1 /*
2 * Copyright 2016-2026 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 * Refer to "The TLS Protocol Version 1.0" Section 5
12 * (https://tools.ietf.org/html/rfc2246#section-5) and
13 * "The Transport Layer Security (TLS) Protocol Version 1.2" Section 5
14 * (https://tools.ietf.org/html/rfc5246#section-5).
15 *
16 * For TLS v1.0 and TLS v1.1 the TLS PRF algorithm is given by:
17 *
18 * PRF(secret, label, seed) = P_MD5(S1, label + seed) XOR
19 * P_SHA-1(S2, label + seed)
20 *
21 * where P_MD5 and P_SHA-1 are defined by P_<hash>, below, and S1 and S2 are
22 * two halves of the secret (with the possibility of one shared byte, in the
23 * case where the length of the original secret is odd). S1 is taken from the
24 * first half of the secret, S2 from the second half.
25 *
26 * For TLS v1.2 the TLS PRF algorithm is given by:
27 *
28 * PRF(secret, label, seed) = P_<hash>(secret, label + seed)
29 *
30 * where hash is SHA-256 for all cipher suites defined in RFC 5246 as well as
31 * those published prior to TLS v1.2 while the TLS v1.2 protocol is in effect,
32 * unless defined otherwise by the cipher suite.
33 *
34 * P_<hash> is an expansion function that uses a single hash function to expand
35 * a secret and seed into an arbitrary quantity of output:
36 *
37 * P_<hash>(secret, seed) = HMAC_<hash>(secret, A(1) + seed) +
38 * HMAC_<hash>(secret, A(2) + seed) +
39 * HMAC_<hash>(secret, A(3) + seed) + ...
40 *
41 * where + indicates concatenation. P_<hash> can be iterated as many times as
42 * is necessary to produce the required quantity of data.
43 *
44 * A(i) is defined as:
45 * A(0) = seed
46 * A(i) = HMAC_<hash>(secret, A(i-1))
47 */
48
49 /*
50 * Low level APIs (such as DH) are deprecated for public use, but still ok for
51 * internal use.
52 */
53 #include "internal/deprecated.h"
54
55 #include <stdio.h>
56 #include <stdarg.h>
57 #include <string.h>
58 #include <openssl/evp.h>
59 #include <openssl/kdf.h>
60 #include <openssl/core_names.h>
61 #include <openssl/params.h>
62 #include <openssl/proverr.h>
63 #include "internal/cryptlib.h"
64 #include "internal/numbers.h"
65 #include "crypto/evp.h"
66 #include "prov/provider_ctx.h"
67 #include "prov/providercommon.h"
68 #include "prov/implementations.h"
69 #include "prov/provider_util.h"
70 #include "prov/securitycheck.h"
71 #include "internal/e_os.h"
72 #include "internal/safe_math.h"
73
74 OSSL_SAFE_MATH_UNSIGNED(size_t, size_t)
75
76 static OSSL_FUNC_kdf_newctx_fn kdf_tls1_prf_new;
77 static OSSL_FUNC_kdf_dupctx_fn kdf_tls1_prf_dup;
78 static OSSL_FUNC_kdf_freectx_fn kdf_tls1_prf_free;
79 static OSSL_FUNC_kdf_reset_fn kdf_tls1_prf_reset;
80 static OSSL_FUNC_kdf_derive_fn kdf_tls1_prf_derive;
81 static OSSL_FUNC_kdf_settable_ctx_params_fn kdf_tls1_prf_settable_ctx_params;
82 static OSSL_FUNC_kdf_set_ctx_params_fn kdf_tls1_prf_set_ctx_params;
