Fix CVE-2017-13704, which resulted in a crash on a large DNS query.
A DNS query recieved by UDP which exceeds 512 bytes (or the EDNS0 packet size,
if different.) is enough to cause SIGSEGV.
diff --git a/src/forward.c b/src/forward.c
index f22556a..e3fa94b 100644
--- a/src/forward.c
+++ b/src/forward.c
@@ -1188,6 +1188,10 @@
(msg.msg_flags & MSG_TRUNC) ||
(header->hb3 & HB3_QR))
return;
+
+ /* Clear buffer beyond request to avoid risk of
+ information disclosure. */
+ memset(daemon->packet + n, 0, daemon->edns_pktsz - n);
source_addr.sa.sa_family = listen->family;
@@ -1688,6 +1692,10 @@
if (size < (int)sizeof(struct dns_header))
continue;
+
+ /* Clear buffer beyond request to avoid risk of
+ information disclosure. */
+ memset(payload + size, 0, 65536 - size);
query_count++;