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 -- -- @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