1 /*
2 * TLS server tickets callbacks implementation
3 *
4 * Copyright (C) 2006-2015, ARM Limited, All Rights Reserved
5 * SPDX-License-Identifier: Apache-2.0
6 *
7 * Licensed under the Apache License, Version 2.0 (the "License"); you may
8 * not use this file except in compliance with the License.
9 * You may obtain a copy of the License at
10 *
11 * http://www.apache.org/licenses/LICENSE-2.0
12 *
13 * Unless required by applicable law or agreed to in writing, software
14 * distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
15 * WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
16 * See the License for the specific language governing permissions and
17 * limitations under the License.
18 *
19 * This file is part of mbed TLS (https://tls.mbed.org)
20 */
21
22 #if !defined(MBEDTLS_CONFIG_FILE)
23 #include "mbedtls/config.h"
24 #else
25 #include MBEDTLS_CONFIG_FILE
26 #endif
27
28 #if defined(MBEDTLS_SSL_TICKET_C)
29
30 #if defined(MBEDTLS_PLATFORM_C)
31 #include "mbedtls/platform.h"
32 #else
33 #include <stdlib.h>
34 #define mbedtls_calloc calloc
35 #define mbedtls_free free
36 #endif
37
38 #include "mbedtls/ssl_ticket.h"
39
40 #include <string.h>
41
42 /* Implementation that should never be optimized out by the compiler */
mbedtls_zeroize(void * v,size_t n)43 static void mbedtls_zeroize( void *v, size_t n ) {
44 volatile unsigned char *p = v; while( n-- ) *p++ = 0;
45 }
46
47 /*
48 * Initialze context
49 */
mbedtls_ssl_ticket_init(mbedtls_ssl_ticket_context * ctx)50 void mbedtls_ssl_ticket_init( mbedtls_ssl_ticket_context *ctx )
51 {
52 memset( ctx, 0, sizeof( mbedtls_ssl_ticket_context ) );
53
54 #if defined(MBEDTLS_THREADING_C)
55 mbedtls_mutex_init( &ctx->mutex );
56 #endif
57 }
58
59 #define MAX_KEY_BYTES 32 /* 256 bits */
60
61 /*
62 * Generate/update a key
63 */
ssl_ticket_gen_key(mbedtls_ssl_ticket_context * ctx,unsigned char index)64 static int ssl_ticket_gen_key( mbedtls_ssl_ticket_context *ctx,
65 unsigned char index )
66 {
67 int ret;
68 unsigned char buf[MAX_KEY_BYTES];
69 mbedtls_ssl_ticket_key *key = ctx->keys + index;
70
71 #if defined(MBEDTLS_HAVE_TIME)
72 key->generation_time = (uint32_t) mbedtls_time( NULL );
73 #endif
74
75 if( ( ret = ctx->f_rng( ctx->p_rng, key->name, sizeof( key->name ) ) ) != 0 )
76 return( ret );
77
78 if( ( ret = ctx->f_rng( ctx->p_rng, buf, sizeof( buf ) ) ) != 0 )
79 return( ret );
80
81 /* With GCM and CCM, same context can encrypt & decrypt */
82 ret = mbedtls_cipher_setkey( &key->ctx, buf,
83 mbedtls_cipher_get_key_bitlen( &key->ctx ),
84 MBEDTLS_ENCRYPT );
85
86 mbedtls_zeroize( buf, sizeof( buf ) );
87
88 return( ret );
89 }
90
91 /*
92 * Rotate/generate keys if necessary
93 */
ssl_ticket_update_keys(mbedtls_ssl_ticket_context * ctx)94 static int ssl_ticket_update_keys( mbedtls_ssl_ticket_context *ctx )
95 {
96 #if !defined(MBEDTLS_HAVE_TIME)
97 ((void) ctx);
98 #else
99 if( ctx->ticket_lifetime != 0 )
100 {
101 uint32_t current_time = (uint32_t) mbedtls_time( NULL );
102 uint32_t key_time = ctx->keys[ctx->active].generation_time;
103
104 if( current_time > key_time &&
105 current_time - key_time < ctx->ticket_lifetime )
106 {
107 return( 0 );
108 }
109
110 ctx->active = 1 - ctx->active;
111
112 return( ssl_ticket_gen_key( ctx, ctx->active ) );
113 }
114 else
115 #endif /* MBEDTLS_HAVE_TIME */
116 return( 0 );
117 }
118
119 /*
120 * Setup context for actual use
121 */
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)122 int mbedtls_ssl_ticket_setup( mbedtls_ssl_ticket_context *ctx,
123 int (*f_rng)(void *, unsigned char *, size_t), void *p_rng,
124 mbedtls_cipher_type_t cipher,
125 uint32_t lifetime )
126 {
127 int ret;
128 const mbedtls_cipher_info_t *cipher_info;
129
130 ctx->f_rng = f_rng;
131 ctx->p_rng = p_rng;
132
133 ctx->ticket_lifetime = lifetime;
134
135 cipher_info = mbedtls_cipher_info_from_type( cipher);
136 if( cipher_info == NULL )
137 return( MBEDTLS_ERR_SSL_BAD_INPUT_DATA );
138
139 if( cipher_info->mode != MBEDTLS_MODE_GCM &&
