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 #define HKDF_MAXINFO (32*1024)
  36
  37 static OSSL_FUNC_kdf_newctx_fn kdf_hkdf_new;
  38 static OSSL_FUNC_kdf_dupctx_fn kdf_hkdf_dup;
  39 static OSSL_FUNC_kdf_freectx_fn kdf_hkdf_free;
  40 static OSSL_FUNC_kdf_reset_fn kdf_hkdf_reset;
  41 static OSSL_FUNC_kdf_derive_fn kdf_hkdf_derive;
  42 static OSSL_FUNC_kdf_settable_ctx_params_fn kdf_hkdf_settable_ctx_params;
  43 static OSSL_FUNC_kdf_set_ctx_params_fn kdf_hkdf_set_ctx_params;
  44 static OSSL_FUNC_kdf_gettable_ctx_params_fn kdf_hkdf_gettable_ctx_params;
  45 static OSSL_FUNC_kdf_get_ctx_params_fn kdf_hkdf_get_ctx_params;
  46 static OSSL_FUNC_kdf_derive_fn kdf_tls1_3_derive;
  47 static OSSL_FUNC_kdf_settable_ctx_params_fn kdf_tls1_3_settable_ctx_params;
  48 static OSSL_FUNC_kdf_set_ctx_params_fn kdf_tls1_3_set_ctx_params;
  49
  50 static int HKDF(OSSL_LIB_CTX *libctx, const EVP_MD *evp_md,
  51                 const unsigned char *salt, size_t salt_len,
  52                 const unsigned char *key, size_t key_len,
  53                 const unsigned char *info, size_t info_len,
  54                 unsigned char *okm, size_t okm_len);
  55 static int HKDF_Extract(OSSL_LIB_CTX *libctx, const EVP_MD *evp_md,
  56                         const unsigned char *salt, size_t salt_len,
  57                         const unsigned char *ikm, size_t ikm_len,
  58                         unsigned char *prk, size_t prk_len);
  59 static int HKDF_Expand(const EVP_MD *evp_md,
  60                        const unsigned char *prk, size_t prk_len,
  61                        const unsigned char *info, size_t info_len,
  62                        unsigned char *okm, size_t okm_len);
  63
  64 /* Settable context parameters that are common across HKDF and the TLS KDF */
  65 #define HKDF_COMMON_SETTABLES                                           \
  66         OSSL_PARAM_utf8_string(OSSL_KDF_PARAM_MODE, NULL, 0),           \
  67         OSSL_PARAM_int(OSSL_KDF_PARAM_MODE, NULL),                      \
  68         OSSL_PARAM_utf8_string(OSSL_KDF_PARAM_PROPERTIES, NULL, 0),     \
  69         OSSL_PARAM_utf8_string(OSSL_KDF_PARAM_DIGEST, NULL, 0),         \
  70         OSSL_PARAM_octet_string(OSSL_KDF_PARAM_KEY, NULL, 0),           \
  71         OSSL_PARAM_octet_string(OSSL_KDF_PARAM_SALT, NULL, 0)
  72
  73 typedef struct {
  74     void *provctx;
  75     int mode;
  76     PROV_DIGEST digest;
  77     unsigned char *salt;
  78     size_t salt_len;
  79     unsigned char *key;
  80     size_t key_len;
  81     unsigned char *prefix;
  82     size_t prefix_len;
  83     unsigned char *label;
  84     size_t label_len;
  85     unsigned char *data;
  86     size_t data_len;
  87     unsigned char *info;
  88     size_t info_len;
  89 } KDF_HKDF;
  90
  91 static void *kdf_hkdf_new(void *provctx)
  92 {
  93     KDF_HKDF *ctx;
  94
  95     if (!ossl_prov_is_running())
  96         return NULL;
  97
  98     if ((ctx = OPENSSL_zalloc(sizeof(*ctx))) != NULL)
  99         ctx->provctx = provctx;
 100     return ctx;
 101 }
 102
 103 static void kdf_hkdf_free(void *vctx)
 104 {
 105     KDF_HKDF *ctx = (KDF_HKDF *)vctx;
 106
 107     if (ctx != NULL) {
 108         kdf_hkdf_reset(ctx);
