local bin = require "bin"
local math = require "math"
local nmap = require "nmap"
local packet = require "packet"
local stdnse = require "stdnse"
local string = require "string"
local tab = require "tab"
local table = require "table"

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.
-- @args numopen Maximum number of open ports to probe (default 8). A negative number disables the limit.
-- @args numclosed Maximum number of closed ports to probe (default 1). A negative number disables the limit.
--
-- @output
-- | qscan:
-- | PORT  FAMILY  MEAN (us)  STDDEV  LOSS (%)
-- | 21    0       2082.70    460.72  0.0%
-- | 22    0       2211.70    886.69  0.0%
-- | 23    1       4631.90    606.67  0.0%
-- | 24    0       1922.40    336.90  0.0%
-- | 25    0       2017.30    404.31  0.0%
-- | 80    1       4180.80    856.98  0.0%
-- |_443   0       2013.30    368.91  0.0%
-- 

-- 03/17/2010

author = "Kris Katterjohn"

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

categories = {"safe", "discovery"}


-- defaults
local DELAY = 0.200
local NUMTRIPS = 10
local CONF = 0.95
local NUMOPEN = 8
local NUMCLOSED = 1

-- 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
}

-- cache ports to probe between the hostrule and the action function
local qscanports


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 check
-- @return Destination and source IP addresses and TCP ports
local check = function(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()

	tab.add(outtab, 1, "PORT")
	tab.add(outtab, 2, "FAMILY")
	tab.add(outtab, 3, "MEAN (us)")
	tab.add(outtab, 4, "STDDEV")
	tab.add(outtab, 5, "LOSS (%)")
	tab.nextrow(outtab)
  local port, fam, mean, stddev, 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.add(outtab, 1, port)
		tab.add(outtab, 2, fam)
		tab.add(outtab, 3, mean)
		tab.add(outtab, 4, stddev)
		tab.add(outtab, 5, loss)
		tab.nextrow(outtab)
	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

local table_extend = function(a, b)
	local t = {}

	for _, v in ipairs(a) do
		t[#t + 1] = v
	end
	for _, v in ipairs(b) do
		t[#t + 1] = v
	end

	return t
end

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

	port = nil
	while numopen < 0 or #open < numopen do
		port = nmap.get_ports(host, port, "tcp", "open")
		if not port then
			break
		end
		open[#open + 1] = port.number
	end
	port = nil
	while numclosed < 0 or #closed < numclosed do
		port = nmap.get_ports(host, port, "tcp", "closed")
		if not port then
			break
		end
		closed[#closed + 1] = port.number
	end

	return table_extend(open, closed)
end

hostrule = function(host)
	if not nmap.is_privileged() then
		nmap.registry[SCRIPT_NAME] = nmap.registry[SCRIPT_NAME] or {}
		if not nmap.registry[SCRIPT_NAME].rootfail then
			stdnse.print_verbose("%s not running for lack of privileges.", SCRIPT_NAME)
		end
		nmap.registry[SCRIPT_NAME].rootfail = true
		return nil
	end

	local numopen, numclosed = NUMOPEN, NUMCLOSED

	if nmap.address_family() ~= 'inet' then
		stdnse.print_debug("%s is IPv4 compatible only.", SCRIPT_NAME)
		return false
	end
	if not host.interface then
		return false
	end

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

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

	qscanports = getports(host, numopen, numclosed)
	return (#qscanports > 1)
end

action = function(host)
	local sock = nmap.new_dnet()
	local pcap = nmap.new_socket()
	local saddr = packet.toip(host.bin_ip_src)
	local daddr = packet.toip(host.bin_ip)
	local start
	local rtt
	local stats = {}
	local try = nmap.new_try()

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

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

	try(sock:ip_open())

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

	-- Simply double the calculated host timeout to account for possible
	-- extra time due to port forwarding or whathaveyou.  Nmap has all
	-- ready scanned this host, so the timing should have taken into
	-- account some of the RTT differences, but I think it really depends
	-- on how many ports were scanned and how many were forwarded where.
	-- Play it safer here.
	pcap:set_timeout(2 * host.times.timeout * 1000)

	local tcp = genericpkt(host)

	for i = 1, numtrips do
		for j, port in ipairs(qscanports) do

			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

			start = stdnse.clock_us()

			try(sock:ip_send(tcp.buf, host))

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

			local test = bin.pack('AA=S=S', tcp.ip_bin_src, tcp.ip_bin_dst, tcp.tcp_sport, tcp.tcp_dport)
			local status, length, _, layer3, stop = pcap:pcap_receive()
			while status and test ~= check(layer3) do
				status, length, _, layer3, stop = pcap:pcap_receive()
			end

			if not stop then
				-- probably a timeout, just grab current time
				stop = stdnse.clock_us()
			else
				-- we use usecs
				stop = stop * 1000000
			end

			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
					stdnse.sleep(((delay / 2) + math.random(0, delay) - rtt))
				else
					stdnse.sleep(math.random((3 * delay) / 2 - rtt))
				end
			end
		end
	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

