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 <openssl/aead.h>
21 #include <openssl/bytestring.h>
22 #include <openssl/digest.h>
23 #include <openssl/hkdf.h>
24 #include <openssl/hmac.h>
25 #include <openssl/mem.h>
26
27 #include "../crypto/internal.h"
28 #include "internal.h"
29
30
init_key_schedule(SSL_HANDSHAKE * hs,uint16_t version,int algorithm_prf)31 static int init_key_schedule(SSL_HANDSHAKE *hs, uint16_t version,
32 int algorithm_prf) {
33 if (!SSL_TRANSCRIPT_init_hash(&hs->transcript, version, algorithm_prf)) {
34 return 0;
35 }
36
37 hs->hash_len = SSL_TRANSCRIPT_digest_len(&hs->transcript);
38
39 /* Initialize the secret to the zero key. */
40 OPENSSL_memset(hs->secret, 0, hs->hash_len);
41
42 return 1;
43 }
44
tls13_init_key_schedule(SSL_HANDSHAKE * hs)45 int tls13_init_key_schedule(SSL_HANDSHAKE *hs) {
46 if (!init_key_schedule(hs, ssl3_protocol_version(hs->ssl),
47 hs->new_cipher->algorithm_prf)) {
48 return 0;
49 }
50
51 SSL_TRANSCRIPT_free_buffer(&hs->transcript);
52 return 1;
53 }
54
tls13_init_early_key_schedule(SSL_HANDSHAKE * hs)55 int tls13_init_early_key_schedule(SSL_HANDSHAKE *hs) {
56 SSL *const ssl = hs->ssl;
57 uint16_t session_version;
58 if (!ssl->method->version_from_wire(&session_version,
59 ssl->session->ssl_version) ||
60 !init_key_schedule(hs, session_version,
61 ssl->session->cipher->algorithm_prf)) {
62 return 0;
63 }
64
65 return 1;
66 }
67
tls13_advance_key_schedule(SSL_HANDSHAKE * hs,const uint8_t * in,size_t len)68 int tls13_advance_key_schedule(SSL_HANDSHAKE *hs, const uint8_t *in,
69 size_t len) {
70 return HKDF_extract(hs->secret, &hs->hash_len,
71 SSL_TRANSCRIPT_md(&hs->transcript), in, len, hs->secret,
72 hs->hash_len);
73 }
74
hkdf_expand_label(uint8_t * out,const EVP_MD * digest,const uint8_t * secret,size_t secret_len,const uint8_t * label,size_t label_len,const uint8_t * hash,size_t hash_len,size_t len)75 static int hkdf_expand_label(uint8_t *out, const EVP_MD *digest,
76 const uint8_t *secret, size_t secret_len,
77 const uint8_t *label, size_t label_len,
78 const uint8_t *hash, size_t hash_len, size_t len) {
79 static const char kTLS13LabelVersion[] = "TLS 1.3, ";
80
81 CBB cbb, child;
82 uint8_t *hkdf_label;
83 size_t hkdf_label_len;
84 if (!CBB_init(&cbb, 2 + 1 + strlen(kTLS13LabelVersion) + label_len + 1 +
85 hash_len) ||
86 !CBB_add_u16(&cbb, len) ||
87 !CBB_add_u8_length_prefixed(&cbb, &child) ||
88 !CBB_add_bytes(&child, (const uint8_t *)kTLS13LabelVersion,
89 strlen(kTLS13LabelVersion)) ||
90 !CBB_add_bytes(&child, label, label_len) ||
91 !CBB_add_u8_length_prefixed(&cbb, &child) ||
92 !CBB_add_bytes(&child, hash, hash_len) ||
93 !CBB_finish(&cbb, &hkdf_label, &hkdf_label_len)) {
94 CBB_cleanup(&cbb);
95 return 0;
96 }
97
98 int ret = HKDF_expand(out, len, digest, secret, secret_len, hkdf_label,
99 hkdf_label_len);
100 OPENSSL_free(hkdf_label);
101 return ret;
102 }
103
104 /* derive_secret derives a secret of length |len| and writes the result in |out|
105 * with the given label and the current base secret and most recently-saved
106 * handshake context. It returns one on success and zero on error. */
derive_secret(SSL_HANDSHAKE * hs,uint8_t * out,size_t len,const uint8_t * label,size_t label_len)107 static int derive_secret(SSL_HANDSHAKE *hs, uint8_t *out, size_t len,
108 const uint8_t *label, size_t label_len) {
109 uint8_t context_hash[EVP_MAX_MD_SIZE];
