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 static const unsigned char keylabel[] = "key";
  21 static const unsigned char ivlabel[] = "iv";
  22
  23 /*
  24  * Given a |secret|; a |label| of length |labellen|; and a |hash| of the
  25  * handshake messages, derive a new secret |outlen| bytes long and store it in
  26  * the location pointed to be |out|. The |hash| value may be NULL.
  27  *
  28  * Returns 1 on success  0 on failure.
  29  */
  30 static int tls13_hkdf_expand(SSL *s, const unsigned char *secret,
  31                              const unsigned char *label, size_t labellen,
  32                              const unsigned char *hash,
  33                              unsigned char *out, size_t outlen)
  34 {
  35     const unsigned char label_prefix[] = "TLS 1.3, ";
  36     const EVP_MD *md = ssl_handshake_md(s);
  37     EVP_PKEY_CTX *pctx = EVP_PKEY_CTX_new_id(EVP_PKEY_HKDF, NULL);
  38     int ret;
  39     size_t hkdflabellen;
  40     size_t hashlen;
  41     /*
  42      * 2 bytes for length of whole HkdfLabel + 1 byte for length of combined
  43      * prefix and label + bytes for the label itself + bytes for the hash
  44      */
  45     unsigned char hkdflabel[sizeof(uint16_t) + sizeof(uint8_t) +
  46                             + sizeof(label_prefix) + TLS13_MAX_LABEL_LEN
  47                             + EVP_MAX_MD_SIZE];
  48     WPACKET pkt;
  49
  50     if (pctx == NULL)
  51         return 0;
  52
  53     hashlen = EVP_MD_size(md);
  54
  55     if (!WPACKET_init_static_len(&pkt, hkdflabel, sizeof(hkdflabel), 0)
  56             || !WPACKET_put_bytes_u16(&pkt, outlen)
  57             || !WPACKET_start_sub_packet_u8(&pkt)
  58             || !WPACKET_memcpy(&pkt, label_prefix, sizeof(label_prefix) - 1)
  59             || !WPACKET_memcpy(&pkt, label, labellen)
  60             || !WPACKET_close(&pkt)
  61             || !WPACKET_sub_memcpy_u8(&pkt, hash, (hash == NULL) ? 0 : hashlen)
  62             || !WPACKET_get_total_written(&pkt, &hkdflabellen)
  63             || !WPACKET_finish(&pkt)) {
  64         WPACKET_cleanup(&pkt);
  65         return 0;
  66     }
  67
  68     ret = EVP_PKEY_derive_init(pctx) <= 0
  69             || EVP_PKEY_CTX_hkdf_mode(pctx, EVP_PKEY_HKDEF_MODE_EXPAND_ONLY)
  70                <= 0
  71             || EVP_PKEY_CTX_set_hkdf_md(pctx, md) <= 0
  72             || EVP_PKEY_CTX_set1_hkdf_key(pctx, secret, hashlen) <= 0
  73             || EVP_PKEY_CTX_add1_hkdf_info(pctx, hkdflabel, hkdflabellen) <= 0
  74             || EVP_PKEY_derive(pctx, out, &outlen) <= 0;
  75
  76     EVP_PKEY_CTX_free(pctx);
  77
  78     return ret == 0;
  79 }
  80
  81 /*
  82  * Given a input secret |insecret| and a |label| of length |labellen|, derive a
  83  * new |secret|. This will be the length of the current hash output size and
  84  * will be based on the current state of the handshake hashes.
  85  *
  86  * Returns 1 on success  0 on failure.
  87  */
  88 int tls13_derive_secret(SSL *s, const unsigned char *insecret,
  89                         const unsigned char *label, size_t labellen,
  90                         unsigned char *secret)
  91 {
  92     unsigned char hash[EVP_MAX_MD_SIZE];
  93     size_t hashlen;
  94
  95     if (!ssl3_digest_cached_records(s, 1))
  96         return 0;
  97
  98     if (!ssl_handshake_hash(s, hash, sizeof(hash), &hashlen))
  99         return 0;
 100
 101     return tls13_hkdf_expand(s, insecret, label, labellen, hash, secret,
 102                              hashlen);
 103 }
 104
 105 /*
 106  * Given a |secret| generate a |key| of length |keylen| bytes.