140 cipher_info->mode != MBEDTLS_MODE_CCM )
141 {
142 return( MBEDTLS_ERR_SSL_BAD_INPUT_DATA );
143 }
144
145 if( cipher_info->key_bitlen > 8 * MAX_KEY_BYTES )
146 return( MBEDTLS_ERR_SSL_BAD_INPUT_DATA );
147
148 if( ( ret = mbedtls_cipher_setup( &ctx->keys[0].ctx, cipher_info ) ) != 0 ||
149 ( ret = mbedtls_cipher_setup( &ctx->keys[1].ctx, cipher_info ) ) != 0 )
150 {
151 return( ret );
152 }
153
154 if( ( ret = ssl_ticket_gen_key( ctx, 0 ) ) != 0 ||
155 ( ret = ssl_ticket_gen_key( ctx, 1 ) ) != 0 )
156 {
157 return( ret );
158 }
159
160 return( 0 );
161 }
162
163 /*
164 * Serialize a session in the following format:
165 * 0 . n-1 session structure, n = sizeof(mbedtls_ssl_session)
166 * n . n+2 peer_cert length = m (0 if no certificate)
167 * n+3 . n+2+m peer cert ASN.1
168 */
ssl_save_session(const mbedtls_ssl_session * session,unsigned char * buf,size_t buf_len,size_t * olen)169 static int ssl_save_session( const mbedtls_ssl_session *session,
170 unsigned char *buf, size_t buf_len,
171 size_t *olen )
172 {
173 unsigned char *p = buf;
174 size_t left = buf_len;
175 #if defined(MBEDTLS_X509_CRT_PARSE_C)
176 size_t cert_len;
177 #endif /* MBEDTLS_X509_CRT_PARSE_C */
178
179 if( left < sizeof( mbedtls_ssl_session ) )
180 return( MBEDTLS_ERR_SSL_BUFFER_TOO_SMALL );
181
182 memcpy( p, session, sizeof( mbedtls_ssl_session ) );
183 p += sizeof( mbedtls_ssl_session );
184 left -= sizeof( mbedtls_ssl_session );
185
186 #if defined(MBEDTLS_X509_CRT_PARSE_C)
187 if( session->peer_cert == NULL )
188 cert_len = 0;
189 else
190 cert_len = session->peer_cert->raw.len;
191
192 if( left < 3 + cert_len )
193 return( MBEDTLS_ERR_SSL_BUFFER_TOO_SMALL );
194
195 *p++ = (unsigned char)( cert_len >> 16 & 0xFF );
196 *p++ = (unsigned char)( cert_len >> 8 & 0xFF );
197 *p++ = (unsigned char)( cert_len & 0xFF );
198
199 if( session->peer_cert != NULL )
200 memcpy( p, session->peer_cert->raw.p, cert_len );
201
202 p += cert_len;
203 #endif /* MBEDTLS_X509_CRT_PARSE_C */
204
205 *olen = p - buf;
206
207 return( 0 );
208 }
209
210 /*
211 * Unserialise session, see ssl_save_session()
212 */
ssl_load_session(mbedtls_ssl_session * session,const unsigned char * buf,size_t len)213 static int ssl_load_session( mbedtls_ssl_session *session,
214 const unsigned char *buf, size_t len )
215 {
216 const unsigned char *p = buf;
217 const unsigned char * const end = buf + len;
218 #if defined(MBEDTLS_X509_CRT_PARSE_C)
219 size_t cert_len;
220 #endif /* MBEDTLS_X509_CRT_PARSE_C */
221
222 if( p + sizeof( mbedtls_ssl_session ) > end )
223 return( MBEDTLS_ERR_SSL_BAD_INPUT_DATA );
224
225 memcpy( session, p, sizeof( mbedtls_ssl_session ) );
226 p += sizeof( mbedtls_ssl_session );
227
228 #if defined(MBEDTLS_X509_CRT_PARSE_C)
229 if( p + 3 > end )
230 return( MBEDTLS_ERR_SSL_BAD_INPUT_DATA );
231
232 cert_len = ( p[0] << 16 ) | ( p[1] << 8 ) | p[2];
233 p += 3;
234
235 if( cert_len == 0 )
236 {
237 session->peer_cert = NULL;
238 }
239 else
240 {
241 int ret;
242
243 if( p + cert_len > end )
244 return( MBEDTLS_ERR_SSL_BAD_INPUT_DATA );
245
246 session->peer_cert = mbedtls_calloc( 1, sizeof( mbedtls_x509_crt ) );
247
248 if( session->peer_cert == NULL )
249 return( MBEDTLS_ERR_SSL_ALLOC_FAILED );
250
251 mbedtls_x509_crt_init( session->peer_cert );
252
253 if( ( ret = mbedtls_x509_crt_parse_der( session->peer_cert,
254 p, cert_len ) ) != 0 )
255 {
256 mbedtls_x509_crt_free( session->peer_cert );
257 mbedtls_free( session->peer_cert );
258 session->peer_cert = NULL;
259 return( ret );
260 }
261
262 p += cert_len;
263 }
264 #endif /* MBEDTLS_X509_CRT_PARSE_C */
265
266 if( p != end )
267 return( MBEDTLS_ERR_SSL_BAD_INPUT_DATA );
268
269 return( 0 );
270 }
271
272 /*
273 * Create session ticket, with the following structure:
274 *
275 * struct {
276 * opaque key_name[4];
277 * opaque iv[12];
278 * opaque encrypted_state<0..2^16-1>;
279 * opaque tag[16];
280 * } ticket;
281 *
282 * The key_name, iv, and length of encrypted_state are the additional
283 * authenticated data.
