From 59a6ce3b0ed3bba5f95e2fb1a5060eecdeff8a66 Mon Sep 17 00:00:00 2001
From: Remi Gacogne <remi.gacogne@powerdns.com>
Date: Thu, 26 Jan 2023 15:07:02 +0100
Subject: [PATCH] Check the record size before allocating in
 PacketReader::copyRecord()

Technically that does not matter because the size is limited to
2^16-1 bytes, and if the size is incorrect we will throw during the
copy, but it's nicer to detect the incorrect size before allocating,
as suggested by Coverity (CID 383044).
---
 pdns/dnsparser.cc | 38 ++++++++++++++++++++++----------------
 1 file changed, 22 insertions(+), 16 deletions(-)

diff --git a/pdns/dnsparser.cc b/pdns/dnsparser.cc
index 9a2ee1a599..930668f935 100644
--- a/pdns/dnsparser.cc
+++ b/pdns/dnsparser.cc
@@ -345,40 +345,46 @@ bool MOADNSParser::hasEDNS() const
 
 void PacketReader::getDnsrecordheader(struct dnsrecordheader &ah)
 {
-  unsigned int n;
-  unsigned char *p=reinterpret_cast<unsigned char*>(&ah);
+  unsigned char *p = reinterpret_cast<unsigned char*>(&ah);
 
-  for(n=0; n < sizeof(dnsrecordheader); ++n)
-    p[n]=d_content.at(d_pos++);
+  for(unsigned int n = 0; n < sizeof(dnsrecordheader); ++n) {
+    p[n] = d_content.at(d_pos++);
+  }
 
-  ah.d_type=ntohs(ah.d_type);
-  ah.d_class=ntohs(ah.d_class);
-  ah.d_clen=ntohs(ah.d_clen);
-  ah.d_ttl=ntohl(ah.d_ttl);
+  ah.d_type = ntohs(ah.d_type);
+  ah.d_class = ntohs(ah.d_class);
+  ah.d_clen = ntohs(ah.d_clen);
+  ah.d_ttl = ntohl(ah.d_ttl);
 
-  d_startrecordpos=d_pos; // needed for getBlob later on
-  d_recordlen=ah.d_clen;
+  d_startrecordpos = d_pos; // needed for getBlob later on
+  d_recordlen = ah.d_clen;
 }
 
 
 void PacketReader::copyRecord(vector<unsigned char>& dest, uint16_t len)
 {
-  dest.resize(len);
-  if(!len)
+  if (len == 0) {
     return;
+  }
+  if ((d_pos + len) > d_content.size()) {
+    throw std::out_of_range("Attempt to copy outside of packet");
+  }
+
+  dest.resize(len);
 
-  for(uint16_t n=0;n<len;++n) {
-    dest.at(n)=d_content.at(d_pos++);
+  for (uint16_t n = 0; n < len; ++n) {
+    dest.at(n) = d_content.at(d_pos++);
   }
 }
 
 void PacketReader::copyRecord(unsigned char* dest, uint16_t len)
 {
-  if(d_pos + len > d_content.size())
+  if (d_pos + len > d_content.size()) {
     throw std::out_of_range("Attempt to copy outside of packet");
+  }
 
   memcpy(dest, &d_content.at(d_pos), len);
-  d_pos+=len;
+  d_pos += len;
 }
 
 void PacketReader::xfrNodeOrLocatorID(NodeOrLocatorID& ret)
-- 
2.47.2