- /* Copyright (c) 2016, Google Inc.
- *
- * Permission to use, copy, modify, and/or distribute this software for any
- * purpose with or without fee is hereby granted, provided that the above
- * copyright notice and this permission notice appear in all copies.
- *
- * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
- * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
- * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY
- * SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
- * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN ACTION
- * OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF OR IN
- * CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE. */
-
- #include <openssl/ssl.h>
-
- #include <assert.h>
- #include <string.h>
-
- #include <openssl/aead.h>
- #include <openssl/bytestring.h>
- #include <openssl/digest.h>
- #include <openssl/hmac.h>
- #include <openssl/hkdf.h>
- #include <openssl/mem.h>
-
- #include "internal.h"
-
-
- int tls13_init_key_schedule(SSL *ssl, const uint8_t *resumption_ctx,
- size_t resumption_ctx_len) {
- 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);
-
- /* Save the hash of the resumption context. */
- unsigned resumption_hash_len;
- if (!EVP_Digest(resumption_ctx, resumption_ctx_len, hs->resumption_hash,
- &resumption_hash_len, digest, NULL)) {
- return 0;
- }
-
- /* 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_hashes(SSL *ssl, uint8_t *out, size_t *out_len) {
- SSL_HANDSHAKE *hs = ssl->s3->hs;
-
- 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) {
- return 0;
- }
-
- memcpy(out + handshake_len, hs->resumption_hash, hs->hash_len);
- *out_len = handshake_len + hs->hash_len;
- return 1;
- }
-
- /* 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_hashes[2 * EVP_MAX_MD_SIZE];
- size_t context_hashes_len;
- if (!tls13_get_context_hashes(ssl, context_hashes, &context_hashes_len)) {
- return 0;
- }
-
- return hkdf_expand_label(out, digest, hs->secret, hs->hash_len, label,
- label_len, context_hashes, context_hashes_len, len);
- }
-
- int tls13_set_traffic_key(SSL *ssl, enum tls_record_type_t type,
- 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;
- }
-
- const char *phase;
- switch (type) {
- case type_early_handshake:
- phase = "early handshake key expansion, ";
- break;
- case type_early_data:
- phase = "early application data key expansion, ";
- break;
- case type_handshake:
- phase = "handshake key expansion, ";
- break;
- case type_data:
- phase = "application data key expansion, ";
- break;
- default:
- return 0;
- }
- size_t phase_len = strlen(phase);
-
- const char *purpose = "client write key";
- if ((ssl->server && direction == evp_aead_seal) ||
- (!ssl->server && direction == evp_aead_open)) {
- purpose = "server write key";
- }
- size_t purpose_len = strlen(purpose);
-
- /* The longest label has length 38 (type_early_data) + 16 (either purpose
- * value). */
- uint8_t label[38 + 16];
- size_t label_len = phase_len + purpose_len;
- if (label_len > sizeof(label)) {
- assert(0);
- return 0;
- }
- memcpy(label, phase, phase_len);
- memcpy(label + phase_len, purpose, purpose_len);
-
- /* Look up cipher suite properties. */
- const EVP_AEAD *aead;
- const EVP_MD *digest = ssl_get_handshake_digest(ssl_get_algorithm_prf(ssl));
- size_t mac_secret_len, fixed_iv_len;
- if (!ssl_cipher_get_evp_aead(&aead, &mac_secret_len, &fixed_iv_len,
- 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, label,
- label_len, NULL, 0, key_len)) {
- return 0;
- }
-
- /* The IV's label ends in "iv" instead of "key". */
- if (label_len < 3) {
- assert(0);
- return 0;
- }
- label_len--;
- label[label_len - 2] = 'i';
- label[label_len - 1] = 'v';
-
- /* 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, label,
- label_len, 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 kTLS13LabelHandshakeTraffic[] = "handshake traffic secret";
