crypto/kdf/tls1_prf.c

   1 /*
   2  * Copyright 2016-2018 The OpenSSL Project Authors. All Rights Reserved.
   3  *
   4  * Licensed under the Apache License 2.0 (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 /*
  11  * Refer to "The TLS Protocol Version 1.0" Section 5
  12  * (https://tools.ietf.org/html/rfc2246#section-5) and
  13  * "The Transport Layer Security (TLS) Protocol Version 1.2" Section 5
  14  * (https://tools.ietf.org/html/rfc5246#section-5).
  15  *
  16  * For TLS v1.0 and TLS v1.1 the TLS PRF algorithm is given by:
  17  *
  18  *   PRF(secret, label, seed) = P_MD5(S1, label + seed) XOR
  19  *                              P_SHA-1(S2, label + seed)
  20  *
  21  * where P_MD5 and P_SHA-1 are defined by P_<hash>, below, and S1 and S2 are
  22  * two halves of the secret (with the possibility of one shared byte, in the
  23  * case where the length of the original secret is odd).  S1 is taken from the
  24  * first half of the secret, S2 from the second half.
  25  *
  26  * For TLS v1.2 the TLS PRF algorithm is given by:
  27  *
  28  *   PRF(secret, label, seed) = P_<hash>(secret, label + seed)
  29  *
  30  * where hash is SHA-256 for all cipher suites defined in RFC 5246 as well as
  31  * those published prior to TLS v1.2 while the TLS v1.2 protocol is in effect,
  32  * unless defined otherwise by the cipher suite.
  33  *
  34  * P_<hash> is an expansion function that uses a single hash function to expand
  35  * a secret and seed into an arbitrary quantity of output:
  36  *
  37  *   P_<hash>(secret, seed) = HMAC_<hash>(secret, A(1) + seed) +
  38  *                            HMAC_<hash>(secret, A(2) + seed) +
  39  *                            HMAC_<hash>(secret, A(3) + seed) + ...
  40  *
  41  * where + indicates concatenation.  P_<hash> can be iterated as many times as
  42  * is necessary to produce the required quantity of data.
  43  *
  44  * A(i) is defined as:
  45  *     A(0) = seed
  46  *     A(i) = HMAC_<hash>(secret, A(i-1))
  47  */
  48 #include <stdio.h>
  49 #include <stdarg.h>
  50 #include <string.h>
  51 #include "internal/cryptlib.h"
  52 #include <openssl/evp.h>
  53 #include <openssl/kdf.h>
  54 #include <openssl/core_names.h>
  55 #include <openssl/params.h>
  56 #include "internal/evp_int.h"
  57 #include "kdf_local.h"
  58
  59 static void kdf_tls1_prf_reset(EVP_KDF_IMPL *impl);
  60 static int tls1_prf_alg(const EVP_MD *md,
  61                         const unsigned char *sec, size_t slen,
  62                         const unsigned char *seed, size_t seed_len,
  63                         unsigned char *out, size_t olen);
  64
  65 #define TLS1_PRF_MAXBUF 1024
  66
  67 /* TLS KDF kdf context structure */
  68
  69 struct evp_kdf_impl_st {
  70     /* Digest to use for PRF */
  71     const EVP_MD *md;
  72     /* Secret value to use for PRF */
  73     unsigned char *sec;
  74     size_t seclen;
  75     /* Buffer of concatenated seed data */
  76     unsigned char seed[TLS1_PRF_MAXBUF];
  77     size_t seedlen;
  78 };
  79
  80 static EVP_KDF_IMPL *kdf_tls1_prf_new(void)
  81 {
  82     EVP_KDF_IMPL *impl;
  83
  84     if ((impl = OPENSSL_zalloc(sizeof(*impl))) == NULL)
  85         KDFerr(KDF_F_KDF_TLS1_PRF_NEW, ERR_R_MALLOC_FAILURE);
  86     return impl;
  87 }
  88
  89 static void kdf_tls1_prf_free(EVP_KDF_IMPL *impl)
  90 {
  91     kdf_tls1_prf_reset(impl);
  92     OPENSSL_free(impl);
  93 }
  94
  95 static void kdf_tls1_prf_reset(EVP_KDF_IMPL *impl)
  96 {
  97     OPENSSL_clear_free(impl->sec, impl->seclen);
  98     OPENSSL_cleanse(impl->seed, impl->seedlen);
  99     memset(impl, 0, sizeof(*impl));
 100 }
 101
 102 static int kdf_tls1_prf_ctrl(EVP_KDF_IMPL *impl, int cmd, va_list args)
