2 * Copyright 2016-2021 The OpenSSL Project Authors. All Rights Reserved.
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
11 * HMAC low level APIs are deprecated for public use, but still ok for internal
14 #include "internal/deprecated.h"
19 #include <openssl/hmac.h>
20 #include <openssl/evp.h>
21 #include <openssl/kdf.h>
22 #include <openssl/core_names.h>
23 #include <openssl/proverr.h>
24 #include "internal/cryptlib.h"
25 #include "internal/numbers.h"
26 #include "crypto/evp.h"
27 #include "prov/provider_ctx.h"
28 #include "prov/providercommon.h"
29 #include "prov/implementations.h"
30 #include "prov/provider_util.h"
33 #define HKDF_MAXBUF 1024
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;
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);
66 unsigned char info[HKDF_MAXBUF];
70 static void *kdf_hkdf_new(void *provctx)
74 if (!ossl_prov_is_running())
77 if ((ctx = OPENSSL_zalloc(sizeof(*ctx))) == NULL)
78 ERR_raise(ERR_LIB_PROV, ERR_R_MALLOC_FAILURE);
80 ctx->provctx = provctx;
84 static void kdf_hkdf_free(void *vctx)
86 KDF_HKDF *ctx = (KDF_HKDF *)vctx;
94 static void kdf_hkdf_reset(void *vctx)
96 KDF_HKDF *ctx = (KDF_HKDF *)vctx;
97 void *provctx = ctx->provctx;
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;
107 static size_t kdf_hkdf_size(KDF_HKDF *ctx)
110 const EVP_MD *md = ossl_prov_digest_md(&ctx->digest);
112 if (ctx->mode != EVP_KDF_HKDF_MODE_EXTRACT_ONLY)
116 ERR_raise(ERR_LIB_PROV, PROV_R_MISSING_MESSAGE_DIGEST);
119 sz = EVP_MD_size(md);
126 static int kdf_hkdf_derive(void *vctx, unsigned char *key, size_t keylen,
127 const OSSL_PARAM params[])
129 KDF_HKDF *ctx = (KDF_HKDF *)vctx;
132 if (!ossl_prov_is_running() || !kdf_hkdf_set_ctx_params(ctx, params))
135 md = ossl_prov_digest_md(&ctx->digest);
137 ERR_raise(ERR_LIB_PROV, PROV_R_MISSING_MESSAGE_DIGEST);
140 if (ctx->key == NULL) {
141 ERR_raise(ERR_LIB_PROV, PROV_R_MISSING_KEY);
145 ERR_raise(ERR_LIB_PROV, PROV_R_INVALID_KEY_LENGTH);
150 case EVP_KDF_HKDF_MODE_EXTRACT_AND_EXPAND:
151 return HKDF(md, ctx->salt, ctx->salt_len, ctx->key,
152 ctx->key_len, ctx->info, ctx->info_len, key,
155 case EVP_KDF_HKDF_MODE_EXTRACT_ONLY:
156 return HKDF_Extract(md, ctx->salt, ctx->salt_len, ctx->key,
157 ctx->key_len, key, keylen);
159 case EVP_KDF_HKDF_MODE_EXPAND_ONLY:
160 return HKDF_Expand(md, ctx->key, ctx->key_len, ctx->info,
161 ctx->info_len, key, keylen);
168 static int kdf_hkdf_set_ctx_params(void *vctx, const OSSL_PARAM params[])
171 KDF_HKDF *ctx = vctx;
172 OSSL_LIB_CTX *provctx = PROV_LIBCTX_OF(ctx->provctx);
178 if (!ossl_prov_digest_load_from_params(&ctx->digest, params, provctx))
181 if ((p = OSSL_PARAM_locate_const(params, OSSL_KDF_PARAM_MODE)) != NULL) {
182 if (p->data_type == OSSL_PARAM_UTF8_STRING) {
183 if (strcasecmp(p->data, "EXTRACT_AND_EXPAND") == 0) {
184 ctx->mode = EVP_KDF_HKDF_MODE_EXTRACT_AND_EXPAND;
185 } else if (strcasecmp(p->data, "EXTRACT_ONLY") == 0) {
186 ctx->mode = EVP_KDF_HKDF_MODE_EXTRACT_ONLY;
187 } else if (strcasecmp(p->data, "EXPAND_ONLY") == 0) {
188 ctx->mode = EVP_KDF_HKDF_MODE_EXPAND_ONLY;
190 ERR_raise(ERR_LIB_PROV, PROV_R_INVALID_MODE);
193 } else if (OSSL_PARAM_get_int(p, &n)) {
194 if (n != EVP_KDF_HKDF_MODE_EXTRACT_AND_EXPAND
195 && n != EVP_KDF_HKDF_MODE_EXTRACT_ONLY
196 && n != EVP_KDF_HKDF_MODE_EXPAND_ONLY) {
