Move srtp from ortp to mediastreamer2

CMakeLists.txt

@@ -59,6 +59,7 @@ option(ENABLE_STATIC "Build static library (default is shared library)." NO)
 option(ENABLE_DEBUG_LOGS "Enable the display of traces showing the execution of the library." NO)
 option(ENABLE_FIXED_POINT "Turn on fixed point computations." ${ENABLE_FIXED_POINT_DEFAULT_VALUE})
 option(ENABLE_RELATIVE_PREFIX "Find resources relatively to the installation directory." NO)
+option(ENABLE_SRTP "Build with the SRTP transport support." YES)
 option(ENABLE_ZRTP "Build with ZRTP support." YES)
 
 option(ENABLE_SOUND "Can be used to turn off all possible sound backends." YES)
@@ -89,6 +90,14 @@ cmake_dependent_option(ENABLE_VPX "Build mediastreamer2 with VPX codec." YES "EN
 list(APPEND CMAKE_MODULE_PATH ${CMAKE_PREFIX_PATH}/share/cmake/Modules)
 list(APPEND CMAKE_MODULE_PATH ${CMAKE_CURRENT_SOURCE_DIR}/cmake)
 
+if(ENABLE_SRTP)
+	find_package(SRTP)
+	if(NOT SRTP_FOUND)
+		message(WARNING "Could not find SRTP library, Mediastreamer2 will be compiled without SRTP support.")
+		set(ENABLE_SRTP OFF CACHE BOOL "Build with the SRTP transport support." FORCE)
+	endif()
+endif()
+
 include(CheckIncludeFile)
 include(CheckLibraryExists)
 
@@ -244,6 +253,10 @@ include_directories(
 if(ENABLE_VIDEO)
 	include_directories(src/voip)
 endif()
+if(SRTP_FOUND)
+	include_directories(${SRTP_INCLUDE_DIRS})
+endif()
+
 if(BZRTP_FOUND)
 	include_directories(${BZRTP_INCLUDE_DIRS})
 endif()
@@ -300,6 +313,9 @@ endif()
 if(ENABLE_FIXED_POINT)
 	set(MS_FIXED_POINT 1)
 endif()
+if(SRTP_FOUND)
+	set(HAVE_SRTP 1)
+endif()
 if(ENABLE_ALSA)
 	set(__ALSA_ENABLED__ 1)
 endif()

