res_pjsip_sdp_rtp: Add support for optimistic SRTP.

Optimistic SRTP is the ability to enable SRTP but not have it be
a fatal requirement. If SRTP can be used it will be, if not it won't be.
This gives you a better chance of using it without having your sessions
fail when it can't be.

Encrypt all the things!

Review: https://reviewboard.asterisk.org/r/3992/


git-svn-id: https://origsvn.digium.com/svn/asterisk/branches/13@428222 65c4cc65-6c06-0410-ace0-fbb531ad65f3

CHANGES

@@ -21,6 +21,14 @@ The features.conf general section has three new configurable options:
 For more information on what these options do, see the Asterisk wiki:
 	https://wiki.asterisk.org/wiki/x/W4fAAQ
 
+Channel Drivers
+------------------
+
+chan_pjsip
+------------------
+ * New 'media_encryption_optimistic' endpoint setting. This will use SRTP
+   when possible but does not consider lack of it a failure.
+
 ------------------------------------------------------------------------------
 --- Functionality changes from Asterisk 12 to Asterisk 13 --------------------
 ------------------------------------------------------------------------------

configs/samples/pjsip.conf.sample

@@ -646,6 +646,8 @@
 ;media_encryption=no    ; Determines whether res_pjsip will use and enforce
                         ; usage of media encryption for this endpoint (default:
                         ; "no")
+;media_encryption_optimistic=no ; Use encryption if possible but don't fail the call
+								; if not possible.
 ;inband_progress=no     ; Determines whether chan_pjsip will indicate ringing
                         ; using inband progress (default: "no")
 ;call_group=    ; The numeric pickup groups for a channel (default: "")

contrib/ast-db-manage/config/versions/eb88a14f2a_add_media_encryption_optimistic_to_pjsip.py

@@ -0,0 +1,31 @@
+"""add media encryption optimistic to pjsip
+
+Revision ID: eb88a14f2a
+Revises: 10aedae86a32
+Create Date: 2014-11-19 07:08:55.423018
+
+"""
+
+# revision identifiers, used by Alembic.
+revision = 'eb88a14f2a'
+down_revision = '10aedae86a32'
+
+from alembic import op
+import sqlalchemy as sa
+from sqlalchemy.dialects.postgresql import ENUM
+
+YESNO_NAME = 'yesno_values'
+YESNO_VALUES = ['yes', 'no']
+
+def upgrade():
+    ############################# Enums ##############################
+
+    # yesno_values have already been created, so use postgres enum object
+    # type to get around "already created" issue - works okay with mysql
+    yesno_values = ENUM(*YESNO_VALUES, name=YESNO_NAME, create_type=False)
+
+    op.add_column('ps_endpoints', sa.Column('media_encryption_optimistic', yesno_values))
+
+
+def downgrade():
+    op.drop_column('ps_endpoints', 'media_encryption_optimistic')

include/asterisk/res_pjsip.h

@@ -483,6 +483,8 @@ struct ast_sip_media_rtp_configuration {
 	unsigned int srtp_tag_32;
 	/*! Do we use media encryption? what type? */
 	enum ast_sip_session_media_encryption encryption;
+	/*! Do we want to optimistically support encryption if possible? */
+	unsigned int encryption_optimistic;
 };
 
 /*!

include/asterisk/res_pjsip_session.h

@@ -73,6 +73,8 @@ struct ast_sip_session_media {
 	struct ast_sip_session_sdp_handler *handler;
 	/*! \brief Holds SRTP information */
 	struct ast_sdp_srtp *srtp;
+	/*! \brief What type of encryption is in use on this stream */
+	enum ast_sip_session_media_encryption encryption;
 	/*! \brief The media transport in use for this stream */
 	pj_str_t transport;
 	/*! \brief Stream is on hold */

