Fix possible buffer overread

JFreegman · JFreegman · commit c292c217422a · 2022-04-02T10:49:44.000-04:00
diff --git a/toxcore/group_announce.c b/toxcore/group_announce.c
@@ -191,6 +191,10 @@ static int gca_unpack_announce(const Logger *log, const uint8_t *data, uint16_t
     }
 
     if (announce->ip_port_is_set) {
+        if (length - offset == 0) {
+            return -1;
+        }
+
         const int ip_port_length = unpack_ip_port(&announce->ip_port, data + offset, length - offset, false);
 
         if (ip_port_length == -1) {

Original file line number	Diff line number	Diff line change
`@@ -191,6 +191,10 @@ static int gca_unpack_announce(const Logger log, const uint8_t data, uint16_t`
`191`	`191`	`}`
`192`	`192`
`193`	`193`	`if (announce->ip_port_is_set) {`
	`194`	`+ if (length - offset == 0) {`
	`195`	`+ return -1;`
	`196`	`+ }`
	`197`	`+`
`194`	`198`	`const int ip_port_length = unpack_ip_port(&announce->ip_port, data + offset, length - offset, false);`
`195`	`199`
`196`	`200`	`if (ip_port_length == -1) {`