83 static OSSL_FUNC_kdf_gettable_ctx_params_fn kdf_tls1_prf_gettable_ctx_params;
84 static OSSL_FUNC_kdf_get_ctx_params_fn kdf_tls1_prf_get_ctx_params;
85
86 static int tls1_prf_alg(EVP_MAC_CTX *mdctx, EVP_MAC_CTX *sha1ctx,
87 const unsigned char *sec, size_t slen,
88 const unsigned char *seed, size_t seed_len,
89 unsigned char *out, size_t olen);
90
91 #define TLS_MD_MASTER_SECRET_CONST "\x6d\x61\x73\x74\x65\x72\x20\x73\x65\x63\x72\x65\x74"
92 #define TLS_MD_MASTER_SECRET_CONST_SIZE 13
93
94 /* TLS KDF kdf context structure */
95 typedef struct {
96 void *provctx;
97
98 /* MAC context for the main digest */
99 EVP_MAC_CTX *P_hash;
100 /* MAC context for SHA1 for the MD5/SHA-1 combined PRF */
101 EVP_MAC_CTX *P_sha1;
102
103 /* Secret value to use for PRF */
104 unsigned char *sec;
105 size_t seclen;
106 /* Concatenated seed data */
107 unsigned char *seed;
108 size_t seedlen;
109
110 OSSL_FIPS_IND_DECLARE
111 } TLS1_PRF;
112
kdf_tls1_prf_new(void * provctx)113 static void *kdf_tls1_prf_new(void *provctx)
114 {
115 TLS1_PRF *ctx;
116
117 if (!ossl_prov_is_running())
118 return NULL;
119
120 if ((ctx = OPENSSL_zalloc(sizeof(*ctx))) != NULL) {
121 ctx->provctx = provctx;
122 OSSL_FIPS_IND_INIT(ctx)
123 }
124 return ctx;
125 }
126
kdf_tls1_prf_free(void * vctx)127 static void kdf_tls1_prf_free(void *vctx)
128 {
129 TLS1_PRF *ctx = (TLS1_PRF *)vctx;
130
131 if (ctx != NULL) {
132 kdf_tls1_prf_reset(ctx);
133 OPENSSL_free(ctx);
134 }
135 }
136
kdf_tls1_prf_reset(void * vctx)137 static void kdf_tls1_prf_reset(void *vctx)
138 {
139 TLS1_PRF *ctx = (TLS1_PRF *)vctx;
140 void *provctx = ctx->provctx;
141
142 EVP_MAC_CTX_free(ctx->P_hash);
143 EVP_MAC_CTX_free(ctx->P_sha1);
144 OPENSSL_clear_free(ctx->sec, ctx->seclen);
145 OPENSSL_clear_free(ctx->seed, ctx->seedlen);
146 memset(ctx, 0, sizeof(*ctx));
147 ctx->provctx = provctx;
148 }
149
kdf_tls1_prf_dup(void * vctx)150 static void *kdf_tls1_prf_dup(void *vctx)
151 {
152 const TLS1_PRF *src = (const TLS1_PRF *)vctx;
153 TLS1_PRF *dest;
154
155 dest = kdf_tls1_prf_new(src->provctx);
156 if (dest != NULL) {
157 if (src->P_hash != NULL
158 && (dest->P_hash = EVP_MAC_CTX_dup(src->P_hash)) == NULL)
159 goto err;
160 if (src->P_sha1 != NULL
161 && (dest->P_sha1 = EVP_MAC_CTX_dup(src->P_sha1)) == NULL)
162 goto err;
163 if (!ossl_prov_memdup(src->sec, src->seclen, &dest->sec, &dest->seclen))
164 goto err;
165 if (!ossl_prov_memdup(src->seed, src->seedlen, &dest->seed,
166 &dest->seedlen))
167 goto err;
168 OSSL_FIPS_IND_COPY(dest, src)
169 }
170 return dest;
171
172 err:
173 kdf_tls1_prf_free(dest);
174 return NULL;
175 }
176
177 #ifdef FIPS_MODULE
178
fips_ems_check_passed(TLS1_PRF * ctx)179 static int fips_ems_check_passed(TLS1_PRF *ctx)
180 {
181 OSSL_LIB_CTX *libctx = PROV_LIBCTX_OF(ctx->provctx);
182 /*
183 * Check that TLS is using EMS.
