chan_pjsip: Use session for retrieving CHANNEL() information.

The CHANNEL() dialplan function implementation for PJSIP allows
querying of PJSIP specific information. This used the channel
passed in to get the PJSIP session and associated information.
It is possible for this channel to be masqueraded and end
up as a different channel type by the time the information
request is actually acted upon.

This change retrieves the PJSIP session safely and accesses
data from it (including channel). This provides a guarantee
that the session and channel will not be altered when the
request is being acted upon.

ASTERISK-26673

Change-Id: I335e12b89e1820cafdd92b3e7526b8ba649eb7e6

1 files changed, 29 insertions, 33 deletions

diff --git a/channels/pjsip/dialplan_functions.c b/channels/pjsip/dialplan_functions.c
index c3fe848e4..17c19b7c0 100644
--- a/channels/pjsip/dialplan_functions.c
+++ b/channels/pjsip/dialplan_functions.c
@@ -720,7 +720,7 @@ static int channel_read_pjsip(struct ast_channel *chan, const char *type, const
 
 /*! \brief Struct used to push function arguments to task processor */
 struct pjsip_func_args {
-	struct ast_channel *chan;
+	struct ast_sip_session *session;
 	const char *param;
 	const char *type;
 	const char *field;
@@ -735,49 +735,31 @@ static int read_pjsip(void *data)
 	struct pjsip_func_args *func_args = data;
 
 	if (!strcmp(func_args->param, "rtp")) {
-		func_args->ret = channel_read_rtp(func_args->chan, func_args->type,
+		func_args->ret = channel_read_rtp(func_args->session->channel, func_args->type,
 		                                  func_args->field, func_args->buf,
 		                                  func_args->len);
 	} else if (!strcmp(func_args->param, "rtcp")) {
-		func_args->ret = channel_read_rtcp(func_args->chan, func_args->type,
+		func_args->ret = channel_read_rtcp(func_args->session->channel, func_args->type,
 		                                   func_args->field, func_args->buf,
 		                                   func_args->len);
 	} else if (!strcmp(func_args->param, "endpoint")) {
-		struct ast_sip_channel_pvt *pvt = ast_channel_tech_pvt(func_args->chan);
-
-		if (!pvt) {
-			ast_log(AST_LOG_WARNING, "Channel %s has no pvt!\n", ast_channel_name(func_args->chan));
+		if (!func_args->session->endpoint) {
+			ast_log(AST_LOG_WARNING, "Channel %s has no endpoint!\n", ast_channel_name(func_args->session->channel));
 			return -1;
 		}
-		if (!pvt->session || !pvt->session->endpoint) {
-			ast_log(AST_LOG_WARNING, "Channel %s has no endpoint!\n", ast_channel_name(func_args->chan));
-			return -1;
-		}
-		snprintf(func_args->buf, func_args->len, "%s", ast_sorcery_object_get_id(pvt->session->endpoint));
+		snprintf(func_args->buf, func_args->len, "%s", ast_sorcery_object_get_id(func_args->session->endpoint));
 	} else if (!strcmp(func_args->param, "contact")) {
-		struct ast_sip_channel_pvt *pvt = ast_channel_tech_pvt(func_args->chan);
-
-		if (!pvt) {
-			ast_log(AST_LOG_WARNING, "Channel %s has no pvt!\n", ast_channel_name(func_args->chan));
-			return -1;
-		}
-		if (!pvt->session || !pvt->session->contact) {
+		if (!func_args->session->contact) {
 			return 0;
 		}
-		snprintf(func_args->buf, func_args->len, "%s", ast_sorcery_object_get_id(pvt->session->contact));
+		snprintf(func_args->buf, func_args->len, "%s", ast_sorcery_object_get_id(func_args->session->contact));
 	} else if (!strcmp(func_args->param, "aor")) {
-		struct ast_sip_channel_pvt *pvt = ast_channel_tech_pvt(func_args->chan);
-
-		if (!pvt) {
-			ast_log(AST_LOG_WARNING, "Channel %s has no pvt!\n", ast_channel_name(func_args->chan));
-			return -1;
-		}
-		if (!pvt->session || !pvt->session->aor) {
+		if (!func_args->session->aor) {
 			return 0;
 		}
-		snprintf(func_args->buf, func_args->len, "%s", ast_sorcery_object_get_id(pvt->session->aor));
+		snprintf(func_args->buf, func_args->len, "%s", ast_sorcery_object_get_id(func_args->session->aor));
 	} else if (!strcmp(func_args->param, "pjsip")) {
-		func_args->ret = channel_read_pjsip(func_args->chan, func_args->type,
+		func_args->ret = channel_read_pjsip(func_args->session->channel, func_args->type,
 		                                    func_args->field, func_args->buf,
 		                                    func_args->len);
 	} else {
@@ -804,7 +786,6 @@ int pjsip_acf_channel_read(struct ast_channel *chan, const char *cmd, char *data
 		ast_log(LOG_WARNING, "No channel was provided to %s function.\n", cmd);
 		return -1;
 	}
-	channel = ast_channel_tech_pvt(chan);
 
 	/* Check for zero arguments */
 	if (ast_strlen_zero(parse)) {
@@ -814,29 +795,44 @@ int pjsip_acf_channel_read(struct ast_channel *chan, const char *cmd, char *data
 
 	AST_STANDARD_APP_ARGS(args, parse);
 
+	ast_channel_lock(chan);
+
 	/* Sanity check */
 	if (strcmp(ast_channel_tech(chan)->type, "PJSIP")) {
 		ast_log(LOG_WARNING, "Cannot call %s on a non-PJSIP channel\n", cmd);
+		ast_channel_unlock(chan);
 		return 0;
 	}
 
+	channel = ast_channel_tech_pvt(chan);
 	if (!channel) {
-		ast_log(AST_LOG_WARNING, "Channel %s has no pvt!\n", ast_channel_name(chan));
+		ast_log(LOG_WARNING, "Channel %s has no pvt!\n", ast_channel_name(chan));
+		ast_channel_unlock(chan);
 		return -1;
 	}
 
+	if (!channel->session) {
+		ast_log(LOG_WARNING, "Channel %s has no session\n", ast_channel_name(chan));
+		ast_channel_unlock(chan);
+		return -1;
+	}
+
+	func_args.session = ao2_bump(channel->session);
+	ast_channel_unlock(chan);
+
 	memset(buf, 0, len);
 
-	func_args.chan = chan;
 	func_args.param = args.param;
 	func_args.type = args.type;
 	func_args.field = args.field;
 	func_args.buf = buf;
 	func_args.len = len;
-	if (ast_sip_push_task_synchronous(channel->session->serializer, read_pjsip, &func_args)) {
+	if (ast_sip_push_task_synchronous(func_args.session->serializer, read_pjsip, &func_args)) {
 		ast_log(LOG_WARNING, "Unable to read properties of channel %s: failed to push task\n", ast_channel_name(chan));
+		ao2_ref(func_args.session, -1);
 		return -1;
 	}
+	ao2_ref(func_args.session, -1);
 
 	return func_args.ret;
 }