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 <algorithm>
21 #include <utility>
22
23 #include <openssl/aead.h>
24 #include <openssl/bytestring.h>
25 #include <openssl/digest.h>
26 #include <openssl/hkdf.h>
27 #include <openssl/hmac.h>
28 #include <openssl/mem.h>
29
30 #include "../crypto/internal.h"
31 #include "internal.h"
32
33
34 BSSL_NAMESPACE_BEGIN
35
init_key_schedule(SSL_HANDSHAKE * hs,uint16_t version,const SSL_CIPHER * cipher)36 static bool init_key_schedule(SSL_HANDSHAKE *hs, uint16_t version,
37 const SSL_CIPHER *cipher) {
38 if (!hs->transcript.InitHash(version, cipher)) {
39 return false;
40 }
41
42 // Initialize the secret to the zero key.
43 hs->ResizeSecrets(hs->transcript.DigestLen());
44 OPENSSL_memset(hs->secret().data(), 0, hs->secret().size());
45
46 return true;
47 }
48
hkdf_extract_to_secret(SSL_HANDSHAKE * hs,Span<const uint8_t> in)49 static bool hkdf_extract_to_secret(SSL_HANDSHAKE *hs, Span<const uint8_t> in) {
50 size_t len;
51 if (!HKDF_extract(hs->secret().data(), &len, hs->transcript.Digest(),
52 in.data(), in.size(), hs->secret().data(),
53 hs->secret().size())) {
54 return false;
55 }
56 assert(len == hs->secret().size());
57 return true;
58 }
59
tls13_init_key_schedule(SSL_HANDSHAKE * hs,Span<const uint8_t> psk)60 bool tls13_init_key_schedule(SSL_HANDSHAKE *hs, Span<const uint8_t> psk) {
61 if (!init_key_schedule(hs, ssl_protocol_version(hs->ssl), hs->new_cipher)) {
62 return false;
63 }
64
65 hs->transcript.FreeBuffer();
66 return hkdf_extract_to_secret(hs, psk);
67 }
68
tls13_init_early_key_schedule(SSL_HANDSHAKE * hs,Span<const uint8_t> psk)69 bool tls13_init_early_key_schedule(SSL_HANDSHAKE *hs, Span<const uint8_t> psk) {
70 SSL *const ssl = hs->ssl;
71 return init_key_schedule(hs, ssl_session_protocol_version(ssl->session.get()),
72 ssl->session->cipher) &&
73 hkdf_extract_to_secret(hs, psk);
74 }
75
label_to_span(const char * label)76 static Span<const char> label_to_span(const char *label) {
77 return MakeConstSpan(label, strlen(label));
78 }
79
hkdf_expand_label(Span<uint8_t> out,const EVP_MD * digest,Span<const uint8_t> secret,Span<const char> label,Span<const uint8_t> hash)80 static bool hkdf_expand_label(Span<uint8_t> out, const EVP_MD *digest,
81 Span<const uint8_t> secret,
82 Span<const char> label,
83 Span<const uint8_t> hash) {
84 Span<const char> protocol_label = label_to_span("tls13 ");
85 ScopedCBB cbb;
86 CBB child;
87 Array<uint8_t> hkdf_label;
88 if (!CBB_init(cbb.get(), 2 + 1 + protocol_label.size() + label.size() + 1 +
89 hash.size()) ||
90 !CBB_add_u16(cbb.get(), out.size()) ||
91 !CBB_add_u8_length_prefixed(cbb.get(), &child) ||
92 !CBB_add_bytes(&child,
93 reinterpret_cast<const uint8_t *>(protocol_label.data()),
94 protocol_label.size()) ||
95 !CBB_add_bytes(&child, reinterpret_cast<const uint8_t *>(label.data()),
96 label.size()) ||
97 !CBB_add_u8_length_prefixed(cbb.get(), &child) ||
98 !CBB_add_bytes(&child, hash.data(), hash.size()) ||
99 !CBBFinishArray(cbb.get(), &hkdf_label)) {
100 return false;
101 }
102
103 return HKDF_expand(out.data(), out.size(), digest, secret.data(),
