1 /*
2 * Copyright 2016-2024 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) != 0);
193
194 if (!ems_approved) {
195 if (!OSSL_FIPS_IND_ON_UNAPPROVED(ctx, OSSL_FIPS_IND_SETTABLE0,
196 libctx, "TLS_PRF", "EMS",
197 ossl_fips_config_tls1_prf_ems_check)) {
198 ERR_raise(ERR_LIB_PROV, PROV_R_EMS_NOT_ENABLED);
199 return 0;
200 }
201 }
202 return 1;
203 }
204
fips_digest_check_passed(TLS1_PRF * ctx,const EVP_MD * md)205 static int fips_digest_check_passed(TLS1_PRF *ctx, const EVP_MD *md)
206 {
207 OSSL_LIB_CTX *libctx = PROV_LIBCTX_OF(ctx->provctx);
208 /*
209 * Perform digest check
210 *
211 * According to NIST SP 800-135r1 section 5.2, the valid hash functions are
212 * specified in FIPS 180-3. ACVP also only lists the same set of hash
213 * functions.
214 */
215 int digest_unapproved = !EVP_MD_is_a(md, SN_sha256)
216 && !EVP_MD_is_a(md, SN_sha384)
217 && !EVP_MD_is_a(md, SN_sha512);
218
219 if (digest_unapproved) {
220 if (!OSSL_FIPS_IND_ON_UNAPPROVED(ctx, OSSL_FIPS_IND_SETTABLE1,
221 libctx, "TLS_PRF", "Digest",
222 ossl_fips_config_tls1_prf_digest_check)) {
223 ERR_raise(ERR_LIB_PROV, PROV_R_DIGEST_NOT_ALLOWED);
224 return 0;
225 }
226 }
227 return 1;
228 }
229
fips_key_check_passed(TLS1_PRF * ctx)230 static int fips_key_check_passed(TLS1_PRF *ctx)
231 {
232 OSSL_LIB_CTX *libctx = PROV_LIBCTX_OF(ctx->provctx);
233 int key_approved = ossl_kdf_check_key_size(ctx->seclen);
234
235 if (!key_approved) {
236 if (!OSSL_FIPS_IND_ON_UNAPPROVED(ctx, OSSL_FIPS_IND_SETTABLE2,
237 libctx, "TLS_PRF", "Key size",
238 ossl_fips_config_tls1_prf_key_check)) {
239 ERR_raise(ERR_LIB_PROV, PROV_R_INVALID_KEY_LENGTH);
240 return 0;
241 }
242 }
243 return 1;
244 }
245 #endif
246
kdf_tls1_prf_derive(void * vctx,unsigned char * key,size_t keylen,const OSSL_PARAM params[])247 static int kdf_tls1_prf_derive(void *vctx, unsigned char *key, size_t keylen,
248 const OSSL_PARAM params[])
249 {
250 TLS1_PRF *ctx = (TLS1_PRF *)vctx;
251
252 if (!ossl_prov_is_running() || !kdf_tls1_prf_set_ctx_params(ctx, params))
253 return 0;
254
255 if (ctx->P_hash == NULL) {
256 ERR_raise(ERR_LIB_PROV, PROV_R_MISSING_MESSAGE_DIGEST);
257 return 0;
258 }
259 if (ctx->sec == NULL) {
260 ERR_raise(ERR_LIB_PROV, PROV_R_MISSING_SECRET);
261 return 0;
262 }
263 if (ctx->seedlen == 0) {
264 ERR_raise(ERR_LIB_PROV, PROV_R_MISSING_SEED);
265 return 0;
266 }
267 if (keylen == 0) {
268 ERR_raise(ERR_LIB_PROV, PROV_R_INVALID_KEY_LENGTH);
269 return 0;
270 }
271
272 #ifdef FIPS_MODULE
273 if (!fips_ems_check_passed(ctx))
274 return 0;
275 #endif
276
277 return tls1_prf_alg(ctx->P_hash, ctx->P_sha1,
278 ctx->sec, ctx->seclen,
279 ctx->seed, ctx->seedlen,
280 key, keylen);
281 }
282
kdf_tls1_prf_set_ctx_params(void * vctx,const OSSL_PARAM params[])283 static int kdf_tls1_prf_set_ctx_params(void *vctx, const OSSL_PARAM params[])
284 {
285 const OSSL_PARAM *p;
286 TLS1_PRF *ctx = vctx;
287 OSSL_LIB_CTX *libctx = PROV_LIBCTX_OF(ctx->provctx);
