ssl/tls13_enc.c

   1 /*
   2  * Copyright 2016 The OpenSSL Project Authors. All Rights Reserved.
   3  *
   4  * Licensed under the OpenSSL license (the "License").  You may not use
   5  * this file except in compliance with the License.  You can obtain a copy
   6  * in the file LICENSE in the source distribution or at
   7  * https://www.openssl.org/source/license.html
   8  */
   9
  10 #include <stdlib.h>
  11 #include "ssl_locl.h"
  12 #include <openssl/evp.h>
  13 #include <openssl/kdf.h>
  14
  15 #define TLS13_MAX_LABEL_LEN     246
  16
  17 /* Always filled with zeros */
  18 static const unsigned char default_zeros[EVP_MAX_MD_SIZE];
  19
  20 /*
  21  * Given a |secret|; a |label| of length |labellen|; and a |hash| of the
  22  * handshake messages, derive a new secret |outlen| bytes long and store it in
  23  * the location pointed to be |out|. The |hash| value may be NULL. Returns 1 on
  24  * success  0 on failure.
  25  */
  26 int tls13_hkdf_expand(SSL *s, const EVP_MD *md, const unsigned char *secret,
  27                              const unsigned char *label, size_t labellen,
  28                              const unsigned char *hash,
  29                              unsigned char *out, size_t outlen)
  30 {
  31     const unsigned char label_prefix[] = "tls13 ";
  32     EVP_PKEY_CTX *pctx = EVP_PKEY_CTX_new_id(EVP_PKEY_HKDF, NULL);
  33     int ret;
  34     size_t hkdflabellen;
  35     size_t hashlen;
  36     /*
  37      * 2 bytes for length of whole HkdfLabel + 1 byte for length of combined
  38      * prefix and label + bytes for the label itself + bytes for the hash
  39      */
  40     unsigned char hkdflabel[sizeof(uint16_t) + sizeof(uint8_t) +
  41                             + sizeof(label_prefix) + TLS13_MAX_LABEL_LEN
  42                             + EVP_MAX_MD_SIZE];
  43     WPACKET pkt;
  44
  45     if (pctx == NULL)
  46         return 0;
  47
  48     hashlen = EVP_MD_size(md);
  49
  50     if (!WPACKET_init_static_len(&pkt, hkdflabel, sizeof(hkdflabel), 0)
  51             || !WPACKET_put_bytes_u16(&pkt, outlen)
  52             || !WPACKET_start_sub_packet_u8(&pkt)
  53             || !WPACKET_memcpy(&pkt, label_prefix, sizeof(label_prefix) - 1)
  54             || !WPACKET_memcpy(&pkt, label, labellen)
  55             || !WPACKET_close(&pkt)
  56             || !WPACKET_sub_memcpy_u8(&pkt, hash, (hash == NULL) ? 0 : hashlen)
  57             || !WPACKET_get_total_written(&pkt, &hkdflabellen)
  58             || !WPACKET_finish(&pkt)) {
  59         EVP_PKEY_CTX_free(pctx);
  60         WPACKET_cleanup(&pkt);
  61         return 0;
  62     }
  63
  64     ret = EVP_PKEY_derive_init(pctx) <= 0
  65             || EVP_PKEY_CTX_hkdf_mode(pctx, EVP_PKEY_HKDEF_MODE_EXPAND_ONLY)
  66                <= 0
  67             || EVP_PKEY_CTX_set_hkdf_md(pctx, md) <= 0
  68             || EVP_PKEY_CTX_set1_hkdf_key(pctx, secret, hashlen) <= 0
  69             || EVP_PKEY_CTX_add1_hkdf_info(pctx, hkdflabel, hkdflabellen) <= 0
  70             || EVP_PKEY_derive(pctx, out, &outlen) <= 0;
  71
  72     EVP_PKEY_CTX_free(pctx);
  73
  74     return ret == 0;
  75 }
  76
  77 /*
  78  * Given a |secret| generate a |key| of length |keylen| bytes. Returns 1 on
  79  * success  0 on failure.
