/* * TLS 1.3 server-side functions * * Copyright The Mbed TLS Contributors * SPDX-License-Identifier: Apache-2.0 * * 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 * * http://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. */ #include "common.h" #if defined(MBEDTLS_SSL_SRV_C) && defined(MBEDTLS_SSL_PROTO_TLS1_3) #include "mbedtls/debug.h" #include "mbedtls/error.h" #include "mbedtls/platform.h" #include "mbedtls/constant_time.h" #include "ssl_misc.h" #include "ssl_tls13_keys.h" #include "ssl_debug_helpers.h" static const mbedtls_ssl_ciphersuite_t *ssl_tls13_validate_peer_ciphersuite( mbedtls_ssl_context *ssl, unsigned int cipher_suite) { const mbedtls_ssl_ciphersuite_t *ciphersuite_info; if (!mbedtls_ssl_tls13_cipher_suite_is_offered(ssl, cipher_suite)) { return NULL; } ciphersuite_info = mbedtls_ssl_ciphersuite_from_id(cipher_suite); if ((mbedtls_ssl_validate_ciphersuite(ssl, ciphersuite_info, ssl->tls_version, ssl->tls_version) != 0)) { return NULL; } return ciphersuite_info; } #if defined(MBEDTLS_SSL_TLS1_3_KEY_EXCHANGE_MODE_SOME_PSK_ENABLED) /* From RFC 8446: * * enum { psk_ke(0), psk_dhe_ke(1), (255) } PskKeyExchangeMode; * struct { * PskKeyExchangeMode ke_modes<1..255>; * } PskKeyExchangeModes; */ MBEDTLS_CHECK_RETURN_CRITICAL static int ssl_tls13_parse_key_exchange_modes_ext(mbedtls_ssl_context *ssl, const unsigned char *buf, const unsigned char *end) { const unsigned char *p = buf; size_t ke_modes_len; int ke_modes = 0; /* Read ke_modes length (1 Byte) */ MBEDTLS_SSL_CHK_BUF_READ_PTR(p, end, 1); ke_modes_len = *p++; /* Currently, there are only two PSK modes, so even without looking * at the content, something's wrong if the list has more than 2 items. */ if (ke_modes_len > 2) { MBEDTLS_SSL_PEND_FATAL_ALERT(MBEDTLS_SSL_ALERT_MSG_ILLEGAL_PARAMETER, MBEDTLS_ERR_SSL_ILLEGAL_PARAMETER); return MBEDTLS_ERR_SSL_HANDSHAKE_FAILURE; } MBEDTLS_SSL_CHK_BUF_READ_PTR(p, end, ke_modes_len); while (ke_modes_len-- != 0) { switch (*p++) { case MBEDTLS_SSL_TLS1_3_PSK_MODE_PURE: ke_modes |= MBEDTLS_SSL_TLS1_3_KEY_EXCHANGE_MODE_PSK; MBEDTLS_SSL_DEBUG_MSG(3, ("Found PSK KEX MODE")); break; case MBEDTLS_SSL_TLS1_3_PSK_MODE_ECDHE: ke_modes |= MBEDTLS_SSL_TLS1_3_KEY_EXCHANGE_MODE_PSK_EPHEMERAL; MBEDTLS_SSL_DEBUG_MSG(3, ("Found PSK_EPHEMERAL KEX MODE")); break; default: MBEDTLS_SSL_PEND_FATAL_ALERT(MBEDTLS_SSL_ALERT_MSG_ILLEGAL_PARAMETER, MBEDTLS_ERR_SSL_ILLEGAL_PARAMETER); return MBEDTLS_ERR_SSL_ILLEGAL_PARAMETER; } } ssl->handshake->tls13_kex_modes = ke_modes; return 0; } #define SSL_TLS1_3_OFFERED_PSK_NOT_MATCH 1 #define SSL_TLS1_3_OFFERED_PSK_MATCH 0 #if defined(MBEDTLS_SSL_SESSION_TICKETS) MBEDTLS_CHECK_RETURN_CRITICAL static int ssl_tls13_offered_psks_check_identity_match_ticket( mbedtls_ssl_context *ssl, const unsigned char *identity, size_t identity_len, uint32_t obfuscated_ticket_age, mbedtls_ssl_session *session) { int ret = MBEDTLS_ERR_ERROR_CORRUPTION_DETECTED; unsigned char *ticket_buffer; #if defined(MBEDTLS_HAVE_TIME) mbedtls_time_t now; uint64_t age_in_s; int64_t age_diff_in_ms; #endif ((void) obfuscated_ticket_age); MBEDTLS_SSL_DEBUG_MSG(2, ("=> check_identity_match_ticket")); /* Ticket parser is not configured, Skip */ if (ssl->conf->f_ticket_parse == NULL || identity_len == 0) { return 0; } /* We create a copy of the encrypted ticket since the ticket parsing * function is allowed to use its input buffer as an output buffer * (in-place decryption). We do, however, need the original buffer for * computing the PSK binder value. */ ticket_buffer = mbedtls_calloc(1, identity_len); if (ticket_buffer == NULL) { MBEDTLS_SSL_DEBUG_MSG(1, ("buffer too small")); return MBEDTLS_ERR_SSL_ALLOC_FAILED; } memcpy(ticket_buffer, identity, identity_len); if ((ret = ssl->conf->f_ticket_parse(ssl->conf->p_ticket, session, ticket_buffer, identity_len)) != 0) { if (ret == MBEDTLS_ERR_SSL_INVALID_MAC) { MBEDTLS_SSL_DEBUG_MSG(3, ("ticket is not authentic")); } else if (ret == MBEDTLS_ERR_SSL_SESSION_TICKET_EXPIRED) { MBEDTLS_SSL_DEBUG_MSG(3, ("ticket is expired")); } else { MBEDTLS_SSL_DEBUG_RET(1, "ticket_parse", ret); } } /* We delete the temporary buffer */ mbedtls_free(ticket_buffer); if (ret != 0) { goto exit; } /* RFC 8446 section 4.2.9 * * Servers SHOULD NOT send NewSessionTicket with tickets that are not * compatible with the advertised modes; however, if a server does so, * the impact will just be that the client's attempts at resumption fail. * * We regard the ticket with incompatible key exchange modes as not match. */ ret = MBEDTLS_ERR_ERROR_GENERIC_ERROR; MBEDTLS_SSL_PRINT_TICKET_FLAGS(4, session->ticket_flags); if (mbedtls_ssl_tls13_check_kex_modes( ssl, mbedtls_ssl_session_get_ticket_flags( session, MBEDTLS_SSL_TLS1_3_KEY_EXCHANGE_MODE_PSK_ALL))) { MBEDTLS_SSL_DEBUG_MSG(3, ("No suitable key exchange mode")); goto exit; } ret = MBEDTLS_ERR_SSL_SESSION_TICKET_EXPIRED; #if defined(MBEDTLS_HAVE_TIME) now = mbedtls_time(NULL); if (now < session->start) { MBEDTLS_SSL_DEBUG_MSG( 3, ("Invalid ticket start time ( now=%" MBEDTLS_PRINTF_LONGLONG ", start=%" MBEDTLS_PRINTF_LONGLONG " )", (long long) now, (long long) session->start)); goto exit; } age_in_s = (uint64_t) (now - session->start); /* RFC 8446 section 4.6.1 * * Servers MUST NOT use any value greater than 604800 seconds (7 days). * * RFC 8446 section 4.2.11.1 * * Clients MUST NOT attempt to use tickets which have ages greater than * the "ticket_lifetime" value which was provided with the ticket. * * For time being, the age MUST be less than 604800 seconds (7 days). */ if (age_in_s > 604800) { MBEDTLS_SSL_DEBUG_MSG( 3, ("Ticket age exceeds limitation ticket_age=%lu", (long unsigned int) age_in_s)); goto exit; } /* RFC 8446 section 4.2.10 * * For PSKs provisioned via NewSessionTicket, a server MUST validate that * the ticket age for the selected PSK identity (computed by subtracting * ticket_age_add from PskIdentity.obfuscated_ticket_age modulo 2^32) is * within a small tolerance of the time since the ticket was issued. * * NOTE: When `now == session->start`, `age_diff_in_ms` may be negative * as the age units are different on the server (s) and in the * client (ms) side. Add a -1000 ms tolerance window to take this * into account. */ age_diff_in_ms = age_in_s * 1000; age_diff_in_ms -= (obfuscated_ticket_age - session->ticket_age_add); if (age_diff_in_ms <= -1000 || age_diff_in_ms > MBEDTLS_SSL_TLS1_3_TICKET_AGE_TOLERANCE) { MBEDTLS_SSL_DEBUG_MSG( 3, ("Ticket age outside tolerance window ( diff=%d )", (int) age_diff_in_ms)); goto exit; } ret = 0; #endif /* MBEDTLS_HAVE_TIME */ exit: if (ret != 0) { mbedtls_ssl_session_free(session); } MBEDTLS_SSL_DEBUG_MSG(2, ("<= check_identity_match_ticket")); return ret; } #endif /* MBEDTLS_SSL_SESSION_TICKETS */ MBEDTLS_CHECK_RETURN_CRITICAL static int ssl_tls13_offered_psks_check_identity_match( mbedtls_ssl_context *ssl, const unsigned char *identity, size_t identity_len, uint32_t obfuscated_ticket_age, int *psk_type, mbedtls_ssl_session *session) { ((void) session); ((void) obfuscated_ticket_age); *psk_type = MBEDTLS_SSL_TLS1_3_PSK_EXTERNAL; MBEDTLS_SSL_DEBUG_BUF(4, "identity", identity, identity_len); ssl->handshake->resume = 0; #if defined(MBEDTLS_SSL_SESSION_TICKETS) if (ssl_tls13_offered_psks_check_identity_match_ticket( ssl, identity, identity_len, obfuscated_ticket_age, session) == SSL_TLS1_3_OFFERED_PSK_MATCH) { ssl->handshake->resume = 1; *psk_type = MBEDTLS_SSL_TLS1_3_PSK_RESUMPTION; mbedtls_ssl_set_hs_psk(ssl, session->resumption_key, session->resumption_key_len); MBEDTLS_SSL_DEBUG_BUF(4, "Ticket-resumed PSK:", session->resumption_key, session->resumption_key_len); MBEDTLS_SSL_DEBUG_MSG(4, ("ticket: obfuscated_ticket_age: %u", (unsigned) obfuscated_ticket_age)); return SSL_TLS1_3_OFFERED_PSK_MATCH; } #endif /* MBEDTLS_SSL_SESSION_TICKETS */ /* Check identity with external configured function */ if (ssl->conf->f_psk != NULL) { if (ssl->conf->f_psk( ssl->conf->p_psk, ssl, identity, identity_len) == 0) { return SSL_TLS1_3_OFFERED_PSK_MATCH; } return SSL_TLS1_3_OFFERED_PSK_NOT_MATCH; } MBEDTLS_SSL_DEBUG_BUF(5, "identity", identity, identity_len); /* Check identity with pre-configured psk */ if (ssl->conf->psk_identity != NULL && identity_len == ssl->conf->psk_identity_len && mbedtls_ct_memcmp(ssl->conf->psk_identity, identity, identity_len) == 0) { mbedtls_ssl_set_hs_psk(ssl, ssl->conf->psk, ssl->conf->psk_len); return SSL_TLS1_3_OFFERED_PSK_MATCH; } return SSL_TLS1_3_OFFERED_PSK_NOT_MATCH; } MBEDTLS_CHECK_RETURN_CRITICAL static int ssl_tls13_offered_psks_check_binder_match(mbedtls_ssl_context *ssl, const unsigned char *binder, size_t binder_len, int psk_type, psa_algorithm_t psk_hash_alg) { int ret = MBEDTLS_ERR_ERROR_CORRUPTION_DETECTED; unsigned char transcript[PSA_HASH_MAX_SIZE]; size_t transcript_len; unsigned char *psk; size_t psk_len; unsigned char server_computed_binder[PSA_HASH_MAX_SIZE]; /* Get current state of handshake transcript. */ ret = mbedtls_ssl_get_handshake_transcript( ssl, mbedtls_hash_info_md_from_psa(psk_hash_alg), transcript, sizeof(transcript), &transcript_len); if (ret != 0) { return ret; } ret = mbedtls_ssl_tls13_export_handshake_psk(ssl, &psk, &psk_len); if (ret != 0) { return ret; } ret = mbedtls_ssl_tls13_create_psk_binder(ssl, psk_hash_alg, psk, psk_len, psk_type, transcript, server_computed_binder); #if defined(MBEDTLS_USE_PSA_CRYPTO) mbedtls_free((void *) psk); #endif if (ret != 0) { MBEDTLS_SSL_DEBUG_MSG(1, ("PSK binder calculation failed.")); return MBEDTLS_ERR_SSL_HANDSHAKE_FAILURE; } MBEDTLS_SSL_DEBUG_BUF(3, "psk binder ( computed ): ", server_computed_binder, transcript_len); MBEDTLS_SSL_DEBUG_BUF(3, "psk binder ( received ): ", binder, binder_len); if (mbedtls_ct_memcmp(server_computed_binder, binder, binder_len) == 0) { return SSL_TLS1_3_OFFERED_PSK_MATCH; } mbedtls_platform_zeroize(server_computed_binder, sizeof(server_computed_binder)); return SSL_TLS1_3_OFFERED_PSK_NOT_MATCH; } MBEDTLS_CHECK_RETURN_CRITICAL static int ssl_tls13_select_ciphersuite_for_psk( mbedtls_ssl_context *ssl, const unsigned char *cipher_suites, const unsigned char *cipher_suites_end, uint16_t *selected_ciphersuite, const mbedtls_ssl_ciphersuite_t **selected_ciphersuite_info) { psa_algorithm_t psk_hash_alg = PSA_ALG_SHA_256; *selected_ciphersuite = 0; *selected_ciphersuite_info = NULL; /* RFC 8446, page 55. * * For externally established PSKs, the Hash algorithm MUST be set when the * PSK is established or default to SHA-256 if no such algorithm is defined. * */ /* * Search for a matching ciphersuite */ for (const unsigned char *p = cipher_suites; p < cipher_suites_end; p += 2) { uint16_t cipher_suite; const mbedtls_ssl_ciphersuite_t *ciphersuite_info; cipher_suite = MBEDTLS_GET_UINT16_BE(p, 0); ciphersuite_info = ssl_tls13_validate_peer_ciphersuite(ssl, cipher_suite); if (ciphersuite_info == NULL) { continue; } /* MAC of selected ciphersuite MUST be same with PSK binder if exist. * Otherwise, client should reject. */ if (psk_hash_alg == mbedtls_psa_translate_md(ciphersuite_info->mac)) { *selected_ciphersuite = cipher_suite; *selected_ciphersuite_info = ciphersuite_info; return 0; } } MBEDTLS_SSL_DEBUG_MSG(2, ("No matched ciphersuite")); return MBEDTLS_ERR_SSL_HANDSHAKE_FAILURE; } #if defined(MBEDTLS_SSL_SESSION_TICKETS) MBEDTLS_CHECK_RETURN_CRITICAL static int ssl_tls13_select_ciphersuite_for_resumption( mbedtls_ssl_context *ssl, const unsigned char *cipher_suites, const unsigned char *cipher_suites_end, mbedtls_ssl_session *session, uint16_t *selected_ciphersuite, const mbedtls_ssl_ciphersuite_t **selected_ciphersuite_info) { *selected_ciphersuite = 0; *selected_ciphersuite_info = NULL; for (const unsigned char *p = cipher_suites; p < cipher_suites_end; p += 2) { uint16_t cipher_suite = MBEDTLS_GET_UINT16_BE(p, 0); const mbedtls_ssl_ciphersuite_t *ciphersuite_info; if (cipher_suite != session->ciphersuite) { continue; } ciphersuite_info = ssl_tls13_validate_peer_ciphersuite(ssl, cipher_suite); if (ciphersuite_info == NULL) { continue; } *selected_ciphersuite = cipher_suite; *selected_ciphersuite_info = ciphersuite_info; return 0; } return MBEDTLS_ERR_SSL_HANDSHAKE_FAILURE; } MBEDTLS_CHECK_RETURN_CRITICAL static int ssl_tls13_session_copy_ticket(mbedtls_ssl_session *dst, const mbedtls_ssl_session *src) { dst->ticket_age_add = src->ticket_age_add; dst->ticket_flags = src->ticket_flags; dst->resumption_key_len = src->resumption_key_len; if (src->resumption_key_len == 0) { return MBEDTLS_ERR_SSL_INTERNAL_ERROR; } memcpy(dst->resumption_key, src->resumption_key, src->resumption_key_len); return 0; } #endif /* MBEDTLS_SSL_SESSION_TICKETS */ /* Parser for pre_shared_key extension in client hello * struct { * opaque identity<1..2^16-1>; * uint32 obfuscated_ticket_age; * } PskIdentity; * * opaque PskBinderEntry<32..255>; * * struct { * PskIdentity identities<7..2^16-1>; * PskBinderEntry binders<33..2^16-1>; * } OfferedPsks; * * struct { * select (Handshake.msg_type) { * case client_hello: OfferedPsks; * .... * }; * } PreSharedKeyExtension; */ MBEDTLS_CHECK_RETURN_CRITICAL static int ssl_tls13_parse_pre_shared_key_ext(mbedtls_ssl_context *ssl, const unsigned char *pre_shared_key_ext, const unsigned char *pre_shared_key_ext_end, const unsigned char *ciphersuites, const unsigned char *ciphersuites_end) { const unsigned char *identities = pre_shared_key_ext; const unsigned char *p_identity_len; size_t identities_len; const unsigned char *identities_end; const unsigned char *binders; const unsigned char *p_binder_len; size_t binders_len; const unsigned char *binders_end; int matched_identity = -1; int identity_id = -1; MBEDTLS_SSL_DEBUG_BUF(3, "pre_shared_key extension", pre_shared_key_ext, pre_shared_key_ext_end - pre_shared_key_ext); /* identities_len 2 bytes * identities_data >= 7 bytes */ MBEDTLS_SSL_CHK_BUF_READ_PTR(identities, pre_shared_key_ext_end, 7 + 2); identities_len = MBEDTLS_GET_UINT16_BE(identities, 0); p_identity_len = identities + 2; MBEDTLS_SSL_CHK_BUF_READ_PTR(p_identity_len, pre_shared_key_ext_end, identities_len); identities_end = p_identity_len + identities_len; /* binders_len 2 bytes * binders >= 33 bytes */ binders = identities_end; MBEDTLS_SSL_CHK_BUF_READ_PTR(binders, pre_shared_key_ext_end, 33 + 2); binders_len = MBEDTLS_GET_UINT16_BE(binders, 0); p_binder_len = binders + 2; MBEDTLS_SSL_CHK_BUF_READ_PTR(p_binder_len, pre_shared_key_ext_end, binders_len); binders_end = p_binder_len + binders_len; ssl->handshake->update_checksum(ssl, pre_shared_key_ext, identities_end - pre_shared_key_ext); while (p_identity_len < identities_end && p_binder_len < binders_end) { const unsigned char *identity; size_t identity_len; uint32_t obfuscated_ticket_age; const unsigned char *binder; size_t binder_len; int ret = MBEDTLS_ERR_ERROR_CORRUPTION_DETECTED; int psk_type; uint16_t cipher_suite; const mbedtls_ssl_ciphersuite_t *ciphersuite_info; #if defined(MBEDTLS_SSL_SESSION_TICKETS) mbedtls_ssl_session session; mbedtls_ssl_session_init(&session); #endif MBEDTLS_SSL_CHK_BUF_READ_PTR(p_identity_len, identities_end, 2 + 1 + 4); identity_len = MBEDTLS_GET_UINT16_BE(p_identity_len, 0); identity = p_identity_len + 2; MBEDTLS_SSL_CHK_BUF_READ_PTR(identity, identities_end, identity_len + 4); obfuscated_ticket_age = MBEDTLS_GET_UINT32_BE(identity, identity_len); p_identity_len += identity_len + 6; MBEDTLS_SSL_CHK_BUF_READ_PTR(p_binder_len, binders_end, 1 + 32); binder_len = *p_binder_len; binder = p_binder_len + 1; MBEDTLS_SSL_CHK_BUF_READ_PTR(binder, binders_end, binder_len); p_binder_len += binder_len + 1; identity_id++; if (matched_identity != -1) { continue; } ret = ssl_tls13_offered_psks_check_identity_match( ssl, identity, identity_len, obfuscated_ticket_age, &psk_type, &session); if (ret != SSL_TLS1_3_OFFERED_PSK_MATCH) { continue; } MBEDTLS_SSL_DEBUG_MSG(4, ("found matched identity")); switch (psk_type) { case MBEDTLS_SSL_TLS1_3_PSK_EXTERNAL: ret = ssl_tls13_select_ciphersuite_for_psk( ssl, ciphersuites, ciphersuites_end, &cipher_suite, &ciphersuite_info); break; case MBEDTLS_SSL_TLS1_3_PSK_RESUMPTION: #if defined(MBEDTLS_SSL_SESSION_TICKETS) ret = ssl_tls13_select_ciphersuite_for_resumption( ssl, ciphersuites, ciphersuites_end, &session, &cipher_suite, &ciphersuite_info); if (ret != 0) { mbedtls_ssl_session_free(&session); } #else ret = MBEDTLS_ERR_SSL_FEATURE_UNAVAILABLE; #endif break; default: return MBEDTLS_ERR_SSL_INTERNAL_ERROR; } if (ret != 0) { /* See below, no cipher_suite available, abort handshake */ MBEDTLS_SSL_PEND_FATAL_ALERT( MBEDTLS_SSL_ALERT_MSG_DECRYPT_ERROR, MBEDTLS_ERR_SSL_HANDSHAKE_FAILURE); MBEDTLS_SSL_DEBUG_RET( 2, "ssl_tls13_select_ciphersuite", ret); return ret; } ret = ssl_tls13_offered_psks_check_binder_match( ssl, binder, binder_len, psk_type, mbedtls_psa_translate_md(ciphersuite_info->mac)); if (ret != SSL_TLS1_3_OFFERED_PSK_MATCH) { /* For security reasons, the handshake should be aborted when we * fail to validate a binder value. See RFC 8446 section 4.2.11.2 * and appendix E.6. */ #if defined(MBEDTLS_SSL_SESSION_TICKETS) mbedtls_ssl_session_free(&session); #endif MBEDTLS_SSL_DEBUG_MSG(3, ("Invalid binder.")); MBEDTLS_SSL_DEBUG_RET(1, "ssl_tls13_offered_psks_check_binder_match", ret); MBEDTLS_SSL_PEND_FATAL_ALERT( MBEDTLS_SSL_ALERT_MSG_DECRYPT_ERROR, MBEDTLS_ERR_SSL_HANDSHAKE_FAILURE); return ret; } matched_identity = identity_id; /* Update handshake parameters */ ssl->handshake->ciphersuite_info = ciphersuite_info; ssl->session_negotiate->ciphersuite = cipher_suite; MBEDTLS_SSL_DEBUG_MSG(2, ("overwrite ciphersuite: %04x - %s", cipher_suite, ciphersuite_info->name)); #if defined(MBEDTLS_SSL_SESSION_TICKETS) if (psk_type == MBEDTLS_SSL_TLS1_3_PSK_RESUMPTION) { ret = ssl_tls13_session_copy_ticket(ssl->session_negotiate, &session); mbedtls_ssl_session_free(&session); if (ret != 0) { return ret; } } #endif /* MBEDTLS_SSL_SESSION_TICKETS */ } if (p_identity_len != identities_end || p_binder_len != binders_end) { MBEDTLS_SSL_DEBUG_MSG(3, ("pre_shared_key extension decode error")); MBEDTLS_SSL_PEND_FATAL_ALERT(MBEDTLS_SSL_ALERT_MSG_DECODE_ERROR, MBEDTLS_ERR_SSL_DECODE_ERROR); return MBEDTLS_ERR_SSL_DECODE_ERROR; } /* Update the handshake transcript with the binder list. */ ssl->handshake->update_checksum(ssl, identities_end, (size_t) (binders_end - identities_end)); if (matched_identity == -1) { MBEDTLS_SSL_DEBUG_MSG(3, ("No matched PSK or ticket.")); return MBEDTLS_ERR_SSL_UNKNOWN_IDENTITY; } ssl->handshake->selected_identity = (uint16_t) matched_identity; MBEDTLS_SSL_DEBUG_MSG(3, ("Pre shared key found")); return 0; } /* * struct { * select ( Handshake.msg_type ) { * .... * case server_hello: * uint16 selected_identity; * } * } PreSharedKeyExtension; */ static int ssl_tls13_write_server_pre_shared_key_ext(mbedtls_ssl_context *ssl, unsigned char *buf, unsigned char *end, size_t *olen) { unsigned char *p = (unsigned char *) buf; *olen = 0; int not_using_psk = 0; #if defined(MBEDTLS_USE_PSA_CRYPTO) not_using_psk = (mbedtls_svc_key_id_is_null(ssl->handshake->psk_opaque)); #else not_using_psk = (ssl->handshake->psk == NULL); #endif if (not_using_psk) { /* We shouldn't have called this extension writer unless we've * chosen to use a PSK. */ return MBEDTLS_ERR_SSL_INTERNAL_ERROR; } MBEDTLS_SSL_DEBUG_MSG(3, ("server hello, adding pre_shared_key extension")); MBEDTLS_SSL_CHK_BUF_PTR(p, end, 6); MBEDTLS_PUT_UINT16_BE(MBEDTLS_TLS_EXT_PRE_SHARED_KEY, p, 0); MBEDTLS_PUT_UINT16_BE(2, p, 2); MBEDTLS_PUT_UINT16_BE(ssl->handshake->selected_identity, p, 4); *olen = 6; MBEDTLS_SSL_DEBUG_MSG(4, ("sent selected_identity: %u", ssl->handshake->selected_identity)); mbedtls_ssl_tls13_set_hs_sent_ext_mask(ssl, MBEDTLS_TLS_EXT_PRE_SHARED_KEY); return 0; } #endif /* MBEDTLS_SSL_TLS1_3_KEY_EXCHANGE_MODE_SOME_PSK_ENABLED */ /* From RFC 8446: * struct { * ProtocolVersion versions<2..254>; * } SupportedVersions; */ MBEDTLS_CHECK_RETURN_CRITICAL static int ssl_tls13_parse_supported_versions_ext(mbedtls_ssl_context *ssl, const unsigned char *buf, const unsigned char *end) { const unsigned char *p = buf; size_t versions_len; const unsigned char *versions_end; uint16_t tls_version; int tls13_supported = 0; MBEDTLS_SSL_CHK_BUF_READ_PTR(p, end, 1); versions_len = p[0]; p += 1; MBEDTLS_SSL_CHK_BUF_READ_PTR(p, end, versions_len); versions_end = p + versions_len; while (p < versions_end) { MBEDTLS_SSL_CHK_BUF_READ_PTR(p, versions_end, 2); tls_version = mbedtls_ssl_read_version(p, ssl->conf->transport); p += 2; /* In this implementation we only support