1 /* Copyright (c) 2016, Google Inc.
2 *
3 * Permission to use, copy, modify, and/or distribute this software for any
4 * purpose with or without fee is hereby granted, provided that the above
5 * copyright notice and this permission notice appear in all copies.
6 *
7 * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
8 * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
9 * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY
10 * SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
11 * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN ACTION
12 * OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF OR IN
13 * CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE. */
14
15 #include <openssl/ssl.h>
16
17 #include <assert.h>
18 #include <string.h>
19
20 #include <utility>
21
22 #include <openssl/aead.h>
23 #include <openssl/bytestring.h>
24 #include <openssl/digest.h>
25 #include <openssl/hkdf.h>
26 #include <openssl/hmac.h>
27 #include <openssl/mem.h>
28
29 #include "../crypto/internal.h"
30 #include "internal.h"
31
32
33 BSSL_NAMESPACE_BEGIN
34
init_key_schedule(SSL_HANDSHAKE * hs,uint16_t version,const SSL_CIPHER * cipher)35 static bool init_key_schedule(SSL_HANDSHAKE *hs, uint16_t version,
36 const SSL_CIPHER *cipher) {
37 if (!hs->transcript.InitHash(version, cipher)) {
38 return false;
39 }
40
41 hs->hash_len = hs->transcript.DigestLen();
42
43 // Initialize the secret to the zero key.
44 OPENSSL_memset(hs->secret, 0, hs->hash_len);
45
46 return true;
47 }
48
tls13_init_key_schedule(SSL_HANDSHAKE * hs,const uint8_t * psk,size_t psk_len)49 bool tls13_init_key_schedule(SSL_HANDSHAKE *hs, const uint8_t *psk,
50 size_t psk_len) {
51 if (!init_key_schedule(hs, ssl_protocol_version(hs->ssl), hs->new_cipher)) {
52 return false;
53 }
54
55 hs->transcript.FreeBuffer();
56 return HKDF_extract(hs->secret, &hs->hash_len, hs->transcript.Digest(), psk,
57 psk_len, hs->secret, hs->hash_len);
58 }
59
tls13_init_early_key_schedule(SSL_HANDSHAKE * hs,const uint8_t * psk,size_t psk_len)60 bool tls13_init_early_key_schedule(SSL_HANDSHAKE *hs, const uint8_t *psk,
61 size_t psk_len) {
62 SSL *const ssl = hs->ssl;
63 return init_key_schedule(hs, ssl_session_protocol_version(ssl->session.get()),
64 ssl->session->cipher) &&
65 HKDF_extract(hs->secret, &hs->hash_len, hs->transcript.Digest(), psk,
66 psk_len, hs->secret, hs->hash_len);
67 }
68
hkdf_expand_label(uint8_t * out,const EVP_MD * digest,const uint8_t * secret,size_t secret_len,const char * label,size_t label_len,const uint8_t * hash,size_t hash_len,size_t len)69 static bool hkdf_expand_label(uint8_t *out, const EVP_MD *digest,
70 const uint8_t *secret, size_t secret_len,
71 const char *label, size_t label_len,
72 const uint8_t *hash, size_t hash_len,
73 size_t len) {
74 static const char kTLS13ProtocolLabel[] = "tls13 ";
75
76 ScopedCBB cbb;
77 CBB child;
78 Array<uint8_t> hkdf_label;
79 if (!CBB_init(cbb.get(), 2 + 1 + strlen(kTLS13ProtocolLabel) + label_len + 1 +
80 hash_len) ||
81 !CBB_add_u16(cbb.get(), len) ||
82 !CBB_add_u8_length_prefixed(cbb.get(), &child) ||
83 !CBB_add_bytes(&child, (const uint8_t *)kTLS13ProtocolLabel,
