Asterisk - The Open Source Telephony Project  21.4.1
res_srtp.c
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1 /*
2  * Asterisk -- An open source telephony toolkit.
3  *
4  * Copyright (C) 2005, Mikael Magnusson
5  *
6  * Mikael Magnusson <mikma@users.sourceforge.net>
7  *
8  * See http://www.asterisk.org for more information about
9  * the Asterisk project. Please do not directly contact
10  * any of the maintainers of this project for assistance;
11  * the project provides a web site, mailing lists and IRC
12  * channels for your use.
13  *
14  * This program is free software, distributed under the terms of
15  * the GNU General Public License Version 2. See the LICENSE file
16  * at the top of the source tree.
17  *
18  * Builds on libSRTP http://srtp.sourceforge.net
19  */
20 
21 /*!
22  * \file
23  *
24  * \brief Secure RTP (SRTP)
25  *
26  * Secure RTP (SRTP)
27  * Specified in RFC 3711.
28  *
29  * \author Mikael Magnusson <mikma@users.sourceforge.net>
30  */
31 
32 /*** MODULEINFO
33  <depend>srtp</depend>
34  <use type="external">openssl</use>
35  <support_level>core</support_level>
36 ***/
37 
38 /* See https://docs.asterisk.org/Deployment/Secure-Calling/ */
39 
40 #include "asterisk.h" /* for NULL, size_t, memcpy, etc */
41 
42 #include <math.h> /* for pow */
43 
44 #if HAVE_SRTP_VERSION > 1
45 # include <srtp2/srtp.h>
46 # include "srtp/srtp_compat.h"
47 # include <openssl/rand.h>
48 #else
49 # include <srtp/srtp.h>
50 # ifdef HAVE_OPENSSL
51 # include <openssl/rand.h>
52 # else
53 # include <srtp/crypto_kernel.h>
54 # endif
55 #endif
56 
57 #include "asterisk/astobj2.h" /* for ao2_t_ref, etc */
58 #include "asterisk/frame.h" /* for AST_FRIENDLY_OFFSET */
59 #include "asterisk/logger.h" /* for ast_log, ast_debug, etc */
60 #include "asterisk/module.h" /* for ast_module_info, etc */
61 #include "asterisk/sdp_srtp.h"
62 #include "asterisk/res_srtp.h" /* for ast_srtp_cb, ast_srtp_suite, etc */
63 #include "asterisk/rtp_engine.h" /* for ast_rtp_engine_register_srtp, etc */
64 #include "asterisk/utils.h" /* for ast_free, ast_calloc */
65 
66 struct ast_srtp {
67  struct ast_rtp_instance *rtp;
68  struct ao2_container *policies;
69  srtp_t session;
70  const struct ast_srtp_cb *cb;
71  void *data;
72  int warned;
73  unsigned char buf[8192 + AST_FRIENDLY_OFFSET];
74  unsigned char rtcpbuf[8192 + AST_FRIENDLY_OFFSET];
75 };
76 
78  srtp_policy_t sp;
79 };
80 
81 /*! Tracks whether or not we've initialized the libsrtp library */
82 static int g_initialized = 0;
83 
84 /* SRTP functions */
85 static int ast_srtp_create(struct ast_srtp **srtp, struct ast_rtp_instance *rtp, struct ast_srtp_policy *policy);
86 static int ast_srtp_replace(struct ast_srtp **srtp, struct ast_rtp_instance *rtp, struct ast_srtp_policy *policy);
87 static void ast_srtp_destroy(struct ast_srtp *srtp);
88 static int ast_srtp_add_stream(struct ast_srtp *srtp, struct ast_srtp_policy *policy);
89 static int ast_srtp_change_source(struct ast_srtp *srtp, unsigned int from_ssrc, unsigned int to_ssrc);
90 
91 static int ast_srtp_unprotect(struct ast_srtp *srtp, void *buf, int *len, int rtcp);
92 static int ast_srtp_protect(struct ast_srtp *srtp, void **buf, int *len, int rtcp);
93 static void ast_srtp_set_cb(struct ast_srtp *srtp, const struct ast_srtp_cb *cb, void *data);
94 static int ast_srtp_get_random(unsigned char *key, size_t len);
95 
96 /* Policy functions */
97 static struct ast_srtp_policy *ast_srtp_policy_alloc(void);
98 static void ast_srtp_policy_destroy(struct ast_srtp_policy *policy);
99 static int ast_srtp_policy_set_suite(struct ast_srtp_policy *policy, enum ast_srtp_suite suite);
100 static int ast_srtp_policy_set_master_key(struct ast_srtp_policy *policy, const unsigned char *key, size_t key_len, const unsigned char *salt, size_t salt_len);
101 static void ast_srtp_policy_set_ssrc(struct ast_srtp_policy *policy, unsigned long ssrc, int inbound);
102 
103 static struct ast_srtp_res srtp_res = {
104  .create = ast_srtp_create,
105  .replace = ast_srtp_replace,
106  .destroy = ast_srtp_destroy,
107  .add_stream = ast_srtp_add_stream,
108  .change_source = ast_srtp_change_source,
109  .set_cb = ast_srtp_set_cb,
110  .unprotect = ast_srtp_unprotect,
111  .protect = ast_srtp_protect,
112  .get_random = ast_srtp_get_random
113 };
114 
115 static struct ast_srtp_policy_res policy_res = {
116  .alloc = ast_srtp_policy_alloc,
117  .destroy = ast_srtp_policy_destroy,
118  .set_suite = ast_srtp_policy_set_suite,
119  .set_master_key = ast_srtp_policy_set_master_key,
120  .set_ssrc = ast_srtp_policy_set_ssrc
121 };
122 
123 static const char *srtp_errstr(int err)
124 {
125  switch(err) {
126  case err_status_ok:
127  return "nothing to report";
128  case err_status_fail:
129  return "unspecified failure";
130  case err_status_bad_param:
131  return "unsupported parameter";
132  case err_status_alloc_fail:
133  return "couldn't allocate memory";
134  case err_status_dealloc_fail:
135  return "couldn't deallocate properly";
136  case err_status_init_fail:
137  return "couldn't initialize";
138  case err_status_terminus:
139  return "can't process as much data as requested";
140  case err_status_auth_fail:
141  return "authentication failure";
142  case err_status_cipher_fail:
143  return "cipher failure";
144  case err_status_replay_fail:
145  return "replay check failed (bad index)";
146  case err_status_replay_old:
147  return "replay check failed (index too old)";
148  case err_status_algo_fail:
149  return "algorithm failed test routine";
150  case err_status_no_such_op:
151  return "unsupported operation";
152  case err_status_no_ctx:
153  return "no appropriate context found";