 103 {
 104     const unsigned char *p;
 105     size_t len;
 106     const EVP_MD *md;
 107
 108     switch (cmd) {
 109     case EVP_KDF_CTRL_SET_MD:
 110         md = va_arg(args, const EVP_MD *);
 111         if (md == NULL)
 112             return 0;
 113
 114         impl->md = md;
 115         return 1;
 116
 117     case EVP_KDF_CTRL_SET_TLS_SECRET:
 118         p = va_arg(args, const unsigned char *);
 119         len = va_arg(args, size_t);
 120         OPENSSL_clear_free(impl->sec, impl->seclen);
 121         impl->sec = OPENSSL_memdup(p, len);
 122         if (impl->sec == NULL)
 123             return 0;
 124
 125         impl->seclen = len;
 126         return 1;
 127
 128     case EVP_KDF_CTRL_RESET_TLS_SEED:
 129         OPENSSL_cleanse(impl->seed, impl->seedlen);
 130         impl->seedlen = 0;
 131         return 1;
 132
 133     case EVP_KDF_CTRL_ADD_TLS_SEED:
 134         p = va_arg(args, const unsigned char *);
 135         len = va_arg(args, size_t);
 136         if (len == 0 || p == NULL)
 137             return 1;
 138
 139         if (len > (TLS1_PRF_MAXBUF - impl->seedlen))
 140             return 0;
 141
 142         memcpy(impl->seed + impl->seedlen, p, len);
 143         impl->seedlen += len;
 144         return 1;
 145
 146     default:
 147         return -2;
 148     }
 149 }
 150
 151 static int kdf_tls1_prf_ctrl_str(EVP_KDF_IMPL *impl,
 152                                  const char *type, const char *value)
 153 {
 154     if (value == NULL) {
 155         KDFerr(KDF_F_KDF_TLS1_PRF_CTRL_STR, KDF_R_VALUE_MISSING);
 156         return 0;
 157     }
 158     if (strcmp(type, "digest") == 0)
 159         return kdf_md2ctrl(impl, kdf_tls1_prf_ctrl, EVP_KDF_CTRL_SET_MD, value);
 160
 161     if (strcmp(type, "secret") == 0)
 162         return kdf_str2ctrl(impl, kdf_tls1_prf_ctrl,
 163                             EVP_KDF_CTRL_SET_TLS_SECRET, value);
 164
 165     if (strcmp(type, "hexsecret") == 0)
 166         return kdf_hex2ctrl(impl, kdf_tls1_prf_ctrl,
 167                             EVP_KDF_CTRL_SET_TLS_SECRET, value);
 168
 169     if (strcmp(type, "seed") == 0)
 170         return kdf_str2ctrl(impl, kdf_tls1_prf_ctrl, EVP_KDF_CTRL_ADD_TLS_SEED,
 171                             value);
 172
 173     if (strcmp(type, "hexseed") == 0)
 174         return kdf_hex2ctrl(impl, kdf_tls1_prf_ctrl, EVP_KDF_CTRL_ADD_TLS_SEED,
 175                             value);
 176
 177     return -2;
 178 }
 179
 180 static int kdf_tls1_prf_derive(EVP_KDF_IMPL *impl, unsigned char *key,
 181                                size_t keylen)
 182 {
 183     if (impl->md == NULL) {
 184         KDFerr(KDF_F_KDF_TLS1_PRF_DERIVE, KDF_R_MISSING_MESSAGE_DIGEST);
 185         return 0;
 186     }
 187     if (impl->sec == NULL) {
 188         KDFerr(KDF_F_KDF_TLS1_PRF_DERIVE, KDF_R_MISSING_SECRET);
 189         return 0;
 190     }
 191     if (impl->seedlen == 0) {
 192         KDFerr(KDF_F_KDF_TLS1_PRF_DERIVE, KDF_R_MISSING_SEED);
 193         return 0;
 194     }
 195     return tls1_prf_alg(impl->md, impl->sec, impl->seclen,
 196                         impl->seed, impl->seedlen,
 197                         key, keylen);
 198 }
 199
 200 const EVP_KDF tls1_prf_kdf_meth = {
 201     EVP_KDF_TLS1_PRF,
 202     kdf_tls1_prf_new,
 203     kdf_tls1_prf_free,
 204     kdf_tls1_prf_reset,
 205     kdf_tls1_prf_ctrl,
 206     kdf_tls1_prf_ctrl_str,
 207     NULL,
 208     kdf_tls1_prf_derive
 209 };
 210
 211 /*
 212  * Refer to "The TLS Protocol Version 1.0" Section 5
 213  * (https://tools.ietf.org/html/rfc2246#section-5) and
 214  * "The Transport Layer Security (TLS) Protocol Version 1.2" Section 5
 215  * (https://tools.ietf.org/html/rfc5246#section-5).
