Secure RTP (SRTP) More...

#include "asterisk.h"
#include <math.h>
#include <srtp/srtp.h>
#include <srtp/crypto_kernel.h>
#include "asterisk/astobj2.h"
#include "asterisk/frame.h"
#include "asterisk/logger.h"
#include "asterisk/module.h"
#include "asterisk/sdp_srtp.h"
#include "asterisk/res_srtp.h"
#include "asterisk/rtp_engine.h"
#include "asterisk/utils.h"

Include dependency graph for res_srtp.c:

Go to the source code of this file.

Data Structures
struct	ast_sdp_crypto

struct	ast_srtp

struct	ast_srtp_policy

Functions
static void	__reg_module (void)

static void	__unreg_module (void)

struct ast_module *	AST_MODULE_SELF_SYM (void)

static int	ast_srtp_add_stream (struct ast_srtp srtp, struct ast_srtp_policy policy)

static int	ast_srtp_change_source (struct ast_srtp *srtp, unsigned int from_ssrc, unsigned int to_ssrc)

static int	ast_srtp_create (struct ast_srtp *srtp, struct ast_rtp_instance rtp, struct ast_srtp_policy *policy)

static void	ast_srtp_destroy (struct ast_srtp *srtp)

static int	ast_srtp_get_random (unsigned char *key, size_t len)

static struct ast_srtp_policy *	ast_srtp_policy_alloc (void)

static void	ast_srtp_policy_destroy (struct ast_srtp_policy *policy)

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)

static void	ast_srtp_policy_set_ssrc (struct ast_srtp_policy *policy, unsigned long ssrc, int inbound)

static int	ast_srtp_policy_set_suite (struct ast_srtp_policy *policy, enum ast_srtp_suite suite)

static int	ast_srtp_protect (struct ast_srtp srtp, void buf, int len, int rtcp)

static int	ast_srtp_replace (struct ast_srtp *srtp, struct ast_rtp_instance rtp, struct ast_srtp_policy *policy)

static void	ast_srtp_set_cb (struct ast_srtp srtp, const struct ast_srtp_cb cb, void *data)

static int	ast_srtp_unprotect (struct ast_srtp srtp, void buf, int *len, int rtcp)

static int	crypto_activate (struct ast_sdp_crypto p, int suite_val, unsigned char remote_key, int key_len, struct ast_rtp_instance *rtp)

static struct ast_sdp_crypto *	crypto_init_keys (struct ast_sdp_crypto *p, const int key_len)

static struct ast_srtp_policy *	find_policy (struct ast_srtp srtp, const srtp_policy_t policy, int flags)

static int	load_module (void)

static int	policy_cmp_fn (void obj, void arg, int flags)

static void	policy_destructor (void *obj)

static int	policy_hash_fn (const void *obj, const int flags)

static int	policy_set_suite (crypto_policy_t *p, enum ast_srtp_suite suite)

static struct ast_sdp_crypto *	res_sdp_crypto_alloc (void)

static int	res_sdp_crypto_build_offer (struct ast_sdp_crypto *p, int taglen)

static void	res_sdp_crypto_dtor (struct ast_sdp_crypto *crypto)

static int	res_sdp_crypto_parse_offer (struct ast_rtp_instance rtp, struct ast_sdp_srtp srtp, const char *attr)

static const char *	res_sdp_srtp_get_attr (struct ast_sdp_srtp *srtp, int dtls_enabled, int default_taglen_32)

static int	res_srtp_init (void)

static struct ast_srtp *	res_srtp_new (void)

static void	res_srtp_shutdown (void)

static struct ast_sdp_crypto *	sdp_crypto_alloc (const int key_len)

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)

static const char *	srtp_errstr (int err)

static void	srtp_event_cb (srtp_event_data_t *data)

static int	unload_module (void)

Variables
static struct ast_module_info	__mod_info = { .name = AST_MODULE, .flags = AST_MODFLAG_GLOBAL_SYMBOLS \| AST_MODFLAG_LOAD_ORDER , .description = "Secure RTP (SRTP)" , .key = "This paragraph is copyright (c) 2006 by Digium, Inc. \In order for your module to load, it must return this \key via a function called \"key\". Any code which \includes this paragraph must be licensed under the GNU \General Public License version 2 or later (at your \option). In addition to Digium's general reservations \of rights, Digium expressly reserves the right to \allow other parties to license this paragraph under \different terms. Any use of Digium, Inc. trademarks or \logos (including \"Asterisk\" or \"Digium\") without \express written permission of Digium, Inc. is prohibited.\n" , .buildopt_sum = AST_BUILDOPT_SUM, .support_level = AST_MODULE_SUPPORT_CORE, .load = load_module, .unload = unload_module, .load_pri = AST_MODPRI_CHANNEL_DEPEND, }

static const struct ast_module_info *	ast_module_info = &__mod_info

static int	g_initialized = 0

static struct ast_srtp_policy_res	policy_res

static struct ast_sdp_crypto_api	res_sdp_crypto_api

static struct ast_srtp_res	srtp_res

Detailed Description

Secure RTP (SRTP)

Secure RTP (SRTP) Specified in RFC 3711.

Author: Mikael Magnusson mikma.nosp@m.@use.nosp@m.rs.so.nosp@m.urce.nosp@m.forge.nosp@m..net

Definition in file res_srtp.c.

Function Documentation

◆ __reg_module()

static void __reg_module ( void )

static

Definition at line 1312 of file res_srtp.c.

◆ __unreg_module()

static void __unreg_module ( void )

static

Definition at line 1312 of file res_srtp.c.

◆ AST_MODULE_SELF_SYM()

struct ast_module * AST_MODULE_SELF_SYM ( void )

Definition at line 1312 of file res_srtp.c.

◆ ast_srtp_add_stream()

static int ast_srtp_add_stream	(	struct ast_srtp *	srtp,
		struct ast_srtp_policy *	policy
	)

static

Definition at line 601 of file res_srtp.c.

{
    struct ast_srtp_policy *match;
 
    /* For existing streams, replace if its an SSRC stream, or bail if its a wildcard */
    if ((match = find_policy(srtp, &policy->sp, OBJ_POINTER))) {
        if (policy->sp.ssrc.type != ssrc_specific) {
            ast_log(AST_LOG_WARNING, "Cannot replace an existing wildcard policy\n");
            ao2_t_ref(match, -1, "Unreffing already existing policy");
            return -1;
        } else {
            if (srtp_remove_stream(srtp->session, match->sp.ssrc.value) != err_status_ok) {
                ast_log(AST_LOG_WARNING, "Failed to remove SRTP stream for SSRC %u\n", match->sp.ssrc.value);
            }
            ao2_t_unlink(srtp->policies, match, "Remove existing match policy");
            ao2_t_ref(match, -1, "Unreffing already existing policy");
        }
    }
 
    ast_debug(3, "Adding new policy for %s %u\n",
        policy->sp.ssrc.type == ssrc_specific ? "SSRC" : "type",
        policy->sp.ssrc.type == ssrc_specific ? policy->sp.ssrc.value : policy->sp.ssrc.type);
    if (srtp_add_stream(srtp->session, &policy->sp) != err_status_ok) {
        ast_log(AST_LOG_WARNING, "Failed to add SRTP stream for %s %u\n",
            policy->sp.ssrc.type == ssrc_specific ? "SSRC" : "type",
            policy->sp.ssrc.type == ssrc_specific ? policy->sp.ssrc.value : policy->sp.ssrc.type);
        return -1;
    }
 
    ao2_t_link(srtp->policies, policy, "Added additional stream");
 
    return 0;
}

References ao2_t_link, ao2_t_ref, ao2_t_unlink, ast_debug, ast_log, AST_LOG_WARNING, err_status_ok, find_policy(), match(), OBJ_POINTER, ast_srtp::policies, ast_srtp::session, and ast_srtp_policy::sp.

Referenced by ast_srtp_change_source().

◆ ast_srtp_change_source()

static int ast_srtp_change_source	(	struct ast_srtp *	srtp,
		unsigned int	from_ssrc,
		unsigned int	to_ssrc
	)

static

Definition at line 635 of file res_srtp.c.