154  case err_status_cant_check:
155  return "unable to perform desired validation";
156  case err_status_key_expired:
157  return "can't use key any more";
158  default:
159  return "unknown";
160  }
161 }
162 
163 static int policy_hash_fn(const void *obj, const int flags)
164 {
165  const struct ast_srtp_policy *policy = obj;
166 
167  return policy->sp.ssrc.type == ssrc_specific ? policy->sp.ssrc.value : policy->sp.ssrc.type;
168 }
169 
170 static int policy_cmp_fn(void *obj, void *arg, int flags)
171 {
172  const struct ast_srtp_policy *one = obj, *two = arg;
173 
174  return one->sp.ssrc.type == two->sp.ssrc.type && one->sp.ssrc.value == two->sp.ssrc.value;
175 }
176 
177 static struct ast_srtp_policy *find_policy(struct ast_srtp *srtp, const srtp_policy_t *policy, int flags)
178 {
179  struct ast_srtp_policy tmp = {
180  .sp = {
181  .ssrc.type = policy->ssrc.type,
182  .ssrc.value = policy->ssrc.value,
183  },
184  };
185 
186  return ao2_t_find(srtp->policies, &tmp, flags, "Looking for policy");
187 }
188 
189 static struct ast_srtp *res_srtp_new(void)
190 {
191  struct ast_srtp *srtp;
192 
193  if (!(srtp = ast_calloc(1, sizeof(*srtp)))) {
194  ast_log(LOG_ERROR, "Unable to allocate memory for srtp\n");
195  return NULL;
196  }
197 
198  srtp->policies = ao2_t_container_alloc_hash(AO2_ALLOC_OPT_LOCK_MUTEX, 0, 5,
199  policy_hash_fn, NULL, policy_cmp_fn, "SRTP policy container");
200  if (!srtp->policies) {
201  ast_free(srtp);
202  return NULL;
203  }
204 
205  srtp->warned = 1;
206 
207  return srtp;
208 }
209 
210 /*
211  struct ast_srtp_policy
212 */
213 static void srtp_event_cb(srtp_event_data_t *data)
214 {
215  switch (data->event) {
216  case event_ssrc_collision:
217  ast_debug(1, "SSRC collision\n");
218  break;
219  case event_key_soft_limit:
220  ast_debug(1, "event_key_soft_limit\n");
221  break;
222  case event_key_hard_limit:
223  ast_debug(1, "event_key_hard_limit\n");
224  break;
225  case event_packet_index_limit:
226  ast_debug(1, "event_packet_index_limit\n");
227  break;
228  }
229 }
230 
231 static void ast_srtp_policy_set_ssrc(struct ast_srtp_policy *policy,
232  unsigned long ssrc, int inbound)
233 {
234  if (ssrc) {
235  policy->sp.ssrc.type = ssrc_specific;
236  policy->sp.ssrc.value = ssrc;
237  } else {
238  policy->sp.ssrc.type = inbound ? ssrc_any_inbound : ssrc_any_outbound;
239  }
240 }
241 
242 static void policy_destructor(void *obj)
243 {
244  struct ast_srtp_policy *policy = obj;
245 
246  if (policy->sp.key) {
247  ast_free(policy->sp.key);
248  policy->sp.key = NULL;
249  }
250 }
251 
252 static struct ast_srtp_policy *ast_srtp_policy_alloc()
253 {
254  struct ast_srtp_policy *tmp;
255 
256  if (!(tmp = ao2_t_alloc(sizeof(*tmp), policy_destructor, "Allocating policy"))) {
257  ast_log(LOG_ERROR, "Unable to allocate memory for srtp_policy\n");
258  }
259 
260  return tmp;
261 }
262 
263 static void ast_srtp_policy_destroy(struct ast_srtp_policy *policy)
264 {
265  ao2_t_ref(policy, -1, "Destroying policy");
266 }
267 
268 static int policy_set_suite(crypto_policy_t *p, enum ast_srtp_suite suite)
269 {
270  switch (suite) {
271  case AST_AES_CM_128_HMAC_SHA1_80:
272  crypto_policy_set_aes_cm_128_hmac_sha1_80(p);
273  return 0;
274 
275  case AST_AES_CM_128_HMAC_SHA1_32:
276  crypto_policy_set_aes_cm_128_hmac_sha1_32(p);
277  return 0;
278 
279 #if defined(HAVE_SRTP_192) && defined(ENABLE_SRTP_AES_192)
280  case AST_AES_CM_192_HMAC_SHA1_80:
281  crypto_policy_set_aes_cm_192_hmac_sha1_80(p);
282  return 0;
283 
284  case AST_AES_CM_192_HMAC_SHA1_32:
285  crypto_policy_set_aes_cm_192_hmac_sha1_32(p);
286  return 0;
287 #endif
288 #if defined(HAVE_SRTP_256) && defined(ENABLE_SRTP_AES_256)
289  case AST_AES_CM_256_HMAC_SHA1_80:
290  crypto_policy_set_aes_cm_256_hmac_sha1_80(p);
291  return 0;
292 
293  case AST_AES_CM_256_HMAC_SHA1_32:
294  crypto_policy_set_aes_cm_256_hmac_sha1_32(p);
295  return 0;
296 #endif
297 #if defined(HAVE_SRTP_GCM) && defined(ENABLE_SRTP_AES_GCM)
298  case AST_AES_GCM_128:
299  crypto_policy_set_aes_gcm_128_16_auth(p);
300  return 0;
301 
302  case AST_AES_GCM_128_8:
303  crypto_policy_set_aes_gcm_128_8_auth(p);
304  return 0;
305 #endif
306 #if defined(HAVE_SRTP_GCM) && defined(ENABLE_SRTP_AES_GCM) && defined(ENABLE_SRTP_AES_256)
307  case AST_AES_GCM_256:
308  crypto_policy_set_aes_gcm_256_16_auth(p);
309  return 0;
310 
311  case AST_AES_GCM_256_8:
312  crypto_policy_set_aes_gcm_256_8_auth(p);
313  return 0;
314 #endif
315 
316  default:
317  ast_log(LOG_ERROR, "Invalid crypto suite: %u\n", suite);
318  return -1;
319  }
320 }
321 
322 static int ast_srtp_policy_set_suite(struct ast_srtp_policy *policy, enum ast_srtp_suite suite)
323 {
324  return policy_set_suite(&policy->sp.rtp, suite) | policy_set_suite(&policy->sp.rtcp, suite);
325 }
326 
327 static int ast_srtp_policy_set_master_key(struct ast_srtp_policy *policy, const unsigned char *key, size_t key_len, const unsigned char *salt, size_t salt_len)
328 {
329  size_t size = key_len + salt_len;
330  unsigned char *master_key;
331 
332  if (policy->sp.key) {
333  ast_free(policy->sp.key);
334  policy->sp.key = NULL;
335  }
336 
337  if (!(master_key = ast_calloc(1, size))) {
338  return -1;
339  }
340 
341  memcpy(master_key, key, key_len);
342  memcpy(master_key + key_len, salt, salt_len);
343 
344  policy->sp.key = master_key;
345 
346  return 0;
347 }
348 
349 static int ast_srtp_get_random(unsigned char *key, size_t len)
350 {
351 #ifdef HAVE_OPENSSL
352  return RAND_bytes(key, len) > 0 ? 0: -1;
353 #else
354  return crypto_get_random(key, len) != err_status_ok ? -1: 0;
355 #endif
356 }
357 
