providers/common/kdfs/hkdf.c

   1 /*
   2  * Copyright 2016-2019 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 #include <stdlib.h>
  11 #include <stdarg.h>
  12 #include <string.h>
  13 #include <openssl/hmac.h>
  14 #include <openssl/evp.h>
  15 #include <openssl/kdf.h>
  16 #include <openssl/core_names.h>
  17 #include "internal/cryptlib.h"
  18 #include "internal/numbers.h"
  19 #include "crypto/evp.h"
  20 #include "internal/provider_ctx.h"
  21 #include "internal/providercommonerr.h"
  22 #include "internal/provider_algs.h"
  23 #include "internal/provider_util.h"
  24 #include "e_os.h"
  25
  26 #define HKDF_MAXBUF 1024
  27
  28 static OSSL_OP_kdf_newctx_fn kdf_hkdf_new;
  29 static OSSL_OP_kdf_freectx_fn kdf_hkdf_free;
  30 static OSSL_OP_kdf_reset_fn kdf_hkdf_reset;
  31 static OSSL_OP_kdf_derive_fn kdf_hkdf_derive;
  32 static OSSL_OP_kdf_settable_ctx_params_fn kdf_hkdf_settable_ctx_params;
  33 static OSSL_OP_kdf_set_ctx_params_fn kdf_hkdf_set_ctx_params;
  34 static OSSL_OP_kdf_gettable_ctx_params_fn kdf_hkdf_gettable_ctx_params;
  35 static OSSL_OP_kdf_get_ctx_params_fn kdf_hkdf_get_ctx_params;
  36
  37 static int HKDF(const EVP_MD *evp_md,
  38                 const unsigned char *salt, size_t salt_len,
  39                 const unsigned char *key, size_t key_len,
  40                 const unsigned char *info, size_t info_len,
  41                 unsigned char *okm, size_t okm_len);
  42 static int HKDF_Extract(const EVP_MD *evp_md,
  43                         const unsigned char *salt, size_t salt_len,
  44                         const unsigned char *ikm, size_t ikm_len,
  45                         unsigned char *prk, size_t prk_len);
  46 static int HKDF_Expand(const EVP_MD *evp_md,
  47                        const unsigned char *prk, size_t prk_len,
  48                        const unsigned char *info, size_t info_len,
  49                        unsigned char *okm, size_t okm_len);
  50
  51 typedef struct {
  52     void *provctx;
  53     int mode;
  54     PROV_DIGEST digest;
  55     unsigned char *salt;
  56     size_t salt_len;
  57     unsigned char *key;
  58     size_t key_len;
  59     unsigned char info[HKDF_MAXBUF];
  60     size_t info_len;
  61 } KDF_HKDF;
  62
  63 static void *kdf_hkdf_new(void *provctx)
  64 {
  65     KDF_HKDF *ctx;
  66
  67     if ((ctx = OPENSSL_zalloc(sizeof(*ctx))) == NULL)
  68         ERR_raise(ERR_LIB_PROV, ERR_R_MALLOC_FAILURE);
  69     else
  70         ctx->provctx = provctx;
  71     return ctx;
  72 }
  73
  74 static void kdf_hkdf_free(void *vctx)
  75 {
  76     KDF_HKDF *ctx = (KDF_HKDF *)vctx;
  77
  78     kdf_hkdf_reset(ctx);
  79     OPENSSL_free(ctx);
  80 }
  81
  82 static void kdf_hkdf_reset(void *vctx)
  83 {
  84     KDF_HKDF *ctx = (KDF_HKDF *)vctx;
  85
  86     ossl_prov_digest_reset(&ctx->digest);
  87     OPENSSL_free(ctx->salt);
  88     OPENSSL_clear_free(ctx->key, ctx->key_len);
  89     OPENSSL_cleanse(ctx->info, ctx->info_len);
  90     memset(ctx, 0, sizeof(*ctx));
  91 }
  92
  93 static size_t kdf_hkdf_size(KDF_HKDF *ctx)
  94 {
  95     int sz;
  96     const EVP_MD *md = ossl_prov_digest_md(&ctx->digest);
  97
  98     if (ctx->mode != EVP_KDF_HKDF_MODE_EXTRACT_ONLY)
  99         return SIZE_MAX;
 100
 101     if (md == NULL) {
 102         ERR_raise(ERR_LIB_PROV, PROV_R_MISSING_MESSAGE_DIGEST);
 103         return 0;
