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o [NSE] Added script broadcast-listener that attempts to discover hosts by
passively listening to the network. It does so by decoding ethernet and IP broadcast and multicast messages. [Patrik]
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patrik
278
scripts/broadcast-listener.nse
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278
scripts/broadcast-listener.nse
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description = [[
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The script sniffs the network for incoming broadcast communication and
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attempts to decode the received packets. It supports protocols like CDP, HSRP,
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Spotify, DropBox, DHCP, ARP and a few more. See packetdecoders.lua for more
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information.
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The script attempts to sniff all ethernet based interfaces with an IPv4 address
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unless a specific interface was given using the -e argument to Nmap.
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]]
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---
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-- @usage
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-- nmap --script broadcast-listener
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-- nmap --script broadcast-listener -e eth0
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--
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-- @output
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-- | broadcast-listener:
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-- | udp
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-- | Netbios
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-- | ip query
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-- | 192.168.0.60 \x01\x02__MSBROWSE__\x02\x01
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-- | DHCP
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-- | srv ip cli ip mask gw dns
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-- | 192.168.0.1 192.168.0.5 255.255.255.0 192.168.0.1 192.168.0.18, 192.168.0.19
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-- | DropBox
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-- | displayname ip port version host_int namespaces
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-- | 39000860 192.168.0.107 17500 1.8 39000860 28814673, 29981099
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-- | HSRP
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-- | ip version op state prio group secret virtual ip
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-- | 192.168.0.254 0 Hello Active 110 1 cisco 192.168.0.253
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-- | ether
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-- | CDP
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-- | ip id platform version
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-- | ? Router cisco 7206VXR 12.3(23)
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-- | ARP Request
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-- | sender ip sender mac target ip
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-- | 192.168.0.101 00:04:30:26:DA:C8 192.168.0.60
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-- |_ 192.168.0.1 90:24:1D:C8:B9:AE 192.168.0.60
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--
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-- @args broadcast-listener.timeout specifies the amount of seconds to sniff
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-- the network interface. (default 30s)
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--
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-- The script attempts to discover all available ipv4 network interfaces,
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-- unless the Nmap -e argument has been supplied, and then starts sniffing
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-- packets on all of the discovered interfaces. It sets a BPF filter to exclude
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-- all packets that have the interface address as source or destination in
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-- order to capture broadcast traffic.
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--
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-- Incoming packets can either be either layer 3 (usually UDP) or layer 2.
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-- Depending on the layer the packet is matched against a packet decoder loaded
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-- from the external nselib/data/packetdecoder.lua file. A more detailed
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-- description on how the decoders work can be found in that file.
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-- In short, there are two different types of decoders: udp and ether.
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-- The udp decoders get triggered by the destination port number, while the
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-- ether decoders are triggered by a pattern match. The port or pattern is used
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-- as an index in a table containing functions to process packets and fetch
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-- the decoded results.
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--
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--
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-- Version 0.1
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-- Created 07/02/2011 - v0.1 - created by Patrik Karlsson <patrik@cqure.net>
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-- Revised 07/25/2011 - v0.2 -
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-- * added more documentation
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-- * added getInterfaces code to detect available
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-- interfaces.
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-- * corrected bug that would fail to load
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-- decoders if not in a relative directory.
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author = "Patrik Karlsson"
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license = "Same as Nmap--See http://nmap.org/book/man-legal.html"
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categories = {"safe"}
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prerule = function() return true end
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require('packet')
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require('tab')
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---
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-- loads the decoders from file
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--
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-- @param fname string containing the name of the file
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-- @return status true on success false on failure
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-- @return decoders table of decoder functions on success
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-- @return err string containing the error message on failure
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loadDecoders = function(fname)
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-- resolve the full, absolute, path
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local abs_fname = nmap.fetchfile(fname)
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if ( not(abs_fname) ) then
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return false, ("ERROR: Failed to load decoder definition (%s)"):format(fname)
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end
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local file = loadfile(abs_fname)
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if(not(file)) then
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stdnse.print_debug("%s: Couldn't load decoder file: %s", SCRIPT_NAME, fname)
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return false, "ERROR: Couldn't load decoder file: " .. fname
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end
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setfenv(file, setmetatable({Decoders = {}; }, {__index = _G}))
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file()
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local d = getfenv(file)["Decoders"]
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if ( d ) then return true, d end
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return false, "ERROR: Failed to load decoders"
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end
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---
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-- Starts sniffing the selected interface for packets with a destination that
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-- is not explicitly ours (broadcast, multicast etc.)
