providers/implementations/kdfs/hkdf.c

   1 /*
   2  * Copyright 2016-2021 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  * HMAC low level APIs are deprecated for public use, but still ok for internal
  12  * use.
  13  */
  14 #include "internal/deprecated.h"
  15
  16 #include <stdlib.h>
  17 #include <stdarg.h>
  18 #include <string.h>
  19 #include <openssl/hmac.h>
  20 #include <openssl/evp.h>
  21 #include <openssl/kdf.h>
  22 #include <openssl/core_names.h>
  23 #include <openssl/proverr.h>
  24 #include "internal/cryptlib.h"
  25 #include "internal/numbers.h"
  26 #include "crypto/evp.h"
  27 #include "prov/provider_ctx.h"
  28 #include "prov/providercommon.h"
  29 #include "prov/implementations.h"
  30 #include "prov/provider_util.h"
  31 #include "e_os.h"
  32
  33 #define HKDF_MAXBUF 2048
  34
  35 static OSSL_FUNC_kdf_newctx_fn kdf_hkdf_new;
  36 static OSSL_FUNC_kdf_freectx_fn kdf_hkdf_free;
  37 static OSSL_FUNC_kdf_reset_fn kdf_hkdf_reset;
  38 static OSSL_FUNC_kdf_derive_fn kdf_hkdf_derive;
  39 static OSSL_FUNC_kdf_settable_ctx_params_fn kdf_hkdf_settable_ctx_params;
  40 static OSSL_FUNC_kdf_set_ctx_params_fn kdf_hkdf_set_ctx_params;
  41 static OSSL_FUNC_kdf_gettable_ctx_params_fn kdf_hkdf_gettable_ctx_params;
  42 static OSSL_FUNC_kdf_get_ctx_params_fn kdf_hkdf_get_ctx_params;
  43
  44 static int HKDF(OSSL_LIB_CTX *libctx, const EVP_MD *evp_md,
  45                 const unsigned char *salt, size_t salt_len,
  46                 const unsigned char *key, size_t key_len,
  47                 const unsigned char *info, size_t info_len,
  48                 unsigned char *okm, size_t okm_len);
  49 static int HKDF_Extract(OSSL_LIB_CTX *libctx, const EVP_MD *evp_md,
  50                         const unsigned char *salt, size_t salt_len,
  51                         const unsigned char *ikm, size_t ikm_len,
  52                         unsigned char *prk, size_t prk_len);
  53 static int HKDF_Expand(const EVP_MD *evp_md,
  54                        const unsigned char *prk, size_t prk_len,
  55                        const unsigned char *info, size_t info_len,
  56                        unsigned char *okm, size_t okm_len);
  57
  58 typedef struct {
  59     void *provctx;
  60     int mode;
  61     PROV_DIGEST digest;
  62     unsigned char *salt;
  63     size_t salt_len;
  64     unsigned char *key;
  65     size_t key_len;
  66     unsigned char info[HKDF_MAXBUF];
  67     size_t info_len;
  68 } KDF_HKDF;
  69
  70 static void *kdf_hkdf_new(void *provctx)
  71 {
  72     KDF_HKDF *ctx;
  73
  74     if (!ossl_prov_is_running())
  75         return NULL;
  76
  77     if ((ctx = OPENSSL_zalloc(sizeof(*ctx))) == NULL)
  78         ERR_raise(ERR_LIB_PROV, ERR_R_MALLOC_FAILURE);
  79     else
  80         ctx->provctx = provctx;
  81     return ctx;
  82 }
  83
  84 static void kdf_hkdf_free(void *vctx)
  85 {
  86     KDF_HKDF *ctx = (KDF_HKDF *)vctx;
  87
  88     if (ctx != NULL) {
  89         kdf_hkdf_reset(ctx);
  90         OPENSSL_free(ctx);
  91     }
  92 }
  93
  94 static void kdf_hkdf_reset(void *vctx)
  95 {
  96     KDF_HKDF *ctx = (KDF_HKDF *)vctx;
  97     void *provctx = ctx->provctx;
  98
  99     ossl_prov_digest_reset(&ctx->digest);
 100     OPENSSL_free(ctx->salt);
 101     OPENSSL_clear_free(ctx->key, ctx->key_len);
 102     OPENSSL_cleanse(ctx->info, ctx->info_len);
 103     memset(ctx, 0, sizeof(*ctx));
 104     ctx->provctx = provctx;
 105 }
 106
 107 static size_t kdf_hkdf_size(KDF_HKDF *ctx)
 108 {
 109     int sz;
 110     const EVP_MD *md = ossl_prov_digest_md(&ctx->digest);
 111
 112     if (ctx->mode != EVP_KDF_HKDF_MODE_EXTRACT_ONLY)
 113         return SIZE_MAX;
 114
 115     if (md == NULL) {