284 */
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)285 int mbedtls_ssl_ticket_write( void *p_ticket,
286 const mbedtls_ssl_session *session,
287 unsigned char *start,
288 const unsigned char *end,
289 size_t *tlen,
290 uint32_t *ticket_lifetime )
291 {
292 int ret;
293 mbedtls_ssl_ticket_context *ctx = p_ticket;
294 mbedtls_ssl_ticket_key *key;
295 unsigned char *key_name = start;
296 unsigned char *iv = start + 4;
297 unsigned char *state_len_bytes = iv + 12;
298 unsigned char *state = state_len_bytes + 2;
299 unsigned char *tag;
300 size_t clear_len, ciph_len;
301
302 *tlen = 0;
303
304 if( ctx == NULL || ctx->f_rng == NULL )
305 return( MBEDTLS_ERR_SSL_BAD_INPUT_DATA );
306
307 /* We need at least 4 bytes for key_name, 12 for IV, 2 for len 16 for tag,
308 * in addition to session itself, that will be checked when writing it. */
309 if( end - start < 4 + 12 + 2 + 16 )
310 return( MBEDTLS_ERR_SSL_BUFFER_TOO_SMALL );
311
312 #if defined(MBEDTLS_THREADING_C)
313 if( ( ret = mbedtls_mutex_lock( &ctx->mutex ) ) != 0 )
314 return( ret );
315 #endif
316
317 if( ( ret = ssl_ticket_update_keys( ctx ) ) != 0 )
318 goto cleanup;
319
320 key = &ctx->keys[ctx->active];
321
322 *ticket_lifetime = ctx->ticket_lifetime;
323
324 memcpy( key_name, key->name, 4 );
325
326 if( ( ret = ctx->f_rng( ctx->p_rng, iv, 12 ) ) != 0 )
327 goto cleanup;
328
329 /* Dump session state */
330 if( ( ret = ssl_save_session( session,
331 state, end - state, &clear_len ) ) != 0 ||
332 (unsigned long) clear_len > 65535 )
333 {
334 goto cleanup;
335 }
336 state_len_bytes[0] = ( clear_len >> 8 ) & 0xff;
337 state_len_bytes[1] = ( clear_len ) & 0xff;
338
339 /* Encrypt and authenticate */
340 tag = state + clear_len;
341 if( ( ret = mbedtls_cipher_auth_encrypt( &key->ctx,
342 iv, 12, key_name, 4 + 12 + 2,
343 state, clear_len, state, &ciph_len, tag, 16 ) ) != 0 )
344 {
345 goto cleanup;
346 }
347 if( ciph_len != clear_len )
348 {
349 ret = MBEDTLS_ERR_SSL_INTERNAL_ERROR;
350 goto cleanup;
351 }
352
353 *tlen = 4 + 12 + 2 + 16 + ciph_len;
354
355 cleanup:
356 #if defined(MBEDTLS_THREADING_C)
357 if( mbedtls_mutex_unlock( &ctx->mutex ) != 0 )
358 return( MBEDTLS_ERR_THREADING_MUTEX_ERROR );
359 #endif
360
361 return( ret );
362 }
363
364 /*
365 * Select key based on name
366 */
ssl_ticket_select_key(mbedtls_ssl_ticket_context * ctx,const unsigned char name[4])367 static mbedtls_ssl_ticket_key *ssl_ticket_select_key(
368 mbedtls_ssl_ticket_context *ctx,
369 const unsigned char name[4] )
370 {
371 unsigned char i;
372
373 for( i = 0; i < sizeof( ctx->keys ) / sizeof( *ctx->keys ); i++ )
374 if( memcmp( name, ctx->keys[i].name, 4 ) == 0 )
375 return( &ctx->keys[i] );
376
377 return( NULL );
378 }
379
380 /*
381 * Load session ticket (see mbedtls_ssl_ticket_write for structure)
382 */
mbedtls_ssl_ticket_parse(void * p_ticket,mbedtls_ssl_session * session,unsigned char * buf,size_t len)383 int mbedtls_ssl_ticket_parse( void *p_ticket,