TLS 1.3 and DTLS 1.3. */ if (tls_version == MBEDTLS_SSL_VERSION_TLS1_3) { tls13_supported = 1; break; } } if (!tls13_supported) { MBEDTLS_SSL_DEBUG_MSG(1, ("TLS 1.3 is not supported by the client")); MBEDTLS_SSL_PEND_FATAL_ALERT(MBEDTLS_SSL_ALERT_MSG_PROTOCOL_VERSION, MBEDTLS_ERR_SSL_BAD_PROTOCOL_VERSION); return MBEDTLS_ERR_SSL_BAD_PROTOCOL_VERSION; } MBEDTLS_SSL_DEBUG_MSG(1, ("Negotiated version. Supported is [%04x]", (unsigned int) tls_version)); return 0; } #if defined(MBEDTLS_ECDH_C) /* * * From RFC 8446: * enum { * ... (0xFFFF) * } NamedGroup; * struct { * NamedGroup named_group_list<2..2^16-1>; * } NamedGroupList; */ MBEDTLS_CHECK_RETURN_CRITICAL static int ssl_tls13_parse_supported_groups_ext(mbedtls_ssl_context *ssl, const unsigned char *buf, const unsigned char *end) { const unsigned char *p = buf; size_t named_group_list_len; const unsigned char *named_group_list_end; MBEDTLS_SSL_DEBUG_BUF(3, "supported_groups extension", p, end - buf); MBEDTLS_SSL_CHK_BUF_READ_PTR(p, end, 2); named_group_list_len = MBEDTLS_GET_UINT16_BE(p, 0); p += 2; MBEDTLS_SSL_CHK_BUF_READ_PTR(p, end, named_group_list_len); named_group_list_end = p + named_group_list_len; ssl->handshake->hrr_selected_group = 0; while (p < named_group_list_end) { uint16_t named_group; MBEDTLS_SSL_CHK_BUF_READ_PTR(p, named_group_list_end, 2); named_group = MBEDTLS_GET_UINT16_BE(p, 0); p += 2; MBEDTLS_SSL_DEBUG_MSG(2, ("got named group: %s(%04x)", mbedtls_ssl_named_group_to_str(named_group), named_group)); if (!mbedtls_ssl_named_group_is_offered(ssl, named_group) || !mbedtls_ssl_named_group_is_supported(named_group) || ssl->handshake->hrr_selected_group != 0) { continue; } MBEDTLS_SSL_DEBUG_MSG(2, ("add named group %s(%04x) into received list.", mbedtls_ssl_named_group_to_str(named_group), named_group)); ssl->handshake->hrr_selected_group = named_group; } return 0; } #endif /* MBEDTLS_ECDH_C */ #define SSL_TLS1_3_PARSE_KEY_SHARES_EXT_NO_MATCH 1 #if defined(MBEDTLS_ECDH_C) /* * ssl_tls13_parse_key_shares_ext() verifies whether the information in the * extension is correct and stores the first acceptable key share and its associated group. * * Possible return values are: * - 0: Successful processing of the client provided key share extension. * - SSL_TLS1_3_PARSE_KEY_SHARES_EXT_NO_MATCH: The key shares provided by the client * does not match a group supported by the server. A HelloRetryRequest will * be needed. * - A negative value for fatal errors. */ MBEDTLS_CHECK_RETURN_CRITICAL static int ssl_tls13_parse_key_shares_ext(mbedtls_ssl_context *ssl, const unsigned char *buf, const unsigned char *end) { int ret = MBEDTLS_ERR_ERROR_CORRUPTION_DETECTED; unsigned char const *p = buf; unsigned char const *client_shares_end; size_t client_shares_len; /* From RFC 8446: * * struct { * KeyShareEntry client_shares<0..2^16-1>; * } KeyShareClientHello; * */ MBEDTLS_SSL_CHK_BUF_READ_PTR(p, end, 2); client_shares_len = MBEDTLS_GET_UINT16_BE(p, 0); p += 2; MBEDTLS_SSL_CHK_BUF_READ_PTR(p, end, client_shares_len); ssl->handshake->offered_group_id = 0; client_shares_end = p + client_shares_len; /* We try to find a suitable key share entry and copy it to the * handshake context. Later, we have to find out whether we can do * something with the provided key share or whether we have to * dismiss it and send a HelloRetryRequest message. */ while (p < client_shares_end) { uint16_t group; size_t key_exchange_len; const unsigned char *key_exchange; /* * struct { * NamedGroup group; * opaque key_exchange<1..2^16-1>; * } KeyShareEntry; */ MBEDTLS_SSL_CHK_BUF_READ_PTR(p, client_shares_end, 4); group = MBEDTLS_GET_UINT16_BE(p, 0); key_exchange_len = MBEDTLS_GET_UINT16_BE(p, 2); p += 4; key_exchange = p; MBEDTLS_SSL_CHK_BUF_READ_PTR(p, client_shares_end, key_exchange_len); p += key_exchange_len; /* Continue parsing even if we have already found a match, * for input validation purposes. */ if (!mbedtls_ssl_named_group_is_offered(ssl, group) || !mbedtls_ssl_named_group_is_supported(group) || ssl->handshake->offered_group_id != 0) { continue; } /* * For now, we only support ECDHE groups. */ if (mbedtls_ssl_tls13_named_group_is_ecdhe(group)) { MBEDTLS_SSL_DEBUG_MSG(2, ("ECDH group: %s (%04x)", mbedtls_ssl_named_group_to_str(group), group)); ret = mbedtls_ssl_tls13_read_public_ecdhe_share( ssl, key_exchange - 2, key_exchange_len + 2); if (ret != 0) { return ret; } } else { MBEDTLS_SSL_DEBUG_MSG(4, ("Unrecognized NamedGroup %u", (unsigned) group)); continue; } ssl->handshake->offered_group_id = group; } if (ssl->handshake->offered_group_id == 0) { MBEDTLS_SSL_DEBUG_MSG(1, ("no matching key share")); return SSL_TLS1_3_PARSE_KEY_SHARES_EXT_NO_MATCH; } return 0; } #endif /* MBEDTLS_ECDH_C */ MBEDTLS_CHECK_RETURN_CRITICAL static int ssl_tls13_client_hello_has_exts(mbedtls_ssl_context *ssl, int exts_mask) { int masked = ssl->handshake->received_extensions & exts_mask; return masked == exts_mask; } #if defined(MBEDTLS_SSL_TLS1_3_KEY_EXCHANGE_MODE_EPHEMERAL_ENABLED) MBEDTLS_CHECK_RETURN_CRITICAL static int ssl_tls13_client_hello_has_exts_for_ephemeral_key_exchange( mbedtls_ssl_context *ssl) { return ssl_tls13_client_hello_has_exts( ssl, MBEDTLS_SSL_EXT_MASK(SUPPORTED_GROUPS) | MBEDTLS_SSL_EXT_MASK(KEY_SHARE) | MBEDTLS_SSL_EXT_MASK(SIG_ALG)); } #endif /* MBEDTLS_SSL_TLS1_3_KEY_EXCHANGE_MODE_EPHEMERAL_ENABLED */ #if defined(MBEDTLS_SSL_TLS1_3_KEY_EXCHANGE_MODE_PSK_ENABLED) MBEDTLS_CHECK_RETURN_CRITICAL static int ssl_tls13_client_hello_has_exts_for_psk_key_exchange( mbedtls_ssl_context *ssl) { return ssl_tls13_client_hello_has_exts( ssl, MBEDTLS_SSL_EXT_MASK(PRE_SHARED_KEY) | MBEDTLS_SSL_EXT_MASK(PSK_KEY_EXCHANGE_MODES)); } #endif /* MBEDTLS_SSL_TLS1_3_KEY_EXCHANGE_MODE_PSK_ENABLED */ #if defined(MBEDTLS_SSL_TLS1_3_KEY_EXCHANGE_MODE_PSK_EPHEMERAL_ENABLED) MBEDTLS_CHECK_RETURN_CRITICAL static int ssl_tls13_client_hello_has_exts_for_psk_ephemeral_key_exchange( mbedtls_ssl_context *ssl) { return ssl_tls13_client_hello_has_exts( ssl, MBEDTLS_SSL_EXT_MASK(SUPPORTED_GROUPS) | MBEDTLS_SSL_EXT_MASK(KEY_SHARE) | MBEDTLS_SSL_EXT_MASK(PRE_SHARED_KEY) | MBEDTLS_SSL_EXT_MASK(PSK_KEY_EXCHANGE_MODES)); } #endif /* MBEDTLS_SSL_TLS1_3_KEY_EXCHANGE_MODE_PSK_EPHEMERAL_ENABLED */ MBEDTLS_CHECK_RETURN_CRITICAL static int ssl_tls13_check_ephemeral_key_exchange(mbedtls_ssl_context *ssl) { #if defined(MBEDTLS_SSL_TLS1_3_KEY_EXCHANGE_MODE_EPHEMERAL_ENABLED) return mbedtls_ssl_conf_tls13_ephemeral_enabled(ssl) && ssl_tls13_client_hello_has_exts_for_ephemeral_key_exchange(ssl); #else ((void) ssl); return 0; #endif } MBEDTLS_CHECK_RETURN_CRITICAL static int ssl_tls13_check_psk_key_exchange(mbedtls_ssl_context *ssl) { #if defined(MBEDTLS_SSL_TLS1_3_KEY_EXCHANGE_MODE_PSK_ENABLED) return mbedtls_ssl_conf_tls13_psk_enabled(ssl) && mbedtls_ssl_tls13_psk_enabled(ssl) && ssl_tls13_client_hello_has_exts_for_psk_key_exchange(ssl); #else ((void) ssl); return 0; #endif } MBEDTLS_CHECK_RETURN_CRITICAL static int ssl_tls13_check_psk_ephemeral_key_exchange(mbedtls_ssl_context *ssl) { #if defined(MBEDTLS_SSL_TLS1_3_KEY_EXCHANGE_MODE_PSK_EPHEMERAL_ENABLED) return mbedtls_ssl_conf_tls13_psk_ephemeral_enabled(ssl) && mbedtls_ssl_tls13_psk_ephemeral_enabled(ssl) && ssl_tls13_client_hello_has_exts_for_psk_ephemeral_key_exchange(ssl); #else ((void) ssl); return 0; #endif } static int ssl_tls13_determine_key_exchange_mode(mbedtls_ssl_context *ssl) { /* * Determine the key exchange algorithm to use. * There are three types of key exchanges supported in TLS 1.3: * - (EC)DH with ECDSA, * - (EC)DH with PSK, * - plain PSK. * * The PSK-based key exchanges may additionally be used with 0-RTT. * * Our built-in order of preference is * 1 ) (EC)DHE-PSK Mode ( psk_ephemeral ) * 2 ) Certificate Mode ( ephemeral ) * 3 ) Plain PSK Mode ( psk ) */ ssl->handshake->key_exchange_mode = MBEDTLS_SSL_TLS1_3_KEY_EXCHANGE_MODE_NONE; if (ssl_tls13_check_psk_ephemeral_key_exchange(ssl)) { ssl->handshake->key_exchange_mode = MBEDTLS_SSL_TLS1_3_KEY_EXCHANGE_MODE_PSK_EPHEMERAL; MBEDTLS_SSL_DEBUG_MSG(2, ("key exchange mode: psk_ephemeral")); } else if (ssl_tls13_check_ephemeral_key_exchange(ssl)) { ssl->handshake->key_exchange_mode = MBEDTLS_SSL_TLS1_3_KEY_EXCHANGE_MODE_EPHEMERAL; MBEDTLS_SSL_DEBUG_MSG(2, ("key exchange mode: ephemeral")); } else if (ssl_tls13_check_psk_key_exchange(ssl)) { ssl->handshake->key_exchange_mode = MBEDTLS_SSL_TLS1_3_KEY_EXCHANGE_MODE_PSK; MBEDTLS_SSL_DEBUG_MSG(2, ("key exchange mode: psk")); } else { MBEDTLS_SSL_DEBUG_MSG( 1, ("ClientHello message misses mandatory extensions.")); MBEDTLS_SSL_PEND_FATAL_ALERT(MBEDTLS_SSL_ALERT_MSG_MISSING_EXTENSION, MBEDTLS_ERR_SSL_ILLEGAL_PARAMETER); return MBEDTLS_ERR_SSL_ILLEGAL_PARAMETER; } return 0; } #if defined(MBEDTLS_X509_CRT_PARSE_C) && \ defined(MBEDTLS_SSL_TLS1_3_KEY_EXCHANGE_MODE_EPHEMERAL_ENABLED) #if defined(MBEDTLS_USE_PSA_CRYPTO) static psa_algorithm_t ssl_tls13_iana_sig_alg_to_psa_alg(uint16_t sig_alg) { switch (sig_alg) { case MBEDTLS_TLS1_3_SIG_ECDSA_SECP256R1_SHA256: return PSA_ALG_ECDSA(PSA_ALG_SHA_256); case MBEDTLS_TLS1_3_SIG_ECDSA_SECP384R1_SHA384: return PSA_ALG_ECDSA(PSA_ALG_SHA_384); case MBEDTLS_TLS1_3_SIG_ECDSA_SECP521R1_SHA512: return PSA_ALG_ECDSA(PSA_ALG_SHA_512); case MBEDTLS_TLS1_3_SIG_RSA_PSS_RSAE_SHA256: return PSA_ALG_RSA_PSS(PSA_ALG_SHA_256); case MBEDTLS_TLS1_3_SIG_RSA_PSS_RSAE_SHA384: return PSA_ALG_RSA_PSS(PSA_ALG_SHA_384); case MBEDTLS_TLS1_3_SIG_RSA_PSS_RSAE_SHA512: return PSA_ALG_RSA_PSS(PSA_ALG_SHA_512); case MBEDTLS_TLS1_3_SIG_RSA_PKCS1_SHA256: return PSA_ALG_RSA_PKCS1V15_SIGN(PSA_ALG_SHA_256); case MBEDTLS_TLS1_3_SIG_RSA_PKCS1_SHA384: return PSA_ALG_RSA_PKCS1V15_SIGN(PSA_ALG_SHA_384); case MBEDTLS_TLS1_3_SIG_RSA_PKCS1_SHA512: return PSA_ALG_RSA_PKCS1V15_SIGN(PSA_ALG_SHA_512); default: return PSA_ALG_NONE; } } #endif /* MBEDTLS_USE_PSA_CRYPTO */ /* * Pick best ( private key, certificate chain ) pair based on the signature * algorithms supported by the client. */ MBEDTLS_CHECK_RETURN_CRITICAL static int ssl_tls13_pick_key_cert(mbedtls_ssl_context *ssl) { mbedtls_ssl_key_cert *key_cert, *key_cert_list; const uint16_t *sig_alg = ssl->handshake->received_sig_algs; #if defined(MBEDTLS_SSL_SERVER_NAME_INDICATION) if (ssl->handshake->sni_key_cert != NULL) { key_cert_list = ssl->handshake->sni_key_cert; } else #endif /* MBEDTLS_SSL_SERVER_NAME_INDICATION */ key_cert_list = ssl->conf->key_cert; if (key_cert_list == NULL) { MBEDTLS_SSL_DEBUG_MSG(3, ("server has no certificate")); return -1; } for (; *sig_alg != MBEDTLS_TLS1_3_SIG_NONE; sig_alg++) { if (!mbedtls_ssl_sig_alg_is_offered(ssl, *sig_alg)) { continue; } if (!mbedtls_ssl_tls13_sig_alg_for_cert_verify_is_supported(*sig_alg)) { continue; } for (key_cert = key_cert_list; key_cert != NULL; key_cert = key_cert->next) { #if defined(MBEDTLS_USE_PSA_CRYPTO) psa_algorithm_t psa_alg = PSA_ALG_NONE; #endif /* MBEDTLS_USE_PSA_CRYPTO */ MBEDTLS_SSL_DEBUG_CRT(3, "certificate (chain) candidate", key_cert->cert); /* * This avoids sending the client a cert it'll reject based on * keyUsage or other extensions. */ if (mbedtls_x509_crt_check_key_usage( key_cert->cert, MBEDTLS_X509_KU_DIGITAL_SIGNATURE) != 0 || mbedtls_x509_crt_check_extended_key_usage( key_cert->cert, MBEDTLS_OID_SERVER_AUTH, MBEDTLS_OID_SIZE(MBEDTLS_OID_SERVER_AUTH)) != 0) { MBEDTLS_SSL_DEBUG_MSG(3, ("certificate mismatch: " "(extended) key usage extension")); continue; } MBEDTLS_SSL_DEBUG_MSG(3, ("ssl_tls13_pick_key_cert:" "check signature algorithm %s [%04x]", mbedtls_ssl_sig_alg_to_str(*sig_alg), *sig_alg)); #if defined(MBEDTLS_USE_PSA_CRYPTO) psa_alg = ssl_tls13_iana_sig_alg_to_psa_alg(*sig_alg); #endif /* MBEDTLS_USE_PSA_CRYPTO */ if (mbedtls_ssl_tls13_check_sig_alg_cert_key_match( *sig_alg, &key_cert->cert->pk) #if defined(MBEDTLS_USE_PSA_CRYPTO) && psa_alg != PSA_ALG_NONE && mbedtls_pk_can_do_ext(&key_cert->cert->pk, psa_alg, PSA_KEY_USAGE_SIGN_HASH) == 1 #endif /* MBEDTLS_USE_PSA_CRYPTO */ ) { ssl->handshake->key_cert = key_cert; MBEDTLS_SSL_DEBUG_MSG(3, ("ssl_tls13_pick_key_cert:" "selected signature algorithm" " %s [%04x]", mbedtls_ssl_sig_alg_to_str(*sig_alg), *sig_alg)); MBEDTLS_SSL_DEBUG_CRT( 3, "selected certificate (chain)", ssl->handshake->key_cert->cert); return 0; } } } MBEDTLS_SSL_DEBUG_MSG(2, ("ssl_tls13_pick_key_cert:" "no suitable certificate found")); return -1; } #endif /* MBEDTLS_X509_CRT_PARSE_C && MBEDTLS_SSL_TLS1_3_KEY_EXCHANGE_MODE_EPHEMERAL_ENABLED */ /* * * STATE HANDLING: ClientHello * * There are three possible classes of outcomes when parsing the ClientHello: * * 1) The ClientHello was well-formed and matched the server's configuration. * * In this case, the server progresses to sending its ServerHello. * * 2) The ClientHello was well-formed but didn't match the server's * configuration. * * For example, the client might not have offered a key share which * the server supports, or the server might require a cookie. * * In this case, the server sends a HelloRetryRequest. * * 3) The ClientHello was ill-formed * * In this case, we abort the handshake. * */ /* * Structure of this message: * * uint16 ProtocolVersion; * opaque Random[32]; * uint8 CipherSuite[2]; // Cryptographic suite selector * * struct { * ProtocolVersion legacy_version = 0x0303; // TLS v1.2 * Random random; * opaque legacy_session_id<0..32>; * CipherSuite cipher_suites<2..2^16-2>; * opaque legacy_compression_methods<1..2^8-1>; * Extension extensions<8..2^16-1>; * } ClientHello; */ #define SSL_CLIENT_HELLO_OK 0 #define SSL_CLIENT_HELLO_HRR_REQUIRED 1 MBEDTLS_CHECK_RETURN_CRITICAL static int ssl_tls13_parse_client_hello(mbedtls_ssl_context *ssl, const unsigned char *buf, const unsigned char *end) { int ret = MBEDTLS_ERR_ERROR_CORRUPTION_DETECTED; const unsigned char *p = buf; size_t legacy_session_id_len; size_t cipher_suites_len; const unsigned char *cipher_suites_end; size_t extensions_len; const unsigned char *extensions_end; mbedtls_ssl_handshake_params *handshake = ssl->handshake; int hrr_required = 0; #if defined(MBEDTLS_SSL_TLS1_3_KEY_EXCHANGE_MODE_SOME_PSK_ENABLED) const unsigned char *cipher_suites; const unsigned char *pre_shared_key_ext = NULL; const unsigned char *pre_shared_key_ext_end = NULL; #endif /* * ClientHello layout: * 0 . 1 protocol version * 2 . 33 random bytes * 34 . 34 session id length ( 1 byte ) * 35 . 34+x session id * .. . .. ciphersuite list length ( 2 bytes ) * .. . .. ciphersuite list * .. . .. compression alg. list length ( 1 byte ) * .. . .. compression alg. list * .. . .. extensions length ( 2 bytes, optional ) * .. . .. extensions ( optional ) */ /* * Minimal length ( with everything empty and extensions omitted ) is * 2 + 32 + 1 + 2 + 1 = 38 bytes. Check that first, so that we can * read at least up to session id length without worrying. */ MBEDTLS_SSL_CHK_BUF_READ_PTR(p, end, 38); /* ... * ProtocolVersion legacy_version = 0x0303; // TLS 1.2 * ... * with ProtocolVersion defined as: * uint16 ProtocolVersion; */ if (mbedtls_ssl_read_version(p, ssl->conf->transport) != MBEDTLS_SSL_VERSION_TLS1_2) { MBEDTLS_SSL_DEBUG_MSG(1, ("Unsupported version of TLS.")); MBEDTLS_SSL_PEND_FATAL_ALERT(MBEDTLS_SSL_ALERT_MSG_PROTOCOL_VERSION, MBEDTLS_ERR_SSL_BAD_PROTOCOL_VERSION); return MBEDTLS_ERR_SSL_BAD_PROTOCOL_VERSION; } p += 2; /* * Only support TLS 1.3 currently, temporarily set the version. */ ssl->tls_version = MBEDTLS_SSL_VERSION_TLS1_3; #if defined(MBEDTLS_SSL_SESSION_TICKETS) /* Store minor version for later use with ticket serialization. */ ssl->session_negotiate->tls_version = MBEDTLS_SSL_VERSION_TLS1_3; ssl->session_negotiate->endpoint = ssl->conf->endpoint; #endif /* ... * Random random; * ... * with Random defined as: * opaque Random[32]; */ MBEDTLS_SSL_DEBUG_BUF(3, "client hello, random bytes", p, MBEDTLS_CLIENT_HELLO_RANDOM_LEN); memcpy(&handshake->randbytes[0], p, MBEDTLS_CLIENT_HELLO_RANDOM_LEN); p += MBEDTLS_CLIENT_HELLO_RANDOM_LEN; /* ... * opaque legacy_session_id<0..32>; * ... */ legacy_session_id_len = p[0]; p++; if (legacy_session_id_len > sizeof(ssl->session_negotiate->id)) { MBEDTLS_SSL_DEBUG_MSG(1, ("bad client hello message")); return MBEDTLS_ERR_SSL_DECODE_ERROR; } ssl->session_negotiate->id_len = legacy_session_id_len; MBEDTLS_SSL_DEBUG_BUF(3, "client hello, session id", p, legacy_session_id_len); /* * Check we have enough data for the legacy session identifier * and the ciphersuite list length. */ MBEDTLS_SSL_CHK_BUF_READ_PTR(p, end, legacy_session_id_len + 2); memcpy(&ssl->session_negotiate->id[0], p, legacy_session_id_len); p += legacy_session_id_len; cipher_suites_len = MBEDTLS_GET_UINT16_BE(p, 0); p += 2; /* Check we have enough data for the ciphersuite list, the legacy * compression methods and the length of the extensions. * * cipher_suites cipher_suites_len bytes * legacy_compression_methods 2 bytes * extensions_len 2 bytes */ MBEDTLS_SSL_CHK_BUF_READ_PTR(p, end, cipher_suites_len + 2 + 2); /* ... * CipherSuite cipher_suites<2..2^16-2>; * ... * with CipherSuite defined as: * uint8 CipherSuite[2]; */ #if defined(MBEDTLS_SSL_TLS1_3_KEY_EXCHANGE_MODE_SOME_PSK_ENABLED) cipher_suites = p; #endif cipher_suites_end = p + cipher_suites_len; MBEDTLS_SSL_DEBUG_BUF(3, "client hello, ciphersuitelist", p, cipher_suites_len); /* * Search for a matching ciphersuite */ for (; p < cipher_suites_end; p += 2) { uint16_t cipher_suite; const mbedtls_ssl_ciphersuite_t *ciphersuite_info; MBEDTLS_SSL_CHK_BUF_READ_PTR(p, cipher_suites_end, 2); cipher_suite = MBEDTLS_GET_UINT16_BE(p, 0); ciphersuite_info = ssl_tls13_validate_peer_ciphersuite( ssl, cipher_suite); if (ciphersuite_info == NULL) { continue; } ssl->session_negotiate->ciphersuite = cipher_suite; handshake->ciphersuite_info = ciphersuite_info; MBEDTLS_SSL_DEBUG_MSG(2, ("selected ciphersuite: %04x - %s", cipher_suite, ciphersuite_info->name)); } if (handshake->ciphersuite_info == NULL) { MBEDTLS_SSL_PEND_FATAL_ALERT(MBEDTLS_SSL_ALERT_MSG_HANDSHAKE_FAILURE, MBEDTLS_ERR_SSL_HANDSHAKE_FAILURE); return MBEDTLS_ERR_SSL_HANDSHAKE_FAILURE; } /* ... * opaque legacy_compression_methods<1..2^8-1>; * ... */ if (p[0] != 1 || p[1] != MBEDTLS_SSL_COMPRESS_NULL) { MBEDTLS_SSL_DEBUG_MSG(1, ("bad legacy compression method")); MBEDTLS_SSL_PEND_FATAL_ALERT(MBEDTLS_SSL_ALERT_MSG_ILLEGAL_PARAMETER, MBEDTLS_ERR_SSL_ILLEGAL_PARAMETER); return MBEDTLS_ERR_SSL_ILLEGAL_PARAMETER; } p += 2; /* ... * Extension extensions<8..2^16-1>; * ... * with Extension defined as: * struct { * ExtensionType extension_type; * opaque extension_data<0..2^16-1>; * } Extension; */ extensions_len = MBEDTLS_GET_UINT16_BE(p, 0); p += 2; MBEDTLS_SSL_CHK_BUF_READ_PTR(p, end, extensions_len); extensions_end = p + extensions_len; MBEDTLS_SSL_DEBUG_BUF(3, "client hello extensions", p, extensions_len); handshake->received_extensions = MBEDTLS_SSL_EXT_MASK_NONE; while (p < extensions_end) { unsigned int extension_type; size_t extension_data_len; const unsigned char *extension_data_end; /* RFC 8446, section 4.2.11 * * The "pre_shared_key" extension MUST be the last extension in the * ClientHello (this facilitates implementation as described below). * Servers MUST check that it is the last extension and otherwise fail * the handshake with an "illegal_parameter" alert. */ if (handshake->received_extensions & MBEDTLS_SSL_EXT_MASK(PRE_SHARED_KEY)) { MBEDTLS_SSL_DEBUG_MSG( 3, ("pre_shared_key is not last extension.")); MBEDTLS_SSL_PEND_FATAL_ALERT( MBEDTLS_SSL_ALERT_MSG_ILLEGAL_PARAMETER, MBEDTLS_ERR_SSL_ILLEGAL_PARAMETER); return MBEDTLS_ERR_SSL_ILLEGAL_PARAMETER; } MBEDTLS_SSL_CHK_BUF_READ_PTR(p, extensions_end, 4); extension_type = MBEDTLS_GET_UINT16_BE(p, 0); extension_data_len = MBEDTLS_GET_UINT16_BE(p, 2); p += 4; MBEDTLS_SSL_CHK_BUF_READ_PTR(p, extensions_end, extension_data_len); extension_data_end = p + extension_data_len; ret = mbedtls_ssl_tls13_check_received_extension( ssl, MBEDTLS_SSL_HS_CLIENT_HELLO, extension_type, MBEDTLS_SSL_TLS1_3_ALLOWED_EXTS_OF_CH); if (ret != 0) { return ret; } switch (extension_type) { #if defined(MBEDTLS_SSL_SERVER_NAME_INDICATION) case MBEDTLS_TLS_EXT_SERVERNAME: MBEDTLS_SSL_DEBUG_MSG(3, ("found ServerName extension")); ret = mbedtls_ssl_parse_server_name_ext(ssl, p, extension_data_end); if (ret != 0) { MBEDTLS_SSL_DEBUG_RET( 1, "mbedtls_ssl_parse_servername_ext", ret); return ret; } break; #endif /* MBEDTLS_SSL_SERVER_NAME_INDICATION */ #if defined(MBEDTLS_ECDH_C) case MBEDTLS_TLS_EXT_SUPPORTED_GROUPS: MBEDTLS_SSL_DEBUG_MSG(3, ("found supported group extension")); /* Supported Groups Extension * * When sent by the client, the "supported_groups" extension * indicates the named groups which the client supports, * ordered from most preferred to least preferred. */ ret = ssl_tls13_parse_supported_groups_ext( ssl, p, extension_data_end); if (ret != 0) { MBEDTLS_SSL_DEBUG_RET(1, "mbedtls_ssl_parse_supported_groups_ext", ret); return ret; } break; #endif /* MBEDTLS_ECDH_C */ #if defined(MBEDTLS_ECDH_C) case MBEDTLS_TLS_EXT_KEY_SHARE: MBEDTLS_SSL_DEBUG_MSG(3, ("found key share extension")); /* * Key Share Extension * * When sent by the client, the "key_share" extension * contains the endpoint's cryptographic parameters for * ECDHE/DHE key establishment methods. */ ret = ssl_tls13_parse_key_shares_ext( ssl, p, extension_data_end); if (ret == SSL_TLS1_3_PARSE_KEY_SHARES_EXT_NO_MATCH) { MBEDTLS_SSL_DEBUG_MSG(2, ("HRR needed ")); hrr_required = 1; } if (ret < 0) { MBEDTLS_SSL_DEBUG_RET( 1, "ssl_tls13_parse_key_shares_ext", ret); return ret; } break; #endif /* MBEDTLS_ECDH_C */ case MBEDTLS_TLS_EXT_SUPPORTED_VERSIONS: MBEDTLS_SSL_DEBUG_MSG(3, ("found supported versions extension")); ret = ssl_tls13_parse_supported_versions_ext( ssl, p, extension_data_end); if (ret != 0) { MBEDTLS_SSL_DEBUG_RET(1, ("ssl_tls13_parse_supported_versions_ext"), ret); return ret; } break; #if defined(MBEDTLS_SSL_TLS1_3_KEY_EXCHANGE_MODE_SOME_PSK_ENABLED) case MBEDTLS_TLS_EXT_PSK_KEY_EXCHANGE_MODES: MBEDTLS_SSL_DEBUG_MSG(3, ("found psk key exchange modes extension")); ret = ssl_tls13_parse_key_exchange_modes_ext( ssl, p, extension_data_end); if (ret != 0) { MBEDTLS_SSL_DEBUG_RET( 1, "ssl_tls13_parse_key_exchange_modes_ext", ret); return ret; } break; #endif case MBEDTLS_TLS_EXT_PRE_SHARED_KEY: MBEDTLS_SSL_DEBUG_MSG(3, ("found pre_shared_key extension")); if ((handshake->received_extensions & MBEDTLS_SSL_EXT_MASK(PSK_KEY_EXCHANGE_MODES)) == 0) { MBEDTLS_SSL_PEND_FATAL_ALERT( MBEDTLS_SSL_ALERT_MSG_ILLEGAL_PARAMETER, MBEDTLS_ERR_SSL_ILLEGAL_PARAMETER); return MBEDTLS_ERR_SSL_ILLEGAL_PARAMETER; } #if defined(MBEDTLS_SSL_TLS1_3_KEY_EXCHANGE_MODE_SOME_PSK_ENABLED) /* Delay processing of the PSK identity once we have * found out which algorithms to use. We keep a pointer * to the buffer and the size for later processing. */ pre_shared_key_ext = p; pre_shared_key_ext_end = extension_data_end; #endif /* MBEDTLS_SSL_TLS1_3_KEY_EXCHANGE_MODE_SOME_PSK_ENABLED */ break; #if defined(MBEDTLS_SSL_ALPN) case MBEDTLS_TLS_EXT_ALPN: MBEDTLS_SSL_DEBUG_MSG(3, ("found alpn extension")); ret = mbedtls_ssl_parse_alpn_ext(ssl, p, extension_data_end); if (ret != 0) { MBEDTLS_SSL_DEBUG_RET( 1, ("mbedtls_ssl_parse_alpn_ext"), ret); return ret; } break; #endif /* MBEDTLS_SSL_ALPN */ #if defined(MBEDTLS_SSL_TLS1_3_KEY_EXCHANGE_MODE_EPHEMERAL_ENABLED) case MBEDTLS_TLS_EXT_SIG_ALG: MBEDTLS_SSL_DEBUG_MSG(3, ("found signature_algorithms extension")); ret = mbedtls_ssl_parse_sig_alg_ext( ssl, p, extension_data_end); if (ret != 0) { MBEDTLS_SSL_DEBUG_MSG(1, ( "ssl_parse_supported_signature_algorithms_server_ext ( %d )", ret)); return ret; } break; #endif /* MBEDTLS_SSL_TLS1_3_KEY_EXCHANGE_MODE_EPHEMERAL_ENABLED */ default: MBEDTLS_SSL_PRINT_EXT( 3, MBEDTLS_SSL_HS_CLIENT_HELLO, extension_type, "( ignored )"); break; } p += extension_data_len; } MBEDTLS_SSL_PRINT_EXTS(3, MBEDTLS_SSL_HS_CLIENT_HELLO, handshake->received_extensions); mbedtls_ssl_add_hs_hdr_to_checksum(ssl, MBEDTLS_SSL_HS_CLIENT_HELLO, p - buf); #if defined(MBEDTLS_SSL_TLS1_3_KEY_EXCHANGE_MODE_SOME_PSK_ENABLED) /* Update checksum with either * - The entire content of the CH message, if no PSK extension is present * - The content up to but excluding the PSK extension, if present. */ /* If we've settled on a PSK-based exchange, parse PSK identity ext */ if (mbedtls_ssl_tls13_some_psk_enabled(ssl) && mbedtls_ssl_conf_tls13_some_psk_enabled(ssl) && (handshake->received_extensions & MBEDTLS_SSL_EXT_MASK(PRE_SHARED_KEY))) { handshake->update_checksum(ssl, buf, pre_shared_key_ext - buf); ret = ssl_tls13_parse_pre_shared_key_ext(ssl, pre_shared_key_ext, pre_shared_key_ext_end, cipher_suites, cipher_suites_end); if (ret == MBEDTLS_ERR_SSL_UNKNOWN_IDENTITY) { handshake->received_extensions &= ~MBEDTLS_SSL_EXT_MASK(PRE_SHARED_KEY); } else if (ret != 0) { MBEDTLS_SSL_DEBUG_RET( 1, "ssl_tls13_parse_pre_shared_key_ext", ret); return ret; } } else #endif /* MBEDTLS_SSL_TLS1_3_KEY_EXCHANGE_MODE_SOME_PSK_ENABLED */ { handshake->update_checksum(ssl, buf, p - buf); } ret = ssl_tls13_determine_key_exchange_mode(ssl); if (ret < 0) { return ret; } mbedtls_ssl_optimize_checksum(ssl, handshake->ciphersuite_info); return hrr_required ? SSL_CLIENT_HELLO_HRR_REQUIRED : SSL_CLIENT_HELLO_OK; } /* Update the handshake state machine */ MBEDTLS_CHECK_RETURN_CRITICAL static int ssl_tls13_postprocess_client_hello(mbedtls_ssl_context *ssl) { int ret = MBEDTLS_ERR_ERROR_CORRUPTION_DETECTED; /* * Server certificate selection */ if (ssl->conf->f_cert_cb && (ret = ssl->conf->f_cert_cb(ssl)) != 0) { MBEDTLS_SSL_DEBUG_RET(1, "f_cert_cb", ret); return ret; } #if defined(MBEDTLS_SSL_SERVER_NAME_INDICATION) ssl->handshake->sni_name = NULL; ssl->handshake->sni_name_len = 0; #endif /* MBEDTLS_SSL_SERVER_NAME_INDICATION */ ret = mbedtls_ssl_tls13_key_schedule_stage_early(ssl); if (ret != 0) { MBEDTLS_SSL_DEBUG_RET(1, "mbedtls_ssl_tls1_3_key_schedule_stage_early", ret); return ret; } return 0; } /* * Main entry point from the state machine; orchestrates the otherfunctions. */ MBEDTLS_CHECK_RETURN_CRITICAL static int ssl_tls13_process_client_hello(mbedtls_ssl_context *ssl) { int ret = MBEDTLS_ERR_ERROR_CORRUPTION_DETECTED; unsigned char *buf = NULL; size_t buflen = 0; int parse_client_hello_ret; MBEDTLS_SSL_DEBUG_MSG(2, ("=> parse client hello")); MBEDTLS_SSL_PROC_CHK(mbedtls_ssl_tls13_fetch_handshake_msg( ssl, MBEDTLS_SSL_HS_CLIENT_HELLO, &buf, &buflen)); MBEDTLS_SSL_PROC_CHK_NEG(ssl_tls13_parse_client_hello(ssl, buf, buf + buflen)); parse_client_hello_ret = ret; /* Store return value of parse_client_hello, * only SSL_CLIENT_HELLO_OK or * SSL_CLIENT_HELLO_HRR_REQUIRED at this * stage as negative error codes are handled * by MBEDTLS_SSL_PROC_CHK_NEG. */ MBEDTLS_SSL_PROC_CHK(ssl_tls13_postprocess_client_hello(ssl)); if (parse_client_hello_ret == SSL_CLIENT_HELLO_OK) { mbedtls_ssl_handshake_set_state(ssl, MBEDTLS_SSL_SERVER_HELLO); } else { mbedtls_ssl_handshake_set_state(ssl, MBEDTLS_SSL_HELLO_RETRY_REQUEST); } cleanup: MBEDTLS_SSL_DEBUG_MSG(2, ("<= parse client hello")); return ret; } /* * Handler for MBEDTLS_SSL_SERVER_HELLO */ MBEDTLS_CHECK_RETURN_CRITICAL static int ssl_tls13_prepare_server_hello(mbedtls_ssl_context *ssl) { int ret = MBEDTLS_ERR_ERROR_CORRUPTION_DETECTED; unsigned char *server_randbytes = ssl->handshake->randbytes + MBEDTLS_CLIENT_HELLO_RANDOM_LEN; if (ssl->conf->f_rng == NULL) { MBEDTLS_SSL_DEBUG_MSG(1, ("no RNG provided")); return MBEDTLS_ERR_SSL_NO_RNG; } if ((ret = ssl->conf->f_rng(ssl->conf->p_rng, server_randbytes, MBEDTLS_SERVER_HELLO_RANDOM_LEN)) != 0) { MBEDTLS_SSL_DEBUG_RET(1, "f_rng", ret); return ret; } MBEDTLS_SSL_DEBUG_BUF(3, "server hello, random bytes", server_randbytes, MBEDTLS_SERVER_HELLO_RANDOM_LEN); #if defined(MBEDTLS_HAVE_TIME) ssl->session_negotiate->start = time(NULL); #endif /* MBEDTLS_HAVE_TIME */ return ret; } /* * ssl_tls13_write_server_hello_supported_versions_ext (): * * struct { * ProtocolVersion selected_version; * } SupportedVersions; */ MBEDTLS_CHECK_RETURN_CRITICAL static int ssl_tls13_write_server_hello_supported_versions_ext( mbedtls_ssl_context *ssl, unsigned char *buf, unsigned char *end, size_t *out_len) { *out_len = 0; MBEDTLS_SSL_DEBUG_MSG(3, ("server hello, write selected version")); /* Check if we have space to write the extension: * - extension_type (2 bytes) * - extension_data_length (2 bytes) * - selected_version (2 bytes) */ MBEDTLS_SSL_CHK_BUF_PTR(buf, end, 6); MBEDTLS_PUT_UINT16_BE(MBEDTLS_TLS_EXT_SUPPORTED_VERSIONS, buf, 0); MBEDTLS_PUT_UINT16_BE(2, buf, 2); mbedtls_ssl_write_version(buf + 4, ssl->conf->transport, ssl->tls_version); MBEDTLS_SSL_DEBUG_MSG(3, ("supported version: [%04x]", ssl->tls_version)); *out_len = 6; mbedtls_ssl_tls13_set_hs_sent_ext_mask( ssl, MBEDTLS_TLS_EXT_SUPPORTED_VERSIONS); return 0; } /* Generate and export a single key share. For hybrid KEMs, this can * be called multiple times with the different components of the hybrid. */ MBEDTLS_CHECK_RETURN_CRITICAL static int ssl_tls13_generate_and_write_key_share(mbedtls_ssl_context *ssl, uint16_t named_group, unsigned char *buf, unsigned char *end, size_t *out_len) { int ret = MBEDTLS_ERR_ERROR_CORRUPTION_DETECTED; *out_len = 0; #if defined(MBEDTLS_ECDH_C) if (mbedtls_ssl_tls13_named_group_is_ecdhe(named_group)) { ret = mbedtls_ssl_tls13_generate_and_write_ecdh_key_exchange( ssl, named_group, buf, end, out_len); if (ret != 0) { MBEDTLS_SSL_DEBUG_RET( 1, "mbedtls_ssl_tls13_generate_and_write_ecdh_key_exchange", ret); return ret; } } else #endif /* MBEDTLS_ECDH_C */ if (0 /* Other kinds of KEMs */) { } else { ((void) ssl); ((void) named_group); ((void) buf); ((void) end); ret = MBEDTLS_ERR_SSL_INTERNAL_ERROR; } return ret; } /* * ssl_tls13_write_key_share_ext * * Structure of key_share extension in ServerHello: * * struct { * NamedGroup group; * opaque key_exchange<1..2^16-1>; * } KeyShareEntry; * struct { * KeyShareEntry server_share; * } KeyShareServerHello; */ MBEDTLS_CHECK_RETURN_CRITICAL static int ssl_tls13_write_key_share_ext(mbedtls_ssl_context *ssl, unsigned char *buf, unsigned char *end, size_t *out_len) { int ret = MBEDTLS_ERR_ERROR_CORRUPTION_DETECTED; unsigned char *p = buf; uint16_t group = ssl->handshake->offered_group_id; unsigned char *server_share = buf + 4; size_t key_exchange_length; *out_len = 0; MBEDTLS_SSL_DEBUG_MSG(3, ("server hello, adding key share extension")); MBEDTLS_SSL_DEBUG_MSG(2, ("server hello, write selected_group: %s (%04x)", mbedtls_ssl_named_group_to_str(group), group)); /* Check if we have space for header and length fields: * - extension_type (2 bytes) * - extension_data_length (2 bytes) * - group (2 bytes) * - key_exchange_length (2 bytes) */ MBEDTLS_SSL_CHK_BUF_PTR(p, end, 8); MBEDTLS_PUT_UINT16_BE(MBEDTLS_TLS_EXT_KEY_SHARE, p, 0); MBEDTLS_PUT_UINT16_BE(group, server_share, 0); p += 8; /* When we introduce PQC-ECDHE hybrids, we'll want