local bin = require "bin"
local dns = require "dns"
local shortport = require "shortport"
local stdnse = require "stdnse"
local table = require "table"
description = [[
Retrieves information from a DNS nameserver by requesting
its nameserver ID (nsid) and asking for its id.server and
version.bind values. This script performs the same queries as the following
two dig commands:
- dig CH TXT bind.version @target
- dig +nsid CH TXT id.server @target
References:
[1]http://www.ietf.org/rfc/rfc5001.txt
[2]http://www.ietf.org/rfc/rfc4892.txt
]]
---
-- @usage
-- nmap -sSU -p 53 --script dns-nsid <target>
--
-- @output
-- 53/udp open domain udp-response
-- | dns-nsid:
-- | NSID dns.example.com (646E732E6578616D706C652E636F6D)
-- | id.server: dns.example.com
-- |_ bind.version: 9.7.3-P3
---
author = "John Bond"
license = "Simplified (2-clause) BSD license--See http://nmap.org/svn/docs/licenses/BSD-simplified"
categories = {"discovery", "default"}
portrule = shortport.port_or_service(53, "domain", {"tcp", "udp"})
local function rr_filter(pktRR, label)
for _, rec in ipairs(pktRR, label) do
if ( rec[label] and 0 < #rec.data ) then
if ( dns.types.OPT == rec.dtype ) then
local pos, _, len = bin.unpack(">SS", rec.data)
if ( len ~= #rec.data - pos + 1 ) then
return false, "Failed to decode NSID"
end
return true, select(2, bin.unpack("A" .. len, rec.data, pos))
else
return true, select(2, bin.unpack("p", rec.data))
end
end
end
end
action = function(host, port)
local result = {}
local status, resp = dns.query("id.server", {host = host.ip, dtype='TXT', class=dns.CLASS.CH, retAll=true, retPkt=true, nsid=true, dnssec=true})
if ( status ) then
local status, nsid = rr_filter(resp.add,'OPT')
if ( status ) then
table.insert(result, ("NSID: %s (%s)"):format(nsid, stdnse.tohex(nsid)))
end
local status, id_server = rr_filter(resp.answers,'TXT')
if ( status ) then
table.insert(result, ("id.server: %s"):format(id_server))
end
end
local status, bind_version = dns.query("version.bind", {host = host.ip, dtype='TXT', class=dns.CLASS.CH})
if ( status ) then
table.insert(result, ("bind.version: %s"):format(bind_version))
end
return stdnse.format_output(true, result)
end
@KyuuKazami