 107  *
 108  * Returns 1 on success  0 on failure.
 109  */
 110 int tls13_derive_key(SSL *s, const unsigned char *secret, unsigned char *key,
 111                      size_t keylen)
 112 {
 113     return tls13_hkdf_expand(s, secret, keylabel, sizeof(keylabel) - 1, NULL,
 114                              key, keylen);
 115 }
 116
 117 /*
 118  * Given a |secret| generate an |iv| of length |ivlen| bytes.
 119  *
 120  * Returns 1 on success  0 on failure.
 121  */
 122 int tls13_derive_iv(SSL *s, const unsigned char *secret, unsigned char *iv,
 123                     size_t ivlen)
 124 {
 125     return tls13_hkdf_expand(s, secret, ivlabel, sizeof(ivlabel) - 1, NULL,
 126                              iv, ivlen);
 127 }
 128
 129 /*
 130  * Given the previous secret |prevsecret| and a new input secret |insecret| of
 131  * length |insecretlen|, generate a new secret and store it in the location
 132  * pointed to by |outsecret|.
 133  *
 134  * Returns 1 on success  0 on failure.
 135  */
 136 static int tls13_generate_secret(SSL *s, const unsigned char *prevsecret,
 137                                  const unsigned char *insecret,
 138                                  size_t insecretlen,
 139                                  unsigned char *outsecret)
 140 {
 141     const EVP_MD *md = ssl_handshake_md(s);
 142     size_t mdlen, prevsecretlen;
 143     int ret;
 144     EVP_PKEY_CTX *pctx = EVP_PKEY_CTX_new_id(EVP_PKEY_HKDF, NULL);
 145
 146     if (pctx == NULL)
 147         return 0;
 148
 149     mdlen = EVP_MD_size(md);
 150
 151     if (insecret == NULL) {
 152         insecret = default_zeros;
 153         insecretlen = mdlen;
 154     }
 155     if (prevsecret == NULL) {
 156         prevsecret = default_zeros;
 157         prevsecretlen = 0;
 158     } else {
 159         prevsecretlen = mdlen;
 160     }
 161
 162     ret = EVP_PKEY_derive_init(pctx) <= 0
 163             || EVP_PKEY_CTX_hkdf_mode(pctx, EVP_PKEY_HKDEF_MODE_EXTRACT_ONLY)
 164                <= 0
 165             || EVP_PKEY_CTX_set_hkdf_md(pctx, md) <= 0
 166             || EVP_PKEY_CTX_set1_hkdf_key(pctx, insecret, insecretlen) <= 0
 167             || EVP_PKEY_CTX_set1_hkdf_salt(pctx, prevsecret, prevsecretlen)
 168                <= 0
 169             || EVP_PKEY_derive(pctx, outsecret, &mdlen)
 170                <= 0;
 171
 172     EVP_PKEY_CTX_free(pctx);
 173     return ret == 0;
 174 }
 175
 176 /*
 177  * Given an input secret |insecret| of length |insecretlen| generate the early
 178  * secret.
 179  *
 180  * Returns 1 on success  0 on failure.
 181  */
 182 int tls13_generate_early_secret(SSL *s, const unsigned char *insecret,
 183                                 size_t insecretlen)
 184 {
 185     return tls13_generate_secret(s, NULL, insecret, insecretlen,
 186                                  (unsigned char *)&s->early_secret);
 187 }
 188
 189 /*
 190  * Given an input secret |insecret| of length |insecretlen| generate the
 191  * handshake secret. This requires the early secret to already have been
 192  * generated.
 193  *
 194  * Returns 1 on success  0 on failure.
 195  */
 196 int tls13_generate_handshake_secret(SSL *s, const unsigned char *insecret,
 197                                 size_t insecretlen)
 198 {
 199     return tls13_generate_secret(s, s->early_secret, insecret, insecretlen,
 200                                  (unsigned char *)&s->handshake_secret);
 201 }
 202
 203 /*
 204  * Given the handshake secret |prev| of length |prevlen| generate the master
 205  * secret and store its length in |*secret_size|
 206  *
 207  * Returns 1 on success  0 on failure.