84 strlen(kTLS13ProtocolLabel)) ||
85 !CBB_add_bytes(&child, (const uint8_t *)label, label_len) ||
86 !CBB_add_u8_length_prefixed(cbb.get(), &child) ||
87 !CBB_add_bytes(&child, hash, hash_len) ||
88 !CBBFinishArray(cbb.get(), &hkdf_label)) {
89 return false;
90 }
91
92 return HKDF_expand(out, len, digest, secret, secret_len, hkdf_label.data(),
93 hkdf_label.size());
94 }
95
96 static const char kTLS13LabelDerived[] = "derived";
97
tls13_advance_key_schedule(SSL_HANDSHAKE * hs,const uint8_t * in,size_t len)98 bool tls13_advance_key_schedule(SSL_HANDSHAKE *hs, const uint8_t *in,
99 size_t len) {
100 uint8_t derive_context[EVP_MAX_MD_SIZE];
101 unsigned derive_context_len;
102 if (!EVP_Digest(nullptr, 0, derive_context, &derive_context_len,
103 hs->transcript.Digest(), nullptr)) {
104 return false;
105 }
106
107 if (!hkdf_expand_label(hs->secret, hs->transcript.Digest(), hs->secret,
108 hs->hash_len, kTLS13LabelDerived,
109 strlen(kTLS13LabelDerived), derive_context,
110 derive_context_len, hs->hash_len)) {
111 return false;
112 }
113
114 return HKDF_extract(hs->secret, &hs->hash_len, hs->transcript.Digest(), in,
115 len, hs->secret, hs->hash_len);
116 }
117
118 // derive_secret derives a secret of length |len| and writes the result in |out|
119 // with the given label and the current base secret and most recently-saved
120 // handshake context. It returns true on success and false on error.
derive_secret(SSL_HANDSHAKE * hs,uint8_t * out,size_t len,const char * label,size_t label_len)121 static bool derive_secret(SSL_HANDSHAKE *hs, uint8_t *out, size_t len,
122 const char *label, size_t label_len) {
123 uint8_t context_hash[EVP_MAX_MD_SIZE];
124 size_t context_hash_len;
125 if (!hs->transcript.GetHash(context_hash, &context_hash_len)) {
126 return false;
127 }
128
129 return hkdf_expand_label(out, hs->transcript.Digest(), hs->secret,
130 hs->hash_len, label, label_len, context_hash,
131 context_hash_len, len);
132 }
133
tls13_set_traffic_key(SSL * ssl,enum ssl_encryption_level_t level,enum evp_aead_direction_t direction,const uint8_t * traffic_secret,size_t traffic_secret_len)134 bool tls13_set_traffic_key(SSL *ssl, enum ssl_encryption_level_t level,
135 enum evp_aead_direction_t direction,
136 const uint8_t *traffic_secret,
137 size_t traffic_secret_len) {
138 const SSL_SESSION *session = SSL_get_session(ssl);
139 uint16_t version = ssl_session_protocol_version(session);
140
141 if (traffic_secret_len > 0xff) {
142 OPENSSL_PUT_ERROR(SSL, ERR_R_OVERFLOW);
143 return false;
144 }
145
146 UniquePtr<SSLAEADContext> traffic_aead;
147 if (ssl->quic_method == nullptr) {
148 // Look up cipher suite properties.
149 const EVP_AEAD *aead;
150 size_t discard;
151 if (!ssl_cipher_get_evp_aead(&aead, &discard, &discard, session->cipher,
152 version, SSL_is_dtls(ssl))) {
153 return false;
154 }
155
156 const EVP_MD *digest = ssl_session_get_digest(session);
157
158 // Derive the key.
159 size_t key_len = EVP_AEAD_key_length(aead);
160 uint8_t key[EVP_AEAD_MAX_KEY_LENGTH];
161 if (!hkdf_expand_label(key, digest, traffic_secret, traffic_secret_len,
162 "key", 3, NULL, 0, key_len)) {
163 return false;
164 }
165
166 // Derive the IV.
