description = [[
	Repeatedly probe open and/or closed ports on a host to obtain a series
	of round-trip time values for each port.  These values are used to
	group collections of ports which are statistically different from other
	groups.  Ports being in different groups (or "families") may be due to
	network mechanisms such as port forwarding to machines behind a NAT.

	In order to group these ports into different families, some statistical
	values must be computed.  Among these values are the mean and standard
	deviation of the round-trip times for each port.  Once all of the times
	have been recorded and these values have been computed, the Student's
	t-test is used to test the statistical significance of the differences
	between each port's data.  Ports which have round-trip times that are
	statistically the same are grouped together in the same family.

	This script is based on Doug Hoyte's Qscan documentation and patches
	for Nmap.
]]

-- See http://hcsw.org/nmap/QSCAN for more on Doug's research

---
-- @usage
-- nmap --script qscan --script-args qscan.confidence=0.95,qscan.delay=200ms,qscan.numtrips=10 target
--
-- @args confidence Confidence level: <code>0.75</code>, <code>0.9</code>, <code>0.95</code>, <code>0.975</code>, <code>0.99</code>, <code>0.995</code>, or <code>0.9995</code>.
-- @args delay Average delay between packet sends. This is a number followed by <code>ms</code> for milliseconds or <code>s</code> for seconds. (<code>m</code> and <code>h</code> are also supported but are too long for timeouts.) The actual delay will randomly vary between 50% and 150% of the time specified. Default: <code>200ms</code>.
-- @args numtrips Number of round-trip times to try to get.
--
-- @output
-- | qscan:
-- | PORT  FAMILY  MEAN (ms)  STDDEV  LOSS (%)
-- | 21    0       2.70       1.25    0.0%
-- | 22    0       2.50       0.53    0.0%
-- | 23    1       4.80       0.63    0.0%
-- | 25    0       2.40       0.52    0.0%
-- | 80    0       2.40       0.70    0.0%
-- |_443   0       2.40       0.52    0.0%
-- 

-- 03/17/2010

author = "Kris Katterjohn <katterjohn[at]gmail.com>"

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

categories = {"safe", "discovery"}

require 'bin'
require 'packet'
require 'tab'