{
    struct ast_srtp_policy *match;
    struct srtp_policy_t sp = {
        .ssrc.type = ssrc_specific,
        .ssrc.value = from_ssrc,
    };
    err_status_t status;
 
    /* If we find a match, return and unlink it from the container so we
     * can change the SSRC (which is part of the hash) and then have
     * ast_srtp_add_stream link it back in if all is well */
    if ((match = find_policy(srtp, &sp, OBJ_POINTER | OBJ_UNLINK))) {
        match->sp.ssrc.value = to_ssrc;
        if (ast_srtp_add_stream(srtp, match)) {
            ast_log(LOG_WARNING, "Couldn't add stream\n");
        } else if ((status = srtp_remove_stream(srtp->session, from_ssrc))) {
            ast_debug(3, "Couldn't remove stream (%u)\n", status);
        }
        ao2_t_ref(match, -1, "Unreffing found policy in change_source");
    }
 
    return 0;
}

References ao2_t_ref, ast_debug, ast_log, ast_srtp_add_stream(), err_status_t, find_policy(), LOG_WARNING, match(), OBJ_POINTER, OBJ_UNLINK, ast_srtp::session, and status.

◆ ast_srtp_create()

static int ast_srtp_create	(	struct ast_srtp **	srtp,
		struct ast_rtp_instance *	rtp,
		struct ast_srtp_policy *	policy
	)

static

Definition at line 542 of file res_srtp.c.

{
    struct ast_srtp *temp;
    int status;
 
    if (!(temp = res_srtp_new())) {
        return -1;
    }
    ast_module_ref(ast_module_info->self);
 
    /* Any failures after this point can use ast_srtp_destroy to destroy the instance */
    status = srtp_create(&temp->session, &policy->sp);
    if (status != err_status_ok) {
        /* Session either wasn't created or was created and dealloced. */
        temp->session = NULL;
        ast_srtp_destroy(temp);
        ast_log(LOG_ERROR, "Failed to create srtp session on rtp instance (%p) - %s\n",
                rtp, srtp_errstr(status));
        return -1;
    }
 
    temp->rtp = rtp;
    *srtp = temp;
 
    ao2_t_link((*srtp)->policies, policy, "Created initial policy");
 
    return 0;
}

References ao2_t_link, ast_log, ast_module_ref, ast_srtp_destroy(), err_status_ok, LOG_ERROR, NULL, res_srtp_new(), ast_srtp::rtp, ast_module_info::self, ast_srtp::session, ast_srtp_policy::sp, srtp_errstr(), and status.

Referenced by ast_srtp_replace().

◆ ast_srtp_destroy()

static void ast_srtp_destroy ( struct ast_srtp * srtp )

static

Definition at line 588 of file res_srtp.c.

{
    if (srtp->session) {
        srtp_dealloc(srtp->session);
    }
 
    ao2_t_callback(srtp->policies, OBJ_UNLINK | OBJ_NODATA | OBJ_MULTIPLE, NULL, NULL, "Unallocate policy");
    ao2_t_ref(srtp->policies, -1, "Destroying container");
 
    ast_free(srtp);
    ast_module_unref(ast_module_info->self);
}

References ao2_t_callback, ao2_t_ref, ast_free, ast_module_unref, NULL, OBJ_MULTIPLE, OBJ_NODATA, OBJ_UNLINK, ast_srtp::policies, ast_module_info::self, and ast_srtp::session.

Referenced by ast_srtp_create(), and ast_srtp_replace().

◆ ast_srtp_get_random()

static int ast_srtp_get_random	(	unsigned char *	key,
		size_t	len
	)

static

Definition at line 375 of file res_srtp.c.

{
#ifdef HAVE_OPENSSL
    return RAND_bytes(key, len) > 0 ? 0: -1;
#else
    return crypto_get_random(key, len) != err_status_ok ? -1: 0;
#endif
}

References err_status_ok, and len().

◆ ast_srtp_policy_alloc()

static struct ast_srtp_policy * ast_srtp_policy_alloc ( void )

static

Definition at line 278 of file res_srtp.c.

{
    struct ast_srtp_policy *tmp;
 
    if (!(tmp = ao2_t_alloc(sizeof(*tmp), policy_destructor, "Allocating policy"))) {
        ast_log(LOG_ERROR, "Unable to allocate memory for srtp_policy\n");
    }
 
    return tmp;
}

References ao2_t_alloc, ast_log, LOG_ERROR, and policy_destructor().

◆ ast_srtp_policy_destroy()

static void ast_srtp_policy_destroy ( struct ast_srtp_policy * policy )

static

Definition at line 289 of file res_srtp.c.

{
    ao2_t_ref(policy, -1, "Destroying policy");
}

References ao2_t_ref.

◆ ast_srtp_policy_set_master_key()

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
	)

static

Definition at line 353 of file res_srtp.c.

{
    size_t size = key_len + salt_len;
    unsigned char *master_key;
 
    if (policy->sp.key) {
        ast_free(policy->sp.key);
        policy->sp.key = NULL;
    }
 
    if (!(master_key = ast_calloc(1, size))) {
        return -1;
    }
 
    memcpy(master_key, key, key_len);
    memcpy(master_key + key_len, salt, salt_len);
 
    policy->sp.key = master_key;
 
    return 0;
}

References ast_calloc, ast_free, NULL, and ast_srtp_policy::sp.

◆ ast_srtp_policy_set_ssrc()

static void ast_srtp_policy_set_ssrc	(	struct ast_srtp_policy *	policy,
		unsigned long	ssrc,
		int	inbound
	)

static

Definition at line 257 of file res_srtp.c.

{
    if (ssrc) {
        policy->sp.ssrc.type = ssrc_specific;
        policy->sp.ssrc.value = ssrc;
    } else {
        policy->sp.ssrc.type = inbound ? ssrc_any_inbound : ssrc_any_outbound;
    }
}

References ast_srtp_policy::sp.

◆ ast_srtp_policy_set_suite()

static int ast_srtp_policy_set_suite	(	struct ast_srtp_policy *	policy,
		enum ast_srtp_suite	suite
	)

static

Definition at line 348 of file res_srtp.c.

{
    return policy_set_suite(&policy->sp.rtp, suite) | policy_set_suite(&policy->sp.rtcp, suite);
}

References policy_set_suite(), and ast_srtp_policy::sp.

◆ ast_srtp_protect()

static int ast_srtp_protect	(	struct ast_srtp *	srtp,
		void **	buf,
		int *	len,
		int	rtcp
	)

static

Definition at line 514 of file res_srtp.c.

{
    int res;
    unsigned char *localbuf;
 
    if (!srtp->session) {
        ast_log(LOG_ERROR, "SRTP protect %s - missing session\n", rtcp ? "rtcp" : "rtp");
        errno = EINVAL;
        return -1;
    }
 
    if ((*len + SRTP_MAX_TRAILER_LEN) > sizeof(srtp->buf)) {
        return -1;
    }
 
    localbuf = rtcp ? srtp->rtcpbuf : srtp->buf;
 
    memcpy(localbuf, *buf, *len);
 
    if ((res = rtcp ? srtp_protect_rtcp(srtp->session, localbuf, len) : srtp_protect(srtp->session, localbuf, len)) != err_status_ok && res != err_status_replay_fail) {
        ast_log(LOG_WARNING, "SRTP protect: %s\n", srtp_errstr(res));
        return -1;
    }
 
    *buf = localbuf;
    return *len;
}

References ast_log, ast_srtp::buf, buf, err_status_ok, err_status_replay_fail, errno, len(), LOG_ERROR, LOG_WARNING, ast_srtp::rtcpbuf, ast_srtp::session, and srtp_errstr().

◆ ast_srtp_replace()

static int ast_srtp_replace	(	struct ast_srtp **	srtp,
		struct ast_rtp_instance *	rtp,
		struct ast_srtp_policy *	policy
	)

static

Definition at line 571 of file res_srtp.c.

{
    struct ast_srtp *old = *srtp;
    int res = ast_srtp_create(srtp, rtp, policy);
 
    if (!res && old) {
        ast_srtp_destroy(old);
    }
 
    if (res) {
        ast_log(LOG_ERROR, "Failed to replace srtp (%p) on rtp instance (%p) "
                "- keeping old\n", *srtp, rtp);
    }
 
    return res;
}

References ast_log, ast_srtp_create(), ast_srtp_destroy(), LOG_ERROR, and ast_srtp::rtp.

◆ ast_srtp_set_cb()

static void ast_srtp_set_cb	(	struct ast_srtp *	srtp,
		const struct ast_srtp_cb *	cb,
		void *	data
	)

static

Definition at line 384 of file res_srtp.c.