167 size_t iv_len = EVP_AEAD_nonce_length(aead);
168 uint8_t iv[EVP_AEAD_MAX_NONCE_LENGTH];
169 if (!hkdf_expand_label(iv, digest, traffic_secret, traffic_secret_len, "iv",
170 2, NULL, 0, iv_len)) {
171 return false;
172 }
173
174
175 traffic_aead = SSLAEADContext::Create(
176 direction, session->ssl_version, SSL_is_dtls(ssl), session->cipher,
177 MakeConstSpan(key, key_len), Span<const uint8_t>(),
178 MakeConstSpan(iv, iv_len));
179 } else {
180 // Install a placeholder SSLAEADContext so that SSL accessors work. The
181 // encryption itself will be handled by the SSL_QUIC_METHOD.
182 traffic_aead =
183 SSLAEADContext::CreatePlaceholderForQUIC(version, session->cipher);
184 }
185
186 if (!traffic_aead) {
187 return false;
188 }
189
190 if (direction == evp_aead_open) {
191 if (!ssl->method->set_read_state(ssl, std::move(traffic_aead))) {
192 return false;
193 }
194 } else {
195 if (!ssl->method->set_write_state(ssl, std::move(traffic_aead))) {
196 return false;
197 }
198 }
199
200 // Save the traffic secret.
201 if (direction == evp_aead_open) {
202 OPENSSL_memmove(ssl->s3->read_traffic_secret, traffic_secret,
203 traffic_secret_len);
204 ssl->s3->read_traffic_secret_len = traffic_secret_len;
205 ssl->s3->read_level = level;
206 } else {
207 OPENSSL_memmove(ssl->s3->write_traffic_secret, traffic_secret,
208 traffic_secret_len);
209 ssl->s3->write_traffic_secret_len = traffic_secret_len;
210 ssl->s3->write_level = level;
211 }
212
213 return true;
214 }
215
216
217 static const char kTLS13LabelExporter[] = "exp master";
218 static const char kTLS13LabelEarlyExporter[] = "e exp master";
219
220 static const char kTLS13LabelClientEarlyTraffic[] = "c e traffic";
221 static const char kTLS13LabelClientHandshakeTraffic[] = "c hs traffic";
222 static const char kTLS13LabelServerHandshakeTraffic[] = "s hs traffic";
223 static const char kTLS13LabelClientApplicationTraffic[] = "c ap traffic";
224 static const char kTLS13LabelServerApplicationTraffic[] = "s ap traffic";
225
tls13_derive_early_secrets(SSL_HANDSHAKE * hs)226 bool tls13_derive_early_secrets(SSL_HANDSHAKE *hs) {
227 SSL *const ssl = hs->ssl;
228 if (!derive_secret(hs, hs->early_traffic_secret, hs->hash_len,
229 kTLS13LabelClientEarlyTraffic,
230 strlen(kTLS13LabelClientEarlyTraffic)) ||
231 !ssl_log_secret(ssl, "CLIENT_EARLY_TRAFFIC_SECRET",
232 hs->early_traffic_secret, hs->hash_len) ||
233 !derive_secret(hs, ssl->s3->early_exporter_secret, hs->hash_len,
234 kTLS13LabelEarlyExporter,
235 strlen(kTLS13LabelEarlyExporter))) {
236 return false;
237 }
238 ssl->s3->early_exporter_secret_len = hs->hash_len;
239
240 if (ssl->quic_method != nullptr) {
241 if (ssl->server) {
242 if (!ssl->quic_method->set_encryption_secrets(
243 ssl, ssl_encryption_early_data, nullptr, hs->early_traffic_secret,
244 hs->hash_len)) {
245 OPENSSL_PUT_ERROR(SSL, SSL_R_QUIC_INTERNAL_ERROR);
246 return false;
247 }
248 } else {
249 if (!ssl->quic_method->set_encryption_secrets(
250 ssl, ssl_encryption_early_data, hs->early_traffic_secret, nullptr,
