crypto/kdf/sskdf.c

   1 /*
   2  * Copyright 2019 The OpenSSL Project Authors. All Rights Reserved.
   3  * Copyright (c) 2019, Oracle and/or its affiliates.  All rights reserved.
   4  *
   5  * Licensed under the Apache License 2.0 (the "License").  You may not use
   6  * this file except in compliance with the License.  You can obtain a copy
   7  * in the file LICENSE in the source distribution or at
   8  * https://www.openssl.org/source/license.html
   9  */
  10
  11 /*
  12  * Refer to https://csrc.nist.gov/publications/detail/sp/800-56c/rev-1/final
  13  * Section 4.1.
  14  *
  15  * The Single Step KDF algorithm is given by:
  16  *
  17  * Result(0) = empty bit string (i.e., the null string).
  18  * For i = 1 to reps, do the following:
  19  *   Increment counter by 1.
  20  *   Result(i) = Result(i - 1) || H(counter || Z || FixedInfo).
  21  * DKM = LeftmostBits(Result(reps), L))
  22  *
  23  * NOTES:
  24  *   Z is a shared secret required to produce the derived key material.
  25  *   counter is a 4 byte buffer.
  26  *   FixedInfo is a bit string containing context specific data.
  27  *   DKM is the output derived key material.
  28  *   L is the required size of the DKM.
  29  *   reps = [L / H_outputBits]
  30  *   H(x) is the auxiliary function that can be either a hash, HMAC or KMAC.
  31  *   H_outputBits is the length of the output of the auxiliary function H(x).
  32  *
  33  * Currently there is not a comprehensive list of test vectors for this
  34  * algorithm, especially for H(x) = HMAC and H(x) = KMAC.
  35  * Test vectors for H(x) = Hash are indirectly used by CAVS KAS tests.
  36  */
  37 #include <stdlib.h>
  38 #include <stdarg.h>
  39 #include <string.h>
  40 #include <openssl/hmac.h>
  41 #include <openssl/evp.h>
  42 #include <openssl/kdf.h>
  43 #include <openssl/core_names.h>
  44 #include <openssl/params.h>
  45 #include "internal/cryptlib.h"
  46 #include "internal/evp_int.h"
  47 #include "kdf_local.h"
  48
  49 struct evp_kdf_impl_st {
  50     EVP_MAC *mac;       /* H(x) = HMAC_hash OR H(x) = KMAC */
  51     const EVP_MD *md;   /* H(x) = hash OR when H(x) = HMAC_hash */
  52     unsigned char *secret;
  53     size_t secret_len;
  54     unsigned char *info;
  55     size_t info_len;
  56     unsigned char *salt;
  57     size_t salt_len;
  58     size_t out_len; /* optional KMAC parameter */
  59 };
  60
  61 #define SSKDF_MAX_INLEN (1<<30)
  62 #define SSKDF_KMAC128_DEFAULT_SALT_SIZE (168 - 4)
  63 #define SSKDF_KMAC256_DEFAULT_SALT_SIZE (136 - 4)
  64
  65 /* KMAC uses a Customisation string of 'KDF' */
  66 static const unsigned char kmac_custom_str[] = { 0x4B, 0x44, 0x46 };
  67
  68 /*
  69  * Refer to https://csrc.nist.gov/publications/detail/sp/800-56c/rev-1/final
  70  * Section 4. One-Step Key Derivation using H(x) = hash(x)
  71  * Note: X9.63 also uses this code with the only difference being that the
  72  * counter is appended to the secret 'z'.
  73  * i.e.
  74  *   result[i] = Hash(counter || z || info) for One Step OR
  75  *   result[i] = Hash(z || counter || info) for X9.63.
