2 * Asterisk -- An open source telephony toolkit.
4 * Copyright (C) 2005, Mikael Magnusson
6 * Mikael Magnusson <mikma@users.sourceforge.net>
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.
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.
18 * Builds on libSRTP http://srtp.sourceforge.net
23 * \brief Secure RTP (SRTP)
26 * Specified in RFC 3711.
28 * \author Mikael Magnusson <mikma@users.sourceforge.net>
33 <support_level>core</support_level>
36 /* See https://wiki.asterisk.org/wiki/display/AST/Secure+Calling */
40 ASTERISK_FILE_VERSION(__FILE__, "$Revision$")
42 #include <srtp/srtp.h>
44 #include "asterisk/lock.h"
45 #include "asterisk/sched.h"
46 #include "asterisk/module.h"
47 #include "asterisk/options.h"
48 #include "asterisk/rtp_engine.h"
49 #include "asterisk/astobj2.h"
52 struct ast_rtp_instance *rtp;
53 struct ao2_container *policies;
55 const struct ast_srtp_cb *cb;
58 unsigned char buf[8192 + AST_FRIENDLY_OFFSET];
59 unsigned char rtcpbuf[8192 + AST_FRIENDLY_OFFSET];
62 struct ast_srtp_policy {
66 static int g_initialized = 0;
69 static int ast_srtp_create(struct ast_srtp **srtp, struct ast_rtp_instance *rtp, struct ast_srtp_policy *policy);
70 static void ast_srtp_destroy(struct ast_srtp *srtp);
71 static int ast_srtp_add_stream(struct ast_srtp *srtp, struct ast_srtp_policy *policy);
72 static int ast_srtp_change_source(struct ast_srtp *srtp, unsigned int from_ssrc, unsigned int to_ssrc);
74 static int ast_srtp_unprotect(struct ast_srtp *srtp, void *buf, int *len, int rtcp);
75 static int ast_srtp_protect(struct ast_srtp *srtp, void **buf, int *len, int rtcp);
76 static void ast_srtp_set_cb(struct ast_srtp *srtp, const struct ast_srtp_cb *cb, void *data);
77 static int ast_srtp_get_random(unsigned char *key, size_t len);
79 /* Policy functions */
80 static struct ast_srtp_policy *ast_srtp_policy_alloc(void);
81 static void ast_srtp_policy_destroy(struct ast_srtp_policy *policy);
82 static int ast_srtp_policy_set_suite(struct ast_srtp_policy *policy, enum ast_srtp_suite suite);
83 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);
84 static void ast_srtp_policy_set_ssrc(struct ast_srtp_policy *policy, unsigned long ssrc, int inbound);
86 static struct ast_srtp_res srtp_res = {
87 .create = ast_srtp_create,
88 .destroy = ast_srtp_destroy,
89 .add_stream = ast_srtp_add_stream,
90 .change_source = ast_srtp_change_source,
91 .set_cb = ast_srtp_set_cb,
92 .unprotect = ast_srtp_unprotect,
93 .protect = ast_srtp_protect,
94 .get_random = ast_srtp_get_random
97 static struct ast_srtp_policy_res policy_res = {
98 .alloc = ast_srtp_policy_alloc,
99 .destroy = ast_srtp_policy_destroy,
100 .set_suite = ast_srtp_policy_set_suite,
101 .set_master_key = ast_srtp_policy_set_master_key,
102 .set_ssrc = ast_srtp_policy_set_ssrc
105 static const char *srtp_errstr(int err)
109 return "nothing to report";
110 case err_status_fail:
111 return "unspecified failure";
112 case err_status_bad_param:
113 return "unsupported parameter";
114 case err_status_alloc_fail:
115 return "couldn't allocate memory";
116 case err_status_dealloc_fail:
117 return "couldn't deallocate properly";
118 case err_status_init_fail:
119 return "couldn't initialize";
120 case err_status_terminus:
121 return "can't process as much data as requested";
122 case err_status_auth_fail:
123 return "authentication failure";
124 case err_status_cipher_fail:
125 return "cipher failure";
126 case err_status_replay_fail:
127 return "replay check failed (bad index)";
128 case err_status_replay_old:
129 return "replay check failed (index too old)";
130 case err_status_algo_fail:
131 return "algorithm failed test routine";
132 case err_status_no_such_op:
133 return "unsupported operation";
134 case err_status_no_ctx:
135 return "no appropriate context found";
136 case err_status_cant_check:
137 return "unable to perform desired validation";
138 case err_status_key_expired:
139 return "can't use key any more";
145 static int policy_hash_fn(const void *obj, const int flags)
147 const struct ast_srtp_policy *policy = obj;
149 return policy->sp.ssrc.type == ssrc_specific ? policy->sp.ssrc.value : policy->sp.ssrc.type;
152 static int policy_cmp_fn(void *obj, void *arg, int flags)
154 const struct ast_srtp_policy *one = obj, *two = arg;
156 return one->sp.ssrc.type == two->sp.ssrc.type && one->sp.ssrc.value == two->sp.ssrc.value;
159 static struct ast_srtp_policy *find_policy(struct ast_srtp *srtp, const srtp_policy_t *policy, int flags)
161 struct ast_srtp_policy tmp = {
163 .ssrc.type = policy->ssrc.type,
164 .ssrc.value = policy->ssrc.value,
168 return ao2_t_find(srtp->policies, &tmp, flags, "Looking for policy");
171 static struct ast_srtp *res_srtp_new(void)
173 struct ast_srtp *srtp;
175 if (!(srtp = ast_calloc(1, sizeof(*srtp)))) {
176 ast_log(LOG_ERROR, "Unable to allocate memory for srtp\n");
180 if (!(srtp->policies = ao2_t_container_alloc(5, policy_hash_fn, policy_cmp_fn, "SRTP policy container"))) {
191 struct ast_srtp_policy
193 static void srtp_event_cb(srtp_event_data_t *data)
195 switch (data->event) {
196 case event_ssrc_collision:
197 ast_debug(1, "SSRC collision\n");
199 case event_key_soft_limit:
200 ast_debug(1, "event_key_soft_limit\n");
202 case event_key_hard_limit:
203 ast_debug(1, "event_key_hard_limit\n");
205 case event_packet_index_limit:
206 ast_debug(1, "event_packet_index_limit\n");
211 static void ast_srtp_policy_set_ssrc(struct ast_srtp_policy *policy,
212 unsigned long ssrc, int inbound)
215 policy->sp.ssrc.type = ssrc_specific;
216 policy->sp.ssrc.value = ssrc;
218 policy->sp.ssrc.type = inbound ? ssrc_any_inbound : ssrc_any_outbound;
222 static void policy_destructor(void *obj)
224 struct ast_srtp_policy *policy = obj;
226 if (policy->sp.key) {
227 ast_free(policy->sp.key);
228 policy->sp.key = NULL;
232 static struct ast_srtp_policy *ast_srtp_policy_alloc()
234 struct ast_srtp_policy *tmp;
236 if (!(tmp = ao2_t_alloc(sizeof(*tmp), policy_destructor, "Allocating policy"))) {
237 ast_log(LOG_ERROR, "Unable to allocate memory for srtp_policy\n");
243 static void ast_srtp_policy_destroy(struct ast_srtp_policy *policy)
245 ao2_t_ref(policy, -1, "Destroying policy");
248 static int policy_set_suite(crypto_policy_t *p, enum ast_srtp_suite suite)