 116         ERR_raise(ERR_LIB_PROV, PROV_R_MISSING_MESSAGE_DIGEST);
 117         return 0;
 118     }
 119     sz = EVP_MD_get_size(md);
 120     if (sz < 0)
 121         return 0;
 122
 123     return sz;
 124 }
 125
 126 static int kdf_hkdf_derive(void *vctx, unsigned char *key, size_t keylen,
 127                            const OSSL_PARAM params[])
 128 {
 129     KDF_HKDF *ctx = (KDF_HKDF *)vctx;
 130     OSSL_LIB_CTX *libctx = PROV_LIBCTX_OF(ctx->provctx);
 131     const EVP_MD *md;
 132
 133     if (!ossl_prov_is_running() || !kdf_hkdf_set_ctx_params(ctx, params))
 134         return 0;
 135
 136     md = ossl_prov_digest_md(&ctx->digest);
 137     if (md == NULL) {
 138         ERR_raise(ERR_LIB_PROV, PROV_R_MISSING_MESSAGE_DIGEST);
 139         return 0;
 140     }
 141     if (ctx->key == NULL) {
 142         ERR_raise(ERR_LIB_PROV, PROV_R_MISSING_KEY);
 143         return 0;
 144     }
 145     if (keylen == 0) {
 146         ERR_raise(ERR_LIB_PROV, PROV_R_INVALID_KEY_LENGTH);
 147         return 0;
 148     }
 149
 150     switch (ctx->mode) {
 151     case EVP_KDF_HKDF_MODE_EXTRACT_AND_EXPAND:
 152         return HKDF(libctx, md, ctx->salt, ctx->salt_len,
 153                     ctx->key, ctx->key_len, ctx->info, ctx->info_len, key, keylen);
 154
 155     case EVP_KDF_HKDF_MODE_EXTRACT_ONLY:
 156         return HKDF_Extract(libctx, md, ctx->salt, ctx->salt_len,
 157                             ctx->key, ctx->key_len, key, keylen);
 158
 159     case EVP_KDF_HKDF_MODE_EXPAND_ONLY:
 160         return HKDF_Expand(md, ctx->key, ctx->key_len, ctx->info,
 161                            ctx->info_len, key, keylen);
 162
 163     default:
 164         return 0;
 165     }
 166 }
 167
 168 static int kdf_hkdf_set_ctx_params(void *vctx, const OSSL_PARAM params[])
 169 {
 170     const OSSL_PARAM *p;
 171     KDF_HKDF *ctx = vctx;
 172     OSSL_LIB_CTX *libctx = PROV_LIBCTX_OF(ctx->provctx);
 173     int n;
 174
 175     if (params == NULL)
 176         return 1;
 177
 178     if (!ossl_prov_digest_load_from_params(&ctx->digest, params, libctx))
 179         return 0;
 180
 181     if ((p = OSSL_PARAM_locate_const(params, OSSL_KDF_PARAM_MODE)) != NULL) {
 182         if (p->data_type == OSSL_PARAM_UTF8_STRING) {
 183             if (strcasecmp(p->data, "EXTRACT_AND_EXPAND") == 0) {
 184                 ctx->mode = EVP_KDF_HKDF_MODE_EXTRACT_AND_EXPAND;
 185             } else if (strcasecmp(p->data, "EXTRACT_ONLY") == 0) {
 186                 ctx->mode = EVP_KDF_HKDF_MODE_EXTRACT_ONLY;
 187             } else if (strcasecmp(p->data, "EXPAND_ONLY") == 0) {
 188                 ctx->mode = EVP_KDF_HKDF_MODE_EXPAND_ONLY;
 189             } else {
 190                 ERR_raise(ERR_LIB_PROV, PROV_R_INVALID_MODE);
 191                 return 0;
 192             }
 193         } else if (OSSL_PARAM_get_int(p, &n)) {
 194             if (n != EVP_KDF_HKDF_MODE_EXTRACT_AND_EXPAND
 195                 && n != EVP_KDF_HKDF_MODE_EXTRACT_ONLY
 196                 && n != EVP_KDF_HKDF_MODE_EXPAND_ONLY) {
 197                 ERR_raise(ERR_LIB_PROV, PROV_R_INVALID_MODE);
 198                 return 0;
 199             }
 200             ctx->mode = n;
 201         } else {
 202             ERR_raise(ERR_LIB_PROV, PROV_R_INVALID_MODE);
 203             return 0;
 204         }
 205     }
 206
 207     if ((p = OSSL_PARAM_locate_const(params, OSSL_KDF_PARAM_KEY)) != NULL) {
 208         OPENSSL_clear_free(ctx->key, ctx->key_len);
 209         ctx->key = NULL;
 210         if (!OSSL_PARAM_get_octet_string(p, (void **)&ctx->key, 0,
 211                                          &ctx->key_len))
 212             return 0;
 213     }
 214
 215     if ((p = OSSL_PARAM_locate_const(params, OSSL_KDF_PARAM_SALT)) != NULL) {