110 size_t context_hash_len;
111 if (!SSL_TRANSCRIPT_get_hash(&hs->transcript, context_hash,
112 &context_hash_len)) {
113 return 0;
114 }
115
116 return hkdf_expand_label(out, SSL_TRANSCRIPT_md(&hs->transcript), hs->secret,
117 hs->hash_len, label, label_len, context_hash,
118 context_hash_len, len);
119 }
120
tls13_set_traffic_key(SSL * ssl,enum evp_aead_direction_t direction,const uint8_t * traffic_secret,size_t traffic_secret_len)121 int tls13_set_traffic_key(SSL *ssl, enum evp_aead_direction_t direction,
122 const uint8_t *traffic_secret,
123 size_t traffic_secret_len) {
124 const SSL_SESSION *session = SSL_get_session(ssl);
125 uint16_t version;
126 if (!ssl->method->version_from_wire(&version, session->ssl_version)) {
127 OPENSSL_PUT_ERROR(SSL, ERR_R_INTERNAL_ERROR);
128 return 0;
129 }
130
131 if (traffic_secret_len > 0xff) {
132 OPENSSL_PUT_ERROR(SSL, ERR_R_OVERFLOW);
133 return 0;
134 }
135
136 /* Look up cipher suite properties. */
137 const EVP_AEAD *aead;
138 size_t discard;
139 if (!ssl_cipher_get_evp_aead(&aead, &discard, &discard, session->cipher,
140 version)) {
141 return 0;
142 }
143
144 const EVP_MD *digest = ssl_get_handshake_digest(
145 session->cipher->algorithm_prf, version);
146
147 /* Derive the key. */
148 size_t key_len = EVP_AEAD_key_length(aead);
149 uint8_t key[EVP_AEAD_MAX_KEY_LENGTH];
150 if (!hkdf_expand_label(key, digest, traffic_secret, traffic_secret_len,
151 (const uint8_t *)"key", 3, NULL, 0, key_len)) {
152 return 0;
153 }
154
155 /* Derive the IV. */
156 size_t iv_len = EVP_AEAD_nonce_length(aead);
157 uint8_t iv[EVP_AEAD_MAX_NONCE_LENGTH];
158 if (!hkdf_expand_label(iv, digest, traffic_secret, traffic_secret_len,
159 (const uint8_t *)"iv", 2, NULL, 0, iv_len)) {
160 return 0;
161 }
162
163 SSL_AEAD_CTX *traffic_aead = SSL_AEAD_CTX_new(
164 direction, version, session->cipher, key, key_len, NULL, 0, iv, iv_len);
165 if (traffic_aead == NULL) {
166 return 0;
167 }
168
169 if (direction == evp_aead_open) {
170 if (!ssl->method->set_read_state(ssl, traffic_aead)) {
171 return 0;
172 }
173 } else {
174 if (!ssl->method->set_write_state(ssl, traffic_aead)) {
175 return 0;
176 }
177 }
178
179 /* Save the traffic secret. */
180 if (direction == evp_aead_open) {
181 OPENSSL_memmove(ssl->s3->read_traffic_secret, traffic_secret,
182 traffic_secret_len);
183 ssl->s3->read_traffic_secret_len = traffic_secret_len;
184 } else {
185 OPENSSL_memmove(ssl->s3->write_traffic_secret, traffic_secret,
186 traffic_secret_len);
187 ssl->s3->write_traffic_secret_len = traffic_secret_len;
188 }
189
190 return 1;
191 }
192
193 static const char kTLS13LabelExporter[] = "exporter master secret";
194 static const char kTLS13LabelEarlyExporter[] = "early exporter master secret";
195
196 static const char kTLS13LabelClientEarlyTraffic[] =
197 "client early traffic secret";
198 static const char kTLS13LabelClientHandshakeTraffic[] =
199 "client handshake traffic secret";
200 static const char kTLS13LabelServerHandshakeTraffic[] =
201 "server handshake traffic secret";
202 static const char kTLS13LabelClientApplicationTraffic[] =
203 "client application traffic secret";
204 static const char kTLS13LabelServerApplicationTraffic[] =
205 "server application traffic secret";
206
tls13_derive_early_secrets(SSL_HANDSHAKE * hs)207 int tls13_derive_early_secrets(SSL_HANDSHAKE *hs) {
