providers/implementations/kdfs/hkdf.c

   1 /*
   2  * Copyright 2016-2022 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 "internal/packet.h"
  27 #include "crypto/evp.h"
  28 #include "prov/provider_ctx.h"
  29 #include "prov/providercommon.h"
  30 #include "prov/implementations.h"
  31 #include "prov/provider_util.h"
  32 #include "internal/e_os.h"
  33
  34 #define HKDF_MAXBUF 2048
  35
  36 static OSSL_FUNC_kdf_newctx_fn kdf_hkdf_new;
  37 static OSSL_FUNC_kdf_dupctx_fn kdf_hkdf_dup;
  38 static OSSL_FUNC_kdf_freectx_fn kdf_hkdf_free;
  39 static OSSL_FUNC_kdf_reset_fn kdf_hkdf_reset;
  40 static OSSL_FUNC_kdf_derive_fn kdf_hkdf_derive;
  41 static OSSL_FUNC_kdf_settable_ctx_params_fn kdf_hkdf_settable_ctx_params;
  42 static OSSL_FUNC_kdf_set_ctx_params_fn kdf_hkdf_set_ctx_params;
  43 static OSSL_FUNC_kdf_gettable_ctx_params_fn kdf_hkdf_gettable_ctx_params;
  44 static OSSL_FUNC_kdf_get_ctx_params_fn kdf_hkdf_get_ctx_params;
  45 static OSSL_FUNC_kdf_derive_fn kdf_tls1_3_derive;
  46 static OSSL_FUNC_kdf_settable_ctx_params_fn kdf_tls1_3_settable_ctx_params;
  47 static OSSL_FUNC_kdf_set_ctx_params_fn kdf_tls1_3_set_ctx_params;
  48
  49 static int HKDF(OSSL_LIB_CTX *libctx, const EVP_MD *evp_md,
  50                 const unsigned char *salt, size_t salt_len,
  51                 const unsigned char *key, size_t key_len,
  52                 const unsigned char *info, size_t info_len,
  53                 unsigned char *okm, size_t okm_len);
  54 static int HKDF_Extract(OSSL_LIB_CTX *libctx, const EVP_MD *evp_md,
  55                         const unsigned char *salt, size_t salt_len,
  56                         const unsigned char *ikm, size_t ikm_len,
  57                         unsigned char *prk, size_t prk_len);
  58 static int HKDF_Expand(const EVP_MD *evp_md,
  59                        const unsigned char *prk, size_t prk_len,
  60                        const unsigned char *info, size_t info_len,
  61                        unsigned char *okm, size_t okm_len);
  62
  63 /* Settable context parameters that are common across HKDF and the TLS KDF */
  64 #define HKDF_COMMON_SETTABLES                                           \
  65         OSSL_PARAM_utf8_string(OSSL_KDF_PARAM_MODE, NULL, 0),           \
  66         OSSL_PARAM_int(OSSL_KDF_PARAM_MODE, NULL),                      \
  67         OSSL_PARAM_utf8_string(OSSL_KDF_PARAM_PROPERTIES, NULL, 0),     \
  68         OSSL_PARAM_utf8_string(OSSL_KDF_PARAM_DIGEST, NULL, 0),         \
  69         OSSL_PARAM_octet_string(OSSL_KDF_PARAM_KEY, NULL, 0),           \
  70         OSSL_PARAM_octet_string(OSSL_KDF_PARAM_SALT, NULL, 0)
  71
  72 typedef struct {
  73     void *provctx;
  74     int mode;
  75     PROV_DIGEST digest;
  76     unsigned char *salt;
  77     size_t salt_len;
  78     unsigned char *key;
  79     size_t key_len;
  80     unsigned char *prefix;
  81     size_t prefix_len;
  82     unsigned char *label;
  83     size_t label_len;
  84     unsigned char *data;
  85     size_t data_len;
  86     unsigned char info[HKDF_MAXBUF];
  87     size_t info_len;
  88 } KDF_HKDF;
  89
  90 static void *kdf_hkdf_new(void *provctx)
  91 {
  92     KDF_HKDF *ctx;
  93
  94     if (!ossl_prov_is_running())
  95         return NULL;
  96
  97     if ((ctx = OPENSSL_zalloc(sizeof(*ctx))) == NULL)
  98         ERR_raise(ERR_LIB_PROV, ERR_R_MALLOC_FAILURE);
  99     else
 100         ctx->provctx = provctx;
 101     return ctx;
 102 }
 103