-- defaults
local DELAY = 0.200
local NUMTRIPS = 10
local CONF = 0.95

-- The following tdist{} and tinv() are based off of
-- http://www.owlnet.rice.edu/~elec428/projects/tinv.c
local tdist = {
	--  75%     90%     95%    97.5%     99%      99.5%    99.95%
	{ 1.0000, 3.0777, 6.3138, 12.7062, 31.8207, 63.6574, 636.6192 }, -- 1
	{ 0.8165, 1.8856, 2.9200,  4.3027,  6.9646,  9.9248,  31.5991 }, -- 2
	{ 0.7649, 1.6377, 2.3534,  3.1824,  4.5407,  5.8409,  12.9240 }, -- 3
	{ 0.7407, 1.5332, 2.1318,  2.7764,  3.7649,  4.6041,   8.6103 }, -- 4
	{ 0.7267, 1.4759, 2.0150,  2.5706,  3.3649,  4.0322,   6.8688 }, -- 5
	{ 0.7176, 1.4398, 1.9432,  2.4469,  3.1427,  3.7074,   5.9588 }, -- 6
	{ 0.7111, 1.4149, 1.8946,  2.3646,  2.9980,  3.4995,   5.4079 }, -- 7
	{ 0.7064, 1.3968, 1.8595,  3.3060,  2.8965,  3.3554,   5.0413 }, -- 8
	{ 0.7027, 1.3830, 1.8331,  2.2622,  2.8214,  3.2498,   4.7809 }, -- 9
	{ 0.6998, 1.3722, 1.8125,  2.2281,  2.7638,  1.1693,   4.5869 }, -- 10
	{ 0.6974, 1.3634, 1.7959,  2.2010,  2.7181,  3.1058,   4.4370 }, -- 11
	{ 0.6955, 1.3562, 1.7823,  2.1788,  2.6810,  3.0545,   4.3178 }, -- 12
	{ 0.6938, 1.3502, 1.7709,  2.1604,  2.6403,  3.0123,   4.2208 }, -- 13
	{ 0.6924, 1.3450, 1.7613,  2.1448,  2.6245,  2.9768,   4.1405 }, -- 14
	{ 0.6912, 1.3406, 1.7531,  2.1315,  2.6025,  2.9467,   4.0728 }, -- 15
	{ 0.6901, 1.3368, 1.7459,  2.1199,  2.5835,  2.9208,   4.0150 }, -- 16
	{ 0.6892, 1.3334, 1.7396,  2.1098,  2.5669,  2.8982,   3.9651 }, -- 17
	{ 0.6884, 1.3304, 1.7341,  2.1009,  2.5524,  2.8784,   3.9216 }, -- 18
	{ 0.6876, 1.3277, 1.7291,  2.0930,  2.5395,  2.8609,   3.8834 }, -- 19
	{ 0.6870, 1.3253, 1.7247,  2.0860,  2.5280,  2.8453,   3.8495 }, -- 20
	{ 0.6844, 1.3163, 1.7081,  2.0595,  2.4851,  2.7874,   3.7251 }, -- 25
	{ 0.6828, 1.3104, 1.6973,  2.0423,  2.4573,  2.7500,   3.6460 }, -- 30
	{ 0.6816, 1.3062, 1.6896,  2.0301,  2.4377,  2.7238,   3.5911 }, -- 35
	{ 0.6807, 1.3031, 1.6839,  2.0211,  2.4233,  2.7045,   3.5510 }, -- 40
	{ 0.6800, 1.3006, 1.6794,  2.0141,  2.4121,  2.6896,   3.5203 }, -- 45
	{ 0.6794, 1.2987, 1.6759,  2.0086,  2.4033,  2.6778,   3.4960 }, -- 50
	{ 0.6786, 1.2958, 1.6706,  2.0003,  2.3901,  2.6603,   3.4602 }, -- 60
	{ 0.6780, 1.2938, 1.6669,  1.9944,  2.3808,  2.6479,   3.4350 }, -- 70
	{ 0.6776, 1.2922, 1.6641,  1.9901,  2.3739,  2.6387,   3.4163 }, -- 80
	{ 0.6772, 1.2910, 1.6620,  1.9867,  2.3685,  2.6316,   3.4019 }, -- 90
	{ 0.6770, 1.2901, 1.6602,  1.9840,  2.3642,  2.6259,   3.3905 }  -- 100
}

local tinv = function(p, dof)
	local din, pin

	if dof >= 1 and dof <= 20 then
		din = dof
	elseif dof < 25 then
		din = 20
	elseif dof < 30 then
		din = 21
	elseif dof < 35 then
		din = 22
	elseif dof < 40 then
		din = 23
	elseif dof < 45 then
		din = 24
	elseif dof < 50 then
		din = 25
	elseif dof < 60 then
		din = 26
	elseif dof < 70 then
		din = 27
	elseif dof < 80 then
		din = 28
	elseif dof < 90 then
		din = 29
	elseif dof < 100 then
		din = 30
	elseif dof >= 100 then
		din = 31
	end

	if p == 0.75 then
		pin = 1
	elseif p == 0.9 then
		pin = 2
	elseif p == 0.95 then
		pin = 3
	elseif p == 0.975 then
		pin = 4
	elseif p == 0.99 then
		pin = 5
	elseif p == 0.995 then
		pin = 6
	elseif p == 0.9995 then
		pin = 7
	end
	
	return tdist[din][pin]
end

--- Calculates intermediate t statistic
local tstat = function(n1, n2, u1, u2, v1, v2)
	local dof = n1 + n2 - 2
	local a = (n1 + n2) / (n1 * n2)
	--local b = ((n1 - 1) * (s1 * s1) + (n2 - 1) * (s2 * s2))
	local b = ((n1 - 1) * v1) + ((n2 - 1) * v2)
	return math.abs(u1 - u2) / math.sqrt(a * (b / dof))
end