{
    if (!srtp) {
        return;
    }
 
    srtp->cb = cb;
    srtp->data = data;
}

References ast_srtp::cb, and ast_srtp::data.

◆ ast_srtp_unprotect()

static int ast_srtp_unprotect	(	struct ast_srtp *	srtp,
		void *	buf,
		int *	len,
		int	rtcp
	)

static

Definition at line 395 of file res_srtp.c.

{
    int res = 0;
    int i;
    int rtcp  = (flags & 0x01) >> 0;
    int retry = (flags & 0x02) >> 1;
    struct ast_rtp_instance_stats stats = {0,};
 
tryagain:
 
    if (!srtp->session) {
        ast_log(LOG_ERROR, "SRTP unprotect %s - missing session\n", rtcp ? "rtcp" : "rtp");
        errno = EINVAL;
        return -1;
    }
 
    for (i = 0; i < 2; i++) {
        res = rtcp ? srtp_unprotect_rtcp(srtp->session, buf, len) : srtp_unprotect(srtp->session, buf, len);
        if (res != err_status_no_ctx) {
            break;
        }
 
        if (srtp->cb && srtp->cb->no_ctx) {
            if (ast_rtp_instance_get_stats(srtp->rtp, &stats, AST_RTP_INSTANCE_STAT_REMOTE_SSRC)) {
                break;
            }
            if (srtp->cb->no_ctx(srtp->rtp, stats.remote_ssrc, srtp->data) < 0) {
                break;
            }
        } else {
            break;
        }
    }
 
    if (retry == 0  && res == err_status_replay_old) {
        ast_log(AST_LOG_NOTICE, "SRTP unprotect failed with %s, retrying\n", srtp_errstr(res));
 
        if (srtp->session) {
            struct ast_srtp_policy *policy;
            struct ao2_iterator it;
            int policies_count;
 
            /* dealloc first */
            ast_debug(5, "SRTP destroy before re-create\n");
            srtp_dealloc(srtp->session);
 
            /* get the count */
            policies_count = ao2_container_count(srtp->policies);
 
            /* get the first to build up */
            it = ao2_iterator_init(srtp->policies, 0);
            policy = ao2_iterator_next(&it);
 
            ast_debug(5, "SRTP try to re-create\n");
            if (policy) {
                int res_srtp_create = srtp_create(&srtp->session, &policy->sp);
                if (res_srtp_create == err_status_ok) {
                    ast_debug(5, "SRTP re-created with first policy\n");
                    ao2_t_ref(policy, -1, "Unreffing first policy for re-creating srtp session");
 
                    /* if we have more than one policy, add them */
                    if (policies_count > 1) {
                        ast_debug(5, "Add all the other %d policies\n",
                            policies_count - 1);
                        while ((policy = ao2_iterator_next(&it))) {
                            srtp_add_stream(srtp->session, &policy->sp);
                            ao2_t_ref(policy, -1, "Unreffing n-th policy for re-creating srtp session");
                        }
                    }
 
                    retry++;
                    ao2_iterator_destroy(&it);
                    goto tryagain;
                }
                ast_log(LOG_ERROR, "SRTP session could not be re-created after unprotect failure: %s\n", srtp_errstr(res_srtp_create));
 
                /* If srtp_create() fails with a previously alloced session, it will have been dealloced before returning. */
                srtp->session = NULL;
 
                ao2_t_ref(policy, -1, "Unreffing first policy after srtp_create failed");
            }
            ao2_iterator_destroy(&it);
        }
    }
 
    if (!srtp->session) {
        errno = EINVAL;
        return -1;
    }
 
    if (res != err_status_ok && res != err_status_replay_fail ) {
        /*
         * Authentication failures happen when an active attacker tries to
         * insert malicious RTP packets. Furthermore, authentication failures
         * happen, when the other party encrypts the sRTP data in an unexpected
         * way. This happens quite often with RTCP. Therefore, when you see
         * authentication failures, try to identify the implementation
         * (author and product name) used by your other party. Try to investigate
         * whether they use a custom library or an outdated version of libSRTP.
         */
        if (rtcp) {
            ast_verb(2, "SRTCP unprotect failed on SSRC %u because of %s\n",
                ast_rtp_instance_get_ssrc(srtp->rtp), srtp_errstr(res));
        } else {
            if ((srtp->warned >= 10) && !((srtp->warned - 10) % 150)) {
                ast_verb(2, "SRTP unprotect failed on SSRC %u because of %s %d\n",
                    ast_rtp_instance_get_ssrc(srtp->rtp), srtp_errstr(res), srtp->warned);
                srtp->warned = 11;
            } else {
                srtp->warned++;
            }
        }
        errno = EAGAIN;
        return -1;
    }
 
    return *len;
}

References ao2_container_count(), ao2_iterator_destroy(), ao2_iterator_init(), ao2_iterator_next, ao2_t_ref, ast_debug, ast_log, AST_LOG_NOTICE, ast_rtp_instance_get_ssrc(), ast_rtp_instance_get_stats(), AST_RTP_INSTANCE_STAT_REMOTE_SSRC, ast_verb, buf, ast_srtp::cb, ast_srtp::data, err_status_no_ctx, err_status_ok, err_status_replay_fail, err_status_replay_old, errno, len(), LOG_ERROR, ast_srtp_cb::no_ctx, NULL, ast_srtp::policies, ast_rtp_instance_stats::remote_ssrc, ast_srtp::rtp, ast_srtp::session, ast_srtp_policy::sp, srtp_errstr(), and ast_srtp::warned.

◆ crypto_activate()

static int crypto_activate	(	struct ast_sdp_crypto *	p,
		int	suite_val,
		unsigned char *	remote_key,
		int	key_len,
		struct ast_rtp_instance *	rtp
	)

static

Definition at line 778 of file res_srtp.c.

{
    struct ast_srtp_policy *local_policy = NULL;
    struct ast_srtp_policy *remote_policy = NULL;
    struct ast_rtp_instance_stats stats = {0,};
    int res = -1;
 
    if (!p) {
        return -1;
    }
 
    if (!(local_policy = policy_res.alloc())) {
        return -1;
    }
 
    if (!(remote_policy = policy_res.alloc())) {
        goto err;
    }
 
    if (ast_rtp_instance_get_stats(rtp, &stats, AST_RTP_INSTANCE_STAT_LOCAL_SSRC)) {
        goto err;
    }
 
    if (set_crypto_policy(local_policy, suite_val, p->local_key, key_len, stats.local_ssrc, 0) < 0) {
        goto err;
    }
 
    if (set_crypto_policy(remote_policy, suite_val, remote_key, key_len, 0, 1) < 0) {
        goto err;
    }
 
    /* Add the SRTP policies */
    if (ast_rtp_instance_add_srtp_policy(rtp, remote_policy, local_policy, 0)) {
        ast_log(LOG_WARNING, "Could not set SRTP policies\n");
        goto err;
    }
 
    ast_debug(1 , "SRTP policy activated\n");
    res = 0;
 
err:
    if (local_policy) {
        policy_res.destroy(local_policy);
    }
 
    if (remote_policy) {
        policy_res.destroy(remote_policy);
    }
 
    return res;
}

References ast_srtp_policy_res::alloc, ast_debug, ast_log, ast_rtp_instance_add_srtp_policy(), ast_rtp_instance_get_stats(), AST_RTP_INSTANCE_STAT_LOCAL_SSRC, ast_srtp_policy_res::destroy, ast_sdp_crypto::local_key, ast_rtp_instance_stats::local_ssrc, LOG_WARNING, NULL, policy_res, and set_crypto_policy().

Referenced by res_sdp_crypto_parse_offer().

◆ crypto_init_keys()

static struct ast_sdp_crypto * crypto_init_keys	(	struct ast_sdp_crypto *	p,
		const int	key_len
	)

static

Definition at line 680 of file res_srtp.c.