 109         OPENSSL_free(ctx);
 110     }
 111 }
 112
 113 static void kdf_hkdf_reset(void *vctx)
 114 {
 115     KDF_HKDF *ctx = (KDF_HKDF *)vctx;
 116     void *provctx = ctx->provctx;
 117
 118     ossl_prov_digest_reset(&ctx->digest);
 119     OPENSSL_free(ctx->salt);
 120     OPENSSL_free(ctx->prefix);
 121     OPENSSL_free(ctx->label);
 122     OPENSSL_clear_free(ctx->data, ctx->data_len);
 123     OPENSSL_clear_free(ctx->key, ctx->key_len);
 124     OPENSSL_clear_free(ctx->info, ctx->info_len);
 125     memset(ctx, 0, sizeof(*ctx));
 126     ctx->provctx = provctx;
 127 }
 128
 129 static void *kdf_hkdf_dup(void *vctx)
 130 {
 131     const KDF_HKDF *src = (const KDF_HKDF *)vctx;
 132     KDF_HKDF *dest;
 133
 134     dest = kdf_hkdf_new(src->provctx);
 135     if (dest != NULL) {
 136         if (!ossl_prov_memdup(src->salt, src->salt_len, &dest->salt,
 137                               &dest->salt_len)
 138                 || !ossl_prov_memdup(src->key, src->key_len,
 139                                      &dest->key , &dest->key_len)
 140                 || !ossl_prov_memdup(src->prefix, src->prefix_len,
 141                                      &dest->prefix, &dest->prefix_len)
 142                 || !ossl_prov_memdup(src->label, src->label_len,
 143                                      &dest->label, &dest->label_len)
 144                 || !ossl_prov_memdup(src->data, src->data_len,
 145                                      &dest->data, &dest->data_len)
 146                 || !ossl_prov_memdup(src->info, src->info_len,
 147                                      &dest->info, &dest->info_len)
 148                 || !ossl_prov_digest_copy(&dest->digest, &src->digest))
 149             goto err;
 150         dest->mode = src->mode;
 151     }
 152     return dest;
 153
 154  err:
 155     kdf_hkdf_free(dest);
 156     return NULL;
 157 }
 158
 159 static size_t kdf_hkdf_size(KDF_HKDF *ctx)
 160 {
 161     int sz;
 162     const EVP_MD *md = ossl_prov_digest_md(&ctx->digest);
 163
 164     if (ctx->mode != EVP_KDF_HKDF_MODE_EXTRACT_ONLY)
 165         return SIZE_MAX;
 166
 167     if (md == NULL) {
 168         ERR_raise(ERR_LIB_PROV, PROV_R_MISSING_MESSAGE_DIGEST);
 169         return 0;
 170     }
 171     sz = EVP_MD_get_size(md);
 172     if (sz < 0)
 173         return 0;
 174
 175     return sz;
 176 }
 177
 178 static int kdf_hkdf_derive(void *vctx, unsigned char *key, size_t keylen,
 179                            const OSSL_PARAM params[])
 180 {
 181     KDF_HKDF *ctx = (KDF_HKDF *)vctx;
 182     OSSL_LIB_CTX *libctx = PROV_LIBCTX_OF(ctx->provctx);
 183     const EVP_MD *md;
 184
 185     if (!ossl_prov_is_running() || !kdf_hkdf_set_ctx_params(ctx, params))
 186         return 0;
 187
 188     md = ossl_prov_digest_md(&ctx->digest);
 189     if (md == NULL) {
 190         ERR_raise(ERR_LIB_PROV, PROV_R_MISSING_MESSAGE_DIGEST);
 191         return 0;
 192     }
 193     if (ctx->key == NULL) {
 194         ERR_raise(ERR_LIB_PROV, PROV_R_MISSING_KEY);
 195         return 0;
 196     }
 197     if (keylen == 0) {
 198         ERR_raise(ERR_LIB_PROV, PROV_R_INVALID_KEY_LENGTH);
 199         return 0;
 200     }
 201
 202     switch (ctx->mode) {