184 *
185 * The seed buffer is prepended with a label.
186 * If EMS mode is enforced then the label "master secret" is not allowed,
187 * We do the check this way since the PRF is used for other purposes, as well
188 * as "extended master secret".
189 */
190 int ems_approved = (ctx->seedlen < TLS_MD_MASTER_SECRET_CONST_SIZE
191 || memcmp(ctx->seed, TLS_MD_MASTER_SECRET_CONST,
192 TLS_MD_MASTER_SECRET_CONST_SIZE)
193 != 0);
194
195 if (!ems_approved) {
196 if (!OSSL_FIPS_IND_ON_UNAPPROVED(ctx, OSSL_FIPS_IND_SETTABLE0,
197 libctx, "TLS_PRF", "EMS",
198 ossl_fips_config_tls1_prf_ems_check)) {
199 ERR_raise(ERR_LIB_PROV, PROV_R_EMS_NOT_ENABLED);
200 return 0;
201 }
202 }
203 return 1;
204 }
205
fips_digest_check_passed(TLS1_PRF * ctx,const EVP_MD * md)206 static int fips_digest_check_passed(TLS1_PRF *ctx, const EVP_MD *md)
207 {
208 OSSL_LIB_CTX *libctx = PROV_LIBCTX_OF(ctx->provctx);
209 /*
210 * Perform digest check
211 *
212 * According to NIST SP 800-135r1 section 5.2, the valid hash functions are
213 * specified in FIPS 180-3. ACVP also only lists the same set of hash
214 * functions.
215 */
216 int digest_unapproved = !EVP_MD_is_a(md, SN_sha256)
217 && !EVP_MD_is_a(md, SN_sha384)
218 && !EVP_MD_is_a(md, SN_sha512);
219
220 if (digest_unapproved) {
221 if (!OSSL_FIPS_IND_ON_UNAPPROVED(ctx, OSSL_FIPS_IND_SETTABLE1,
222 libctx, "TLS_PRF", "Digest",
223 ossl_fips_config_tls1_prf_digest_check)) {
224 ERR_raise(ERR_LIB_PROV, PROV_R_DIGEST_NOT_ALLOWED);
225 return 0;
226 }
227 }
228 return 1;
229 }
230
fips_key_check_passed(TLS1_PRF * ctx)231 static int fips_key_check_passed(TLS1_PRF *ctx)
232 {
233 OSSL_LIB_CTX *libctx = PROV_LIBCTX_OF(ctx->provctx);
234 int key_approved = ossl_kdf_check_key_size(ctx->seclen);
235
236 if (!key_approved) {
237 if (!OSSL_FIPS_IND_ON_UNAPPROVED(ctx, OSSL_FIPS_IND_SETTABLE2,
238 libctx, "TLS_PRF", "Key size",
239 ossl_fips_config_tls1_prf_key_check)) {
240 ERR_raise(ERR_LIB_PROV, PROV_R_INVALID_KEY_LENGTH);
241 return 0;
242 }
243 }
244 return 1;
245 }
246 #endif
247
kdf_tls1_prf_derive(void * vctx,unsigned char * key,size_t keylen,const OSSL_PARAM params[])248 static int kdf_tls1_prf_derive(void *vctx, unsigned char *key, size_t keylen,
249 const OSSL_PARAM params[])
250 {
251 TLS1_PRF *ctx = (TLS1_PRF *)vctx;
252
253 if (!ossl_prov_is_running() || !kdf_tls1_prf_set_ctx_params(ctx, params))
254 return 0;
255
256 if (ctx->P_hash == NULL) {
257 ERR_raise(ERR_LIB_PROV, PROV_R_MISSING_MESSAGE_DIGEST);
258 return 0;
259 }
260 if (ctx->sec == NULL) {
261 ERR_raise(ERR_LIB_PROV, PROV_R_MISSING_SECRET);
262 return 0;