res/res_pjsip.c

@@ -430,6 +430,14 @@
 						</enumlist>
 					</description>
 				</configOption>
+				<configOption name="media_encryption_optimistic" default="no">
+					<synopsis>Determines whether encryption should be used if possible but does not terminate the
+					session if not achieved.</synopsis>
+					<description><para>
+						This option only applies if <replaceable>media_encryption</replaceable> is
+						set to <literal>sdes</literal> or <literal>dtls</literal>.
+					</para></description>
+				</configOption>
 				<configOption name="inband_progress" default="no">
 					<synopsis>Determines whether chan_pjsip will indicate ringing using inband
 					    progress.</synopsis>
@@ -1494,6 +1502,9 @@
 				<parameter name="MediaEncryption">
 					<para><xi:include xpointer="xpointer(/docs/configInfo[@name='res_pjsip']/configFile[@name='pjsip.conf']/configObject[@name='endpoint']/configOption[@name='media_encryption']/synopsis/node())"/></para>
 				</parameter>
+				<parameter name="MediaEncryptionOptimistic">
+					<para><xi:include xpointer="xpointer(/docs/configInfo[@name='res_pjsip']/configFile[@name='pjsip.conf']/configObject[@name='endpoint']/configOption[@name='media_encryption_optimistic']/synopsis/node())"/></para>
+				</parameter>
 				<parameter name="UseAvpf">
 					<para><xi:include xpointer="xpointer(/docs/configInfo[@name='res_pjsip']/configFile[@name='pjsip.conf']/configObject[@name='endpoint']/configOption[@name='use_avpf']/synopsis/node())"/></para>
 				</parameter>

res/res_pjsip/pjsip_configuration.c

@@ -1762,6 +1762,7 @@ int ast_res_pjsip_initialize_configuration(const struct ast_module_info *ast_mod
 	ast_sorcery_object_field_register_custom(sip_sorcery, "endpoint", "dtls_setup", "", dtls_handler, dtlssetup_to_str, NULL, 0, 0);
 	ast_sorcery_object_field_register_custom(sip_sorcery, "endpoint", "dtls_fingerprint", "", dtls_handler, dtlsfingerprint_to_str, NULL, 0, 0);
 	ast_sorcery_object_field_register(sip_sorcery, "endpoint", "srtp_tag_32", "no", OPT_BOOL_T, 1, FLDSET(struct ast_sip_endpoint, media.rtp.srtp_tag_32));
+	ast_sorcery_object_field_register(sip_sorcery, "endpoint", "media_encryption_optimistic", "no", OPT_BOOL_T, 1, FLDSET(struct ast_sip_endpoint, media.rtp.encryption_optimistic));
 	ast_sorcery_object_field_register_custom(sip_sorcery, "endpoint", "redirect_method", "user", redirect_handler, NULL, NULL, 0, 0);
 	ast_sorcery_object_field_register_custom(sip_sorcery, "endpoint", "set_var", "", set_var_handler, set_var_to_str, set_var_to_vl, 0, 0);
 	ast_sorcery_object_field_register(sip_sorcery, "endpoint", "message_context", "", OPT_STRINGFIELD_T, 1, STRFLDSET(struct ast_sip_endpoint, message_context));

res/res_pjsip_sdp_rtp.c

@@ -494,14 +494,41 @@ static void process_ice_attributes(struct ast_sip_session *session, struct ast_s
 	ice->start(session_media->rtp);
 }
 
+/*! \brief figure out if media stream has crypto lines for sdes */
+static int media_stream_has_crypto(const struct pjmedia_sdp_media *stream)
+{
+	int i;
+
+	for (i = 0; i < stream->attr_count; i++) {
+		pjmedia_sdp_attr *attr;
+
+		/* check the stream for the required crypto attribute */
+		attr = stream->attr[i];
+		if (pj_strcmp2(&attr->name, "crypto")) {
+			continue;
+		}
+
+		return 1;
+	}
+
+	return 0;
+}
+
 /*! \brief figure out media transport encryption type from the media transport string */
-static enum ast_sip_session_media_encryption get_media_encryption_type(pj_str_t transport)
+static enum ast_sip_session_media_encryption get_media_encryption_type(pj_str_t transport,
+	const struct pjmedia_sdp_media *stream, unsigned int *optimistic)
 {
 	RAII_VAR(char *, transport_str, ast_strndup(transport.ptr, transport.slen), ast_free);
+
+	*optimistic = 0;
+
 	if (strstr(transport_str, "UDP/TLS")) {
 		return AST_SIP_MEDIA_ENCRYPT_DTLS;
 	} else if (strstr(transport_str, "SAVP")) {
 		return AST_SIP_MEDIA_ENCRYPT_SDES;
+	} else if (media_stream_has_crypto(stream)) {
+		*optimistic = 1;
+		return AST_SIP_MEDIA_ENCRYPT_SDES;
 	} else {
 		return AST_SIP_MEDIA_ENCRYPT_NONE;
 	}
@@ -523,22 +550,31 @@ static enum ast_sip_session_media_encryption check_endpoint_media_transport(
 {
 	enum ast_sip_session_media_encryption incoming_encryption;
 	char transport_end = stream->desc.transport.ptr[stream->desc.transport.slen - 1];
+	unsigned int optimistic;
 
 	if ((transport_end == 'F' && !endpoint->media.rtp.use_avpf)
 		|| (transport_end != 'F' && endpoint->media.rtp.use_avpf)) {
 		return AST_SIP_MEDIA_TRANSPORT_INVALID;
 	}
 