  76  */
  77 static int SSKDF_hash_kdm(const EVP_MD *kdf_md,
  78                           const unsigned char *z, size_t z_len,
  79                           const unsigned char *info, size_t info_len,
  80                           unsigned int append_ctr,
  81                           unsigned char *derived_key, size_t derived_key_len)
  82 {
  83     int ret = 0, hlen;
  84     size_t counter, out_len, len = derived_key_len;
  85     unsigned char c[4];
  86     unsigned char mac[EVP_MAX_MD_SIZE];
  87     unsigned char *out = derived_key;
  88     EVP_MD_CTX *ctx = NULL, *ctx_init = NULL;
  89
  90     if (z_len > SSKDF_MAX_INLEN || info_len > SSKDF_MAX_INLEN
  91             || derived_key_len > SSKDF_MAX_INLEN
  92             || derived_key_len == 0)
  93         return 0;
  94
  95     hlen = EVP_MD_size(kdf_md);
  96     if (hlen <= 0)
  97         return 0;
  98     out_len = (size_t)hlen;
  99
 100     ctx = EVP_MD_CTX_create();
 101     ctx_init = EVP_MD_CTX_create();
 102     if (ctx == NULL || ctx_init == NULL)
 103         goto end;
 104
 105     if (!EVP_DigestInit(ctx_init, kdf_md))
 106         goto end;
 107
 108     for (counter = 1;; counter++) {
 109         c[0] = (unsigned char)((counter >> 24) & 0xff);
 110         c[1] = (unsigned char)((counter >> 16) & 0xff);
 111         c[2] = (unsigned char)((counter >> 8) & 0xff);
 112         c[3] = (unsigned char)(counter & 0xff);
 113
 114         if (!(EVP_MD_CTX_copy_ex(ctx, ctx_init)
 115                 && (append_ctr || EVP_DigestUpdate(ctx, c, sizeof(c)))
 116                 && EVP_DigestUpdate(ctx, z, z_len)
 117                 && (!append_ctr || EVP_DigestUpdate(ctx, c, sizeof(c)))
 118                 && EVP_DigestUpdate(ctx, info, info_len)))
 119             goto end;
 120         if (len >= out_len) {
 121             if (!EVP_DigestFinal_ex(ctx, out, NULL))
 122                 goto end;
 123             out += out_len;
 124             len -= out_len;
 125             if (len == 0)
 126                 break;
 127         } else {
 128             if (!EVP_DigestFinal_ex(ctx, mac, NULL))
 129                 goto end;
 130             memcpy(out, mac, len);
 131             break;
 132         }
 133     }
 134     ret = 1;
 135 end:
 136     EVP_MD_CTX_destroy(ctx);
 137     EVP_MD_CTX_destroy(ctx_init);
 138     OPENSSL_cleanse(mac, sizeof(mac));
 139     return ret;
 140 }
 141
 142 static int kmac_init(EVP_MAC_CTX *ctx, const unsigned char *custom,
 143                      size_t custom_len, size_t kmac_out_len,
 144                      size_t derived_key_len, unsigned char **out)
 145 {
 146     OSSL_PARAM params[2];
 147
 148     /* Only KMAC has custom data - so return if not KMAC */
 149     if (custom == NULL)
 150         return 1;
 151
 152     params[0] = OSSL_PARAM_construct_octet_string(OSSL_MAC_PARAM_CUSTOM,
 153                                                   (void *)custom, custom_len);
 154     params[1] = OSSL_PARAM_construct_end();
 155
 156     if (!EVP_MAC_CTX_set_params(ctx, params))
 157         return 0;
 158
 159     /* By default only do one iteration if kmac_out_len is not specified */
 160     if (kmac_out_len == 0)
 161         kmac_out_len = derived_key_len;
 162     /* otherwise check the size is valid */
 163     else if (!(kmac_out_len == derived_key_len
 164             || kmac_out_len == 20
 165             || kmac_out_len == 28
 166             || kmac_out_len == 32
 167             || kmac_out_len == 48
 168             || kmac_out_len == 64))
 169         return 0;
 170
 171     params[0] = OSSL_PARAM_construct_size_t(OSSL_MAC_PARAM_SIZE,
 172                                             &kmac_out_len);
 173
 174     if (EVP_MAC_CTX_set_params(ctx, params) <= 0)
 175         return 0;
 176
 177     /*
 178      * For kmac the output buffer can be larger than EVP_MAX_MD_SIZE: so
 179      * alloc a buffer for this case.