251 hs->hash_len)) {
252 OPENSSL_PUT_ERROR(SSL, SSL_R_QUIC_INTERNAL_ERROR);
253 return false;
254 }
255 }
256 }
257
258 return true;
259 }
260
tls13_derive_handshake_secrets(SSL_HANDSHAKE * hs)261 bool tls13_derive_handshake_secrets(SSL_HANDSHAKE *hs) {
262 SSL *const ssl = hs->ssl;
263 if (!derive_secret(hs, hs->client_handshake_secret, hs->hash_len,
264 kTLS13LabelClientHandshakeTraffic,
265 strlen(kTLS13LabelClientHandshakeTraffic)) ||
266 !ssl_log_secret(ssl, "CLIENT_HANDSHAKE_TRAFFIC_SECRET",
267 hs->client_handshake_secret, hs->hash_len) ||
268 !derive_secret(hs, hs->server_handshake_secret, hs->hash_len,
269 kTLS13LabelServerHandshakeTraffic,
270 strlen(kTLS13LabelServerHandshakeTraffic)) ||
271 !ssl_log_secret(ssl, "SERVER_HANDSHAKE_TRAFFIC_SECRET",
272 hs->server_handshake_secret, hs->hash_len)) {
273 return false;
274 }
275
276 if (ssl->quic_method != nullptr) {
277 if (ssl->server) {
278 if (!ssl->quic_method->set_encryption_secrets(
279 ssl, ssl_encryption_handshake, hs->client_handshake_secret,
280 hs->server_handshake_secret, hs->hash_len)) {
281 OPENSSL_PUT_ERROR(SSL, SSL_R_QUIC_INTERNAL_ERROR);
282 return false;
283 }
284 } else {
285 if (!ssl->quic_method->set_encryption_secrets(
286 ssl, ssl_encryption_handshake, hs->server_handshake_secret,
287 hs->client_handshake_secret, hs->hash_len)) {
288 OPENSSL_PUT_ERROR(SSL, SSL_R_QUIC_INTERNAL_ERROR);
289 return false;
290 }
291 }
292 }
293
294 return true;
295 }
296
tls13_derive_application_secrets(SSL_HANDSHAKE * hs)297 bool tls13_derive_application_secrets(SSL_HANDSHAKE *hs) {
298 SSL *const ssl = hs->ssl;
299 ssl->s3->exporter_secret_len = hs->hash_len;
300 if (!derive_secret(hs, hs->client_traffic_secret_0, hs->hash_len,
301 kTLS13LabelClientApplicationTraffic,
302 strlen(kTLS13LabelClientApplicationTraffic)) ||
303 !ssl_log_secret(ssl, "CLIENT_TRAFFIC_SECRET_0",
304 hs->client_traffic_secret_0, hs->hash_len) ||
305 !derive_secret(hs, hs->server_traffic_secret_0, hs->hash_len,
306 kTLS13LabelServerApplicationTraffic,
307 strlen(kTLS13LabelServerApplicationTraffic)) ||
308 !ssl_log_secret(ssl, "SERVER_TRAFFIC_SECRET_0",
309 hs->server_traffic_secret_0, hs->hash_len) ||
310 !derive_secret(hs, ssl->s3->exporter_secret, hs->hash_len,
311 kTLS13LabelExporter, strlen(kTLS13LabelExporter)) ||
312 !ssl_log_secret(ssl, "EXPORTER_SECRET", ssl->s3->exporter_secret,
313 hs->hash_len)) {
314 return false;
315 }
316
317 if (ssl->quic_method != nullptr) {
318 if (ssl->server) {
319 if (!ssl->quic_method->set_encryption_secrets(
320 ssl, ssl_encryption_application, hs->client_traffic_secret_0,
321 hs->server_traffic_secret_0, hs->hash_len)) {
322 OPENSSL_PUT_ERROR(SSL, SSL_R_QUIC_INTERNAL_ERROR);
323 return false;
324 }
325 } else {
326 if (!ssl->quic_method->set_encryption_secrets(
327 ssl, ssl_encryption_application, hs->server_traffic_secret_0,
328 hs->client_traffic_secret_0, hs->hash_len)) {
329 OPENSSL_PUT_ERROR(SSL, SSL_R_QUIC_INTERNAL_ERROR);