-	incoming_encryption = get_media_encryption_type(stream->desc.transport);
+	incoming_encryption = get_media_encryption_type(stream->desc.transport, stream, &optimistic);
 
 	if (incoming_encryption == endpoint->media.rtp.encryption) {
 		return incoming_encryption;
 	}
 
-	if (endpoint->media.rtp.force_avp) {
+	if (endpoint->media.rtp.force_avp ||
+		endpoint->media.rtp.encryption_optimistic) {
 		return incoming_encryption;
 	}
 
+	/* If an optimistic offer has been made but encryption is not enabled consider it as having
+	 * no offer of crypto at all instead of invalid so the session proceeds.
+	 */
+	if (optimistic) {
+		return AST_SIP_MEDIA_ENCRYPT_NONE;
+	}
+
 	return AST_SIP_MEDIA_TRANSPORT_INVALID;
 }
 
@@ -697,7 +733,7 @@ static int setup_media_encryption(struct ast_sip_session *session,
 	const struct pjmedia_sdp_session *sdp,
 	const struct pjmedia_sdp_media *stream)
 {
-	switch (session->endpoint->media.rtp.encryption) {
+	switch (session_media->encryption) {
 	case AST_SIP_MEDIA_ENCRYPT_SDES:
 		if (setup_sdes_srtp(session_media, stream)) {
 			return -1;
@@ -726,6 +762,8 @@ static int negotiate_incoming_sdp_stream(struct ast_sip_session *session, struct
 	char host[NI_MAXHOST];
 	RAII_VAR(struct ast_sockaddr *, addrs, NULL, ast_free_ptr);
 	enum ast_media_type media_type = stream_to_media_type(session_media->stream_type);
+	enum ast_sip_session_media_encryption encryption = AST_SIP_MEDIA_ENCRYPT_NONE;
+	int res;
 
 	/* If port is 0, ignore this media stream */
 	if (!stream->desc.port) {
@@ -740,9 +778,12 @@ static int negotiate_incoming_sdp_stream(struct ast_sip_session *session, struct
 	}
 
 	/* Ensure incoming transport is compatible with the endpoint's configuration */
-	if (!session->endpoint->media.rtp.use_received_transport &&
-		check_endpoint_media_transport(session->endpoint, stream) == AST_SIP_MEDIA_TRANSPORT_INVALID) {
-		return -1;
+	if (!session->endpoint->media.rtp.use_received_transport) {
+		encryption = check_endpoint_media_transport(session->endpoint, stream);
+
+		if (encryption == AST_SIP_MEDIA_TRANSPORT_INVALID) {
+			return -1;
+		}
 	}
 
 	ast_copy_pj_str(host, stream->conn ? &stream->conn->addr : &sdp->conn->addr, sizeof(host));
@@ -758,13 +799,27 @@ static int negotiate_incoming_sdp_stream(struct ast_sip_session *session, struct
 		return -1;
 	}
 
-	if (session->endpoint->media.rtp.use_received_transport) {
+	res = setup_media_encryption(session, session_media, sdp, stream);
+	if (res) {
+		if (!session->endpoint->media.rtp.encryption_optimistic) {
+			/* If optimistic encryption is disabled and crypto should have been enabled
+			 * but was not this session must fail.
+			 */
+			return -1;
+		}
+		/* There is no encryption, sad. */
+		session_media->encryption = AST_SIP_MEDIA_ENCRYPT_NONE;
+ 	}
+
+	/* If we've been explicitly configured to use the received transport OR if
+	 * encryption is on and crypto is present use the received transport.
+	 * This is done in case of optimistic because it may come in as RTP/AVP or RTP/SAVP depending
+	 * on the configuration of the remote endpoint (optimistic themselves or mandatory).
+	 */
+	if ((session->endpoint->media.rtp.use_received_transport) ||
+		((encryption == AST_SIP_MEDIA_ENCRYPT_SDES) && !res)) {
 		pj_strdup(session->inv_session->pool, &session_media->transport, &stream->desc.transport);
-	}
-
-	if (setup_media_encryption(session, session_media, sdp, stream)) {
-		return -1;
-	}
+ 	}
 
 	if (set_caps(session, session_media, stream)) {
 		return 0;
@@ -788,7 +843,7 @@ static int add_crypto_to_stream(struct ast_sip_session *session,
 	static const pj_str_t STR_ACTPASS = { "actpass", 7 };
 	static const pj_str_t STR_HOLDCONN = { "holdconn", 8 };
 