 180      */
 181     if (kmac_out_len > EVP_MAX_MD_SIZE) {
 182         *out = OPENSSL_zalloc(kmac_out_len);
 183         if (*out == NULL)
 184             return 0;
 185     }
 186     return 1;
 187 }
 188
 189 /*
 190  * Refer to https://csrc.nist.gov/publications/detail/sp/800-56c/rev-1/final
 191  * Section 4. One-Step Key Derivation using MAC: i.e either
 192  *     H(x) = HMAC-hash(salt, x) OR
 193  *     H(x) = KMAC#(salt, x, outbits, CustomString='KDF')
 194  */
 195 static int SSKDF_mac_kdm(EVP_MAC *kdf_mac, const EVP_MD *hmac_md,
 196                          const unsigned char *kmac_custom,
 197                          size_t kmac_custom_len, size_t kmac_out_len,
 198                          const unsigned char *salt, size_t salt_len,
 199                          const unsigned char *z, size_t z_len,
 200                          const unsigned char *info, size_t info_len,
 201                          unsigned char *derived_key, size_t derived_key_len)
 202 {
 203     int ret = 0;
 204     size_t counter, out_len, len;
 205     unsigned char c[4];
 206     unsigned char mac_buf[EVP_MAX_MD_SIZE];
 207     unsigned char *out = derived_key;
 208     EVP_MAC_CTX *ctx = NULL, *ctx_init = NULL;
 209     unsigned char *mac = mac_buf, *kmac_buffer = NULL;
 210     OSSL_PARAM params[3];
 211     size_t params_n = 0;
 212
 213     if (z_len > SSKDF_MAX_INLEN || info_len > SSKDF_MAX_INLEN
 214             || derived_key_len > SSKDF_MAX_INLEN
 215             || derived_key_len == 0)
 216         return 0;
 217
 218     ctx_init = EVP_MAC_CTX_new(kdf_mac);
 219     if (ctx_init == NULL)
 220         goto end;
 221
 222     if (hmac_md != NULL) {
 223         const char *mdname = EVP_MD_name(hmac_md);
 224         params[params_n++] =
 225             OSSL_PARAM_construct_utf8_string(OSSL_MAC_PARAM_DIGEST,
 226                                              (char *)mdname, 0);
 227     }
 228     params[params_n++] =
 229         OSSL_PARAM_construct_octet_string(OSSL_MAC_PARAM_KEY, (void *)salt,
 230                                           salt_len);
 231     params[params_n] = OSSL_PARAM_construct_end();
 232
 233     if (!EVP_MAC_CTX_set_params(ctx_init, params))
 234         goto end;
 235
 236     if (!kmac_init(ctx_init, kmac_custom, kmac_custom_len, kmac_out_len,
 237                    derived_key_len, &kmac_buffer))
 238         goto end;
 239     if (kmac_buffer != NULL)
 240         mac = kmac_buffer;
 241
 242     if (!EVP_MAC_init(ctx_init))
 243         goto end;
 244
 245     out_len = EVP_MAC_size(ctx_init); /* output size */
 246     if (out_len <= 0)
 247         goto end;
 248     len = derived_key_len;
 249
 250     for (counter = 1;; counter++) {
 251         c[0] = (unsigned char)((counter >> 24) & 0xff);
 252         c[1] = (unsigned char)((counter >> 16) & 0xff);
 253         c[2] = (unsigned char)((counter >> 8) & 0xff);
 254         c[3] = (unsigned char)(counter & 0xff);
 255
 256         ctx = EVP_MAC_CTX_dup(ctx_init);
 257         if (!(ctx != NULL
 258                 && EVP_MAC_update(ctx, c, sizeof(c))
 259                 && EVP_MAC_update(ctx, z, z_len)
 260                 && EVP_MAC_update(ctx, info, info_len)))
 261             goto end;