configure.ac

@@ -1005,6 +1005,66 @@ case "$target_os" in
 	;;
 esac
 
+dnl check for libsrtp support (secure rtp)
+AC_ARG_WITH(srtp,
+	AC_HELP_STRING([--with-srtp], [Set prefix where libsrtp can be found or "none" to disable (ex:/usr or /usr/local) [[default=/usr]]]),
+	[srtp_prefix=$withval],
+	[srtp_prefix=/usr]
+)
+if test "${srtp_prefix}" != "none" ; then
+	if test "${srtp_prefix}" != "/usr" || test "$mingw_found" = "yes" ; then
+		SRTP_CFLAGS="-I${srtp_prefix}/include -I${srtp_prefix}/include/srtp"
+		SRTP_LIBS="-L${srtp_prefix}/lib"
+	fi
+	SRTP_LIBS="$SRTP_LIBS -lsrtp"
+
+	dnl check srtp headers
+	have_srtp=no
+	CPPFLAGS_save=$CPPFLAGS
+	CPPFLAGS="$CPPFLAGS $SRTP_CFLAGS"
+	AC_CHECK_HEADER([srtp/srtp.h],have_srtp_headers=yes)
+	CPPFLAGS=$CPPFLAGS_save
+
+	dnl check for srtp lib
+	LDFLAGS_save=$LDFLAGS
+	LDFLAGS="$LDFLAGS $SRTP_LIBS"
+	LIBS_save=$LIBS
+	AC_CHECK_LIB(srtp,srtp_init,have_srtp_lib=yes)
+	AC_CHECK_LIB(srtp,srtp_shutdown,[AC_DEFINE([HAVE_SRTP_SHUTDOWN],1,[Defined when srtp_shutdown() exists.])])
+	LDFLAGS=$LDFLAGS_save
+	LIBS=$LIBS_save
+
+	if test "$have_srtp_headers$have_srtp_lib" = "yesyes" ; then
+		have_srtp=yes
+		if test "$test_for_broken_srtp" = yes; then
+			LDFLAGS_save=$LDFLAGS
+			LDFLAGS="$LDFLAGS $SRTP_LIBS"
+			LIBS_save=$LIBS
+			AC_CHECK_LIB(srtp,sha1_update,[
+			AC_MSG_ERROR([This libsrtp version exports symbols conflicting with polar ssl, resulting in a bad execution path.
+			 Please use the one from git://git.linphone.org/srtp.git
+			 You could also track resolution of defect on https://github.com/cisco/libsrtp/issues/28
+			 If you are not linking against polar ssl, you may prefer to skip this test with --enable-broken-srtp
+			])], have_srtp=yes)
+			LDFLAGS=$LDFLAGS_save
+			LIBS=$LIBS_save
+		fi
+		AC_DEFINE(HAVE_SRTP, 1, [Defined when srtp support is compiled])
+	else
+		AC_MSG_NOTICE([Could not find libsrtp headers or lib, cryto transport disabled.])
+		SRTP_CFLAGS=
+		SRTP_LIBS=
+	fi
+
+	AC_SUBST(SRTP_CFLAGS)
+	AC_SUBST(SRTP_LIBS)
+else
+	have_srtp=no
+	SRTP_CFLAGS=
+	SRTP_LIBS=
+fi
+
+
 dnl check for libzrtp support (RFC 6189: Media Path Key Agreement for Unicast Secure RTP)
 AC_ARG_ENABLE(zrtp,
 	[AS_HELP_STRING([--enable-zrtp], [Turn on or off compilation of zrtp (default=no)])],

include/mediastreamer2/mediastream.h

@@ -35,6 +35,7 @@ typedef struct srtp_ctx_t *MSSrtpCtx;
 #include <mediastreamer2/qualityindicator.h>
 #include <mediastreamer2/ice.h>
 #include <mediastreamer2/zrtp.h>
+#include <mediastreamer2/ms_srtp.h>
 
 
 #define PAYLOAD_TYPE_FLAG_CAN_RECV	PAYLOAD_TYPE_USER_FLAG_1
@@ -157,9 +158,6 @@ struct _MediaStream {
  * @addtogroup audio_stream_api
  * @{
 **/
-
-MS2_PUBLIC bool_t media_stream_srtp_supported(void);
-
 MS2_PUBLIC void media_stream_set_rtcp_information(MediaStream *stream, const char *cname, const char *tool);
 
 MS2_PUBLIC void media_stream_get_local_rtp_stats(MediaStream *stream, rtp_stats_t *stats);
@@ -177,9 +175,6 @@ MS2_PUBLIC void media_stream_enable_adaptive_jittcomp(MediaStream *stream, bool_
 **/
 MS2_PUBLIC bool_t media_stream_enable_srtp(MediaStream* stream, MSCryptoSuite suite, const char* snd_key, const char* rcv_key);
 
-MS2_PUBLIC int media_stream_set_srtp_recv_key(MediaStream *stream, MSCryptoSuite suite, const char* key, bool_t keyisb64);
-
-MS2_PUBLIC int media_stream_set_srtp_send_key(MediaStream *stream, MSCryptoSuite suite, const char* key, bool_t keyisb64);
 /**
  * @param[in] stream MediaStream object
  * @return true if stream is encrypted

