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