Re: -6 and mass_dns and dns.lua

[jah <jah () zadkiel plus com>]

Hi again,

Attached is a patch which enables l_get_dns_servers() to return dns
servers to NSE when nmap_mass_rdns() is called with no targets and
o.mass_dns is false.

It does the job, but the problem is that the --system-dns option is not
respected, making the patch a non-starter - I attach it in the hope that
someone knows or can think of another approach.

To illustrate the problem, a scan such as:

  nmap -6 -p80 -PN -d --script ASN ipv6.google.com

would yield

  SCRIPT ENGINE DEBUG: AS Numbers Failed to send dns query.  Response
from dns.query(): 9

whereas the same scan with the patch applied would result in the
expected script output:

  Host script results:
  |  AS Numbers:
  |  BGP: 2001:4860::/32 | Country: US
  |_   Origin AS: 15169 - GOOGLE - Google Inc.

You could also see the effect of the patch with an IPv4 target:

  nmap -p80 -PN -d --script ASN --system-dns www.google.com

So does anyone have any bright ideas?

Regards,

jah

--- nmap_dns.cc.orig    2008-10-06 20:55:34.062500000 +0100
+++ nmap_dns.cc 2008-10-06 19:33:30.875000000 +0100
@@ -1129,7 +1129,7 @@
   bool lasttrace = false;
   char spmobuf[1024];
 
-  if (o.mass_dns == false) {
+  if (o.mass_dns == false && num_targets) {
     Target *currenths;
     struct sockaddr_storage ss;
     size_t sslen;
@@ -1175,7 +1175,7 @@
     if (servs.size() == 0 && firstrun) error("mass_dns: warning: Unable to determine any DNS servers. Reverse DNS is 
disabled. Try using --system-dns or specify valid servers with --dns-servers");
   }
 
-
+  if (!num_targets) return;
   // If necessary, set up the /etc/hosts hashtable
   etchosts_init();
 
@@ -1332,8 +1332,11 @@
 std::list<std::string> get_dns_servers() {
   // if, for example, run with -n, list is not initialized,
   // run empty nmap_mass_rdns to do so
-  if(servs.size() == 0 && firstrun) {
+  static int firstNoTargets=1;
+  
+  if(servs.size() == 0 && (firstrun || firstNoTargets)) {
     nmap_mass_rdns(NULL, 0);
+       firstNoTargets = 0;
   }
   std::list<dns_server *>::iterator servI;
   std::list<std::string> serverList;


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