 104 static void kdf_hkdf_free(void *vctx)
 105 {
 106     KDF_HKDF *ctx = (KDF_HKDF *)vctx;
 107
 108     if (ctx != NULL) {
 109         kdf_hkdf_reset(ctx);
 110         OPENSSL_free(ctx);
 111     }
 112 }
 113
 114 static void kdf_hkdf_reset(void *vctx)
 115 {
 116     KDF_HKDF *ctx = (KDF_HKDF *)vctx;
 117     void *provctx = ctx->provctx;
 118
 119     ossl_prov_digest_reset(&ctx->digest);
 120     OPENSSL_free(ctx->salt);
 121     OPENSSL_free(ctx->prefix);
 122     OPENSSL_free(ctx->label);
 123     OPENSSL_clear_free(ctx->data, ctx->data_len);
 124     OPENSSL_clear_free(ctx->key, ctx->key_len);
 125     OPENSSL_cleanse(ctx->info, ctx->info_len);
 126     memset(ctx, 0, sizeof(*ctx));
 127     ctx->provctx = provctx;
 128 }
 129
 130 static void *kdf_hkdf_dup(void *vctx)
 131 {
 132     const KDF_HKDF *src = (const KDF_HKDF *)vctx;
 133     KDF_HKDF *dest;
 134
 135     dest = kdf_hkdf_new(src->provctx);
 136     if (dest != NULL) {
 137         if (!ossl_prov_memdup(src->salt, src->salt_len, &dest->salt,
 138                               &dest->salt_len)
 139                 || !ossl_prov_memdup(src->key, src->key_len,
 140                                      &dest->key , &dest->key_len)
 141                 || !ossl_prov_memdup(src->prefix, src->prefix_len,
 142                                      &dest->prefix, &dest->prefix_len)
 143                 || !ossl_prov_memdup(src->label, src->label_len,
 144                                      &dest->label, &dest->label_len)
 145                 || !ossl_prov_memdup(src->data, src->data_len,
 146                                      &dest->data, &dest->data_len)
 147                 || !ossl_prov_digest_copy(&dest->digest, &src->digest))
 148             goto err;
 149         memcpy(dest->info, src->info, sizeof(dest->info));
 150         dest->info_len = src->info_len;
 151         dest->mode = src->mode;
 152     }
 153     return dest;
 154
 155  err:
 156     kdf_hkdf_free(dest);
 157     return NULL;
 158 }
 159
 160 static size_t kdf_hkdf_size(KDF_HKDF *ctx)
 161 {
 162     int sz;
 163     const EVP_MD *md = ossl_prov_digest_md(&ctx->digest);
 164
 165     if (ctx->mode != EVP_KDF_HKDF_MODE_EXTRACT_ONLY)
 166         return SIZE_MAX;
 167
 168     if (md == NULL) {
 169         ERR_raise(ERR_LIB_PROV, PROV_R_MISSING_MESSAGE_DIGEST);
 170         return 0;
 171     }
 172     sz = EVP_MD_get_size(md);
 173     if (sz < 0)
 174         return 0;
 175
 176     return sz;
 177 }
 178
 179 static int kdf_hkdf_derive(void *vctx, unsigned char *key, size_t keylen,
 180                            const OSSL_PARAM params[])
 181 {
 182     KDF_HKDF *ctx = (KDF_HKDF *)vctx;
 183     OSSL_LIB_CTX *libctx = PROV_LIBCTX_OF(ctx->provctx);
 184     const EVP_MD *md;
 185
 186     if (!ossl_prov_is_running() || !kdf_hkdf_set_ctx_params(ctx, params))
 187         return 0;
 188
 189     md = ossl_prov_digest_md(&ctx->digest);
 190     if (md == NULL) {
 191         ERR_raise(ERR_LIB_PROV, PROV_R_MISSING_MESSAGE_DIGEST);
 192         return 0;
 193     }
 194     if (ctx->key == NULL) {
 195         ERR_raise(ERR_LIB_PROV, PROV_R_MISSING_KEY);
 196         return 0;
 197     }
 198     if (keylen == 0) {
 199         ERR_raise(ERR_LIB_PROV, PROV_R_INVALID_KEY_LENGTH);
 200         return 0;
 201     }
 202
 203     switch (ctx->mode) {
 204     case EVP_KDF_HKDF_MODE_EXTRACT_AND_EXPAND:
 205     default:
 206         return HKDF(libctx, md, ctx->salt, ctx->salt_len,