263 }
264 if (ctx->seedlen == 0) {
265 ERR_raise(ERR_LIB_PROV, PROV_R_MISSING_SEED);
266 return 0;
267 }
268 if (keylen == 0) {
269 ERR_raise(ERR_LIB_PROV, PROV_R_INVALID_KEY_LENGTH);
270 return 0;
271 }
272
273 #ifdef FIPS_MODULE
274 if (!fips_ems_check_passed(ctx))
275 return 0;
276 #endif
277
278 return tls1_prf_alg(ctx->P_hash, ctx->P_sha1,
279 ctx->sec, ctx->seclen,
280 ctx->seed, ctx->seedlen,
281 key, keylen);
282 }
283
kdf_tls1_prf_set_ctx_params(void * vctx,const OSSL_PARAM params[])284 static int kdf_tls1_prf_set_ctx_params(void *vctx, const OSSL_PARAM params[])
285 {
286 const OSSL_PARAM *p;
287 TLS1_PRF *ctx = vctx;
288 OSSL_LIB_CTX *libctx = PROV_LIBCTX_OF(ctx->provctx);
289
290 if (ossl_param_is_empty(params))
291 return 1;
292
293 if (!OSSL_FIPS_IND_SET_CTX_PARAM(ctx, OSSL_FIPS_IND_SETTABLE0, params,
294 OSSL_KDF_PARAM_FIPS_EMS_CHECK))
295 return 0;
296 if (!OSSL_FIPS_IND_SET_CTX_PARAM(ctx, OSSL_FIPS_IND_SETTABLE1, params,
297 OSSL_KDF_PARAM_FIPS_DIGEST_CHECK))
298 return 0;
299 if (!OSSL_FIPS_IND_SET_CTX_PARAM(ctx, OSSL_FIPS_IND_SETTABLE2, params,
300 OSSL_KDF_PARAM_FIPS_KEY_CHECK))
301 return 0;
302
303 if ((p = OSSL_PARAM_locate_const(params, OSSL_KDF_PARAM_DIGEST)) != NULL) {
304 PROV_DIGEST digest;
305 const EVP_MD *md = NULL;
306
307 if (OPENSSL_strcasecmp(p->data, SN_md5_sha1) == 0) {
308 if (!ossl_prov_macctx_load_from_params(&ctx->P_hash, params,
309 OSSL_MAC_NAME_HMAC,
310 NULL, SN_md5, libctx)
311 || !ossl_prov_macctx_load_from_params(&ctx->P_sha1, params,
312 OSSL_MAC_NAME_HMAC,
313 NULL, SN_sha1, libctx))
314 return 0;
315 } else {
316 EVP_MAC_CTX_free(ctx->P_sha1);
317 ctx->P_sha1 = NULL;
318 if (!ossl_prov_macctx_load_from_params(&ctx->P_hash, params,
319 OSSL_MAC_NAME_HMAC,
320 NULL, NULL, libctx))
321 return 0;
322 }
323
324 memset(&digest, 0, sizeof(digest));
325 if (!ossl_prov_digest_load_from_params(&digest, params, libctx))
326 return 0;
327
328 md = ossl_prov_digest_md(&digest);
329 if (EVP_MD_xof(md)) {
330 ERR_raise(ERR_LIB_PROV, PROV_R_XOF_DIGESTS_NOT_ALLOWED);
331 ossl_prov_digest_reset(&digest);
332 return 0;
333 }
334
335 #ifdef FIPS_MODULE
336 if (!fips_digest_check_passed(ctx, md)) {
337 ossl_prov_digest_reset(&digest);
338 return 0;
339 }
340 #endif
341
342 ossl_prov_digest_reset(&digest);
343 }
344
345 if ((p = OSSL_PARAM_locate_const(params, OSSL_KDF_PARAM_SECRET)) != NULL) {
346 OPENSSL_clear_free(ctx->sec, ctx->seclen);
347 ctx->sec = NULL;
348 if (!OSSL_PARAM_get_octet_string(p, (void **)&ctx->sec, 0, &ctx->seclen))
349 return 0;
350
351 #ifdef FIPS_MODULE
352 if (!fips_key_check_passed(ctx))
