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 = ASTERISK_GPL_KEY , .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, ast_srtp_policy::sp, 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, 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 = ASTERISK_GPL_KEY , .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.

                                               {
    .alloc = ast_srtp_policy_alloc,
    .destroy = ast_srtp_policy_destroy,
    .set_suite = ast_srtp_policy_set_suite,
    .set_master_key = ast_srtp_policy_set_master_key,
    .set_ssrc = ast_srtp_policy_set_ssrc
};

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.

                                                      {
    .dtor = res_sdp_crypto_dtor,
    .alloc = res_sdp_crypto_alloc,
    .build_offer = res_sdp_crypto_build_offer,
    .parse_offer = res_sdp_crypto_parse_offer,
    .get_attr = res_sdp_srtp_get_attr,
};

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.

                                      {
    .create = ast_srtp_create,
    .replace = ast_srtp_replace,
    .destroy = ast_srtp_destroy,
    .add_stream = ast_srtp_add_stream,
    .change_source = ast_srtp_change_source,
    .set_cb = ast_srtp_set_cb,
    .unprotect = ast_srtp_unprotect,
    .protect = ast_srtp_protect,
    .get_random = ast_srtp_get_random
};

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