288
289 if (ossl_param_is_empty(params))
290 return 1;
291
292 if (!OSSL_FIPS_IND_SET_CTX_PARAM(ctx, OSSL_FIPS_IND_SETTABLE0, params,
293 OSSL_KDF_PARAM_FIPS_EMS_CHECK))
294 return 0;
295 if (!OSSL_FIPS_IND_SET_CTX_PARAM(ctx, OSSL_FIPS_IND_SETTABLE1, params,
296 OSSL_KDF_PARAM_FIPS_DIGEST_CHECK))
297 return 0;
298 if (!OSSL_FIPS_IND_SET_CTX_PARAM(ctx, OSSL_FIPS_IND_SETTABLE2, params,
299 OSSL_KDF_PARAM_FIPS_KEY_CHECK))
300 return 0;
301
302 if ((p = OSSL_PARAM_locate_const(params, OSSL_KDF_PARAM_DIGEST)) != NULL) {
303 PROV_DIGEST digest;
304 const EVP_MD *md = NULL;
305
306 if (OPENSSL_strcasecmp(p->data, SN_md5_sha1) == 0) {
307 if (!ossl_prov_macctx_load_from_params(&ctx->P_hash, params,
308 OSSL_MAC_NAME_HMAC,
309 NULL, SN_md5, libctx)
310 || !ossl_prov_macctx_load_from_params(&ctx->P_sha1, params,
311 OSSL_MAC_NAME_HMAC,
312 NULL, SN_sha1, libctx))
313 return 0;
314 } else {
315 EVP_MAC_CTX_free(ctx->P_sha1);
316 if (!ossl_prov_macctx_load_from_params(&ctx->P_hash, params,
317 OSSL_MAC_NAME_HMAC,
318 NULL, NULL, libctx))
319 return 0;
320 }
321
322 memset(&digest, 0, sizeof(digest));
323 if (!ossl_prov_digest_load_from_params(&digest, params, libctx))
324 return 0;
325
326 md = ossl_prov_digest_md(&digest);
327 if (EVP_MD_xof(md)) {
328 ERR_raise(ERR_LIB_PROV, PROV_R_XOF_DIGESTS_NOT_ALLOWED);
329 ossl_prov_digest_reset(&digest);
330 return 0;
331 }
332
333 #ifdef FIPS_MODULE
334 if (!fips_digest_check_passed(ctx, md)) {
335 ossl_prov_digest_reset(&digest);
336 return 0;
337 }
338 #endif
339
340 ossl_prov_digest_reset(&digest);
341 }
342
343 if ((p = OSSL_PARAM_locate_const(params, OSSL_KDF_PARAM_SECRET)) != NULL) {
344 OPENSSL_clear_free(ctx->sec, ctx->seclen);
345 ctx->sec = NULL;
346 if (!OSSL_PARAM_get_octet_string(p, (void **)&ctx->sec, 0, &ctx->seclen))
347 return 0;
348
349 #ifdef FIPS_MODULE
350 if (!fips_key_check_passed(ctx))
351 return 0;
352 #endif
353 }
354 /* The seed fields concatenate, so process them all */
355 if ((p = OSSL_PARAM_locate_const(params, OSSL_KDF_PARAM_SEED)) != NULL) {
356 for (; p != NULL; p = OSSL_PARAM_locate_const(p + 1,
357 OSSL_KDF_PARAM_SEED)) {
358 if (p->data_size != 0 && p->data != NULL) {
359 const void *val = NULL;
360 size_t sz = 0;
361 unsigned char *seed;
362 size_t seedlen;
363 int err = 0;
364
365 if (!OSSL_PARAM_get_octet_string_ptr(p, &val, &sz))
366 return 0;
367
368 seedlen = safe_add_size_t(ctx->seedlen, sz, &err);
369 if (err)
370 return 0;
371
372 seed = OPENSSL_clear_realloc(ctx->seed, ctx->seedlen, seedlen);
373 if (!seed)
374 return 0;
375
376 ctx->seed = seed;
377 if (ossl_assert(sz != 0))
378 memcpy(ctx->seed + ctx->seedlen, val, sz);
379 ctx->seedlen = seedlen;
380 }
381 }
382 }
383 return 1;
384 }
385
kdf_tls1_prf_settable_ctx_params(ossl_unused void * ctx,ossl_unused void * provctx)386 static const OSSL_PARAM *kdf_tls1_prf_settable_ctx_params(
387 ossl_unused void *ctx, ossl_unused void *provctx)