 262         if (len >= out_len) {
 263             if (!EVP_MAC_final(ctx, out, NULL, len))
 264                 goto end;
 265             out += out_len;
 266             len -= out_len;
 267             if (len == 0)
 268                 break;
 269         } else {
 270             if (!EVP_MAC_final(ctx, mac, NULL, len))
 271                 goto end;
 272             memcpy(out, mac, len);
 273             break;
 274         }
 275         EVP_MAC_CTX_free(ctx);
 276         ctx = NULL;
 277     }
 278     ret = 1;
 279 end:
 280     if (kmac_buffer != NULL)
 281         OPENSSL_clear_free(kmac_buffer, kmac_out_len);
 282     else
 283         OPENSSL_cleanse(mac_buf, sizeof(mac_buf));
 284
 285     EVP_MAC_CTX_free(ctx);
 286     EVP_MAC_CTX_free(ctx_init);
 287     return ret;
 288 }
 289
 290 static EVP_KDF_IMPL *sskdf_new(void)
 291 {
 292     EVP_KDF_IMPL *impl;
 293
 294     if ((impl = OPENSSL_zalloc(sizeof(*impl))) == NULL)
 295         KDFerr(KDF_F_SSKDF_NEW, ERR_R_MALLOC_FAILURE);
 296     return impl;
 297 }
 298
 299 static void sskdf_reset(EVP_KDF_IMPL *impl)
 300 {
 301     OPENSSL_clear_free(impl->secret, impl->secret_len);
 302     OPENSSL_clear_free(impl->info, impl->info_len);
 303     OPENSSL_clear_free(impl->salt, impl->salt_len);
 304     EVP_MAC_free(impl->mac);
 305 #if 0                    /* TODO(3.0) When we switch to fetched MDs */
 306     EVP_MD_meth_free(impl->md);
 307 #endif
 308     memset(impl, 0, sizeof(*impl));
 309 }
 310
 311 static void sskdf_free(EVP_KDF_IMPL *impl)
 312 {
 313     sskdf_reset(impl);
 314     OPENSSL_free(impl);
 315 }
 316
 317 static int sskdf_set_buffer(va_list args, unsigned char **out, size_t *out_len)
 318 {
 319     const unsigned char *p;
 320     size_t len;
 321
 322     p = va_arg(args, const unsigned char *);
 323     len = va_arg(args, size_t);
 324     if (len == 0 || p == NULL)
 325         return 1;
 326
 327     OPENSSL_free(*out);
 328     *out = OPENSSL_memdup(p, len);
 329     if (*out == NULL)
 330         return 0;
 331
 332     *out_len = len;
 333     return 1;
 334 }
 335
 336 static int sskdf_ctrl(EVP_KDF_IMPL *impl, int cmd, va_list args)
 337 {
 338     const EVP_MD *md;
 339
 340     switch (cmd) {
 341     case EVP_KDF_CTRL_SET_KEY:
 342         return sskdf_set_buffer(args, &impl->secret, &impl->secret_len);
 343
 344     case EVP_KDF_CTRL_SET_SSKDF_INFO:
 345         return sskdf_set_buffer(args, &impl->info, &impl->info_len);
 346
 347     case EVP_KDF_CTRL_SET_MD:
 348         md = va_arg(args, const EVP_MD *);
 349         if (md == NULL)
 350             return 0;
 351
 352 #if 0                    /* TODO(3.0) When we switch to fetched MDs */
 353         EVP_MD_meth_free(impl->md);
 354 #endif
 355         impl->md = md;
 356         return 1;
 357
 358     case EVP_KDF_CTRL_SET_MAC:
 359         {
 360             const char *name;
 361             EVP_MAC *mac;
 362
 363             name = va_arg(args, const char *);
 364             if (name == NULL)
 365                 return 0;
 366
 367             EVP_MAC_free(impl->mac);
 368             impl->mac = NULL;
 369
 370             /*
 371              * TODO(3.0) add support for OPENSSL_CTX and properties in KDFs
 372              */