104 secret.size(), hkdf_label.data(), hkdf_label.size());
105 }
106
107 static const char kTLS13LabelDerived[] = "derived";
108
tls13_advance_key_schedule(SSL_HANDSHAKE * hs,Span<const uint8_t> in)109 bool tls13_advance_key_schedule(SSL_HANDSHAKE *hs, Span<const uint8_t> in) {
110 uint8_t derive_context[EVP_MAX_MD_SIZE];
111 unsigned derive_context_len;
112 return EVP_Digest(nullptr, 0, derive_context, &derive_context_len,
113 hs->transcript.Digest(), nullptr) &&
114 hkdf_expand_label(hs->secret(), hs->transcript.Digest(), hs->secret(),
115 label_to_span(kTLS13LabelDerived),
116 MakeConstSpan(derive_context, derive_context_len)) &&
117 hkdf_extract_to_secret(hs, in);
118 }
119
120 // derive_secret derives a secret of length |out.size()| and writes the result
121 // in |out| with the given label, the current base secret, and the most
122 // recently-saved handshake context. It returns true on success and false on
123 // error.
derive_secret(SSL_HANDSHAKE * hs,Span<uint8_t> out,Span<const char> label)124 static bool derive_secret(SSL_HANDSHAKE *hs, Span<uint8_t> out,
125 Span<const char> label) {
126 uint8_t context_hash[EVP_MAX_MD_SIZE];
127 size_t context_hash_len;
128 if (!hs->transcript.GetHash(context_hash, &context_hash_len)) {
129 return false;
130 }
131
132 return hkdf_expand_label(out, hs->transcript.Digest(), hs->secret(), label,
133 MakeConstSpan(context_hash, context_hash_len));
134 }
135
tls13_set_traffic_key(SSL * ssl,enum ssl_encryption_level_t level,enum evp_aead_direction_t direction,Span<const uint8_t> traffic_secret)136 bool tls13_set_traffic_key(SSL *ssl, enum ssl_encryption_level_t level,
137 enum evp_aead_direction_t direction,
138 Span<const uint8_t> traffic_secret) {
139 const SSL_SESSION *session = SSL_get_session(ssl);
140 uint16_t version = ssl_session_protocol_version(session);
141
142 UniquePtr<SSLAEADContext> traffic_aead;
143 if (ssl->quic_method == nullptr) {
144 // Look up cipher suite properties.
145 const EVP_AEAD *aead;
146 size_t discard;
147 if (!ssl_cipher_get_evp_aead(&aead, &discard, &discard, session->cipher,
148 version, SSL_is_dtls(ssl))) {
149 return false;
150 }
151
152 const EVP_MD *digest = ssl_session_get_digest(session);
153
154 // Derive the key.
155 size_t key_len = EVP_AEAD_key_length(aead);
156 uint8_t key_buf[EVP_AEAD_MAX_KEY_LENGTH];
157 auto key = MakeSpan(key_buf, key_len);
158 if (!hkdf_expand_label(key, digest, traffic_secret, label_to_span("key"),
159 {})) {
160 return false;
161 }
162
163 // Derive the IV.
164 size_t iv_len = EVP_AEAD_nonce_length(aead);
165 uint8_t iv_buf[EVP_AEAD_MAX_NONCE_LENGTH];
166 auto iv = MakeSpan(iv_buf, iv_len);
167 if (!hkdf_expand_label(iv, digest, traffic_secret, label_to_span("iv"),
168 {})) {
169 return false;
170 }
171
172
173 traffic_aead = SSLAEADContext::Create(direction, session->ssl_version,
174 SSL_is_dtls(ssl), session->cipher,
175 key, Span<const uint8_t>(), iv);
176 } else {
177 // Install a placeholder SSLAEADContext so that SSL accessors work. The
178 // encryption itself will be handled by the SSL_QUIC_METHOD.