include/mediastreamer2/ms_srtp.h

+/*
+  mediastreamer2 library - modular sound and video processing and streaming
+  Copyright (C) 2006-2014 Belledonne Communications, Grenoble
+
+  This library 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.
+
+  This library 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 this library; if not, write to the Free Software
+  Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
+*/
+
+#ifndef ms_srtp_h
+#define ms_srtp_h
+
+
+#if defined(HAVE_SRTP)
+#if defined(ANDROID) || !WINAPI_FAMILY_PARTITION(WINAPI_PARTITION_DESKTOP)
+// Android and Windows phone don't use make install
+#	include <srtp.h>
+#else
+#	include <srtp/srtp.h>
+#endif /* ANDROID */
+#else /* HAVE_SRTP */
+
+typedef void* srtp_t;
+typedef int err_status_t;
+typedef struct srtp_policy srtp_policy_t;
+
+#endif /* HAVE_SRTP */
+
+/*srtp defines all this stuff*/
+#undef PACKAGE_BUGREPORT
+#undef PACKAGE_NAME
+#undef PACKAGE_STRING
+#undef PACKAGE_TARNAME
+#undef PACKAGE_VERSION
+
+#include <ortp/rtpsession.h>
+#include "mediastreamer2/mscommon.h"
+
+
+
+#ifdef __cplusplus
+extern "C"{
+#endif
+
+/* defined in mediastream.h */
+struct _MediaStream;
+enum _MSCryptoSuite;
+
+/**
+ * Check if SRTP is supported
+ * @return true if SRTP is supported
+ */
+MS2_PUBLIC bool_t ms_srtp_supported(void);
+
+/**
+ * Set srtp receiver key for the given media stream.
+ * If no srtp session exists on the stream it is created, if it already exists srtp policy is created/modified for the receiver side of the stream.
+ *
+ * @param[in/out]	stream	The mediastream to operate on
+ * @param[in]		suite	The srtp crypto suite to use
+ * @param[in]		key	Srtp master key and master salt in a base 64 NULL terminated string
+ * @return	0 on success, error code otherwise
+ */
+MS2_PUBLIC int media_stream_set_srtp_recv_key_b64(struct _MediaStream *stream, enum _MSCryptoSuite suite, const char* key);
+
+/**
+ * Set srtp receiver key for the given media stream.
+ * If no srtp session exists on the stream it is created, if it already exists srtp policy is created/modified for the receiver side of the stream.
+ *
+ * @param[in/out]	stream		The mediastream to operate on
+ * @param[in]		suite		The srtp crypto suite to use
+ * @param[in]		key		Srtp master key and master salt
+ * @param[in]		key_length	key buffer length
+ * @return	0 on success, error code otherwise
+ */
+MS2_PUBLIC int media_stream_set_srtp_recv_key(struct _MediaStream *stream, enum _MSCryptoSuite suite, const char* key, size_t key_length);
+
+/**
+ * Set srtp sender key for the given media stream.
+ * If no srtp session exists on the stream it is created, if it already exists srtp policy is created/modified for the sender side of the stream.
+ *
+ * @param[in/out]	stream	The mediastream to operate on
+ * @param[in]		suite	The srtp crypto suite to use
+ * @param[in]		key	Srtp master key and master salt in a base 64 NULL terminated string
+ * @return	0 on success, error code otherwise
+ */
+MS2_PUBLIC int media_stream_set_srtp_send_key_b64(struct _MediaStream *stream, enum _MSCryptoSuite suite, const char* key);
+
+/**
+ * Set srtp sender key for the given media stream.
+ * If no srtp session exists on the stream it is created, if it already exists srtp policy is created/modified for the sender side of the stream.
+ *
+ * @param[in/out]	stream		The mediastream to operate on
+ * @param[in]		suite		The srtp crypto suite to use
+ * @param[in]		key		Srtp master key and master salt
+ * @param[in]		key_length	key buffer length
+ * @return	0 on success, error code otherwise
+ */
+MS2_PUBLIC int media_stream_set_srtp_send_key(struct _MediaStream *stream, enum _MSCryptoSuite suite, const char* key, size_t key_length);
+
+/**
+ * Deallocate ressources for a srtp session
+ *
+ * @param[in/out] session	SRTP session to be terminated
+ * @return 0 on success
+ */
+MS2_PUBLIC err_status_t ms_srtp_dealloc(srtp_t session);
+#ifdef __cplusplus
+}
+#endif
+
+#endif /* ms_srtp_h */

src/CMakeLists.txt

@@ -25,7 +25,6 @@ if(MSVC)
 	find_library(LIBMINGWEX NAMES mingwex)
 endif()
 
