providers/implementations/kdfs/hkdf.c

   1 /*
   2  * Copyright 2016-2020 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 "internal/cryptlib.h"
  24 #include "internal/numbers.h"
  25 #include "crypto/evp.h"
  26 #include "prov/provider_ctx.h"
  27 #include "prov/providercommon.h"
  28 #include "prov/providercommonerr.h"
  29 #include "prov/implementations.h"
  30 #include "prov/provider_util.h"
  31 #include "e_os.h"
  32
  33 #define HKDF_MAXBUF 1024
  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(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(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_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 {
 128     KDF_HKDF *ctx = (KDF_HKDF *)vctx;
 129     const EVP_MD *md;
 130
 131     if (!ossl_prov_is_running())
 132         return 0;
 133
 134     md = ossl_prov_digest_md(&ctx->digest);
 135     if (md == NULL) {
 136         ERR_raise(ERR_LIB_PROV, PROV_R_MISSING_MESSAGE_DIGEST);
 137         return 0;
 138     }
 139     if (ctx->key == NULL) {
 140         ERR_raise(ERR_LIB_PROV, PROV_R_MISSING_KEY);
 141         return 0;
 142     }
 143     if (keylen == 0) {
 144         ERR_raise(ERR_LIB_PROV, PROV_R_INVALID_KEY_LENGTH);
 145         return 0;
 146     }
 147
 148     switch (ctx->mode) {
 149     case EVP_KDF_HKDF_MODE_EXTRACT_AND_EXPAND:
 150         return HKDF(md, ctx->salt, ctx->salt_len, ctx->key,
 151                     ctx->key_len, ctx->info, ctx->info_len, key,
 152                     keylen);
 153
 154     case EVP_KDF_HKDF_MODE_EXTRACT_ONLY:
 155         return HKDF_Extract(md, ctx->salt, ctx->salt_len, ctx->key,
 156                             ctx->key_len, key, keylen);
 157
 158     case EVP_KDF_HKDF_MODE_EXPAND_ONLY:
 159         return HKDF_Expand(md, ctx->key, ctx->key_len, ctx->info,
 160                            ctx->info_len, key, keylen);
 161
 162     default:
 163         return 0;
 164     }
 165 }
 166
 167 static int kdf_hkdf_set_ctx_params(void *vctx, const OSSL_PARAM params[])
 168 {
 169     const OSSL_PARAM *p;
 170     KDF_HKDF *ctx = vctx;
 171     OSSL_LIB_CTX *provctx = PROV_LIBRARY_CONTEXT_OF(ctx->provctx);
 172     int n;
 173
 174     if (!ossl_prov_digest_load_from_params(&ctx->digest, params, provctx))
 175         return 0;
 176
 177     if ((p = OSSL_PARAM_locate_const(params, OSSL_KDF_PARAM_MODE)) != NULL) {
 178         if (p->data_type == OSSL_PARAM_UTF8_STRING) {
 179             if (strcasecmp(p->data, "EXTRACT_AND_EXPAND") == 0) {
 180                 ctx->mode = EVP_KDF_HKDF_MODE_EXTRACT_AND_EXPAND;
 181             } else if (strcasecmp(p->data, "EXTRACT_ONLY") == 0) {
 182                 ctx->mode = EVP_KDF_HKDF_MODE_EXTRACT_ONLY;
 183             } else if (strcasecmp(p->data, "EXPAND_ONLY") == 0) {
 184                 ctx->mode = EVP_KDF_HKDF_MODE_EXPAND_ONLY;
 185             } else {
 186                 ERR_raise(ERR_LIB_PROV, PROV_R_INVALID_MODE);
 187                 return 0;
 188             }
 189         } else if (OSSL_PARAM_get_int(p, &n)) {
 190             if (n != EVP_KDF_HKDF_MODE_EXTRACT_AND_EXPAND
 191                 && n != EVP_KDF_HKDF_MODE_EXTRACT_ONLY
 192                 && n != EVP_KDF_HKDF_MODE_EXPAND_ONLY) {
 193                 ERR_raise(ERR_LIB_PROV, PROV_R_INVALID_MODE);
 194                 return 0;
 195             }
 196             ctx->mode = n;
 197         } else {
 198             ERR_raise(ERR_LIB_PROV, PROV_R_INVALID_MODE);
 199             return 0;
 200         }
 201     }
 202
 203     if ((p = OSSL_PARAM_locate_const(params, OSSL_KDF_PARAM_KEY)) != NULL) {
 204         OPENSSL_clear_free(ctx->key, ctx->key_len);
 205         ctx->key = NULL;
 206         if (!OSSL_PARAM_get_octet_string(p, (void **)&ctx->key, 0,
