chan_sip: Fix crash when accessing RURI before initiating outgoing call

Attempting to access ${CHANNEL(ruri)} in a pre-dial handler before
initiating an outgoing call will cause Asterisk to crash. This is
because a null field is accessed, resulting in an offset from null and
subsequent memory access violation.

Since RURI is not guaranteed to exist, we now check if the base
pointer is non-null before calculating an offset.

ASTERISK-29772

Change-Id: Icd3b02f07256bbe6615854af5717074087b95a83

diff --git a/channels/sip/dialplan_functions.c b/channels/sip/dialplan_functions.c
index 7c34fc9023ef530ff97f3b7d4b9e371d3f640481..74106d1be771fac0f91203acce1ac08bd2a146aa 100644 (file)
--- a/channels/sip/dialplan_functions.c
+++ b/channels/sip/dialplan_functions.c
@@ -166,8 +166,12 @@ int sip_acf_channel_read(struct ast_channel *chan, const char *funcname, char *p
        } else if (!strcasecmp(args.param, "uri")) {
                ast_copy_string(buf, p->uri, buflen);
        } else if (!strcasecmp(args.param, "ruri")) {
-               char *tmpruri = REQ_OFFSET_TO_STR(&p->initreq, rlpart2);
-               ast_copy_string(buf, tmpruri, buflen);
+               if (p->initreq.data) {
+                       char *tmpruri = REQ_OFFSET_TO_STR(&p->initreq, rlpart2);
+                       ast_copy_string(buf, tmpruri, buflen);
+               } else {
+                       return -1;
+               }
        } else if (!strcasecmp(args.param, "useragent")) {
                ast_copy_string(buf, p->useragent, buflen);
        } else if (!strcasecmp(args.param, "peername")) {