 203     case EVP_KDF_HKDF_MODE_EXTRACT_AND_EXPAND:
 204     default:
 205         return HKDF(libctx, md, ctx->salt, ctx->salt_len,
 206                     ctx->key, ctx->key_len, ctx->info, ctx->info_len, key, keylen);
 207
 208     case EVP_KDF_HKDF_MODE_EXTRACT_ONLY:
 209         return HKDF_Extract(libctx, md, ctx->salt, ctx->salt_len,
 210                             ctx->key, ctx->key_len, key, keylen);
 211
 212     case EVP_KDF_HKDF_MODE_EXPAND_ONLY:
 213         return HKDF_Expand(md, ctx->key, ctx->key_len, ctx->info,
 214                            ctx->info_len, key, keylen);
 215     }
 216 }
 217
 218 static int hkdf_common_set_ctx_params(KDF_HKDF *ctx, const OSSL_PARAM params[])
 219 {
 220     OSSL_LIB_CTX *libctx = PROV_LIBCTX_OF(ctx->provctx);
 221     const OSSL_PARAM *p;
 222     int n;
 223
 224     if (params == NULL)
 225         return 1;
 226
 227     if (!ossl_prov_digest_load_from_params(&ctx->digest, params, libctx))
 228         return 0;
 229
 230     if ((p = OSSL_PARAM_locate_const(params, OSSL_KDF_PARAM_MODE)) != NULL) {
 231         if (p->data_type == OSSL_PARAM_UTF8_STRING) {
 232             if (OPENSSL_strcasecmp(p->data, "EXTRACT_AND_EXPAND") == 0) {
 233                 ctx->mode = EVP_KDF_HKDF_MODE_EXTRACT_AND_EXPAND;
 234             } else if (OPENSSL_strcasecmp(p->data, "EXTRACT_ONLY") == 0) {
 235                 ctx->mode = EVP_KDF_HKDF_MODE_EXTRACT_ONLY;
 236             } else if (OPENSSL_strcasecmp(p->data, "EXPAND_ONLY") == 0) {
 237                 ctx->mode = EVP_KDF_HKDF_MODE_EXPAND_ONLY;
 238             } else {
 239                 ERR_raise(ERR_LIB_PROV, PROV_R_INVALID_MODE);
 240                 return 0;
 241             }
 242         } else if (OSSL_PARAM_get_int(p, &n)) {
 243             if (n != EVP_KDF_HKDF_MODE_EXTRACT_AND_EXPAND
 244                 && n != EVP_KDF_HKDF_MODE_EXTRACT_ONLY
 245                 && n != EVP_KDF_HKDF_MODE_EXPAND_ONLY) {
 246                 ERR_raise(ERR_LIB_PROV, PROV_R_INVALID_MODE);
 247                 return 0;
 248             }
 249             ctx->mode = n;
 250         } else {
 251             ERR_raise(ERR_LIB_PROV, PROV_R_INVALID_MODE);
 252             return 0;
 253         }
 254     }
 255
 256     if ((p = OSSL_PARAM_locate_const(params, OSSL_KDF_PARAM_KEY)) != NULL) {
 257         OPENSSL_clear_free(ctx->key, ctx->key_len);
 258         ctx->key = NULL;
 259         if (!OSSL_PARAM_get_octet_string(p, (void **)&ctx->key, 0,
 260                                          &ctx->key_len))
 261             return 0;
 262     }
 263
 264     if ((p = OSSL_PARAM_locate_const(params, OSSL_KDF_PARAM_SALT)) != NULL) {
 265         if (p->data_size != 0 && p->data != NULL) {
 266             OPENSSL_free(ctx->salt);
 267             ctx->salt = NULL;
 268             if (!OSSL_PARAM_get_octet_string(p, (void **)&ctx->salt, 0,
 269                                              &ctx->salt_len))
 270                 return 0;
 271         }
 272     }
 273
 274     return 1;
 275 }
 276
 277 /*
 278  * Use WPACKET to concat one or more OSSL_KDF_PARAM_INFO fields into a fixed
 279  * out buffer of size *outlen.
 280  * If out is NULL then outlen is used to return the required buffer size.