 216  *
 217  * P_<hash> is an expansion function that uses a single hash function to expand
 218  * a secret and seed into an arbitrary quantity of output:
 219  *
 220  *   P_<hash>(secret, seed) = HMAC_<hash>(secret, A(1) + seed) +
 221  *                            HMAC_<hash>(secret, A(2) + seed) +
 222  *                            HMAC_<hash>(secret, A(3) + seed) + ...
 223  *
 224  * where + indicates concatenation.  P_<hash> can be iterated as many times as
 225  * is necessary to produce the required quantity of data.
 226  *
 227  * A(i) is defined as:
 228  *     A(0) = seed
 229  *     A(i) = HMAC_<hash>(secret, A(i-1))
 230  */
 231 static int tls1_prf_P_hash(const EVP_MD *md,
 232                            const unsigned char *sec, size_t sec_len,
 233                            const unsigned char *seed, size_t seed_len,
 234                            unsigned char *out, size_t olen)
 235 {
 236     size_t chunk;
 237     EVP_MAC *mac = NULL;
 238     EVP_MAC_CTX *ctx = NULL, *ctx_Ai = NULL, *ctx_init = NULL;
 239     unsigned char Ai[EVP_MAX_MD_SIZE];
 240     size_t Ai_len;
 241     int ret = 0;
 242     OSSL_PARAM params[4];
 243     int mac_flags;
 244     const char *mdname = EVP_MD_name(md);
 245
 246     mac = EVP_MAC_fetch(NULL, OSSL_MAC_NAME_HMAC, NULL); /* Implicit fetch */
 247     ctx_init = EVP_MAC_CTX_new(mac);
 248     if (ctx_init == NULL)
 249         goto err;
 250
 251     /* TODO(3.0) rethink "flags", also see hmac.c in providers */
 252     mac_flags = EVP_MD_CTX_FLAG_NON_FIPS_ALLOW;
 253     params[0] = OSSL_PARAM_construct_int(OSSL_MAC_PARAM_FLAGS, &mac_flags);
 254     params[1] = OSSL_PARAM_construct_utf8_string(OSSL_MAC_PARAM_DIGEST,
 255                                                  (char *)mdname, 0);
 256     params[2] = OSSL_PARAM_construct_octet_string(OSSL_MAC_PARAM_KEY,
 257                                                   (void *)sec, sec_len);
 258     params[3] = OSSL_PARAM_construct_end();
 259     if (!EVP_MAC_CTX_set_params(ctx_init, params))
 260         goto err;
 261     if (!EVP_MAC_init(ctx_init))
 262         goto err;
 263     chunk = EVP_MAC_size(ctx_init);
 264     if (chunk == 0)
 265         goto err;
 266     /* A(0) = seed */
 267     ctx_Ai = EVP_MAC_CTX_dup(ctx_init);
 268     if (ctx_Ai == NULL)
 269         goto err;
 270     if (seed != NULL && !EVP_MAC_update(ctx_Ai, seed, seed_len))
 271         goto err;
 272
 273     for (;;) {
 274         /* calc: A(i) = HMAC_<hash>(secret, A(i-1)) */
 275         if (!EVP_MAC_final(ctx_Ai, Ai, &Ai_len, sizeof(Ai)))
 276             goto err;
 277         EVP_MAC_CTX_free(ctx_Ai);
 278         ctx_Ai = NULL;
 279
 280         /* calc next chunk: HMAC_<hash>(secret, A(i) + seed) */
 281         ctx = EVP_MAC_CTX_dup(ctx_init);
 282         if (ctx == NULL)
 283             goto err;
 284         if (!EVP_MAC_update(ctx, Ai, Ai_len))
 285             goto err;
 286         /* save state for calculating next A(i) value */
 287         if (olen > chunk) {