 104     }
 105     sz = EVP_MD_size(md);
 106     if (sz < 0)
 107         return 0;
 108
 109     return sz;
 110 }
 111
 112 static int kdf_hkdf_derive(void *vctx, unsigned char *key, size_t keylen)
 113 {
 114     KDF_HKDF *ctx = (KDF_HKDF *)vctx;
 115     const EVP_MD *md = ossl_prov_digest_md(&ctx->digest);
 116
 117     if (md == NULL) {
 118         ERR_raise(ERR_LIB_PROV, PROV_R_MISSING_MESSAGE_DIGEST);
 119         return 0;
 120     }
 121     if (ctx->key == NULL) {
 122         ERR_raise(ERR_LIB_PROV, PROV_R_MISSING_KEY);
 123         return 0;
 124     }
 125
 126     switch (ctx->mode) {
 127     case EVP_KDF_HKDF_MODE_EXTRACT_AND_EXPAND:
 128         return HKDF(md, ctx->salt, ctx->salt_len, ctx->key,
 129                     ctx->key_len, ctx->info, ctx->info_len, key,
 130                     keylen);
 131
 132     case EVP_KDF_HKDF_MODE_EXTRACT_ONLY:
 133         return HKDF_Extract(md, ctx->salt, ctx->salt_len, ctx->key,
 134                             ctx->key_len, key, keylen);
 135
 136     case EVP_KDF_HKDF_MODE_EXPAND_ONLY:
 137         return HKDF_Expand(md, ctx->key, ctx->key_len, ctx->info,
 138                            ctx->info_len, key, keylen);
 139
 140     default:
 141         return 0;
 142     }
 143 }
 144
 145 static int kdf_hkdf_set_ctx_params(void *vctx, const OSSL_PARAM params[])
 146 {
 147     const OSSL_PARAM *p;
 148     KDF_HKDF *ctx = vctx;
 149     OPENSSL_CTX *provctx = PROV_LIBRARY_CONTEXT_OF(ctx->provctx);
 150     int n;
 151
 152     if (!ossl_prov_digest_load_from_params(&ctx->digest, params, provctx))
 153         return 0;
 154
 155     if ((p = OSSL_PARAM_locate_const(params, OSSL_KDF_PARAM_MODE)) != NULL) {
 156         if (p->data_type == OSSL_PARAM_UTF8_STRING) {
 157             if (strcasecmp(p->data, "EXTRACT_AND_EXPAND") == 0) {
 158                 ctx->mode = EVP_KDF_HKDF_MODE_EXTRACT_AND_EXPAND;
 159             } else if (strcasecmp(p->data, "EXTRACT_ONLY") == 0) {
 160                 ctx->mode = EVP_KDF_HKDF_MODE_EXTRACT_ONLY;
 161             } else if (strcasecmp(p->data, "EXPAND_ONLY") == 0) {
 162                 ctx->mode = EVP_KDF_HKDF_MODE_EXPAND_ONLY;
 163             } else {
 164                 ERR_raise(ERR_LIB_PROV, PROV_R_INVALID_MODE);
 165                 return 0;
 166             }
 167         } else if (OSSL_PARAM_get_int(p, &n)) {
 168             if (n != EVP_KDF_HKDF_MODE_EXTRACT_AND_EXPAND
 169                 && n != EVP_KDF_HKDF_MODE_EXTRACT_ONLY
 170                 && n != EVP_KDF_HKDF_MODE_EXPAND_ONLY) {
 171                 ERR_raise(ERR_LIB_PROV, PROV_R_INVALID_MODE);
 172                 return 0;
 173             }
 174             ctx->mode = n;
 175         } else {
 176             ERR_raise(ERR_LIB_PROV, PROV_R_INVALID_MODE);
 177             return 0;
 178         }
 179     }
 180
 181     if ((p = OSSL_PARAM_locate_const(params, OSSL_KDF_PARAM_KEY)) != NULL) {
 182         OPENSSL_clear_free(ctx->key, ctx->key_len);
 183         ctx->key = NULL;
 184         if (!OSSL_PARAM_get_octet_string(p, (void **)&ctx->key, 0,
 185                                          &ctx->key_len))
 186             return 0;
 187     }
 188
 189     if ((p = OSSL_PARAM_locate_const(params, OSSL_KDF_PARAM_SALT)) != NULL) {
 190         if (p->data_size != 0 && p->data != NULL) {
 191             OPENSSL_free(ctx->salt);