  80  */
  81 int tls13_derive_key(SSL *s, const EVP_MD *md, const unsigned char *secret,
  82                      unsigned char *key, size_t keylen)
  83 {
  84     static const unsigned char keylabel[] = "key";
  85
  86     return tls13_hkdf_expand(s, md, secret, keylabel, sizeof(keylabel) - 1,
  87                              NULL, key, keylen);
  88 }
  89
  90 /*
  91  * Given a |secret| generate an |iv| of length |ivlen| bytes. Returns 1 on
  92  * success  0 on failure.
  93  */
  94 int tls13_derive_iv(SSL *s, const EVP_MD *md, const unsigned char *secret,
  95                     unsigned char *iv, size_t ivlen)
  96 {
  97     static const unsigned char ivlabel[] = "iv";
  98
  99     return tls13_hkdf_expand(s, md, secret, ivlabel, sizeof(ivlabel) - 1,
 100                              NULL, iv, ivlen);
 101 }
 102
 103 int tls13_derive_finishedkey(SSL *s, const EVP_MD *md,
 104                              const unsigned char *secret,
 105                              unsigned char *fin, size_t finlen)
 106 {
 107     static const unsigned char finishedlabel[] = "finished";
 108
 109     return tls13_hkdf_expand(s, md, secret, finishedlabel,
 110                              sizeof(finishedlabel) - 1, NULL, fin, finlen);
 111 }
 112
 113 /*
 114  * Given the previous secret |prevsecret| and a new input secret |insecret| of
 115  * length |insecretlen|, generate a new secret and store it in the location
 116  * pointed to by |outsecret|. Returns 1 on success  0 on failure.
 117  */
 118 int tls13_generate_secret(SSL *s, const EVP_MD *md,
 119                           const unsigned char *prevsecret,
 120                           const unsigned char *insecret,
 121                           size_t insecretlen,
 122                           unsigned char *outsecret)
 123 {
 124     size_t mdlen, prevsecretlen;
 125     int ret;
 126     EVP_PKEY_CTX *pctx = EVP_PKEY_CTX_new_id(EVP_PKEY_HKDF, NULL);
 127     static const char derived_secret_label[] = "derived";
 128     unsigned char preextractsec[EVP_MAX_MD_SIZE];
 129
 130     if (pctx == NULL)
 131         return 0;
 132
 133     mdlen = EVP_MD_size(md);
 134
 135     if (insecret == NULL) {
 136         insecret = default_zeros;
 137         insecretlen = mdlen;
 138     }
 139     if (prevsecret == NULL) {
 140         prevsecret = default_zeros;
 141         prevsecretlen = 0;
 142     } else {
 143         EVP_MD_CTX *mctx = EVP_MD_CTX_new();
 144         unsigned char hash[EVP_MAX_MD_SIZE];
 145
 146         /* The pre-extract derive step uses a hash of no messages */
 147         if (mctx == NULL
 148                 || EVP_DigestInit_ex(mctx, md, NULL) <= 0
 149                 || EVP_DigestFinal_ex(mctx, hash, NULL) <= 0) {
 150             EVP_MD_CTX_free(mctx);
 151             return 0;
 152         }
 153         EVP_MD_CTX_free(mctx);
 154
 155         /* Generate the pre-extract secret */
 156         if (!tls13_hkdf_expand(s, md, prevsecret,
 157                                (unsigned char *)derived_secret_label,
 158                                sizeof(derived_secret_label) - 1, hash,
 159                                preextractsec, mdlen))
 160             return 0;
 161
 162         prevsecret = preextractsec;
 163         prevsecretlen = mdlen;
 164     }
 165
 166     ret = EVP_PKEY_derive_init(pctx) <= 0
 167             || EVP_PKEY_CTX_hkdf_mode(pctx, EVP_PKEY_HKDEF_MODE_EXTRACT_ONLY)
 168                <= 0
 169             || EVP_PKEY_CTX_set_hkdf_md(pctx, md) <= 0
 170             || EVP_PKEY_CTX_set1_hkdf_key(pctx, insecret, insecretlen) <= 0
 171             || EVP_PKEY_CTX_set1_hkdf_salt(pctx, prevsecret, prevsecretlen)
 172                <= 0
 173             || EVP_PKEY_derive(pctx, outsecret, &mdlen)
 174                <= 0;
 175
 176     EVP_PKEY_CTX_free(pctx);
 177     if (prevsecret == preextractsec)
 178         OPENSSL_cleanse(preextractsec, mdlen);
 179     return ret == 0;
 180 }
 181
 182 /*
 183  * Given an input secret |insecret| of length |insecretlen| generate the
 184  * handshake secret. This requires the early secret to already have been
 185  * generated. Returns 1 on success  0 on failure.