-
 find_program(AWK_PROGRAM awk)
 if(NOT AWK_PROGRAM)
 	message(FATAL_ERROR "You need the awk program to build mediastreamer2.")
@@ -153,6 +152,7 @@ set(VOIP_SOURCE_FILES
 	voip/qualityindicator.c
 	voip/ringstream.c
 	voip/zrtp.c
+	crypto/ms_srtp.c
 )
 
 if(ENABLE_ALSA)
@@ -339,6 +339,9 @@ endif()
 if(BZRTP_FOUND)
 	list(APPEND VOIP_LIBS ${BZRTP_LIBRARIES})
 endif()
+if(SRTP_FOUND)
+	list(APPEND VOIP_LIBS ${SRTP_LIBRARIES})
+endif()
 if(GSM_FOUND)
 	list(APPEND VOIP_LIBS ${GSM_LIBRARIES})
 endif()

src/Makefile.am

@@ -51,7 +51,8 @@ libmediastreamer_voip_la_LIBADD=	libmediastreamer_base.la \
 					$(LIBV4LCONVERT_LIBS) \
 					$(SPANDSP_LIBS) \
 					$(PCAP_LIBS) \
-					$(OPUS_LIBS)
+					$(OPUS_LIBS) \
+					$(SRTP_LIBS)
 
 
 if LIBBZRTP
@@ -98,7 +99,8 @@ libmediastreamer_voip_la_SOURCES+=	voip/private.h \
 					voip/bitratedriver.c \
 					voip/qosanalyzer.c voip/qosanalyzer.h \
 					voip/bitratecontrol.c \
-					voip/zrtp.c
+					voip/zrtp.c \
+					crypto/ms_srtp.c
 else
 libmediastreamer_base_la_SOURCES+=	ortp-deps/logging.c \
 					ortp-deps/port.c \
@@ -384,7 +386,8 @@ AM_CFLAGS=\
 	$(SPANDSP_CFLAGS)  \
 	$(MSSILK_CFLAGS) \
 	$(PCAP_CFLAGS) \
-	$(OPUS_CFLAGS)
+	$(OPUS_CFLAGS) \
+	$(SRTP_FLAGS)
 