179 traffic_aead =
180 SSLAEADContext::CreatePlaceholderForQUIC(version, session->cipher);
181 // QUIC never installs early data keys at the TLS layer.
182 assert(level != ssl_encryption_early_data);
183 }
184
185 if (!traffic_aead) {
186 return false;
187 }
188
189 if (direction == evp_aead_open) {
190 if (!ssl->method->set_read_state(ssl, std::move(traffic_aead))) {
191 return false;
192 }
193 } else {
194 if (!ssl->method->set_write_state(ssl, std::move(traffic_aead))) {
195 return false;
196 }
197 }
198
199 // Save the traffic secret.
200 if (traffic_secret.size() >
201 OPENSSL_ARRAY_SIZE(ssl->s3->read_traffic_secret) ||
202 traffic_secret.size() >
203 OPENSSL_ARRAY_SIZE(ssl->s3->write_traffic_secret)) {
204 OPENSSL_PUT_ERROR(SSL, ERR_R_INTERNAL_ERROR);
205 return false;
206 }
207 if (direction == evp_aead_open) {
208 OPENSSL_memmove(ssl->s3->read_traffic_secret, traffic_secret.data(),
209 traffic_secret.size());
210 ssl->s3->read_traffic_secret_len = traffic_secret.size();
211 ssl->s3->read_level = level;
212 } else {
213 OPENSSL_memmove(ssl->s3->write_traffic_secret, traffic_secret.data(),
214 traffic_secret.size());
215 ssl->s3->write_traffic_secret_len = traffic_secret.size();
216 ssl->s3->write_level = level;
217 }
218
219 return true;
220 }
221
222
223 static const char kTLS13LabelExporter[] = "exp master";
224
225 static const char kTLS13LabelClientEarlyTraffic[] = "c e traffic";
226 static const char kTLS13LabelClientHandshakeTraffic[] = "c hs traffic";
227 static const char kTLS13LabelServerHandshakeTraffic[] = "s hs traffic";
228 static const char kTLS13LabelClientApplicationTraffic[] = "c ap traffic";
229 static const char kTLS13LabelServerApplicationTraffic[] = "s ap traffic";
230
tls13_derive_early_secret(SSL_HANDSHAKE * hs)231 bool tls13_derive_early_secret(SSL_HANDSHAKE *hs) {
232 SSL *const ssl = hs->ssl;
233 if (!derive_secret(hs, hs->early_traffic_secret(),
234 label_to_span(kTLS13LabelClientEarlyTraffic)) ||
235 !ssl_log_secret(ssl, "CLIENT_EARLY_TRAFFIC_SECRET",
236 hs->early_traffic_secret())) {
237 return false;
238 }
239 return true;
240 }
241
tls13_set_early_secret_for_quic(SSL_HANDSHAKE * hs)242 bool tls13_set_early_secret_for_quic(SSL_HANDSHAKE *hs) {
243 SSL *const ssl = hs->ssl;
244 if (ssl->quic_method == nullptr) {
245 return true;
246 }
247 if (ssl->server) {
248 if (!ssl->quic_method->set_encryption_secrets(
249 ssl, ssl_encryption_early_data, hs->early_traffic_secret().data(),
250 /*write_secret=*/nullptr, hs->early_traffic_secret().size())) {
251 OPENSSL_PUT_ERROR(SSL, SSL_R_QUIC_INTERNAL_ERROR);
252 return false;
253 }
254 } else {
255 if (!ssl->quic_method->set_encryption_secrets(
256 ssl, ssl_encryption_early_data, /*read_secret=*/nullptr,
257 hs->early_traffic_secret().data(),
258 hs->early_traffic_secret().size())) {
259 OPENSSL_PUT_ERROR(SSL, SSL_R_QUIC_INTERNAL_ERROR);
260 return false;
261 }
262 }
263 return true;
264 }
265