 207                                          &ctx->key_len))
 208             return 0;
 209     }
 210
 211     if ((p = OSSL_PARAM_locate_const(params, OSSL_KDF_PARAM_SALT)) != NULL) {
 212         if (p->data_size != 0 && p->data != NULL) {
 213             OPENSSL_free(ctx->salt);
 214             ctx->salt = NULL;
 215             if (!OSSL_PARAM_get_octet_string(p, (void **)&ctx->salt, 0,
 216                                              &ctx->salt_len))
 217                 return 0;
 218         }
 219     }
 220     /* The info fields concatenate, so process them all */
 221     if ((p = OSSL_PARAM_locate_const(params, OSSL_KDF_PARAM_INFO)) != NULL) {
 222         ctx->info_len = 0;
 223         for (; p != NULL; p = OSSL_PARAM_locate_const(p + 1,
 224                                                       OSSL_KDF_PARAM_INFO)) {
 225             const void *q = ctx->info + ctx->info_len;
 226             size_t sz = 0;
 227
 228             if (p->data_size != 0
 229                 && p->data != NULL
 230                 && !OSSL_PARAM_get_octet_string(p, (void **)&q,
 231                                                 HKDF_MAXBUF - ctx->info_len,
 232                                                 &sz))
 233                 return 0;
 234             ctx->info_len += sz;
 235         }
 236     }
 237     return 1;
 238 }
 239
 240 static const OSSL_PARAM *kdf_hkdf_settable_ctx_params(ossl_unused void *provctx)
 241 {
 242     static const OSSL_PARAM known_settable_ctx_params[] = {
 243         OSSL_PARAM_utf8_string(OSSL_KDF_PARAM_MODE, NULL, 0),
 244         OSSL_PARAM_int(OSSL_KDF_PARAM_MODE, NULL),
 245         OSSL_PARAM_utf8_string(OSSL_KDF_PARAM_PROPERTIES, NULL, 0),
 246         OSSL_PARAM_utf8_string(OSSL_KDF_PARAM_DIGEST, NULL, 0),
 247         OSSL_PARAM_octet_string(OSSL_KDF_PARAM_SALT, NULL, 0),
 248         OSSL_PARAM_octet_string(OSSL_KDF_PARAM_KEY, NULL, 0),
 249         OSSL_PARAM_octet_string(OSSL_KDF_PARAM_INFO, NULL, 0),
 250         OSSL_PARAM_END
 251     };
 252     return known_settable_ctx_params;
 253 }
 254
 255 static int kdf_hkdf_get_ctx_params(void *vctx, OSSL_PARAM params[])
 256 {
 257     KDF_HKDF *ctx = (KDF_HKDF *)vctx;
 258     OSSL_PARAM *p;
 259
 260     if ((p = OSSL_PARAM_locate(params, OSSL_KDF_PARAM_SIZE)) != NULL)
 261         return OSSL_PARAM_set_size_t(p, kdf_hkdf_size(ctx));
 262     return -2;
 263 }
 264
 265 static const OSSL_PARAM *kdf_hkdf_gettable_ctx_params(ossl_unused void *provctx)
 266 {
 267     static const OSSL_PARAM known_gettable_ctx_params[] = {
 268         OSSL_PARAM_size_t(OSSL_KDF_PARAM_SIZE, NULL),
 269         OSSL_PARAM_END
 270     };
 271     return known_gettable_ctx_params;
 272 }
 273
 274 const OSSL_DISPATCH ossl_kdf_hkdf_functions[] = {
 275     { OSSL_FUNC_KDF_NEWCTX, (void(*)(void))kdf_hkdf_new },
 276     { OSSL_FUNC_KDF_FREECTX, (void(*)(void))kdf_hkdf_free },
 277     { OSSL_FUNC_KDF_RESET, (void(*)(void))kdf_hkdf_reset },
 278     { OSSL_FUNC_KDF_DERIVE, (void(*)(void))kdf_hkdf_derive },
 279     { OSSL_FUNC_KDF_SETTABLE_CTX_PARAMS,
 280       (void(*)(void))kdf_hkdf_settable_ctx_params },
 281     { OSSL_FUNC_KDF_SET_CTX_PARAMS, (void(*)(void))kdf_hkdf_set_ctx_params },
 282     { OSSL_FUNC_KDF_GETTABLE_CTX_PARAMS,
 283       (void(*)(void))kdf_hkdf_gettable_ctx_params },
 284     { OSSL_FUNC_KDF_GET_CTX_PARAMS, (void(*)(void))kdf_hkdf_get_ctx_params },
 285     { 0, NULL }
 286 };
 287
 288 /*
 289  * Refer to "HMAC-based Extract-and-Expand Key Derivation Function (HKDF)"
 290  * Section 2 (https://tools.ietf.org/html/rfc5869#section-2) and
 291  * "Cryptographic Extraction and Key Derivation: The HKDF Scheme"
 292  * Section 4.2 (https://eprint.iacr.org/2010/264.pdf).