 207                     ctx->key, ctx->key_len, ctx->info, ctx->info_len, key, keylen);
 208
 209     case EVP_KDF_HKDF_MODE_EXTRACT_ONLY:
 210         return HKDF_Extract(libctx, md, ctx->salt, ctx->salt_len,
 211                             ctx->key, ctx->key_len, key, keylen);
 212
 213     case EVP_KDF_HKDF_MODE_EXPAND_ONLY:
 214         return HKDF_Expand(md, ctx->key, ctx->key_len, ctx->info,
 215                            ctx->info_len, key, keylen);
 216     }
 217 }
 218
 219 static int hkdf_common_set_ctx_params(KDF_HKDF *ctx, const OSSL_PARAM params[])
 220 {
 221     OSSL_LIB_CTX *libctx = PROV_LIBCTX_OF(ctx->provctx);
 222     const OSSL_PARAM *p;
 223     int n;
 224
 225     if (params == NULL)
 226         return 1;
 227
 228     if (!ossl_prov_digest_load_from_params(&ctx->digest, params, libctx))
 229         return 0;
 230
 231     if ((p = OSSL_PARAM_locate_const(params, OSSL_KDF_PARAM_MODE)) != NULL) {
 232         if (p->data_type == OSSL_PARAM_UTF8_STRING) {
 233             if (OPENSSL_strcasecmp(p->data, "EXTRACT_AND_EXPAND") == 0) {
 234                 ctx->mode = EVP_KDF_HKDF_MODE_EXTRACT_AND_EXPAND;
 235             } else if (OPENSSL_strcasecmp(p->data, "EXTRACT_ONLY") == 0) {
 236                 ctx->mode = EVP_KDF_HKDF_MODE_EXTRACT_ONLY;
 237             } else if (OPENSSL_strcasecmp(p->data, "EXPAND_ONLY") == 0) {
 238                 ctx->mode = EVP_KDF_HKDF_MODE_EXPAND_ONLY;
 239             } else {
 240                 ERR_raise(ERR_LIB_PROV, PROV_R_INVALID_MODE);
 241                 return 0;
 242             }
 243         } else if (OSSL_PARAM_get_int(p, &n)) {
 244             if (n != EVP_KDF_HKDF_MODE_EXTRACT_AND_EXPAND
 245                 && n != EVP_KDF_HKDF_MODE_EXTRACT_ONLY
 246                 && n != EVP_KDF_HKDF_MODE_EXPAND_ONLY) {
 247                 ERR_raise(ERR_LIB_PROV, PROV_R_INVALID_MODE);
 248                 return 0;
 249             }
 250             ctx->mode = n;
 251         } else {
 252             ERR_raise(ERR_LIB_PROV, PROV_R_INVALID_MODE);
 253             return 0;
 254         }
 255     }
 256
 257     if ((p = OSSL_PARAM_locate_const(params, OSSL_KDF_PARAM_KEY)) != NULL) {
 258         OPENSSL_clear_free(ctx->key, ctx->key_len);
 259         ctx->key = NULL;
 260         if (!OSSL_PARAM_get_octet_string(p, (void **)&ctx->key, 0,
 261                                          &ctx->key_len))
 262             return 0;
 263     }
 264
 265     if ((p = OSSL_PARAM_locate_const(params, OSSL_KDF_PARAM_SALT)) != NULL) {
 266         if (p->data_size != 0 && p->data != NULL) {
 267             OPENSSL_free(ctx->salt);
 268             ctx->salt = NULL;
 269             if (!OSSL_PARAM_get_octet_string(p, (void **)&ctx->salt, 0,
 270                                              &ctx->salt_len))
 271                 return 0;
 272         }
 273     }
 274
 275     return 1;
 276 }
 277
 278 static int kdf_hkdf_set_ctx_params(void *vctx, const OSSL_PARAM params[])
 279 {
 280     const OSSL_PARAM *p;
 281     KDF_HKDF *ctx = vctx;
 282
 283     if (params == NULL)
 284         return 1;
 285
 286     if (!hkdf_common_set_ctx_params(ctx, params))
 287         return 0;
 288
 289     /* The info fields concatenate, so process them all */
 290     if ((p = OSSL_PARAM_locate_const(params, OSSL_KDF_PARAM_INFO)) != NULL) {
 291         ctx->info_len = 0;
 292         for (; p != NULL; p = OSSL_PARAM_locate_const(p + 1,