 373             mac = EVP_MAC_fetch(NULL, name, NULL);
 374             if (mac == NULL)
 375                 return 0;
 376
 377             impl->mac = mac;
 378             return 1;
 379         }
 380     case EVP_KDF_CTRL_SET_SALT:
 381         return sskdf_set_buffer(args, &impl->salt, &impl->salt_len);
 382
 383     case EVP_KDF_CTRL_SET_MAC_SIZE:
 384         impl->out_len = va_arg(args, size_t);
 385         return 1;
 386
 387     default:
 388         return -2;
 389     }
 390 }
 391
 392 static int sskdf_ctrl_str(EVP_KDF_IMPL *impl, const char *type,
 393                           const char *value)
 394 {
 395     if (strcmp(type, "secret") == 0 || strcmp(type, "key") == 0)
 396          return kdf_str2ctrl(impl, sskdf_ctrl, EVP_KDF_CTRL_SET_KEY,
 397                              value);
 398
 399     if (strcmp(type, "hexsecret") == 0 || strcmp(type, "hexkey") == 0)
 400         return kdf_hex2ctrl(impl, sskdf_ctrl, EVP_KDF_CTRL_SET_KEY,
 401                             value);
 402
 403     if (strcmp(type, "info") == 0)
 404         return kdf_str2ctrl(impl, sskdf_ctrl, EVP_KDF_CTRL_SET_SSKDF_INFO,
 405                             value);
 406
 407     if (strcmp(type, "hexinfo") == 0)
 408         return kdf_hex2ctrl(impl, sskdf_ctrl, EVP_KDF_CTRL_SET_SSKDF_INFO,
 409                             value);
 410
 411     if (strcmp(type, "digest") == 0)
 412         return kdf_md2ctrl(impl, sskdf_ctrl, EVP_KDF_CTRL_SET_MD, value);
 413
 414     if (strcmp(type, "mac") == 0)
 415         return kdf_str2ctrl(impl, sskdf_ctrl, EVP_KDF_CTRL_SET_MAC, value);
 416
 417     if (strcmp(type, "salt") == 0)
 418         return kdf_str2ctrl(impl, sskdf_ctrl, EVP_KDF_CTRL_SET_SALT, value);
 419
 420     if (strcmp(type, "hexsalt") == 0)
 421         return kdf_hex2ctrl(impl, sskdf_ctrl, EVP_KDF_CTRL_SET_SALT, value);
 422
 423
 424     if (strcmp(type, "maclen") == 0) {
 425         int val = atoi(value);
 426         if (val < 0) {
 427             KDFerr(KDF_F_SSKDF_CTRL_STR, KDF_R_VALUE_ERROR);
 428             return 0;
 429         }
 430         return call_ctrl(sskdf_ctrl, impl, EVP_KDF_CTRL_SET_MAC_SIZE,
 431                          (size_t)val);
 432     }
 433     return -2;
 434 }
 435
 436 static size_t sskdf_size(EVP_KDF_IMPL *impl)
 437 {
 438     int len;
 439
 440     if (impl->md == NULL) {
 441         KDFerr(KDF_F_SSKDF_SIZE, KDF_R_MISSING_MESSAGE_DIGEST);
 442         return 0;
 443     }
 444     len = EVP_MD_size(impl->md);
 445     return (len <= 0) ? 0 : (size_t)len;
 446 }
 447
 448 static int sskdf_derive(EVP_KDF_IMPL *impl, unsigned char *key, size_t keylen)
 449 {
 450     if (impl->secret == NULL) {
 451         KDFerr(KDF_F_SSKDF_DERIVE, KDF_R_MISSING_SECRET);
 452         return 0;
 453     }
 454
 455     if (impl->mac != NULL) {
 456         /* H(x) = KMAC or H(x) = HMAC */
 457         int ret;
 458         const unsigned char *custom = NULL;
 459         size_t custom_len = 0;
 460         const char *macname;
 461         int default_salt_len;
 462
 463         /*
 464          * TODO(3.0) investigate the necessity to have all these controls.
 465          * Why does KMAC require a salt length that's shorter than the MD
 466          * block size?