208 SSL *const ssl = hs->ssl;
209 return derive_secret(hs, hs->early_traffic_secret, hs->hash_len,
210 (const uint8_t *)kTLS13LabelClientEarlyTraffic,
211 strlen(kTLS13LabelClientEarlyTraffic)) &&
212 ssl_log_secret(ssl, "CLIENT_EARLY_TRAFFIC_SECRET",
213 hs->early_traffic_secret, hs->hash_len) &&
214 derive_secret(hs, ssl->s3->early_exporter_secret, hs->hash_len,
215 (const uint8_t *)kTLS13LabelEarlyExporter,
216 strlen(kTLS13LabelEarlyExporter));
217 }
218
tls13_derive_handshake_secrets(SSL_HANDSHAKE * hs)219 int tls13_derive_handshake_secrets(SSL_HANDSHAKE *hs) {
220 SSL *const ssl = hs->ssl;
221 return derive_secret(hs, hs->client_handshake_secret, hs->hash_len,
222 (const uint8_t *)kTLS13LabelClientHandshakeTraffic,
223 strlen(kTLS13LabelClientHandshakeTraffic)) &&
224 ssl_log_secret(ssl, "CLIENT_HANDSHAKE_TRAFFIC_SECRET",
225 hs->client_handshake_secret, hs->hash_len) &&
226 derive_secret(hs, hs->server_handshake_secret, hs->hash_len,
227 (const uint8_t *)kTLS13LabelServerHandshakeTraffic,
228 strlen(kTLS13LabelServerHandshakeTraffic)) &&
229 ssl_log_secret(ssl, "SERVER_HANDSHAKE_TRAFFIC_SECRET",
230 hs->server_handshake_secret, hs->hash_len);
231 }
232
tls13_derive_application_secrets(SSL_HANDSHAKE * hs)233 int tls13_derive_application_secrets(SSL_HANDSHAKE *hs) {
234 SSL *const ssl = hs->ssl;
235 ssl->s3->exporter_secret_len = hs->hash_len;
236 return derive_secret(hs, hs->client_traffic_secret_0, hs->hash_len,
237 (const uint8_t *)kTLS13LabelClientApplicationTraffic,
238 strlen(kTLS13LabelClientApplicationTraffic)) &&
239 ssl_log_secret(ssl, "CLIENT_TRAFFIC_SECRET_0",
240 hs->client_traffic_secret_0, hs->hash_len) &&
241 derive_secret(hs, hs->server_traffic_secret_0, hs->hash_len,
242 (const uint8_t *)kTLS13LabelServerApplicationTraffic,
243 strlen(kTLS13LabelServerApplicationTraffic)) &&
244 ssl_log_secret(ssl, "SERVER_TRAFFIC_SECRET_0",
245 hs->server_traffic_secret_0, hs->hash_len) &&
246 derive_secret(hs, ssl->s3->exporter_secret, hs->hash_len,
247 (const uint8_t *)kTLS13LabelExporter,
248 strlen(kTLS13LabelExporter));
249 }
250
251 static const char kTLS13LabelApplicationTraffic[] =
252 "application traffic secret";
253
tls13_rotate_traffic_key(SSL * ssl,enum evp_aead_direction_t direction)254 int tls13_rotate_traffic_key(SSL *ssl, enum evp_aead_direction_t direction) {
255 const EVP_MD *digest = ssl_get_handshake_digest(
256 SSL_get_session(ssl)->cipher->algorithm_prf, ssl3_protocol_version(ssl));
257
258 uint8_t *secret;
259 size_t secret_len;
260 if (direction == evp_aead_open) {
261 secret = ssl->s3->read_traffic_secret;
262 secret_len = ssl->s3->read_traffic_secret_len;
263 } else {
264 secret = ssl->s3->write_traffic_secret;
265 secret_len = ssl->s3->write_traffic_secret_len;
266 }
267
268 if (!hkdf_expand_label(secret, digest, secret, secret_len,
269 (const uint8_t *)kTLS13LabelApplicationTraffic,
270 strlen(kTLS13LabelApplicationTraffic), NULL, 0,
271 secret_len)) {
272 return 0;
273 }
274
275 return tls13_set_traffic_key(ssl, direction, secret, secret_len);
276 }
277
278 static const char kTLS13LabelResumption[] = "resumption master secret";
279
tls13_derive_resumption_secret(SSL_HANDSHAKE * hs)280 int tls13_derive_resumption_secret(SSL_HANDSHAKE *hs) {
281 if (hs->hash_len > SSL_MAX_MASTER_KEY_LENGTH) {
282 OPENSSL_PUT_ERROR(SSL, ERR_R_INTERNAL_ERROR);
283 return 0;
284 }
285