 281  */
 282 static int setinfo_fromparams(const OSSL_PARAM *p, unsigned char *out, size_t *outlen)
 283 {
 284     int ret = 0;
 285     WPACKET pkt;
 286
 287     if (out == NULL) {
 288         if (!WPACKET_init_null(&pkt, 0))
 289             return 0;
 290     } else {
 291         if (!WPACKET_init_static_len(&pkt, out, *outlen, 0))
 292             return 0;
 293     }
 294
 295     for (; p != NULL; p = OSSL_PARAM_locate_const(p + 1, OSSL_KDF_PARAM_INFO)) {
 296         if (p->data_type != OSSL_PARAM_OCTET_STRING)
 297             goto err;
 298         if (p->data != NULL
 299                 && p->data_size != 0
 300                 && !WPACKET_memcpy(&pkt, p->data, p->data_size))
 301             goto err;
 302     }
 303     if (!WPACKET_get_total_written(&pkt, outlen)
 304             || !WPACKET_finish(&pkt))
 305         goto err;
 306     ret = 1;
 307 err:
 308     WPACKET_cleanup(&pkt);
 309     return ret;
 310 }
 311
 312 static int kdf_hkdf_set_ctx_params(void *vctx, const OSSL_PARAM params[])
 313 {
 314     const OSSL_PARAM *p;
 315     KDF_HKDF *ctx = vctx;
 316
 317     if (params == NULL)
 318         return 1;
 319
 320     if (!hkdf_common_set_ctx_params(ctx, params))
 321         return 0;
 322
 323     /* The info fields concatenate, so process them all */
 324     if ((p = OSSL_PARAM_locate_const(params, OSSL_KDF_PARAM_INFO)) != NULL) {
 325         size_t sz = 0;
 326
 327         /* calculate the total size */
 328         if (!setinfo_fromparams(p, NULL, &sz))
 329             return 0;
 330         if (sz > HKDF_MAXINFO)
 331             return 0;
 332
 333         OPENSSL_clear_free(ctx->info, ctx->info_len);
 334         ctx->info = NULL;
 335         if (sz == 0)
 336             return 1;
 337         /* Alloc the buffer */
 338         ctx->info = OPENSSL_malloc(sz);
 339         if (ctx->info == NULL)
 340             return 0;
 341         ctx->info_len = sz;
 342         /* Concat one or more OSSL_KDF_PARAM_INFO fields */
 343         if (!setinfo_fromparams(p, ctx->info, &sz))
 344             return 0;
 345     }
 346     return 1;
 347 }
 348
 349 static const OSSL_PARAM *kdf_hkdf_settable_ctx_params(ossl_unused void *ctx,
 350                                                       ossl_unused void *provctx)
 351 {
 352     static const OSSL_PARAM known_settable_ctx_params[] = {
 353         HKDF_COMMON_SETTABLES,
 354         OSSL_PARAM_octet_string(OSSL_KDF_PARAM_INFO, NULL, 0),
 355         OSSL_PARAM_END
 356     };
 357     return known_settable_ctx_params;
 358 }
 359
 360 static int kdf_hkdf_get_ctx_params(void *vctx, OSSL_PARAM params[])
 361 {
 362     KDF_HKDF *ctx = (KDF_HKDF *)vctx;
 363     OSSL_PARAM *p;
 364
 365     if ((p = OSSL_PARAM_locate(params, OSSL_KDF_PARAM_SIZE)) != NULL) {
 366         size_t sz = kdf_hkdf_size(ctx);
 367
 368         if (sz == 0)
 369             return 0;
 370         return OSSL_PARAM_set_size_t(p, sz);
 371     }
 372     return -2;
 373 }
 374
 375 static const OSSL_PARAM *kdf_hkdf_gettable_ctx_params(ossl_unused void *ctx,
 376                                                       ossl_unused void *provctx)
 377 {
 378     static const OSSL_PARAM known_gettable_ctx_params[] = {
 379         OSSL_PARAM_size_t(OSSL_KDF_PARAM_SIZE, NULL),
 380         OSSL_PARAM_END
 381     };
 382     return known_gettable_ctx_params;
 383 }
 384
 385 const OSSL_DISPATCH ossl_kdf_hkdf_functions[] = {
 386     { OSSL_FUNC_KDF_NEWCTX, (void(*)(void))kdf_hkdf_new },
 387     { OSSL_FUNC_KDF_DUPCTX, (void(*)(void))kdf_hkdf_dup },
 388     { OSSL_FUNC_KDF_FREECTX, (void(*)(void))kdf_hkdf_free },
 389     { OSSL_FUNC_KDF_RESET, (void(*)(void))kdf_hkdf_reset },
 390     { OSSL_FUNC_KDF_DERIVE, (void(*)(void))kdf_hkdf_derive },
 391     { OSSL_FUNC_KDF_SETTABLE_CTX_PARAMS,
 392       (void(*)(void))kdf_hkdf_settable_ctx_params },
 393     { OSSL_FUNC_KDF_SET_CTX_PARAMS, (void(*)(void))kdf_hkdf_set_ctx_params },
 394     { OSSL_FUNC_KDF_GETTABLE_CTX_PARAMS,
 395       (void(*)(void))kdf_hkdf_gettable_ctx_params },
 396     { OSSL_FUNC_KDF_GET_CTX_PARAMS, (void(*)(void))kdf_hkdf_get_ctx_params },
 397     OSSL_DISPATCH_END
 398 };
 399
 400 /*
 401  * Refer to "HMAC-based Extract-and-Expand Key Derivation Function (HKDF)"
 402  * Section 2 (https://tools.ietf.org/html/rfc5869#section-2) and
 403  * "Cryptographic Extraction and Key Derivation: The HKDF Scheme"
 404  * Section 4.2 (https://eprint.iacr.org/2010/264.pdf).