353 return 0;
354 #endif
355 }
356 /* The seed fields concatenate, so process them all */
357 if ((p = OSSL_PARAM_locate_const(params, OSSL_KDF_PARAM_SEED)) != NULL) {
358 for (; p != NULL; p = OSSL_PARAM_locate_const(p + 1,
359 OSSL_KDF_PARAM_SEED)) {
360 if (p->data_size != 0 && p->data != NULL) {
361 const void *val = NULL;
362 size_t sz = 0;
363 unsigned char *seed;
364 size_t seedlen;
365 int err = 0;
366
367 if (!OSSL_PARAM_get_octet_string_ptr(p, &val, &sz))
368 return 0;
369
370 seedlen = safe_add_size_t(ctx->seedlen, sz, &err);
371 if (err)
372 return 0;
373
374 seed = OPENSSL_clear_realloc(ctx->seed, ctx->seedlen, seedlen);
375 if (!seed)
376 return 0;
377
378 ctx->seed = seed;
379 if (ossl_assert(sz != 0))
380 memcpy(ctx->seed + ctx->seedlen, val, sz);
381 ctx->seedlen = seedlen;
382 }
383 }
384 }
385 return 1;
386 }
387
kdf_tls1_prf_settable_ctx_params(ossl_unused void * ctx,ossl_unused void * provctx)388 static const OSSL_PARAM *kdf_tls1_prf_settable_ctx_params(
389 ossl_unused void *ctx, ossl_unused void *provctx)
390 {
391 static const OSSL_PARAM known_settable_ctx_params[] = {
392 OSSL_PARAM_utf8_string(OSSL_KDF_PARAM_PROPERTIES, NULL, 0),
393 OSSL_PARAM_utf8_string(OSSL_KDF_PARAM_DIGEST, NULL, 0),
394 OSSL_PARAM_octet_string(OSSL_KDF_PARAM_SECRET, NULL, 0),
395 OSSL_PARAM_octet_string(OSSL_KDF_PARAM_SEED, NULL, 0),
396 OSSL_FIPS_IND_SETTABLE_CTX_PARAM(OSSL_KDF_PARAM_FIPS_EMS_CHECK)
397 OSSL_FIPS_IND_SETTABLE_CTX_PARAM(OSSL_KDF_PARAM_FIPS_DIGEST_CHECK)
398 OSSL_FIPS_IND_SETTABLE_CTX_PARAM(OSSL_KDF_PARAM_FIPS_KEY_CHECK)
399 OSSL_PARAM_END
400 };
401 return known_settable_ctx_params;
402 }
403
kdf_tls1_prf_get_ctx_params(void * vctx,OSSL_PARAM params[])404 static int kdf_tls1_prf_get_ctx_params(void *vctx, OSSL_PARAM params[])
405 {
406 OSSL_PARAM *p;
407
408 if ((p = OSSL_PARAM_locate(params, OSSL_KDF_PARAM_SIZE)) != NULL) {
409 if (!OSSL_PARAM_set_size_t(p, SIZE_MAX))
410 return 0;
411 }
412 if (!OSSL_FIPS_IND_GET_CTX_PARAM(((TLS1_PRF *)vctx), params))
413 return 0;
414 return 1;
415 }
416
kdf_tls1_prf_gettable_ctx_params(ossl_unused void * ctx,ossl_unused void * provctx)417 static const OSSL_PARAM *kdf_tls1_prf_gettable_ctx_params(
418 ossl_unused void *ctx, ossl_unused void *provctx)
419 {
420 static const OSSL_PARAM known_gettable_ctx_params[] = {
421 OSSL_PARAM_size_t(OSSL_KDF_PARAM_SIZE, NULL),
422 OSSL_FIPS_IND_GETTABLE_CTX_PARAM()
423 OSSL_PARAM_END
424 };
425 return known_gettable_ctx_params;
426 }
427
428 const OSSL_DISPATCH ossl_kdf_tls1_prf_functions[] = {
429 { OSSL_FUNC_KDF_NEWCTX, (void (*)(void))kdf_tls1_prf_new },