{
    unsigned char remote_key[key_len];
 
    if (srtp_res.get_random(p->local_key, key_len) < 0) {
        return NULL;
    }
 
    ast_base64encode(p->local_key64, p->local_key, key_len, sizeof(p->local_key64));
 
    p->key_len = ast_base64decode(remote_key, p->local_key64, sizeof(remote_key));
 
    if (p->key_len != key_len) {
        ast_log(LOG_ERROR, "base64 encode/decode bad len %d != %d\n", p->key_len, key_len);
        return NULL;
    }
 
    if (memcmp(remote_key, p->local_key, p->key_len)) {
        ast_log(LOG_ERROR, "base64 encode/decode bad key\n");
        return NULL;
    }
 
    ast_debug(1 , "local_key64 %s len %zu\n", p->local_key64, strlen(p->local_key64));
 
    return p;
}

References ast_base64decode(), ast_base64encode(), ast_debug, ast_log, ast_srtp_res::get_random, ast_sdp_crypto::key_len, ast_sdp_crypto::local_key, ast_sdp_crypto::local_key64, LOG_ERROR, NULL, ast_sdp_crypto::remote_key, and srtp_res.

Referenced by res_sdp_crypto_parse_offer(), and sdp_crypto_alloc().

◆ find_policy()

static struct ast_srtp_policy * find_policy	(	struct ast_srtp *	srtp,
		const srtp_policy_t *	policy,
		int	flags
	)

static

Definition at line 203 of file res_srtp.c.

{
    struct ast_srtp_policy tmp = {
        .sp = {
            .ssrc.type = policy->ssrc.type,
            .ssrc.value = policy->ssrc.value,
        },
    };
 
    return ao2_t_find(srtp->policies, &tmp, flags, "Looking for policy");
}

References ao2_t_find, ast_srtp::policies, and ast_srtp_policy::sp.

Referenced by ast_srtp_add_stream(), and ast_srtp_change_source().

◆ load_module()

static int load_module ( void )

static

Definition at line 1296 of file res_srtp.c.

{
    return res_srtp_init();
}

References res_srtp_init().

◆ policy_cmp_fn()

static int policy_cmp_fn	(	void *	obj,
		void *	arg,
		int	flags
	)

static

Definition at line 196 of file res_srtp.c.

{
    const struct ast_srtp_policy *one = obj, *two = arg;
 
    return one->sp.ssrc.type == two->sp.ssrc.type && one->sp.ssrc.value == two->sp.ssrc.value;
}

References ast_srtp_policy::sp.

Referenced by res_srtp_new().

◆ policy_destructor()

static void policy_destructor ( void * obj )

static

Definition at line 268 of file res_srtp.c.

{
    struct ast_srtp_policy *policy = obj;
 
    if (policy->sp.key) {
        ast_free(policy->sp.key);
        policy->sp.key = NULL;
    }
}

References ast_free, NULL, and ast_srtp_policy::sp.

Referenced by ast_srtp_policy_alloc().

◆ policy_hash_fn()

static int policy_hash_fn	(	const void *	obj,
		const int	flags
	)

static

Definition at line 189 of file res_srtp.c.

{
    const struct ast_srtp_policy *policy = obj;
 
    return policy->sp.ssrc.type == ssrc_specific ? policy->sp.ssrc.value : policy->sp.ssrc.type;
}

References ast_srtp_policy::sp.

Referenced by res_srtp_new().

◆ policy_set_suite()

static int policy_set_suite	(	crypto_policy_t *	p,
		enum ast_srtp_suite	suite
	)

static

Definition at line 294 of file res_srtp.c.

{
    switch (suite) {
    case AST_AES_CM_128_HMAC_SHA1_80:
        crypto_policy_set_aes_cm_128_hmac_sha1_80(p);
        return 0;
 
    case AST_AES_CM_128_HMAC_SHA1_32:
        crypto_policy_set_aes_cm_128_hmac_sha1_32(p);
        return 0;
 
#if defined(HAVE_SRTP_192) && defined(ENABLE_SRTP_AES_192)
    case AST_AES_CM_192_HMAC_SHA1_80:
        crypto_policy_set_aes_cm_192_hmac_sha1_80(p);
        return 0;
 
    case AST_AES_CM_192_HMAC_SHA1_32:
        crypto_policy_set_aes_cm_192_hmac_sha1_32(p);
        return 0;
#endif
#if defined(HAVE_SRTP_256) && defined(ENABLE_SRTP_AES_256)
    case AST_AES_CM_256_HMAC_SHA1_80:
        crypto_policy_set_aes_cm_256_hmac_sha1_80(p);
        return 0;
 
    case AST_AES_CM_256_HMAC_SHA1_32:
        crypto_policy_set_aes_cm_256_hmac_sha1_32(p);
        return 0;
#endif
#if defined(HAVE_SRTP_GCM) && defined(ENABLE_SRTP_AES_GCM)
    case AST_AES_GCM_128:
        crypto_policy_set_aes_gcm_128_16_auth(p);
        return 0;
 
    case AST_AES_GCM_128_8:
        crypto_policy_set_aes_gcm_128_8_auth(p);
        return 0;
#endif
#if defined(HAVE_SRTP_GCM) && defined(ENABLE_SRTP_AES_GCM) && defined(ENABLE_SRTP_AES_256)
    case AST_AES_GCM_256:
        crypto_policy_set_aes_gcm_256_16_auth(p);
        return 0;
 
    case AST_AES_GCM_256_8:
        crypto_policy_set_aes_gcm_256_8_auth(p);
        return 0;
#endif
 
    default:
        ast_log(LOG_ERROR, "Invalid crypto suite: %u\n", suite);
        return -1;
    }
}

Referenced by ast_srtp_policy_set_suite().

◆ res_sdp_crypto_alloc()

static struct ast_sdp_crypto * res_sdp_crypto_alloc ( void )

static

Definition at line 726 of file res_srtp.c.

{
    return sdp_crypto_alloc(SRTP_MASTER_KEY_LEN);
}

References sdp_crypto_alloc(), and SRTP_MASTER_KEY_LEN.

Referenced by res_sdp_srtp_get_attr().

◆ res_sdp_crypto_build_offer()

static int res_sdp_crypto_build_offer	(	struct ast_sdp_crypto *	p,
		int	taglen
	)

static

Definition at line 731 of file res_srtp.c.

{
    int res;
 
    /* Rebuild the crypto line */
    ast_free(p->a_crypto);
    p->a_crypto = NULL;
 
    if ((taglen & 0x007f) == 8) {
        res = ast_asprintf(&p->a_crypto, "%d AEAD_AES_%d_GCM_%d inline:%s",
            p->tag, 128 + ((taglen & 0x0300) >> 2), taglen & 0x007f, p->local_key64);
    } else if ((taglen & 0x007f) == 16) {
        res = ast_asprintf(&p->a_crypto, "%d AEAD_AES_%d_GCM inline:%s",
            p->tag, 128 + ((taglen & 0x0300) >> 2), p->local_key64);
    } else if ((taglen & 0x0300) && !(taglen & 0x0080)) {
        res = ast_asprintf(&p->a_crypto, "%d AES_%d_CM_HMAC_SHA1_%d inline:%s",
            p->tag, 128 + ((taglen & 0x0300) >> 2), taglen & 0x007f, p->local_key64);
    } else {
        res = ast_asprintf(&p->a_crypto, "%d AES_CM_%d_HMAC_SHA1_%d inline:%s",
            p->tag, 128 + ((taglen & 0x0300) >> 2), taglen & 0x007f, p->local_key64);
    }
    if (res == -1 || !p->a_crypto) {
        ast_log(LOG_ERROR, "Could not allocate memory for crypto line\n");
        return -1;
    }
 
    ast_debug(1, "Crypto line: a=crypto:%s\n", p->a_crypto);
 
    return 0;
}

References ast_sdp_crypto::a_crypto, ast_asprintf, ast_debug, ast_free, ast_log, ast_sdp_crypto::local_key64, LOG_ERROR, NULL, and ast_sdp_crypto::tag.

Referenced by res_sdp_crypto_parse_offer(), and res_sdp_srtp_get_attr().

◆ res_sdp_crypto_dtor()

static void res_sdp_crypto_dtor ( struct ast_sdp_crypto * crypto )

static

Definition at line 669 of file res_srtp.c.

{
    if (crypto) {
        ast_free(crypto->a_crypto);
        crypto->a_crypto = NULL;
        ast_free(crypto);
 
        ast_module_unref(ast_module_info->self);
    }
}

References ast_sdp_crypto::a_crypto, ast_free, ast_module_unref, NULL, and ast_module_info::self.

Referenced by sdp_crypto_alloc().