 192             ctx->salt = NULL;
 193             if (!OSSL_PARAM_get_octet_string(p, (void **)&ctx->salt, 0,
 194                                              &ctx->salt_len))
 195                 return 0;
 196         }
 197     }
 198     /* The info fields concatenate, so process them all */
 199     if ((p = OSSL_PARAM_locate_const(params, OSSL_KDF_PARAM_INFO)) != NULL) {
 200         ctx->info_len = 0;
 201         for (; p != NULL; p = OSSL_PARAM_locate_const(p + 1,
 202                                                       OSSL_KDF_PARAM_INFO)) {
 203             const void *q = ctx->info + ctx->info_len;
 204             size_t sz = 0;
 205
 206             if (p->data_size != 0
 207                 && p->data != NULL
 208                 && !OSSL_PARAM_get_octet_string(p, (void **)&q,
 209                                                 HKDF_MAXBUF - ctx->info_len,
 210                                                 &sz))
 211                 return 0;
 212             ctx->info_len += sz;
 213         }
 214     }
 215     return 1;
 216 }
 217
 218 static const OSSL_PARAM *kdf_hkdf_settable_ctx_params(void)
 219 {
 220     static const OSSL_PARAM known_settable_ctx_params[] = {
 221         OSSL_PARAM_utf8_string(OSSL_KDF_PARAM_MODE, NULL, 0),
 222         OSSL_PARAM_int(OSSL_KDF_PARAM_MODE, NULL),
 223         OSSL_PARAM_utf8_string(OSSL_KDF_PARAM_PROPERTIES, NULL, 0),
 224         OSSL_PARAM_utf8_string(OSSL_KDF_PARAM_DIGEST, NULL, 0),
 225         OSSL_PARAM_octet_string(OSSL_KDF_PARAM_SALT, NULL, 0),
 226         OSSL_PARAM_octet_string(OSSL_KDF_PARAM_KEY, NULL, 0),
 227         OSSL_PARAM_octet_string(OSSL_KDF_PARAM_INFO, NULL, 0),
 228         OSSL_PARAM_END
 229     };
 230     return known_settable_ctx_params;
 231 }
 232
 233 static int kdf_hkdf_get_ctx_params(void *vctx, OSSL_PARAM params[])
 234 {
 235     KDF_HKDF *ctx = (KDF_HKDF *)vctx;
 236     OSSL_PARAM *p;
 237
 238     if ((p = OSSL_PARAM_locate(params, OSSL_KDF_PARAM_SIZE)) != NULL)
 239         return OSSL_PARAM_set_size_t(p, kdf_hkdf_size(ctx));
 240     return -2;
 241 }
 242
 243 static const OSSL_PARAM *kdf_hkdf_gettable_ctx_params(void)
 244 {
 245     static const OSSL_PARAM known_gettable_ctx_params[] = {
 246         OSSL_PARAM_size_t(OSSL_KDF_PARAM_SIZE, NULL),
 247         OSSL_PARAM_END
 248     };
 249     return known_gettable_ctx_params;
 250 }
 251
 252 const OSSL_DISPATCH kdf_hkdf_functions[] = {
 253     { OSSL_FUNC_KDF_NEWCTX, (void(*)(void))kdf_hkdf_new },
 254     { OSSL_FUNC_KDF_FREECTX, (void(*)(void))kdf_hkdf_free },
 255     { OSSL_FUNC_KDF_RESET, (void(*)(void))kdf_hkdf_reset },
 256     { OSSL_FUNC_KDF_DERIVE, (void(*)(void))kdf_hkdf_derive },
 257     { OSSL_FUNC_KDF_SETTABLE_CTX_PARAMS,
 258       (void(*)(void))kdf_hkdf_settable_ctx_params },
 259     { OSSL_FUNC_KDF_SET_CTX_PARAMS, (void(*)(void))kdf_hkdf_set_ctx_params },
 260     { OSSL_FUNC_KDF_GETTABLE_CTX_PARAMS,
 261       (void(*)(void))kdf_hkdf_gettable_ctx_params },
 262     { OSSL_FUNC_KDF_GET_CTX_PARAMS, (void(*)(void))kdf_hkdf_get_ctx_params },
 263     { 0, NULL }
 264 };
 265
 266 /*
 267  * Refer to "HMAC-based Extract-and-Expand Key Derivation Function (HKDF)"
 268  * Section 2 (https://tools.ietf.org/html/rfc5869#section-2) and
 269  * "Cryptographic Extraction and Key Derivation: The HKDF Scheme"
 270  * Section 4.2 (https://eprint.iacr.org/2010/264.pdf).
