[Asterisk-Dev] Patch to avoid writing to constant strings in pbx.c

[Luke Howard]

pbx_substitute_variables_temp() would try to write to a constant string
in cases such as a remote endpoint having no caller ID and an offset
being defined.

In the following example, if CALLERIDNUM was NULL, it would be set to
"", and pbx_substitute_variables_temp() would try and assign a value to
the constant string "".

[remote]
exten => _95555XXX,1,SetCallerID(+61${CALLERIDNUM:1})
exten => _95555XXX,2,Goto(default,${EXTEN:5},1)

One workaround would be to compile with -fwriteable-strings, but the 
attached patch fixes this properly (at least for the said function).

-- Luke

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Index: pbx.c
===================================================================
RCS file: /usr/cvsroot/asterisk/pbx.c,v
retrieving revision 1.1.1.12
diff -u -r1.1.1.12 pbx.c
--- pbx.c	18 Mar 2003 19:55:35 -0000	1.1.1.12
+++ pbx.c	23 Mar 2003 08:20:48 -0000
@@ -718,21 +718,26 @@
 		if (num) {
 			ast_shrink_phone_number(num);
 			*cp4 = num;
-		} else
-			*cp4 = "";
+		} else {
+			cid[0] = '\0';
+			*cp4 = cid;
+		}
 	} else if (!strcmp(cp3, "CALLERIDNAME")) {
 		char cid[256] = "";
 		if (c->callerid)
 			strncpy(cid, c->callerid, sizeof(cid) - 1);
 		ast_callerid_parse(cid, &name, &num);
-		if (name)
+		if (name) {
 			*cp4 = name;
-		else
-			*cp4 = "";
+		} else {
+			cid[0] = '\0';
+			*cp4 = cid;
+		}
 	} else if (!strcmp(cp3, "CALLERID")) {
+		char cid[1] = "";
 		*cp4 = c->callerid;
 		if (!(*cp4))
-			*cp4 = "";
+			*cp4 = cid;
 	} else if (!strcmp(cp3, "EXTEN")) {
 		*cp4 = c->exten;
 	} else if (!strncmp(cp3, "EXTEN-", strlen("EXTEN-")) && 
@@ -754,9 +759,10 @@
 		*cp4 = c->exten + offset;
 #endif
 	} else if (!strcmp(cp3, "RDNIS")) {
+		char rdins[1] = "";
 		*cp4 = c->rdnis;
 		if (!(*cp4))
-			*cp4 = "";
+			*cp4 = rdins;
 	} else if (!strcmp(cp3, "CONTEXT")) {
 		*cp4 = c->context;
 	} else if (!strcmp(cp3, "PRIORITY")) {
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--
Luke Howard | PADL Software Pty Ltd | www.padl.com