to call this * function multiple times. */ ret = ssl_tls13_generate_and_write_key_share( ssl, group, server_share + 4, end, &key_exchange_length); if (ret != 0) { return ret; } p += key_exchange_length; MBEDTLS_PUT_UINT16_BE(key_exchange_length, server_share + 2, 0); MBEDTLS_PUT_UINT16_BE(p - server_share, buf, 2); *out_len = p - buf; mbedtls_ssl_tls13_set_hs_sent_ext_mask(ssl, MBEDTLS_TLS_EXT_KEY_SHARE); return 0; } MBEDTLS_CHECK_RETURN_CRITICAL static int ssl_tls13_write_hrr_key_share_ext(mbedtls_ssl_context *ssl, unsigned char *buf, unsigned char *end, size_t *out_len) { uint16_t selected_group = ssl->handshake->hrr_selected_group; /* key_share Extension * * struct { * select (Handshake.msg_type) { * ... * case hello_retry_request: * NamedGroup selected_group; * ... * }; * } KeyShare; */ *out_len = 0; /* * For a pure PSK key exchange, there is no group to agree upon. The purpose * of the HRR is then to transmit a cookie to force the client to demonstrate * reachability at their apparent network address (primarily useful for DTLS). */ if (!mbedtls_ssl_tls13_key_exchange_mode_with_ephemeral(ssl)) { return 0; } /* We should only send the key_share extension if the client's initial * key share was not acceptable. */ if (ssl->handshake->offered_group_id != 0) { MBEDTLS_SSL_DEBUG_MSG(4, ("Skip key_share extension in HRR")); return 0; } if (selected_group == 0) { MBEDTLS_SSL_DEBUG_MSG(1, ("no matching named group found")); return MBEDTLS_ERR_SSL_HANDSHAKE_FAILURE; } /* Check if we have enough space: * - extension_type (2 bytes) * - extension_data_length (2 bytes) * - selected_group (2 bytes) */ MBEDTLS_SSL_CHK_BUF_PTR(buf, end, 6); MBEDTLS_PUT_UINT16_BE(MBEDTLS_TLS_EXT_KEY_SHARE, buf, 0); MBEDTLS_PUT_UINT16_BE(2, buf, 2); MBEDTLS_PUT_UINT16_BE(selected_group, buf, 4); MBEDTLS_SSL_DEBUG_MSG(3, ("HRR selected_group: %s (%x)", mbedtls_ssl_named_group_to_str(selected_group), selected_group)); *out_len = 6; mbedtls_ssl_tls13_set_hs_sent_ext_mask(ssl, MBEDTLS_TLS_EXT_KEY_SHARE); return 0; } /* * Structure of ServerHello message: * * struct { * ProtocolVersion legacy_version = 0x0303; // TLS v1.2 * Random random; * opaque legacy_session_id_echo<0..32>; * CipherSuite cipher_suite; * uint8 legacy_compression_method = 0; * Extension extensions<6..2^16-1>; * } ServerHello; */ MBEDTLS_CHECK_RETURN_CRITICAL static int ssl_tls13_write_server_hello_body(mbedtls_ssl_context *ssl, unsigned char *buf, unsigned char *end, size_t *out_len, int is_hrr) { int ret = MBEDTLS_ERR_ERROR_CORRUPTION_DETECTED; unsigned char *p = buf; unsigned char *p_extensions_len; size_t output_len; *out_len = 0; ssl->handshake->sent_extensions = MBEDTLS_SSL_EXT_MASK_NONE; /* ... * ProtocolVersion legacy_version = 0x0303; // TLS 1.2 * ... * with ProtocolVersion defined as: * uint16 ProtocolVersion; */ MBEDTLS_SSL_CHK_BUF_PTR(p, end, 2); MBEDTLS_PUT_UINT16_BE(0x0303, p, 0); p += 2; /* ... * Random random; * ... * with Random defined as: * opaque Random[MBEDTLS_SERVER_HELLO_RANDOM_LEN]; */ MBEDTLS_SSL_CHK_BUF_PTR(p, end, MBEDTLS_SERVER_HELLO_RANDOM_LEN); if (is_hrr) { memcpy(p, mbedtls_ssl_tls13_hello_retry_request_magic, MBEDTLS_SERVER_HELLO_RANDOM_LEN); } else { memcpy(p, &ssl->handshake->randbytes[MBEDTLS_CLIENT_HELLO_RANDOM_LEN], MBEDTLS_SERVER_HELLO_RANDOM_LEN); } MBEDTLS_SSL_DEBUG_BUF(3, "server hello, random bytes", p, MBEDTLS_SERVER_HELLO_RANDOM_LEN); p += MBEDTLS_SERVER_HELLO_RANDOM_LEN; /* ... * opaque legacy_session_id_echo<0..32>; * ... */ MBEDTLS_SSL_CHK_BUF_PTR(p, end, 1 + ssl->session_negotiate->id_len); *p++ = (unsigned char) ssl->session_negotiate->id_len; if (ssl->session_negotiate->id_len > 0) { memcpy(p, &ssl->session_negotiate->id[0], ssl->session_negotiate->id_len); p += ssl->session_negotiate->id_len; MBEDTLS_SSL_DEBUG_BUF(3, "session id", ssl->session_negotiate->id, ssl->session_negotiate->id_len); } /* ... * CipherSuite cipher_suite; * ... * with CipherSuite defined as: * uint8 CipherSuite[2]; */ MBEDTLS_SSL_CHK_BUF_PTR(p, end, 2); MBEDTLS_PUT_UINT16_BE(ssl->session_negotiate->ciphersuite, p, 0); p += 2; MBEDTLS_SSL_DEBUG_MSG(3, ("server hello, chosen ciphersuite: %s ( id=%d )", mbedtls_ssl_get_ciphersuite_name( ssl->session_negotiate->ciphersuite), ssl->session_negotiate->ciphersuite)); /* ... * uint8 legacy_compression_method = 0; * ... */ MBEDTLS_SSL_CHK_BUF_PTR(p, end, 1); *p++ = MBEDTLS_SSL_COMPRESS_NULL; /* ... * Extension extensions<6..2^16-1>; * ... * struct { * ExtensionType extension_type; (2 bytes) * opaque extension_data<0..2^16-1>; * } Extension; */ MBEDTLS_SSL_CHK_BUF_PTR(p, end, 2); p_extensions_len = p; p += 2; if ((ret = ssl_tls13_write_server_hello_supported_versions_ext( ssl, p, end, &output_len)) != 0) { MBEDTLS_SSL_DEBUG_RET( 1, "ssl_tls13_write_server_hello_supported_versions_ext", ret); return ret; } p += output_len; if (mbedtls_ssl_tls13_key_exchange_mode_with_ephemeral(ssl)) { if (is_hrr) { ret = ssl_tls13_write_hrr_key_share_ext(ssl, p, end, &output_len); } else { ret = ssl_tls13_write_key_share_ext(ssl, p, end, &output_len); } if (ret != 0) { return ret; } p += output_len; } #if defined(MBEDTLS_SSL_TLS1_3_KEY_EXCHANGE_MODE_SOME_PSK_ENABLED) if (!is_hrr && mbedtls_ssl_tls13_key_exchange_mode_with_psk(ssl)) { ret = ssl_tls13_write_server_pre_shared_key_ext(ssl, p, end, &output_len); if (ret != 0) { MBEDTLS_SSL_DEBUG_RET(1, "ssl_tls13_write_server_pre_shared_key_ext", ret); return ret; } p += output_len; } #endif MBEDTLS_PUT_UINT16_BE(p - p_extensions_len - 2, p_extensions_len, 0); MBEDTLS_SSL_DEBUG_BUF(4, "server hello extensions", p_extensions_len, p - p_extensions_len); *out_len = p - buf; MBEDTLS_SSL_DEBUG_BUF(3, "server hello", buf, *out_len); MBEDTLS_SSL_PRINT_EXTS( 3, is_hrr ? MBEDTLS_SSL_TLS1_3_HS_HELLO_RETRY_REQUEST : MBEDTLS_SSL_HS_SERVER_HELLO, ssl->handshake->sent_extensions); return ret; } MBEDTLS_CHECK_RETURN_CRITICAL static int ssl_tls13_finalize_server_hello(mbedtls_ssl_context *ssl) { int ret = MBEDTLS_ERR_ERROR_CORRUPTION_DETECTED; ret = mbedtls_ssl_tls13_compute_handshake_transform(ssl); if (ret != 0) { MBEDTLS_SSL_DEBUG_RET(1, "mbedtls_ssl_tls13_compute_handshake_transform", ret); return ret; } return ret; } MBEDTLS_CHECK_RETURN_CRITICAL static int ssl_tls13_write_server_hello(mbedtls_ssl_context *ssl) { int ret = MBEDTLS_ERR_ERROR_CORRUPTION_DETECTED; unsigned char *buf; size_t buf_len, msg_len; MBEDTLS_SSL_DEBUG_MSG(2, ("=> write server hello")); MBEDTLS_SSL_PROC_CHK(ssl_tls13_prepare_server_hello(ssl)); MBEDTLS_SSL_PROC_CHK(mbedtls_ssl_start_handshake_msg(ssl, MBEDTLS_SSL_HS_SERVER_HELLO, &buf, &buf_len)); MBEDTLS_SSL_PROC_CHK(ssl_tls13_write_server_hello_body(ssl, buf, buf + buf_len, &msg_len, 0)); mbedtls_ssl_add_hs_msg_to_checksum( ssl, MBEDTLS_SSL_HS_SERVER_HELLO, buf, msg_len); MBEDTLS_SSL_PROC_CHK(mbedtls_ssl_finish_handshake_msg( ssl, buf_len, msg_len)); MBEDTLS_SSL_PROC_CHK(ssl_tls13_finalize_server_hello(ssl)); #if defined(MBEDTLS_SSL_TLS1_3_COMPATIBILITY_MODE) /* The server sends a dummy change_cipher_spec record immediately * after its first handshake message. This may either be after * a ServerHello or a HelloRetryRequest. */ mbedtls_ssl_handshake_set_state( ssl, MBEDTLS_SSL_SERVER_CCS_AFTER_SERVER_HELLO); #else mbedtls_ssl_handshake_set_state(ssl, MBEDTLS_SSL_ENCRYPTED_EXTENSIONS); #endif /* MBEDTLS_SSL_TLS1_3_COMPATIBILITY_MODE */ cleanup: MBEDTLS_SSL_DEBUG_MSG(2, ("<= write server hello")); return ret; } /* * Handler for MBEDTLS_SSL_HELLO_RETRY_REQUEST */ MBEDTLS_CHECK_RETURN_CRITICAL static int ssl_tls13_prepare_hello_retry_request(mbedtls_ssl_context *ssl) { int ret = MBEDTLS_ERR_ERROR_CORRUPTION_DETECTED; if (ssl->handshake->hello_retry_request_count > 0) { MBEDTLS_SSL_DEBUG_MSG(1, ("Too many HRRs")); MBEDTLS_SSL_PEND_FATAL_ALERT(MBEDTLS_SSL_ALERT_MSG_HANDSHAKE_FAILURE, MBEDTLS_ERR_SSL_HANDSHAKE_FAILURE); return MBEDTLS_ERR_SSL_HANDSHAKE_FAILURE; } /* * Create stateless transcript hash for HRR */ MBEDTLS_SSL_DEBUG_MSG(4, ("Reset transcript for HRR")); ret = mbedtls_ssl_reset_transcript_for_hrr(ssl); if (ret != 0) { MBEDTLS_SSL_DEBUG_RET(1, "mbedtls_ssl_reset_transcript_for_hrr", ret); return ret; } mbedtls_ssl_session_reset_msg_layer(ssl, 0); return 0; } MBEDTLS_CHECK_RETURN_CRITICAL static int ssl_tls13_write_hello_retry_request(mbedtls_ssl_context *ssl) { int ret = MBEDTLS_ERR_ERROR_CORRUPTION_DETECTED; unsigned char *buf; size_t buf_len, msg_len; MBEDTLS_SSL_DEBUG_MSG(2, ("=> write hello retry request")); MBEDTLS_SSL_PROC_CHK(ssl_tls13_prepare_hello_retry_request(ssl)); MBEDTLS_SSL_PROC_CHK(mbedtls_ssl_start_handshake_msg( ssl, MBEDTLS_SSL_HS_SERVER_HELLO, &buf, &buf_len)); MBEDTLS_SSL_PROC_CHK(ssl_tls13_write_server_hello_body(ssl, buf, buf + buf_len, &msg_len, 1)); mbedtls_ssl_add_hs_msg_to_checksum( ssl, MBEDTLS_SSL_HS_SERVER_HELLO, buf, msg_len); MBEDTLS_SSL_PROC_CHK(mbedtls_ssl_finish_handshake_msg(ssl, buf_len, msg_len)); ssl->handshake->hello_retry_request_count++; #if defined(MBEDTLS_SSL_TLS1_3_COMPATIBILITY_MODE) /* The server sends a dummy change_cipher_spec record immediately * after its first handshake message. This may either be after * a ServerHello or a HelloRetryRequest. */ mbedtls_ssl_handshake_set_state( ssl, MBEDTLS_SSL_SERVER_CCS_AFTER_HELLO_RETRY_REQUEST); #else mbedtls_ssl_handshake_set_state(ssl, MBEDTLS_SSL_CLIENT_HELLO); #endif /* MBEDTLS_SSL_TLS1_3_COMPATIBILITY_MODE */ cleanup: MBEDTLS_SSL_DEBUG_MSG(2, ("<= write hello retry request")); return ret; } /* * Handler for MBEDTLS_SSL_ENCRYPTED_EXTENSIONS */ /* * struct { * Extension extensions<0..2 ^ 16 - 1>; * } EncryptedExtensions; * */ MBEDTLS_CHECK_RETURN_CRITICAL static int ssl_tls13_write_encrypted_extensions_body(mbedtls_ssl_context *ssl, unsigned char *buf, unsigned char *end, size_t *out_len) { int ret = MBEDTLS_ERR_ERROR_CORRUPTION_DETECTED; unsigned char *p = buf; size_t extensions_len = 0; unsigned char *p_extensions_len; size_t output_len; *out_len = 0; MBEDTLS_SSL_CHK_BUF_PTR(p, end, 2); p_extensions_len = p; p += 2; ((void) ssl); ((void) ret); ((void) output_len); #if defined(MBEDTLS_SSL_ALPN) ret = mbedtls_ssl_write_alpn_ext(ssl, p, end, &output_len); if (ret != 0) { return ret; } p += output_len; #endif /* MBEDTLS_SSL_ALPN */ extensions_len = (p - p_extensions_len) - 