 208  */
 209 int tls13_generate_master_secret(SSL *s, unsigned char *out,
 210                                  unsigned char *prev, size_t prevlen,
 211                                  size_t *secret_size)
 212 {
 213     *secret_size = EVP_MD_size(ssl_handshake_md(s));
 214     return tls13_generate_secret(s, prev, NULL, 0, out);
 215 }
 216
 217 const unsigned char client_handshake_traffic[] =
 218     "client handshake traffic secret";
 219 const unsigned char client_application_traffic[] =
 220     "client application traffic secret";
 221 const unsigned char server_handshake_traffic[] =
 222     "server handshake traffic secret";
 223 const unsigned char server_application_traffic[] =
 224     "server application traffic secret";
 225
 226 int tls13_change_cipher_state(SSL *s, int which)
 227 {
 228     unsigned char key[EVP_MAX_KEY_LENGTH];
 229     unsigned char iv[EVP_MAX_IV_LENGTH];
 230     unsigned char secret[EVP_MAX_MD_SIZE];
 231     unsigned char *insecret;
 232     EVP_CIPHER_CTX *ciph_ctx;
 233     const EVP_CIPHER *ciph = s->s3->tmp.new_sym_enc;;
 234     size_t ivlen, keylen;
 235     const unsigned char *label;
 236     size_t labellen;
 237
 238     if (which & SSL3_CC_READ) {
 239         if (s->enc_read_ctx != NULL) {
 240             EVP_CIPHER_CTX_reset(s->enc_read_ctx);
 241         } else {
 242             s->enc_read_ctx = EVP_CIPHER_CTX_new();
 243             if (s->enc_read_ctx == NULL) {
 244                 SSLerr(SSL_F_TLS13_CHANGE_CIPHER_STATE, ERR_R_MALLOC_FAILURE);
 245                 goto err;
 246             }
 247         }
 248         ciph_ctx = s->enc_read_ctx;
 249
 250         RECORD_LAYER_reset_read_sequence(&s->rlayer);
 251     } else {
 252         if (s->enc_write_ctx != NULL) {
 253             EVP_CIPHER_CTX_reset(s->enc_write_ctx);
 254         } else {
 255             s->enc_write_ctx = EVP_CIPHER_CTX_new();
 256             if (s->enc_write_ctx == NULL) {
 257                 SSLerr(SSL_F_TLS13_CHANGE_CIPHER_STATE, ERR_R_MALLOC_FAILURE);
 258                 goto err;
 259             }
 260         }
 261         ciph_ctx = s->enc_write_ctx;
 262
 263         RECORD_LAYER_reset_write_sequence(&s->rlayer);
 264     }
 265
 266     if (((which & SSL3_CC_CLIENT) && (which & SSL3_CC_WRITE))
 267             || ((which & SSL3_CC_SERVER) && (which & SSL3_CC_READ))) {
 268         if (which & SSL3_CC_HANDSHAKE) {
 269             insecret = s->handshake_secret;
 270             label = client_handshake_traffic;
 271             labellen = sizeof(client_handshake_traffic) - 1;
 272         } else {
 273             insecret = s->session->master_key;
 274             label = client_application_traffic;
 275             labellen = sizeof(client_application_traffic) - 1;
 276         }
 277     } else {
 278         if (which & SSL3_CC_HANDSHAKE) {
 279             insecret = s->handshake_secret;
 280             label = server_handshake_traffic;
 281             labellen = sizeof(server_handshake_traffic) - 1;
 282         } else {
 283             insecret = s->session->master_key;
 284             label = server_application_traffic;
 285             labellen = sizeof(server_application_traffic) - 1;
 286         }
 287     }
 288
 289     if (!tls13_derive_secret(s, insecret, label, labellen, secret)) {
 290         SSLerr(SSL_F_TLS13_CHANGE_CIPHER_STATE, ERR_R_INTERNAL_ERROR);
 291         goto err;