◆ res_sdp_crypto_parse_offer()

static int res_sdp_crypto_parse_offer	(	struct ast_rtp_instance *	rtp,
		struct ast_sdp_srtp *	srtp,
		const char *	attr
	)

static

Definition at line 830 of file res_srtp.c.

{
    char *str = NULL;
    char *tag = NULL;
    char *suite = NULL;
    char *key_params = NULL;
    char *key_param = NULL;
    char *session_params = NULL;
    char *key_salt = NULL;       /* The actual master key and key salt */
    char *lifetime = NULL;       /* Key lifetime (# of RTP packets) */
    char *mki = NULL;            /* Master Key Index */
    int found = 0;
    int key_len_from_sdp;
    int key_len_expected;
    int tag_from_sdp;
    int suite_val = 0;
    unsigned char remote_key[SRTP_MAX_KEY_LEN];
    int taglen;
    double sdes_lifetime;
    struct ast_sdp_crypto *crypto;
    struct ast_sdp_srtp *tmp;
 
    str = ast_strdupa(attr);
 
    tag = strsep(&str, " ");
    suite = strsep(&str, " ");
    key_params = strsep(&str, " ");
    session_params = strsep(&str, " ");
 
    if (!tag || !suite) {
        ast_log(LOG_WARNING, "Unrecognized crypto attribute a=%s\n", attr);
        return -1;
    }
 
    /* RFC4568 9.1 - tag is 1-9 digits */
    if (sscanf(tag, "%30d", &tag_from_sdp) != 1 || tag_from_sdp < 0 || tag_from_sdp > 999999999) {
        ast_log(LOG_WARNING, "Unacceptable a=crypto tag: %s\n", tag);
        return -1;
    }
 
    if (!ast_strlen_zero(session_params)) {
        ast_log(LOG_WARNING, "Unsupported crypto parameters: %s\n", session_params);
        return -1;
    }
 
    /* On egress, Asterisk sent several crypto lines in the SIP/SDP offer
       The remote party might have choosen another line than the first */
    for (tmp = srtp; tmp && tmp->crypto && tmp->crypto->tag != tag_from_sdp;) {
        tmp = AST_LIST_NEXT(tmp, sdp_srtp_list);
    }
    if (tmp) { /* tag matched an already created crypto line */
        unsigned int flags = tmp->flags;
 
        /* Make that crypto line the head of the list, not by changing the
           list structure but by exchanging the content of the list members */
        crypto = tmp->crypto;
        tmp->crypto = srtp->crypto;
        tmp->flags = srtp->flags;
        srtp->crypto = crypto;
        srtp->flags = flags;
    } else {
        crypto = srtp->crypto;
        crypto->tag = tag_from_sdp;
    }
 
    ast_clear_flag(srtp, AST_SRTP_CRYPTO_TAG_8);
    ast_clear_flag(srtp, AST_SRTP_CRYPTO_TAG_16);
    ast_clear_flag(srtp, AST_SRTP_CRYPTO_TAG_32);
    ast_clear_flag(srtp, AST_SRTP_CRYPTO_TAG_80);
    ast_clear_flag(srtp, AST_SRTP_CRYPTO_AES_192);
    ast_clear_flag(srtp, AST_SRTP_CRYPTO_AES_256);
    ast_clear_flag(srtp, AST_SRTP_CRYPTO_OLD_NAME);
 
    if (!strcmp(suite, "AES_CM_128_HMAC_SHA1_80")) {
        suite_val = AST_AES_CM_128_HMAC_SHA1_80;
        ast_set_flag(srtp, AST_SRTP_CRYPTO_TAG_80);
        key_len_expected = 30;
    } else if (!strcmp(suite, "AES_CM_128_HMAC_SHA1_32")) {
        suite_val = AST_AES_CM_128_HMAC_SHA1_32;
        ast_set_flag(srtp, AST_SRTP_CRYPTO_TAG_32);
        key_len_expected = 30;
#if defined(HAVE_SRTP_192) && defined(ENABLE_SRTP_AES_192)
    } else if (!strcmp(suite, "AES_192_CM_HMAC_SHA1_80")) {
        suite_val = AST_AES_CM_192_HMAC_SHA1_80;
        ast_set_flag(srtp, AST_SRTP_CRYPTO_TAG_80);
        ast_set_flag(srtp, AST_SRTP_CRYPTO_AES_192);
        key_len_expected = 38;
    } else if (!strcmp(suite, "AES_192_CM_HMAC_SHA1_32")) {
        suite_val = AST_AES_CM_192_HMAC_SHA1_32;
        ast_set_flag(srtp, AST_SRTP_CRYPTO_TAG_32);
        ast_set_flag(srtp, AST_SRTP_CRYPTO_AES_192);
        key_len_expected = 38;
    /* RFC used a different name while in draft, some still use that */
    } else if (!strcmp(suite, "AES_CM_192_HMAC_SHA1_80")) {
        suite_val = AST_AES_CM_192_HMAC_SHA1_80;
        ast_set_flag(srtp, AST_SRTP_CRYPTO_TAG_80);
        ast_set_flag(srtp, AST_SRTP_CRYPTO_AES_192);
        ast_set_flag(srtp, AST_SRTP_CRYPTO_OLD_NAME);
        key_len_expected = 38;
    } else if (!strcmp(suite, "AES_CM_192_HMAC_SHA1_32")) {
        suite_val = AST_AES_CM_192_HMAC_SHA1_32;
        ast_set_flag(srtp, AST_SRTP_CRYPTO_TAG_32);
        ast_set_flag(srtp, AST_SRTP_CRYPTO_AES_192);
        ast_set_flag(srtp, AST_SRTP_CRYPTO_OLD_NAME);
        key_len_expected = 38;
#endif
#if defined(HAVE_SRTP_256) && defined(ENABLE_SRTP_AES_256)
    } else if (!strcmp(suite, "AES_256_CM_HMAC_SHA1_80")) {
        suite_val = AST_AES_CM_256_HMAC_SHA1_80;
        ast_set_flag(srtp, AST_SRTP_CRYPTO_TAG_80);
        ast_set_flag(srtp, AST_SRTP_CRYPTO_AES_256);
        key_len_expected = 46;
    } else if (!strcmp(suite, "AES_256_CM_HMAC_SHA1_32")) {
        suite_val = AST_AES_CM_256_HMAC_SHA1_32;
        ast_set_flag(srtp, AST_SRTP_CRYPTO_TAG_32);
        ast_set_flag(srtp, AST_SRTP_CRYPTO_AES_256);
        key_len_expected = 46;
    /* RFC used a different name while in draft, some still use that */
    } else if (!strcmp(suite, "AES_CM_256_HMAC_SHA1_80")) {
        suite_val = AST_AES_CM_256_HMAC_SHA1_80;
        ast_set_flag(srtp, AST_SRTP_CRYPTO_TAG_80);
        ast_set_flag(srtp, AST_SRTP_CRYPTO_AES_256);
        ast_set_flag(srtp, AST_SRTP_CRYPTO_OLD_NAME);
        key_len_expected = 46;
    } else if (!strcmp(suite, "AES_CM_256_HMAC_SHA1_32")) {
        suite_val = AST_AES_CM_256_HMAC_SHA1_32;
        ast_set_flag(srtp, AST_SRTP_CRYPTO_TAG_32);
        ast_set_flag(srtp, AST_SRTP_CRYPTO_AES_256);
        ast_set_flag(srtp, AST_SRTP_CRYPTO_OLD_NAME);
        key_len_expected = 46;
#endif
#if defined(HAVE_SRTP_GCM) && defined(ENABLE_SRTP_AES_GCM)
    } else if (!strcmp(suite, "AEAD_AES_128_GCM")) {
        suite_val = AST_AES_GCM_128;
        ast_set_flag(srtp, AST_SRTP_CRYPTO_TAG_16);
        key_len_expected = AES_128_GCM_KEYSIZE_WSALT;
    /* RFC contained a (too) short auth tag for RTP media, some still use that */
    } else if (!strcmp(suite, "AEAD_AES_128_GCM_8")) {
        suite_val = AST_AES_GCM_128_8;
        ast_set_flag(srtp, AST_SRTP_CRYPTO_TAG_8);
        key_len_expected = AES_128_GCM_KEYSIZE_WSALT;
#endif
#if defined(HAVE_SRTP_GCM) && defined(ENABLE_SRTP_AES_GCM) && defined(ENABLE_SRTP_AES_256)
    } else if (!strcmp(suite, "AEAD_AES_256_GCM")) {
        suite_val = AST_AES_GCM_256;
        ast_set_flag(srtp, AST_SRTP_CRYPTO_TAG_16);
        ast_set_flag(srtp, AST_SRTP_CRYPTO_AES_256);
        key_len_expected = AES_256_GCM_KEYSIZE_WSALT;
    /* RFC contained a (too) short auth tag for RTP media, some still use that */
    } else if (!strcmp(suite, "AEAD_AES_256_GCM_8")) {
        suite_val = AST_AES_GCM_256_8;
        ast_set_flag(srtp, AST_SRTP_CRYPTO_TAG_8);
        ast_set_flag(srtp, AST_SRTP_CRYPTO_AES_256);
        key_len_expected = AES_256_GCM_KEYSIZE_WSALT;
#endif
    } else {
        ast_debug(3, "Unsupported crypto suite: %s\n", suite);
        return -1;
    }
 