- static const char kTLS13LabelApplicationTraffic[] =
- "application traffic secret";
-
- int tls13_set_handshake_traffic(SSL *ssl) {
- SSL_HANDSHAKE *hs = ssl->s3->hs;
-
- uint8_t traffic_secret[EVP_MAX_MD_SIZE];
- if (!derive_secret(ssl, traffic_secret, hs->hash_len,
- (const uint8_t *)kTLS13LabelHandshakeTraffic,
- strlen(kTLS13LabelHandshakeTraffic)) ||
- !ssl_log_secret(ssl, "HANDSHAKE_TRAFFIC_SECRET", traffic_secret,
- hs->hash_len) ||
- !tls13_set_traffic_key(ssl, type_handshake, evp_aead_open, traffic_secret,
- hs->hash_len) ||
- !tls13_set_traffic_key(ssl, type_handshake, evp_aead_seal, traffic_secret,
- hs->hash_len)) {
- return 0;
- }
- return 1;
- }
-
- int tls13_derive_traffic_secret_0(SSL *ssl) {
- SSL_HANDSHAKE *hs = ssl->s3->hs;
-
- return derive_secret(ssl, hs->traffic_secret_0, hs->hash_len,
- (const uint8_t *)kTLS13LabelApplicationTraffic,
- strlen(kTLS13LabelApplicationTraffic)) &&
- ssl_log_secret(ssl, "TRAFFIC_SECRET_0", hs->traffic_secret_0,
- hs->hash_len);
- }
-
- 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, type_data, direction, secret, secret_len);
- }
-
- static const char kTLS13LabelExporter[] = "exporter master secret";
- static const char kTLS13LabelResumption[] = "resumption master secret";
-
- int tls13_finalize_keys(SSL *ssl) {
- SSL_HANDSHAKE *hs = ssl->s3->hs;
-
- ssl->s3->exporter_secret_len = hs->hash_len;
- ssl->s3->new_session->master_key_length = hs->hash_len;
- if (!derive_secret(
- ssl, ssl->s3->exporter_secret, ssl->s3->exporter_secret_len,
- (const uint8_t *)kTLS13LabelExporter, strlen(kTLS13LabelExporter)) ||
- !derive_secret(ssl, ssl->s3->new_session->master_key,
- ssl->s3->new_session->master_key_length,
- (const uint8_t *)kTLS13LabelResumption,
- strlen(kTLS13LabelResumption))) {
- return 0;
- }
-
- 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));
-
- uint8_t key[EVP_MAX_MD_SIZE];
- size_t key_len = EVP_MD_size(digest);
-
- const uint8_t *traffic_secret;
- const char *label;
- if (is_server) {
- label = "server finished";
- if (ssl->server) {
- traffic_secret = ssl->s3->write_traffic_secret;
- } else {
- traffic_secret = ssl->s3->read_traffic_secret;
- }
- } else {
- label = "client finished";
- if (!ssl->server) {
- traffic_secret = ssl->s3->write_traffic_secret;
- } else {
- traffic_secret = ssl->s3->read_traffic_secret;
- }
- }
-
- uint8_t context_hashes[2 * EVP_MAX_MD_SIZE];
- size_t context_hashes_len;
- unsigned len;
- if (!hkdf_expand_label(key, digest, traffic_secret, hs->hash_len,
- (const uint8_t *)label, strlen(label), NULL, 0,
- hs->hash_len) ||
- !tls13_get_context_hashes(ssl, context_hashes, &context_hashes_len) ||
- HMAC(digest, key, key_len, context_hashes, context_hashes_len, out,
- &len) == NULL) {
- return 0;
- }
- *out_len = len;
- return 1;
- }
-
- static const char kTLS13LabelResumptionPSK[] = "resumption psk";
- static const char kTLS13LabelResumptionContext[] = "resumption context";
-
- int tls13_resumption_psk(SSL *ssl, uint8_t *out, size_t out_len,
- const SSL_SESSION *session) {
- const EVP_MD *digest = ssl_get_handshake_digest(ssl_get_algorithm_prf(ssl));
- return hkdf_expand_label(out, digest, session->master_key,
- session->master_key_length,
- (const uint8_t *)kTLS13LabelResumptionPSK,
- strlen(kTLS13LabelResumptionPSK), NULL, 0, out_len);
- }
-
- int tls13_resumption_context(SSL *ssl, uint8_t *out, size_t out_len,
- const SSL_SESSION *session) {
- const EVP_MD *digest = ssl_get_handshake_digest(ssl_get_algorithm_prf(ssl));
- return hkdf_expand_label(out, digest, session->master_key,
- session->master_key_length,
- (const uint8_t *)kTLS13LabelResumptionContext,
- strlen(kTLS13LabelResumptionContext), NULL, 0,
- out_len);
- }
-
- 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);
- }
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