197 ERR_raise(ERR_LIB_PROV, PROV_R_INVALID_MODE);
202 ERR_raise(ERR_LIB_PROV, PROV_R_INVALID_MODE);
207 if ((p = OSSL_PARAM_locate_const(params, OSSL_KDF_PARAM_KEY)) != NULL) {
208 OPENSSL_clear_free(ctx->key, ctx->key_len);
210 if (!OSSL_PARAM_get_octet_string(p, (void **)&ctx->key, 0,
215 if ((p = OSSL_PARAM_locate_const(params, OSSL_KDF_PARAM_SALT)) != NULL) {
216 if (p->data_size != 0 && p->data != NULL) {
217 OPENSSL_free(ctx->salt);
219 if (!OSSL_PARAM_get_octet_string(p, (void **)&ctx->salt, 0,
224 /* The info fields concatenate, so process them all */
225 if ((p = OSSL_PARAM_locate_const(params, OSSL_KDF_PARAM_INFO)) != NULL) {
227 for (; p != NULL; p = OSSL_PARAM_locate_const(p + 1,
228 OSSL_KDF_PARAM_INFO)) {
229 const void *q = ctx->info + ctx->info_len;
232 if (p->data_size != 0
234 && !OSSL_PARAM_get_octet_string(p, (void **)&q,
235 HKDF_MAXBUF - ctx->info_len,
244 static const OSSL_PARAM *kdf_hkdf_settable_ctx_params(ossl_unused void *ctx,
245 ossl_unused void *provctx)
247 static const OSSL_PARAM known_settable_ctx_params[] = {
248 OSSL_PARAM_utf8_string(OSSL_KDF_PARAM_MODE, NULL, 0),
249 OSSL_PARAM_int(OSSL_KDF_PARAM_MODE, NULL),
250 OSSL_PARAM_utf8_string(OSSL_KDF_PARAM_PROPERTIES, NULL, 0),
251 OSSL_PARAM_utf8_string(OSSL_KDF_PARAM_DIGEST, NULL, 0),
252 OSSL_PARAM_octet_string(OSSL_KDF_PARAM_SALT, NULL, 0),
253 OSSL_PARAM_octet_string(OSSL_KDF_PARAM_KEY, NULL, 0),
254 OSSL_PARAM_octet_string(OSSL_KDF_PARAM_INFO, NULL, 0),
257 return known_settable_ctx_params;
260 static int kdf_hkdf_get_ctx_params(void *vctx, OSSL_PARAM params[])
262 KDF_HKDF *ctx = (KDF_HKDF *)vctx;
265 if ((p = OSSL_PARAM_locate(params, OSSL_KDF_PARAM_SIZE)) != NULL)
266 return OSSL_PARAM_set_size_t(p, kdf_hkdf_size(ctx));
270 static const OSSL_PARAM *kdf_hkdf_gettable_ctx_params(ossl_unused void *ctx,
271 ossl_unused void *provctx)
273 static const OSSL_PARAM known_gettable_ctx_params[] = {
274 OSSL_PARAM_size_t(OSSL_KDF_PARAM_SIZE, NULL),
277 return known_gettable_ctx_params;
280 const OSSL_DISPATCH ossl_kdf_hkdf_functions[] = {
281 { OSSL_FUNC_KDF_NEWCTX, (void(*)(void))kdf_hkdf_new },
282 { OSSL_FUNC_KDF_FREECTX, (void(*)(void))kdf_hkdf_free },
283 { OSSL_FUNC_KDF_RESET, (void(*)(void))kdf_hkdf_reset },
284 { OSSL_FUNC_KDF_DERIVE, (void(*)(void))kdf_hkdf_derive },
285 { OSSL_FUNC_KDF_SETTABLE_CTX_PARAMS,
286 (void(*)(void))kdf_hkdf_settable_ctx_params },
287 { OSSL_FUNC_KDF_SET_CTX_PARAMS, (void(*)(void))kdf_hkdf_set_ctx_params },
288 { OSSL_FUNC_KDF_GETTABLE_CTX_PARAMS,
289 (void(*)(void))kdf_hkdf_gettable_ctx_params },
290 { OSSL_FUNC_KDF_GET_CTX_PARAMS, (void(*)(void))kdf_hkdf_get_ctx_params },
295 * Refer to "HMAC-based Extract-and-Expand Key Derivation Function (HKDF)"
296 * Section 2 (https://tools.ietf.org/html/rfc5869#section-2) and
297 * "Cryptographic Extraction and Key Derivation: The HKDF Scheme"
298 * Section 4.2 (https://eprint.iacr.org/2010/264.pdf).
301 * The scheme HKDF is specified as:
302 * HKDF(XTS, SKM, CTXinfo, L) = K(1) | K(2) | ... | K(t)
305 * SKM is source key material
306 * XTS is extractor salt (which may be null or constant)
307 * CTXinfo is context information (may be null)
308 * L is the number of key bits to be produced by KDF
309 * k is the output length in bits of the hash function used with HMAC
311 * the value K(t) is truncated to its first d = L mod k bits.
