From 0033eaa7ba2e1a15a8bc2bbe055c6cee264b7147 Mon Sep 17 00:00:00 2001
From: Doran Moppert <dmoppert@redhat.com>
Date: Tue, 26 Sep 2017 14:48:20 +0930
Subject: [PATCH] google patch hand-applied

---
 src/edns0.c   | 10 +++++-----
 src/forward.c |  4 ++++
 src/rfc1035.c |  8 +++++---
 3 files changed, 14 insertions(+), 8 deletions(-)

diff --git a/src/edns0.c b/src/edns0.c
index a9ee717..d3ab895 100644
--- a/src/edns0.c
+++ b/src/edns0.c
@@ -212,11 +212,11 @@ size_t add_pseudoheader(struct dns_header *header, size_t plen, unsigned char *l
       /* Copy back any options */
       if (buff)
 	{
-          if (p + rdlen > limit)
-          {
-            free(buff);
-            return plen; /* Too big */
-          }
+	  if (p + rdlen > limit)
+	  {
+	    free(buff);
+	    return plen; /* Too big */
+	  }
 	  memcpy(p, buff, rdlen);
 	  free(buff);
 	  p += rdlen;
diff --git a/src/forward.c b/src/forward.c
index 0f8f462..a729c06 100644
--- a/src/forward.c
+++ b/src/forward.c
@@ -1412,6 +1412,10 @@ void receive_query(struct listener *listen, time_t now)
 	udp_size = PACKETSZ; /* Sanity check - can't reduce below default. RFC 6891 6.2.3 */
     }
 
+  // Make sure the udp size is not smaller than the incoming message so that we
+  // do not underflow
+  if (udp_size < n) udp_size = n;
+
 #ifdef HAVE_AUTH
   if (auth_dns)
     {
diff --git a/src/rfc1035.c b/src/rfc1035.c
index ec3f283..aa7c664 100644
--- a/src/rfc1035.c
+++ b/src/rfc1035.c
@@ -1185,8 +1185,8 @@ int add_resource_record(struct dns_header *header, char *limit, int *truncp, int
   va_end(ap);	/* clean up variable argument pointer */
   
   j = p - sav - 2;
- /* this has already been checked against limit before */
- PUTSHORT(j, sav);     /* Now, store real RDLength */
+  /* this has already been checked against limit before */
+  PUTSHORT(j, sav);     /* Now, store real RDLength */
   
   /* check for overflow of buffer */
   if (limit && ((unsigned char *)limit - p) < 0)
@@ -1246,7 +1246,9 @@ size_t answer_request(struct dns_header *header, char *limit, size_t qlen,
   int nxdomain = 0, auth = 1, trunc = 0, sec_data = 1;
   struct mx_srv_record *rec;
   size_t len;
-  
+  // Make sure we do not underflow here too.
+  if (qlen > (limit - ((char *)header))) return 0;
+
   if (ntohs(header->ancount) != 0 ||
       ntohs(header->nscount) != 0 ||
       ntohs(header->qdcount) == 0 || 
-- 
2.9.5