 293  *
 294  * From the paper:
 295  *   The scheme HKDF is specified as:
 296  *     HKDF(XTS, SKM, CTXinfo, L) = K(1) | K(2) | ... | K(t)
 297  *
 298  *     where:
 299  *       SKM is source key material
 300  *       XTS is extractor salt (which may be null or constant)
 301  *       CTXinfo is context information (may be null)
 302  *       L is the number of key bits to be produced by KDF
 303  *       k is the output length in bits of the hash function used with HMAC
 304  *       t = ceil(L/k)
 305  *       the value K(t) is truncated to its first d = L mod k bits.
 306  *
 307  * From RFC 5869:
 308  *   2.2.  Step 1: Extract
 309  *     HKDF-Extract(salt, IKM) -> PRK
 310  *   2.3.  Step 2: Expand
 311  *     HKDF-Expand(PRK, info, L) -> OKM
 312  */
 313 static int HKDF(const EVP_MD *evp_md,
 314                 const unsigned char *salt, size_t salt_len,
 315                 const unsigned char *ikm, size_t ikm_len,
 316                 const unsigned char *info, size_t info_len,
 317                 unsigned char *okm, size_t okm_len)
 318 {
 319     unsigned char prk[EVP_MAX_MD_SIZE];
 320     int ret, sz;
 321     size_t prk_len;
 322
 323     sz = EVP_MD_size(evp_md);
 324     if (sz < 0)
 325         return 0;
 326     prk_len = (size_t)sz;
 327
 328     /* Step 1: HKDF-Extract(salt, IKM) -> PRK */
 329     if (!HKDF_Extract(evp_md, salt, salt_len, ikm, ikm_len, prk, prk_len))
 330         return 0;
 331
 332     /* Step 2: HKDF-Expand(PRK, info, L) -> OKM */
 333     ret = HKDF_Expand(evp_md, prk, prk_len, info, info_len, okm, okm_len);
 334     OPENSSL_cleanse(prk, sizeof(prk));
 335
 336     return ret;
 337 }
 338
 339 /*
 340  * Refer to "HMAC-based Extract-and-Expand Key Derivation Function (HKDF)"
 341  * Section 2.2 (https://tools.ietf.org/html/rfc5869#section-2.2).
 342  *
 343  * 2.2.  Step 1: Extract
 344  *
 345  *   HKDF-Extract(salt, IKM) -> PRK
 346  *
 347  *   Options:
 348  *      Hash     a hash function; HashLen denotes the length of the
 349  *               hash function output in octets
 350  *
 351  *   Inputs:
 352  *      salt     optional salt value (a non-secret random value);
 353  *               if not provided, it is set to a string of HashLen zeros.
 354  *      IKM      input keying material
 355  *
 356  *   Output:
 357  *      PRK      a pseudorandom key (of HashLen octets)
 358  *
 359  *   The output PRK is calculated as follows:
 360  *
 361  *   PRK = HMAC-Hash(salt, IKM)
 362  */
 363 static int HKDF_Extract(const EVP_MD *evp_md,
 364                         const unsigned char *salt, size_t salt_len,
 365                         const unsigned char *ikm, size_t ikm_len,
 366                         unsigned char *prk, size_t prk_len)
 367 {
 368     int sz = EVP_MD_size(evp_md);
 369
 370     if (sz < 0)
 371         return 0;
 372     if (prk_len != (size_t)sz) {
 373         ERR_raise(ERR_LIB_PROV, PROV_R_WRONG_OUTPUT_BUFFER_SIZE);
 374         return 0;
 375     }
 376     /* calc: PRK = HMAC-Hash(salt, IKM) */
 377     return HMAC(evp_md, salt, salt_len, ikm, ikm_len, prk, NULL) != NULL;
 378 }
 379
 380 /*
 381  * Refer to "HMAC-based Extract-and-Expand Key Derivation Function (HKDF)"
 382  * Section 2.3 (https://tools.ietf.org/html/rfc5869#section-2.3).
