/* 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 #include #include #include #include #include #include #include #include #include "internal.h" int tls13_init_key_schedule(SSL *ssl) { SSL_HANDSHAKE *hs = ssl->s3->hs; const EVP_MD *digest = ssl_get_handshake_digest(ssl_get_algorithm_prf(ssl)); hs->hash_len = EVP_MD_size(digest); /* Initialize the secret to the zero key. */ memset(hs->secret, 0, hs->hash_len); /* Initialize the rolling hashes and release the handshake buffer. */ if (!ssl3_init_handshake_hash(ssl)) { return 0; } ssl3_free_handshake_buffer(ssl); return 1; } int tls13_advance_key_schedule(SSL *ssl, const uint8_t *in, size_t len) { SSL_HANDSHAKE *hs = ssl->s3->hs; const EVP_MD *digest = ssl_get_handshake_digest(ssl_get_algorithm_prf(ssl)); return HKDF_extract(hs->secret, &hs->hash_len, digest, in, 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 uint8_t *label, size_t label_len, const uint8_t *hash, size_t hash_len, size_t len) { static const char kTLS13LabelVersion[] = "TLS 1.3, "; CBB cbb, child; uint8_t *hkdf_label; size_t hkdf_label_len; if (!CBB_init(&cbb, 2 + 1 + strlen(kTLS13LabelVersion) + label_len + 1 + hash_len) || !CBB_add_u16(&cbb, len) || !CBB_add_u8_length_prefixed(&cbb, &child) || !CBB_add_bytes(&child, (const uint8_t *)kTLS13LabelVersion, strlen(kTLS13LabelVersion)) || !CBB_add_bytes(&child, label, label_len) || !CBB_add_u8_length_prefixed(&cbb, &child) || !CBB_add_bytes(&child, hash, hash_len) || !CBB_finish(&cbb, &hkdf_label, &hkdf_label_len)) { CBB_cleanup(&cbb); return 0; } int ret = HKDF_expand(out, len, digest, secret, secret_len, hkdf_label, hkdf_label_len); OPENSSL_free(hkdf_label); return ret; } int tls13_get_context_hash(SSL *ssl, uint8_t *out, size_t *out_len) { EVP_MD_CTX ctx; EVP_MD_CTX_init(&ctx); unsigned handshake_len = 0; int ok = EVP_MD_CTX_copy_ex(&ctx, &ssl->s3->handshake_hash) && EVP_DigestFinal_ex(&ctx, out, &handshake_len); EVP_MD_CTX_cleanup(&ctx); if (ok) { *out_len = handshake_len; } return ok; } /* 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 *ssl, uint8_t *out, size_t len, const uint8_t *label, size_t label_len) { SSL_HANDSHAKE *hs = ssl->s3->hs; const EVP_MD *digest = ssl_get_handshake_digest(ssl_get_algorithm_prf(ssl)); uint8_t context_hash[EVP_MAX_MD_SIZE]; size_t context_hash_len; if (!tls13_get_context_hash(ssl, context_hash, &context_hash_len)) { return 0; } return hkdf_expand_label(out, 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) { if (traffic_secret_len > 0xff) { OPENSSL_PUT_ERROR(SSL, ERR_R_OVERFLOW); return 0; } /* Look up cipher suite properties. */ const EVP_AEAD *aead; const EVP_MD *digest = ssl_get_handshake_digest(ssl_get_algorithm_prf(ssl)); size_t discard; if (!ssl_cipher_get_evp_aead(&aead, &discard, &discard, SSL_get_session(ssl)->cipher, ssl3_protocol_version(ssl))) { return 0; } /* 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, (const uint8_t *)"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, (const uint8_t *)"iv", 2, NULL, 0, iv_len)) { return 0; } SSL_AEAD_CTX *traffic_aead = SSL_AEAD_CTX_new( direction, ssl3_protocol_version(ssl), SSL_get_session(ssl)->cipher, key, key_len, NULL, 0, iv, iv_len); if (traffic_aead == NULL) { return 0; } if (direction == evp_aead_open) { if (!ssl->method->set_read_state(ssl, traffic_aead)) { return 0; } } else { if (!ssl->method->set_write_state(ssl, traffic_aead)) { return 0; } } /* Save the traffic secret. */ if (direction == evp_aead_open) { memmove(ssl->s3->read_traffic_secret, traffic_secret, traffic_secret_len); ssl->s3->read_traffic_secret_len = traffic_secret_len; } else { 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 kTLS13LabelClientHandshakeTraffic[] = "client handshake traffic secret"; static const char kTLS13LabelServerHandshakeTraffic[] = "server handshake traffic secret"; static const char kTLS13LabelClientApplicationTraffic[] = "client application traffic secret"; static const char kTLS13LabelServerApplicationTraffic[] = "server application traffic secret"; int tls13_set_handshake_traffic(SSL *ssl) { SSL_HANDSHAKE *hs = ssl->s3->hs; uint8_t client_traffic_secret[EVP_MAX_MD_SIZE]; uint8_t server_traffic_secret[EVP_MAX_MD_SIZE]; if (!derive_secret(ssl, client_traffic_secret, hs->hash_len, (const uint8_t *)kTLS13LabelClientHandshakeTraffic, strlen(kTLS13LabelClientHandshakeTraffic)) || !ssl_log_secret(ssl, "CLIENT_HANDSHAKE_TRAFFIC_SECRET", client_traffic_secret, hs->hash_len) || !derive_secret(ssl, server_traffic_secret, hs->hash_len, (const uint8_t *)kTLS13LabelServerHandshakeTraffic, strlen(kTLS13LabelServerHandshakeTraffic)) || !ssl_log_secret(ssl, "SERVER_HANDSHAKE_TRAFFIC_SECRET", server_traffic_secret, hs->hash_len)) { return 0; } if (ssl->server) { if (!tls13_set_traffic_key(ssl, evp_aead_open, client_traffic_secret, hs->hash_len) || !tls13_set_traffic_key(ssl, evp_aead_seal, server_traffic_secret, hs->hash_len)) { return 0; } } else { if (!tls13_set_traffic_key(ssl, evp_aead_open, server_traffic_secret, hs->hash_len) || !tls13_set_traffic_key(ssl, evp_aead_seal, client_traffic_secret, hs->hash_len)) { return 0; } } return 1; } static const char kTLS13LabelExporter[] = "exporter master secret"; int tls13_derive_application_secrets(SSL *ssl) { SSL_HANDSHAKE *hs = ssl->s3->hs; ssl->s3->exporter_secret_len = hs->hash_len; return derive_secret(ssl, hs->client_traffic_secret_0, hs->hash_len, (const uint8_t *)kTLS13LabelClientApplicationTraffic, strlen(kTLS13LabelClientApplicationTraffic)) && ssl_log_secret(ssl, "CLIENT_TRAFFIC_SECRET_0", hs->client_traffic_secret_0, hs->hash_len) && derive_secret(ssl, hs->server_traffic_secret_0, hs->hash_len, (const uint8_t *)kTLS13LabelServerApplicationTraffic, strlen(kTLS13LabelServerApplicationTraffic)) && ssl_log_secret(ssl, "SERVER_TRAFFIC_SECRET_0", hs->server_traffic_secret_0, hs->hash_len) && derive_secret(ssl, ssl->s3->exporter_secret, hs->hash_len, (const uint8_t *)kTLS13LabelExporter, strlen(kTLS13LabelExporter)); } static const char kTLS13LabelApplicationTraffic[] = "application traffic secret"; int tls13_rotate_traffic_key(SSL *ssl, enum evp_aead_direction_t direction) { const EVP_MD *digest = ssl_get_handshake_digest(ssl_get_algorithm_prf(ssl)); 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; } if (!hkdf_expand_label(secret, digest, secret, secret_len, (const uint8_t *)kTLS13LabelApplicationTraffic, strlen(kTLS13LabelApplicationTraffic), NULL, 0, secret_len)) { return 0; } return tls13_set_traffic_key(ssl, direction, secret, secret_len); } static const char kTLS13LabelResumption[] = "resumption master secret"; int tls13_derive_resumption_secret(SSL *ssl) { if (ssl->s3->hs->hash_len > SSL_MAX_MASTER_KEY_LENGTH) { OPENSSL_PUT_ERROR(SSL, ERR_R_INTERNAL_ERROR); return 0; } ssl->s3->new_session->master_key_length = ssl->s3->hs->hash_len; return derive_secret(ssl, ssl->s3->new_session->master_key, ssl->s3->new_session->master_key_length, (const uint8_t *)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, 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, (const uint8_t *)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 *ssl, uint8_t *out, size_t *out_len, int is_server) { SSL_HANDSHAKE *hs = ssl->s3->hs; const EVP_MD *digest = ssl_get_handshake_digest(ssl_get_algorithm_prf(ssl)); const uint8_t *traffic_secret; if (is_server == ssl->server) { traffic_secret = ssl->s3->write_traffic_secret; } else { traffic_secret = ssl->s3->read_traffic_secret; } uint8_t context_hash[EVP_MAX_MD_SIZE]; size_t context_hash_len; if (!tls13_get_context_hash(ssl, context_hash, &context_hash_len) || !tls13_verify_data(digest, out, out_len, traffic_secret, hs->hash_len, context_hash, context_hash_len)) { return 0; } return 1; } int tls13_export_keying_material(SSL *ssl, uint8_t *out, size_t out_len, const char *label, size_t label_len, const uint8_t *context, size_t context_len, int use_context) { const EVP_MD *digest = ssl_get_handshake_digest(ssl_get_algorithm_prf(ssl)); const uint8_t *hash = NULL; size_t hash_len = 0; if (use_context) { hash = context; hash_len = context_len; } return hkdf_expand_label(out, digest, ssl->s3->exporter_secret, ssl->s3->exporter_secret_len, (const uint8_t *)label, label_len, hash, hash_len, out_len); } static const char kTLS13LabelPSKBinder[] = "resumption psk binder key"; static int tls13_psk_binder(SSL *ssl, uint8_t *out, 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, (const uint8_t *)kTLS13LabelPSKBinder, strlen(kTLS13LabelPSKBinder), binder_context, binder_context_len, hash_len) || !tls13_verify_data(digest, out, &len, binder_key, hash_len, context, context_len)) { return 0; } return 1; } int tls13_write_psk_binder(SSL *ssl, uint8_t *msg, size_t len) { const EVP_MD *digest = ssl_get_handshake_digest(ssl->session->cipher->algorithm_prf); size_t hash_len = EVP_MD_size(digest); if (len < hash_len + 3) { OPENSSL_PUT_ERROR(SSL, ERR_R_INTERNAL_ERROR); return 0; } EVP_MD_CTX ctx; EVP_MD_CTX_init(&ctx); uint8_t context[EVP_MAX_MD_SIZE]; unsigned context_len; if (!EVP_DigestInit_ex(&ctx, digest, NULL) || !EVP_DigestUpdate(&ctx, ssl->s3->handshake_buffer->data, ssl->s3->handshake_buffer->length) || !EVP_DigestUpdate(&ctx, msg, len - hash_len - 3) || !EVP_DigestFinal_ex(&ctx, context, &context_len)) { EVP_MD_CTX_cleanup(&ctx); return 0; } EVP_MD_CTX_cleanup(&ctx); uint8_t verify_data[EVP_MAX_MD_SIZE] = {0}; if (!tls13_psk_binder(ssl, verify_data, digest, ssl->session->master_key, ssl->session->master_key_length, context, context_len, hash_len)) { return 0; } memcpy(msg + len - hash_len, verify_data, hash_len); return 1; } int tls13_verify_psk_binder(SSL *ssl, SSL_SESSION *session, CBS *binders) { const EVP_MD *digest = ssl_get_handshake_digest(session->cipher->algorithm_prf); size_t hash_len = EVP_MD_size(digest); /* Get the full ClientHello, including message header. It must be large enough * to exclude the binders. */ CBS message; ssl->method->get_current_message(ssl, &message); if (CBS_len(&message) < CBS_len(binders) + 2) { OPENSSL_PUT_ERROR(SSL, ERR_R_INTERNAL_ERROR); return 0; } /* Hash a ClientHello prefix up to the binders. 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(&message), CBS_len(&message) - CBS_len(binders) - 2, context, &context_len, digest, NULL)) { return 0; } uint8_t verify_data[EVP_MAX_MD_SIZE] = {0}; CBS binder; if (!tls13_psk_binder(ssl, verify_data, 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; }