358 static void ast_srtp_set_cb(struct ast_srtp *srtp, const struct ast_srtp_cb *cb, void *data)
359 {
360  if (!srtp) {
361  return;
362  }
363 
364  srtp->cb = cb;
365  srtp->data = data;
366 }
367 
368 /* Vtable functions */
369 static int ast_srtp_unprotect(struct ast_srtp *srtp, void *buf, int *len, int flags)
370 {
371  int res = 0;
372  int i;
373  int rtcp = (flags & 0x01) >> 0;
374  int retry = (flags & 0x02) >> 1;
375  struct ast_rtp_instance_stats stats = {0,};
376 
377 tryagain:
378 
379  if (!srtp->session) {
380  ast_log(LOG_ERROR, "SRTP unprotect %s - missing session\n", rtcp ? "rtcp" : "rtp");
381  errno = EINVAL;
382  return -1;
383  }
384 
385  for (i = 0; i < 2; i++) {
386  res = rtcp ? srtp_unprotect_rtcp(srtp->session, buf, len) : srtp_unprotect(srtp->session, buf, len);
387  if (res != err_status_no_ctx) {
388  break;
389  }
390 
391  if (srtp->cb && srtp->cb->no_ctx) {
393  break;
394  }
395  if (srtp->cb->no_ctx(srtp->rtp, stats.remote_ssrc, srtp->data) < 0) {
396  break;
397  }
398  } else {
399  break;
400  }
401  }
402 
403  if (retry == 0 && res == err_status_replay_old) {
404  ast_log(AST_LOG_NOTICE, "SRTP unprotect failed with %s, retrying\n", srtp_errstr(res));
405 
406  if (srtp->session) {
407  struct ast_srtp_policy *policy;
408  struct ao2_iterator it;
409  int policies_count;
410 
411  /* dealloc first */
412  ast_debug(5, "SRTP destroy before re-create\n");
413  srtp_dealloc(srtp->session);
414 
415  /* get the count */
416  policies_count = ao2_container_count(srtp->policies);
417 
418  /* get the first to build up */
419  it = ao2_iterator_init(srtp->policies, 0);
420  policy = ao2_iterator_next(&it);
421 
422  ast_debug(5, "SRTP try to re-create\n");
423  if (policy) {
424  int res_srtp_create = srtp_create(&srtp->session, &policy->sp);
425  if (res_srtp_create == err_status_ok) {
426  ast_debug(5, "SRTP re-created with first policy\n");
427  ao2_t_ref(policy, -1, "Unreffing first policy for re-creating srtp session");
428 
429  /* if we have more than one policy, add them */
430  if (policies_count > 1) {
431  ast_debug(5, "Add all the other %d policies\n",
432  policies_count - 1);
433  while ((policy = ao2_iterator_next(&it))) {
434  srtp_add_stream(srtp->session, &policy->sp);
435  ao2_t_ref(policy, -1, "Unreffing n-th policy for re-creating srtp session");
436  }
437  }
438 
439  retry++;
441  goto tryagain;
442  }
443  ast_log(LOG_ERROR, "SRTP session could not be re-created after unprotect failure: %s\n", srtp_errstr(res_srtp_create));
444 
445  /* If srtp_create() fails with a previously alloced session, it will have been dealloced before returning. */
446  srtp->session = NULL;
447 
448  ao2_t_ref(policy, -1, "Unreffing first policy after srtp_create failed");
449  }
451  }
452  }
453 
454  if (!srtp->session) {
455  errno = EINVAL;
456  return -1;
457  }
458 
459  if (res != err_status_ok && res != err_status_replay_fail ) {
460  /*
461  * Authentication failures happen when an active attacker tries to
462  * insert malicious RTP packets. Furthermore, authentication failures
463  * happen, when the other party encrypts the sRTP data in an unexpected
464  * way. This happens quite often with RTCP. Therefore, when you see
465  * authentication failures, try to identify the implementation
466  * (author and product name) used by your other party. Try to investigate
467  * whether they use a custom library or an outdated version of libSRTP.
468  */
469  if (rtcp) {
470  ast_verb(2, "SRTCP unprotect failed on SSRC %u because of %s\n",
471  ast_rtp_instance_get_ssrc(srtp->rtp), srtp_errstr(res));
472  } else {
473  if ((srtp->warned >= 10) && !((srtp->warned - 10) % 150)) {
474  ast_verb(2, "SRTP unprotect failed on SSRC %u because of %s %d\n",
475  ast_rtp_instance_get_ssrc(srtp->rtp), srtp_errstr(res), srtp->warned);
476  srtp->warned = 11;
477  } else {
478  srtp->warned++;
479  }
480  }
481  errno = EAGAIN;
482  return -1;
483  }
484 
485  return *len;
486 }
487 
488 static int ast_srtp_protect(struct ast_srtp *srtp, void **buf, int *len, int rtcp)
489 {
490  int res;
491  unsigned char *localbuf;
492 
493  if (!srtp->session) {
494  ast_log(LOG_ERROR, "SRTP protect %s - missing session\n", rtcp ? "rtcp" : "rtp");
495  errno = EINVAL;
496  return -1;
497  }
498 
499  if ((*len + SRTP_MAX_TRAILER_LEN) > sizeof(srtp->buf)) {
500  return -1;
501  }
502 
503  localbuf = rtcp ? srtp->rtcpbuf : srtp->buf;
504 
505  memcpy(localbuf, *buf, *len);
506 
507  if ((res = rtcp ? srtp_protect_rtcp(srtp->session, localbuf, len) : srtp_protect(srtp->session, localbuf, len)) != err_status_ok && res != err_status_replay_fail) {
508  ast_log(LOG_WARNING, "SRTP protect: %s\n", srtp_errstr(res));
509  return -1;
510  }
511 
512  *buf = localbuf;
513  return *len;
514 }
515 
516 static int ast_srtp_create(struct ast_srtp **srtp, struct ast_rtp_instance *rtp, struct ast_srtp_policy *policy)
517 {
518  struct ast_srtp *temp;
519  int status;
520 
521  if (!(temp = res_srtp_new())) {
522  return -1;
523  }
525 
526  /* Any failures after this point can use ast_srtp_destroy to destroy the instance */
527  status = srtp_create(&temp->session, &policy->sp);
528  if (status != err_status_ok) {
529  /* Session either wasn't created or was created and dealloced. */
530  temp->session = NULL;
531  ast_srtp_destroy(temp);
532  ast_log(LOG_ERROR, "Failed to create srtp session on rtp instance (%p) - %s\n",
533  rtp, srtp_errstr(status));
534  return -1;
535  }
536 
537  temp->rtp = rtp;
538  *srtp = temp;
539 
540  ao2_t_link((*srtp)->policies, policy, "Created initial policy");
541 
542  return 0;
543 }
544 
545 static int ast_srtp_replace(struct ast_srtp **srtp, struct ast_rtp_instance *rtp, struct ast_srtp_policy *policy)
