs->server_handshake_secret;
} else {
traffic_secret = hs->client_handshake_secret;
}
uint8_t context_hash[EVP_MAX_MD_SIZE];
size_t context_hash_len;
if (!hs->transcript.GetHash(context_hash, &context_hash_len) ||
!tls13_verify_data(hs->transcript.Digest(), hs->ssl->version, out,
out_len, traffic_secret, hs->hash_len, context_hash,
context_hash_len)) {
return 0;
}
return 1;
}
static const char kTLS13LabelResumptionPSK[] = "resumption";
bool tls13_derive_session_psk(SSL_SESSION *session, Span<const uint8_t> nonce) {
const EVP_MD *digest = ssl_session_get_digest(session);
return hkdf_expand_label(session->master_key, digest, session->master_key,
session->master_key_length, kTLS13LabelResumptionPSK,
strlen(kTLS13LabelResumptionPSK), nonce.data(),
nonce.size(), session->master_key_length);
}
static const char kTLS13LabelExportKeying[] = "exporter";
int tls13_export_keying_material(SSL *ssl, Span<uint8_t> out,
Span<const uint8_t> secret,
Span<const char> label,
Span<const uint8_t> context) {
if (secret.empty()) {
assert(0);
OPENSSL_PUT_ERROR(SSL, ERR_R_INTERNAL_ERROR);
return 0;
}
const EVP_MD *digest = ssl_session_get_digest(SSL_get_session(ssl));
uint8_t hash[EVP_MAX_MD_SIZE];
uint8_t export_context[EVP_MAX_MD_SIZE];
uint8_t derived_secret[EVP_MAX_MD_SIZE];
unsigned hash_len;
unsigned export_context_len;
unsigned derived_secret_len = EVP_MD_size(digest);
return EVP_Digest(context.data(), context.size(), hash, &hash_len, digest,
nullptr) &&
EVP_Digest(nullptr, 0, export_context, &export_context_len, digest,
nullptr) &&
hkdf_expand_label(derived_secret, digest, secret.data(), secret.size(),
label.data(), label.size(), export_context,
export_context_len, derived_secret_len) &&
hkdf_expand_label(out.data(), digest, derived_secret,
derived_secret_len, kTLS13LabelExportKeying,
strlen(kTLS13LabelExportKeying), hash, hash_len,
out.size());
}
static const char kTLS13LabelPSKBinder[] = "res binder";
static int tls13_psk_binder(uint8_t *out, uint16_t version,
const EVP_MD *digest, uint8_t *psk, size_t psk_len,
uint8_t *context, size_t context_len,
size_t hash_len) {
uint8_t binder_context[EVP_MAX_MD_SIZE];
unsigned binder_context_len;
if (!EVP_Digest(NULL, 0, binder_context, &binder_context_len, digest, NULL)) {
return 0;
}
uint8_t early_secret[EVP_MAX_MD_SIZE] = {0};
size_t early_secret_len;
if (!HKDF_extract(early_secret, &early_secret_len, digest, psk, hash_len,
NULL, 0)) {
return 0;
}
uint8_t binder_key[EVP_MAX_MD_SIZE] = {0};
size_t len;
if (!hkdf_expand_label(binder_key, digest, early_secret, hash_len,
kTLS13LabelPSKBinder, strlen(kTLS13LabelPSKBinder),
binder_context, binder_context_len, hash_len) ||
!tls13_verify_data(digest, version, out, &len, binder_key, hash_len,
context, context_len)) {
return 0;
}
return 1;
}
int tls13_write_psk_binder(SSL_HANDSHAKE *hs, uint8_t *msg, size_t len) {
SSL *const ssl = hs->ssl;
const EVP_MD *digest = ssl_session_get_digest(ssl->session);
size_t hash_len = EVP_MD_size(digest);
if (len < hash_len + 3) {
OPENSSL_PUT_ERROR(SSL, ERR_R_INTERNAL_ERROR);
return 0;
}
ScopedEVP_MD_CTX ctx;
uint8_t context[EVP_MAX_MD_SIZE];
unsigned context_len;
if (!EVP_DigestInit_ex(ctx.get(), digest, NULL) ||
!EVP_DigestUpdate(ctx.get(), hs->transcript.buffer().data(),
hs->transcript.buffer().size()) ||
!EVP_DigestUpdate(ctx.get(), msg, len - hash_len - 3) ||
!EVP_DigestFinal_ex(ctx.get(), context, &context_len)) {
return 0;
}
uint8_t verify_data[EVP_MAX_MD_SIZE] = {0};
if (!tls13_psk_binder(verify_data, ssl->session->ssl_version, digest,
ssl->session->master_key,
ssl->session->master_key_length, context, context_len,
hash_len)) {
return 0;
}
OPENSSL_memcpy(msg + len - hash_len, verify_data, hash_len);
return 1;
}
int tls13_verify_psk_binder(SSL_HANDSHAKE *hs, SSL_SESSION *session,
const SSLMessage &msg, CBS *binders) {
size_t hash_len = hs->transcript.DigestLen();
// The message must be large enough to exclude the binders.
if (CBS_len(&msg.raw) < CBS_len(binders) + 2) {
OPENSSL_PUT_ERROR(SSL, ERR_R_INTERNAL_ERROR);
return 0;
}
// Hash a ClientHello prefix up to the binders. This includes the header. For
// now, this assumes we only ever verify PSK binders on initial
// ClientHellos.
uint8_t context[EVP_MAX_MD_SIZE];
unsigned context_len;
if (!EVP_Digest(CBS_data(&msg.raw), CBS_len(&msg.raw) - CBS_len(binders) - 2,
context, &context_len, hs->transcript.Digest(), NULL)) {
return 0;
}
uint8_t verify_data[EVP_MAX_MD_SIZE] = {0};
CBS binder;
if (!tls13_psk_binder(verify_data, hs->ssl->version, hs->transcript.Digest(),
session->master_key, session->master_key_length,
context, context_len, hash_len) ||
// We only consider the first PSK, so compare against the first binder.
!CBS_get_u8_length_prefixed(binders, &binder)) {
OPENSSL_PUT_ERROR(SSL, ERR_R_INTERNAL_ERROR);
return 0;
}
int binder_ok =
CBS_len(&binder) == hash_len &&
CRYPTO_memcmp(CBS_data(&binder), verify_data, hash_len) == 0;
#if defined(BORINGSSL_UNSAFE_FUZZER_MODE)
binder_ok = 1;
#endif
if (!binder_ok) {
OPENSSL_PUT_ERROR(SSL, SSL_R_DIGEST_CHECK_FAILED);
return 0;
}
return 1;
}
} // namespace bssl