314 * 2.2. Step 1: Extract
315 * HKDF-Extract(salt, IKM) -> PRK
316 * 2.3. Step 2: Expand
317 * HKDF-Expand(PRK, info, L) -> OKM
319 static int HKDF(const EVP_MD *evp_md,
320 const unsigned char *salt, size_t salt_len,
321 const unsigned char *ikm, size_t ikm_len,
322 const unsigned char *info, size_t info_len,
323 unsigned char *okm, size_t okm_len)
325 unsigned char prk[EVP_MAX_MD_SIZE];
329 sz = EVP_MD_size(evp_md);
332 prk_len = (size_t)sz;
334 /* Step 1: HKDF-Extract(salt, IKM) -> PRK */
335 if (!HKDF_Extract(evp_md, salt, salt_len, ikm, ikm_len, prk, prk_len))
338 /* Step 2: HKDF-Expand(PRK, info, L) -> OKM */
339 ret = HKDF_Expand(evp_md, prk, prk_len, info, info_len, okm, okm_len);
340 OPENSSL_cleanse(prk, sizeof(prk));
346 * Refer to "HMAC-based Extract-and-Expand Key Derivation Function (HKDF)"
347 * Section 2.2 (https://tools.ietf.org/html/rfc5869#section-2.2).
349 * 2.2. Step 1: Extract
351 * HKDF-Extract(salt, IKM) -> PRK
354 * Hash a hash function; HashLen denotes the length of the
355 * hash function output in octets
358 * salt optional salt value (a non-secret random value);
359 * if not provided, it is set to a string of HashLen zeros.
360 * IKM input keying material
363 * PRK a pseudorandom key (of HashLen octets)
365 * The output PRK is calculated as follows:
367 * PRK = HMAC-Hash(salt, IKM)
369 static int HKDF_Extract(const EVP_MD *evp_md,
370 const unsigned char *salt, size_t salt_len,
371 const unsigned char *ikm, size_t ikm_len,
372 unsigned char *prk, size_t prk_len)
374 int sz = EVP_MD_size(evp_md);
378 if (prk_len != (size_t)sz) {
379 ERR_raise(ERR_LIB_PROV, PROV_R_WRONG_OUTPUT_BUFFER_SIZE);
382 /* calc: PRK = HMAC-Hash(salt, IKM) */
383 return HMAC(evp_md, salt, salt_len, ikm, ikm_len, prk, NULL) != NULL;
387 * Refer to "HMAC-based Extract-and-Expand Key Derivation Function (HKDF)"
388 * Section 2.3 (https://tools.ietf.org/html/rfc5869#section-2.3).
390 * 2.3. Step 2: Expand
392 * HKDF-Expand(PRK, info, L) -> OKM
395 * Hash a hash function; HashLen denotes the length of the
396 * hash function output in octets
399 * PRK a pseudorandom key of at least HashLen octets
400 * (usually, the output from the extract step)
401 * info optional context and application specific information
402 * (can be a zero-length string)
403 * L length of output keying material in octets
407 * OKM output keying material (of L octets)
409 * The output OKM is calculated as follows:
411 * N = ceil(L/HashLen)
412 * T = T(1) | T(2) | T(3) | ... | T(N)
413 * OKM = first L octets of T
416 * T(0) = empty string (zero length)
417 * T(1) = HMAC-Hash(PRK, T(0) | info | 0x01)
418 * T(2) = HMAC-Hash(PRK, T(1) | info | 0x02)
419 * T(3) = HMAC-Hash(PRK, T(2) | info | 0x03)
422 * (where the constant concatenated to the end of each T(n) is a
425 static int HKDF_Expand(const EVP_MD *evp_md,
426 const unsigned char *prk, size_t prk_len,
427 const unsigned char *info, size_t info_len,
428 unsigned char *okm, size_t okm_len)
433 unsigned char prev[EVP_MAX_MD_SIZE];
434 size_t done_len = 0, dig_len, n;
436 sz = EVP_MD_size(evp_md);
439 dig_len = (size_t)sz;
441 /* calc: N = ceil(L/HashLen) */
442 n = okm_len / dig_len;
443 if (okm_len % dig_len)
446 if (n > 255 || okm == NULL)
449 if ((hmac = HMAC_CTX_new()) == NULL)
452 if (!HMAC_Init_ex(hmac, prk, prk_len, evp_md, NULL))
455 for (i = 1; i <= n; i++) {
457 const unsigned char ctr = i;
459 /* calc: T(i) = HMAC-Hash(PRK, T(i - 1) | info | i) */
461 if (!HMAC_Init_ex(hmac, NULL, 0, NULL, NULL))
464 if (!HMAC_Update(hmac, prev, dig_len))
468 if (!HMAC_Update(hmac, info, info_len))
471 if (!HMAC_Update(hmac, &ctr, 1))
474 if (!HMAC_Final(hmac, prev, NULL))
477 copy_len = (done_len + dig_len > okm_len) ?
481 memcpy(okm + done_len, prev, copy_len);
483 done_len += copy_len;
488 OPENSSL_cleanse(prev, sizeof(prev));