set_quic_secrets(SSL_HANDSHAKE * hs,ssl_encryption_level_t level,Span<const uint8_t> client_write_secret,Span<const uint8_t> server_write_secret)266 static bool set_quic_secrets(SSL_HANDSHAKE *hs, ssl_encryption_level_t level,
267 Span<const uint8_t> client_write_secret,
268 Span<const uint8_t> server_write_secret) {
269 SSL *const ssl = hs->ssl;
270 assert(client_write_secret.size() == server_write_secret.size());
271 if (ssl->quic_method == nullptr) {
272 return true;
273 }
274 if (!ssl->server) {
275 std::swap(client_write_secret, server_write_secret);
276 }
277 return ssl->quic_method->set_encryption_secrets(
278 ssl, level,
279 /*read_secret=*/client_write_secret.data(),
280 /*write_secret=*/server_write_secret.data(), client_write_secret.size());
281 }
282
tls13_derive_handshake_secrets(SSL_HANDSHAKE * hs)283 bool tls13_derive_handshake_secrets(SSL_HANDSHAKE *hs) {
284 SSL *const ssl = hs->ssl;
285 if (!derive_secret(hs, hs->client_handshake_secret(),
286 label_to_span(kTLS13LabelClientHandshakeTraffic)) ||
287 !ssl_log_secret(ssl, "CLIENT_HANDSHAKE_TRAFFIC_SECRET",
288 hs->client_handshake_secret()) ||
289 !derive_secret(hs, hs->server_handshake_secret(),
290 label_to_span(kTLS13LabelServerHandshakeTraffic)) ||
291 !ssl_log_secret(ssl, "SERVER_HANDSHAKE_TRAFFIC_SECRET",
292 hs->server_handshake_secret()) ||
293 !set_quic_secrets(hs, ssl_encryption_handshake,
294 hs->client_handshake_secret(),
295 hs->server_handshake_secret())) {
296 return false;
297 }
298
299 return true;
300 }
301
tls13_derive_application_secrets(SSL_HANDSHAKE * hs)302 bool tls13_derive_application_secrets(SSL_HANDSHAKE *hs) {
303 SSL *const ssl = hs->ssl;
304 ssl->s3->exporter_secret_len = hs->transcript.DigestLen();
305 if (!derive_secret(hs, hs->client_traffic_secret_0(),
306 label_to_span(kTLS13LabelClientApplicationTraffic)) ||
307 !ssl_log_secret(ssl, "CLIENT_TRAFFIC_SECRET_0",
308 hs->client_traffic_secret_0()) ||
309 !derive_secret(hs, hs->server_traffic_secret_0(),
310 label_to_span(kTLS13LabelServerApplicationTraffic)) ||
311 !ssl_log_secret(ssl, "SERVER_TRAFFIC_SECRET_0",
312 hs->server_traffic_secret_0()) ||
313 !derive_secret(
314 hs, MakeSpan(ssl->s3->exporter_secret, ssl->s3->exporter_secret_len),
315 label_to_span(kTLS13LabelExporter)) ||
316 !ssl_log_secret(ssl, "EXPORTER_SECRET",
317 MakeConstSpan(ssl->s3->exporter_secret,
318 ssl->s3->exporter_secret_len)) ||
319 !set_quic_secrets(hs, ssl_encryption_application,
320 hs->client_traffic_secret_0(),
321 hs->server_traffic_secret_0())) {
322 return false;
323 }
324
325 return true;
326 }
327
328 static const char kTLS13LabelApplicationTraffic[] = "traffic upd";
329
tls13_rotate_traffic_key(SSL * ssl,enum evp_aead_direction_t direction)330 bool tls13_rotate_traffic_key(SSL *ssl, enum evp_aead_direction_t direction) {
331 Span<uint8_t> secret;
332 if (direction == evp_aead_open) {
333 secret = MakeSpan(ssl->s3->read_traffic_secret,
334 ssl->s3->read_traffic_secret_len);
335 } else {