546 {
547  struct ast_srtp *old = *srtp;
548  int res = ast_srtp_create(srtp, rtp, policy);
549 
550  if (!res && old) {
551  ast_srtp_destroy(old);
552  }
553 
554  if (res) {
555  ast_log(LOG_ERROR, "Failed to replace srtp (%p) on rtp instance (%p) "
556  "- keeping old\n", *srtp, rtp);
557  }
558 
559  return res;
560 }
561 
562 static void ast_srtp_destroy(struct ast_srtp *srtp)
563 {
564  if (srtp->session) {
565  srtp_dealloc(srtp->session);
566  }
567 
568  ao2_t_callback(srtp->policies, OBJ_UNLINK | OBJ_NODATA | OBJ_MULTIPLE, NULL, NULL, "Unallocate policy");
569  ao2_t_ref(srtp->policies, -1, "Destroying container");
570 
571  ast_free(srtp);
573 }
574 
575 static int ast_srtp_add_stream(struct ast_srtp *srtp, struct ast_srtp_policy *policy)
576 {
577  struct ast_srtp_policy *match;
578 
579  /* For existing streams, replace if its an SSRC stream, or bail if its a wildcard */
580  if ((match = find_policy(srtp, &policy->sp, OBJ_POINTER))) {
581  if (policy->sp.ssrc.type != ssrc_specific) {
582  ast_log(AST_LOG_WARNING, "Cannot replace an existing wildcard policy\n");
583  ao2_t_ref(match, -1, "Unreffing already existing policy");
584  return -1;
585  } else {
586  if (srtp_remove_stream(srtp->session, match->sp.ssrc.value) != err_status_ok) {
587  ast_log(AST_LOG_WARNING, "Failed to remove SRTP stream for SSRC %u\n", match->sp.ssrc.value);
588  }
589  ao2_t_unlink(srtp->policies, match, "Remove existing match policy");
590  ao2_t_ref(match, -1, "Unreffing already existing policy");
591  }
592  }
593 
594  ast_debug(3, "Adding new policy for %s %u\n",
595  policy->sp.ssrc.type == ssrc_specific ? "SSRC" : "type",
596  policy->sp.ssrc.type == ssrc_specific ? policy->sp.ssrc.value : policy->sp.ssrc.type);
597  if (srtp_add_stream(srtp->session, &policy->sp) != err_status_ok) {
598  ast_log(AST_LOG_WARNING, "Failed to add SRTP stream for %s %u\n",
599  policy->sp.ssrc.type == ssrc_specific ? "SSRC" : "type",
600  policy->sp.ssrc.type == ssrc_specific ? policy->sp.ssrc.value : policy->sp.ssrc.type);
601  return -1;
602  }
603 
604  ao2_t_link(srtp->policies, policy, "Added additional stream");
605 
606  return 0;
607 }
608 
609 static int ast_srtp_change_source(struct ast_srtp *srtp, unsigned int from_ssrc, unsigned int to_ssrc)
610 {
611  struct ast_srtp_policy *match;
612  struct srtp_policy_t sp = {
613  .ssrc.type = ssrc_specific,
614  .ssrc.value = from_ssrc,
615  };
616  err_status_t status;
617 
618  /* If we find a match, return and unlink it from the container so we
619  * can change the SSRC (which is part of the hash) and then have
620  * ast_srtp_add_stream link it back in if all is well */
621  if ((match = find_policy(srtp, &sp, OBJ_POINTER | OBJ_UNLINK))) {
622  match->sp.ssrc.value = to_ssrc;
623  if (ast_srtp_add_stream(srtp, match)) {
624  ast_log(LOG_WARNING, "Couldn't add stream\n");
625  } else if ((status = srtp_remove_stream(srtp->session, from_ssrc))) {
626  ast_debug(3, "Couldn't remove stream (%u)\n", status);
627  }
628  ao2_t_ref(match, -1, "Unreffing found policy in change_source");
629  }
630 
631  return 0;
632 }
633 
635  char *a_crypto;
636  unsigned char local_key[SRTP_MAX_KEY_LEN];
637  int tag;
638  char local_key64[((SRTP_MAX_KEY_LEN) * 8 + 5) / 6 + 1];
639  unsigned char remote_key[SRTP_MAX_KEY_LEN];
640  int key_len;
641 };
642 
643 static void res_sdp_crypto_dtor(struct ast_sdp_crypto *crypto)
644 {
645  if (crypto) {
646  ast_free(crypto->a_crypto);
647  crypto->a_crypto = NULL;
648  ast_free(crypto);
649 
651  }
652 }
653 
654 static struct ast_sdp_crypto *crypto_init_keys(struct ast_sdp_crypto *p, const int key_len)
655 {
656  unsigned char remote_key[key_len];
657 
658  if (srtp_res.get_random(p->local_key, key_len) < 0) {
659  return NULL;
660  }
661 
662  ast_base64encode(p->local_key64, p->local_key, key_len, sizeof(p->local_key64));
663 
664  p->key_len = ast_base64decode(remote_key, p->local_key64, sizeof(remote_key));
665 
666  if (p->key_len != key_len) {
667  ast_log(LOG_ERROR, "base64 encode/decode bad len %d != %d\n", p->key_len, key_len);
668  return NULL;
669  }
670 
671  if (memcmp(remote_key, p->local_key, p->key_len)) {
672  ast_log(LOG_ERROR, "base64 encode/decode bad key\n");
673  return NULL;
674  }
675 
676  ast_debug(1 , "local_key64 %s len %zu\n", p->local_key64, strlen(p->local_key64));
677 
678  return p;
679 }
680 
681 static struct ast_sdp_crypto *sdp_crypto_alloc(const int key_len)
682 {
683  struct ast_sdp_crypto *p, *result;
684 
685  if (!(p = ast_calloc(1, sizeof(*p)))) {
686  return NULL;
687  }
688  p->tag = 1;
690 
691  /* default is a key which uses AST_AES_CM_128_HMAC_SHA1_xx */
692  result = crypto_init_keys(p, key_len);
693  if (!result) {
694  res_sdp_crypto_dtor(p);
695  }
696 
697  return result;
698 }
699 
700 static struct ast_sdp_crypto *res_sdp_crypto_alloc(void)
701 {
702  return sdp_crypto_alloc(SRTP_MASTER_KEY_LEN);
703 }
704 
705 static int res_sdp_crypto_build_offer(struct ast_sdp_crypto *p, int taglen)
706 {
707  int res;
708 
709  /* Rebuild the crypto line */
710  ast_free(p->a_crypto);
711  p->a_crypto = NULL;
712 
713  if ((taglen & 0x007f) == 8) {
714  res = ast_asprintf(&p->a_crypto, "%d AEAD_AES_%d_GCM_%d inline:%s",
715  p->tag, 128 + ((taglen & 0x0300) >> 2), taglen & 0x007f, p->local_key64);
716  } else if ((taglen & 0x007f) == 16) {
717  res = ast_asprintf(&p->a_crypto, "%d AEAD_AES_%d_GCM inline:%s",
718  p->tag, 128 + ((taglen & 0x0300) >> 2), p->local_key64);
719  } else if ((taglen & 0x0300) && !(taglen & 0x0080)) {
720  res = ast_asprintf(&p->a_crypto, "%d AES_%d_CM_HMAC_SHA1_%d inline:%s",