286 hs->new_session->master_key_length = hs->hash_len;
287 return derive_secret(
288 hs, hs->new_session->master_key, hs->new_session->master_key_length,
289 (const uint8_t *)kTLS13LabelResumption, strlen(kTLS13LabelResumption));
290 }
291
292 static const char kTLS13LabelFinished[] = "finished";
293
294 /* tls13_verify_data sets |out| to be the HMAC of |context| using a derived
295 * Finished key for both Finished messages and the PSK binder. */
tls13_verify_data(const EVP_MD * digest,uint8_t * out,size_t * out_len,const uint8_t * secret,size_t hash_len,uint8_t * context,size_t context_len)296 static int tls13_verify_data(const EVP_MD *digest, uint8_t *out,
297 size_t *out_len, const uint8_t *secret,
298 size_t hash_len, uint8_t *context,
299 size_t context_len) {
300 uint8_t key[EVP_MAX_MD_SIZE];
301 unsigned len;
302 if (!hkdf_expand_label(key, digest, secret, hash_len,
303 (const uint8_t *)kTLS13LabelFinished,
304 strlen(kTLS13LabelFinished), NULL, 0, hash_len) ||
305 HMAC(digest, key, hash_len, context, context_len, out, &len) == NULL) {
306 return 0;
307 }
308 *out_len = len;
309 return 1;
310 }
311
tls13_finished_mac(SSL_HANDSHAKE * hs,uint8_t * out,size_t * out_len,int is_server)312 int tls13_finished_mac(SSL_HANDSHAKE *hs, uint8_t *out, size_t *out_len,
313 int is_server) {
314 const uint8_t *traffic_secret;
315 if (is_server) {
316 traffic_secret = hs->server_handshake_secret;
317 } else {
318 traffic_secret = hs->client_handshake_secret;
319 }
320
321 uint8_t context_hash[EVP_MAX_MD_SIZE];
322 size_t context_hash_len;
323 if (!SSL_TRANSCRIPT_get_hash(&hs->transcript, context_hash,
324 &context_hash_len) ||
325 !tls13_verify_data(SSL_TRANSCRIPT_md(&hs->transcript), out, out_len,
326 traffic_secret, hs->hash_len, context_hash,
327 context_hash_len)) {
328 return 0;
329 }
330 return 1;
331 }
332
tls13_export_keying_material(SSL * ssl,uint8_t * out,size_t out_len,const char * label,size_t label_len,const uint8_t * context,size_t context_len,int use_context)333 int tls13_export_keying_material(SSL *ssl, uint8_t *out, size_t out_len,
334 const char *label, size_t label_len,
335 const uint8_t *context, size_t context_len,
336 int use_context) {
337 const EVP_MD *digest = ssl_get_handshake_digest(
338 SSL_get_session(ssl)->cipher->algorithm_prf, ssl3_protocol_version(ssl));
339
340 const uint8_t *hash = NULL;
341 size_t hash_len = 0;
342 if (use_context) {
343 hash = context;
344 hash_len = context_len;
345 }
346 return hkdf_expand_label(out, digest, ssl->s3->exporter_secret,
347 ssl->s3->exporter_secret_len, (const uint8_t *)label,
348 label_len, hash, hash_len, out_len);
349 }
350
351 static const char kTLS13LabelPSKBinder[] = "resumption psk binder key";
352
tls13_psk_binder(uint8_t * out,const EVP_MD * digest,uint8_t * psk,size_t psk_len,uint8_t * context,size_t context_len,size_t hash_len)353 static int tls13_psk_binder(uint8_t *out, const EVP_MD *digest, uint8_t *psk,
354 size_t psk_len, uint8_t *context,
355 size_t context_len, size_t hash_len) {
356 uint8_t binder_context[EVP_MAX_MD_SIZE];
357 unsigned binder_context_len;
358 if (!EVP_Digest(NULL, 0, binder_context, &binder_context_len, digest, NULL)) {
359 return 0;
360 }
361
362 uint8_t early_secret[EVP_MAX_MD_SIZE] = {0};
363 size_t early_secret_len;
364 if (!HKDF_extract(early_secret, &early_secret_len, digest, psk, hash_len,
365 NULL, 0)) {
366 return 0;
367 }
368
