1 /*
2 * TLS server tickets callbacks implementation
3 *
4 * Copyright The Mbed TLS Contributors
5 * SPDX-License-Identifier: Apache-2.0 OR GPL-2.0-or-later
6 *
7 * This file is provided under the Apache License 2.0, or the
8 * GNU General Public License v2.0 or later.
9 *
10 * **********
11 * Apache License 2.0:
12 *
13 * Licensed under the Apache License, Version 2.0 (the "License"); you may
14 * not use this file except in compliance with the License.
15 * You may obtain a copy of the License at
16 *
17 * http://www.apache.org/licenses/LICENSE-2.0
18 *
19 * Unless required by applicable law or agreed to in writing, software
20 * distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
21 * WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
22 * See the License for the specific language governing permissions and
23 * limitations under the License.
24 *
25 * **********
26 *
27 * **********
28 * GNU General Public License v2.0 or later:
29 *
30 * This program is free software; you can redistribute it and/or modify
31 * it under the terms of the GNU General Public License as published by
32 * the Free Software Foundation; either version 2 of the License, or
33 * (at your option) any later version.
34 *
35 * This program is distributed in the hope that it will be useful,
36 * but WITHOUT ANY WARRANTY; without even the implied warranty of
37 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
38 * GNU General Public License for more details.
39 *
40 * You should have received a copy of the GNU General Public License along
41 * with this program; if not, write to the Free Software Foundation, Inc.,
42 * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
43 *
44 * **********
45 */
46
47 #if !defined(MBEDTLS_CONFIG_FILE)
48 #include "mbedtls/config.h"
49 #else
50 #include MBEDTLS_CONFIG_FILE
51 #endif
52
53 #if defined(MBEDTLS_SSL_TICKET_C)
54
55 #if defined(MBEDTLS_PLATFORM_C)
56 #include "mbedtls/platform.h"
57 #else
58 #include <stdlib.h>
59 #define mbedtls_calloc calloc
60 #define mbedtls_free free
61 #endif
62
63 #include "mbedtls/ssl_internal.h"
64 #include "mbedtls/ssl_ticket.h"
65 #include "mbedtls/platform_util.h"
66
67 #include <string.h>
68
69 /*
70 * Initialze context
71 */
mbedtls_ssl_ticket_init(mbedtls_ssl_ticket_context * ctx)72 void mbedtls_ssl_ticket_init( mbedtls_ssl_ticket_context *ctx )
73 {
74 memset( ctx, 0, sizeof( mbedtls_ssl_ticket_context ) );
75
76 #if defined(MBEDTLS_THREADING_C)
77 mbedtls_mutex_init( &ctx->mutex );
78 #endif
79 }
80
81 #define MAX_KEY_BYTES 32 /* 256 bits */
82
83 #define TICKET_KEY_NAME_BYTES 4
84 #define TICKET_IV_BYTES 12
85 #define TICKET_CRYPT_LEN_BYTES 2
86 #define TICKET_AUTH_TAG_BYTES 16
87
88 #define TICKET_MIN_LEN ( TICKET_KEY_NAME_BYTES + \
89 TICKET_IV_BYTES + \
90 TICKET_CRYPT_LEN_BYTES + \
91 TICKET_AUTH_TAG_BYTES )
92 #define TICKET_ADD_DATA_LEN ( TICKET_KEY_NAME_BYTES + \
93 TICKET_IV_BYTES + \
94 TICKET_CRYPT_LEN_BYTES )
95
96 /*
97 * Generate/update a key
98 */
ssl_ticket_gen_key(mbedtls_ssl_ticket_context * ctx,unsigned char index)99 static int ssl_ticket_gen_key( mbedtls_ssl_ticket_context *ctx,