2; MBEDTLS_PUT_UINT16_BE(extensions_len, p_extensions_len, 0); *out_len = p - buf; MBEDTLS_SSL_DEBUG_BUF(4, "encrypted extensions", buf, *out_len); MBEDTLS_SSL_PRINT_EXTS( 3, MBEDTLS_SSL_HS_ENCRYPTED_EXTENSIONS, ssl->handshake->sent_extensions); return 0; } MBEDTLS_CHECK_RETURN_CRITICAL static int ssl_tls13_write_encrypted_extensions(mbedtls_ssl_context *ssl) { int ret = MBEDTLS_ERR_ERROR_CORRUPTION_DETECTED; unsigned char *buf; size_t buf_len, msg_len; mbedtls_ssl_set_outbound_transform(ssl, ssl->handshake->transform_handshake); MBEDTLS_SSL_DEBUG_MSG( 3, ("switching to handshake transform for outbound data")); MBEDTLS_SSL_DEBUG_MSG(2, ("=> write encrypted extensions")); MBEDTLS_SSL_PROC_CHK(mbedtls_ssl_start_handshake_msg(ssl, MBEDTLS_SSL_HS_ENCRYPTED_EXTENSIONS, &buf, &buf_len)); MBEDTLS_SSL_PROC_CHK(ssl_tls13_write_encrypted_extensions_body( ssl, buf, buf + buf_len, &msg_len)); mbedtls_ssl_add_hs_msg_to_checksum( ssl, MBEDTLS_SSL_HS_ENCRYPTED_EXTENSIONS, buf, msg_len); MBEDTLS_SSL_PROC_CHK(mbedtls_ssl_finish_handshake_msg( ssl, buf_len, msg_len)); #if defined(MBEDTLS_SSL_TLS1_3_KEY_EXCHANGE_MODE_EPHEMERAL_ENABLED) if (mbedtls_ssl_tls13_key_exchange_mode_with_psk(ssl)) { mbedtls_ssl_handshake_set_state(ssl, MBEDTLS_SSL_SERVER_FINISHED); } else { mbedtls_ssl_handshake_set_state(ssl, MBEDTLS_SSL_CERTIFICATE_REQUEST); } #else mbedtls_ssl_handshake_set_state(ssl, MBEDTLS_SSL_SERVER_FINISHED); #endif cleanup: MBEDTLS_SSL_DEBUG_MSG(2, ("<= write encrypted extensions")); return ret; } #if defined(MBEDTLS_SSL_TLS1_3_KEY_EXCHANGE_MODE_EPHEMERAL_ENABLED) #define SSL_CERTIFICATE_REQUEST_SEND_REQUEST 0 #define SSL_CERTIFICATE_REQUEST_SKIP 1 /* Coordination: * Check whether a CertificateRequest message should be written. * Returns a negative code on failure, or * - SSL_CERTIFICATE_REQUEST_SEND_REQUEST * - SSL_CERTIFICATE_REQUEST_SKIP * indicating if the writing of the CertificateRequest * should be skipped or not. */ MBEDTLS_CHECK_RETURN_CRITICAL static int ssl_tls13_certificate_request_coordinate(mbedtls_ssl_context *ssl) { int authmode; #if defined(MBEDTLS_SSL_SERVER_NAME_INDICATION) if (ssl->handshake->sni_authmode != MBEDTLS_SSL_VERIFY_UNSET) { authmode = ssl->handshake->sni_authmode; } else #endif authmode = ssl->conf->authmode; if (authmode == MBEDTLS_SSL_VERIFY_NONE) { ssl->session_negotiate->verify_result = MBEDTLS_X509_BADCERT_SKIP_VERIFY; return SSL_CERTIFICATE_REQUEST_SKIP; } ssl->handshake->certificate_request_sent = 1; return SSL_CERTIFICATE_REQUEST_SEND_REQUEST; } /* * struct { * opaque certificate_request_context<0..2^8-1>; * Extension extensions<2..2^16-1>; * } CertificateRequest; * */ MBEDTLS_CHECK_RETURN_CRITICAL static int ssl_tls13_write_certificate_request_body(mbedtls_ssl_context *ssl, unsigned char *buf, const unsigned char *end, size_t *out_len) { int ret = MBEDTLS_ERR_ERROR_CORRUPTION_DETECTED; unsigned char *p = buf; size_t output_len = 0; unsigned char *p_extensions_len; *out_len = 0; /* Check if we have enough space: * - certificate_request_context (1 byte) * - extensions length (2 bytes) */ MBEDTLS_SSL_CHK_BUF_PTR(p, end, 3); /* * Write certificate_request_context */ /* * We use a zero length context for the normal handshake * messages. For post-authentication handshake messages * this request context would be set to a non-zero value. */ *p++ = 0x0; /* * Write extensions */ /* The extensions must contain the signature_algorithms. */ p_extensions_len = p; p += 2; ret = mbedtls_ssl_write_sig_alg_ext(ssl, p, end, &output_len); if (ret != 0) { return ret; } p += output_len; MBEDTLS_PUT_UINT16_BE(p - p_extensions_len - 2, p_extensions_len, 0); *out_len = p - buf; MBEDTLS_SSL_PRINT_EXTS( 3, MBEDTLS_SSL_HS_CERTIFICATE_REQUEST, ssl->handshake->sent_extensions); return 0; } MBEDTLS_CHECK_RETURN_CRITICAL static int ssl_tls13_write_certificate_request(mbedtls_ssl_context *ssl) { int ret = MBEDTLS_ERR_ERROR_CORRUPTION_DETECTED; MBEDTLS_SSL_DEBUG_MSG(2, ("=> write certificate request")); MBEDTLS_SSL_PROC_CHK_NEG(ssl_tls13_certificate_request_coordinate(ssl)); if (ret == SSL_CERTIFICATE_REQUEST_SEND_REQUEST) { unsigned char *buf; size_t buf_len, msg_len; MBEDTLS_SSL_PROC_CHK(mbedtls_ssl_start_handshake_msg(ssl, MBEDTLS_SSL_HS_CERTIFICATE_REQUEST, &buf, &buf_len)); MBEDTLS_SSL_PROC_CHK(ssl_tls13_write_certificate_request_body( ssl, buf, buf + buf_len, &msg_len)); mbedtls_ssl_add_hs_msg_to_checksum( ssl, MBEDTLS_SSL_HS_CERTIFICATE_REQUEST, buf, msg_len); MBEDTLS_SSL_PROC_CHK(mbedtls_ssl_finish_handshake_msg( ssl, buf_len, msg_len)); } else if (ret == SSL_CERTIFICATE_REQUEST_SKIP) { MBEDTLS_SSL_DEBUG_MSG(2, ("<= skip write certificate request")); ret = 0; } else { MBEDTLS_SSL_DEBUG_MSG(1, ("should never happen")); ret = MBEDTLS_ERR_SSL_INTERNAL_ERROR; goto cleanup; } mbedtls_ssl_handshake_set_state(ssl, MBEDTLS_SSL_SERVER_CERTIFICATE); cleanup: MBEDTLS_SSL_DEBUG_MSG(2, ("<= write certificate request")); return ret; } /* * Handler for MBEDTLS_SSL_SERVER_CERTIFICATE */ MBEDTLS_CHECK_RETURN_CRITICAL static int ssl_tls13_write_server_certificate(mbedtls_ssl_context *ssl) { int ret = MBEDTLS_ERR_ERROR_CORRUPTION_DETECTED; #if defined(MBEDTLS_X509_CRT_PARSE_C) if ((ssl_tls13_pick_key_cert(ssl) != 0) || mbedtls_ssl_own_cert(ssl) == NULL) { MBEDTLS_SSL_DEBUG_MSG(2, ("No certificate available.")); MBEDTLS_SSL_PEND_FATAL_ALERT(MBEDTLS_SSL_ALERT_MSG_HANDSHAKE_FAILURE, MBEDTLS_ERR_SSL_HANDSHAKE_FAILURE); return MBEDTLS_ERR_SSL_HANDSHAKE_FAILURE; } #endif /* MBEDTLS_X509_CRT_PARSE_C */ ret = mbedtls_ssl_tls13_write_certificate(ssl); if (ret != 0) { return ret; } mbedtls_ssl_handshake_set_state(ssl, MBEDTLS_SSL_CERTIFICATE_VERIFY); return 0; } /* * Handler for MBEDTLS_SSL_CERTIFICATE_VERIFY */ MBEDTLS_CHECK_RETURN_CRITICAL static int ssl_tls13_write_certificate_verify(mbedtls_ssl_context *ssl) { int ret = mbedtls_ssl_tls13_write_certificate_verify(ssl); if (ret != 0) { return ret; } mbedtls_ssl_handshake_set_state(ssl, MBEDTLS_SSL_SERVER_FINISHED); return 0; } #endif /* MBEDTLS_SSL_TLS1_3_KEY_EXCHANGE_MODE_EPHEMERAL_ENABLED */ /* * Handler for MBEDTLS_SSL_SERVER_FINISHED */ MBEDTLS_CHECK_RETURN_CRITICAL static int ssl_tls13_write_server_finished(mbedtls_ssl_context *ssl) { int ret = MBEDTLS_ERR_ERROR_CORRUPTION_DETECTED; ret = mbedtls_ssl_tls13_write_finished_message(ssl); if (ret != 0) { return ret; } ret = mbedtls_ssl_tls13_compute_application_transform(ssl); if (ret != 0) { MBEDTLS_SSL_PEND_FATAL_ALERT( MBEDTLS_SSL_ALERT_MSG_HANDSHAKE_FAILURE, MBEDTLS_ERR_SSL_HANDSHAKE_FAILURE); return ret; } MBEDTLS_SSL_DEBUG_MSG(1, ("Switch to handshake keys for inbound traffic")); mbedtls_ssl_set_inbound_transform(ssl, ssl->handshake->transform_handshake); if (ssl->handshake->certificate_request_sent) { mbedtls_ssl_handshake_set_state(ssl, MBEDTLS_SSL_CLIENT_CERTIFICATE); } else { MBEDTLS_SSL_DEBUG_MSG(2, ("skip parse certificate")); MBEDTLS_SSL_DEBUG_MSG(2, ("skip parse certificate verify")); mbedtls_ssl_handshake_set_state(ssl, MBEDTLS_SSL_CLIENT_FINISHED); } return 0; } /* * Handler for MBEDTLS_SSL_CLIENT_FINISHED */ MBEDTLS_CHECK_RETURN_CRITICAL static int ssl_tls13_process_client_finished(mbedtls_ssl_context *ssl) { int ret = MBEDTLS_ERR_ERROR_CORRUPTION_DETECTED; ret = mbedtls_ssl_tls13_process_finished_message(ssl); if (ret != 0) { return ret; } ret = mbedtls_ssl_tls13_compute_resumption_master_secret(ssl); if (ret != 0) { MBEDTLS_SSL_DEBUG_RET(1, "mbedtls_ssl_tls13_compute_resumption_master_secret", ret); } mbedtls_ssl_handshake_set_state(ssl, MBEDTLS_SSL_HANDSHAKE_WRAPUP); return 0; } /* * Handler for MBEDTLS_SSL_HANDSHAKE_WRAPUP */ MBEDTLS_CHECK_RETURN_CRITICAL static int ssl_tls13_handshake_wrapup(mbedtls_ssl_context *ssl) { MBEDTLS_SSL_DEBUG_MSG(2, ("handshake: done")); mbedtls_ssl_tls13_handshake_wrapup(ssl); #if defined(MBEDTLS_SSL_SESSION_TICKETS) && \ defined(MBEDTLS_SSL_TLS1_3_KEY_EXCHANGE_MODE_SOME_PSK_ENABLED) /* TODO: Remove the check of SOME_PSK_ENABLED since SESSION_TICKETS requires * SOME_PSK_ENABLED to be enabled. Here is just to make CI happy. It is * expected to be resolved with issue#6395. */ /* Sent NewSessionTicket message only when client supports PSK */ if (mbedtls_ssl_tls13_some_psk_enabled(ssl)) { mbedtls_ssl_handshake_set_state(ssl, MBEDTLS_SSL_TLS1_3_NEW_SESSION_TICKET); } else #endif { mbedtls_ssl_handshake_set_state(ssl, MBEDTLS_SSL_HANDSHAKE_OVER); } return 0; } /* * Handler for MBEDTLS_SSL_TLS1_3_NEW_SESSION_TICKET */ #define SSL_NEW_SESSION_TICKET_SKIP 0 #define SSL_NEW_SESSION_TICKET_WRITE 1 MBEDTLS_CHECK_RETURN_CRITICAL static int ssl_tls13_write_new_session_ticket_coordinate(mbedtls_ssl_context *ssl) { /* Check whether the use of session tickets is enabled */ if (ssl->conf->f_ticket_write == NULL) { MBEDTLS_SSL_DEBUG_MSG(2, ("NewSessionTicket: disabled," " callback is not set")); return SSL_NEW_SESSION_TICKET_SKIP; } if (ssl->conf->new_session_tickets_count == 0) { MBEDTLS_SSL_DEBUG_MSG(2, ("NewSessionTicket: disabled," " configured count is zero")); return SSL_NEW_SESSION_TICKET_SKIP; } if (ssl->handshake->new_session_tickets_count == 0) { MBEDTLS_SSL_DEBUG_MSG(2, ("NewSessionTicket: all tickets have " "been sent.")); return SSL_NEW_SESSION_TICKET_SKIP; } return SSL_NEW_SESSION_TICKET_WRITE; } #if defined(MBEDTLS_SSL_SESSION_TICKETS) MBEDTLS_CHECK_RETURN_CRITICAL static int ssl_tls13_prepare_new_session_ticket(mbedtls_ssl_context *ssl, unsigned char *ticket_nonce, size_t ticket_nonce_size) { int ret = MBEDTLS_ERR_ERROR_CORRUPTION_DETECTED; mbedtls_ssl_session *session = ssl->session; mbedtls_ssl_ciphersuite_t *ciphersuite_info; psa_algorithm_t psa_hash_alg; int hash_length; MBEDTLS_SSL_DEBUG_MSG(2, ("=> prepare NewSessionTicket msg")); #if defined(MBEDTLS_HAVE_TIME) session->start = mbedtls_time(NULL); #endif /* Set ticket_flags depends on the advertised psk key exchange mode */ mbedtls_ssl_session_clear_ticket_flags( session, MBEDTLS_SSL_TLS1_3_TICKET_FLAGS_MASK); #if defined(MBEDTLS_SSL_TLS1_3_KEY_EXCHANGE_MODE_SOME_PSK_ENABLED) mbedtls_ssl_session_set_ticket_flags( session, ssl->handshake->tls13_kex_modes); #endif MBEDTLS_SSL_PRINT_TICKET_FLAGS(4, session->ticket_flags); /* Generate ticket_age_add */ if ((ret = ssl->conf->f_rng(ssl->conf->p_rng, (unsigned char *) &session->ticket_age_add, sizeof(session->ticket_age_add)) != 