local _G = require "_G" local bin = require "bin" local coroutine = require "coroutine" local nmap = require "nmap" local packet = require "packet" local stdnse = require "stdnse" local table = require "table" description = [[ Sniffs the network for incoming broadcast communication and attempts to decode the received packets. It supports protocols like CDP, HSRP, Spotify, DropBox, DHCP, ARP and a few more. See packetdecoders.lua for more information. The script attempts to sniff all ethernet based interfaces with an IPv4 address unless a specific interface was given using the -e argument to Nmap. ]] --- -- @usage -- nmap --script broadcast-listener -- nmap --script broadcast-listener -e eth0 -- -- @output -- | broadcast-listener: -- | udp -- | Netbios -- | ip query -- | 192.168.0.60 \x01\x02__MSBROWSE__\x02\x01 -- | DHCP -- | srv ip cli ip mask gw dns -- | 192.168.0.1 192.168.0.5 255.255.255.0 192.168.0.1 192.168.0.18, 192.168.0.19 -- | DropBox -- | displayname ip port version host_int namespaces -- | 39000860 192.168.0.107 17500 1.8 39000860 28814673, 29981099 -- | HSRP -- | ip version op state prio group secret virtual ip -- | 192.168.0.254 0 Hello Active 110 1 cisco 192.168.0.253 -- | ether -- | CDP -- | ip id platform version -- | ? Router cisco 7206VXR 12.3(23) -- | ARP Request -- | sender ip sender mac target ip -- | 192.168.0.101 00:04:30:26:DA:C8 192.168.0.60 -- |_ 192.168.0.1 90:24:1D:C8:B9:AE 192.168.0.60 -- -- @args broadcast-listener.timeout specifies the amount of seconds to sniff -- the network interface. (default 30s) -- -- The script attempts to discover all available ipv4 network interfaces, -- unless the Nmap -e argument has been supplied, and then starts sniffing -- packets on all of the discovered interfaces. It sets a BPF filter to exclude -- all packets that have the interface address as source or destination in -- order to capture broadcast traffic. -- -- Incoming packets can either be either layer 3 (usually UDP) or layer 2. -- Depending on the layer the packet is matched against a packet decoder loaded -- from the external nselib/data/packetdecoder.lua file. A more detailed -- description on how the decoders work can be found in that file. -- In short, there are two different types of decoders: udp and ether. -- The udp decoders get triggered by the destination port number, while the -- ether decoders are triggered by a pattern match. The port or pattern is used -- as an index in a table containing functions to process packets and fetch -- the decoded results. -- -- -- Version 0.1 -- Created 07/02/2011 - v0.1 - created by Patrik Karlsson -- Revised 07/25/2011 - v0.2 - -- * added more documentation -- * added getInterfaces code to detect available -- interfaces. -- * corrected bug that would fail to load -- decoders if not in a relative directory. author = "Patrik Karlsson" license = "Same as Nmap--See https://nmap.org/book/man-legal.html" categories = {"broadcast", "safe"} prerule = function() if not nmap.is_privileged() then stdnse.verbose1("not running for lack of privileges.") return false end return true end --- -- loads the decoders from file -- -- @param fname string containing the name of the file -- @return status true on success false on failure -- @return decoders table of decoder functions on success -- @return err string containing the error message on failure loadDecoders = function(fname) -- resolve the full, absolute, path local abs_fname = nmap.fetchfile(fname) if ( not(abs_fname) ) then return false, ("Failed to load decoder definition (%s)"):format(fname) end local env = setmetatable({Decoders = {}}, {__index = _G}); local file = loadfile(abs_fname, "t", env) if(not(file)) then stdnse.debug1("Couldn't load decoder file: %s", fname) return false, "Couldn't load decoder file: " .. fname end file() local d = env.Decoders if ( d ) then return true, d end return false, "Failed to load decoders" end --- -- Starts sniffing the selected interface for packets with a destination that -- is not explicitly ours (broadcast, multicast etc.) -- -- @param iface table containing name and address -- @param Decoders the decoders class loaded externally -- @param decodertab the "result" table to which all discovered items are -- reported sniffInterface = function(iface, Decoders, decodertab) local condvar = nmap.condvar(decodertab) local sock = nmap.new_socket() local timeout = stdnse.parse_timespec(stdnse.get_script_args("broadcast-listener.timeout")) -- default to 30 seconds, if nothing else was set timeout = (timeout or 30) * 1000 -- We want all packets that aren't explicitly for us