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/* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
/* vim: set et sw=2 ts=2: */
/***************************************************************************
* srtp.cc
*
* Thu Sep 5 10:46:10 CEST 2013
* Copyright 2013 Bent Bisballe Nyeng
* deva@aasimon.org
****************************************************************************/
/*
* This file is part of lrtp.
*
* lrtp is free software; you can redistribute it and/or
* modify it under the terms of the GNU Lesser General Public
* License as published by the Free Software Foundation; either
* version 2.1 of the License, or (at your option) any later version.
*
* lrtp is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
* Lesser General Public License for more details.
*
* You should have received a copy of the GNU Lesser General Public
* License along with lrtp; if not, write to the Free Software
* Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
*/
#include "srtp.h"
#ifdef WIN32
#include <srtp.h>
#else
#include <srtp/srtp.h>
#endif
#include "asc2bin.h"
// Global SRTP instance status
static err_status_t active_srtp_instance_status = err_status_init_fail;
// This macro translates srtp status codes into exceptions:
#define SRTP_THROW(s) \
do { \
switch(s) { \
case err_status_fail: throw LRTP_SRTP_FAIL; \
case err_status_bad_param: throw LRTP_SRTP_BAD_PARAM; \
case err_status_alloc_fail: throw LRTP_SRTP_ALLOC_FAIL; \
case err_status_dealloc_fail: throw LRTP_SRTP_DEALLOC_FAIL; \
case err_status_init_fail: throw LRTP_SRTP_INIT_FAIL; \
case err_status_terminus: throw LRTP_SRTP_TERMINUS; \
case err_status_auth_fail: throw LRTP_SRTP_AUTH_FAIL; \
case err_status_cipher_fail: throw LRTP_SRTP_CIPHER_FAIL; \
case err_status_replay_fail: throw LRTP_SRTP_REPLAY_FAIL; \
case err_status_replay_old: throw LRTP_SRTP_REPLAY_OLD; \
case err_status_algo_fail: throw LRTP_SRTP_ALGO_FAIL; \
case err_status_no_such_op: throw LRTP_SRTP_NO_SUCH_OP; \
case err_status_no_ctx: throw LRTP_SRTP_NO_CTX; \
case err_status_cant_check: throw LRTP_SRTP_CANT_CHECK; \
case err_status_key_expired: throw LRTP_SRTP_KEY_EXPIRED; \
case err_status_socket_err: throw LRTP_SRTP_SOCKET_ERR; \
case err_status_signal_err: throw LRTP_SRTP_SIGNAL_ERR; \
case err_status_nonce_bad: throw LRTP_SRTP_NONCE_BAD; \
case err_status_read_fail: throw LRTP_SRTP_READ_FAIL; \
case err_status_write_fail: throw LRTP_SRTP_WRITE_FAIL; \
case err_status_parse_err: throw LRTP_SRTP_PARSE_ERR; \
case err_status_encode_err: throw LRTP_SRTP_ENCODE_ERR; \
case err_status_semaphore_err: throw LRTP_SRTP_SEMAPHORE_ERR; \
case err_status_pfkey_err: throw LRTP_SRTP_PFKEY_ERR; \
default: throw LRTP_SRTP_FAIL; \
} \
} while(0)
struct SRTP::prv {
char *key;
size_t key_len;
unsigned int ssrc;
srtp_t session;
srtp_policy_t policy;
};
SRTP::SRTP(std::string key, unsigned int ssrc)
_throw(enum lrtp_status_t)
{
if(active_srtp_instance_status != err_status_ok) {
SRTP_THROW(active_srtp_instance_status);
}
prv = NULL;
err_status_t status;
prv = new struct prv;
if(!prv) throw LRTP_OUT_OF_MEMORY;
prv->ssrc = ssrc;
try {
setupKey(key);
setupPolicy(true, true);
} catch(enum lrtp_status_t s) {
throw s;
}
status = srtp_create(&prv->session, &prv->policy);
if(status != err_status_ok) SRTP_THROW(status);
status = srtp_add_stream(prv->session, &prv->policy);
if(status != err_status_ok) SRTP_THROW(status);
}
SRTP::~SRTP()
{
err_status_t status = srtp_remove_stream(prv->session, htonl(prv->ssrc));
if(status != err_status_ok) SRTP_THROW(status);
status = srtp_dealloc(prv->session);
if(status != err_status_ok) SRTP_THROW(status);
if(prv) {
free(prv->key);
delete prv;
}
}
void SRTP::setupKey(const std::string &key)
_throw(enum lrtp_status_t)
{
prv->key = (char *)calloc(MASTER_KEY_LEN, 1);
prv->key_len = MASTER_KEY_LEN;
if(key.length() > MASTER_KEY_LEN * 2) throw LRTP_KEY_TOO_LONG;
// Read key from hexadecimal on command line into an octet string
ssize_t len = asc2bin(prv->key, prv->key_len, key.c_str(), key.size());
if(len == -1) throw LRTP_INVALID_KEY_STRING;
prv->key_len = len;
// check that hex string is the right length.