 186  */
 187 int tls13_generate_handshake_secret(SSL *s, const unsigned char *insecret,
 188                                 size_t insecretlen)
 189 {
 190     return tls13_generate_secret(s, ssl_handshake_md(s), s->early_secret,
 191                                  insecret, insecretlen,
 192                                  (unsigned char *)&s->handshake_secret);
 193 }
 194
 195 /*
 196  * Given the handshake secret |prev| of length |prevlen| generate the master
 197  * secret and store its length in |*secret_size|. Returns 1 on success  0 on
 198  * failure.
 199  */
 200 int tls13_generate_master_secret(SSL *s, unsigned char *out,
 201                                  unsigned char *prev, size_t prevlen,
 202                                  size_t *secret_size)
 203 {
 204     const EVP_MD *md = ssl_handshake_md(s);
 205
 206     *secret_size = EVP_MD_size(md);
 207     return tls13_generate_secret(s, md, prev, NULL, 0, out);
 208 }
 209
 210 /*
 211  * Generates the mac for the Finished message. Returns the length of the MAC or
 212  * 0 on error.
 213  */
 214 size_t tls13_final_finish_mac(SSL *s, const char *str, size_t slen,
 215                              unsigned char *out)
 216 {
 217     const EVP_MD *md = ssl_handshake_md(s);
 218     unsigned char hash[EVP_MAX_MD_SIZE];
 219     size_t hashlen, ret = 0;
 220     EVP_PKEY *key = NULL;
 221     EVP_MD_CTX *ctx = EVP_MD_CTX_new();
 222
 223     if (!ssl_handshake_hash(s, hash, sizeof(hash), &hashlen))
 224         goto err;
 225
 226     if (str == s->method->ssl3_enc->server_finished_label)
 227         key = EVP_PKEY_new_mac_key(EVP_PKEY_HMAC, NULL,
 228                                    s->server_finished_secret, hashlen);
 229     else
 230         key = EVP_PKEY_new_mac_key(EVP_PKEY_HMAC, NULL,
 231                                    s->client_finished_secret, hashlen);
 232
 233     if (key == NULL
 234             || ctx == NULL
 235             || EVP_DigestSignInit(ctx, NULL, md, NULL, key) <= 0
 236             || EVP_DigestSignUpdate(ctx, hash, hashlen) <= 0
 237             || EVP_DigestSignFinal(ctx, out, &hashlen) <= 0)
 238         goto err;
 239
 240     ret = hashlen;
 241  err:
 242     EVP_PKEY_free(key);
 243     EVP_MD_CTX_free(ctx);
 244     return ret;
 245 }
 246
 247 /*
 248  * There isn't really a key block in TLSv1.3, but we still need this function
 249  * for initialising the cipher and hash. Returns 1 on success or 0 on failure.