330 return false;
331 }
332 }
333 }
334
335 return true;
336 }
337
338 static const char kTLS13LabelApplicationTraffic[] = "traffic upd";
339
tls13_rotate_traffic_key(SSL * ssl,enum evp_aead_direction_t direction)340 bool tls13_rotate_traffic_key(SSL *ssl, enum evp_aead_direction_t direction) {
341 uint8_t *secret;
342 size_t secret_len;
343 if (direction == evp_aead_open) {
344 secret = ssl->s3->read_traffic_secret;
345 secret_len = ssl->s3->read_traffic_secret_len;
346 } else {
347 secret = ssl->s3->write_traffic_secret;
348 secret_len = ssl->s3->write_traffic_secret_len;
349 }
350
351 const EVP_MD *digest = ssl_session_get_digest(SSL_get_session(ssl));
352 if (!hkdf_expand_label(secret, digest, secret, secret_len,
353 kTLS13LabelApplicationTraffic,
354 strlen(kTLS13LabelApplicationTraffic), NULL, 0,
355 secret_len)) {
356 return false;
357 }
358
359 return tls13_set_traffic_key(ssl, ssl_encryption_application, direction,
360 secret, secret_len);
361 }
362
363 static const char kTLS13LabelResumption[] = "res master";
364
tls13_derive_resumption_secret(SSL_HANDSHAKE * hs)365 bool tls13_derive_resumption_secret(SSL_HANDSHAKE *hs) {
366 if (hs->hash_len > SSL_MAX_MASTER_KEY_LENGTH) {
367 OPENSSL_PUT_ERROR(SSL, ERR_R_INTERNAL_ERROR);
368 return false;
369 }
370 hs->new_session->master_key_length = hs->hash_len;
371 return derive_secret(hs, hs->new_session->master_key,
372 hs->new_session->master_key_length,
373 kTLS13LabelResumption, strlen(kTLS13LabelResumption));
374 }
375
376 static const char kTLS13LabelFinished[] = "finished";
377
378 // tls13_verify_data sets |out| to be the HMAC of |context| using a derived
379 // Finished key for both Finished messages and the PSK binder.
tls13_verify_data(const EVP_MD * digest,uint16_t version,uint8_t * out,size_t * out_len,const uint8_t * secret,size_t hash_len,uint8_t * context,size_t context_len)380 static bool tls13_verify_data(const EVP_MD *digest, uint16_t version,
381 uint8_t *out, size_t *out_len,
382 const uint8_t *secret, size_t hash_len,
383 uint8_t *context, size_t context_len) {
384 uint8_t key[EVP_MAX_MD_SIZE];
385 unsigned len;
386 if (!hkdf_expand_label(key, digest, secret, hash_len, kTLS13LabelFinished,
387 strlen(kTLS13LabelFinished), NULL, 0, hash_len) ||
388 HMAC(digest, key, hash_len, context, context_len, out, &len) == NULL) {
389 return false;
390 }
391 *out_len = len;
392 return true;
393 }
394
tls13_finished_mac(SSL_HANDSHAKE * hs,uint8_t * out,size_t * out_len,bool is_server)395 bool tls13_finished_mac(SSL_HANDSHAKE *hs, uint8_t *out, size_t *out_len,
396 bool is_server) {
397 const uint8_t *traffic_secret;
398 if (is_server) {
399 traffic_secret = hs->server_handshake_secret;
400 } else {
401 traffic_secret = hs->client_handshake_secret;
402 }
403
404 uint8_t context_hash[EVP_MAX_MD_SIZE];
405 size_t context_hash_len;
406 if (!hs->transcript.GetHash(context_hash, &context_hash_len) ||
407 !tls13_verify_data(hs->transcript.Digest(), hs->ssl->version, out,