721  p->tag, 128 + ((taglen & 0x0300) >> 2), taglen & 0x007f, p->local_key64);
722  } else {
723  res = ast_asprintf(&p->a_crypto, "%d AES_CM_%d_HMAC_SHA1_%d inline:%s",
724  p->tag, 128 + ((taglen & 0x0300) >> 2), taglen & 0x007f, p->local_key64);
725  }
726  if (res == -1 || !p->a_crypto) {
727  ast_log(LOG_ERROR, "Could not allocate memory for crypto line\n");
728  return -1;
729  }
730 
731  ast_debug(1, "Crypto line: a=crypto:%s\n", p->a_crypto);
732 
733  return 0;
734 }
735 
736 static int set_crypto_policy(struct ast_srtp_policy *policy, int suite_val, const unsigned char *master_key, int key_len, unsigned long ssrc, int inbound)
737 {
738  if (policy_res.set_master_key(policy, master_key, key_len, NULL, 0) < 0) {
739  return -1;
740  }
741 
742  if (policy_res.set_suite(policy, suite_val)) {
743  ast_log(LOG_WARNING, "Could not set remote SRTP suite\n");
744  return -1;
745  }
746 
747  policy_res.set_ssrc(policy, ssrc, inbound);
748 
749  return 0;
750 }
751 
752 static int crypto_activate(struct ast_sdp_crypto *p, int suite_val, unsigned char *remote_key, int key_len, struct ast_rtp_instance *rtp)
753 {
754  struct ast_srtp_policy *local_policy = NULL;
755  struct ast_srtp_policy *remote_policy = NULL;
756  struct ast_rtp_instance_stats stats = {0,};
757  int res = -1;
758 
759  if (!p) {
760  return -1;
761  }
762 
763  if (!(local_policy = policy_res.alloc())) {
764  return -1;
765  }
766 
767  if (!(remote_policy = policy_res.alloc())) {
768  goto err;
769  }
770 
772  goto err;
773  }
774 
775  if (set_crypto_policy(local_policy, suite_val, p->local_key, key_len, stats.local_ssrc, 0) < 0) {
776  goto err;
777  }
778 
779  if (set_crypto_policy(remote_policy, suite_val, remote_key, key_len, 0, 1) < 0) {
780  goto err;
781  }
782 
783  /* Add the SRTP policies */
784  if (ast_rtp_instance_add_srtp_policy(rtp, remote_policy, local_policy, 0)) {
785  ast_log(LOG_WARNING, "Could not set SRTP policies\n");
786  goto err;
787  }
788 
789  ast_debug(1 , "SRTP policy activated\n");
790  res = 0;
791 
792 err:
793  if (local_policy) {
794  policy_res.destroy(local_policy);
795  }
796 
797  if (remote_policy) {
798  policy_res.destroy(remote_policy);
799  }
800 
801  return res;
802 }
803 
804 static int res_sdp_crypto_parse_offer(struct ast_rtp_instance *rtp, struct ast_sdp_srtp *srtp, const char *attr)
805 {
806  char *str = NULL;
807  char *tag = NULL;
808  char *suite = NULL;
809  char *key_params = NULL;
810  char *key_param = NULL;
811  char *session_params = NULL;
812  char *key_salt = NULL; /* The actual master key and key salt */
813  char *lifetime = NULL; /* Key lifetime (# of RTP packets) */
814  char *mki = NULL; /* Master Key Index */
815  int found = 0;
816  int key_len_from_sdp;
817  int key_len_expected;
818  int tag_from_sdp;
819  int suite_val = 0;
820  unsigned char remote_key[SRTP_MAX_KEY_LEN];
821  int taglen;
822  double sdes_lifetime;
823  struct ast_sdp_crypto *crypto;
824  struct ast_sdp_srtp *tmp;
825 
826  str = ast_strdupa(attr);
827 
828  tag = strsep(&str, " ");
829  suite = strsep(&str, " ");
830  key_params = strsep(&str, " ");
831  session_params = strsep(&str, " ");
832 
833  if (!tag || !suite) {
834  ast_log(LOG_WARNING, "Unrecognized crypto attribute a=%s\n", attr);
835  return -1;
836  }
837 
838  /* RFC4568 9.1 - tag is 1-9 digits */
839  if (sscanf(tag, "%30d", &tag_from_sdp) != 1 || tag_from_sdp < 0 || tag_from_sdp > 999999999) {
840  ast_log(LOG_WARNING, "Unacceptable a=crypto tag: %s\n", tag);
841  return -1;
842  }
843 
844  if (!ast_strlen_zero(session_params)) {
845  ast_log(LOG_WARNING, "Unsupported crypto parameters: %s\n", session_params);
846  return -1;
847  }
848 
849  /* On egress, Asterisk sent several crypto lines in the SIP/SDP offer
850  The remote party might have choosen another line than the first */
851  for (tmp = srtp; tmp && tmp->crypto && tmp->crypto->tag != tag_from_sdp;) {
852  tmp = AST_LIST_NEXT(tmp, sdp_srtp_list);
853  }
854  if (tmp) { /* tag matched an already created crypto line */
855  unsigned int flags = tmp->flags;
856 
857  /* Make that crypto line the head of the list, not by changing the
858  list structure but by exchanging the content of the list members */
859  crypto = tmp->crypto;
860  tmp->crypto = srtp->crypto;
861  tmp->flags = srtp->flags;
862  srtp->crypto = crypto;
863  srtp->flags = flags;
864  } else {
865  crypto = srtp->crypto;
866  crypto->tag = tag_from_sdp;
867  }
868 
869  ast_clear_flag(srtp, AST_SRTP_CRYPTO_TAG_8);
870  ast_clear_flag(srtp, AST_SRTP_CRYPTO_TAG_16);
871  ast_clear_flag(srtp, AST_SRTP_CRYPTO_TAG_32);
872  ast_clear_flag(srtp, AST_SRTP_CRYPTO_TAG_80);
873  ast_clear_flag(srtp, AST_SRTP_CRYPTO_AES_192);
874  ast_clear_flag(srtp, AST_SRTP_CRYPTO_AES_256);
875  ast_clear_flag(srtp, AST_SRTP_CRYPTO_OLD_NAME);
876 
877  if (!strcmp(suite, "AES_CM_128_HMAC_SHA1_80")) {
878  suite_val = AST_AES_CM_128_HMAC_SHA1_80;
879  ast_set_flag(srtp, AST_SRTP_CRYPTO_TAG_80);
880  key_len_expected = 30;
881  } else if (!strcmp(suite, "AES_CM_128_HMAC_SHA1_32")) {
882  suite_val = AST_AES_CM_128_HMAC_SHA1_32;
883  ast_set_flag(srtp, AST_SRTP_CRYPTO_TAG_32);
884  key_len_expected = 30;
885 #if defined(HAVE_SRTP_192) && defined(ENABLE_SRTP_AES_192)
886  } else if (!strcmp(suite, "AES_192_CM_HMAC_SHA1_80")) {
887  suite_val = AST_AES_CM_192_HMAC_SHA1_80;
888  ast_set_flag(srtp, AST_SRTP_CRYPTO_TAG_80);
889  ast_set_flag(srtp, AST_SRTP_CRYPTO_AES_192);
890  key_len_expected = 38;
891  } else if (!strcmp(suite, "AES_192_CM_HMAC_SHA1_32")) {
892  suite_val = AST_AES_CM_192_HMAC_SHA1_32;
893  ast_set_flag(srtp, AST_SRTP_CRYPTO_TAG_32);
894  ast_set_flag(srtp, AST_SRTP_CRYPTO_AES_192);