    while ((key_param = strsep(&key_params, ";"))) {
        unsigned int n_lifetime;
        char *method = NULL;
        char *info = NULL;
 
        method = strsep(&key_param, ":");
        info = strsep(&key_param, ";");
        sdes_lifetime = 0;
 
        if (strcmp(method, "inline")) {
            continue;
        }
 
        key_salt = strsep(&info, "|");
 
        /* The next parameter can be either lifetime or MKI */
        lifetime = strsep(&info, "|");
        if (!lifetime) {
            found = 1;
            break;
        }
 
        mki = strchr(lifetime, ':');
        if (mki) {
            mki = lifetime;
            lifetime = NULL;
        } else {
            mki = strsep(&info, "|");
        }
 
        if (mki && *mki != '1') {
            ast_log(LOG_NOTICE, "Crypto MKI handling is not supported: ignoring attribute %s\n", attr);
            continue;
        }
 
        if (lifetime) {
            if (!strncmp(lifetime, "2^", 2)) {
                char *lifetime_val = lifetime + 2;
 
                /* Exponential lifetime */
                if (sscanf(lifetime_val, "%30u", &n_lifetime) != 1) {
                    ast_log(LOG_NOTICE, "Failed to parse lifetime value in crypto attribute: %s\n", attr);
                    continue;
                }
 
                if (n_lifetime > 48) {
                    /* Yeah... that's a bit big. */
                    ast_log(LOG_NOTICE, "Crypto lifetime exponent of '%u' is a bit large; using 48\n", n_lifetime);
                    n_lifetime = 48;
                }
                sdes_lifetime = pow(2, n_lifetime);
            } else {
                /* Decimal lifetime */
                if (sscanf(lifetime, "%30u", &n_lifetime) != 1) {
                    ast_log(LOG_NOTICE, "Failed to parse lifetime value in crypto attribute: %s\n", attr);
                    continue;
                }
                sdes_lifetime = n_lifetime;
            }
 
            /* Accept anything above ~5.8 hours. Less than ~5.8; reject. */
            if (sdes_lifetime < 1048576) {
                ast_log(LOG_NOTICE, "Rejecting crypto attribute '%s': lifetime '%f' too short\n", attr, sdes_lifetime);
                continue;
            }
        }
 
        ast_debug(2, "Crypto attribute '%s' accepted with lifetime '%f', MKI '%s'\n",
            attr, sdes_lifetime, mki ? mki : "-");
 
        found = 1;
        break;
    }
 
    if (!found) {
        ast_log(LOG_NOTICE, "SRTP crypto offer not acceptable: '%s'\n", attr);
        return -1;
    }
 
    key_len_from_sdp = ast_base64decode(remote_key, key_salt, sizeof(remote_key));
    if (key_len_from_sdp != key_len_expected) {
        ast_log(LOG_WARNING, "SRTP descriptions key length is '%d', not '%d'\n",
            key_len_from_sdp, key_len_expected);
        return -1;
    }
 
    /* on default, the key is 30 (AES-128); throw that away (only) when the suite changed actually */
    /* ingress: optional, but saves one expensive call to get_random(.) */
    /*  egress: required, because the local key was communicated before the remote key is processed */
    if (crypto->key_len != key_len_from_sdp) {
        if (!crypto_init_keys(crypto, key_len_from_sdp)) {
            return -1;
        }
    } else if (!memcmp(crypto->remote_key, remote_key, key_len_from_sdp)) {
        ast_debug(1, "SRTP remote key unchanged; maintaining current policy\n");
        return 0;
    }
 
    if (key_len_from_sdp > sizeof(crypto->remote_key)) {
        ast_log(LOG_ERROR,
            "SRTP key buffer is %zu although it must be at least %d bytes\n",
            sizeof(crypto->remote_key), key_len_from_sdp);
        return -1;
    }
    memcpy(crypto->remote_key, remote_key, key_len_from_sdp);
 
    if (crypto_activate(crypto, suite_val, remote_key, key_len_from_sdp, rtp) < 0) {
        return -1;
    }
 
    if (ast_test_flag(srtp, AST_SRTP_CRYPTO_TAG_32)) {
        taglen = 32;
    } else if (ast_test_flag(srtp, AST_SRTP_CRYPTO_TAG_16)) {
        taglen = 16;
    } else if (ast_test_flag(srtp, AST_SRTP_CRYPTO_TAG_8)) {
        taglen = 8;
    } else {
        taglen = 80;
    }
    if (ast_test_flag(srtp, AST_SRTP_CRYPTO_AES_256)) {
        taglen |= 0x0200;
    } else if (ast_test_flag(srtp, AST_SRTP_CRYPTO_AES_192)) {
        taglen |= 0x0100;
    }
    if (ast_test_flag(srtp, AST_SRTP_CRYPTO_OLD_NAME)) {
        taglen |= 0x0080;
    }
 
    /* Finally, rebuild the crypto line */
    if (res_sdp_crypto_build_offer(crypto, taglen)) {
        return -1;
    }
 
    ast_set_flag(srtp, AST_SRTP_CRYPTO_OFFER_OK);
    return 0;
}

References AES_128_GCM_KEYSIZE_WSALT, AES_256_GCM_KEYSIZE_WSALT, AST_AES_CM_128_HMAC_SHA1_32, AST_AES_CM_128_HMAC_SHA1_80, AST_AES_CM_192_HMAC_SHA1_32, AST_AES_CM_192_HMAC_SHA1_80, AST_AES_CM_256_HMAC_SHA1_32, AST_AES_CM_256_HMAC_SHA1_80, AST_AES_GCM_128, AST_AES_GCM_128_8, AST_AES_GCM_256, AST_AES_GCM_256_8, ast_base64decode(), ast_clear_flag, ast_debug, AST_LIST_NEXT, ast_log, ast_set_flag, AST_SRTP_CRYPTO_AES_192, AST_SRTP_CRYPTO_AES_256, AST_SRTP_CRYPTO_OFFER_OK, AST_SRTP_CRYPTO_OLD_NAME, AST_SRTP_CRYPTO_TAG_16, AST_SRTP_CRYPTO_TAG_32, AST_SRTP_CRYPTO_TAG_8, AST_SRTP_CRYPTO_TAG_80, ast_strdupa, ast_strlen_zero(), ast_test_flag, ast_sdp_srtp::crypto, crypto_activate(), crypto_init_keys(), ast_sdp_srtp::flags, sip_to_pjsip::info(), ast_sdp_crypto::key_len, LOG_ERROR, LOG_NOTICE, LOG_WARNING, method, NULL, ast_sdp_crypto::remote_key, res_sdp_crypto_build_offer(), ast_sdp_srtp::sdp_srtp_list, str, strsep(), and ast_sdp_crypto::tag.

◆ res_sdp_srtp_get_attr()

static const char * res_sdp_srtp_get_attr	(	struct ast_sdp_srtp *	srtp,
		int	dtls_enabled,
		int	default_taglen_32
	)

static

Definition at line 1127 of file res_srtp.c.