 271  *
 272  * From the paper:
 273  *   The scheme HKDF is specified as:
 274  *     HKDF(XTS, SKM, CTXinfo, L) = K(1) | K(2) | ... | K(t)
 275  *
 276  *     where:
 277  *       SKM is source key material
 278  *       XTS is extractor salt (which may be null or constant)
 279  *       CTXinfo is context information (may be null)
 280  *       L is the number of key bits to be produced by KDF
 281  *       k is the output length in bits of the hash function used with HMAC
 282  *       t = ceil(L/k)
 283  *       the value K(t) is truncated to its first d = L mod k bits.
 284  *
 285  * From RFC 5869:
 286  *   2.2.  Step 1: Extract
 287  *     HKDF-Extract(salt, IKM) -> PRK
 288  *   2.3.  Step 2: Expand
 289  *     HKDF-Expand(PRK, info, L) -> OKM
 290  */
 291 static int HKDF(const EVP_MD *evp_md,
 292                 const unsigned char *salt, size_t salt_len,
 293                 const unsigned char *ikm, size_t ikm_len,
 294                 const unsigned char *info, size_t info_len,
 295                 unsigned char *okm, size_t okm_len)
 296 {
 297     unsigned char prk[EVP_MAX_MD_SIZE];
 298     int ret, sz;
 299     size_t prk_len;
 300
 301     sz = EVP_MD_size(evp_md);
 302     if (sz < 0)
 303         return 0;
 304     prk_len = (size_t)sz;
 305
 306     /* Step 1: HKDF-Extract(salt, IKM) -> PRK */
 307     if (!HKDF_Extract(evp_md, salt, salt_len, ikm, ikm_len, prk, prk_len))
 308         return 0;
 309
 310     /* Step 2: HKDF-Expand(PRK, info, L) -> OKM */
 311     ret = HKDF_Expand(evp_md, prk, prk_len, info, info_len, okm, okm_len);
 312     OPENSSL_cleanse(prk, sizeof(prk));
 313
 314     return ret;
 315 }
 316
 317 /*
 318  * Refer to "HMAC-based Extract-and-Expand Key Derivation Function (HKDF)"
 319  * Section 2.2 (https://tools.ietf.org/html/rfc5869#section-2.2).
 320  *
 321  * 2.2.  Step 1: Extract
 322  *
 323  *   HKDF-Extract(salt, IKM) -> PRK
 324  *
 325  *   Options:
 326  *      Hash     a hash function; HashLen denotes the length of the
 327  *               hash function output in octets
 328  *
 329  *   Inputs:
 330  *      salt     optional salt value (a non-secret random value);
 331  *               if not provided, it is set to a string of HashLen zeros.
 332  *      IKM      input keying material
 333  *
 334  *   Output:
 335  *      PRK      a pseudorandom key (of HashLen octets)
 336  *
 337  *   The output PRK is calculated as follows:
 338  *
 339  *   PRK = HMAC-Hash(salt, IKM)
 340  */
 341 static int HKDF_Extract(const EVP_MD *evp_md,
 342                         const unsigned char *salt, size_t salt_len,
 343                         const unsigned char *ikm, size_t ikm_len,
 344                         unsigned char *prk, size_t prk_len)
 345 {
 346     int sz = EVP_MD_size(evp_md);
 347
 348     if (sz < 0)
 349         return 0;
 350     if (prk_len != (size_t)sz) {
 351         ERR_raise(ERR_LIB_PROV, PROV_R_WRONG_OUTPUT_BUFFER_SIZE);
 352         return 0;
 353     }
 354     /* calc: PRK = HMAC-Hash(salt, IKM) */
 355     return HMAC(evp_md, salt, salt_len, ikm, ikm_len, prk, NULL) != NULL;
 356 }
 357
 358 /*
 359  * Refer to "HMAC-based Extract-and-Expand Key Derivation Function (HKDF)"
 360  * Section 2.3 (https://tools.ietf.org/html/rfc5869#section-2.3).