100 unsigned char index )
101 {
102 int ret;
103 unsigned char buf[MAX_KEY_BYTES];
104 mbedtls_ssl_ticket_key *key = ctx->keys + index;
105
106 #if defined(MBEDTLS_HAVE_TIME)
107 key->generation_time = (uint32_t) mbedtls_time( NULL );
108 #endif
109
110 if( ( ret = ctx->f_rng( ctx->p_rng, key->name, sizeof( key->name ) ) ) != 0 )
111 return( ret );
112
113 if( ( ret = ctx->f_rng( ctx->p_rng, buf, sizeof( buf ) ) ) != 0 )
114 return( ret );
115
116 /* With GCM and CCM, same context can encrypt & decrypt */
117 ret = mbedtls_cipher_setkey( &key->ctx, buf,
118 mbedtls_cipher_get_key_bitlen( &key->ctx ),
119 MBEDTLS_ENCRYPT );
120
121 mbedtls_platform_zeroize( buf, sizeof( buf ) );
122
123 return( ret );
124 }
125
126 /*
127 * Rotate/generate keys if necessary
128 */
ssl_ticket_update_keys(mbedtls_ssl_ticket_context * ctx)129 static int ssl_ticket_update_keys( mbedtls_ssl_ticket_context *ctx )
130 {
131 #if !defined(MBEDTLS_HAVE_TIME)
132 ((void) ctx);
133 #else
134 if( ctx->ticket_lifetime != 0 )
135 {
136 uint32_t current_time = (uint32_t) mbedtls_time( NULL );
137 uint32_t key_time = ctx->keys[ctx->active].generation_time;
138
139 if( current_time >= key_time &&
140 current_time - key_time < ctx->ticket_lifetime )
141 {
142 return( 0 );
143 }
144
145 ctx->active = 1 - ctx->active;
146
147 return( ssl_ticket_gen_key( ctx, ctx->active ) );
148 }
149 else
150 #endif /* MBEDTLS_HAVE_TIME */
151 return( 0 );
152 }
153
154 /*
155 * Setup context for actual use
156 */
mbedtls_ssl_ticket_setup(mbedtls_ssl_ticket_context * ctx,int (* f_rng)(void *,unsigned char *,size_t),void * p_rng,mbedtls_cipher_type_t cipher,uint32_t lifetime)157 int mbedtls_ssl_ticket_setup( mbedtls_ssl_ticket_context *ctx,
158 int (*f_rng)(void *, unsigned char *, size_t), void *p_rng,
159 mbedtls_cipher_type_t cipher,
160 uint32_t lifetime )
161 {
162 int ret;
163 const mbedtls_cipher_info_t *cipher_info;
164
165 ctx->f_rng = f_rng;
166 ctx->p_rng = p_rng;
167
168 ctx->ticket_lifetime = lifetime;
169
170 cipher_info = mbedtls_cipher_info_from_type( cipher);
171 if( cipher_info == NULL )
172 return( MBEDTLS_ERR_SSL_BAD_INPUT_DATA );
173
174 if( cipher_info->mode != MBEDTLS_MODE_GCM &&
175 cipher_info->mode != MBEDTLS_MODE_CCM )
176 {
177 return( MBEDTLS_ERR_SSL_BAD_INPUT_DATA );
178 }
179
180 if( cipher_info->key_bitlen > 8 * MAX_KEY_BYTES )
181 return( MBEDTLS_ERR_SSL_BAD_INPUT_DATA );
182
183 if( ( ret = mbedtls_cipher_setup( &ctx->keys[0].ctx, cipher_info ) ) != 0 ||
184 ( ret = mbedtls_cipher_setup( &ctx->keys[1].ctx, cipher_info ) ) != 0 )
185 {
186 return( ret );
187 }
188
189 if( ( ret = ssl_ticket_gen_key( ctx, 0 ) ) != 0 ||
190 ( ret = ssl_ticket_gen_key( ctx, 1 ) ) != 0 )
191 {
192 return( ret );
193 }
194
195 return( 0 );
196 }
197
198 /*
199 * Serialize a session in the following format:
200 * 0 . n-1 session structure, n = sizeof(mbedtls_ssl_session)
201 * n . n+2 peer_cert length = m (0 if no certificate)
202 * n+3 . n+2+m peer cert ASN.1
203 */
ssl_save_session(const mbedtls_ssl_session * session,unsigned char * buf,size_t buf_len,size_t * olen)204 static int ssl_save_session( const mbedtls_ssl_session *session,