 293                                                       OSSL_KDF_PARAM_INFO)) {
 294             const void *q = ctx->info + ctx->info_len;
 295             size_t sz = 0;
 296
 297             if (p->data_size != 0
 298                 && p->data != NULL
 299                 && !OSSL_PARAM_get_octet_string(p, (void **)&q,
 300                                                 HKDF_MAXBUF - ctx->info_len,
 301                                                 &sz))
 302                 return 0;
 303             ctx->info_len += sz;
 304         }
 305     }
 306     return 1;
 307 }
 308
 309 static const OSSL_PARAM *kdf_hkdf_settable_ctx_params(ossl_unused void *ctx,
 310                                                       ossl_unused void *provctx)
 311 {
 312     static const OSSL_PARAM known_settable_ctx_params[] = {
 313         HKDF_COMMON_SETTABLES,
 314         OSSL_PARAM_octet_string(OSSL_KDF_PARAM_INFO, NULL, 0),
 315         OSSL_PARAM_END
 316     };
 317     return known_settable_ctx_params;
 318 }
 319
 320 static int kdf_hkdf_get_ctx_params(void *vctx, OSSL_PARAM params[])
 321 {
 322     KDF_HKDF *ctx = (KDF_HKDF *)vctx;
 323     OSSL_PARAM *p;
 324
 325     if ((p = OSSL_PARAM_locate(params, OSSL_KDF_PARAM_SIZE)) != NULL) {
 326         size_t sz = kdf_hkdf_size(ctx);
 327
 328         if (sz == 0)
 329             return 0;
 330         return OSSL_PARAM_set_size_t(p, sz);
 331     }
 332     return -2;
 333 }
 334
 335 static const OSSL_PARAM *kdf_hkdf_gettable_ctx_params(ossl_unused void *ctx,
 336                                                       ossl_unused void *provctx)
 337 {
 338     static const OSSL_PARAM known_gettable_ctx_params[] = {
 339         OSSL_PARAM_size_t(OSSL_KDF_PARAM_SIZE, NULL),
 340         OSSL_PARAM_END
 341     };
 342     return known_gettable_ctx_params;
 343 }
 344
 345 const OSSL_DISPATCH ossl_kdf_hkdf_functions[] = {
 346     { OSSL_FUNC_KDF_NEWCTX, (void(*)(void))kdf_hkdf_new },
 347     { OSSL_FUNC_KDF_DUPCTX, (void(*)(void))kdf_hkdf_dup },
 348     { OSSL_FUNC_KDF_FREECTX, (void(*)(void))kdf_hkdf_free },
 349     { OSSL_FUNC_KDF_RESET, (void(*)(void))kdf_hkdf_reset },
 350     { OSSL_FUNC_KDF_DERIVE, (void(*)(void))kdf_hkdf_derive },
 351     { OSSL_FUNC_KDF_SETTABLE_CTX_PARAMS,
 352       (void(*)(void))kdf_hkdf_settable_ctx_params },
 353     { OSSL_FUNC_KDF_SET_CTX_PARAMS, (void(*)(void))kdf_hkdf_set_ctx_params },
 354     { OSSL_FUNC_KDF_GETTABLE_CTX_PARAMS,
 355       (void(*)(void))kdf_hkdf_gettable_ctx_params },
 356     { OSSL_FUNC_KDF_GET_CTX_PARAMS, (void(*)(void))kdf_hkdf_get_ctx_params },
 357     { 0, NULL }
 358 };
 359
 360 /*
 361  * Refer to "HMAC-based Extract-and-Expand Key Derivation Function (HKDF)"
 362  * Section 2 (https://tools.ietf.org/html/rfc5869#section-2) and
 363  * "Cryptographic Extraction and Key Derivation: The HKDF Scheme"
 364  * Section 4.2 (https://eprint.iacr.org/2010/264.pdf).
 365  *
 366  * From the paper:
 367  *   The scheme HKDF is specified as:
 368  *     HKDF(XTS, SKM, CTXinfo, L) = K(1) | K(2) | ... | K(t)
 369  *
 370  *     where:
 371  *       SKM is source key material
 372  *       XTS is extractor salt (which may be null or constant)
 373  *       CTXinfo is context information (may be null)
 374  *       L is the number of key bits to be produced by KDF
 375  *       k is the output length in bits of the hash function used with HMAC
 376  *       t = ceil(L/k)
 377  *       the value K(t) is truncated to its first d = L mod k bits.