 216         if (p->data_size != 0 && p->data != NULL) {
 217             OPENSSL_free(ctx->salt);
 218             ctx->salt = NULL;
 219             if (!OSSL_PARAM_get_octet_string(p, (void **)&ctx->salt, 0,
 220                                              &ctx->salt_len))
 221                 return 0;
 222         }
 223     }
 224     /* The info fields concatenate, so process them all */
 225     if ((p = OSSL_PARAM_locate_const(params, OSSL_KDF_PARAM_INFO)) != NULL) {
 226         ctx->info_len = 0;
 227         for (; p != NULL; p = OSSL_PARAM_locate_const(p + 1,
 228                                                       OSSL_KDF_PARAM_INFO)) {
 229             const void *q = ctx->info + ctx->info_len;
 230             size_t sz = 0;
 231
 232             if (p->data_size != 0
 233                 && p->data != NULL
 234                 && !OSSL_PARAM_get_octet_string(p, (void **)&q,
 235                                                 HKDF_MAXBUF - ctx->info_len,
 236                                                 &sz))
 237                 return 0;
 238             ctx->info_len += sz;
 239         }
 240     }
 241     return 1;
 242 }
 243
 244 static const OSSL_PARAM *kdf_hkdf_settable_ctx_params(ossl_unused void *ctx,
 245                                                       ossl_unused void *provctx)
 246 {
 247     static const OSSL_PARAM known_settable_ctx_params[] = {
 248         OSSL_PARAM_utf8_string(OSSL_KDF_PARAM_MODE, NULL, 0),
 249         OSSL_PARAM_int(OSSL_KDF_PARAM_MODE, NULL),
 250         OSSL_PARAM_utf8_string(OSSL_KDF_PARAM_PROPERTIES, NULL, 0),
 251         OSSL_PARAM_utf8_string(OSSL_KDF_PARAM_DIGEST, NULL, 0),
 252         OSSL_PARAM_octet_string(OSSL_KDF_PARAM_SALT, NULL, 0),
 253         OSSL_PARAM_octet_string(OSSL_KDF_PARAM_KEY, NULL, 0),
 254         OSSL_PARAM_octet_string(OSSL_KDF_PARAM_INFO, NULL, 0),
 255         OSSL_PARAM_END
 256     };
 257     return known_settable_ctx_params;
 258 }
 259
 260 static int kdf_hkdf_get_ctx_params(void *vctx, OSSL_PARAM params[])
 261 {
 262     KDF_HKDF *ctx = (KDF_HKDF *)vctx;
 263     OSSL_PARAM *p;
 264
 265     if ((p = OSSL_PARAM_locate(params, OSSL_KDF_PARAM_SIZE)) != NULL)
 266         return OSSL_PARAM_set_size_t(p, kdf_hkdf_size(ctx));
 267     return -2;
 268 }
 269
 270 static const OSSL_PARAM *kdf_hkdf_gettable_ctx_params(ossl_unused void *ctx,
 271                                                       ossl_unused void *provctx)
 272 {
 273     static const OSSL_PARAM known_gettable_ctx_params[] = {
 274         OSSL_PARAM_size_t(OSSL_KDF_PARAM_SIZE, NULL),
 275         OSSL_PARAM_END
 276     };
 277     return known_gettable_ctx_params;
 278 }
 279
 280 const OSSL_DISPATCH ossl_kdf_hkdf_functions[] = {
 281     { OSSL_FUNC_KDF_NEWCTX, (void(*)(void))kdf_hkdf_new },
 282     { OSSL_FUNC_KDF_FREECTX, (void(*)(void))kdf_hkdf_free },
 283     { OSSL_FUNC_KDF_RESET, (void(*)(void))kdf_hkdf_reset },
 284     { OSSL_FUNC_KDF_DERIVE, (void(*)(void))kdf_hkdf_derive },
 285     { OSSL_FUNC_KDF_SETTABLE_CTX_PARAMS,
 286       (void(*)(void))kdf_hkdf_settable_ctx_params },
 287     { OSSL_FUNC_KDF_SET_CTX_PARAMS, (void(*)(void))kdf_hkdf_set_ctx_params },
 288     { OSSL_FUNC_KDF_GETTABLE_CTX_PARAMS,
 289       (void(*)(void))kdf_hkdf_gettable_ctx_params },
 290     { OSSL_FUNC_KDF_GET_CTX_PARAMS, (void(*)(void))kdf_hkdf_get_ctx_params },
 291     { 0, NULL }
 292 };
 293
 294 /*
 295  * Refer to "HMAC-based Extract-and-Expand Key Derivation Function (HKDF)"
 296  * Section 2 (https://tools.ietf.org/html/rfc5869#section-2) and
 297  * "Cryptographic Extraction and Key Derivation: The HKDF Scheme"
 298  * Section 4.2 (https://eprint.iacr.org/2010/264.pdf).