 361  *
 362  * 2.3.  Step 2: Expand
 363  *
 364  *   HKDF-Expand(PRK, info, L) -> OKM
 365  *
 366  *   Options:
 367  *      Hash     a hash function; HashLen denotes the length of the
 368  *               hash function output in octets
 369  *
 370  *   Inputs:
 371  *      PRK      a pseudorandom key of at least HashLen octets
 372  *               (usually, the output from the extract step)
 373  *      info     optional context and application specific information
 374  *               (can be a zero-length string)
 375  *      L        length of output keying material in octets
 376  *               (<= 255*HashLen)
 377  *
 378  *   Output:
 379  *      OKM      output keying material (of L octets)
 380  *
 381  *   The output OKM is calculated as follows:
 382  *
 383  *   N = ceil(L/HashLen)
 384  *   T = T(1) | T(2) | T(3) | ... | T(N)
 385  *   OKM = first L octets of T
 386  *
 387  *   where:
 388  *   T(0) = empty string (zero length)
 389  *   T(1) = HMAC-Hash(PRK, T(0) | info | 0x01)
 390  *   T(2) = HMAC-Hash(PRK, T(1) | info | 0x02)
 391  *   T(3) = HMAC-Hash(PRK, T(2) | info | 0x03)
 392  *   ...
 393  *
 394  *   (where the constant concatenated to the end of each T(n) is a
 395  *   single octet.)
 396  */
 397 static int HKDF_Expand(const EVP_MD *evp_md,
 398                        const unsigned char *prk, size_t prk_len,
 399                        const unsigned char *info, size_t info_len,
 400                        unsigned char *okm, size_t okm_len)
 401 {
 402     HMAC_CTX *hmac;
 403     int ret = 0, sz;
 404     unsigned int i;
 405     unsigned char prev[EVP_MAX_MD_SIZE];
 406     size_t done_len = 0, dig_len, n;
 407
 408     sz = EVP_MD_size(evp_md);
 409     if (sz <= 0)
 410         return 0;
 411     dig_len = (size_t)sz;
 412
 413     /* calc: N = ceil(L/HashLen) */
 414     n = okm_len / dig_len;
 415     if (okm_len % dig_len)
 416         n++;
 417
 418     if (n > 255 || okm == NULL)
 419         return 0;
 420
 421     if ((hmac = HMAC_CTX_new()) == NULL)
 422         return 0;
 423
 424     if (!HMAC_Init_ex(hmac, prk, prk_len, evp_md, NULL))
 425         goto err;
 426
 427     for (i = 1; i <= n; i++) {
 428         size_t copy_len;
 429         const unsigned char ctr = i;
 430
 431         /* calc: T(i) = HMAC-Hash(PRK, T(i - 1) | info | i) */
 432         if (i > 1) {
 433             if (!HMAC_Init_ex(hmac, NULL, 0, NULL, NULL))
 434                 goto err;
 435
 436             if (!HMAC_Update(hmac, prev, dig_len))
 437                 goto err;
 438         }
 439
 440         if (!HMAC_Update(hmac, info, info_len))
 441             goto err;
 442
 443         if (!HMAC_Update(hmac, &ctr, 1))
 444             goto err;
 445
 446         if (!HMAC_Final(hmac, prev, NULL))
 447             goto err;
 448
 449         copy_len = (done_len + dig_len > okm_len) ?
 450                        okm_len - done_len :
 451                        dig_len;
 452
 453         memcpy(okm + done_len, prev, copy_len);
 454
 455         done_len += copy_len;
 456     }
 457     ret = 1;
 458
 459  err:
 460     OPENSSL_cleanse(prev, sizeof(prev));
 461     HMAC_CTX_free(hmac);
 462     return ret;
 463 }