 378  *
 379  * From RFC 5869:
 380  *   2.2.  Step 1: Extract
 381  *     HKDF-Extract(salt, IKM) -> PRK
 382  *   2.3.  Step 2: Expand
 383  *     HKDF-Expand(PRK, info, L) -> OKM
 384  */
 385 static int HKDF(OSSL_LIB_CTX *libctx, const EVP_MD *evp_md,
 386                 const unsigned char *salt, size_t salt_len,
 387                 const unsigned char *ikm, size_t ikm_len,
 388                 const unsigned char *info, size_t info_len,
 389                 unsigned char *okm, size_t okm_len)
 390 {
 391     unsigned char prk[EVP_MAX_MD_SIZE];
 392     int ret, sz;
 393     size_t prk_len;
 394
 395     sz = EVP_MD_get_size(evp_md);
 396     if (sz < 0)
 397         return 0;
 398     prk_len = (size_t)sz;
 399
 400     /* Step 1: HKDF-Extract(salt, IKM) -> PRK */
 401     if (!HKDF_Extract(libctx, evp_md,
 402                       salt, salt_len, ikm, ikm_len, prk, prk_len))
 403         return 0;
 404
 405     /* Step 2: HKDF-Expand(PRK, info, L) -> OKM */
 406     ret = HKDF_Expand(evp_md, prk, prk_len, info, info_len, okm, okm_len);
 407     OPENSSL_cleanse(prk, sizeof(prk));
 408
 409     return ret;
 410 }
 411
 412 /*
 413  * Refer to "HMAC-based Extract-and-Expand Key Derivation Function (HKDF)"
 414  * Section 2.2 (https://tools.ietf.org/html/rfc5869#section-2.2).
 415  *
 416  * 2.2.  Step 1: Extract
 417  *
 418  *   HKDF-Extract(salt, IKM) -> PRK
 419  *
 420  *   Options:
 421  *      Hash     a hash function; HashLen denotes the length of the
 422  *               hash function output in octets
 423  *
 424  *   Inputs:
 425  *      salt     optional salt value (a non-secret random value);
 426  *               if not provided, it is set to a string of HashLen zeros.
 427  *      IKM      input keying material
 428  *
 429  *   Output:
 430  *      PRK      a pseudorandom key (of HashLen octets)
 431  *
 432  *   The output PRK is calculated as follows:
 433  *
 434  *   PRK = HMAC-Hash(salt, IKM)
 435  */
 436 static int HKDF_Extract(OSSL_LIB_CTX *libctx, const EVP_MD *evp_md,
 437                         const unsigned char *salt, size_t salt_len,
 438                         const unsigned char *ikm, size_t ikm_len,
 439                         unsigned char *prk, size_t prk_len)
 440 {
 441     int sz = EVP_MD_get_size(evp_md);
 442
 443     if (sz < 0)
 444         return 0;
 445     if (prk_len != (size_t)sz) {
 446         ERR_raise(ERR_LIB_PROV, PROV_R_WRONG_OUTPUT_BUFFER_SIZE);
 447         return 0;
 448     }
 449     /* calc: PRK = HMAC-Hash(salt, IKM) */
 450     return
 451         EVP_Q_mac(libctx, "HMAC", NULL, EVP_MD_get0_name(evp_md), NULL, salt,
 452                   salt_len, ikm, ikm_len, prk, EVP_MD_get_size(evp_md), NULL)
 453         != NULL;
 454 }
 455
 456 /*
 457  * Refer to "HMAC-based Extract-and-Expand Key Derivation Function (HKDF)"
 458  * Section 2.3 (https://tools.ietf.org/html/rfc5869#section-2.3).
 459  *
 460  * 2.3.  Step 2: Expand
 461  *
 462  *   HKDF-Expand(PRK, info, L) -> OKM
 463  *
 464  *   Options:
 465  *      Hash     a hash function; HashLen denotes the length of the
 466  *               hash function output in octets
 467  *
 468  *   Inputs:
 469  *      PRK      a pseudorandom key of at least HashLen octets
 470  *               (usually, the output from the extract step)
 471  *      info     optional context and application specific information
 472  *               (can be a zero-length string)
 473  *      L        length of output keying material in octets
 474  *               (<= 255*HashLen)
 475  *
 476  *   Output:
 477  *      OKM      output keying material (of L octets)
 478  *
 479  *   The output OKM is calculated as follows:
 480  *
 481  *   N = ceil(L/HashLen)
 482  *   T = T(1) | T(2) | T(3) | ... | T(N)
 483  *   OKM = first L octets of T
 484  *
 485  *   where:
 486  *   T(0) = empty string (zero length)
 487  *   T(1) = HMAC-Hash(PRK, T(0) | info | 0x01)
 488  *   T(2) = HMAC-Hash(PRK, T(1) | info | 0x02)
 489  *   T(3) = HMAC-Hash(PRK, T(2) | info | 0x03)
 490  *   ...