 250  */
 251 int tls13_setup_key_block(SSL *s)
 252 {
 253     const EVP_CIPHER *c;
 254     const EVP_MD *hash;
 255     int mac_type = NID_undef;
 256
 257     s->session->cipher = s->s3->tmp.new_cipher;
 258     if (!ssl_cipher_get_evp
 259         (s->session, &c, &hash, &mac_type, NULL, NULL, 0)) {
 260         SSLerr(SSL_F_TLS13_SETUP_KEY_BLOCK, SSL_R_CIPHER_OR_HASH_UNAVAILABLE);
 261         return 0;
 262     }
 263
 264     s->s3->tmp.new_sym_enc = c;
 265     s->s3->tmp.new_hash = hash;
 266
 267     return 1;
 268 }
 269
 270 static int derive_secret_key_and_iv(SSL *s, int sending, const EVP_MD *md,
 271                                     const EVP_CIPHER *ciph,
 272                                     const unsigned char *insecret,
 273                                     const unsigned char *hash,
 274                                     const unsigned char *label,
 275                                     size_t labellen, unsigned char *secret,
 276                                     unsigned char *iv, EVP_CIPHER_CTX *ciph_ctx)
 277 {
 278     unsigned char key[EVP_MAX_KEY_LENGTH];
 279     size_t ivlen, keylen, taglen;
 280     size_t hashlen = EVP_MD_size(md);
 281
 282     if (!tls13_hkdf_expand(s, md, insecret, label, labellen, hash, secret,
 283                            hashlen)) {
 284         SSLerr(SSL_F_DERIVE_SECRET_KEY_AND_IV, ERR_R_INTERNAL_ERROR);
 285         goto err;
 286     }
 287
 288     /* TODO(size_t): convert me */
 289     keylen = EVP_CIPHER_key_length(ciph);
 290     if (EVP_CIPHER_mode(ciph) == EVP_CIPH_CCM_MODE) {
 291         uint32_t algenc;
 292
 293         ivlen = EVP_CCM_TLS_IV_LEN;
 294         if (s->s3->tmp.new_cipher == NULL) {
 295             /* We've not selected a cipher yet - we must be doing early data */
 296             algenc = s->session->cipher->algorithm_enc;
 297         } else {
 298             algenc = s->s3->tmp.new_cipher->algorithm_enc;
 299         }
 300         if (algenc & (SSL_AES128CCM8 | SSL_AES256CCM8))
 301             taglen = EVP_CCM8_TLS_TAG_LEN;
 302          else
 303             taglen = EVP_CCM_TLS_TAG_LEN;
 304     } else {
 305         ivlen = EVP_CIPHER_iv_length(ciph);
 306         taglen = 0;
 307     }
 308
 309     if (!tls13_derive_key(s, md, secret, key, keylen)
 310             || !tls13_derive_iv(s, md, secret, iv, ivlen)) {
 311         SSLerr(SSL_F_DERIVE_SECRET_KEY_AND_IV, ERR_R_INTERNAL_ERROR);
 312         goto err;
 313     }
 314
 315     if (EVP_CipherInit_ex(ciph_ctx, ciph, NULL, NULL, NULL, sending) <= 0
 316         || !EVP_CIPHER_CTX_ctrl(ciph_ctx, EVP_CTRL_AEAD_SET_IVLEN, ivlen, NULL)
 317         || (taglen != 0 && !EVP_CIPHER_CTX_ctrl(ciph_ctx, EVP_CTRL_AEAD_SET_TAG,
 318                                                 taglen, NULL))
 319         || EVP_CipherInit_ex(ciph_ctx, NULL, NULL, key, NULL, -1) <= 0) {
 320         SSLerr(SSL_F_DERIVE_SECRET_KEY_AND_IV, ERR_R_EVP_LIB);
 321         goto err;
 322     }
 323
 324     return 1;
 325  err:
 326     OPENSSL_cleanse(key, sizeof(key));
 327     return 0;
 328 }
 329
 330 int tls13_change_cipher_state(SSL *s, int which)
 331 {
 332     static const unsigned char client_early_traffic[] = "c e traffic";
 333     static const unsigned char client_handshake_traffic[] = "c hs traffic";