 405  *
 406  * From the paper:
 407  *   The scheme HKDF is specified as:
 408  *     HKDF(XTS, SKM, CTXinfo, L) = K(1) | K(2) | ... | K(t)
 409  *
 410  *     where:
 411  *       SKM is source key material
 412  *       XTS is extractor salt (which may be null or constant)
 413  *       CTXinfo is context information (may be null)
 414  *       L is the number of key bits to be produced by KDF
 415  *       k is the output length in bits of the hash function used with HMAC
 416  *       t = ceil(L/k)
 417  *       the value K(t) is truncated to its first d = L mod k bits.
 418  *
 419  * From RFC 5869:
 420  *   2.2.  Step 1: Extract
 421  *     HKDF-Extract(salt, IKM) -> PRK
 422  *   2.3.  Step 2: Expand
 423  *     HKDF-Expand(PRK, info, L) -> OKM
 424  */
 425 static int HKDF(OSSL_LIB_CTX *libctx, const EVP_MD *evp_md,
 426                 const unsigned char *salt, size_t salt_len,
 427                 const unsigned char *ikm, size_t ikm_len,
 428                 const unsigned char *info, size_t info_len,
 429                 unsigned char *okm, size_t okm_len)
 430 {
 431     unsigned char prk[EVP_MAX_MD_SIZE];
 432     int ret, sz;
 433     size_t prk_len;
 434
 435     sz = EVP_MD_get_size(evp_md);
 436     if (sz < 0)
 437         return 0;
 438     prk_len = (size_t)sz;
 439
 440     /* Step 1: HKDF-Extract(salt, IKM) -> PRK */
 441     if (!HKDF_Extract(libctx, evp_md,
 442                       salt, salt_len, ikm, ikm_len, prk, prk_len))
 443         return 0;
 444
 445     /* Step 2: HKDF-Expand(PRK, info, L) -> OKM */
 446     ret = HKDF_Expand(evp_md, prk, prk_len, info, info_len, okm, okm_len);
 447     OPENSSL_cleanse(prk, sizeof(prk));
 448
 449     return ret;
 450 }
 451
 452 /*
 453  * Refer to "HMAC-based Extract-and-Expand Key Derivation Function (HKDF)"
 454  * Section 2.2 (https://tools.ietf.org/html/rfc5869#section-2.2).
 455  *
 456  * 2.2.  Step 1: Extract
 457  *
 458  *   HKDF-Extract(salt, IKM) -> PRK
 459  *
 460  *   Options:
 461  *      Hash     a hash function; HashLen denotes the length of the
 462  *               hash function output in octets
 463  *
 464  *   Inputs:
 465  *      salt     optional salt value (a non-secret random value);
 466  *               if not provided, it is set to a string of HashLen zeros.
 467  *      IKM      input keying material
 468  *
 469  *   Output:
 470  *      PRK      a pseudorandom key (of HashLen octets)
 471  *
 472  *   The output PRK is calculated as follows:
 473  *
 474  *   PRK = HMAC-Hash(salt, IKM)
 475  */
 476 static int HKDF_Extract(OSSL_LIB_CTX *libctx, const EVP_MD *evp_md,
 477                         const unsigned char *salt, size_t salt_len,
 478                         const unsigned char *ikm, size_t ikm_len,
 479                         unsigned char *prk, size_t prk_len)
 480 {
 481     int sz = EVP_MD_get_size(evp_md);
 482
 483     if (sz < 0)
 484         return 0;
 485     if (prk_len != (size_t)sz) {
 486         ERR_raise(ERR_LIB_PROV, PROV_R_WRONG_OUTPUT_BUFFER_SIZE);
 487         return 0;
 488     }
 489     /* calc: PRK = HMAC-Hash(salt, IKM) */
 490     return
 491         EVP_Q_mac(libctx, "HMAC", NULL, EVP_MD_get0_name(evp_md), NULL, salt,
 492                   salt_len, ikm, ikm_len, prk, EVP_MD_get_size(evp_md), NULL)
 493         != NULL;
 494 }
 495
 496 /*
 497  * Refer to "HMAC-based Extract-and-Expand Key Derivation Function (HKDF)"
 498  * Section 2.3 (https://tools.ietf.org/html/rfc5869#section-2.3).
