From: Remi Gacogne <remi.gacogne@powerdns.com>
Date: Wed, 2 Mar 2016 15:50:02 +0000 (+0100)
Subject: dnsdist: Fix a crash when adding an invalid packet to the cache
X-Git-Tag: rec-4.0.0-alpha2~21^2~1
X-Git-Url: https://granicus.if.org/sourcecode?a=commitdiff_plain;h=cceddbeff82cf031f93af458361bfcfb23909586;p=pdns

dnsdist: Fix a crash when adding an invalid packet to the cache

Reported by @rygl.
---

diff --git a/pdns/dnsdist-cache.cc b/pdns/dnsdist-cache.cc
index 2d951bc56..ed5221091 100644
--- a/pdns/dnsdist-cache.cc
+++ b/pdns/dnsdist-cache.cc
@@ -197,10 +197,17 @@ uint32_t DNSDistPacketCache::getKey(const DNSName& qname, uint16_t consumed, con
 {
   uint32_t result = 0;
   /* skip the query ID */
+  if (packetLen < sizeof(dnsheader))
+    throw std::range_error("Computing packet cache key for an invalid packet size");
   result = burtle(packet + 2, sizeof(dnsheader) - 2, result);
   string lc(qname.toDNSStringLC());
   result = burtle((const unsigned char*) lc.c_str(), lc.length(), result);
-  result = burtle(packet + sizeof(dnsheader) + consumed, packetLen - (sizeof(dnsheader) + consumed), result);
+  if (packetLen < sizeof(dnsheader) + consumed) {
+    throw std::range_error("Computing packet cache key for an invalid packet");
+  }
+  if (packetLen > ((sizeof(dnsheader) + consumed))) {
+    result = burtle(packet + sizeof(dnsheader) + consumed, packetLen - (sizeof(dnsheader) + consumed), result);
+  }
   result = burtle((const unsigned char*) &tcp, sizeof(tcp), result);
   return result;
 }