 491  *
 492  *   (where the constant concatenated to the end of each T(n) is a
 493  *   single octet.)
 494  */
 495 static int HKDF_Expand(const EVP_MD *evp_md,
 496                        const unsigned char *prk, size_t prk_len,
 497                        const unsigned char *info, size_t info_len,
 498                        unsigned char *okm, size_t okm_len)
 499 {
 500     HMAC_CTX *hmac;
 501     int ret = 0, sz;
 502     unsigned int i;
 503     unsigned char prev[EVP_MAX_MD_SIZE];
 504     size_t done_len = 0, dig_len, n;
 505
 506     sz = EVP_MD_get_size(evp_md);
 507     if (sz <= 0)
 508         return 0;
 509     dig_len = (size_t)sz;
 510
 511     /* calc: N = ceil(L/HashLen) */
 512     n = okm_len / dig_len;
 513     if (okm_len % dig_len)
 514         n++;
 515
 516     if (n > 255 || okm == NULL)
 517         return 0;
 518
 519     if ((hmac = HMAC_CTX_new()) == NULL)
 520         return 0;
 521
 522     if (!HMAC_Init_ex(hmac, prk, prk_len, evp_md, NULL))
 523         goto err;
 524
 525     for (i = 1; i <= n; i++) {
 526         size_t copy_len;
 527         const unsigned char ctr = i;
 528
 529         /* calc: T(i) = HMAC-Hash(PRK, T(i - 1) | info | i) */
 530         if (i > 1) {
 531             if (!HMAC_Init_ex(hmac, NULL, 0, NULL, NULL))
 532                 goto err;
 533
 534             if (!HMAC_Update(hmac, prev, dig_len))
 535                 goto err;
 536         }
 537
 538         if (!HMAC_Update(hmac, info, info_len))
 539             goto err;
 540
 541         if (!HMAC_Update(hmac, &ctr, 1))
 542             goto err;
 543
 544         if (!HMAC_Final(hmac, prev, NULL))
 545             goto err;
 546
 547         copy_len = (done_len + dig_len > okm_len) ?
 548                        okm_len - done_len :
 549                        dig_len;
 550
 551         memcpy(okm + done_len, prev, copy_len);
 552
 553         done_len += copy_len;
 554     }
 555     ret = 1;
 556
 557  err:
 558     OPENSSL_cleanse(prev, sizeof(prev));
 559     HMAC_CTX_free(hmac);
 560     return ret;
 561 }
 562
 563 /*
 564  * TLS uses slight variations of the above and for FIPS validation purposes,
 565  * they need to be present here.
 566  * Refer to RFC 8446 section 7 for specific details.
 567  */
 568
 569 /*
 570  * Given a |secret|; a |label| of length |labellen|; and |data| of length
 571  * |datalen| (e.g. typically a hash of the handshake messages), derive a new
 572  * secret |outlen| bytes long and store it in the location pointed to be |out|.
 573  * The |data| value may be zero length. Returns 1 on success and 0 on failure.
 574  */
 575 static int prov_tls13_hkdf_expand(const EVP_MD *md,
 576                                   const unsigned char *key, size_t keylen,
 577                                   const unsigned char *prefix, size_t prefixlen,
 578                                   const unsigned char *label, size_t labellen,
 579                                   const unsigned char *data, size_t datalen,
 580                                   unsigned char *out, size_t outlen)
 581 {
 582     size_t hkdflabellen;
 583     unsigned char hkdflabel[HKDF_MAXBUF];
 584     WPACKET pkt;
 585
 586     /*
 587      * 2 bytes for length of derived secret + 1 byte for length of combined
 588      * prefix and label + bytes for the label itself + 1 byte length of hash
 589      * + bytes for the hash itself.  We've got the maximum the KDF can handle
 590      * which should always be sufficient.