 292     }
 293
 294     /* TODO(size_t): convert me */
 295     keylen = EVP_CIPHER_key_length(ciph);
 296
 297     if (EVP_CIPHER_mode(ciph) == EVP_CIPH_GCM_MODE)
 298         ivlen = EVP_GCM_TLS_FIXED_IV_LEN;
 299     else if (EVP_CIPHER_mode(ciph) == EVP_CIPH_CCM_MODE)
 300         ivlen = EVP_CCM_TLS_FIXED_IV_LEN;
 301     else
 302         ivlen = EVP_CIPHER_iv_length(ciph);
 303
 304     if (!tls13_derive_key(s, secret, key, keylen)
 305             || !tls13_derive_iv(s, secret, iv, ivlen)) {
 306         SSLerr(SSL_F_TLS13_CHANGE_CIPHER_STATE, ERR_R_INTERNAL_ERROR);
 307         goto err;
 308     }
 309
 310     if (EVP_CIPHER_mode(ciph) == EVP_CIPH_GCM_MODE) {
 311         if (!EVP_CipherInit_ex(ciph_ctx, ciph, NULL, key, NULL,
 312                                (which & SSL3_CC_WRITE))
 313                 || !EVP_CIPHER_CTX_ctrl(ciph_ctx, EVP_CTRL_GCM_SET_IV_FIXED,
 314                                         (int)ivlen, iv)) {
 315             SSLerr(SSL_F_TLS13_CHANGE_CIPHER_STATE, ERR_R_EVP_LIB);
 316             goto err;
 317         }
 318     } else if (EVP_CIPHER_mode(ciph) == EVP_CIPH_CCM_MODE) {
 319         int taglen;
 320         if (s->s3->tmp.new_cipher->algorithm_enc
 321                 & (SSL_AES128CCM8 | SSL_AES256CCM8))
 322             taglen = 8;
 323         else
 324             taglen = 16;
 325         if (!EVP_CipherInit_ex(ciph_ctx, ciph, NULL, NULL, NULL,
 326                                (which & SSL3_CC_WRITE))
 327                 || !EVP_CIPHER_CTX_ctrl(ciph_ctx, EVP_CTRL_AEAD_SET_IVLEN, 12,
 328                                         NULL)
 329                 || !EVP_CIPHER_CTX_ctrl(ciph_ctx, EVP_CTRL_AEAD_SET_TAG, taglen,
 330                                         NULL)
 331                 || !EVP_CIPHER_CTX_ctrl(ciph_ctx, EVP_CTRL_CCM_SET_IV_FIXED,
 332                                         (int)ivlen, iv)
 333                 || !EVP_CipherInit_ex(ciph_ctx, NULL, NULL, key, NULL, -1)) {
 334             SSLerr(SSL_F_TLS13_CHANGE_CIPHER_STATE, ERR_R_EVP_LIB);
 335             goto err;
 336         }
 337     } else {
 338         if (!EVP_CipherInit_ex(ciph_ctx, ciph, NULL, key, iv,
 339                                (which & SSL3_CC_WRITE))) {
 340             SSLerr(SSL_F_TLS13_CHANGE_CIPHER_STATE, ERR_R_EVP_LIB);
 341             goto err;
 342         }
 343     }
 344
 345 #ifdef OPENSSL_SSL_TRACE_CRYPTO
 346     if (s->msg_callback) {
 347         int wh = which & SSL3_CC_WRITE ? TLS1_RT_CRYPTO_WRITE : 0;
 348
 349         if (ciph->key_len)
 350             s->msg_callback(2, s->version, wh | TLS1_RT_CRYPTO_KEY,
 351                             key, ciph->key_len, s, s->msg_callback_arg);
 352         if (ivlen) {
 353             if (EVP_CIPHER_mode(ciph) == EVP_CIPH_GCM_MODE)
 354                 wh |= TLS1_RT_CRYPTO_FIXED_IV;
 355             else
 356                 wh |= TLS1_RT_CRYPTO_IV;
 357             s->msg_callback(2, s->version, wh, iv, ivlen, s,
 358                             s->msg_callback_arg);
 359         }
 360     }
 361 #endif
 362
 363     OPENSSL_cleanse(secret, sizeof(secret));
 364     OPENSSL_cleanse(key, sizeof(key));
 365     OPENSSL_cleanse(iv, sizeof(iv));
 366     return 1;
 367
 368  err:
 369     OPENSSL_cleanse(secret, sizeof(secret));
 370     OPENSSL_cleanse(key, sizeof(key));
 371     OPENSSL_cleanse(iv, sizeof(iv));
 372     return 0;
 373 }