205 unsigned char *buf, size_t buf_len,
206 size_t *olen )
207 {
208 unsigned char *p = buf;
209 size_t left = buf_len;
210 #if defined(MBEDTLS_X509_CRT_PARSE_C)
211 size_t cert_len;
212 #endif /* MBEDTLS_X509_CRT_PARSE_C */
213
214 if( left < sizeof( mbedtls_ssl_session ) )
215 return( MBEDTLS_ERR_SSL_BUFFER_TOO_SMALL );
216
217 memcpy( p, session, sizeof( mbedtls_ssl_session ) );
218 p += sizeof( mbedtls_ssl_session );
219 left -= sizeof( mbedtls_ssl_session );
220
221 #if defined(MBEDTLS_X509_CRT_PARSE_C)
222 if( session->peer_cert == NULL )
223 cert_len = 0;
224 else
225 cert_len = session->peer_cert->raw.len;
226
227 if( left < 3 + cert_len )
228 return( MBEDTLS_ERR_SSL_BUFFER_TOO_SMALL );
229
230 *p++ = (unsigned char)( ( cert_len >> 16 ) & 0xFF );
231 *p++ = (unsigned char)( ( cert_len >> 8 ) & 0xFF );
232 *p++ = (unsigned char)( ( cert_len ) & 0xFF );
233
234 if( session->peer_cert != NULL )
235 memcpy( p, session->peer_cert->raw.p, cert_len );
236
237 p += cert_len;
238 #endif /* MBEDTLS_X509_CRT_PARSE_C */
239
240 *olen = p - buf;
241
242 return( 0 );
243 }
244
245 /*
246 * Unserialise session, see ssl_save_session()
247 */
ssl_load_session(mbedtls_ssl_session * session,const unsigned char * buf,size_t len)248 static int ssl_load_session( mbedtls_ssl_session *session,
249 const unsigned char *buf, size_t len )
250 {
251 const unsigned char *p = buf;
252 const unsigned char * const end = buf + len;
253 #if defined(MBEDTLS_X509_CRT_PARSE_C)
254 size_t cert_len;
255 #endif /* MBEDTLS_X509_CRT_PARSE_C */
256
257 if( sizeof( mbedtls_ssl_session ) > (size_t)( end - p ) )
258 return( MBEDTLS_ERR_SSL_BAD_INPUT_DATA );
259
260 memcpy( session, p, sizeof( mbedtls_ssl_session ) );
261 p += sizeof( mbedtls_ssl_session );
262
263 #if defined(MBEDTLS_X509_CRT_PARSE_C)
264 if( 3 > (size_t)( end - p ) )
265 return( MBEDTLS_ERR_SSL_BAD_INPUT_DATA );
266
267 cert_len = ( p[0] << 16 ) | ( p[1] << 8 ) | p[2];
268 p += 3;
269
270 if( cert_len == 0 )
271 {
272 session->peer_cert = NULL;
273 }
274 else
275 {
276 int ret;
277
278 if( cert_len > (size_t)( end - p ) )
279 return( MBEDTLS_ERR_SSL_BAD_INPUT_DATA );
280
281 session->peer_cert = mbedtls_calloc( 1, sizeof( mbedtls_x509_crt ) );
282
283 if( session->peer_cert == NULL )
284 return( MBEDTLS_ERR_SSL_ALLOC_FAILED );
285
286 mbedtls_x509_crt_init( session->peer_cert );
287
288 if( ( ret = mbedtls_x509_crt_parse_der( session->peer_cert,
289 p, cert_len ) ) != 0 )
290 {
291 mbedtls_x509_crt_free( session->peer_cert );
292 mbedtls_free( session->peer_cert );
293 session->peer_cert = NULL;
294 return( ret );
295 }
296
297 p += cert_len;
298 }
299 #endif /* MBEDTLS_X509_CRT_PARSE_C */
300
301 if( p != end )
302 return( MBEDTLS_ERR_SSL_BAD_INPUT_DATA );
303
304 return( 0 );
305 }
306
307 /*
308 * Create session ticket, with the following structure:
309 *
310 * struct {
311 * opaque key_name[4];
312 * opaque iv[12];
313 * opaque encrypted_state<0..2^16-1>;
314 * opaque tag[16];
315 * } ticket;
316 *
317 * The key_name, iv, and length of encrypted_state are the additional
318 * authenticated data.