 299  *
 300  * From the paper:
 301  *   The scheme HKDF is specified as:
 302  *     HKDF(XTS, SKM, CTXinfo, L) = K(1) | K(2) | ... | K(t)
 303  *
 304  *     where:
 305  *       SKM is source key material
 306  *       XTS is extractor salt (which may be null or constant)
 307  *       CTXinfo is context information (may be null)
 308  *       L is the number of key bits to be produced by KDF
 309  *       k is the output length in bits of the hash function used with HMAC
 310  *       t = ceil(L/k)
 311  *       the value K(t) is truncated to its first d = L mod k bits.
 312  *
 313  * From RFC 5869:
 314  *   2.2.  Step 1: Extract
 315  *     HKDF-Extract(salt, IKM) -> PRK
 316  *   2.3.  Step 2: Expand
 317  *     HKDF-Expand(PRK, info, L) -> OKM
 318  */
 319 static int HKDF(OSSL_LIB_CTX *libctx, const EVP_MD *evp_md,
 320                 const unsigned char *salt, size_t salt_len,
 321                 const unsigned char *ikm, size_t ikm_len,
 322                 const unsigned char *info, size_t info_len,
 323                 unsigned char *okm, size_t okm_len)
 324 {
 325     unsigned char prk[EVP_MAX_MD_SIZE];
 326     int ret, sz;
 327     size_t prk_len;
 328
 329     sz = EVP_MD_get_size(evp_md);
 330     if (sz < 0)
 331         return 0;
 332     prk_len = (size_t)sz;
 333
 334     /* Step 1: HKDF-Extract(salt, IKM) -> PRK */
 335     if (!HKDF_Extract(libctx, evp_md,
 336                       salt, salt_len, ikm, ikm_len, prk, prk_len))
 337         return 0;
 338
 339     /* Step 2: HKDF-Expand(PRK, info, L) -> OKM */
 340     ret = HKDF_Expand(evp_md, prk, prk_len, info, info_len, okm, okm_len);
 341     OPENSSL_cleanse(prk, sizeof(prk));
 342
 343     return ret;
 344 }
 345
 346 /*
 347  * Refer to "HMAC-based Extract-and-Expand Key Derivation Function (HKDF)"
 348  * Section 2.2 (https://tools.ietf.org/html/rfc5869#section-2.2).
 349  *
 350  * 2.2.  Step 1: Extract
 351  *
 352  *   HKDF-Extract(salt, IKM) -> PRK
 353  *
 354  *   Options:
 355  *      Hash     a hash function; HashLen denotes the length of the
 356  *               hash function output in octets
 357  *
 358  *   Inputs:
 359  *      salt     optional salt value (a non-secret random value);
 360  *               if not provided, it is set to a string of HashLen zeros.