336 secret = MakeSpan(ssl->s3->write_traffic_secret,
337 ssl->s3->write_traffic_secret_len);
338 }
339
340 const EVP_MD *digest = ssl_session_get_digest(SSL_get_session(ssl));
341 return hkdf_expand_label(secret, digest, secret,
342 label_to_span(kTLS13LabelApplicationTraffic), {}) &&
343 tls13_set_traffic_key(ssl, ssl_encryption_application, direction,
344 secret);
345 }
346
347 static const char kTLS13LabelResumption[] = "res master";
348
tls13_derive_resumption_secret(SSL_HANDSHAKE * hs)349 bool tls13_derive_resumption_secret(SSL_HANDSHAKE *hs) {
350 if (hs->transcript.DigestLen() > SSL_MAX_MASTER_KEY_LENGTH) {
351 OPENSSL_PUT_ERROR(SSL, ERR_R_INTERNAL_ERROR);
352 return false;
353 }
354 hs->new_session->master_key_length = hs->transcript.DigestLen();
355 return derive_secret(
356 hs,
357 MakeSpan(hs->new_session->master_key, hs->new_session->master_key_length),
358 label_to_span(kTLS13LabelResumption));
359 }
360
361 static const char kTLS13LabelFinished[] = "finished";
362
363 // tls13_verify_data sets |out| to be the HMAC of |context| using a derived
364 // Finished key for both Finished messages and the PSK binder. |out| must have
365 // space available for |EVP_MAX_MD_SIZE| bytes.
tls13_verify_data(uint8_t * out,size_t * out_len,const EVP_MD * digest,uint16_t version,Span<const uint8_t> secret,Span<const uint8_t> context)366 static bool tls13_verify_data(uint8_t *out, size_t *out_len,
367 const EVP_MD *digest, uint16_t version,
368 Span<const uint8_t> secret,
369 Span<const uint8_t> context) {
370 uint8_t key_buf[EVP_MAX_MD_SIZE];
371 auto key = MakeSpan(key_buf, EVP_MD_size(digest));
372 unsigned len;
373 if (!hkdf_expand_label(key, digest, secret,
374 label_to_span(kTLS13LabelFinished), {}) ||
375 HMAC(digest, key.data(), key.size(), context.data(), context.size(), out,
376 &len) == nullptr) {
377 return false;
378 }
379 *out_len = len;
380 return true;
381 }
382
tls13_finished_mac(SSL_HANDSHAKE * hs,uint8_t * out,size_t * out_len,bool is_server)383 bool tls13_finished_mac(SSL_HANDSHAKE *hs, uint8_t *out, size_t *out_len,
384 bool is_server) {
385 Span<const uint8_t> traffic_secret =
386 is_server ? hs->server_handshake_secret() : hs->client_handshake_secret();
387
388 uint8_t context_hash[EVP_MAX_MD_SIZE];
389 size_t context_hash_len;
390 if (!hs->transcript.GetHash(context_hash, &context_hash_len) ||
391 !tls13_verify_data(out, out_len, hs->transcript.Digest(),
392 hs->ssl->version, traffic_secret,
393 MakeConstSpan(context_hash, context_hash_len))) {
394 return 0;
395 }
396 return 1;
397 }
398
399 static const char kTLS13LabelResumptionPSK[] = "resumption";
400
tls13_derive_session_psk(SSL_SESSION * session,Span<const uint8_t> nonce)401 bool tls13_derive_session_psk(SSL_SESSION *session, Span<const uint8_t> nonce) {
402 const EVP_MD *digest = ssl_session_get_digest(session);
403 // The session initially stores the resumption_master_secret, which we
404 // override with the PSK.