319 */
320
mbedtls_ssl_ticket_write(void * p_ticket,const mbedtls_ssl_session * session,unsigned char * start,const unsigned char * end,size_t * tlen,uint32_t * ticket_lifetime)321 int mbedtls_ssl_ticket_write( void *p_ticket,
322 const mbedtls_ssl_session *session,
323 unsigned char *start,
324 const unsigned char *end,
325 size_t *tlen,
326 uint32_t *ticket_lifetime )
327 {
328 int ret;
329 mbedtls_ssl_ticket_context *ctx = p_ticket;
330 mbedtls_ssl_ticket_key *key;
331 unsigned char *key_name = start;
332 unsigned char *iv = start + TICKET_KEY_NAME_BYTES;
333 unsigned char *state_len_bytes = iv + TICKET_IV_BYTES;
334 unsigned char *state = state_len_bytes + TICKET_CRYPT_LEN_BYTES;
335 unsigned char *tag;
336 size_t clear_len, ciph_len;
337
338 *tlen = 0;
339
340 if( ctx == NULL || ctx->f_rng == NULL )
341 return( MBEDTLS_ERR_SSL_BAD_INPUT_DATA );
342
343 /* We need at least 4 bytes for key_name, 12 for IV, 2 for len 16 for tag,
344 * in addition to session itself, that will be checked when writing it. */
345 MBEDTLS_SSL_CHK_BUF_PTR( start, end, TICKET_MIN_LEN );
346
347 #if defined(MBEDTLS_THREADING_C)
348 if( ( ret = mbedtls_mutex_lock( &ctx->mutex ) ) != 0 )
349 return( ret );
350 #endif
351
352 if( ( ret = ssl_ticket_update_keys( ctx ) ) != 0 )
353 goto cleanup;
354
355 key = &ctx->keys[ctx->active];
356
357 *ticket_lifetime = ctx->ticket_lifetime;
358
359 memcpy( key_name, key->name, TICKET_KEY_NAME_BYTES );
360
361 if( ( ret = ctx->f_rng( ctx->p_rng, iv, TICKET_IV_BYTES ) ) != 0 )
362 goto cleanup;
363
364 /* Dump session state */
365 if( ( ret = ssl_save_session( session,
366 state, end - state, &clear_len ) ) != 0 ||
367 (unsigned long) clear_len > 65535 )
368 {
369 goto cleanup;
370 }
371 state_len_bytes[0] = ( clear_len >> 8 ) & 0xff;
372 state_len_bytes[1] = ( clear_len ) & 0xff;
373
374 /* Encrypt and authenticate */
375 tag = state + clear_len;
376 if( ( ret = mbedtls_cipher_auth_encrypt( &key->ctx,
377 iv, TICKET_IV_BYTES,
378 /* Additional data: key name, IV and length */
379 key_name, TICKET_ADD_DATA_LEN,
380 state, clear_len, state, &ciph_len,
381 tag, TICKET_AUTH_TAG_BYTES ) ) != 0 )
382 {
383 goto cleanup;
384 }
385 if( ciph_len != clear_len )
386 {
387 ret = MBEDTLS_ERR_SSL_INTERNAL_ERROR;
388 goto cleanup;
389 }
390
391 *tlen = TICKET_MIN_LEN + ciph_len;
392
393 cleanup:
394 #if defined(MBEDTLS_THREADING_C)
395 if( mbedtls_mutex_unlock( &ctx->mutex ) != 0 )
396 return( MBEDTLS_ERR_THREADING_MUTEX_ERROR );
397 #endif
398
399 return( ret );
400 }
401
402 /*
403 * Select key based on name
404 */
ssl_ticket_select_key(mbedtls_ssl_ticket_context * ctx,const unsigned char name[4])405 static mbedtls_ssl_ticket_key *ssl_ticket_select_key(
406 mbedtls_ssl_ticket_context *ctx,
407 const unsigned char name[4] )
408 {
409 unsigned char i;
410
411 for( i = 0; i < sizeof( ctx->keys ) / sizeof( *ctx->keys ); i++ )
412 if( memcmp( name, ctx->keys[i].name, 4 ) == 0 )
413 return( &ctx->keys[i] );
414
415 return( NULL );
416 }
417
418 /*
419 * Load session ticket (see mbedtls_ssl_ticket_write for structure)
420 */