 467          */
 468         macname = EVP_MAC_name(impl->mac);
 469         if (strcmp(macname, OSSL_MAC_NAME_HMAC) == 0) {
 470             /* H(x) = HMAC(x, salt, hash) */
 471             if (impl->md == NULL) {
 472                 KDFerr(KDF_F_SSKDF_DERIVE, KDF_R_MISSING_MESSAGE_DIGEST);
 473                 return 0;
 474             }
 475             default_salt_len = EVP_MD_block_size(impl->md);
 476             if (default_salt_len <= 0)
 477                 return 0;
 478         } else if (strcmp(macname, OSSL_MAC_NAME_KMAC128) == 0
 479                    || strcmp(macname, OSSL_MAC_NAME_KMAC256) == 0) {
 480             /* H(x) = KMACzzz(x, salt, custom) */
 481             custom = kmac_custom_str;
 482             custom_len = sizeof(kmac_custom_str);
 483             if (strcmp(macname, OSSL_MAC_NAME_KMAC128) == 0)
 484                 default_salt_len = SSKDF_KMAC128_DEFAULT_SALT_SIZE;
 485             else
 486                 default_salt_len = SSKDF_KMAC256_DEFAULT_SALT_SIZE;
 487         } else {
 488             KDFerr(KDF_F_SSKDF_DERIVE, KDF_R_UNSUPPORTED_MAC_TYPE);
 489             return 0;
 490         }
 491         /* If no salt is set then use a default_salt of zeros */
 492         if (impl->salt == NULL || impl->salt_len <= 0) {
 493             impl->salt = OPENSSL_zalloc(default_salt_len);
 494             if (impl->salt == NULL) {
 495                 KDFerr(KDF_F_SSKDF_DERIVE, ERR_R_MALLOC_FAILURE);
 496                 return 0;
 497             }
 498             impl->salt_len = default_salt_len;
 499         }
 500         ret = SSKDF_mac_kdm(impl->mac, impl->md,
 501                             custom, custom_len, impl->out_len,
 502                             impl->salt, impl->salt_len,
 503                             impl->secret, impl->secret_len,
 504                             impl->info, impl->info_len, key, keylen);
 505         return ret;
 506     } else {
 507         /* H(x) = hash */
 508         if (impl->md == NULL) {
 509             KDFerr(KDF_F_SSKDF_DERIVE, KDF_R_MISSING_MESSAGE_DIGEST);
 510             return 0;
 511         }
 512         return SSKDF_hash_kdm(impl->md, impl->secret, impl->secret_len,
 513                               impl->info, impl->info_len, 0, key, keylen);
 514     }
 515 }
 516
 517 static int x963kdf_derive(EVP_KDF_IMPL *impl, unsigned char *key, size_t keylen)
 518 {
 519     if (impl->secret == NULL) {
 520         KDFerr(KDF_F_X963KDF_DERIVE, KDF_R_MISSING_SECRET);
 521         return 0;
 522     }
 523
 524     if (impl->mac != NULL) {
 525         KDFerr(KDF_F_X963KDF_DERIVE, KDF_R_NOT_SUPPORTED);
 526         return 0;
 527     } else {
 528         /* H(x) = hash */
 529         if (impl->md == NULL) {
 530             KDFerr(KDF_F_X963KDF_DERIVE, KDF_R_MISSING_MESSAGE_DIGEST);
 531             return 0;
 532         }
 533         return SSKDF_hash_kdm(impl->md, impl->secret, impl->secret_len,
 534                               impl->info, impl->info_len, 1, key, keylen);
 535     }
 536 }
 537
 538 const EVP_KDF ss_kdf_meth = {
 539     EVP_KDF_SS,
 540     sskdf_new,
 541     sskdf_free,
 542     sskdf_reset,
 543     sskdf_ctrl,
 544     sskdf_ctrl_str,
 545     sskdf_size,
 546     sskdf_derive
 547 };
 548
 549 const EVP_KDF x963_kdf_meth = {
 550     EVP_KDF_X963,
 551     sskdf_new,
 552     sskdf_free,
 553     sskdf_reset,
 554     sskdf_ctrl,
 555     sskdf_ctrl_str,
 556     sskdf_size,
 557     x963kdf_derive
 558 };