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 | |
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 | |
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 | |
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 | |
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 | |
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. |
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 | |
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 | |
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 | |
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 | |
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 | |
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 | |
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. |
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 | |
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 | |
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 | |
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 | |
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 | |
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 | |
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 | |