369 uint8_t binder_key[EVP_MAX_MD_SIZE] = {0};
370 size_t len;
371 if (!hkdf_expand_label(binder_key, digest, early_secret, hash_len,
372 (const uint8_t *)kTLS13LabelPSKBinder,
373 strlen(kTLS13LabelPSKBinder), binder_context,
374 binder_context_len, hash_len) ||
375 !tls13_verify_data(digest, out, &len, binder_key, hash_len, context,
376 context_len)) {
377 return 0;
378 }
379
380 return 1;
381 }
382
tls13_write_psk_binder(SSL_HANDSHAKE * hs,uint8_t * msg,size_t len)383 int tls13_write_psk_binder(SSL_HANDSHAKE *hs, uint8_t *msg, size_t len) {
384 SSL *const ssl = hs->ssl;
385 const EVP_MD *digest = SSL_SESSION_get_digest(ssl->session, ssl);
386 if (digest == NULL) {
387 OPENSSL_PUT_ERROR(SSL, ERR_R_INTERNAL_ERROR);
388 return 0;
389 }
390 size_t hash_len = EVP_MD_size(digest);
391
392 if (len < hash_len + 3) {
393 OPENSSL_PUT_ERROR(SSL, ERR_R_INTERNAL_ERROR);
394 return 0;
395 }
396
397 EVP_MD_CTX ctx;
398 EVP_MD_CTX_init(&ctx);
399 uint8_t context[EVP_MAX_MD_SIZE];
400 unsigned context_len;
401 if (!EVP_DigestInit_ex(&ctx, digest, NULL) ||
402 !EVP_DigestUpdate(&ctx, hs->transcript.buffer->data,
403 hs->transcript.buffer->length) ||
404 !EVP_DigestUpdate(&ctx, msg, len - hash_len - 3) ||
405 !EVP_DigestFinal_ex(&ctx, context, &context_len)) {
406 EVP_MD_CTX_cleanup(&ctx);
407 return 0;
408 }
409
410 EVP_MD_CTX_cleanup(&ctx);
411
412 uint8_t verify_data[EVP_MAX_MD_SIZE] = {0};
413 if (!tls13_psk_binder(verify_data, digest, ssl->session->master_key,
414 ssl->session->master_key_length, context, context_len,
415 hash_len)) {
416 return 0;
417 }
418
419 OPENSSL_memcpy(msg + len - hash_len, verify_data, hash_len);
420 return 1;
421 }
422
tls13_verify_psk_binder(SSL_HANDSHAKE * hs,SSL_SESSION * session,CBS * binders)423 int tls13_verify_psk_binder(SSL_HANDSHAKE *hs, SSL_SESSION *session,
424 CBS *binders) {
425 size_t hash_len = SSL_TRANSCRIPT_digest_len(&hs->transcript);
426
427 /* Get the full ClientHello, including message header. It must be large enough
428 * to exclude the binders. */
429 CBS message;
430 hs->ssl->method->get_current_message(hs->ssl, &message);
431 if (CBS_len(&message) < CBS_len(binders) + 2) {
432 OPENSSL_PUT_ERROR(SSL, ERR_R_INTERNAL_ERROR);
433 return 0;
434 }
435
436 /* Hash a ClientHello prefix up to the binders. For now, this assumes we only
437 * ever verify PSK binders on initial ClientHellos. */
438 uint8_t context[EVP_MAX_MD_SIZE];
439 unsigned context_len;
440 if (!EVP_Digest(CBS_data(&message), CBS_len(&message) - CBS_len(binders) - 2,
441 context, &context_len, SSL_TRANSCRIPT_md(&hs->transcript),
442 NULL)) {
443 return 0;
444 }
445
446 uint8_t verify_data[EVP_MAX_MD_SIZE] = {0};
447 CBS binder;
448 if (!tls13_psk_binder(verify_data, SSL_TRANSCRIPT_md(&hs->transcript),
449 session->master_key, session->master_key_length,
450 context, context_len, hash_len) ||
451 /* We only consider the first PSK, so compare against the first binder. */
452 !CBS_get_u8_length_prefixed(binders, &binder)) {
453 OPENSSL_PUT_ERROR(SSL, ERR_R_INTERNAL_ERROR);
454 return 0;
455 }
456
457 int binder_ok =
458 CBS_len(&binder) == hash_len &&
459 CRYPTO_memcmp(CBS_data(&binder), verify_data, hash_len) == 0;
460 #if defined(BORINGSSL_UNSAFE_FUZZER_MODE)
461 binder_ok = 1;
462 #endif
463 if (!binder_ok) {
464 OPENSSL_PUT_ERROR(SSL, SSL_R_DIGEST_CHECK_FAILED);
465 return 0;
466 }
467
468 return 1;
469 }
470