251 case AST_AES_CM_128_HMAC_SHA1_80:
252 p->cipher_type = AES_128_ICM;
253 p->cipher_key_len = 30;
254 p->auth_type = HMAC_SHA1;
255 p->auth_key_len = 20;
256 p->auth_tag_len = 10;
257 p->sec_serv = sec_serv_conf_and_auth;
260 case AST_AES_CM_128_HMAC_SHA1_32:
261 p->cipher_type = AES_128_ICM;
262 p->cipher_key_len = 30;
263 p->auth_type = HMAC_SHA1;
264 p->auth_key_len = 20;
266 p->sec_serv = sec_serv_conf_and_auth;
270 ast_log(LOG_ERROR, "Invalid crypto suite: %d\n", suite);
275 static int ast_srtp_policy_set_suite(struct ast_srtp_policy *policy, enum ast_srtp_suite suite)
277 return policy_set_suite(&policy->sp.rtp, suite) | policy_set_suite(&policy->sp.rtcp, suite);
280 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)
282 size_t size = key_len + salt_len;
283 unsigned char *master_key;
285 if (policy->sp.key) {
286 ast_free(policy->sp.key);
287 policy->sp.key = NULL;
290 if (!(master_key = ast_calloc(1, size))) {
294 memcpy(master_key, key, key_len);
295 memcpy(master_key + key_len, salt, salt_len);
297 policy->sp.key = master_key;
302 static int ast_srtp_get_random(unsigned char *key, size_t len)
304 return crypto_get_random(key, len) != err_status_ok ? -1: 0;
307 static void ast_srtp_set_cb(struct ast_srtp *srtp, const struct ast_srtp_cb *cb, void *data)
317 /* Vtable functions */
318 static int ast_srtp_unprotect(struct ast_srtp *srtp, void *buf, int *len, int rtcp)
323 struct ast_rtp_instance_stats stats = {0,};
327 for (i = 0; i < 2; i++) {
328 res = rtcp ? srtp_unprotect_rtcp(srtp->session, buf, len) : srtp_unprotect(srtp->session, buf, len);
329 if (res != err_status_no_ctx) {
333 if (srtp->cb && srtp->cb->no_ctx) {
334 if (ast_rtp_instance_get_stats(srtp->rtp, &stats, AST_RTP_INSTANCE_STAT_REMOTE_SSRC)) {
337 if (srtp->cb->no_ctx(srtp->rtp, stats.remote_ssrc, srtp->data) < 0) {
345 if (retry == 0 && res == err_status_replay_old) {
346 ast_log(LOG_WARNING, "SRTP unprotect: %s\n", srtp_errstr(res));
349 struct ast_srtp_policy *policy;
350 struct ao2_iterator it;
351 int policies_count = 0;
354 ast_log(LOG_WARNING, "SRTP destroy before re-create\n");
355 srtp_dealloc(srtp->session);
358 policies_count = ao2_container_count(srtp->policies);
360 // get the first to build up
361 it = ao2_iterator_init(srtp->policies, 0);
362 policy = ao2_iterator_next(&it);
364 ast_log(LOG_WARNING, "SRTP try to re-create\n");
365 if (srtp_create(&srtp->session, &policy->sp) == err_status_ok) {
366 ast_log(LOG_WARNING, "SRTP re-created with first policy\n");
368 // unref first element
369 ao2_t_ref(policy, -1, "Unreffing first policy for re-creating srtp session");
371 // if we have more than one policy, add them afterwards
372 if (policies_count > 1) {
373 ast_log(LOG_WARNING, "Add all the other %d policies\n", policies_count-1);
374 while ((policy = ao2_iterator_next(&it))) {
375 srtp_add_stream(srtp->session, &policy->sp);
376 ao2_t_ref(policy, -1, "Unreffing n-th policy for re-creating srtp session");
381 ao2_iterator_destroy(&it);
384 ao2_iterator_destroy(&it);
388 if (res != err_status_ok && res != err_status_replay_fail ) {