388 {
389 static const OSSL_PARAM known_settable_ctx_params[] = {
390 OSSL_PARAM_utf8_string(OSSL_KDF_PARAM_PROPERTIES, NULL, 0),
391 OSSL_PARAM_utf8_string(OSSL_KDF_PARAM_DIGEST, NULL, 0),
392 OSSL_PARAM_octet_string(OSSL_KDF_PARAM_SECRET, NULL, 0),
393 OSSL_PARAM_octet_string(OSSL_KDF_PARAM_SEED, NULL, 0),
394 OSSL_FIPS_IND_SETTABLE_CTX_PARAM(OSSL_KDF_PARAM_FIPS_EMS_CHECK)
395 OSSL_FIPS_IND_SETTABLE_CTX_PARAM(OSSL_KDF_PARAM_FIPS_DIGEST_CHECK)
396 OSSL_FIPS_IND_SETTABLE_CTX_PARAM(OSSL_KDF_PARAM_FIPS_KEY_CHECK)
397 OSSL_PARAM_END
398 };
399 return known_settable_ctx_params;
400 }
401
kdf_tls1_prf_get_ctx_params(void * vctx,OSSL_PARAM params[])402 static int kdf_tls1_prf_get_ctx_params(void *vctx, OSSL_PARAM params[])
403 {
404 OSSL_PARAM *p;
405
406 if ((p = OSSL_PARAM_locate(params, OSSL_KDF_PARAM_SIZE)) != NULL) {
407 if (!OSSL_PARAM_set_size_t(p, SIZE_MAX))
408 return 0;
409 }
410 if (!OSSL_FIPS_IND_GET_CTX_PARAM(((TLS1_PRF *)vctx), params))
411 return 0;
412 return 1;
413 }
414
kdf_tls1_prf_gettable_ctx_params(ossl_unused void * ctx,ossl_unused void * provctx)415 static const OSSL_PARAM *kdf_tls1_prf_gettable_ctx_params(
416 ossl_unused void *ctx, ossl_unused void *provctx)
417 {
418 static const OSSL_PARAM known_gettable_ctx_params[] = {
419 OSSL_PARAM_size_t(OSSL_KDF_PARAM_SIZE, NULL),
420 OSSL_FIPS_IND_GETTABLE_CTX_PARAM()
421 OSSL_PARAM_END
422 };
423 return known_gettable_ctx_params;
424 }
425
426 const OSSL_DISPATCH ossl_kdf_tls1_prf_functions[] = {
427 { OSSL_FUNC_KDF_NEWCTX, (void(*)(void))kdf_tls1_prf_new },
428 { OSSL_FUNC_KDF_DUPCTX, (void(*)(void))kdf_tls1_prf_dup },
429 { OSSL_FUNC_KDF_FREECTX, (void(*)(void))kdf_tls1_prf_free },
430 { OSSL_FUNC_KDF_RESET, (void(*)(void))kdf_tls1_prf_reset },
431 { OSSL_FUNC_KDF_DERIVE, (void(*)(void))kdf_tls1_prf_derive },
432 { OSSL_FUNC_KDF_SETTABLE_CTX_PARAMS,
433 (void(*)(void))kdf_tls1_prf_settable_ctx_params },
434 { OSSL_FUNC_KDF_SET_CTX_PARAMS,
435 (void(*)(void))kdf_tls1_prf_set_ctx_params },
436 { OSSL_FUNC_KDF_GETTABLE_CTX_PARAMS,
437 (void(*)(void))kdf_tls1_prf_gettable_ctx_params },
438 { OSSL_FUNC_KDF_GET_CTX_PARAMS,
439 (void(*)(void))kdf_tls1_prf_get_ctx_params },
440 OSSL_DISPATCH_END
441 };
442
443 /*
444 * Refer to "The TLS Protocol Version 1.0" Section 5
445 * (https://tools.ietf.org/html/rfc2246#section-5) and
446 * "The Transport Layer Security (TLS) Protocol Version 1.2" Section 5
447 * (https://tools.ietf.org/html/rfc5246#section-5).
448 *
449 * P_<hash> is an expansion function that uses a single hash function to expand
450 * a secret and seed into an arbitrary quantity of output:
451 *
452 * P_<hash>(secret, seed) = HMAC_<hash>(secret, A(1) + seed) +
453 * HMAC_<hash>(secret, A(2) + seed) +
454 * HMAC_<hash>(secret, A(3) + seed) + ...
455 *
456 * where + indicates concatenation. P_<hash> can be iterated as many times as
457 * is necessary to produce the required quantity of data.
