Don't overflow when paging more than 128 extensions

The number of available slots for calls in app_page was hardcoded to 128.
Proper bounds checking was not in place to enforce this limit, so if more than
128 extensions were passed to the Page() app, Asterisk would crash.  This patch
instead dynamically allocates memory for the ast_dial structures and removes
the (non-functional) arbitrary limit.

This issue would have special importance to anyone who is dynamically creating
the argument passed to the Page application and allowing more than 128
extensions to be added by an outside user via some external interface.

The patch posted by a_villacis was slightly modified for some coding guidelines
and other cleanups.  Thanks, a_villacis!
(closes issue #14217)
Reported by: a_villacis
Patches: 
      20080912-asterisk-app_page-fix-buffer-overflow.patch uploaded by a (license 660)
Tested by: otherwiseguy


git-svn-id: https://origsvn.digium.com/svn/asterisk/branches/1.4@168593 65c4cc65-6c06-0410-ace0-fbb531ad65f3

apps/app_page.c

@@ -78,18 +78,18 @@ AST_APP_OPTIONS(page_opts, {
 	AST_APP_OPTION('r', PAGE_RECORD),
 });
 
-#define MAX_DIALS 128
 
 static int page_exec(struct ast_channel *chan, void *data)
 {
 	struct ast_module_user *u;
-	char *options, *tech, *resource, *tmp;
+	char *options, *tech, *resource, *tmp, *tmp2;
 	char meetmeopts[88], originator[AST_CHANNEL_NAME];
 	struct ast_flags flags = { 0 };
 	unsigned int confid = ast_random();
 	struct ast_app *app;
 	int res = 0, pos = 0, i = 0;
-	struct ast_dial *dials[MAX_DIALS];
+	struct ast_dial **dial_list;
+	unsigned int num_dials;
 
 	if (ast_strlen_zero(data)) {
 		ast_log(LOG_WARNING, "This application requires at least one argument (destination(s) to page)\n");
@@ -117,6 +117,19 @@ static int page_exec(struct ast_channel *chan, void *data)
 	snprintf(meetmeopts, sizeof(meetmeopts), "MeetMe|%ud|%s%sqxdw(5)", confid, (ast_test_flag(&flags, PAGE_DUPLEX) ? "" : "m"),
 		(ast_test_flag(&flags, PAGE_RECORD) ? "r" : "") );
 
+	/* Count number of extensions in list by number of ampersands + 1 */
+	num_dials = 1;
+	tmp2 = tmp;
+	while (*tmp2 && *tmp2++ == '&') {
+		num_dials++;
+	}
+
+	if (!(dial_list = ast_calloc(num_dials, sizeof(void *)))) {
+		ast_log(LOG_ERROR, "Can't allocate %ld bytes for dial list\n", (sizeof(void *) * num_dials));
+		ast_module_user_remove(u);
+		return -1;
+	}
+
 	/* Go through parsing/calling each device */
 	while ((tech = strsep(&tmp, "&"))) {
 		struct ast_dial *dial = NULL;
@@ -149,7 +162,7 @@ static int page_exec(struct ast_channel *chan, void *data)
 		ast_dial_run(dial, chan, 1);
 
 		/* Put in our dialing array */
-		dials[pos++] = dial;
+		dial_list[pos++] = dial;
 	}
 
 	if (!ast_test_flag(&flags, PAGE_QUIET)) {
@@ -166,7 +179,7 @@ static int page_exec(struct ast_channel *chan, void *data)
 
 	/* Go through each dial attempt cancelling, joining, and destroying */
 	for (i = 0; i < pos; i++) {
-		struct ast_dial *dial = dials[i];
+		struct ast_dial *dial = dial_list[i];
 
 		/* We have to wait for the async thread to exit as it's possible Meetme won't throw them out immediately */
 		ast_dial_join(dial);
@@ -178,6 +191,7 @@ static int page_exec(struct ast_channel *chan, void *data)
 		ast_dial_destroy(dial);
 	}
 
+	ast_free(dial_list);
 	ast_module_user_remove(u);
 
 	return -1;