 AM_CXXFLAGS=\
 	$(STRICT_OPTIONS) \

src/crypto/ms_srtp.c

+/*
+  mediastreamer2 library - modular sound and video processing and streaming
+  Copyright (C) 2006-2014 Belledonne Communications, Grenoble
+
+  This library 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.
+
+  This library 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 this library; if not, write to the Free Software
+  Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
+*/
+
+#ifdef HAVE_CONFIG_H
+#include "mediastreamer-config.h"
+#endif
+#include "ortp/ortp.h"
+
+#undef PACKAGE_NAME
+#undef PACKAGE_STRING
+#undef PACKAGE_TARNAME
+#undef PACKAGE_VERSION
+
+#include "mediastreamer2/ms_srtp.h"
+#include "mediastreamer2/mediastream.h"
+
+#ifdef HAVE_SRTP
+#if defined(ANDROID) || !WINAPI_FAMILY_PARTITION(WINAPI_PARTITION_DESKTOP)
+// Android and Windows phone don't use make install
+#include <srtp_priv.h>
+#else
+#include <srtp/srtp_priv.h>
+#endif
+
+#include "ortp/b64.h"
+
+#define SRTP_PAD_BYTES (SRTP_MAX_TRAILER_LEN + 4)
+
+/***********************************************/
+/***** LOCAL FUNCTIONS                     *****/
+/***********************************************/
+
+static srtp_stream_ctx_t * find_other_ssrc(srtp_t srtp, uint32_t ssrc){
+	srtp_stream_ctx_t *stream;
+	for (stream=srtp->stream_list;stream!=NULL;stream=stream->next){
+		if (stream->ssrc!=ssrc) return stream;
+	}
+	return stream;
+}
+
+/**** Sender functions ****/
+static int _process_on_send(RtpSession* session,srtp_t srtp,mblk_t *m,bool_t is_rtp){
+	int slen;
+	err_status_t err;
+	rtp_header_t *rtp_header=is_rtp?(rtp_header_t*)m->b_rptr:NULL;
+	rtcp_common_header_t *rtcp_header=!is_rtp?(rtcp_common_header_t*)m->b_rptr:NULL;
+
+	slen=msgdsize(m);
+
+	if (rtp_header && (slen>RTP_FIXED_HEADER_SIZE && rtp_header->version==2)) {
+		/* defragment incoming message and enlarge the buffer for srtp to write its data */
+		msgpullup(m,slen+SRTP_PAD_BYTES);
+		err=srtp_protect(srtp,m->b_rptr,&slen);
+	} else if (rtcp_header && (slen>RTP_FIXED_HEADER_SIZE && rtcp_header->version==2)) {
+		/* defragment incoming message and enlarge the buffer for srtp to write its data */
+		msgpullup(m,slen+SRTP_PAD_BYTES);
+		err=srtp_protect_rtcp(srtp,m->b_rptr,&slen);
+
+	} else {
+		/*ignoring non rtp/rtcp packets*/
+ 		return slen;
+ 	}
+
+	/* check return code from srtp_protect */
+	if (err==err_status_ok){
+		return slen;
+	}
+	ortp_error("srtp_protect%s() failed (%d)", is_rtp?"":"_rtcp", err);
+	return -1;
+}
+
+static int ms_srtp_process_on_send(RtpTransportModifier *t, mblk_t *m){
+	return _process_on_send(t->session,(srtp_t)t->data, m,TRUE);
+}
+static int ms_srtcp_process_on_send(RtpTransportModifier *t, mblk_t *m){
+	return _process_on_send(t->session,(srtp_t)t->data, m,FALSE);
+}
+
+/**** Receiver functions ****/
+/*
+* The ssrc_any_inbound feature of the libsrtp is not working good.
+* It cannot be changed dynamically nor removed.
+* As a result we prefer not to use it, but instead the recv stream is configured with a dummy SSRC value.
+* When the first packet arrives, or when the SSRC changes, then we change the ssrc value inside the srtp stream context,
+* so that the stream that was configured with the dummy SSRC value becomes now fully valid.
