ssl/tls13_enc.c - boringssl - Git at Google

 /* 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/hkdf.h>
 #include <openssl/hmac.h>
 #include <openssl/mem.h>

 #include "../crypto/internal.h"
 #include "internal.h"


 int tls13_init_key_schedule(SSL_HANDSHAKE *hs) {
   SSL *const ssl = hs->ssl;
   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. */
   OPENSSL_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_HANDSHAKE *hs, const uint8_t *in,
                                size_t len) {
   const EVP_MD *digest =
       ssl_get_handshake_digest(ssl_get_algorithm_prf(hs->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_HANDSHAKE *hs, uint8_t *out, size_t len,
                          const uint8_t *label, size_t label_len) {
   SSL *const ssl = hs->ssl;
   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) {
     OPENSSL_memmove(ssl->s3->read_traffic_secret, traffic_secret,
                     traffic_secret_len);
     ssl->s3->read_traffic_secret_len = traffic_secret_len;
   } else {
     OPENSSL_memmove(ssl->s3->write_traffic_secret, traffic_secret,
                     traffic_secret_len);
     ssl->s3->write_traffic_secret_len = traffic_secret_len;
   }

   return 1;
 }

 static const char 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_derive_handshake_secrets(SSL_HANDSHAKE *hs) {
   SSL *const ssl = hs->ssl;
   return derive_secret(hs, hs->client_handshake_secret, hs->hash_len,
                        (const uint8_t *)kTLS13LabelClientHandshakeTraffic,
                        strlen(kTLS13LabelClientHandshakeTraffic)) &&
          ssl_log_secret(ssl, "CLIENT_HANDSHAKE_TRAFFIC_SECRET",
                         hs->client_handshake_secret, hs->hash_len) &&
          derive_secret(hs, hs->server_handshake_secret, hs->hash_len,
                        (const uint8_t *)kTLS13LabelServerHandshakeTraffic,
                        strlen(kTLS13LabelServerHandshakeTraffic)) &&
          ssl_log_secret(ssl, "SERVER_HANDSHAKE_TRAFFIC_SECRET",
                         hs->server_handshake_secret, hs->hash_len);
 }

 static const char kTLS13LabelExporter[] = "exporter master secret";

 int tls13_derive_application_secrets(SSL_HANDSHAKE *hs) {
   SSL *const ssl = hs->ssl;
   ssl->s3->exporter_secret_len = hs->hash_len;
   return derive_secret(hs, hs->client_traffic_secret_0, hs->hash_len,
                        (const uint8_t *)kTLS13LabelClientApplicationTraffic,
                        strlen(kTLS13LabelClientApplicationTraffic)) &&
          ssl_log_secret(ssl, "CLIENT_TRAFFIC_SECRET_0",
                         hs->client_traffic_secret_0, hs->hash_len) &&
          derive_secret(hs, hs->server_traffic_secret_0, hs->hash_len,
                        (const uint8_t *)kTLS13LabelServerApplicationTraffic,
                        strlen(kTLS13LabelServerApplicationTraffic)) &&
          ssl_log_secret(ssl, "SERVER_TRAFFIC_SECRET_0",
                         hs->server_traffic_secret_0, hs->hash_len) &&
          derive_secret(hs, ssl->s3->exporter_secret, hs->hash_len,
                        (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_HANDSHAKE *hs) {
   SSL *const ssl = hs->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 = hs->hash_len;
   return derive_secret(hs, 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_HANDSHAKE *hs, uint8_t *out, size_t *out_len,
                        int is_server) {
   SSL *const ssl = hs->ssl;
   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;
   }

   OPENSSL_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;
 }
	/* 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/hkdf.h>
	#include <openssl/hmac.h>
	#include <openssl/mem.h>

	#include "../crypto/internal.h"
	#include "internal.h"


	int tls13_init_key_schedule(SSL_HANDSHAKE *hs) {
	SSL *const ssl = hs->ssl;
	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. */
	OPENSSL_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_HANDSHAKE hs, const uint8_t in,
	size_t len) {
	const EVP_MD *digest =
	ssl_get_handshake_digest(ssl_get_algorithm_prf(hs->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_HANDSHAKE hs, uint8_t out, size_t len,
	const uint8_t *label, size_t label_len) {
	SSL *const ssl = hs->ssl;
	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) {
	OPENSSL_memmove(ssl->s3->read_traffic_secret, traffic_secret,
	traffic_secret_len);
	ssl->s3->read_traffic_secret_len = traffic_secret_len;
	} else {
	OPENSSL_memmove(ssl->s3->write_traffic_secret, traffic_secret,
	traffic_secret_len);
	ssl->s3->write_traffic_secret_len = traffic_secret_len;
	}

	return 1;
	}

	static const char 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_derive_handshake_secrets(SSL_HANDSHAKE *hs) {
	SSL *const ssl = hs->ssl;
	return derive_secret(hs, hs->client_handshake_secret, hs->hash_len,
	(const uint8_t *)kTLS13LabelClientHandshakeTraffic,
	strlen(kTLS13LabelClientHandshakeTraffic)) &&
	ssl_log_secret(ssl, "CLIENT_HANDSHAKE_TRAFFIC_SECRET",
	hs->client_handshake_secret, hs->hash_len) &&
	derive_secret(hs, hs->server_handshake_secret, hs->hash_len,
	(const uint8_t *)kTLS13LabelServerHandshakeTraffic,
	strlen(kTLS13LabelServerHandshakeTraffic)) &&
	ssl_log_secret(ssl, "SERVER_HANDSHAKE_TRAFFIC_SECRET",
	hs->server_handshake_secret, hs->hash_len);
	}

	static const char kTLS13LabelExporter[] = "exporter master secret";

	int tls13_derive_application_secrets(SSL_HANDSHAKE *hs) {
	SSL *const ssl = hs->ssl;
	ssl->s3->exporter_secret_len = hs->hash_len;
	return derive_secret(hs, hs->client_traffic_secret_0, hs->hash_len,
	(const uint8_t *)kTLS13LabelClientApplicationTraffic,
	strlen(kTLS13LabelClientApplicationTraffic)) &&
	ssl_log_secret(ssl, "CLIENT_TRAFFIC_SECRET_0",
	hs->client_traffic_secret_0, hs->hash_len) &&
	derive_secret(hs, hs->server_traffic_secret_0, hs->hash_len,
	(const uint8_t *)kTLS13LabelServerApplicationTraffic,
	strlen(kTLS13LabelServerApplicationTraffic)) &&
	ssl_log_secret(ssl, "SERVER_TRAFFIC_SECRET_0",
	hs->server_traffic_secret_0, hs->hash_len) &&
	derive_secret(hs, ssl->s3->exporter_secret, hs->hash_len,
	(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_HANDSHAKE *hs) {
	SSL *const ssl = hs->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 = hs->hash_len;
	return derive_secret(hs, 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_HANDSHAKE hs, uint8_t out, size_t *out_len,
	int is_server) {
	SSL *const ssl = hs->ssl;
	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;
	}

	OPENSSL_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;
	}