 334     static const unsigned char client_application_traffic[] = "c ap traffic";
 335     static const unsigned char server_handshake_traffic[] = "s hs traffic";
 336     static const unsigned char server_application_traffic[] = "s ap traffic";
 337     static const unsigned char resumption_master_secret[] = "res master";
 338     unsigned char *iv;
 339     unsigned char secret[EVP_MAX_MD_SIZE];
 340     unsigned char hashval[EVP_MAX_MD_SIZE];
 341     unsigned char *hash = hashval;
 342     unsigned char *insecret;
 343     unsigned char *finsecret = NULL;
 344     const char *log_label = NULL;
 345     EVP_CIPHER_CTX *ciph_ctx;
 346     size_t finsecretlen = 0;
 347     const unsigned char *label;
 348     size_t labellen, hashlen = 0;
 349     int ret = 0;
 350     const EVP_MD *md = NULL;
 351     const EVP_CIPHER *cipher = NULL;
 352
 353     if (which & SSL3_CC_READ) {
 354         if (s->enc_read_ctx != NULL) {
 355             EVP_CIPHER_CTX_reset(s->enc_read_ctx);
 356         } else {
 357             s->enc_read_ctx = EVP_CIPHER_CTX_new();
 358             if (s->enc_read_ctx == NULL) {
 359                 SSLerr(SSL_F_TLS13_CHANGE_CIPHER_STATE, ERR_R_MALLOC_FAILURE);
 360                 goto err;
 361             }
 362         }
 363         ciph_ctx = s->enc_read_ctx;
 364         iv = s->read_iv;
 365
 366         RECORD_LAYER_reset_read_sequence(&s->rlayer);
 367     } else {
 368         if (s->enc_write_ctx != NULL) {
 369             EVP_CIPHER_CTX_reset(s->enc_write_ctx);
 370         } else {
 371             s->enc_write_ctx = EVP_CIPHER_CTX_new();
 372             if (s->enc_write_ctx == NULL) {
 373                 SSLerr(SSL_F_TLS13_CHANGE_CIPHER_STATE, ERR_R_MALLOC_FAILURE);
 374                 goto err;
 375             }
 376         }
 377         ciph_ctx = s->enc_write_ctx;
 378         iv = s->write_iv;
 379
 380         RECORD_LAYER_reset_write_sequence(&s->rlayer);
 381     }
 382
 383     if (((which & SSL3_CC_CLIENT) && (which & SSL3_CC_WRITE))
 384             || ((which & SSL3_CC_SERVER) && (which & SSL3_CC_READ))) {
 385         if (which & SSL3_CC_EARLY) {
 386             EVP_MD_CTX *mdctx = NULL;
 387             long handlen;
 388             void *hdata;
 389             unsigned int hashlenui;
 390             const SSL_CIPHER *sslcipher = SSL_SESSION_get0_cipher(s->session);
 391
 392             insecret = s->early_secret;
 393             label = client_early_traffic;
 394             labellen = sizeof(client_early_traffic) - 1;
 395             log_label = CLIENT_EARLY_LABEL;
 396
 397             handlen = BIO_get_mem_data(s->s3->handshake_buffer, &hdata);
 398             if (handlen <= 0) {
 399                 SSLerr(SSL_F_TLS13_CHANGE_CIPHER_STATE,
 400                        SSL_R_BAD_HANDSHAKE_LENGTH);
 401                 goto err;
 402             }
 403             if (sslcipher == NULL) {
 404                 SSLerr(SSL_F_TLS13_CHANGE_CIPHER_STATE, ERR_R_INTERNAL_ERROR);
 405                 goto err;
 406             }
 407
 408             /*
 409              * We need to calculate the handshake digest using the digest from
 410              * the session. We haven't yet selected our ciphersuite so we can't
 411              * use ssl_handshake_md().