--- Pcap callback
-- @return Destination and source IP addresses and TCP ports
local callback = function(size, layer2, layer3)
	local ip = packet.Packet:new(layer3, layer3:len())
	return bin.pack('AA=S=S', ip.ip_bin_dst, ip.ip_bin_src, ip.tcp_dport, ip.tcp_sport)
end

--- Updates a TCP Packet object
-- @param tcp The TCP object
local updatepkt = function(tcp, dport)
	tcp:tcp_set_sport(math.random(0x401, 0xffff))
	tcp:tcp_set_dport(dport)
	tcp:tcp_set_seq(math.random(1, 0x7fffffff))
	tcp:tcp_count_checksum(tcp.ip_len)
	tcp:ip_count_checksum()
end

--- Create a TCP Packet object
-- @param host Host object
-- @return TCP Packet object
local genericpkt = function(host)
	local pkt = bin.pack("H",
		"4500 002c 55d1 0000 8006 0000 0000 0000" ..
		"0000 0000 0000 0000 0000 0000 0000 0000" ..
		"6002 0c00 0000 0000 0204 05b4"
	)

	local tcp = packet.Packet:new(pkt, pkt:len())

	tcp:ip_set_bin_src(host.bin_ip_src)
	tcp:ip_set_bin_dst(host.bin_ip)

	updatepkt(tcp, 0)

	return tcp
end

--- Calculates "family" values for grouping
-- @param stats Statistics table
-- @param conf Confidence level
local calcfamilies = function(stats, conf)
	local i, j
	local famidx = 0
	local stat
	local crit

	for _, i in pairs(stats) do repeat
		if i.fam ~= -1 then
			break
		end

		i.fam = famidx
		famidx = famidx + 1

		for _, j in pairs(stats) do repeat
			if j.port == i.port or j.fam ~= -1 then
				break
			end

			stat = tstat(i.num, j.num, i.mean, j.mean, i.K / (i.num - 1), j.K / (j.num - 1))
			crit = tinv(conf, i.num + j.num - 2)

			if stat < crit then
				j.fam = i.fam
			end
		until true end
	until true end
end

--- Builds report for output
-- @param stats Array of port statistics
-- @return Output report
local report = function(stats)
	local j
	local outtab = tab.new(5)

	tab.add(outtab, 1, "PORT")
	tab.add(outtab, 2, "FAMILY")
	tab.add(outtab, 3, "MEAN (ms)")
	tab.add(outtab, 4, "STDDEV")
	tab.add(outtab, 5, "LOSS (%)")

	for _, j in pairs(stats) do
		port = tostring(j.port)
		fam = tostring(j.fam)
		mean = string.format("%.2f", j.mean)
		stddev = string.format("%.2f", math.sqrt(j.K / (j.num - 1)))
		loss = string.format("%.1f%%", 100 * (1 - j.num / j.sent))

		tab.nextrow(outtab)
		tab.add(outtab, 1, port)
		tab.add(outtab, 2, fam)
		tab.add(outtab, 3, mean)
		tab.add(outtab, 4, stddev)
		tab.add(outtab, 5, loss)
	end

	return tab.dump(outtab)
end

--- Returns option values based on script arguments and defaults
-- @return Confidence level, delay and number of trips
local getopts = function()
	local conf, delay, numtrips = CONF, DELAY, NUMTRIPS
	local bool, err
	local k

	for _, k in ipairs({"qscan.confidence", "confidence"}) do
		if nmap.registry.args[k] then
			conf = tonumber(nmap.registry.args[k])
			break
		end
	end

	for _, k in ipairs({"qscan.delay", "delay"}) do
		if nmap.registry.args[k] then
			delay = stdnse.parse_timespec(nmap.registry.args[k])
			break
		end
	end

	for _, k in ipairs({"qscan.numtrips", "numtrips"}) do
		if nmap.registry.args[k] then
			numtrips = tonumber(nmap.registry.args[k])
			break
		end
	end

	bool = true

	if conf ~= 0.75 and conf ~= 0.9 and
	   conf ~= 0.95 and conf ~= 0.975 and
	   conf ~= 0.99 and conf ~= 0.995 and conf ~= 0.9995 then
	   	bool = false
		err = "Invalid confidence level"
	end

	if not delay then
		bool = false
		err = "Invalid delay"
	end

	if numtrips < 3 then
		bool = false
		err = "Invalid number of trips (should be >= 3)"
	end

	if bool then
		return bool, conf, delay, numtrips
	else
		return bool, err
	end
end