895  key_len_expected = 38;
896  /* RFC used a different name while in draft, some still use that */
897  } else if (!strcmp(suite, "AES_CM_192_HMAC_SHA1_80")) {
898  suite_val = AST_AES_CM_192_HMAC_SHA1_80;
899  ast_set_flag(srtp, AST_SRTP_CRYPTO_TAG_80);
900  ast_set_flag(srtp, AST_SRTP_CRYPTO_AES_192);
901  ast_set_flag(srtp, AST_SRTP_CRYPTO_OLD_NAME);
902  key_len_expected = 38;
903  } else if (!strcmp(suite, "AES_CM_192_HMAC_SHA1_32")) {
904  suite_val = AST_AES_CM_192_HMAC_SHA1_32;
905  ast_set_flag(srtp, AST_SRTP_CRYPTO_TAG_32);
906  ast_set_flag(srtp, AST_SRTP_CRYPTO_AES_192);
907  ast_set_flag(srtp, AST_SRTP_CRYPTO_OLD_NAME);
908  key_len_expected = 38;
909 #endif
910 #if defined(HAVE_SRTP_256) && defined(ENABLE_SRTP_AES_256)
911  } else if (!strcmp(suite, "AES_256_CM_HMAC_SHA1_80")) {
912  suite_val = AST_AES_CM_256_HMAC_SHA1_80;
913  ast_set_flag(srtp, AST_SRTP_CRYPTO_TAG_80);
914  ast_set_flag(srtp, AST_SRTP_CRYPTO_AES_256);
915  key_len_expected = 46;
916  } else if (!strcmp(suite, "AES_256_CM_HMAC_SHA1_32")) {
917  suite_val = AST_AES_CM_256_HMAC_SHA1_32;
918  ast_set_flag(srtp, AST_SRTP_CRYPTO_TAG_32);
919  ast_set_flag(srtp, AST_SRTP_CRYPTO_AES_256);
920  key_len_expected = 46;
921  /* RFC used a different name while in draft, some still use that */
922  } else if (!strcmp(suite, "AES_CM_256_HMAC_SHA1_80")) {
923  suite_val = AST_AES_CM_256_HMAC_SHA1_80;
924  ast_set_flag(srtp, AST_SRTP_CRYPTO_TAG_80);
925  ast_set_flag(srtp, AST_SRTP_CRYPTO_AES_256);
926  ast_set_flag(srtp, AST_SRTP_CRYPTO_OLD_NAME);
927  key_len_expected = 46;
928  } else if (!strcmp(suite, "AES_CM_256_HMAC_SHA1_32")) {
929  suite_val = AST_AES_CM_256_HMAC_SHA1_32;
930  ast_set_flag(srtp, AST_SRTP_CRYPTO_TAG_32);
931  ast_set_flag(srtp, AST_SRTP_CRYPTO_AES_256);
932  ast_set_flag(srtp, AST_SRTP_CRYPTO_OLD_NAME);
933  key_len_expected = 46;
934 #endif
935 #if defined(HAVE_SRTP_GCM) && defined(ENABLE_SRTP_AES_GCM)
936  } else if (!strcmp(suite, "AEAD_AES_128_GCM")) {
937  suite_val = AST_AES_GCM_128;
938  ast_set_flag(srtp, AST_SRTP_CRYPTO_TAG_16);
939  key_len_expected = AES_128_GCM_KEYSIZE_WSALT;
940  /* RFC contained a (too) short auth tag for RTP media, some still use that */
941  } else if (!strcmp(suite, "AEAD_AES_128_GCM_8")) {
942  suite_val = AST_AES_GCM_128_8;
943  ast_set_flag(srtp, AST_SRTP_CRYPTO_TAG_8);
944  key_len_expected = AES_128_GCM_KEYSIZE_WSALT;
945 #endif
946 #if defined(HAVE_SRTP_GCM) && defined(ENABLE_SRTP_AES_GCM) && defined(ENABLE_SRTP_AES_256)
947  } else if (!strcmp(suite, "AEAD_AES_256_GCM")) {
948  suite_val = AST_AES_GCM_256;
949  ast_set_flag(srtp, AST_SRTP_CRYPTO_TAG_16);
950  ast_set_flag(srtp, AST_SRTP_CRYPTO_AES_256);
951  key_len_expected = AES_256_GCM_KEYSIZE_WSALT;
952  /* RFC contained a (too) short auth tag for RTP media, some still use that */
953  } else if (!strcmp(suite, "AEAD_AES_256_GCM_8")) {
954  suite_val = AST_AES_GCM_256_8;
955  ast_set_flag(srtp, AST_SRTP_CRYPTO_TAG_8);
956  ast_set_flag(srtp, AST_SRTP_CRYPTO_AES_256);
957  key_len_expected = AES_256_GCM_KEYSIZE_WSALT;
958 #endif
959  } else {
960  ast_verb(1, "Unsupported crypto suite: %s\n", suite);
961  return -1;
962  }
963 
964  while ((key_param = strsep(&key_params, ";"))) {
965  unsigned int n_lifetime;
966  char *method = NULL;
967  char *info = NULL;
968 
969  method = strsep(&key_param, ":");
970  info = strsep(&key_param, ";");
971  sdes_lifetime = 0;
972 
973  if (strcmp(method, "inline")) {
974  continue;
975  }
976 
977  key_salt = strsep(&info, "|");
978 
979  /* The next parameter can be either lifetime or MKI */
980  lifetime = strsep(&info, "|");
981  if (!lifetime) {
982  found = 1;
983  break;
984  }
985 
986  mki = strchr(lifetime, ':');
987  if (mki) {
988  mki = lifetime;
989  lifetime = NULL;
990  } else {
991  mki = strsep(&info, "|");
992  }
993 
994  if (mki && *mki != '1') {
995  ast_log(LOG_NOTICE, "Crypto MKI handling is not supported: ignoring attribute %s\n", attr);
996  continue;
997  }
998 
999  if (lifetime) {
1000  if (!strncmp(lifetime, "2^", 2)) {
1001  char *lifetime_val = lifetime + 2;
1002 
1003  /* Exponential lifetime */
1004  if (sscanf(lifetime_val, "%30u", &n_lifetime) != 1) {
1005  ast_log(LOG_NOTICE, "Failed to parse lifetime value in crypto attribute: %s\n", attr);
1006  continue;
1007  }
1008 
1009  if (n_lifetime > 48) {
1010  /* Yeah... that's a bit big. */
1011  ast_log(LOG_NOTICE, "Crypto lifetime exponent of '%u' is a bit large; using 48\n", n_lifetime);
1012  n_lifetime = 48;
1013  }
1014  sdes_lifetime = pow(2, n_lifetime);
1015  } else {
1016  /* Decimal lifetime */
1017  if (sscanf(lifetime, "%30u", &n_lifetime) != 1) {
1018  ast_log(LOG_NOTICE, "Failed to parse lifetime value in crypto attribute: %s\n", attr);
1019  continue;
1020  }
1021  sdes_lifetime = n_lifetime;
1022  }
1023 
1024  /* Accept anything above ~5.8 hours. Less than ~5.8; reject. */
1025  if (sdes_lifetime < 1048576) {
1026  ast_log(LOG_NOTICE, "Rejecting crypto attribute '%s': lifetime '%f' too short\n", attr, sdes_lifetime);
1027  continue;
1028  }
1029  }
1030 
1031  ast_debug(2, "Crypto attribute '%s' accepted with lifetime '%f', MKI '%s'\n",
1032  attr, sdes_lifetime, mki ? mki : "-");
1033 
1034  found = 1;
1035  break;
1036  }
1037 
1038  if (!found) {
1039  ast_log(LOG_NOTICE, "SRTP crypto offer not acceptable: '%s'\n", attr);
1040  return -1;
1041  }
1042 
1043  key_len_from_sdp = ast_base64decode(remote_key, key_salt, sizeof(remote_key));
1044  if (key_len_from_sdp != key_len_expected) {
1045  ast_log(LOG_WARNING, "SRTP descriptions key length is '%d', not '%d'\n",
1046  key_len_from_sdp, key_len_expected);