 499  *
 500  * 2.3.  Step 2: Expand
 501  *
 502  *   HKDF-Expand(PRK, info, L) -> OKM
 503  *
 504  *   Options:
 505  *      Hash     a hash function; HashLen denotes the length of the
 506  *               hash function output in octets
 507  *
 508  *   Inputs:
 509  *      PRK      a pseudorandom key of at least HashLen octets
 510  *               (usually, the output from the extract step)
 511  *      info     optional context and application specific information
 512  *               (can be a zero-length string)
 513  *      L        length of output keying material in octets
 514  *               (<= 255*HashLen)
 515  *
 516  *   Output:
 517  *      OKM      output keying material (of L octets)
 518  *
 519  *   The output OKM is calculated as follows:
 520  *
 521  *   N = ceil(L/HashLen)
 522  *   T = T(1) | T(2) | T(3) | ... | T(N)
 523  *   OKM = first L octets of T
 524  *
 525  *   where:
 526  *   T(0) = empty string (zero length)
 527  *   T(1) = HMAC-Hash(PRK, T(0) | info | 0x01)
 528  *   T(2) = HMAC-Hash(PRK, T(1) | info | 0x02)
 529  *   T(3) = HMAC-Hash(PRK, T(2) | info | 0x03)
 530  *   ...
 531  *
 532  *   (where the constant concatenated to the end of each T(n) is a
 533  *   single octet.)
 534  */
 535 static int HKDF_Expand(const EVP_MD *evp_md,
 536                        const unsigned char *prk, size_t prk_len,
 537                        const unsigned char *info, size_t info_len,
 538                        unsigned char *okm, size_t okm_len)
 539 {
 540     HMAC_CTX *hmac;
 541     int ret = 0, sz;
 542     unsigned int i;
 543     unsigned char prev[EVP_MAX_MD_SIZE];
 544     size_t done_len = 0, dig_len, n;
 545
 546     sz = EVP_MD_get_size(evp_md);
 547     if (sz <= 0)
 548         return 0;
 549     dig_len = (size_t)sz;
 550
 551     /* calc: N = ceil(L/HashLen) */
 552     n = okm_len / dig_len;
 553     if (okm_len % dig_len)
 554         n++;
 555
 556     if (n > 255 || okm == NULL)
 557         return 0;
 558
 559     if ((hmac = HMAC_CTX_new()) == NULL)
 560         return 0;
 561
 562     if (!HMAC_Init_ex(hmac, prk, prk_len, evp_md, NULL))
 563         goto err;
 564
 565     for (i = 1; i <= n; i++) {
 566         size_t copy_len;
 567         const unsigned char ctr = i;
 568
 569         /* calc: T(i) = HMAC-Hash(PRK, T(i - 1) | info | i) */
 570         if (i > 1) {
 571             if (!HMAC_Init_ex(hmac, NULL, 0, NULL, NULL))
 572                 goto err;
 573
 574             if (!HMAC_Update(hmac, prev, dig_len))
 575                 goto err;
 576         }
 577
 578         if (!HMAC_Update(hmac, info, info_len))
 579             goto err;
 580
 581         if (!HMAC_Update(hmac, &ctr, 1))
 582             goto err;
 583
 584         if (!HMAC_Final(hmac, prev, NULL))
 585             goto err;
 586
 587         copy_len = (done_len + dig_len > okm_len) ?
 588                        okm_len - done_len :
 589                        dig_len;
 590
 591         memcpy(okm + done_len, prev, copy_len);
 592
 593         done_len += copy_len;
 594     }
 595     ret = 1;
 596
 597  err:
 598     OPENSSL_cleanse(prev, sizeof(prev));
 599     HMAC_CTX_free(hmac);
 600     return ret;
 601 }
 602
 603 /*
 604  * TLS uses slight variations of the above and for FIPS validation purposes,
 605  * they need to be present here.
 606  * Refer to RFC 8446 section 7 for specific details.
 607  */
 608
 609 /*
 610  * Given a |secret|; a |label| of length |labellen|; and |data| of length
 611  * |datalen| (e.g. typically a hash of the handshake messages), derive a new
 612  * secret |outlen| bytes long and store it in the location pointed to be |out|.
 613  * The |data| value may be zero length. Returns 1 on success and 0 on failure.
 614  */
 615 static int prov_tls13_hkdf_expand(const EVP_MD *md,
 616                                   const unsigned char *key, size_t keylen,
 617                                   const unsigned char *prefix, size_t prefixlen,
 618                                   const unsigned char *label, size_t labellen,
 619                                   const unsigned char *data, size_t datalen,
 620                                   unsigned char *out, size_t outlen)
 621 {
 622     size_t hkdflabellen;
 623     unsigned char hkdflabel[HKDF_MAXBUF];
 624     WPACKET pkt;
 625
 626     /*
 627      * 2 bytes for length of derived secret + 1 byte for length of combined
 628      * prefix and label + bytes for the label itself + 1 byte length of hash
 629      * + bytes for the hash itself.  We've got the maximum the KDF can handle
 630      * which should always be sufficient.