408 out_len, traffic_secret, hs->hash_len, context_hash,
409 context_hash_len)) {
410 return 0;
411 }
412 return 1;
413 }
414
415 static const char kTLS13LabelResumptionPSK[] = "resumption";
416
tls13_derive_session_psk(SSL_SESSION * session,Span<const uint8_t> nonce)417 bool tls13_derive_session_psk(SSL_SESSION *session, Span<const uint8_t> nonce) {
418 const EVP_MD *digest = ssl_session_get_digest(session);
419 return hkdf_expand_label(session->master_key, digest, session->master_key,
420 session->master_key_length, kTLS13LabelResumptionPSK,
421 strlen(kTLS13LabelResumptionPSK), nonce.data(),
422 nonce.size(), session->master_key_length);
423 }
424
425 static const char kTLS13LabelExportKeying[] = "exporter";
426
tls13_export_keying_material(SSL * ssl,Span<uint8_t> out,Span<const uint8_t> secret,Span<const char> label,Span<const uint8_t> context)427 bool tls13_export_keying_material(SSL *ssl, Span<uint8_t> out,
428 Span<const uint8_t> secret,
429 Span<const char> label,
430 Span<const uint8_t> context) {
431 if (secret.empty()) {
432 assert(0);
433 OPENSSL_PUT_ERROR(SSL, ERR_R_INTERNAL_ERROR);
434 return false;
435 }
436
437 const EVP_MD *digest = ssl_session_get_digest(SSL_get_session(ssl));
438
439 uint8_t hash[EVP_MAX_MD_SIZE];
440 uint8_t export_context[EVP_MAX_MD_SIZE];
441 uint8_t derived_secret[EVP_MAX_MD_SIZE];
442 unsigned hash_len;
443 unsigned export_context_len;
444 unsigned derived_secret_len = EVP_MD_size(digest);
445 return EVP_Digest(context.data(), context.size(), hash, &hash_len, digest,
446 nullptr) &&
447 EVP_Digest(nullptr, 0, export_context, &export_context_len, digest,
448 nullptr) &&
449 hkdf_expand_label(derived_secret, digest, secret.data(), secret.size(),
450 label.data(), label.size(), export_context,
451 export_context_len, derived_secret_len) &&
452 hkdf_expand_label(out.data(), digest, derived_secret,
453 derived_secret_len, kTLS13LabelExportKeying,
454 strlen(kTLS13LabelExportKeying), hash, hash_len,
455 out.size());
456 }
457
458 static const char kTLS13LabelPSKBinder[] = "res binder";
459
tls13_psk_binder(uint8_t * out,uint16_t version,const EVP_MD * digest,uint8_t * psk,size_t psk_len,uint8_t * context,size_t context_len,size_t hash_len)460 static bool tls13_psk_binder(uint8_t *out, uint16_t version,
461 const EVP_MD *digest, uint8_t *psk, size_t psk_len,
462 uint8_t *context, size_t context_len,
463 size_t hash_len) {
464 uint8_t binder_context[EVP_MAX_MD_SIZE];
465 unsigned binder_context_len;
466 if (!EVP_Digest(NULL, 0, binder_context, &binder_context_len, digest, NULL)) {
467 return false;
468 }
469
470 uint8_t early_secret[EVP_MAX_MD_SIZE] = {0};
471 size_t early_secret_len;
472 if (!HKDF_extract(early_secret, &early_secret_len, digest, psk, hash_len,
473 NULL, 0)) {
474 return false;
475 }
476
477 uint8_t binder_key[EVP_MAX_MD_SIZE] = {0};
478 size_t len;
479 if (!hkdf_expand_label(binder_key, digest, early_secret, hash_len,
480 kTLS13LabelPSKBinder, strlen(kTLS13LabelPSKBinder),
481 binder_context, binder_context_len, hash_len) ||