1047  return -1;
1048  }
1049 
1050  /* on default, the key is 30 (AES-128); throw that away (only) when the suite changed actually */
1051  /* ingress: optional, but saves one expensive call to get_random(.) */
1052  /* egress: required, because the local key was communicated before the remote key is processed */
1053  if (crypto->key_len != key_len_from_sdp) {
1054  if (!crypto_init_keys(crypto, key_len_from_sdp)) {
1055  return -1;
1056  }
1057  } else if (!memcmp(crypto->remote_key, remote_key, key_len_from_sdp)) {
1058  ast_debug(1, "SRTP remote key unchanged; maintaining current policy\n");
1059  return 0;
1060  }
1061 
1062  if (key_len_from_sdp > sizeof(crypto->remote_key)) {
1063  ast_log(LOG_ERROR,
1064  "SRTP key buffer is %zu although it must be at least %d bytes\n",
1065  sizeof(crypto->remote_key), key_len_from_sdp);
1066  return -1;
1067  }
1068  memcpy(crypto->remote_key, remote_key, key_len_from_sdp);
1069 
1070  if (crypto_activate(crypto, suite_val, remote_key, key_len_from_sdp, rtp) < 0) {
1071  return -1;
1072  }
1073 
1074  if (ast_test_flag(srtp, AST_SRTP_CRYPTO_TAG_32)) {
1075  taglen = 32;
1076  } else if (ast_test_flag(srtp, AST_SRTP_CRYPTO_TAG_16)) {
1077  taglen = 16;
1078  } else if (ast_test_flag(srtp, AST_SRTP_CRYPTO_TAG_8)) {
1079  taglen = 8;
1080  } else {
1081  taglen = 80;
1082  }
1083  if (ast_test_flag(srtp, AST_SRTP_CRYPTO_AES_256)) {
1084  taglen |= 0x0200;
1085  } else if (ast_test_flag(srtp, AST_SRTP_CRYPTO_AES_192)) {
1086  taglen |= 0x0100;
1087  }
1088  if (ast_test_flag(srtp, AST_SRTP_CRYPTO_OLD_NAME)) {
1089  taglen |= 0x0080;
1090  }
1091 
1092  /* Finally, rebuild the crypto line */
1093  if (res_sdp_crypto_build_offer(crypto, taglen)) {
1094  return -1;
1095  }
1096 
1097  ast_set_flag(srtp, AST_SRTP_CRYPTO_OFFER_OK);
1098  return 0;
1099 }
1100 
1101 static const char *res_sdp_srtp_get_attr(struct ast_sdp_srtp *srtp, int dtls_enabled, int default_taglen_32)
1102 {
1103  int taglen;
1104 
1105  if (!srtp) {
1106  return NULL;
1107  }
1108 
1109  /* Set encryption properties */
1110  if (!srtp->crypto) {
1111  if (AST_LIST_NEXT(srtp, sdp_srtp_list)) {
1112  srtp->crypto = res_sdp_crypto_alloc();
1113  ast_log(LOG_ERROR, "SRTP SDP list was not empty\n");
1114  } else {
1115  const int len = default_taglen_32 ? AST_SRTP_CRYPTO_TAG_32 : AST_SRTP_CRYPTO_TAG_80;
1116  const int attr[][3] = {
1117  /* This array creates the following list:
1118  * a=crypto:1 AES_CM_128_HMAC_SHA1_ ...
1119  * a=crypto:2 AEAD_AES_128_GCM ...
1120  * a=crypto:3 AES_256_CM_HMAC_SHA1_ ...
1121  * a=crypto:4 AEAD_AES_256_GCM ...
1122  * a=crypto:5 AES_192_CM_HMAC_SHA1_ ...
1123  * something like 'AEAD_AES_192_GCM' is not specified by the RFCs
1124  *
1125  * If you want to prefer another crypto suite or you want to
1126  * exclude a suite, change this array and recompile Asterisk.
1127  * This list cannot be changed from rtp.conf because you should
1128  * know what you are doing. Especially AES-192 and AES-GCM are
1129  * broken in many VoIP clients, see
1130  * https://github.com/cisco/libsrtp/pull/170
1131  * https://github.com/cisco/libsrtp/pull/184
1132  * Furthermore, AES-GCM uses a shorter crypto-suite string which
1133  * causes Nokia phones based on Symbian/S60 to reject the whole
1134  * INVITE with status 500, even if a matching suite was offered.
1135  * AES-256 might just waste your processor cycles, especially if
1136  * your TLS transport is not secured with equivalent grade, see
1137  * https://security.stackexchange.com/q/61361
1138  * Therefore, AES-128 was preferred here.
1139  *
1140  * If you want to enable one of those defines, please, go for
1141  * CFLAGS='-DENABLE_SRTP_AES_GCM' ./configure && sudo make install
1142  */
1143  { len, 0, 30 },
1144 #if defined(HAVE_SRTP_GCM) && defined(ENABLE_SRTP_AES_GCM)
1145  { AST_SRTP_CRYPTO_TAG_16, 0, AES_128_GCM_KEYSIZE_WSALT },
1146 #endif
1147 #if defined(HAVE_SRTP_256) && defined(ENABLE_SRTP_AES_256)
1148  { len, AST_SRTP_CRYPTO_AES_256, 46 },
1149 #endif
1150 #if defined(HAVE_SRTP_GCM) && defined(ENABLE_SRTP_AES_GCM) && defined(ENABLE_SRTP_AES_256)
1151  { AST_SRTP_CRYPTO_TAG_16, AST_SRTP_CRYPTO_AES_256, AES_256_GCM_KEYSIZE_WSALT },
1152 #endif
1153 #if defined(HAVE_SRTP_192) && defined(ENABLE_SRTP_AES_192)
1154  { len, AST_SRTP_CRYPTO_AES_192, 38 },
1155 #endif
1156  };
1157  struct ast_sdp_srtp *tmp = srtp;
1158  int i;
1159 
1160  for (i = 0; i < ARRAY_LEN(attr); i++) {
1161  if (attr[i][0]) {
1162  ast_set_flag(tmp, attr[i][0]);
1163  }
1164  if (attr[i][1]) {
1165  ast_set_flag(tmp, attr[i][1]);
1166  }
1167  tmp->crypto = sdp_crypto_alloc(attr[i][2]); /* key_len */
1168  tmp->crypto->tag = (i + 1); /* tag starts at 1 */
1169 
1170  if (i < ARRAY_LEN(attr) - 1) {
1171  AST_LIST_NEXT(tmp, sdp_srtp_list) = ast_sdp_srtp_alloc();
1172  tmp = AST_LIST_NEXT(tmp, sdp_srtp_list);
1173  }
1174  }
1175  }
1176  }
1177 
1178  if (dtls_enabled) {
1179  /* If DTLS-SRTP is enabled the key details will be pulled from TLS */
1180  return NULL;
1181  }
1182 
1183  /* set the key length based on INVITE or settings */
1184  if (ast_test_flag(srtp, AST_SRTP_CRYPTO_TAG_80)) {
1185  taglen = 80;
1186  } else if (ast_test_flag(srtp, AST_SRTP_CRYPTO_TAG_32)) {
1187  taglen = 32;
1188  } else if (ast_test_flag(srtp, AST_SRTP_CRYPTO_TAG_16)) {
1189  taglen = 16;
1190  } else if (ast_test_flag(srtp, AST_SRTP_CRYPTO_TAG_8)) {
1191  taglen = 8;
1192  } else {
1193  taglen = default_taglen_32 ? 32 : 80;
1194  }
1195  if (ast_test_flag(srtp, AST_SRTP_CRYPTO_AES_256)) {
1196  taglen |= 0x0200;
1197  } else if (ast_test_flag(srtp, AST_SRTP_CRYPTO_AES_192)) {
1198  taglen |= 0x0100;
1199  }