 412              */
 413             mdctx = EVP_MD_CTX_new();
 414             if (mdctx == NULL) {
 415                 SSLerr(SSL_F_TLS13_CHANGE_CIPHER_STATE, ERR_R_MALLOC_FAILURE);
 416                 goto err;
 417             }
 418             cipher = EVP_get_cipherbynid(SSL_CIPHER_get_cipher_nid(sslcipher));
 419             md = ssl_md(sslcipher->algorithm2);
 420             if (md == NULL || !EVP_DigestInit_ex(mdctx, md, NULL)
 421                     || !EVP_DigestUpdate(mdctx, hdata, handlen)
 422                     || !EVP_DigestFinal_ex(mdctx, hashval, &hashlenui)) {
 423                 SSLerr(SSL_F_TLS13_CHANGE_CIPHER_STATE, ERR_R_INTERNAL_ERROR);
 424                 EVP_MD_CTX_free(mdctx);
 425                 goto err;
 426             }
 427             hashlen = hashlenui;
 428             EVP_MD_CTX_free(mdctx);
 429         } else if (which & SSL3_CC_HANDSHAKE) {
 430             insecret = s->handshake_secret;
 431             finsecret = s->client_finished_secret;
 432             finsecretlen = EVP_MD_size(ssl_handshake_md(s));
 433             label = client_handshake_traffic;
 434             labellen = sizeof(client_handshake_traffic) - 1;
 435             log_label = CLIENT_HANDSHAKE_LABEL;
 436             /*
 437              * The handshake hash used for the server read/client write handshake
 438              * traffic secret is the same as the hash for the server
 439              * write/client read handshake traffic secret. However, if we
 440              * processed early data then we delay changing the server
 441              * read/client write cipher state until later, and the handshake
 442              * hashes have moved on. Therefore we use the value saved earlier
 443              * when we did the server write/client read change cipher state.
 444              */
 445             hash = s->handshake_traffic_hash;
 446         } else {
 447             insecret = s->master_secret;
 448             label = client_application_traffic;
 449             labellen = sizeof(client_application_traffic) - 1;
 450             log_label = CLIENT_APPLICATION_LABEL;
 451             /*
 452              * For this we only use the handshake hashes up until the server
 453              * Finished hash. We do not include the client's Finished, which is
 454              * what ssl_handshake_hash() would give us. Instead we use the
 455              * previously saved value.
 456              */
 457             hash = s->server_finished_hash;
 458         }
 459     } else {
 460         /* Early data never applies to client-read/server-write */
 461         if (which & SSL3_CC_HANDSHAKE) {
 462             insecret = s->handshake_secret;
 463             finsecret = s->server_finished_secret;
 464             finsecretlen = EVP_MD_size(ssl_handshake_md(s));
 465             label = server_handshake_traffic;
 466             labellen = sizeof(server_handshake_traffic) - 1;
 467             log_label = SERVER_HANDSHAKE_LABEL;
 468         } else {
 469             insecret = s->master_secret;
 470             label = server_application_traffic;
 471             labellen = sizeof(server_application_traffic) - 1;
 472             log_label = SERVER_APPLICATION_LABEL;
 473         }
 474     }
 475
 476     if (!(which & SSL3_CC_EARLY)) {
 477         md = ssl_handshake_md(s);
 478         cipher = s->s3->tmp.new_sym_enc;
 479         if (!ssl3_digest_cached_records(s, 1)
 480                 || !ssl_handshake_hash(s, hashval, sizeof(hashval), &hashlen)) {
 481             SSLerr(SSL_F_TLS13_CHANGE_CIPHER_STATE, ERR_R_INTERNAL_ERROR);
 482             goto err;
 483         }
 484     }
 485
 486     /*