384 mbedtls_ssl_session *session,
385 unsigned char *buf,
386 size_t len )
387 {
388 int ret;
389 mbedtls_ssl_ticket_context *ctx = p_ticket;
390 mbedtls_ssl_ticket_key *key;
391 unsigned char *key_name = buf;
392 unsigned char *iv = buf + 4;
393 unsigned char *enc_len_p = iv + 12;
394 unsigned char *ticket = enc_len_p + 2;
395 unsigned char *tag;
396 size_t enc_len, clear_len;
397
398 if( ctx == NULL || ctx->f_rng == NULL )
399 return( MBEDTLS_ERR_SSL_BAD_INPUT_DATA );
400
401 /* See mbedtls_ssl_ticket_write() */
402 if( len < 4 + 12 + 2 + 16 )
403 return( MBEDTLS_ERR_SSL_BAD_INPUT_DATA );
404
405 #if defined(MBEDTLS_THREADING_C)
406 if( ( ret = mbedtls_mutex_lock( &ctx->mutex ) ) != 0 )
407 return( ret );
408 #endif
409
410 if( ( ret = ssl_ticket_update_keys( ctx ) ) != 0 )
411 goto cleanup;
412
413 enc_len = ( enc_len_p[0] << 8 ) | enc_len_p[1];
414 tag = ticket + enc_len;
415
416 if( len != 4 + 12 + 2 + enc_len + 16 )
417 {
418 ret = MBEDTLS_ERR_SSL_BAD_INPUT_DATA;
419 goto cleanup;
420 }
421
422 /* Select key */
423 if( ( key = ssl_ticket_select_key( ctx, key_name ) ) == NULL )
424 {
425 /* We can't know for sure but this is a likely option unless we're
426 * under attack - this is only informative anyway */
427 ret = MBEDTLS_ERR_SSL_SESSION_TICKET_EXPIRED;
428 goto cleanup;
429 }
430
431 /* Decrypt and authenticate */
432 if( ( ret = mbedtls_cipher_auth_decrypt( &key->ctx, iv, 12,
433 key_name, 4 + 12 + 2, ticket, enc_len,
434 ticket, &clear_len, tag, 16 ) ) != 0 )
435 {
436 if( ret == MBEDTLS_ERR_CIPHER_AUTH_FAILED )
437 ret = MBEDTLS_ERR_SSL_INVALID_MAC;
438
439 goto cleanup;
440 }
441 if( clear_len != enc_len )
442 {
443 ret = MBEDTLS_ERR_SSL_INTERNAL_ERROR;
444 goto cleanup;
445 }
446
447 /* Actually load session */
448 if( ( ret = ssl_load_session( session, ticket, clear_len ) ) != 0 )
449 goto cleanup;
450
451 #if defined(MBEDTLS_HAVE_TIME)
452 {
453 /* Check for expiration */
454 mbedtls_time_t current_time = mbedtls_time( NULL );
455
456 if( current_time < session->start ||
457 (uint32_t)( current_time - session->start ) > ctx->ticket_lifetime )
458 {
459 ret = MBEDTLS_ERR_SSL_SESSION_TICKET_EXPIRED;
460 goto cleanup;
461 }
462 }
463 #endif
464
465 cleanup:
466 #if defined(MBEDTLS_THREADING_C)
467 if( mbedtls_mutex_unlock( &ctx->mutex ) != 0 )
468 return( MBEDTLS_ERR_THREADING_MUTEX_ERROR );
469 #endif
470
471 return( ret );
472 }
473
474 /*
475 * Free context
476 */
mbedtls_ssl_ticket_free(mbedtls_ssl_ticket_context * ctx)477 void mbedtls_ssl_ticket_free( mbedtls_ssl_ticket_context *ctx )
478 {
479 mbedtls_cipher_free( &ctx->keys[0].ctx );
480 mbedtls_cipher_free( &ctx->keys[1].ctx );
481
482 #if defined(MBEDTLS_THREADING_C)
483 mbedtls_mutex_free( &ctx->mutex );
484 #endif
485
486 mbedtls_zeroize( ctx, sizeof( mbedtls_ssl_ticket_context ) );
487 }
488
489 #endif /* MBEDTLS_SSL_TICKET_C */
490