+*/
+static void update_recv_stream(RtpSession *session, srtp_t srtp, uint32_t new_ssrc){
+	uint32_t send_ssrc=rtp_session_get_send_ssrc(session);
+	srtp_stream_ctx_t *recvstream=find_other_ssrc(srtp,htonl(send_ssrc));
+	if (recvstream){
+		recvstream->ssrc=new_ssrc;
+	}
+}
+
+static int _process_on_receive(RtpSession* session,srtp_t srtp,mblk_t *m,bool_t is_rtp, int err){
+	int slen;
+	uint32_t new_ssrc;
+	err_status_t srtp_err;
+
+	/* keep NON-RTP data unencrypted */
+	if (is_rtp){
+		rtp_header_t *rtp=(rtp_header_t*)m->b_rptr;
+		if (err<RTP_FIXED_HEADER_SIZE || rtp->version!=2 )
+			return err;
+		new_ssrc=rtp->ssrc;
+	}else{
+		rtcp_common_header_t *rtcp=(rtcp_common_header_t*)m->b_rptr;
+		if (err<(sizeof(rtcp_common_header_t)+4) || rtcp->version!=2 )
+			return err;
+		new_ssrc=*(uint32_t*)(m->b_rptr+sizeof(rtcp_common_header_t));
+	}
+
+	slen=err;
+	srtp_err = is_rtp?srtp_unprotect(srtp,m->b_rptr,&slen):srtp_unprotect_rtcp(srtp,m->b_rptr,&slen);
+	if (srtp_err==err_status_no_ctx) {
+		update_recv_stream(session,srtp,new_ssrc);
+		slen=err;
+		srtp_err = is_rtp?srtp_unprotect(srtp,m->b_rptr,&slen):srtp_unprotect_rtcp(srtp,m->b_rptr,&slen);
+	}
+	if (srtp_err==err_status_ok) {
+		return slen;
+	} else {
+		ms_error("srtp_unprotect%s() failed (%d)", is_rtp?"":"_rtcp", srtp_err);
+		return -1;
+	}
+}
+static int ms_srtp_process_on_receive(RtpTransportModifier *t, mblk_t *m){
+	return _process_on_receive(t->session,(srtp_t)t->data, m,TRUE,msgdsize(m));
+}
+static int ms_srtcp_process_on_receive(RtpTransportModifier *t, mblk_t *m){
+	return _process_on_receive(t->session,(srtp_t)t->data, m,FALSE,msgdsize(m));
+}
+
+
+
+
+/**** Session management functions ****/
+
+/**
+ * deallocate transport modifier ressources
+ * @param[in/out] tp	The transport modifier to be deallocated
+ */
+static void ms_srtp_transport_modifier_destroy(RtpTransportModifier *tp){
+	ms_free(tp);
+}
+
+/**
+ * create a new transport modifier for srtp
+ * @param[in] srtp	the srtp session to be used by the modifier
+ */
+static int ms_srtp_transport_modifier_new(srtp_t srtp, RtpTransportModifier **rtpt, RtpTransportModifier **rtcpt ){
+	if (rtpt) {
+		(*rtpt)=ms_new0(RtpTransportModifier,1);
+		(*rtpt)->data=srtp;
+		(*rtpt)->t_process_on_send=ms_srtp_process_on_send;
+		(*rtpt)->t_process_on_receive=ms_srtp_process_on_receive;
+		(*rtpt)->t_destroy=ms_srtp_transport_modifier_destroy;
+	}
+	if (rtcpt) {
+		(*rtcpt)=ms_new0(RtpTransportModifier,1);
+		(*rtcpt)->data=srtp;
+		(*rtcpt)->t_process_on_send=ms_srtcp_process_on_send;
+		(*rtcpt)->t_process_on_receive=ms_srtcp_process_on_receive;
+		(*rtcpt)->t_destroy=ms_srtp_transport_modifier_destroy;
+	}
+	return 0;
+}
+
+static int ms_check_srtp_session_created(struct _MediaStream *stream){
+	if (stream->sessions.srtp_session==NULL){
+		err_status_t err;
+		srtp_t session;
+		RtpTransport *rtp=NULL,*rtcp=NULL;
+		RtpTransportModifier *rtp_modifier, *rtcp_modifier;
+
+		err = srtp_create(&session, NULL);
+		if (err != 0) {
+			ms_error("Failed to create srtp session (%d)", err);
+			return -1;
+		}
+
+		stream->sessions.srtp_session=session;
+		ms_srtp_transport_modifier_new(session,&rtp_modifier,&rtcp_modifier);