 631      */
 632     if (!WPACKET_init_static_len(&pkt, hkdflabel, sizeof(hkdflabel), 0)
 633             || !WPACKET_put_bytes_u16(&pkt, outlen)
 634             || !WPACKET_start_sub_packet_u8(&pkt)
 635             || !WPACKET_memcpy(&pkt, prefix, prefixlen)
 636             || !WPACKET_memcpy(&pkt, label, labellen)
 637             || !WPACKET_close(&pkt)
 638             || !WPACKET_sub_memcpy_u8(&pkt, data, (data == NULL) ? 0 : datalen)
 639             || !WPACKET_get_total_written(&pkt, &hkdflabellen)
 640             || !WPACKET_finish(&pkt)) {
 641         WPACKET_cleanup(&pkt);
 642         return 0;
 643     }
 644
 645     return HKDF_Expand(md, key, keylen, hkdflabel, hkdflabellen,
 646                        out, outlen);
 647 }
 648
 649 static int prov_tls13_hkdf_generate_secret(OSSL_LIB_CTX *libctx,
 650                                            const EVP_MD *md,
 651                                            const unsigned char *prevsecret,
 652                                            size_t prevsecretlen,
 653                                            const unsigned char *insecret,
 654                                            size_t insecretlen,
 655                                            const unsigned char *prefix,
 656                                            size_t prefixlen,
 657                                            const unsigned char *label,
 658                                            size_t labellen,
 659                                            unsigned char *out, size_t outlen)
 660 {
 661     size_t mdlen;
 662     int ret;
 663     unsigned char preextractsec[EVP_MAX_MD_SIZE];
 664     /* Always filled with zeros */
 665     static const unsigned char default_zeros[EVP_MAX_MD_SIZE];
 666
 667     ret = EVP_MD_get_size(md);
 668     /* Ensure cast to size_t is safe */
 669     if (ret <= 0)
 670         return 0;
 671     mdlen = (size_t)ret;
 672
 673     if (insecret == NULL) {
 674         insecret = default_zeros;
 675         insecretlen = mdlen;
 676     }
 677     if (prevsecret == NULL) {
 678         prevsecret = default_zeros;
 679         prevsecretlen = 0;
 680     } else {
 681         EVP_MD_CTX *mctx = EVP_MD_CTX_new();
 682         unsigned char hash[EVP_MAX_MD_SIZE];
 683
 684         /* The pre-extract derive step uses a hash of no messages */
 685         if (mctx == NULL
 686                 || EVP_DigestInit_ex(mctx, md, NULL) <= 0
 687                 || EVP_DigestFinal_ex(mctx, hash, NULL) <= 0) {
 688             EVP_MD_CTX_free(mctx);
 689             return 0;
 690         }
 691         EVP_MD_CTX_free(mctx);
 692
 693         /* Generate the pre-extract secret */
 694         if (!prov_tls13_hkdf_expand(md, prevsecret, mdlen,
 695                                     prefix, prefixlen, label, labellen,
 696                                     hash, mdlen, preextractsec, mdlen))
 697             return 0;
 698         prevsecret = preextractsec;
 699         prevsecretlen = mdlen;
 700     }
 701
 702     ret = HKDF_Extract(libctx, md, prevsecret, prevsecretlen,
 703                        insecret, insecretlen, out, outlen);
 704
 705     if (prevsecret == preextractsec)
 706         OPENSSL_cleanse(preextractsec, mdlen);
 707     return ret;
 708 }
 709
 710 static int kdf_tls1_3_derive(void *vctx, unsigned char *key, size_t keylen,
 711                              const OSSL_PARAM params[])
 712 {
 713     KDF_HKDF *ctx = (KDF_HKDF *)vctx;
 714     const EVP_MD *md;
 715
 716     if (!ossl_prov_is_running() || !kdf_tls1_3_set_ctx_params(ctx, params))
 717         return 0;
 718
 719     md = ossl_prov_digest_md(&ctx->digest);
 720     if (md == NULL) {
 721         ERR_raise(ERR_LIB_PROV, PROV_R_MISSING_MESSAGE_DIGEST);
 722         return 0;
 723     }
 724
 725     switch (ctx->mode) {
 726     default:
