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: / usr / share / nmap / scripts /
Filename : sniffer-detect.nse
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local nmap = require "nmap"
local stdnse = require "stdnse"
local string = require "string"

description = [[
Checks if a target on a local Ethernet has its network card in promiscuous mode.

The techniques used are described at
http://www.securityfriday.com/promiscuous_detection_01.pdf.
]]

---
-- @output
-- Host script results:
-- |_ sniffer-detect: Likely in promiscuous mode (tests: "11111111")


author = "Marek Majkowski"
license = "Same as Nmap--See http://nmap.org/book/man-legal.html"

categories = {"discovery", "intrusive"}

-- okay, we're interested only in hosts that are on our ethernet lan
hostrule = function(host)
	if nmap.address_family() ~= 'inet' then
		stdnse.print_debug("%s is IPv4 compatible only.", SCRIPT_NAME)
		return false
	end
	if host.directly_connected == true and
	  host.mac_addr ~= nil and
	  host.mac_addr_src ~= nil and
	  host.interface ~= nil then
	        local iface = nmap.get_interface_info(host.interface)
	        if iface and iface.link == 'ethernet' then
	              return true
	        end
	end
	return false
end

local function check (layer2)
	return string.sub(layer2, 0, 12)
end


do_test = function(dnet, pcap, host, test)
	local status, length, layer2, layer3
	local i = 0

	-- ARP requests are send with timeouts: 10ms, 40ms, 90ms
	-- before each try, we wait at least 100ms
	-- in summary, this test takes at least 100ms and at most 440ms
	for i=1,3 do
		-- flush buffers :), wait quite long.
		repeat
			pcap:set_timeout(100)
			local test = host.mac_addr_src .. host.mac_addr
			status, length, layer2, layer3 = pcap:pcap_receive()
			while status and test ~= check(layer2) do
				status, length, layer2, layer3 = pcap:pcap_receive()
			end
		until status ~= true
		pcap:set_timeout(10 * i*i)

		dnet:ethernet_send(test)

		local test = host.mac_addr_src .. host.mac_addr
		status, length, layer2, layer3 = pcap:pcap_receive()
		while status and test ~= check(layer2) do
			status, length, layer2, layer3 = pcap:pcap_receive()
		end
		if status == true then
			-- the basic idea, was to inform user about time, when we got packet
			-- so that 1 would mean (0-10ms), 2=(10-40ms) and 3=(40ms-90ms)
			-- but when we're running this tests on macs, first test is always 2.
			-- which means that the first answer is dropped.
			-- for now, just return 1 if test was successfull, it's easier
			-- return(i)
			return(1)
		end
	end
	return('_')
end

action = function(host)
	local dnet = nmap.new_dnet()
	local pcap = nmap.new_socket()
	local _
	local status
	local results = {
		['1_____1_'] = false, -- MacOSX(Tiger.Panther)/Linux/ ?Win98/ WinXP sp2(no pcap)
		['1_______'] = false, -- Old Apple/SunOS/3Com
		['1___1_1_'] = false, -- MacOSX(Tiger)
		['11111111'] = true,  -- BSD/Linux/OSX/     (or not promiscous openwrt )
		['1_1___1_'] = false, -- WinXP sp2 + pcap|| win98 sniff || win2k sniff (see below)
		['111___1_'] = true,  -- WinXP sp2 promisc
--		['1111__1_'] = true,  -- ?Win98 promisc + ??win98 no promisc *not confirmed*
		}
	dnet:ethernet_open(host.interface)

	pcap:pcap_open(host.interface, 64, false, "arp")

	local test_static = host.mac_addr_src ..
			string.char(0x08,0x06, 0x00,0x01, 0x08,0x00, 0x06,0x04, 0x00,0x01) ..
			host.mac_addr_src ..
			host.bin_ip_src ..
			string.char(0x00,0x00, 0x00,0x00, 0x00,0x00) ..
			host.bin_ip
	local t = {
		string.char(0xff,0xff, 0xff,0xff, 0xff,0xff), -- B32 no meaning?
		string.char(0xff,0xff, 0xff,0xff, 0xff,0xfe), -- B31
		string.char(0xff,0xff, 0x00,0x00, 0x00,0x00), -- B16
		string.char(0xff,0x00, 0x00,0x00, 0x00,0x00), -- B8
		string.char(0x01,0x00, 0x00,0x00, 0x00,0x00), -- G
		string.char(0x01,0x00, 0x5e,0x00, 0x00,0x00), -- M0
		string.char(0x01,0x00, 0x5e,0x00, 0x00,0x01), -- M1 no meaning?
		string.char(0x01,0x00, 0x5e,0x00, 0x00,0x03), -- M3
		}
	local v
	local out = ""
	for _, v in ipairs(t) do
		out = out .. do_test(dnet, pcap, host, v .. test_static)
	end

	dnet:ethernet_close()
	pcap:pcap_close()

	if out == '1_1___1_' then
		return 'Windows with libpcap installed; may or may not be sniffing (tests: "' .. out .. '")'
	end
	if results[out] == false then
		-- probably not sniffing
		return
	end
	if results[out] == true then
		-- rather sniffer.
		return 'Likely in promiscuous mode (tests: "' .. out .. '")'
	end

	-- results[out] == nil
	return 'Unknown (tests: "' .. out .. '")'
end