sock:pcap_open(iface.name, 1500, true, ("!host %s"):format(iface.address)) -- Set a short timeout so that we can timeout in time if needed sock:set_timeout(100) local start_time = nmap.clock_ms() while( nmap.clock_ms() - start_time < timeout ) do local status, _, _, data = sock:pcap_receive() if ( status ) then local p = packet.Packet:new( data, #data ) -- if we have an UDP-based broadcast, we should have a proper packet if ( p and p.udp_dport and ( decodertab.udp[p.udp_dport] or Decoders.udp[p.udp_dport] ) ) then if ( not(decodertab.udp[p.udp_dport]) ) then decodertab.udp[p.udp_dport] = Decoders.udp[p.udp_dport]:new() end decodertab.udp[p.udp_dport]:process(data) -- The packet was decoded successfully but we don't have a valid decoder -- Report this elseif ( p and p.udp_dport ) then stdnse.debug2("No decoder for dst port %d", p.udp_dport) -- we don't have a packet, so this is most likely something layer2 based -- in that case, check the ether Decoder table for pattern matches else -- attempt to find a match for a pattern local pos, hex = bin.unpack("H" .. #data, data) local decoded = false for match, _ in pairs(Decoders.ether) do -- attempts to match the "raw" packet against a filter -- supplied in each ethernet packet decoder if ( hex:match(match) ) then if ( not(decodertab.ether[match]) ) then decodertab.ether[match] = Decoders.ether[match]:new() end -- start a new decoding thread. This way, if something gets foobared -- the whole script doesn't break, only the packet decoding for that -- specific packet. stdnse.new_thread( decodertab.ether[match].process, decodertab.ether[match], data ) decoded = true end end -- no decoder was found for this layer2 packet if ( not(decoded) and #data > 10 ) then stdnse.debug1("No decoder for packet hex: %s", select(2, bin.unpack("H10", data) ) ) end end end end condvar "signal" end --- -- Gets a list of available interfaces based on link and up filters -- Interfaces are only added if they've got an ipv4 address -- -- @param link string containing the link type to filter -- @param up string containing the interface status to filter -- @return result table containing tables of interfaces -- each interface table has the following fields: -- name containing the device name -- address containing the device address getInterfaces = function(link, up) if( not(nmap.list_interfaces) ) then return end local interfaces, err = nmap.list_interfaces() local result = {} if ( not(err) ) then for _, iface in ipairs(interfaces) do if ( iface.link == link and iface.up == up and iface.address ) then -- exclude ipv6 addresses for now if ( not(iface.address:match(":")) ) then table.insert(result, { name = iface.device, address = iface.address } ) end end end end return result end local function fail (err) return stdnse.format_output(false, err) end action = function() local DECODERFILE = "nselib/data/packetdecoders.lua" local iface = nmap.get_interface() local interfaces = {} -- was an interface supplied using the -e argument? if ( iface ) then local iinfo, err = nmap.get_interface_info(iface) if ( not(iinfo.address) ) then return fail("The IP address of the interface could not be determined") end interfaces = { { name = iface, address = iinfo.address } } else -- no interface was supplied, attempt autodiscovery interfaces = getInterfaces("ethernet", "up") end -- make sure we have at least one interface to start sniffing if ( #interfaces == 0 ) then return fail("Could not determine any valid interfaces") end -- load the decoders from file local status, Decoders = loadDecoders(DECODERFILE) if ( not(status) ) then return fail(Decoders) end -- create a local table to handle instantiated decoders local decodertab = { udp = {}, ether = {} } local condvar = nmap.condvar(decodertab) local threads = {} -- start a thread for each interface to sniff for _, iface in ipairs(interfaces) do local co = stdnse.new_thread(sniffInterface, iface, Decoders, decodertab) threads[co] = true end -- wait for all threads to finish sniffing repeat for thread in pairs(threads) do if coroutine.status(thread) == "dead" then threads[thread] = nil end end if ( next(threads) ) then condvar "wait" end until next(threads) == nil local out_outer = {} -- create the results table for proto, _ in pairs(decodertab) do local out_inner = {} for key, decoder in pairs(decodertab[proto]) do table.insert( out_inner, decodertab[proto][key]:getResults() ) end if ( #out_inner > 0 ) then table.insert( out_outer, { name = proto, out_inner } ) end end table.sort(out_outer, function(a, b) return a.name < b.name end) return stdnse.format_output(true, out_outer) end