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--
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-- @param iface table containing <code>name</code> and <code>address</code>
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-- @param Decoders the decoders class loaded externally
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-- @param decodertab the "result" table to which all discovered items are
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-- reported
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sniffInterface = function(iface, Decoders, decodertab)
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local condvar = nmap.condvar(decodertab)
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local sock = nmap.new_socket()
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local timeout = tonumber(stdnse.get_script_args("broadcast-listener.timeout"))
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-- default to 30 seconds, if nothing else was set
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timeout = timeout and (timeout * 1000) or (30 * 1000)
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-- We wan't all packets that aren't explicitly for us
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sock:pcap_open(iface.name, 1500, false, ("!host %s"):format(iface.address))
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-- Set a short timeout so that we can timeout in time if needed
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sock:set_timeout(100)
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local start_time = nmap.clock_ms()
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while( nmap.clock_ms() - start_time < timeout ) do
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local status, _, _, data = sock:pcap_receive()
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if ( status ) then
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local p = packet.Packet:new( data, #data )
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-- if we have an UDP-based broadcast, we should have a proper packet
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if ( p and p.udp_dport and ( decodertab.udp[p.udp_dport] or Decoders.udp[p.udp_dport] ) ) then
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if ( not(decodertab.udp[p.udp_dport]) ) then
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decodertab.udp[p.udp_dport] = Decoders.udp[p.udp_dport]:new()
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end
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decodertab.udp[p.udp_dport]:process(data)
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-- The packet was decoded successfully but we don't have a valid decoder
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-- Report this
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elseif ( p and p.udp_dport ) then
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stdnse.print_debug(2, "No decoder for dst port %d", p.udp_dport)
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-- we don't have a packet, so this is most likely something layer2 based
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-- in that case, check the ether Decoder table for pattern matches
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else
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-- attempt to find a match for a pattern
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local pos, hex = bin.unpack("H" .. #data, data)
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local decoded = false
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for match, _ in pairs(Decoders.ether) do
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-- attempts to match the "raw" packet against a filter
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-- supplied in each ethernet packet decoder
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if ( hex:match(match) ) then
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if ( not(decodertab.ether[match]) ) then
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decodertab.ether[match] = Decoders.ether[match]:new()
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end
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-- start a new decoding thread. This way, if something gets foobared
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-- the whole script doesn't break, only the packet decoding for that
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-- specific packet.
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stdnse.new_thread( decodertab.ether[match].process, decodertab.ether[match], data )
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decoded = true
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end
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end
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-- no decoder was found for this layer2 packet
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if ( not(decoded) and #data > 10 ) then
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stdnse.print_debug(2, "No decoder for packet hex: %s", select(2, bin.unpack("H10", 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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condvar "signal"
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end
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---
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-- Gets a list of available interfaces based on link and up filters
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-- Interfaces are only added if they've got an ipv4 address
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--
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-- @param link string containing the link type to filter
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-- @param up string containing the interface status to filter
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-- @return result table containing tables of interfaces
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-- each interface table has the following fields:
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-- <code>name</code> containing the device name
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-- <code>address</code> containing the device address
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getInterfaces = function(link, up)
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if( not(nmap.list_interfaces) ) then return end
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local interfaces, err = nmap.list_interfaces()
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local result
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if ( not(err) ) then
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for _, iface in ipairs(interfaces) do
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if ( iface.link == link and
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iface.up == up and
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iface.address ) then
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-- exclude ipv6 addresses for now
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if ( not(iface.address:match(":")) ) then
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result = result or {}
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table.insert(result, { name = iface.device,
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address = iface.address } )
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end
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end
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end
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end
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return result
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end
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action = function()
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local DECODERFILE = "nselib/data/packetdecoders.lua"
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local iface = nmap.get_interface()
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local interfaces = {}
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-- was an interface supplied using the -e argument?
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if ( iface ) then
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local iinfo, err = nmap.get_interface_info(iface)
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if ( not(iinfo.address) ) then
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return "\n ERROR: The IP address of the interface could not be determined ..."
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end
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interfaces = { { name = iface, address = iinfo.address } }
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else
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-- no interface was supplied, attempt autodiscovery
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interfaces = getInterfaces("ethernet", "up")
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end
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-- make sure we have at least one interface to start sniffing
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if ( #interfaces == 0 ) then
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return "\n ERROR: Could not determine any valid interfaces"
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end
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-- load the decoders from file
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local status, Decoders = loadDecoders(DECODERFILE)
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if ( not(status) ) then return "\n " .. Decoders end
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-- create a local table to handle instantiated decoders
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local decodertab = { udp = {}, ether = {} }
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local condvar = nmap.condvar(decodertab)
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local threads = {}
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-- start a thread for each interface to sniff
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for _, iface in ipairs(interfaces) do
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local co = stdnse.new_thread(sniffInterface, iface, Decoders, decodertab)
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threads[co] = true
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end
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-- wait for all threads to finish sniffing
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repeat
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condvar "wait"
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for thread in pairs(threads) do
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if coroutine.status(thread) == "dead" then
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threads[thread] = nil
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end
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end
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until next(threads) == nil
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local out_outer = {}
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-- create the results table
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for proto, _ in pairs(decodertab) do
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local out_inner = {}
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for key, decoder in pairs(decodertab[proto]) do
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table.insert( out_inner, decodertab[proto][key]:getResults() )
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end
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if ( #out_inner > 0 ) then
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table.insert( out_outer, { name = proto, out_inner } )
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end
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end
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return stdnse.format_output(true, out_outer)
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end
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