389 if ((srtp->warned >= 10) && !((srtp->warned - 10) % 100)) {
390 ast_log(LOG_WARNING, "SRTP unprotect: %s %d\n", srtp_errstr(res), srtp->warned);
402 static int ast_srtp_protect(struct ast_srtp *srtp, void **buf, int *len, int rtcp)
405 unsigned char *localbuf;
407 if ((*len + SRTP_MAX_TRAILER_LEN) > sizeof(srtp->buf)) {
411 localbuf = rtcp ? srtp->rtcpbuf : srtp->buf;
413 memcpy(localbuf, *buf, *len);
415 if ((res = rtcp ? srtp_protect_rtcp(srtp->session, localbuf, len) : srtp_protect(srtp->session, localbuf, len)) != err_status_ok && res != err_status_replay_fail) {
416 ast_log(LOG_WARNING, "SRTP protect: %s\n", srtp_errstr(res));
424 static int ast_srtp_create(struct ast_srtp **srtp, struct ast_rtp_instance *rtp, struct ast_srtp_policy *policy)
426 struct ast_srtp *temp;
428 if (!(temp = res_srtp_new())) {
432 if (srtp_create(&temp->session, &policy->sp) != err_status_ok) {
436 ast_module_ref(ast_module_info->self);
440 ao2_t_link((*srtp)->policies, policy, "Created initial policy");
445 static void ast_srtp_destroy(struct ast_srtp *srtp)
448 srtp_dealloc(srtp->session);
451 ao2_t_callback(srtp->policies, OBJ_UNLINK | OBJ_NODATA | OBJ_MULTIPLE, NULL, NULL, "Unallocate policy");
452 ao2_t_ref(srtp->policies, -1, "Destroying container");
455 ast_module_unref(ast_module_info->self);
458 static int ast_srtp_add_stream(struct ast_srtp *srtp, struct ast_srtp_policy *policy)
460 struct ast_srtp_policy *match;
462 if ((match = find_policy(srtp, &policy->sp, OBJ_POINTER))) {
463 ast_debug(3, "Policy already exists, not re-adding\n");
464 ao2_t_ref(match, -1, "Unreffing already existing policy");
468 if (srtp_add_stream(srtp->session, &policy->sp) != err_status_ok) {
472 ao2_t_link(srtp->policies, policy, "Added additional stream");
477 static int ast_srtp_change_source(struct ast_srtp *srtp, unsigned int from_ssrc, unsigned int to_ssrc)
479 struct ast_srtp_policy *match;
480 struct srtp_policy_t sp = {
481 .ssrc.type = ssrc_specific,
482 .ssrc.value = from_ssrc,
486 /* If we find a mach, return and unlink it from the container so we
487 * can change the SSRC (which is part of the hash) and then have
488 * ast_srtp_add_stream link it back in if all is well */
489 if ((match = find_policy(srtp, &sp, OBJ_POINTER | OBJ_UNLINK))) {
490 match->sp.ssrc.value = to_ssrc;
491 if (ast_srtp_add_stream(srtp, match)) {
492 ast_log(LOG_WARNING, "Couldn't add stream\n");
493 } else if ((status = srtp_remove_stream(srtp->session, from_ssrc))) {
494 ast_debug(3, "Couldn't remove stream (%d)\n", status);
496 ao2_t_ref(match, -1, "Unreffing found policy in change_source");
502 static int res_srtp_init(void)
508 if (srtp_init() != err_status_ok) {
512 srtp_install_event_handler(srtp_event_cb);
514 return ast_rtp_engine_register_srtp(&srtp_res, &policy_res);
521 static int load_module(void)
523 return res_srtp_init();
526 static int unload_module(void)
528 ast_rtp_engine_unregister_srtp();
532 AST_MODULE_INFO(ASTERISK_GPL_KEY, AST_MODFLAG_GLOBAL_SYMBOLS | AST_MODFLAG_LOAD_ORDER, "Secure RTP (SRTP)",
534 .unload = unload_module,
535 .load_pri = AST_MODPRI_CHANNEL_DEPEND,