 383  *
 384  * 2.3.  Step 2: Expand
 385  *
 386  *   HKDF-Expand(PRK, info, L) -> OKM
 387  *
 388  *   Options:
 389  *      Hash     a hash function; HashLen denotes the length of the
 390  *               hash function output in octets
 391  *
 392  *   Inputs:
 393  *      PRK      a pseudorandom key of at least HashLen octets
 394  *               (usually, the output from the extract step)
 395  *      info     optional context and application specific information
 396  *               (can be a zero-length string)
 397  *      L        length of output keying material in octets
 398  *               (<= 255*HashLen)
 399  *
 400  *   Output:
 401  *      OKM      output keying material (of L octets)
 402  *
 403  *   The output OKM is calculated as follows:
 404  *
 405  *   N = ceil(L/HashLen)
 406  *   T = T(1) | T(2) | T(3) | ... | T(N)
 407  *   OKM = first L octets of T
 408  *
 409  *   where:
 410  *   T(0) = empty string (zero length)
 411  *   T(1) = HMAC-Hash(PRK, T(0) | info | 0x01)
 412  *   T(2) = HMAC-Hash(PRK, T(1) | info | 0x02)
 413  *   T(3) = HMAC-Hash(PRK, T(2) | info | 0x03)
 414  *   ...
 415  *
 416  *   (where the constant concatenated to the end of each T(n) is a
 417  *   single octet.)
 418  */
 419 static int HKDF_Expand(const EVP_MD *evp_md,
 420                        const unsigned char *prk, size_t prk_len,
 421                        const unsigned char *info, size_t info_len,
 422                        unsigned char *okm, size_t okm_len)
 423 {
 424     HMAC_CTX *hmac;
 425     int ret = 0, sz;
 426     unsigned int i;
 427     unsigned char prev[EVP_MAX_MD_SIZE];
 428     size_t done_len = 0, dig_len, n;
 429
 430     sz = EVP_MD_size(evp_md);
 431     if (sz <= 0)
 432         return 0;
 433     dig_len = (size_t)sz;
 434
 435     /* calc: N = ceil(L/HashLen) */
 436     n = okm_len / dig_len;
 437     if (okm_len % dig_len)
 438         n++;
 439
 440     if (n > 255 || okm == NULL)
 441         return 0;
 442
 443     if ((hmac = HMAC_CTX_new()) == NULL)
 444         return 0;
 445
 446     if (!HMAC_Init_ex(hmac, prk, prk_len, evp_md, NULL))
 447         goto err;
 448
 449     for (i = 1; i <= n; i++) {
 450         size_t copy_len;
 451         const unsigned char ctr = i;
 452
 453         /* calc: T(i) = HMAC-Hash(PRK, T(i - 1) | info | i) */
 454         if (i > 1) {
 455             if (!HMAC_Init_ex(hmac, NULL, 0, NULL, NULL))
 456                 goto err;
 457
 458             if (!HMAC_Update(hmac, prev, dig_len))
 459                 goto err;
 460         }
 461
 462         if (!HMAC_Update(hmac, info, info_len))
 463             goto err;
 464
 465         if (!HMAC_Update(hmac, &ctr, 1))
 466             goto err;
 467
 468         if (!HMAC_Final(hmac, prev, NULL))
 469             goto err;
 470
 471         copy_len = (done_len + dig_len > okm_len) ?
 472                        okm_len - done_len :
 473                        dig_len;
 474
 475         memcpy(okm + done_len, prev, copy_len);
 476
 477         done_len += copy_len;
 478     }
 479     ret = 1;
 480
 481  err:
 482     OPENSSL_cleanse(prev, sizeof(prev));
 483     HMAC_CTX_free(hmac);
 484     return ret;
 485 }