 591      */
 592     if (!WPACKET_init_static_len(&pkt, hkdflabel, sizeof(hkdflabel), 0)
 593             || !WPACKET_put_bytes_u16(&pkt, outlen)
 594             || !WPACKET_start_sub_packet_u8(&pkt)
 595             || !WPACKET_memcpy(&pkt, prefix, prefixlen)
 596             || !WPACKET_memcpy(&pkt, label, labellen)
 597             || !WPACKET_close(&pkt)
 598             || !WPACKET_sub_memcpy_u8(&pkt, data, (data == NULL) ? 0 : datalen)
 599             || !WPACKET_get_total_written(&pkt, &hkdflabellen)
 600             || !WPACKET_finish(&pkt)) {
 601         WPACKET_cleanup(&pkt);
 602         return 0;
 603     }
 604
 605     return HKDF_Expand(md, key, keylen, hkdflabel, hkdflabellen,
 606                        out, outlen);
 607 }
 608
 609 static int prov_tls13_hkdf_generate_secret(OSSL_LIB_CTX *libctx,
 610                                            const EVP_MD *md,
 611                                            const unsigned char *prevsecret,
 612                                            size_t prevsecretlen,
 613                                            const unsigned char *insecret,
 614                                            size_t insecretlen,
 615                                            const unsigned char *prefix,
 616                                            size_t prefixlen,
 617                                            const unsigned char *label,
 618                                            size_t labellen,
 619                                            unsigned char *out, size_t outlen)
 620 {
 621     size_t mdlen;
 622     int ret;
 623     unsigned char preextractsec[EVP_MAX_MD_SIZE];
 624     /* Always filled with zeros */
 625     static const unsigned char default_zeros[EVP_MAX_MD_SIZE];
 626
 627     ret = EVP_MD_get_size(md);
 628     /* Ensure cast to size_t is safe */
 629     if (ret <= 0)
 630         return 0;
 631     mdlen = (size_t)ret;
 632
 633     if (insecret == NULL) {
 634         insecret = default_zeros;
 635         insecretlen = mdlen;
 636     }
 637     if (prevsecret == NULL) {
 638         prevsecret = default_zeros;
 639         prevsecretlen = 0;
 640     } else {
 641         EVP_MD_CTX *mctx = EVP_MD_CTX_new();
 642         unsigned char hash[EVP_MAX_MD_SIZE];
 643
 644         /* The pre-extract derive step uses a hash of no messages */
 645         if (mctx == NULL
 646                 || EVP_DigestInit_ex(mctx, md, NULL) <= 0
 647                 || EVP_DigestFinal_ex(mctx, hash, NULL) <= 0) {
 648             EVP_MD_CTX_free(mctx);
 649             return 0;
 650         }
 651         EVP_MD_CTX_free(mctx);
 652
 653         /* Generate the pre-extract secret */
 654         if (!prov_tls13_hkdf_expand(md, prevsecret, mdlen,
 655                                     prefix, prefixlen, label, labellen,
 656                                     hash, mdlen, preextractsec, mdlen))
 657             return 0;
 658         prevsecret = preextractsec;
 659         prevsecretlen = mdlen;
 660     }
 661
 662     ret = HKDF_Extract(libctx, md, prevsecret, prevsecretlen,
 663                        insecret, insecretlen, out, outlen);
 664
 665     if (prevsecret == preextractsec)
 666         OPENSSL_cleanse(preextractsec, mdlen);
 667     return ret;
 668 }
 669
 670 static int kdf_tls1_3_derive(void *vctx, unsigned char *key, size_t keylen,
 671                              const OSSL_PARAM params[])
 672 {
 673     KDF_HKDF *ctx = (KDF_HKDF *)vctx;
 674     const EVP_MD *md;
 675
 676     if (!ossl_prov_is_running() || !kdf_tls1_3_set_ctx_params(ctx, params))
 677         return 0;
 678
 679     md = ossl_prov_digest_md(&ctx->digest);
 680     if (md == NULL) {
 681         ERR_raise(ERR_LIB_PROV, PROV_R_MISSING_MESSAGE_DIGEST);
 682         return 0;
 683     }
 684
 685     switch (ctx->mode) {
 686     default:
 687         return 0;
 688
 689     case EVP_KDF_HKDF_MODE_EXTRACT_ONLY:
 690         return prov_tls13_hkdf_generate_secret(PROV_LIBCTX_OF(ctx->provctx),
 691                                                md,
 692                                                ctx->salt, ctx->salt_len,
 693                                                ctx->key, ctx->key_len,
 694                                                ctx->prefix, ctx->prefix_len,
 695                                                ctx->label, ctx->label_len,
 696                                                key, keylen);
 697
 698     case EVP_KDF_HKDF_MODE_EXPAND_ONLY:
 699         return prov_tls13_hkdf_expand(md, ctx->key, ctx->key_len,
 700                                       ctx->prefix, ctx->prefix_len,
 701                                       ctx->label, ctx->label_len,
 702                                       ctx->data, ctx->data_len,
 703                                       key, keylen);
 704     }
 705 }
 706
 707 static int kdf_tls1_3_set_ctx_params(void *vctx, const OSSL_PARAM params[])
 708 {
 709     const OSSL_PARAM *p;
 710     KDF_HKDF *ctx = vctx;
 711
 712     if (params == NULL)
 713         return 1;
 714
 715     if (!hkdf_common_set_ctx_params(ctx, params))
 716         return 0;
 717
 718     if (ctx->mode == EVP_KDF_HKDF_MODE_EXTRACT_AND_EXPAND) {
 719         ERR_raise(ERR_LIB_PROV, PROV_R_INVALID_MODE);
 720         return 0;
 721     }
 722
 723     if ((p = OSSL_PARAM_locate_const(params, OSSL_KDF_PARAM_PREFIX)) != NULL) {
 724         OPENSSL_free(ctx->prefix);
 725         ctx->prefix = NULL;
 726         if (!OSSL_PARAM_get_octet_string(p, (void **)&ctx->prefix, 0,
 727                                          &ctx->prefix_len))
 728             return 0;
 729     }
 730
 731     if ((p = OSSL_PARAM_locate_const(params, OSSL_KDF_PARAM_LABEL)) != NULL) {
 732         OPENSSL_free(ctx->label);
 733         ctx->label = NULL;
 734         if (!OSSL_PARAM_get_octet_string(p, (void **)&ctx->label, 0,
 735                                          &ctx->label_len))
 736             return 0;
 737     }
 738
 739     OPENSSL_clear_free(ctx->data, ctx->data_len);
 740     ctx->data = NULL;
 741     if ((p = OSSL_PARAM_locate_const(params, OSSL_KDF_PARAM_DATA)) != NULL
 742             && !OSSL_PARAM_get_octet_string(p, (void **)&ctx->data, 0,
 743                                             &ctx->data_len))
 744         return 0;
 745     return 1;
 746 }
 747
 748 static const OSSL_PARAM *kdf_tls1_3_settable_ctx_params(ossl_unused void *ctx,
 749                                                         ossl_unused void *provctx)
 750 {
 751     static const OSSL_PARAM known_settable_ctx_params[] = {
 752         HKDF_COMMON_SETTABLES,
 753         OSSL_PARAM_octet_string(OSSL_KDF_PARAM_PREFIX, NULL, 0),
 754         OSSL_PARAM_octet_string(OSSL_KDF_PARAM_LABEL, NULL, 0),
 755         OSSL_PARAM_octet_string(OSSL_KDF_PARAM_DATA, NULL, 0),
 756         OSSL_PARAM_END
 757     };
 758     return known_settable_ctx_params;
 759 }
 760
 761 const OSSL_DISPATCH ossl_kdf_tls1_3_kdf_functions[] = {
 762     { OSSL_FUNC_KDF_NEWCTX, (void(*)(void))kdf_hkdf_new },
 763     { OSSL_FUNC_KDF_DUPCTX, (void(*)(void))kdf_hkdf_dup },
 764     { OSSL_FUNC_KDF_FREECTX, (void(*)(void))kdf_hkdf_free },
 765     { OSSL_FUNC_KDF_RESET, (void(*)(void))kdf_hkdf_reset },
 766     { OSSL_FUNC_KDF_DERIVE, (void(*)(void))kdf_tls1_3_derive },
 767     { OSSL_FUNC_KDF_SETTABLE_CTX_PARAMS,
 768       (void(*)(void))kdf_tls1_3_settable_ctx_params },
 769     { OSSL_FUNC_KDF_SET_CTX_PARAMS, (void(*)(void))kdf_tls1_3_set_ctx_params },
 770     { OSSL_FUNC_KDF_GETTABLE_CTX_PARAMS,
 771       (void(*)(void))kdf_hkdf_gettable_ctx_params },
 772     { OSSL_FUNC_KDF_GET_CTX_PARAMS, (void(*)(void))kdf_hkdf_get_ctx_params },
 773     { 0, NULL }
 774 };