if(len < MASTER_KEY_LEN) throw LRTP_KEY_TOO_SHORT;
}
void SRTP::setupPolicy(bool confidentiality, bool authentication)
_throw(enum lrtp_status_t)
{
#ifndef USE_CRYPTO
confidentiality = authentication = false;
// printf("No crypto!\n");
#endif
// Apparently not all fields in prv->policy are set during initialisation.
memset(&prv->policy, 0, sizeof(srtp_policy_t));
/*
* create policy structure, using the default mechanisms but
* with only the security services requested on the command line,
* using the right SSRC value
*/
if(confidentiality && authentication) {
crypto_policy_set_aes_cm_128_hmac_sha1_80(&prv->policy.rtp);
prv->policy.rtp.sec_serv = sec_serv_conf_and_auth;
} else if(confidentiality && !authentication) {
crypto_policy_set_aes_cm_128_null_auth(&prv->policy.rtp);
prv->policy.rtp.sec_serv = sec_serv_conf;
} else if(!confidentiality && authentication) {
crypto_policy_set_null_cipher_hmac_sha1_80(&prv->policy.rtp);
prv->policy.rtp.sec_serv = sec_serv_auth;
} else {
/*
* we're not providing security services, so set the policy to the
* null policy
*
* Note that this policy does not conform to the SRTP
* specification, since RTCP authentication is required. However,
* the effect of this policy is to turn off SRTP, so that this
* application is now a vanilla-flavored RTP application.
*/
prv->policy.rtp.cipher_type = NULL_CIPHER;
prv->policy.rtp.cipher_key_len = 0;
prv->policy.rtp.auth_type = NULL_AUTH;
prv->policy.rtp.auth_key_len = 0;
prv->policy.rtp.auth_tag_len = 0;
prv->policy.rtp.sec_serv = sec_serv_none;
}
crypto_policy_set_rtcp_default(&prv->policy.rtcp);
prv->policy.rtcp.sec_serv = sec_serv_none; // No need for RTCP
prv->policy.key = (uint8_t *)prv->key;
prv->policy.ssrc.type = ssrc_specific;
prv->policy.ssrc.value = prv->ssrc;
prv->policy.next = NULL;
}
int SRTP::encrypt(char *packet, size_t size)
_throw(enum lrtp_status_t)
{
int sz = size;
err_status_t status = srtp_protect(prv->session, packet, &sz);
if(status != err_status_ok) SRTP_THROW(status);
return sz;
}
int SRTP::decrypt(char *packet, size_t size)
_throw(enum lrtp_status_t)
{
int sz = size;
err_status_t status = srtp_unprotect(prv->session, packet, &sz);
if(status != err_status_ok) SRTP_THROW(status);
return sz;
}
class SRTPInstance {
public:
SRTPInstance();
~SRTPInstance();
};
SRTPInstance::SRTPInstance()
{
// printf("SRTP init\n");
active_srtp_instance_status = srtp_init();
}
SRTPInstance::~SRTPInstance()
{
// printf("SRTP shutdown\n");
if(active_srtp_instance_status == err_status_ok) {
active_srtp_instance_status = srtp_shutdown();
//if(status != err_status_ok) Nothing we can do here really...
}
// Mark SRTP instance as 'shut down'
active_srtp_instance_status = err_status_init_fail;
}
// One global instance.
SRTPInstance instance;
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