110 lines
3.4 KiB
Lua
110 lines
3.4 KiB
Lua
local dns = require "dns"
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local nmap = require "nmap"
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local shortport = require "shortport"
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local stdnse = require "stdnse"
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local string = require "string"
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description = [[
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Retrieves information from a DNS nameserver by requesting
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its nameserver ID (nsid) and asking for its id.server and
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version.bind values. This script performs the same queries as the following
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two dig commands:
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- dig CH TXT bind.version @target
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- dig +nsid CH TXT id.server @target
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References:
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[1]http://www.ietf.org/rfc/rfc5001.txt
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[2]http://www.ietf.org/rfc/rfc4892.txt
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]]
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---
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-- @usage
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-- nmap -sSU -p 53 --script dns-nsid <target>
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--
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-- @output
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-- 53/udp open domain udp-response
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-- | dns-nsid:
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-- | NSID dns.example.com (646E732E6578616D706C652E636F6D)
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-- | id.server: dns.example.com
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-- |_ bind.version: 9.7.3-P3
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--
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-- @xmloutput
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-- <table key="NSID">
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-- <elem key="raw">mia01.l.root-servers.org</elem>
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-- <elem key="hex">6d696130312e6c2e726f6f742d736572766572732e6f7267</elem>
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-- </table>
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-- <elem key="id.server">mia01.l.root-servers.org</elem>
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-- <elem key="bind.version">NSD 3.2.15</elem>
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author = "John R. Bond"
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license = "Simplified (2-clause) BSD license--See https://nmap.org/svn/docs/licenses/BSD-simplified"
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categories = {"discovery", "default", "safe"}
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portrule = function (host, port)
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if not shortport.port_or_service(53, "domain", {"tcp", "udp"})(host, port) then
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return false
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end
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-- only check tcp if udp is not open or open|filtered
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if port.protocol == 'tcp' then
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local tmp_port = nmap.get_port_state(host, {number=port.number, protocol="udp"})
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if tmp_port then
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return not string.match(tmp_port.state, '^open')
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end
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end
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return true
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end
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local function rr_filter(pktRR, label)
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for _, rec in ipairs(pktRR, label) do
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if ( rec[label] and 0 < #rec.data ) then
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if ( dns.types.OPT == rec.dtype ) then
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if #rec.data < 4 then
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return false, "Failed to decode NSID"
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end
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local _, len, pos = string.unpack(">I2 I2", rec.data)
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if ( len ~= #rec.data - pos + 1 ) then
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return false, "Failed to decode NSID"
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end
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return true, string.unpack("c" .. len, rec.data, pos)
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else
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return true, string.unpack(">s1", rec.data)
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end
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end
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end
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end
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action = function(host, port)
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local result = stdnse.output_table()
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local flag = false
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local status, resp = dns.query("id.server", {host = host.ip, port=port.number, proto=port.protocol, dtype='TXT', class=dns.CLASS.CH, retAll=true, retPkt=true, nsid=true, dnssec=true})
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if ( status ) then
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local status, nsid = rr_filter(resp.add,'OPT')
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if ( status ) then
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flag = true
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-- RFC 5001 says NSID can be any arbitrary bytes, and should be displayed
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-- as hex, but often it is a readable string. Store both.
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result["NSID"] = { raw = nsid, hex = stdnse.tohex(nsid) }
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setmetatable(result["NSID"], {
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__tostring = function(t)
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return ("%s (%s)"):format(t.raw, t.hex)
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end
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})
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end
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local status, id_server = rr_filter(resp.answers,'TXT')
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if ( status ) then
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flag = true
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result["id.server"] = id_server
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end
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end
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local status, bind_version = dns.query("version.bind", {host = host.ip, port=port.number, proto=port.protocol, dtype='TXT', class=dns.CLASS.CH})
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if ( status ) then
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flag = true
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result["bind.version"] = bind_version
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end
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if flag then
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return result
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end
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end
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