458 *
459 * A(i) is defined as:
460 * A(0) = seed
461 * A(i) = HMAC_<hash>(secret, A(i-1))
462 */
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)463 static int tls1_prf_P_hash(EVP_MAC_CTX *ctx_init,
464 const unsigned char *sec, size_t sec_len,
465 const unsigned char *seed, size_t seed_len,
466 unsigned char *out, size_t olen)
467 {
468 size_t chunk;
469 EVP_MAC_CTX *ctx = NULL, *ctx_Ai = NULL;
470 unsigned char Ai[EVP_MAX_MD_SIZE];
471 size_t Ai_len;
472 int ret = 0;
473
474 if (!EVP_MAC_init(ctx_init, sec, sec_len, NULL))
475 goto err;
476 chunk = EVP_MAC_CTX_get_mac_size(ctx_init);
477 if (chunk == 0)
478 goto err;
479 /* A(0) = seed */
480 ctx_Ai = EVP_MAC_CTX_dup(ctx_init);
481 if (ctx_Ai == NULL)
482 goto err;
483 if (seed != NULL && !EVP_MAC_update(ctx_Ai, seed, seed_len))
484 goto err;
485
486 for (;;) {
487 /* calc: A(i) = HMAC_<hash>(secret, A(i-1)) */
488 if (!EVP_MAC_final(ctx_Ai, Ai, &Ai_len, sizeof(Ai)))
489 goto err;
490 EVP_MAC_CTX_free(ctx_Ai);
491 ctx_Ai = NULL;
492
493 /* calc next chunk: HMAC_<hash>(secret, A(i) + seed) */
494 ctx = EVP_MAC_CTX_dup(ctx_init);
495 if (ctx == NULL)
496 goto err;
497 if (!EVP_MAC_update(ctx, Ai, Ai_len))
498 goto err;
499 /* save state for calculating next A(i) value */
500 if (olen > chunk) {
501 ctx_Ai = EVP_MAC_CTX_dup(ctx);
502 if (ctx_Ai == NULL)
503 goto err;
504 }
505 if (seed != NULL && !EVP_MAC_update(ctx, seed, seed_len))
506 goto err;
507 if (olen <= chunk) {
508 /* last chunk - use Ai as temp bounce buffer */
509 if (!EVP_MAC_final(ctx, Ai, &Ai_len, sizeof(Ai)))
510 goto err;
511 memcpy(out, Ai, olen);
512 break;
513 }
514 if (!EVP_MAC_final(ctx, out, NULL, olen))
515 goto err;
516 EVP_MAC_CTX_free(ctx);
517 ctx = NULL;
518 out += chunk;
519 olen -= chunk;
520 }
521 ret = 1;
522 err:
523 EVP_MAC_CTX_free(ctx);
524 EVP_MAC_CTX_free(ctx_Ai);
525 OPENSSL_cleanse(Ai, sizeof(Ai));
526 return ret;
527 }
528
529 /*
530 * Refer to "The TLS Protocol Version 1.0" Section 5
531 * (https://tools.ietf.org/html/rfc2246#section-5) and
532 * "The Transport Layer Security (TLS) Protocol Version 1.2" Section 5
533 * (https://tools.ietf.org/html/rfc5246#section-5).
534 *
535 * For TLS v1.0 and TLS v1.1:
536 *
537 * PRF(secret, label, seed) = P_MD5(S1, label + seed) XOR
538 * P_SHA-1(S2, label + seed)
539 *
540 * S1 is taken from the first half of the secret, S2 from the second half.
541 *
542 * L_S = length in bytes of secret;
543 * L_S1 = L_S2 = ceil(L_S / 2);
544 *
545 * For TLS v1.2:
546 *
547 * PRF(secret, label, seed) = P_<hash>(secret, label + seed)
548 */
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)549 static int tls1_prf_alg(EVP_MAC_CTX *mdctx, EVP_MAC_CTX *sha1ctx,
550 const unsigned char *sec, size_t slen,
551 const unsigned char *seed, size_t seed_len,
552 unsigned char *out, size_t olen)
553 {
554 if (sha1ctx != NULL) {
555 /* TLS v1.0 and TLS v1.1 */
556 size_t i;
557 unsigned char *tmp;
558 /* calc: L_S1 = L_S2 = ceil(L_S / 2) */
559 size_t L_S1 = (slen + 1) / 2;
560 size_t L_S2 = L_S1;
561
562 if (!tls1_prf_P_hash(mdctx, sec, L_S1,
563 seed, seed_len, out, olen))
564 return 0;
565
566 if ((tmp = OPENSSL_malloc(olen)) == NULL)
567 return 0;
568
569 if (!tls1_prf_P_hash(sha1ctx, sec + slen - L_S2, L_S2,
570 seed, seed_len, tmp, olen)) {
571 OPENSSL_clear_free(tmp, olen);
572 return 0;
573 }
574 for (i = 0; i < olen; i++)
575 out[i] ^= tmp[i];
576 OPENSSL_clear_free(tmp, olen);
577 return 1;
578 }
579
580 /* TLS v1.2 */
581 if (!tls1_prf_P_hash(mdctx, sec, slen, seed, seed_len, out, olen))
582 return 0;
583
584 return 1;
585 }
586