+		rtp_session_get_transports(stream->sessions.rtp_session,&rtp,&rtcp);
+		/*if transports are set, we assume they are meta transporters, otherwise create them*/
+		if (rtp==NULL&&rtcp==NULL){
+			meta_rtp_transport_new(&rtp, TRUE, NULL, 0);
+			meta_rtp_transport_new(&rtcp, FALSE, NULL, 0);
+		}
+		meta_rtp_transport_append_modifier(rtp, rtp_modifier);
+		meta_rtp_transport_append_modifier(rtcp, rtcp_modifier);
+		rtp_session_set_transports(stream->sessions.rtp_session,rtp,rtcp);
+		stream->sessions.is_secured=TRUE;
+	}
+	return 0;
+}
+
+static int ms_add_srtp_stream(srtp_t srtp, MSCryptoSuite suite, uint32_t ssrc, const char* key, size_t key_length, bool_t inbound)
+{
+	srtp_policy_t policy;
+	err_status_t err;
+	ssrc_t ssrc_conf;
+
+	memset(&policy,0,sizeof(policy));
+
+	switch(suite){
+		case MS_AES_128_SHA1_32:
+			crypto_policy_set_aes_cm_128_hmac_sha1_32(&policy.rtp);
+			// srtp doc says: not adapted to rtcp...
+			crypto_policy_set_aes_cm_128_hmac_sha1_32(&policy.rtcp);
+			break;
+		case MS_AES_128_NO_AUTH:
+			crypto_policy_set_aes_cm_128_null_auth(&policy.rtp);
+			// srtp doc says: not adapted to rtcp...
+			crypto_policy_set_aes_cm_128_null_auth(&policy.rtcp);
+			break;
+		case MS_NO_CIPHER_SHA1_80:
+			crypto_policy_set_null_cipher_hmac_sha1_80(&policy.rtp);
+			crypto_policy_set_null_cipher_hmac_sha1_80(&policy.rtcp);
+			break;
+		case MS_AES_128_SHA1_80: /*default mode*/
+			crypto_policy_set_aes_cm_128_hmac_sha1_80(&policy.rtp);
+			crypto_policy_set_aes_cm_128_hmac_sha1_80(&policy.rtcp);
+			break;
+		case MS_AES_256_SHA1_80:
+			crypto_policy_set_aes_cm_256_hmac_sha1_80(&policy.rtp);
+			crypto_policy_set_aes_cm_256_hmac_sha1_80(&policy.rtcp);
+			break;
+		case MS_AES_256_SHA1_32:
+			crypto_policy_set_aes_cm_256_hmac_sha1_32(&policy.rtp);
+			crypto_policy_set_aes_cm_256_hmac_sha1_32(&policy.rtcp);
+			break;
+		case MS_CRYPTO_SUITE_INVALID:
+			return -1;
+			break;
+	}
+
+	/* check if key length match given policy */
+	if (key_length != policy.rtp.cipher_key_len) {
+		ms_error("Key size (%ld) doesn't match the selected srtp profile (required %d)", key_length, policy.rtp.cipher_key_len);	
+		return -1;
+	}
+
+	if (!inbound)
+		policy.allow_repeat_tx=1; /*necessary for telephone-events*/
+
+	/*ssrc_conf.type=inbound ? ssrc_any_inbound : ssrc_specific;*/
+	ssrc_conf.type=ssrc_specific;
+	ssrc_conf.value=ssrc;
+
+	policy.ssrc = ssrc_conf;
+	policy.key = (uint8_t *)key;
+	policy.next = NULL;
+
+	err = srtp_add_stream(srtp, &policy);
+	if (err != err_status_ok) {
+		ms_error("Failed to add stream to srtp session (%d)", err);
+		return -1;
+	}
+
+	return 0;
+}
+
+/***********************************************/
+/***** EXPORTED FUNCTIONS                  *****/
+/***********************************************/
+/**** Private to mediastreamer2 functions ****/
+/* header declared in voip/private.h */
+static int srtp_init_done=0;
+
+err_status_t ms_srtp_init(void)
+{
+
+	err_status_t st=0;
+	ms_message("srtp init");
+	if (!srtp_init_done) {
+		st=srtp_init();
+		if (st==0) {
+			srtp_init_done++;
+		}else{
+			ms_fatal("Couldn't initialize SRTP library.");
+			err_reporting_init("mediastreamer2");
+		}
+	}else srtp_init_done++;
+	return st;
+}