0)) { MBEDTLS_SSL_DEBUG_RET(1, "generate_ticket_age_add", ret); return ret; } MBEDTLS_SSL_DEBUG_MSG(3, ("ticket_age_add: %u", (unsigned int) session->ticket_age_add)); /* Generate ticket_nonce */ ret = ssl->conf->f_rng(ssl->conf->p_rng, ticket_nonce, ticket_nonce_size); if (ret != 0) { MBEDTLS_SSL_DEBUG_RET(1, "generate_ticket_nonce", ret); return ret; } MBEDTLS_SSL_DEBUG_BUF(3, "ticket_nonce:", ticket_nonce, ticket_nonce_size); ciphersuite_info = (mbedtls_ssl_ciphersuite_t *) ssl->handshake->ciphersuite_info; psa_hash_alg = mbedtls_psa_translate_md(ciphersuite_info->mac); hash_length = PSA_HASH_LENGTH(psa_hash_alg); if (hash_length == -1 || (size_t) hash_length > sizeof(session->resumption_key)) { return MBEDTLS_ERR_SSL_INTERNAL_ERROR; } /* In this code the psk key length equals the length of the hash */ session->resumption_key_len = hash_length; session->ciphersuite = ciphersuite_info->id; /* Compute resumption key * * HKDF-Expand-Label( resumption_master_secret, * "resumption", ticket_nonce, Hash.length ) */ ret = mbedtls_ssl_tls13_hkdf_expand_label( psa_hash_alg, session->app_secrets.resumption_master_secret, hash_length, MBEDTLS_SSL_TLS1_3_LBL_WITH_LEN(resumption), ticket_nonce, ticket_nonce_size, session->resumption_key, hash_length); if (ret != 0) { MBEDTLS_SSL_DEBUG_RET(2, "Creating the ticket-resumed PSK failed", ret); return ret; } MBEDTLS_SSL_DEBUG_BUF(3, "Ticket-resumed PSK", session->resumption_key, session->resumption_key_len); MBEDTLS_SSL_DEBUG_BUF(3, "resumption_master_secret", session->app_secrets.resumption_master_secret, hash_length); return 0; } /* This function creates a NewSessionTicket message in the following format: * * struct { * uint32 ticket_lifetime; * uint32 ticket_age_add; * opaque ticket_nonce<0..255>; * opaque ticket<1..2^16-1>; * Extension extensions<0..2^16-2>; * } NewSessionTicket; * * The ticket inside the NewSessionTicket message is an encrypted container * carrying the necessary information so that the server is later able to * re-start the communication. * * The following fields are placed inside the ticket by the * f_ticket_write() function: * * - creation time (start) * - flags (flags) * - age add (ticket_age_add) * - key (key) * - key length (key_len) * - ciphersuite (ciphersuite) */ MBEDTLS_CHECK_RETURN_CRITICAL static int ssl_tls13_write_new_session_ticket_body(mbedtls_ssl_context *ssl, unsigned char *buf, unsigned char *end, size_t *out_len, unsigned char *ticket_nonce, size_t ticket_nonce_size) { int ret = MBEDTLS_ERR_ERROR_CORRUPTION_DETECTED; unsigned char *p = buf; mbedtls_ssl_session *session = ssl->session; size_t ticket_len; uint32_t ticket_lifetime; *out_len = 0; MBEDTLS_SSL_DEBUG_MSG(2, ("=> write NewSessionTicket msg")); /* * ticket_lifetime 4 bytes * ticket_age_add 4 bytes * ticket_nonce 1 + ticket_nonce_size bytes * ticket >=2 bytes */ MBEDTLS_SSL_CHK_BUF_PTR(p, end, 4 + 4 + 1 + ticket_nonce_size + 2); /* Generate ticket and ticket_lifetime */ ret = ssl->conf->f_ticket_write(ssl->conf->p_ticket, session, p + 9 + ticket_nonce_size + 2, end, &ticket_len, &ticket_lifetime); if (ret != 0) { MBEDTLS_SSL_DEBUG_RET(1, "write_ticket", ret); return ret; } /* RFC 8446 4.6.1 * ticket_lifetime: Indicates the lifetime in seconds as a 32-bit * unsigned integer in network byte order from the time of ticket * issuance. Servers MUST NOT use any value greater than * 604800 seconds (7 days). The value of zero indicates that the * ticket should be discarded immediately. Clients MUST NOT cache * tickets for longer than 7 days, regardless of the ticket_lifetime, * and MAY delete tickets earlier based on local policy. A server * MAY treat a ticket as valid for a shorter period of time than what * is stated in the ticket_lifetime. */ if (ticket_lifetime > 604800) { ticket_lifetime = 604800; } MBEDTLS_PUT_UINT32_BE(ticket_lifetime, p, 0); MBEDTLS_SSL_DEBUG_MSG(3, ("ticket_lifetime: %u", (unsigned int) ticket_lifetime)); /* Write ticket_age_add */ MBEDTLS_PUT_UINT32_BE(session->ticket_age_add, p, 4); MBEDTLS_SSL_DEBUG_MSG(3, ("ticket_age_add: %u", (unsigned int) session->ticket_age_add)); /* Write ticket_nonce */ p[8] = (unsigned char) ticket_nonce_size; if (ticket_nonce_size > 0) { memcpy(p + 9, ticket_nonce, ticket_nonce_size); } p += 9 + ticket_nonce_size; /* Write ticket */ MBEDTLS_PUT_UINT16_BE(ticket_len, p, 0); p += 2; MBEDTLS_SSL_DEBUG_BUF(4, "ticket", p, ticket_len); p += ticket_len; /* Ticket Extensions * * Note: We currently don't have any extensions. * Set length to zero. */ ssl->handshake->sent_extensions = MBEDTLS_SSL_EXT_MASK_NONE; MBEDTLS_SSL_CHK_BUF_PTR(p, end, 2); MBEDTLS_PUT_UINT16_BE(0, p, 0); p += 2; *out_len = p - buf; MBEDTLS_SSL_DEBUG_BUF(4, "ticket", buf, *out_len); MBEDTLS_SSL_DEBUG_MSG(2, ("<= write new session ticket")); MBEDTLS_SSL_PRINT_EXTS( 3, MBEDTLS_SSL_HS_NEW_SESSION_TICKET, ssl->handshake->sent_extensions); return 0; } /* * Handler for MBEDTLS_SSL_TLS1_3_NEW_SESSION_TICKET */ static int ssl_tls13_write_new_session_ticket(mbedtls_ssl_context *ssl) { int ret = MBEDTLS_ERR_ERROR_CORRUPTION_DETECTED; MBEDTLS_SSL_PROC_CHK_NEG(ssl_tls13_write_new_session_ticket_coordinate(ssl)); if (ret == SSL_NEW_SESSION_TICKET_WRITE) { unsigned char ticket_nonce[MBEDTLS_SSL_TLS1_3_TICKET_NONCE_LENGTH]; unsigned char *buf; size_t buf_len, msg_len; MBEDTLS_SSL_PROC_CHK(ssl_tls13_prepare_new_session_ticket( ssl, ticket_nonce, sizeof(ticket_nonce))); MBEDTLS_SSL_PROC_CHK(mbedtls_ssl_start_handshake_msg(ssl, MBEDTLS_SSL_HS_NEW_SESSION_TICKET, &buf, &buf_len)); MBEDTLS_SSL_PROC_CHK(ssl_tls13_write_new_session_ticket_body( ssl, buf, buf + buf_len, &msg_len, ticket_nonce, sizeof(ticket_nonce))); MBEDTLS_SSL_PROC_CHK(mbedtls_ssl_finish_handshake_msg( ssl, buf_len, msg_len)); /* Limit session tickets count to one when resumption connection. * * See document of mbedtls_ssl_conf_new_session_tickets. */ if (ssl->handshake->resume == 1) { ssl->handshake->new_session_tickets_count = 0; } else { ssl->handshake->new_session_tickets_count--; } mbedtls_ssl_handshake_set_state( ssl, MBEDTLS_SSL_TLS1_3_NEW_SESSION_TICKET_FLUSH); } else { mbedtls_ssl_handshake_set_state(ssl, MBEDTLS_SSL_HANDSHAKE_OVER); } cleanup: return ret; } #endif /* MBEDTLS_SSL_SESSION_TICKETS */ /* * TLS 1.3 State Machine -- server side */ int mbedtls_ssl_tls13_handshake_server_step(mbedtls_ssl_context *ssl) { int ret = MBEDTLS_ERR_ERROR_CORRUPTION_DETECTED; if (ssl->state == MBEDTLS_SSL_HANDSHAKE_OVER || ssl->handshake == NULL) { return MBEDTLS_ERR_SSL_BAD_INPUT_DATA; } MBEDTLS_SSL_DEBUG_MSG(2, ("tls13 server state: %s(%d)", mbedtls_ssl_states_str(ssl->state), ssl->state)); switch (ssl->state) { /* start state */ case MBEDTLS_SSL_HELLO_REQUEST: mbedtls_ssl_handshake_set_state(ssl, MBEDTLS_SSL_CLIENT_HELLO); ret = 0; break; case MBEDTLS_SSL_CLIENT_HELLO: ret = ssl_tls13_process_client_hello(ssl); if (ret != 0) { MBEDTLS_SSL_DEBUG_RET(1, "ssl_tls13_process_client_hello", ret); } break; case MBEDTLS_SSL_HELLO_RETRY_REQUEST: ret = ssl_tls13_write_hello_retry_request(ssl); if (ret != 0) { MBEDTLS_SSL_DEBUG_RET(1, "ssl_tls13_write_hello_retry_request", ret); return ret; } break; case MBEDTLS_SSL_SERVER_HELLO: ret = ssl_tls13_write_server_hello(ssl); break; case MBEDTLS_SSL_ENCRYPTED_EXTENSIONS: ret = ssl_tls13_write_encrypted_extensions(ssl); if (ret != 0) { MBEDTLS_SSL_DEBUG_RET(1, "ssl_tls13_write_encrypted_extensions", ret); return ret; } break; #if defined(MBEDTLS_SSL_TLS1_3_KEY_EXCHANGE_MODE_EPHEMERAL_ENABLED) case MBEDTLS_SSL_CERTIFICATE_REQUEST: ret = ssl_tls13_write_certificate_request(ssl); break; case MBEDTLS_SSL_SERVER_CERTIFICATE: ret = ssl_tls13_write_server_certificate(ssl); break; case MBEDTLS_SSL_CERTIFICATE_VERIFY: ret = ssl_tls13_write_certificate_verify(ssl); break; #endif /* MBEDTLS_SSL_TLS1_3_KEY_EXCHANGE_MODE_EPHEMERAL_ENABLED */ /* * Injection of dummy-CCS's for middlebox compatibility */ #if defined(MBEDTLS_SSL_TLS1_3_COMPATIBILITY_MODE) case MBEDTLS_SSL_SERVER_CCS_AFTER_HELLO_RETRY_REQUEST: ret = mbedtls_ssl_tls13_write_change_cipher_spec(ssl); if (ret == 0) { mbedtls_ssl_handshake_set_state(ssl, MBEDTLS_SSL_CLIENT_HELLO); } break; case MBEDTLS_SSL_SERVER_CCS_AFTER_SERVER_HELLO: ret = mbedtls_ssl_tls13_write_change_cipher_spec(ssl); if (ret == 0) { mbedtls_ssl_handshake_set_state(ssl, MBEDTLS_SSL_ENCRYPTED_EXTENSIONS); } break; #endif /* MBEDTLS_SSL_TLS1_3_COMPATIBILITY_MODE */ case MBEDTLS_SSL_SERVER_FINISHED: ret = ssl_tls13_write_server_finished(ssl); break; case MBEDTLS_SSL_CLIENT_FINISHED: ret = ssl_tls13_process_client_finished(ssl); break; case MBEDTLS_SSL_HANDSHAKE_WRAPUP: ret = ssl_tls13_handshake_wrapup(ssl); break; #if defined(MBEDTLS_SSL_TLS1_3_KEY_EXCHANGE_MODE_EPHEMERAL_ENABLED) case MBEDTLS_SSL_CLIENT_CERTIFICATE: ret = mbedtls_ssl_tls13_process_certificate(ssl); if (ret == 0) { if (ssl->session_negotiate->peer_cert != NULL) { mbedtls_ssl_handshake_set_state( ssl, MBEDTLS_SSL_CLIENT_CERTIFICATE_VERIFY); } else { MBEDTLS_SSL_DEBUG_MSG(2, ("skip parse certificate verify")); mbedtls_ssl_handshake_set_state( ssl, MBEDTLS_SSL_CLIENT_FINISHED); } } break; case MBEDTLS_SSL_CLIENT_CERTIFICATE_VERIFY: ret = mbedtls_ssl_tls13_process_certificate_verify(ssl); if (ret == 0) { mbedtls_ssl_handshake_set_state( ssl, MBEDTLS_SSL_CLIENT_FINISHED); } break; #endif /* MBEDTLS_SSL_TLS1_3_KEY_EXCHANGE_MODE_EPHEMERAL_ENABLED */ #if defined(MBEDTLS_SSL_SESSION_TICKETS) case MBEDTLS_SSL_TLS1_3_NEW_SESSION_TICKET: ret = ssl_tls13_write_new_session_ticket(ssl); if (ret != 0) { MBEDTLS_SSL_DEBUG_RET(1, "ssl_tls13_write_new_session_ticket ", ret); } break; case MBEDTLS_SSL_TLS1_3_NEW_SESSION_TICKET_FLUSH: /* This state is necessary to do the flush of the New Session * Ticket message written in MBEDTLS_SSL_TLS1_3_NEW_SESSION_TICKET * as part of ssl_prepare_handshake_step. */ ret = 0; if (ssl->handshake->new_session_tickets_count == 0) { mbedtls_ssl_handshake_set_state(ssl, MBEDTLS_SSL_HANDSHAKE_OVER); } else { mbedtls_ssl_handshake_set_state(ssl, MBEDTLS_SSL_TLS1_3_NEW_SESSION_TICKET); } break; #endif /* MBEDTLS_SSL_SESSION_TICKETS */ default: MBEDTLS_SSL_DEBUG_MSG(1, ("invalid state %d", ssl->state)); return MBEDTLS_ERR_SSL_FEATURE_UNAVAILABLE; } return ret; } #endif /* MBEDTLS_SSL_SRV_C && MBEDTLS_SSL_PROTO_TLS1_3 */