 727         return 0;
 728
 729     case EVP_KDF_HKDF_MODE_EXTRACT_ONLY:
 730         return prov_tls13_hkdf_generate_secret(PROV_LIBCTX_OF(ctx->provctx),
 731                                                md,
 732                                                ctx->salt, ctx->salt_len,
 733                                                ctx->key, ctx->key_len,
 734                                                ctx->prefix, ctx->prefix_len,
 735                                                ctx->label, ctx->label_len,
 736                                                key, keylen);
 737
 738     case EVP_KDF_HKDF_MODE_EXPAND_ONLY:
 739         return prov_tls13_hkdf_expand(md, ctx->key, ctx->key_len,
 740                                       ctx->prefix, ctx->prefix_len,
 741                                       ctx->label, ctx->label_len,
 742                                       ctx->data, ctx->data_len,
 743                                       key, keylen);
 744     }
 745 }
 746
 747 static int kdf_tls1_3_set_ctx_params(void *vctx, const OSSL_PARAM params[])
 748 {
 749     const OSSL_PARAM *p;
 750     KDF_HKDF *ctx = vctx;
 751
 752     if (params == NULL)
 753         return 1;
 754
 755     if (!hkdf_common_set_ctx_params(ctx, params))
 756         return 0;
 757
 758     if (ctx->mode == EVP_KDF_HKDF_MODE_EXTRACT_AND_EXPAND) {
 759         ERR_raise(ERR_LIB_PROV, PROV_R_INVALID_MODE);
 760         return 0;
 761     }
 762
 763     if ((p = OSSL_PARAM_locate_const(params, OSSL_KDF_PARAM_PREFIX)) != NULL) {
 764         OPENSSL_free(ctx->prefix);
 765         ctx->prefix = NULL;
 766         if (!OSSL_PARAM_get_octet_string(p, (void **)&ctx->prefix, 0,
 767                                          &ctx->prefix_len))
 768             return 0;
 769     }
 770
 771     if ((p = OSSL_PARAM_locate_const(params, OSSL_KDF_PARAM_LABEL)) != NULL) {
 772         OPENSSL_free(ctx->label);
 773         ctx->label = NULL;
 774         if (!OSSL_PARAM_get_octet_string(p, (void **)&ctx->label, 0,
 775                                          &ctx->label_len))
 776             return 0;
 777     }
 778
 779     OPENSSL_clear_free(ctx->data, ctx->data_len);
 780     ctx->data = NULL;
 781     if ((p = OSSL_PARAM_locate_const(params, OSSL_KDF_PARAM_DATA)) != NULL
 782             && !OSSL_PARAM_get_octet_string(p, (void **)&ctx->data, 0,
 783                                             &ctx->data_len))
 784         return 0;
 785     return 1;
 786 }
 787
 788 static const OSSL_PARAM *kdf_tls1_3_settable_ctx_params(ossl_unused void *ctx,
 789                                                         ossl_unused void *provctx)
 790 {
 791     static const OSSL_PARAM known_settable_ctx_params[] = {
 792         HKDF_COMMON_SETTABLES,
 793         OSSL_PARAM_octet_string(OSSL_KDF_PARAM_PREFIX, NULL, 0),
 794         OSSL_PARAM_octet_string(OSSL_KDF_PARAM_LABEL, NULL, 0),
 795         OSSL_PARAM_octet_string(OSSL_KDF_PARAM_DATA, NULL, 0),
 796         OSSL_PARAM_END
 797     };
 798     return known_settable_ctx_params;
 799 }
 800
 801 const OSSL_DISPATCH ossl_kdf_tls1_3_kdf_functions[] = {
 802     { OSSL_FUNC_KDF_NEWCTX, (void(*)(void))kdf_hkdf_new },
 803     { OSSL_FUNC_KDF_DUPCTX, (void(*)(void))kdf_hkdf_dup },
 804     { OSSL_FUNC_KDF_FREECTX, (void(*)(void))kdf_hkdf_free },
 805     { OSSL_FUNC_KDF_RESET, (void(*)(void))kdf_hkdf_reset },
 806     { OSSL_FUNC_KDF_DERIVE, (void(*)(void))kdf_tls1_3_derive },
 807     { OSSL_FUNC_KDF_SETTABLE_CTX_PARAMS,
 808       (void(*)(void))kdf_tls1_3_settable_ctx_params },
 809     { OSSL_FUNC_KDF_SET_CTX_PARAMS, (void(*)(void))kdf_tls1_3_set_ctx_params },
 810     { OSSL_FUNC_KDF_GETTABLE_CTX_PARAMS,
 811       (void(*)(void))kdf_hkdf_gettable_ctx_params },
 812     { OSSL_FUNC_KDF_GET_CTX_PARAMS, (void(*)(void))kdf_hkdf_get_ctx_params },
 813     OSSL_DISPATCH_END
 814 };