{
    int taglen;
 
    if (!srtp) {
        return NULL;
    }
 
    /* Set encryption properties */
    if (!srtp->crypto) {
        if (AST_LIST_NEXT(srtp, sdp_srtp_list)) {
            srtp->crypto = res_sdp_crypto_alloc();
            ast_log(LOG_ERROR, "SRTP SDP list was not empty\n");
        } else {
            const int len = default_taglen_32 ? AST_SRTP_CRYPTO_TAG_32 : AST_SRTP_CRYPTO_TAG_80;
            const int attr[][3] = {
            /* This array creates the following list:
             * a=crypto:1 AES_CM_128_HMAC_SHA1_ ...
             * a=crypto:2 AEAD_AES_128_GCM ...
             * a=crypto:3 AES_256_CM_HMAC_SHA1_ ...
             * a=crypto:4 AEAD_AES_256_GCM ...
             * a=crypto:5 AES_192_CM_HMAC_SHA1_ ...
             * something like 'AEAD_AES_192_GCM' is not specified by the RFCs
             *
             * If you want to prefer another crypto suite or you want to
             * exclude a suite, change this array and recompile Asterisk.
             * This list cannot be changed from rtp.conf because you should
             * know what you are doing. Especially AES-192 and AES-GCM are
             * broken in many VoIP clients, see
             * https://github.com/cisco/libsrtp/pull/170
             * https://github.com/cisco/libsrtp/pull/184
             * Furthermore, AES-GCM uses a shorter crypto-suite string which
             * causes Nokia phones based on Symbian/S60 to reject the whole
             * INVITE with status 500, even if a matching suite was offered.
             * AES-256 might just waste your processor cycles, especially if
             * your TLS transport is not secured with equivalent grade, see
             * https://security.stackexchange.com/q/61361
             * Therefore, AES-128 was preferred here.
             *
             * If you want to enable one of those defines, please, go for
             * CFLAGS='-DENABLE_SRTP_AES_GCM' ./configure && sudo make install
             */
                { len, 0, 30 },
#if defined(HAVE_SRTP_GCM) && defined(ENABLE_SRTP_AES_GCM)
                { AST_SRTP_CRYPTO_TAG_16, 0, AES_128_GCM_KEYSIZE_WSALT },
#endif
#if defined(HAVE_SRTP_256) && defined(ENABLE_SRTP_AES_256)
                { len, AST_SRTP_CRYPTO_AES_256, 46 },
#endif
#if defined(HAVE_SRTP_GCM) && defined(ENABLE_SRTP_AES_GCM) && defined(ENABLE_SRTP_AES_256)
                { AST_SRTP_CRYPTO_TAG_16, AST_SRTP_CRYPTO_AES_256, AES_256_GCM_KEYSIZE_WSALT },
#endif
#if defined(HAVE_SRTP_192) && defined(ENABLE_SRTP_AES_192)
                { len, AST_SRTP_CRYPTO_AES_192, 38 },
#endif
            };
            struct ast_sdp_srtp *tmp = srtp;
            int i;
 
            for (i = 0; i < ARRAY_LEN(attr); i++) {
                if (attr[i][0]) {
                    ast_set_flag(tmp, attr[i][0]);
                }
                if (attr[i][1]) {
                    ast_set_flag(tmp, attr[i][1]);
                }
                tmp->crypto = sdp_crypto_alloc(attr[i][2]); /* key_len */
                tmp->crypto->tag = (i + 1); /* tag starts at 1 */
 
                if (i < ARRAY_LEN(attr) - 1) {
                    AST_LIST_NEXT(tmp, sdp_srtp_list) = ast_sdp_srtp_alloc();
                    tmp = AST_LIST_NEXT(tmp, sdp_srtp_list);
                }
            }
        }
    }
 
    if (dtls_enabled) {
        /* If DTLS-SRTP is enabled the key details will be pulled from TLS */
        return NULL;
    }
 
    /* set the key length based on INVITE or settings */
    if (ast_test_flag(srtp, AST_SRTP_CRYPTO_TAG_80)) {
        taglen = 80;
    } else if (ast_test_flag(srtp, AST_SRTP_CRYPTO_TAG_32)) {
        taglen = 32;
    } else if (ast_test_flag(srtp, AST_SRTP_CRYPTO_TAG_16)) {
        taglen = 16;
    } else if (ast_test_flag(srtp, AST_SRTP_CRYPTO_TAG_8)) {
        taglen = 8;
    } else {
        taglen = default_taglen_32 ? 32 : 80;
    }
    if (ast_test_flag(srtp, AST_SRTP_CRYPTO_AES_256)) {
        taglen |= 0x0200;
    } else if (ast_test_flag(srtp, AST_SRTP_CRYPTO_AES_192)) {
        taglen |= 0x0100;
    }
    if (ast_test_flag(srtp, AST_SRTP_CRYPTO_OLD_NAME)) {
        taglen |= 0x0080;
    }
 
    if (srtp->crypto && (res_sdp_crypto_build_offer(srtp->crypto, taglen) >= 0)) {
        return srtp->crypto->a_crypto;
    }
 
    ast_log(LOG_WARNING, "No SRTP key management enabled\n");
    return NULL;
}

References ast_sdp_crypto::a_crypto, AES_128_GCM_KEYSIZE_WSALT, AES_256_GCM_KEYSIZE_WSALT, ARRAY_LEN, AST_LIST_NEXT, ast_log, ast_sdp_srtp_alloc(), ast_set_flag, AST_SRTP_CRYPTO_AES_192, AST_SRTP_CRYPTO_AES_256, AST_SRTP_CRYPTO_OLD_NAME, AST_SRTP_CRYPTO_TAG_16, AST_SRTP_CRYPTO_TAG_32, AST_SRTP_CRYPTO_TAG_8, AST_SRTP_CRYPTO_TAG_80, ast_test_flag, ast_sdp_srtp::crypto, len(), LOG_ERROR, LOG_WARNING, NULL, res_sdp_crypto_alloc(), res_sdp_crypto_build_offer(), sdp_crypto_alloc(), ast_sdp_srtp::sdp_srtp_list, and ast_sdp_crypto::tag.

◆ res_srtp_init()

static int res_srtp_init ( void )

static

Definition at line 1257 of file res_srtp.c.

{
    if (g_initialized) {
        return 0;
    }
 
    if (srtp_init() != err_status_ok) {
        ast_log(AST_LOG_WARNING, "Failed to initialize libsrtp\n");
        return -1;
    }
 
    srtp_install_event_handler(srtp_event_cb);
 
    if (ast_rtp_engine_register_srtp(&srtp_res, &policy_res)) {
        ast_log(AST_LOG_WARNING, "Failed to register SRTP with rtp engine\n");
        res_srtp_shutdown();
        return -1;
    }
 
    if (ast_sdp_crypto_register(&res_sdp_crypto_api)) {
        ast_log(AST_LOG_WARNING, "Failed to register SDP SRTP crypto API\n");
        res_srtp_shutdown();
        return -1;
    }
 
#ifdef HAVE_SRTP_GET_VERSION
    ast_verb(2, "%s initialized\n", srtp_get_version_string());
#else
    ast_verb(2, "libsrtp initialized\n");
#endif
 
    g_initialized = 1;
    return 0;
}

References ast_log, AST_LOG_WARNING, ast_rtp_engine_register_srtp(), ast_sdp_crypto_register(), ast_verb, err_status_ok, g_initialized, policy_res, res_sdp_crypto_api, res_srtp_shutdown(), srtp_event_cb(), and srtp_res.

Referenced by load_module().

◆ res_srtp_new()

static struct ast_srtp * res_srtp_new ( void )

static

Definition at line 215 of file res_srtp.c.

{
    struct ast_srtp *srtp;
 
    if (!(srtp = ast_calloc(1, sizeof(*srtp)))) {
        ast_log(LOG_ERROR, "Unable to allocate memory for srtp\n");
        return NULL;
    }
 
    srtp->policies = ao2_t_container_alloc_hash(AO2_ALLOC_OPT_LOCK_MUTEX, 0, 5,
        policy_hash_fn, NULL, policy_cmp_fn, "SRTP policy container");
    if (!srtp->policies) {
        ast_free(srtp);
        return NULL;
    }
 
    srtp->warned = 1;
 
    return srtp;
}

References AO2_ALLOC_OPT_LOCK_MUTEX, ao2_t_container_alloc_hash, ast_calloc, ast_free, ast_log, LOG_ERROR, NULL, ast_srtp::policies, policy_cmp_fn(), policy_hash_fn(), and ast_srtp::warned.

Referenced by ast_srtp_create().

◆ res_srtp_shutdown()

static void res_srtp_shutdown ( void )

static

Definition at line 1246 of file res_srtp.c.

