diff options
Diffstat (limited to 'lib/handshake.c')
| -rw-r--r-- | lib/handshake.c | 99 |
1 files changed, 48 insertions, 51 deletions
diff --git a/lib/handshake.c b/lib/handshake.c index 9a38cf8242..af6e0a25b6 100644 --- a/lib/handshake.c +++ b/lib/handshake.c @@ -166,48 +166,14 @@ static int resume_copy_required_values(gnutls_session_t session) return 0; } - -/* this function will produce GNUTLS_RANDOM_SIZE==32 bytes of random data - * and put it to dst. - */ -static int create_tls_random(uint8_t * dst) -{ - int ret; - - /* Use nonce rng level for the most of the - * buffer except for the first 4 that are the - * system's time. - */ - -#if defined(FUZZING_BUILD_MODE_UNSAFE_FOR_PRODUCTION) - /* When fuzzying avoid timing dependencies */ - memset(dst, 1, 4); -#else - uint32_t tim; - - tim = gnutls_time(NULL); - /* generate server random value */ - _gnutls_write_uint32(tim, dst); -#endif - - ret = - gnutls_rnd(GNUTLS_RND_NONCE, &dst[3], GNUTLS_RANDOM_SIZE - 3); - if (ret < 0) { - gnutls_assert(); - return ret; - } - - return 0; -} - int _gnutls_set_client_random(gnutls_session_t session, uint8_t * rnd) { int ret; - if (rnd != NULL) + if (rnd != NULL) { /* server */ memcpy(session->security_parameters.client_random, rnd, GNUTLS_RANDOM_SIZE); - else { + } else { /* client */ /* no random given, we generate. */ if (session->internals.sc_random_set != 0) { memcpy(session->security_parameters.client_random, @@ -216,9 +182,9 @@ int _gnutls_set_client_random(gnutls_session_t session, uint8_t * rnd) GNUTLS_RANDOM_SIZE); } else { ret = - create_tls_random(session-> - security_parameters. - client_random); + gnutls_rnd(GNUTLS_RND_NONCE, + session->security_parameters.client_random, + GNUTLS_RANDOM_SIZE); if (ret < 0) return gnutls_assert_val(ret); } @@ -226,27 +192,58 @@ int _gnutls_set_client_random(gnutls_session_t session, uint8_t * rnd) return 0; } -int _gnutls_set_server_random(gnutls_session_t session, uint8_t * rnd) +int _gnutls_set_server_random(gnutls_session_t session, int version, uint8_t * rnd) { int ret; - if (rnd != NULL) + if (rnd != NULL) { /* client */ memcpy(session->security_parameters.server_random, rnd, GNUTLS_RANDOM_SIZE); - else { - /* no random given, we generate. */ + + /* check whether the server random value is set according to + * to TLS 1.3. p4.1.3 requirements */ + if (version <= GNUTLS_TLS1_2 && _gnutls_version_is_supported(session, GNUTLS_TLS1_3)) { + if (version == GNUTLS_TLS1_2 && + memcmp(&session->security_parameters.server_random[GNUTLS_RANDOM_SIZE-8-1], + "\x44\x4F\x57\x4E\x47\x52\x44\x01", 8) == 0) { + _gnutls_audit_log(session, + "Detected downgrade to TLS 1.2 from TLS 1.3\n"); + return gnutls_assert_val(GNUTLS_E_RECEIVED_ILLEGAL_PARAMETER); + } else if (version <= GNUTLS_TLS1_1 && + memcmp(&session->security_parameters.server_random[GNUTLS_RANDOM_SIZE-8-1], + "\x44\x4F\x57\x4E\x47\x52\x44\x00", 8) == 0) { + _gnutls_audit_log(session, + "Detected downgrade to TLS 1.1 or earlier from TLS 1.3\n"); + return gnutls_assert_val(GNUTLS_E_RECEIVED_ILLEGAL_PARAMETER); + } + } + + } else { /* server */ if (session->internals.sc_random_set != 0) { memcpy(session->security_parameters.server_random, session->internals. resumed_security_parameters.server_random, GNUTLS_RANDOM_SIZE); } else { - ret = - create_tls_random(session-> - security_parameters. - server_random); - if (ret < 0) - return gnutls_assert_val(ret); + if (version == GNUTLS_TLS1_2) { + memcpy(&session->security_parameters.server_random[GNUTLS_RANDOM_SIZE-8-1], + "\x44\x4F\x57\x4E\x47\x52\x44\x01", 8); + ret = + gnutls_rnd(GNUTLS_RND_NONCE, session->security_parameters.server_random, GNUTLS_RANDOM_SIZE-8); + } else if (version <= GNUTLS_TLS1_1) { + memcpy(&session->security_parameters.server_random[GNUTLS_RANDOM_SIZE-8-1], + "\x44\x4F\x57\x4E\x47\x52\x44\x00", 8); + ret = + gnutls_rnd(GNUTLS_RND_NONCE, session->security_parameters.server_random, GNUTLS_RANDOM_SIZE-8); + } else { + ret = + gnutls_rnd(GNUTLS_RND_NONCE, session->security_parameters.server_random, GNUTLS_RANDOM_SIZE); + } + + if (ret < 0) { + gnutls_assert(); + return ret; + } } } return 0; @@ -480,7 +477,7 @@ read_client_hello(gnutls_session_t session, uint8_t * data, pos += GNUTLS_RANDOM_SIZE; - ret = _gnutls_set_server_random(session, NULL); + ret = _gnutls_set_server_random(session, neg_version, NULL); if (ret < 0) return gnutls_assert_val(ret); @@ -1510,7 +1507,7 @@ read_server_hello(gnutls_session_t session, pos += 2; DECR_LEN(len, GNUTLS_RANDOM_SIZE); - ret = _gnutls_set_server_random(session, &data[pos]); + ret = _gnutls_set_server_random(session, version, &data[pos]); if (ret < 0) return gnutls_assert_val(ret); |