[Dnsmasq-discuss] CVE-2015-7547 tcp path mitigation hack

[starlight at binnacle.cx]

UDP path mitigation covered by

   edns-packet-max=512

Ugly but effective TCP fix:


--- src/forward.c.orig  2011-02-17 10:30:15.000000000 -0500
+++ src/forward.c       2016-02-17 23:16:03.792233438 -0500
@@ -966,14 +966,17 @@ unsigned char *tcp_request(int confd, ti
          /* In case of local answer or no connections made. */
          if (m == 0)
            m = setup_reply(header, (unsigned int)size, addrp, flags, daemon->local_ttl);
        }

       check_log_writer(NULL);

+      /* mitigate CVE-2015-7547, truncate beyond 1023 bytes */
+      m &= 0x3FF;
+
       c1 = m>>8;
       c2 = m;
       if (!read_write(confd, &c1, 1, 0) ||
          !read_write(confd, &c2, 1, 0) ||
          !read_write(confd, packet, m, 0))
        return packet;
     }