482 !tls13_verify_data(digest, version, out, &len, binder_key, hash_len,
483 context, context_len)) {
484 return false;
485 }
486
487 return true;
488 }
489
tls13_write_psk_binder(SSL_HANDSHAKE * hs,uint8_t * msg,size_t len)490 bool tls13_write_psk_binder(SSL_HANDSHAKE *hs, uint8_t *msg, size_t len) {
491 SSL *const ssl = hs->ssl;
492 const EVP_MD *digest = ssl_session_get_digest(ssl->session.get());
493 size_t hash_len = EVP_MD_size(digest);
494
495 if (len < hash_len + 3) {
496 OPENSSL_PUT_ERROR(SSL, ERR_R_INTERNAL_ERROR);
497 return false;
498 }
499
500 ScopedEVP_MD_CTX ctx;
501 uint8_t context[EVP_MAX_MD_SIZE];
502 unsigned context_len;
503
504 if (!EVP_DigestInit_ex(ctx.get(), digest, NULL) ||
505 !EVP_DigestUpdate(ctx.get(), hs->transcript.buffer().data(),
506 hs->transcript.buffer().size()) ||
507 !EVP_DigestUpdate(ctx.get(), msg, len - hash_len - 3) ||
508 !EVP_DigestFinal_ex(ctx.get(), context, &context_len)) {
509 return false;
510 }
511
512 uint8_t verify_data[EVP_MAX_MD_SIZE] = {0};
513 if (!tls13_psk_binder(verify_data, ssl->session->ssl_version, digest,
514 ssl->session->master_key,
515 ssl->session->master_key_length, context, context_len,
516 hash_len)) {
517 return false;
518 }
519
520 OPENSSL_memcpy(msg + len - hash_len, verify_data, hash_len);
521 return true;
522 }
523
tls13_verify_psk_binder(SSL_HANDSHAKE * hs,SSL_SESSION * session,const SSLMessage & msg,CBS * binders)524 bool tls13_verify_psk_binder(SSL_HANDSHAKE *hs, SSL_SESSION *session,
525 const SSLMessage &msg, CBS *binders) {
526 size_t hash_len = hs->transcript.DigestLen();
527
528 // The message must be large enough to exclude the binders.
529 if (CBS_len(&msg.raw) < CBS_len(binders) + 2) {
530 OPENSSL_PUT_ERROR(SSL, ERR_R_INTERNAL_ERROR);
531 return false;
532 }
533
534 // Hash a ClientHello prefix up to the binders. This includes the header. For
535 // now, this assumes we only ever verify PSK binders on initial
536 // ClientHellos.
537 uint8_t context[EVP_MAX_MD_SIZE];
538 unsigned context_len;
539 if (!EVP_Digest(CBS_data(&msg.raw), CBS_len(&msg.raw) - CBS_len(binders) - 2,
540 context, &context_len, hs->transcript.Digest(), NULL)) {
541 return false;
542 }
543
544 uint8_t verify_data[EVP_MAX_MD_SIZE] = {0};
545 CBS binder;
546 if (!tls13_psk_binder(verify_data, hs->ssl->version, hs->transcript.Digest(),
547 session->master_key, session->master_key_length,
548 context, context_len, hash_len) ||
549 // We only consider the first PSK, so compare against the first binder.
550 !CBS_get_u8_length_prefixed(binders, &binder)) {
551 OPENSSL_PUT_ERROR(SSL, ERR_R_INTERNAL_ERROR);
552 return false;
553 }
554
555 bool binder_ok = CBS_len(&binder) == hash_len &&
556 CRYPTO_memcmp(CBS_data(&binder), verify_data, hash_len) == 0;
557 #if defined(BORINGSSL_UNSAFE_FUZZER_MODE)
558 binder_ok = true;
559 #endif
560 if (!binder_ok) {
561 OPENSSL_PUT_ERROR(SSL, SSL_R_DIGEST_CHECK_FAILED);
562 return false;
563 }
564
565 return true;
566 }
567
568 BSSL_NAMESPACE_END
569