405 auto session_key = MakeSpan(session->master_key, session->master_key_length);
406 return hkdf_expand_label(session_key, digest, session_key,
407 label_to_span(kTLS13LabelResumptionPSK), nonce);
408 }
409
410 static const char kTLS13LabelExportKeying[] = "exporter";
411
tls13_export_keying_material(SSL * ssl,Span<uint8_t> out,Span<const uint8_t> secret,Span<const char> label,Span<const uint8_t> context)412 bool tls13_export_keying_material(SSL *ssl, Span<uint8_t> out,
413 Span<const uint8_t> secret,
414 Span<const char> label,
415 Span<const uint8_t> context) {
416 if (secret.empty()) {
417 assert(0);
418 OPENSSL_PUT_ERROR(SSL, ERR_R_INTERNAL_ERROR);
419 return false;
420 }
421
422 const EVP_MD *digest = ssl_session_get_digest(SSL_get_session(ssl));
423
424 uint8_t hash_buf[EVP_MAX_MD_SIZE];
425 uint8_t export_context_buf[EVP_MAX_MD_SIZE];
426 unsigned hash_len;
427 unsigned export_context_len;
428 if (!EVP_Digest(context.data(), context.size(), hash_buf, &hash_len, digest,
429 nullptr) ||
430 !EVP_Digest(nullptr, 0, export_context_buf, &export_context_len, digest,
431 nullptr)) {
432 return false;
433 }
434
435 auto hash = MakeConstSpan(hash_buf, hash_len);
436 auto export_context = MakeConstSpan(export_context_buf, export_context_len);
437 uint8_t derived_secret_buf[EVP_MAX_MD_SIZE];
438 auto derived_secret = MakeSpan(derived_secret_buf, EVP_MD_size(digest));
439 return hkdf_expand_label(derived_secret, digest, secret, label,
440 export_context) &&
441 hkdf_expand_label(out, digest, derived_secret,
442 label_to_span(kTLS13LabelExportKeying), hash);
443 }
444
445 static const char kTLS13LabelPSKBinder[] = "res binder";
446
tls13_psk_binder(uint8_t * out,size_t * out_len,uint16_t version,const EVP_MD * digest,Span<const uint8_t> psk,Span<const uint8_t> context)447 static bool tls13_psk_binder(uint8_t *out, size_t *out_len, uint16_t version,
448 const EVP_MD *digest, Span<const uint8_t> psk,
449 Span<const uint8_t> context) {
450 uint8_t binder_context[EVP_MAX_MD_SIZE];
451 unsigned binder_context_len;
452 if (!EVP_Digest(NULL, 0, binder_context, &binder_context_len, digest, NULL)) {
453 return false;
454 }
455
456 uint8_t early_secret[EVP_MAX_MD_SIZE] = {0};
457 size_t early_secret_len;
458 if (!HKDF_extract(early_secret, &early_secret_len, digest, psk.data(),
459 psk.size(), NULL, 0)) {
460 return false;
461 }
462
463 uint8_t binder_key_buf[EVP_MAX_MD_SIZE] = {0};
464 auto binder_key = MakeSpan(binder_key_buf, EVP_MD_size(digest));
465 if (!hkdf_expand_label(binder_key, digest,
466 MakeConstSpan(early_secret, early_secret_len),
467 label_to_span(kTLS13LabelPSKBinder),
468 MakeConstSpan(binder_context, binder_context_len)) ||
469 !tls13_verify_data(out, out_len, digest, version, binder_key, context)) {
470 return false;
471 }
472
473 assert(*out_len == EVP_MD_size(digest));
474 return true;
475 }
476
hash_transcript_and_truncated_client_hello(SSL_HANDSHAKE * hs,uint8_t * out,size_t * out_len,const EVP_MD * digest,Span<const uint8_t> client_hello,size_t binders_len)477 static bool hash_transcript_and_truncated_client_hello(
478 SSL_HANDSHAKE *hs, uint8_t *out, size_t *out_len, const EVP_MD *digest,
479 Span<const uint8_t> client_hello, size_t binders_len) {
480 // Truncate the ClientHello.