1200  if (ast_test_flag(srtp, AST_SRTP_CRYPTO_OLD_NAME)) {
1201  taglen |= 0x0080;
1202  }
1203 
1204  if (srtp->crypto && (res_sdp_crypto_build_offer(srtp->crypto, taglen) >= 0)) {
1205  return srtp->crypto->a_crypto;
1206  }
1207 
1208  ast_log(LOG_WARNING, "No SRTP key management enabled\n");
1209  return NULL;
1210 }
1211 
1212 static struct ast_sdp_crypto_api res_sdp_crypto_api = {
1213  .dtor = res_sdp_crypto_dtor,
1214  .alloc = res_sdp_crypto_alloc,
1215  .build_offer = res_sdp_crypto_build_offer,
1216  .parse_offer = res_sdp_crypto_parse_offer,
1217  .get_attr = res_sdp_srtp_get_attr,
1218 };
1219 
1220 static void res_srtp_shutdown(void)
1221 {
1222  ast_sdp_crypto_unregister(&res_sdp_crypto_api);
1223  ast_rtp_engine_unregister_srtp();
1224  srtp_install_event_handler(NULL);
1225 #ifdef HAVE_SRTP_SHUTDOWN
1226  srtp_shutdown();
1227 #endif
1228  g_initialized = 0;
1229 }
1230 
1231 static int res_srtp_init(void)
1232 {
1233  if (g_initialized) {
1234  return 0;
1235  }
1236 
1237  if (srtp_init() != err_status_ok) {
1238  ast_log(AST_LOG_WARNING, "Failed to initialize libsrtp\n");
1239  return -1;
1240  }
1241 
1242  srtp_install_event_handler(srtp_event_cb);
1243 
1244  if (ast_rtp_engine_register_srtp(&srtp_res, &policy_res)) {
1245  ast_log(AST_LOG_WARNING, "Failed to register SRTP with rtp engine\n");
1246  res_srtp_shutdown();
1247  return -1;
1248  }
1249 
1250  if (ast_sdp_crypto_register(&res_sdp_crypto_api)) {
1251  ast_log(AST_LOG_WARNING, "Failed to register SDP SRTP crypto API\n");
1252  res_srtp_shutdown();
1253  return -1;
1254  }
1255 
1256 #ifdef HAVE_SRTP_GET_VERSION
1257  ast_verb(2, "%s initialized\n", srtp_get_version_string());
1258 #else
1259  ast_verb(2, "libsrtp initialized\n");
1260 #endif
1261 
1262  g_initialized = 1;
1263  return 0;
1264 }
1265 
1266 /*
1267  * Exported functions
1268  */
1269 
1270 static int load_module(void)
1271 {
1272  return res_srtp_init();
1273 }
1274 
1275 static int unload_module(void)
1276 {
1277  res_srtp_shutdown();
1278  return 0;
1279 }
1280 
1281 AST_MODULE_INFO(ASTERISK_GPL_KEY, AST_MODFLAG_GLOBAL_SYMBOLS | AST_MODFLAG_LOAD_ORDER, "Secure RTP (SRTP)",
1282  .support_level = AST_MODULE_SUPPORT_CORE,
1283  .load = load_module,
1284  .unload = unload_module,
1285  .load_pri = AST_MODPRI_CHANNEL_DEPEND,
1286 );
structure for secure RTP audio
Definition: sdp_srtp.h:38
Asterisk main include file. File version handling, generic pbx functions.
int ao2_container_count(struct ao2_container *c)
Returns the number of elements in a container.
int ast_rtp_instance_get_stats(struct ast_rtp_instance *instance, struct ast_rtp_instance_stats *stats, enum ast_rtp_instance_stat stat)
Retrieve statistics about an RTP instance.
Definition: rtp_engine.c:2570
#define OBJ_POINTER
Definition: astobj2.h:1150
#define AST_LIST_NEXT(elm, field)
Returns the next entry in the list after the given entry.
Definition: linkedlists.h:439
void ao2_iterator_destroy(struct ao2_iterator *iter)
Destroy a container iterator.
int ast_rtp_instance_add_srtp_policy(struct ast_rtp_instance *instance, struct ast_srtp_policy *remote_policy, struct ast_srtp_policy *local_policy, int rtcp)
Add or replace the SRTP policies for the given RTP instance.
Definition: rtp_engine.c:2884
Utility functions.
#define ast_asprintf(ret, fmt,...)
A wrapper for asprintf()
Definition: astmm.h:267
int ast_base64decode(unsigned char *dst, const char *src, int max)
Decode data from base64.
Definition: utils.c:296
sdp_crypto_destroy_cb dtor
Definition: sdp_srtp.h:128
struct ast_module * self
Definition: module.h:356
#define AST_FRIENDLY_OFFSET
Offset into a frame's data buffer.
SRTP and SDP Security descriptions.
#define ast_strdupa(s)
duplicate a string in memory from the stack
Definition: astmm.h:298
Asterisk internal frame definitions.
#define ast_debug(level,...)
Log a DEBUG message.
int ast_base64encode(char *dst, const unsigned char *src, int srclen, int max)
Encode data in base64.
Definition: utils.c:406
unsigned int local_ssrc
Definition: rtp_engine.h:452
unsigned int ast_rtp_instance_get_ssrc(struct ast_rtp_instance *rtp)
Retrieve the local SSRC value that we will be using.
Definition: rtp_engine.c:3959
#define ast_module_ref(mod)
Hold a reference to the module.
Definition: module.h:457
#define ast_calloc(num, len)
A wrapper for calloc()
Definition: astmm.h:202
struct ast_sdp_srtp * ast_sdp_srtp_alloc(void)
allocate a ast_sdp_srtp structure
Definition: sdp_srtp.c:41
Support for logging to various files, console and syslog Configuration in file logger.conf.
#define ast_module_unref(mod)
Release a reference to the module.
Definition: module.h:483
When we need to walk through a container, we use an ao2_iterator to keep track of the current positio...
Definition: astobj2.h:1821
void ast_sdp_crypto_unregister(struct ast_sdp_crypto_api *api)
Unregister SDP SRTP crypto processing routines.
Definition: sdp_srtp.c:132
#define ao2_t_find(container, arg, flags, tag)
Definition: astobj2.h:1734
int ast_sdp_crypto_register(struct ast_sdp_crypto_api *api)
Register SDP SRTP crypto processing routines.
Definition: sdp_srtp.c:123
SRTP resource.
Generic container type.
#define ASTERISK_GPL_KEY
The text the key() function should return.
Definition: module.h:46
Pluggable RTP Architecture.
Asterisk module definitions.
static int g_initialized
Definition: res_srtp.c:82
struct ao2_iterator ao2_iterator_init(struct ao2_container *c, int flags) attribute_warn_unused_result
Create an iterator for a container.
unsigned int remote_ssrc
Definition: rtp_engine.h:454
int(* create)(struct ast_srtp **srtp, struct ast_rtp_instance *rtp, struct ast_srtp_policy *policy)
Definition: res_srtp.h:36