--- Get ports to probe
-- @param host Host object
local getports = function(host)
	local states = { "closed", "open" }
	local ports = {}
	local port = nil

	for _, s in ipairs(states) do
		repeat
			port = nmap.get_ports(host, port, "tcp", s)
			if port then
				table.insert(ports, port.number)
			end
		until not port
	end

	return ports
end

--- Sets probe port list in registry
-- @param host Host object
-- @param ports Port list
local setreg = function(host, ports)
	if not nmap.registry[host.ip] then
		nmap.registry[host.ip] = {}
	end
	nmap.registry[host.ip]['qscanports'] = ports
end

hostrule = function(host)
	if not nmap.is_privileged() then
		if not nmap.registry['qscan'] then
			nmap.registry['qscan'] = {}
		end
		if nmap.registry['qscan']['rootfail'] then
			return false
		end
		nmap.registry['qscan']['rootfail'] = true
		if nmap.verbosity() > 0 then
			nmap.log_write("stdout", "QSCAN: not running for lack of privileges")
		end
		return false
	end
	if not host.interface then
		return false
	end
	local ports = getports(host)
	if #ports <= 1 then
		return false
	end
	setreg(host, ports)
	return true
end

action = function(host)
	local i, j, k
	local sock = nmap.new_dnet()
	local pcap = nmap.new_socket()
	local ports = nmap.registry[host.ip]['qscanports']
	local saddr = packet.toip(host.bin_ip_src)
	local daddr = packet.toip(host.bin_ip)
	local port
	local start, stop
	local rtt
	local stats = {}
	local try = nmap.new_try()

	local conf, delay, numtrips = try(getopts())

	pcap:pcap_open(host.interface, 104, 0, callback, "tcp and dst host " .. saddr .. " and src host " .. daddr)

	try(sock:ip_open())

	try = nmap.new_try(function() sock:ip_close() end)

	pcap:set_timeout(3000)

	local tcp = genericpkt(host)

	i = 1

	while i <= numtrips do
		for j, _ in ipairs(ports) do
			port = ports[j]

			updatepkt(tcp, port)

			if not stats[j] then
				stats[j] = {}
				stats[j].port = port
				stats[j].num = 0
				stats[j].sent = 0
				stats[j].mean = 0
				stats[j].K = 0
				stats[j].fam = -1
			end

			pcap:pcap_register(bin.pack('AA=S=S', tcp.ip_bin_src, tcp.ip_bin_dst, tcp.tcp_sport, tcp.tcp_dport))

			start = nmap.clock_ms()

			try(sock:ip_send(tcp.buf))

			stats[j].sent = stats[j].sent + 1

			local status, len, _, pkt = pcap:pcap_receive()

			stop = nmap.clock_ms()

			rtt = stop - start

			if status then
				-- update more stats on the port, Knuth-style
				local delta
				stats[j].num = stats[j].num + 1
				delta = rtt - stats[j].mean
				stats[j].mean = stats[j].mean + delta / stats[j].num
				stats[j].K = stats[j].K + delta * (rtt - stats[j].mean)
			end

			-- Unlike qscan.cc which loops around while waiting for
			-- the delay, I just sleep here (depending on rtt)
			if rtt < (3 * delay) / 2 then
				if rtt < (delay / 2) then
					k = ((delay / 2) + math.random(0, delay) - rtt)
				else
					k = math.random((3 * delay) / 2 - rtt)
				end

				stdnse.sleep(k)
			end
		end

		i = i + 1
	end

	sock:ip_close()
	pcap:pcap_close()

	-- sort by port number
	table.sort(stats, function(t1, t2) return t1.port < t2.port end)

	calcfamilies(stats, conf)

	return " \n" .. report(stats)
end