mbedtls_ssl_ticket_parse(void * p_ticket,mbedtls_ssl_session * session,unsigned char * buf,size_t len)421 int mbedtls_ssl_ticket_parse( void *p_ticket,
422 mbedtls_ssl_session *session,
423 unsigned char *buf,
424 size_t len )
425 {
426 int ret;
427 mbedtls_ssl_ticket_context *ctx = p_ticket;
428 mbedtls_ssl_ticket_key *key;
429 unsigned char *key_name = buf;
430 unsigned char *iv = buf + TICKET_KEY_NAME_BYTES;
431 unsigned char *enc_len_p = iv + TICKET_IV_BYTES;
432 unsigned char *ticket = enc_len_p + TICKET_CRYPT_LEN_BYTES;
433 unsigned char *tag;
434 size_t enc_len, clear_len;
435
436 if( ctx == NULL || ctx->f_rng == NULL )
437 return( MBEDTLS_ERR_SSL_BAD_INPUT_DATA );
438
439 if( len < TICKET_MIN_LEN )
440 return( MBEDTLS_ERR_SSL_BAD_INPUT_DATA );
441
442 #if defined(MBEDTLS_THREADING_C)
443 if( ( ret = mbedtls_mutex_lock( &ctx->mutex ) ) != 0 )
444 return( ret );
445 #endif
446
447 if( ( ret = ssl_ticket_update_keys( ctx ) ) != 0 )
448 goto cleanup;
449
450 enc_len = ( enc_len_p[0] << 8 ) | enc_len_p[1];
451 tag = ticket + enc_len;
452
453 if( len != TICKET_MIN_LEN + enc_len )
454 {
455 ret = MBEDTLS_ERR_SSL_BAD_INPUT_DATA;
456 goto cleanup;
457 }
458
459 /* Select key */
460 if( ( key = ssl_ticket_select_key( ctx, key_name ) ) == NULL )
461 {
462 /* We can't know for sure but this is a likely option unless we're
463 * under attack - this is only informative anyway */
464 ret = MBEDTLS_ERR_SSL_SESSION_TICKET_EXPIRED;
465 goto cleanup;
466 }
467
468 /* Decrypt and authenticate */
469 if( ( ret = mbedtls_cipher_auth_decrypt( &key->ctx,
470 iv, TICKET_IV_BYTES,
471 /* Additional data: key name, IV and length */
472 key_name, TICKET_ADD_DATA_LEN,
473 ticket, enc_len,
474 ticket, &clear_len,
475 tag, TICKET_AUTH_TAG_BYTES ) ) != 0 )
476 {
477 if( ret == MBEDTLS_ERR_CIPHER_AUTH_FAILED )
478 ret = MBEDTLS_ERR_SSL_INVALID_MAC;
479
480 goto cleanup;
481 }
482 if( clear_len != enc_len )
483 {
484 ret = MBEDTLS_ERR_SSL_INTERNAL_ERROR;
485 goto cleanup;
486 }
487
488 /* Actually load session */
489 if( ( ret = ssl_load_session( session, ticket, clear_len ) ) != 0 )
490 goto cleanup;
491
492 #if defined(MBEDTLS_HAVE_TIME)
493 {
494 /* Check for expiration */
495 mbedtls_time_t current_time = mbedtls_time( NULL );
496
497 if( current_time < session->start ||
498 (uint32_t)( current_time - session->start ) > ctx->ticket_lifetime )
499 {
500 ret = MBEDTLS_ERR_SSL_SESSION_TICKET_EXPIRED;
501 goto cleanup;
502 }
503 }
504 #endif
505
506 cleanup:
507 #if defined(MBEDTLS_THREADING_C)
508 if( mbedtls_mutex_unlock( &ctx->mutex ) != 0 )
509 return( MBEDTLS_ERR_THREADING_MUTEX_ERROR );
510 #endif
511
512 return( ret );
513 }
514
515 /*
516 * Free context
517 */
mbedtls_ssl_ticket_free(mbedtls_ssl_ticket_context * ctx)518 void mbedtls_ssl_ticket_free( mbedtls_ssl_ticket_context *ctx )
519 {
520 mbedtls_cipher_free( &ctx->keys[0].ctx );
521 mbedtls_cipher_free( &ctx->keys[1].ctx );
522
523 #if defined(MBEDTLS_THREADING_C)
524 mbedtls_mutex_free( &ctx->mutex );
525 #endif
526
527 mbedtls_platform_zeroize( ctx, sizeof( mbedtls_ssl_ticket_context ) );
528 }
529
530 #endif /* MBEDTLS_SSL_TICKET_C */
531