481 if (binders_len + 2 < binders_len || client_hello.size() < binders_len + 2) {
482 return false;
483 }
484 client_hello = client_hello.subspan(0, client_hello.size() - binders_len - 2);
485
486 ScopedEVP_MD_CTX ctx;
487 unsigned len;
488 if (!hs->transcript.CopyToHashContext(ctx.get(), digest) ||
489 !EVP_DigestUpdate(ctx.get(), client_hello.data(), client_hello.size()) ||
490 !EVP_DigestFinal_ex(ctx.get(), out, &len)) {
491 return false;
492 }
493
494 *out_len = len;
495 return true;
496 }
497
tls13_write_psk_binder(SSL_HANDSHAKE * hs,Span<uint8_t> msg)498 bool tls13_write_psk_binder(SSL_HANDSHAKE *hs, Span<uint8_t> msg) {
499 SSL *const ssl = hs->ssl;
500 const EVP_MD *digest = ssl_session_get_digest(ssl->session.get());
501 size_t hash_len = EVP_MD_size(digest);
502
503 ScopedEVP_MD_CTX ctx;
504 uint8_t context[EVP_MAX_MD_SIZE];
505 size_t context_len;
506 uint8_t verify_data[EVP_MAX_MD_SIZE];
507 size_t verify_data_len;
508 if (!hash_transcript_and_truncated_client_hello(
509 hs, context, &context_len, digest, msg,
510 1 /* length prefix */ + hash_len) ||
511 !tls13_psk_binder(verify_data, &verify_data_len,
512 ssl->session->ssl_version, digest,
513 MakeConstSpan(ssl->session->master_key,
514 ssl->session->master_key_length),
515 MakeConstSpan(context, context_len)) ||
516 verify_data_len != hash_len) {
517 OPENSSL_PUT_ERROR(SSL, ERR_R_INTERNAL_ERROR);
518 return false;
519 }
520
521 OPENSSL_memcpy(msg.data() + msg.size() - verify_data_len, verify_data,
522 verify_data_len);
523 return true;
524 }
525
tls13_verify_psk_binder(SSL_HANDSHAKE * hs,SSL_SESSION * session,const SSLMessage & msg,CBS * binders)526 bool tls13_verify_psk_binder(SSL_HANDSHAKE *hs, SSL_SESSION *session,
527 const SSLMessage &msg, CBS *binders) {
528 uint8_t context[EVP_MAX_MD_SIZE];
529 size_t context_len;
530 uint8_t verify_data[EVP_MAX_MD_SIZE];
531 size_t verify_data_len;
532 CBS binder;
533 if (!hash_transcript_and_truncated_client_hello(hs, context, &context_len,
534 hs->transcript.Digest(),
535 msg.raw, CBS_len(binders)) ||
536 !tls13_psk_binder(
537 verify_data, &verify_data_len, hs->ssl->version,
538 hs->transcript.Digest(),
539 MakeConstSpan(session->master_key, session->master_key_length),
540 MakeConstSpan(context, context_len)) ||
541 // We only consider the first PSK, so compare against the first binder.
542 !CBS_get_u8_length_prefixed(binders, &binder)) {
543 OPENSSL_PUT_ERROR(SSL, ERR_R_INTERNAL_ERROR);
544 return false;
545 }
546
547 bool binder_ok =
548 CBS_len(&binder) == verify_data_len &&
549 CRYPTO_memcmp(CBS_data(&binder), verify_data, verify_data_len) == 0;
550 #if defined(BORINGSSL_UNSAFE_FUZZER_MODE)
551 binder_ok = true;
552 #endif
553 if (!binder_ok) {
554 OPENSSL_PUT_ERROR(SSL, SSL_R_DIGEST_CHECK_FAILED);
555 return false;
556 }
557
558 return true;
559 }
560
561 BSSL_NAMESPACE_END
562