 361  *      IKM      input keying material
 362  *
 363  *   Output:
 364  *      PRK      a pseudorandom key (of HashLen octets)
 365  *
 366  *   The output PRK is calculated as follows:
 367  *
 368  *   PRK = HMAC-Hash(salt, IKM)
 369  */
 370 static int HKDF_Extract(OSSL_LIB_CTX *libctx, const EVP_MD *evp_md,
 371                         const unsigned char *salt, size_t salt_len,
 372                         const unsigned char *ikm, size_t ikm_len,
 373                         unsigned char *prk, size_t prk_len)
 374 {
 375     int sz = EVP_MD_get_size(evp_md);
 376
 377     if (sz < 0)
 378         return 0;
 379     if (prk_len != (size_t)sz) {
 380         ERR_raise(ERR_LIB_PROV, PROV_R_WRONG_OUTPUT_BUFFER_SIZE);
 381         return 0;
 382     }
 383     /* calc: PRK = HMAC-Hash(salt, IKM) */
 384     return
 385         EVP_Q_mac(libctx, "HMAC", NULL, EVP_MD_get0_name(evp_md), NULL, salt,
 386                   salt_len, ikm, ikm_len, prk, EVP_MD_get_size(evp_md), NULL)
 387         != NULL;
 388 }
 389
 390 /*
 391  * Refer to "HMAC-based Extract-and-Expand Key Derivation Function (HKDF)"
 392  * Section 2.3 (https://tools.ietf.org/html/rfc5869#section-2.3).
 393  *
 394  * 2.3.  Step 2: Expand
 395  *
 396  *   HKDF-Expand(PRK, info, L) -> OKM
 397  *
 398  *   Options:
 399  *      Hash     a hash function; HashLen denotes the length of the
 400  *               hash function output in octets
 401  *
 402  *   Inputs:
 403  *      PRK      a pseudorandom key of at least HashLen octets
 404  *               (usually, the output from the extract step)
 405  *      info     optional context and application specific information
 406  *               (can be a zero-length string)
 407  *      L        length of output keying material in octets
 408  *               (<= 255*HashLen)
 409  *
 410  *   Output:
 411  *      OKM      output keying material (of L octets)
 412  *
 413  *   The output OKM is calculated as follows:
 414  *
 415  *   N = ceil(L/HashLen)
 416  *   T = T(1) | T(2) | T(3) | ... | T(N)
 417  *   OKM = first L octets of T
 418  *
 419  *   where:
 420  *   T(0) = empty string (zero length)
 421  *   T(1) = HMAC-Hash(PRK, T(0) | info | 0x01)
 422  *   T(2) = HMAC-Hash(PRK, T(1) | info | 0x02)
 423  *   T(3) = HMAC-Hash(PRK, T(2) | info | 0x03)
 424  *   ...
 425  *
 426  *   (where the constant concatenated to the end of each T(n) is a
 427  *   single octet.)
 428  */
 429 static int HKDF_Expand(const EVP_MD *evp_md,
 430                        const unsigned char *prk, size_t prk_len,
 431                        const unsigned char *info, size_t info_len,
 432                        unsigned char *okm, size_t okm_len)
 433 {
 434     HMAC_CTX *hmac;
 435     int ret = 0, sz;
 436     unsigned int i;
 437     unsigned char prev[EVP_MAX_MD_SIZE];
 438     size_t done_len = 0, dig_len, n;
 439
 440     sz = EVP_MD_get_size(evp_md);
 441     if (sz <= 0)
 442         return 0;
 443     dig_len = (size_t)sz;
 444
 445     /* calc: N = ceil(L/HashLen) */
 446     n = okm_len / dig_len;
 447     if (okm_len % dig_len)
 448         n++;
 449
 450     if (n > 255 || okm == NULL)
 451         return 0;
 452
 453     if ((hmac = HMAC_CTX_new()) == NULL)
 454         return 0;
 455
 456     if (!HMAC_Init_ex(hmac, prk, prk_len, evp_md, NULL))
 457         goto err;
 458
 459     for (i = 1; i <= n; i++) {
 460         size_t copy_len;
 461         const unsigned char ctr = i;
 462
 463         /* calc: T(i) = HMAC-Hash(PRK, T(i - 1) | info | i) */
 464         if (i > 1) {
 465             if (!HMAC_Init_ex(hmac, NULL, 0, NULL, NULL))
 466                 goto err;
 467
 468             if (!HMAC_Update(hmac, prev, dig_len))
 469                 goto err;
 470         }
 471
 472         if (!HMAC_Update(hmac, info, info_len))
 473             goto err;
 474
 475         if (!HMAC_Update(hmac, &ctr, 1))
 476             goto err;
 477
 478         if (!HMAC_Final(hmac, prev, NULL))
 479             goto err;
 480
 481         copy_len = (done_len + dig_len > okm_len) ?
 482                        okm_len - done_len :
 483                        dig_len;
 484
 485         memcpy(okm + done_len, prev, copy_len);
 486
 487         done_len += copy_len;
 488     }
 489     ret = 1;
 490
 491  err:
 492     OPENSSL_cleanse(prev, sizeof(prev));
 493     HMAC_CTX_free(hmac);
 494     return ret;
 495 }