-	switch (session->endpoint->media.rtp.encryption) {
+	switch (session_media->encryption) {
 	case AST_SIP_MEDIA_ENCRYPT_NONE:
 	case AST_SIP_MEDIA_TRANSPORT_INVALID:
 		break;
@@ -922,11 +977,14 @@ static int create_outgoing_sdp_stream(struct ast_sip_session *session, struct as
 	}
 
 	media->desc.media = pj_str(session_media->stream_type);
-	if (session->endpoint->media.rtp.use_received_transport && pj_strlen(&session_media->transport)) {
+	if (pj_strlen(&session_media->transport)) {
+		/* If a transport has already been specified use it */
 		media->desc.transport = session_media->transport;
 	} else {
 		media->desc.transport = pj_str(ast_sdp_get_rtp_profile(
-			session->endpoint->media.rtp.encryption == AST_SIP_MEDIA_ENCRYPT_SDES,
+			/* Optimistic encryption places crypto in the normal RTP/AVP profile */
+			!session->endpoint->media.rtp.encryption_optimistic &&
+				(session_media->encryption == AST_SIP_MEDIA_ENCRYPT_SDES),
 			session_media->rtp, session->endpoint->media.rtp.use_avpf,
 			session->endpoint->media.rtp.force_avp));
 	}
@@ -1062,7 +1120,7 @@ static int apply_negotiated_sdp_stream(struct ast_sip_session *session, struct a
 	RAII_VAR(struct ast_sockaddr *, addrs, NULL, ast_free_ptr);
 	enum ast_media_type media_type = stream_to_media_type(session_media->stream_type);
 	char host[NI_MAXHOST];
-	int fdno;
+	int fdno, res;
 
 	if (!session->channel) {
 		return 1;
@@ -1083,10 +1141,18 @@ static int apply_negotiated_sdp_stream(struct ast_sip_session *session, struct a
 		return -1;
 	}
 
-	if (setup_media_encryption(session, session_media, remote, remote_stream)) {
+	res = setup_media_encryption(session, session_media, remote, remote_stream);
+	if (!session->endpoint->media.rtp.encryption_optimistic && res) {
+		/* If optimistic encryption is disabled and crypto should have been enabled but was not
+		 * this session must fail.
+		 */
 		return -1;
 	}
 
+	if (!remote_stream->conn && !remote->conn) {
+		return 1;
+	}
+
 	ast_copy_pj_str(host, remote_stream->conn ? &remote_stream->conn->addr : &remote->conn->addr, sizeof(host));
 
 	/* Ensure that the address provided is valid */
@@ -1136,6 +1202,9 @@ static int apply_negotiated_sdp_stream(struct ast_sip_session *session, struct a
 		session_media->held = 0;
 	}
 
+	/* This purposely resets the encryption to the configured in case it gets added later */
+	session_media->encryption = session->endpoint->media.rtp.encryption;
+
 	return 1;
 }
 

res/res_pjsip_session.c

@@ -1000,6 +1000,7 @@ static int add_session_media(void *obj, void *arg, int flags)
 	if (!session_media) {
 		return CMP_STOP;
 	}
+	session_media->encryption = session->endpoint->media.rtp.encryption;
 	/* Safe use of strcpy */
 	strcpy(session_media->stream_type, handler_list->stream_type);
 	ao2_link(session->media, session_media);
@@ -1046,6 +1047,8 @@ struct ast_sip_session *ast_sip_session_alloc(struct ast_sip_endpoint *endpoint,
 		return NULL;
 	}
 
+	session->endpoint = ao2_bump(endpoint);
+
 	session->media = ao2_container_alloc(MEDIA_BUCKETS, session_media_hash, session_media_cmp);
 	if (!session->media) {
 		return NULL;
@@ -1061,7 +1064,6 @@ struct ast_sip_session *ast_sip_session_alloc(struct ast_sip_endpoint *endpoint,
 	ast_sip_dialog_set_endpoint(inv_session->dlg, endpoint);
 	pjsip_dlg_inc_session(inv_session->dlg, &session_module);
 	inv_session->mod_data[session_module.id] = ao2_bump(session);
-	session->endpoint = ao2_bump(endpoint);
 	session->contact = ao2_bump(contact);
 	session->inv_session = inv_session;
 	session->req_caps = ast_format_cap_alloc(AST_FORMAT_CAP_FLAG_DEFAULT);