430 { OSSL_FUNC_KDF_DUPCTX, (void (*)(void))kdf_tls1_prf_dup },
431 { OSSL_FUNC_KDF_FREECTX, (void (*)(void))kdf_tls1_prf_free },
432 { OSSL_FUNC_KDF_RESET, (void (*)(void))kdf_tls1_prf_reset },
433 { OSSL_FUNC_KDF_DERIVE, (void (*)(void))kdf_tls1_prf_derive },
434 { OSSL_FUNC_KDF_SETTABLE_CTX_PARAMS,
435 (void (*)(void))kdf_tls1_prf_settable_ctx_params },
436 { OSSL_FUNC_KDF_SET_CTX_PARAMS,
437 (void (*)(void))kdf_tls1_prf_set_ctx_params },
438 { OSSL_FUNC_KDF_GETTABLE_CTX_PARAMS,
439 (void (*)(void))kdf_tls1_prf_gettable_ctx_params },
440 { OSSL_FUNC_KDF_GET_CTX_PARAMS,
441 (void (*)(void))kdf_tls1_prf_get_ctx_params },
442 OSSL_DISPATCH_END
443 };
444
445 /*
446 * Refer to "The TLS Protocol Version 1.0" Section 5
447 * (https://tools.ietf.org/html/rfc2246#section-5) and
448 * "The Transport Layer Security (TLS) Protocol Version 1.2" Section 5
449 * (https://tools.ietf.org/html/rfc5246#section-5).
450 *
451 * P_<hash> is an expansion function that uses a single hash function to expand
452 * a secret and seed into an arbitrary quantity of output:
453 *
454 * P_<hash>(secret, seed) = HMAC_<hash>(secret, A(1) + seed) +
455 * HMAC_<hash>(secret, A(2) + seed) +
456 * HMAC_<hash>(secret, A(3) + seed) + ...
457 *
458 * where + indicates concatenation. P_<hash> can be iterated as many times as
459 * is necessary to produce the required quantity of data.
460 *
461 * A(i) is defined as:
462 * A(0) = seed
463 * A(i) = HMAC_<hash>(secret, A(i-1))
464 */
tls1_prf_P_hash(EVP_MAC_CTX * ctx_init,const unsigned char * sec,size_t sec_len,const unsigned char * seed,size_t seed_len,unsigned char * out,size_t olen)465 static int tls1_prf_P_hash(EVP_MAC_CTX *ctx_init,
466 const unsigned char *sec, size_t sec_len,
467 const unsigned char *seed, size_t seed_len,
468 unsigned char *out, size_t olen)
469 {
470 size_t chunk;
471 EVP_MAC_CTX *ctx = NULL, *ctx_Ai = NULL;
472 unsigned char Ai[EVP_MAX_MD_SIZE];
473 size_t Ai_len;
474 int ret = 0;
475
476 if (!EVP_MAC_init(ctx_init, sec, sec_len, NULL))
477 goto err;
478 chunk = EVP_MAC_CTX_get_mac_size(ctx_init);
479 if (chunk == 0)
480 goto err;
481 /* A(0) = seed */
482 ctx_Ai = EVP_MAC_CTX_dup(ctx_init);
483 if (ctx_Ai == NULL)
484 goto err;
485 if (seed != NULL && !EVP_MAC_update(ctx_Ai, seed, seed_len))
486 goto err;
487
488 for (;;) {
489 /* calc: A(i) = HMAC_<hash>(secret, A(i-1)) */
490 if (!EVP_MAC_final(ctx_Ai, Ai, &Ai_len, sizeof(Ai)))
491 goto err;
492 EVP_MAC_CTX_free(ctx_Ai);
493 ctx_Ai = NULL;
494
495 /* calc next chunk: HMAC_<hash>(secret, A(i) + seed) */
496 ctx = EVP_MAC_CTX_dup(ctx_init);