{
    ast_sdp_crypto_unregister(&res_sdp_crypto_api);
    ast_rtp_engine_unregister_srtp();
    srtp_install_event_handler(NULL);
#ifdef HAVE_SRTP_SHUTDOWN
    srtp_shutdown();
#endif
    g_initialized = 0;
}

References ast_rtp_engine_unregister_srtp(), ast_sdp_crypto_unregister(), g_initialized, NULL, and res_sdp_crypto_api.

Referenced by res_srtp_init(), and unload_module().

◆ sdp_crypto_alloc()

static struct ast_sdp_crypto * sdp_crypto_alloc ( const int key_len )

static

Definition at line 707 of file res_srtp.c.

{
    struct ast_sdp_crypto *p, *result;
 
    if (!(p = ast_calloc(1, sizeof(*p)))) {
        return NULL;
    }
    p->tag = 1;
    ast_module_ref(ast_module_info->self);
 
    /* default is a key which uses AST_AES_CM_128_HMAC_SHA1_xx */
    result = crypto_init_keys(p, key_len);
    if (!result) {
        res_sdp_crypto_dtor(p);
    }
 
    return result;
}

References ast_calloc, ast_module_ref, crypto_init_keys(), ast_sdp_crypto::key_len, NULL, res_sdp_crypto_dtor(), result, ast_module_info::self, and ast_sdp_crypto::tag.

Referenced by res_sdp_crypto_alloc(), and res_sdp_srtp_get_attr().

◆ set_crypto_policy()

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
	)

static

Definition at line 762 of file res_srtp.c.

{
    if (policy_res.set_master_key(policy, master_key, key_len, NULL, 0) < 0) {
        return -1;
    }
 
    if (policy_res.set_suite(policy, suite_val)) {
        ast_log(LOG_WARNING, "Could not set remote SRTP suite\n");
        return -1;
    }
 
    policy_res.set_ssrc(policy, ssrc, inbound);
 
    return 0;
}

References ast_log, ast_sdp_crypto::key_len, LOG_WARNING, NULL, policy_res, ast_srtp_policy_res::set_master_key, ast_srtp_policy_res::set_ssrc, and ast_srtp_policy_res::set_suite.

Referenced by crypto_activate().

◆ srtp_errstr()

static const char * srtp_errstr ( int err )

static

Definition at line 149 of file res_srtp.c.

{
    switch(err) {
    case err_status_ok:
        return "nothing to report";
    case err_status_fail:
        return "unspecified failure";
    case err_status_bad_param:
        return "unsupported parameter";
    case err_status_alloc_fail:
        return "couldn't allocate memory";
    case err_status_dealloc_fail:
        return "couldn't deallocate properly";
    case err_status_init_fail:
        return "couldn't initialize";
    case err_status_terminus:
        return "can't process as much data as requested";
    case err_status_auth_fail:
        return "authentication failure";
    case err_status_cipher_fail:
        return "cipher failure";
    case err_status_replay_fail:
        return "replay check failed (bad index)";
    case err_status_replay_old:
        return "replay check failed (index too old)";
    case err_status_algo_fail:
        return "algorithm failed test routine";
    case err_status_no_such_op:
        return "unsupported operation";
    case err_status_no_ctx:
        return "no appropriate context found";
    case err_status_cant_check:
        return "unable to perform desired validation";
    case err_status_key_expired:
        return "can't use key any more";
    default:
        return "unknown";
    }
}

References err_status_algo_fail, err_status_alloc_fail, err_status_auth_fail, err_status_bad_param, err_status_cant_check, err_status_cipher_fail, err_status_dealloc_fail, err_status_fail, err_status_init_fail, err_status_key_expired, err_status_no_ctx, err_status_no_such_op, err_status_ok, err_status_replay_fail, err_status_replay_old, and err_status_terminus.

Referenced by ast_srtp_create(), ast_srtp_protect(), and ast_srtp_unprotect().

◆ srtp_event_cb()

static void srtp_event_cb ( srtp_event_data_t * data )

static

Definition at line 239 of file res_srtp.c.

{
    switch (data->event) {
    case event_ssrc_collision:
        ast_debug(1, "SSRC collision\n");
        break;
    case event_key_soft_limit:
        ast_debug(1, "event_key_soft_limit\n");
        break;
    case event_key_hard_limit:
        ast_debug(1, "event_key_hard_limit\n");
        break;
    case event_packet_index_limit:
        ast_debug(1, "event_packet_index_limit\n");
        break;
    }
}

References ast_debug, and ast_srtp::data.

Referenced by res_srtp_init().

◆ unload_module()

static int unload_module ( void )

static

Definition at line 1301 of file res_srtp.c.

{
    res_srtp_shutdown();
    return 0;
}

References res_srtp_shutdown().

Variable Documentation

◆ __mod_info

struct ast_module_info __mod_info = { .name = AST_MODULE, .flags = AST_MODFLAG_GLOBAL_SYMBOLS | AST_MODFLAG_LOAD_ORDER , .description = "Secure RTP (SRTP)" , .key = "This paragraph is copyright (c) 2006 by Digium, Inc. \In order for your module to load, it must return this \key via a function called \"key\". Any code which \includes this paragraph must be licensed under the GNU \General Public License version 2 or later (at your \option). In addition to Digium's general reservations \of rights, Digium expressly reserves the right to \allow other parties to license this paragraph under \different terms. Any use of Digium, Inc. trademarks or \logos (including \"Asterisk\" or \"Digium\") without \express written permission of Digium, Inc. is prohibited.\n" , .buildopt_sum = AST_BUILDOPT_SUM, .support_level = AST_MODULE_SUPPORT_CORE, .load = load_module, .unload = unload_module, .load_pri = AST_MODPRI_CHANNEL_DEPEND, }

static

Definition at line 1312 of file res_srtp.c.

◆ ast_module_info

const struct ast_module_info* ast_module_info = &__mod_info

static

Definition at line 1312 of file res_srtp.c.

◆ g_initialized

int g_initialized = 0

static

Tracks whether or not we've initialized the libsrtp library

Definition at line 108 of file res_srtp.c.

Referenced by res_srtp_init(), and res_srtp_shutdown().

◆ policy_res

struct ast_srtp_policy_res policy_res

static

Definition at line 141 of file res_srtp.c.

Referenced by ast_rtp_engine_register_srtp(), crypto_activate(), res_srtp_init(), and set_crypto_policy().

◆ res_sdp_crypto_api

struct ast_sdp_crypto_api res_sdp_crypto_api

static

Definition at line 1238 of file res_srtp.c.

Referenced by res_srtp_init(), and res_srtp_shutdown().

◆ srtp_res

struct ast_srtp_res srtp_res

static

Definition at line 129 of file res_srtp.c.

Referenced by ast_rtp_engine_register_srtp(), crypto_init_keys(), and res_srtp_init().

Data Structures

Functions

Variables

Detailed Description

Function Documentation

◆ __reg_module()

◆ __unreg_module()

◆ AST_MODULE_SELF_SYM()

◆ ast_srtp_add_stream()

◆ ast_srtp_change_source()

◆ ast_srtp_create()

◆ ast_srtp_destroy()

◆ ast_srtp_get_random()

◆ ast_srtp_policy_alloc()

◆ ast_srtp_policy_destroy()

◆ ast_srtp_policy_set_master_key()

◆ ast_srtp_policy_set_ssrc()

◆ ast_srtp_policy_set_suite()

◆ ast_srtp_protect()

◆ ast_srtp_replace()

◆ ast_srtp_set_cb()

◆ ast_srtp_unprotect()

◆ crypto_activate()

◆ crypto_init_keys()

◆ find_policy()

◆ load_module()

◆ policy_cmp_fn()

◆ policy_destructor()

◆ policy_hash_fn()

◆ policy_set_suite()

◆ res_sdp_crypto_alloc()

◆ res_sdp_crypto_build_offer()

◆ res_sdp_crypto_dtor()

◆ res_sdp_crypto_parse_offer()

◆ res_sdp_srtp_get_attr()

◆ res_srtp_init()

◆ res_srtp_new()

◆ res_srtp_shutdown()

◆ sdp_crypto_alloc()

◆ set_crypto_policy()

◆ srtp_errstr()

◆ srtp_event_cb()

◆ unload_module()

Variable Documentation

◆ __mod_info

◆ ast_module_info

◆ g_initialized

◆ policy_res

◆ res_sdp_crypto_api

◆ srtp_res