 288             ctx_Ai = EVP_MAC_CTX_dup(ctx);
 289             if (ctx_Ai == NULL)
 290                 goto err;
 291         }
 292         if (seed != NULL && !EVP_MAC_update(ctx, seed, seed_len))
 293             goto err;
 294         if (olen <= chunk) {
 295             /* last chunk - use Ai as temp bounce buffer */
 296             if (!EVP_MAC_final(ctx, Ai, &Ai_len, sizeof(Ai)))
 297                 goto err;
 298             memcpy(out, Ai, olen);
 299             break;
 300         }
 301         if (!EVP_MAC_final(ctx, out, NULL, olen))
 302             goto err;
 303         EVP_MAC_CTX_free(ctx);
 304         ctx = NULL;
 305         out += chunk;
 306         olen -= chunk;
 307     }
 308     ret = 1;
 309  err:
 310     EVP_MAC_CTX_free(ctx);
 311     EVP_MAC_CTX_free(ctx_Ai);
 312     EVP_MAC_CTX_free(ctx_init);
 313     EVP_MAC_free(mac);
 314     OPENSSL_cleanse(Ai, sizeof(Ai));
 315     return ret;
 316 }
 317
 318 /*
 319  * Refer to "The TLS Protocol Version 1.0" Section 5
 320  * (https://tools.ietf.org/html/rfc2246#section-5) and
 321  * "The Transport Layer Security (TLS) Protocol Version 1.2" Section 5
 322  * (https://tools.ietf.org/html/rfc5246#section-5).
 323  *
 324  * For TLS v1.0 and TLS v1.1:
 325  *
 326  *   PRF(secret, label, seed) = P_MD5(S1, label + seed) XOR
 327  *                              P_SHA-1(S2, label + seed)
 328  *
 329  * S1 is taken from the first half of the secret, S2 from the second half.
 330  *
 331  *   L_S = length in bytes of secret;
 332  *   L_S1 = L_S2 = ceil(L_S / 2);
 333  *
 334  * For TLS v1.2:
 335  *
 336  *   PRF(secret, label, seed) = P_<hash>(secret, label + seed)
 337  */
 338 static int tls1_prf_alg(const EVP_MD *md,
 339                         const unsigned char *sec, size_t slen,
 340                         const unsigned char *seed, size_t seed_len,
 341                         unsigned char *out, size_t olen)
 342 {
 343     if (EVP_MD_type(md) == NID_md5_sha1) {
 344         /* TLS v1.0 and TLS v1.1 */
 345         size_t i;
 346         unsigned char *tmp;
 347         /* calc: L_S1 = L_S2 = ceil(L_S / 2) */
 348         size_t L_S1 = (slen + 1) / 2;
 349         size_t L_S2 = L_S1;
 350
 351         if (!tls1_prf_P_hash(EVP_md5(), sec, L_S1,
 352                              seed, seed_len, out, olen))
 353             return 0;
 354
 355         if ((tmp = OPENSSL_malloc(olen)) == NULL) {
 356             KDFerr(KDF_F_TLS1_PRF_ALG, ERR_R_MALLOC_FAILURE);
 357             return 0;
 358         }
 359         if (!tls1_prf_P_hash(EVP_sha1(), sec + slen - L_S2, L_S2,
 360                              seed, seed_len, tmp, olen)) {
 361             OPENSSL_clear_free(tmp, olen);
 362             return 0;
 363         }
 364         for (i = 0; i < olen; i++)
 365             out[i] ^= tmp[i];
 366         OPENSSL_clear_free(tmp, olen);
 367         return 1;
 368     }
 369
 370     /* TLS v1.2 */
 371     if (!tls1_prf_P_hash(md, sec, slen, seed, seed_len, out, olen))
 372         return 0;
 373
 374     return 1;
 375 }