497 if (ctx == NULL)
498 goto err;
499 if (!EVP_MAC_update(ctx, Ai, Ai_len))
500 goto err;
501 /* save state for calculating next A(i) value */
502 if (olen > chunk) {
503 ctx_Ai = EVP_MAC_CTX_dup(ctx);
504 if (ctx_Ai == NULL)
505 goto err;
506 }
507 if (seed != NULL && !EVP_MAC_update(ctx, seed, seed_len))
508 goto err;
509 if (olen <= chunk) {
510 /* last chunk - use Ai as temp bounce buffer */
511 if (!EVP_MAC_final(ctx, Ai, &Ai_len, sizeof(Ai)))
512 goto err;
513 memcpy(out, Ai, olen);
514 break;
515 }
516 if (!EVP_MAC_final(ctx, out, NULL, olen))
517 goto err;
518 EVP_MAC_CTX_free(ctx);
519 ctx = NULL;
520 out += chunk;
521 olen -= chunk;
522 }
523 ret = 1;
524 err:
525 EVP_MAC_CTX_free(ctx);
526 EVP_MAC_CTX_free(ctx_Ai);
527 OPENSSL_cleanse(Ai, sizeof(Ai));
528 return ret;
529 }
530
531 /*
532 * Refer to "The TLS Protocol Version 1.0" Section 5
533 * (https://tools.ietf.org/html/rfc2246#section-5) and
534 * "The Transport Layer Security (TLS) Protocol Version 1.2" Section 5
535 * (https://tools.ietf.org/html/rfc5246#section-5).
536 *
537 * For TLS v1.0 and TLS v1.1:
538 *
539 * PRF(secret, label, seed) = P_MD5(S1, label + seed) XOR
540 * P_SHA-1(S2, label + seed)
541 *
542 * S1 is taken from the first half of the secret, S2 from the second half.
543 *
544 * L_S = length in bytes of secret;
545 * L_S1 = L_S2 = ceil(L_S / 2);
546 *
547 * For TLS v1.2:
548 *
549 * PRF(secret, label, seed) = P_<hash>(secret, label + seed)
550 */
tls1_prf_alg(EVP_MAC_CTX * mdctx,EVP_MAC_CTX * sha1ctx,const unsigned char * sec,size_t slen,const unsigned char * seed,size_t seed_len,unsigned char * out,size_t olen)551 static int tls1_prf_alg(EVP_MAC_CTX *mdctx, EVP_MAC_CTX *sha1ctx,
552 const unsigned char *sec, size_t slen,
553 const unsigned char *seed, size_t seed_len,
554 unsigned char *out, size_t olen)
555 {
556 if (sha1ctx != NULL) {
557 /* TLS v1.0 and TLS v1.1 */
558 size_t i;
559 unsigned char *tmp;
560 /* calc: L_S1 = L_S2 = ceil(L_S / 2) */
561 size_t L_S1 = (slen + 1) / 2;
562 size_t L_S2 = L_S1;
563
564 if (!tls1_prf_P_hash(mdctx, sec, L_S1,
565 seed, seed_len, out, olen))
566 return 0;
567
568 if ((tmp = OPENSSL_malloc(olen)) == NULL)
569 return 0;
570
571 if (!tls1_prf_P_hash(sha1ctx, sec + slen - L_S2, L_S2,
572 seed, seed_len, tmp, olen)) {
573 OPENSSL_clear_free(tmp, olen);
574 return 0;
575 }
576 for (i = 0; i < olen; i++)
577 out[i] ^= tmp[i];
578 OPENSSL_clear_free(tmp, olen);
579 return 1;
580 }
581
582 /* TLS v1.2 */
583 if (!tls1_prf_P_hash(mdctx, sec, slen, seed, seed_len, out, olen))
584 return 0;
585
586 return 1;
587 }
588