 487      * Save the hash of handshakes up to now for use when we calculate the
 488      * client application traffic secret
 489      */
 490     if (label == server_application_traffic)
 491         memcpy(s->server_finished_hash, hashval, hashlen);
 492
 493     if (label == server_handshake_traffic)
 494         memcpy(s->handshake_traffic_hash, hashval, hashlen);
 495
 496     if (label == client_application_traffic) {
 497         /*
 498          * We also create the resumption master secret, but this time use the
 499          * hash for the whole handshake including the Client Finished
 500          */
 501         if (!tls13_hkdf_expand(s, ssl_handshake_md(s), insecret,
 502                                resumption_master_secret,
 503                                sizeof(resumption_master_secret) - 1,
 504                                hashval, s->session->master_key, hashlen)) {
 505             SSLerr(SSL_F_TLS13_CHANGE_CIPHER_STATE, ERR_R_INTERNAL_ERROR);
 506             goto err;
 507         }
 508         s->session->master_key_length = hashlen;
 509     }
 510
 511     if (!derive_secret_key_and_iv(s, which & SSL3_CC_WRITE, md, cipher,
 512                                   insecret, hash, label, labellen, secret, iv,
 513                                   ciph_ctx)) {
 514         goto err;
 515     }
 516
 517     if (label == server_application_traffic)
 518         memcpy(s->server_app_traffic_secret, secret, hashlen);
 519     else if (label == client_application_traffic)
 520         memcpy(s->client_app_traffic_secret, secret, hashlen);
 521
 522     if (!ssl_log_secret(s, log_label, secret, hashlen)) {
 523         SSLerr(SSL_F_TLS13_CHANGE_CIPHER_STATE, ERR_R_INTERNAL_ERROR);
 524         goto err;
 525     }
 526
 527     if (finsecret != NULL
 528             && !tls13_derive_finishedkey(s, ssl_handshake_md(s), secret,
 529                                          finsecret, finsecretlen)) {
 530         SSLerr(SSL_F_TLS13_CHANGE_CIPHER_STATE, ERR_R_INTERNAL_ERROR);
 531         goto err;
 532     }
 533
 534     ret = 1;
 535  err:
 536     OPENSSL_cleanse(secret, sizeof(secret));
 537     return ret;
 538 }
 539
 540 int tls13_update_key(SSL *s, int sending)
 541 {
 542     static const unsigned char application_traffic[] = "traffic upd";
 543     const EVP_MD *md = ssl_handshake_md(s);
 544     size_t hashlen = EVP_MD_size(md);
 545     unsigned char *insecret, *iv;
 546     unsigned char secret[EVP_MAX_MD_SIZE];
 547     EVP_CIPHER_CTX *ciph_ctx;
 548     int ret = 0;
 549
 550     if (s->server == sending)
 551         insecret = s->server_app_traffic_secret;
 552     else
 553         insecret = s->client_app_traffic_secret;
 554
 555     if (sending) {
 556         iv = s->write_iv;
 557         ciph_ctx = s->enc_write_ctx;
 558         RECORD_LAYER_reset_write_sequence(&s->rlayer);
 559     } else {
 560         iv = s->read_iv;
 561         ciph_ctx = s->enc_read_ctx;
 562         RECORD_LAYER_reset_read_sequence(&s->rlayer);
 563     }
 564
 565     if (!derive_secret_key_and_iv(s, sending, ssl_handshake_md(s),
 566                                   s->s3->tmp.new_sym_enc, insecret, NULL,
 567                                   application_traffic,
 568                                   sizeof(application_traffic) - 1, secret, iv,
 569                                   ciph_ctx))
 570         goto err;
 571
 572     memcpy(insecret, secret, hashlen);
 573
 574     ret = 1;
 575  err:
 576     OPENSSL_cleanse(secret, sizeof(secret));
 577     return ret;
 578 }
 579
 580 int tls13_alert_code(int code)
 581 {
 582     if (code == SSL_AD_MISSING_EXTENSION)
 583         return code;
 584
 585     return tls1_alert_code(code);
 586 }