Merged http-slowloris-check

CHANGELOG

@@ -1,5 +1,8 @@
 # Nmap Changelog ($Id$); -*-text-*-
 
+o [NSE] Added http-slowloris-check script which checks if the server is vulnerable
+  to a Slowloris DoS attack in a safe way. [Aleksandar Nikolic]
+
 o Removed pos_scan scan engine as the old implementation of RPC grind was the
   last scan type to use it. [Hani Benhabiles] 
 

nselib/http.lua

@@ -117,7 +117,7 @@ _ENV = stdnse.module("http", stdnse.seeall)
 ---Use ssl if we have it
 local have_ssl, openssl = pcall(require,'openssl')
 
-local USER_AGENT = stdnse.get_script_args('http.useragent') or "Mozilla/5.0 (compatible; Nmap Scripting Engine; http://nmap.org/book/nse.html)"
+USER_AGENT = stdnse.get_script_args('http.useragent') or "Mozilla/5.0 (compatible; Nmap Scripting Engine; http://nmap.org/book/nse.html)"
 local MAX_REDIRECT_COUNT = 5
 
 -- Recursively copy a table.

scripts/http-slowloris-check.nse

@@ -0,0 +1,147 @@
+local coroutine = require "coroutine"
+local math = require "math"
+local nmap = require "nmap"
+local shortport = require "shortport"
+local stdnse = require "stdnse"
+local comm = require "comm"
+local vulns = require "vulns"
+local http = require "http"
+
+
+description = [[
+Tests a web server for vulnerability to the Slowloris DoS attack.
+
+Slowloris was described at Defcon 17 by RSnake
+(see http://ha.ckers.org/slowloris/).
+
+This script opens two connections to the server, each without 
+the final CRLF. After 10 seconds, second connection sends 
+additional header. Both connections then wait for server timeout.
+If second connection gets a timeout 10 or more seconds after the
+first one, we can conclude that sending additional header prolonged
+it's timeout and that the server is vulnerable to slowloris DoS attack.
+
+You can specify custom http User-agent field with <code>http.useragent</code>
+script argument.
+
+Idea from Qualys blogpost:
+ * https://community.qualys.com/blogs/securitylabs/2011/07/07/identifying-slow-http-attack-vulnerabilities-on-web-applications
+ 
+]]
+
+---
+-- @usage
+-- nmap --script http-slowloris-check  <target>
+--
+-- @args http.useragent Specifies custom user agent string.
+--
+-- @output
+-- PORT   STATE SERVICE REASON
+-- 80/tcp open  http    syn-ack
+-- | http-slowloris-check:
+-- |   VULNERABLE:
+-- |   Slowloris DOS attack
+-- |     State: VULNERABLE
+-- |     Description:
+-- |       Slowloris tries to keep many connections to the target web server open and hold them open as long as possible.
+-- |       It accomplishes this by opening connections to the target web server and sending a partial request. By doing
+-- |       so, it starves the http server's resources causing Denial Of Service.
+-- |
+-- |     Disclosure date: 2009-09-17
+-- |     References:
+-- |_      http://ha.ckers.org/slowloris/
+
+author = "Aleksandar Nikolic"
+license = "Same as Nmap--See http://nmap.org/book/man-legal.html"
+categories = {"vuln", "safe"}
+
+
+portrule = shortport.http
+
+local HalfHTTP
+local Bestopt
+local TimeWithout -- time without additional headers
+local TimeWith 	  -- time with additional headers
+
+-- does a half http request and waits until timeout 
+local function slowThread1(host,port)
+	local socket,status
+	local catch = function()
+		TimeWithout = nmap.clock()
+	end
+	local try = nmap.new_try(catch)	
+	socket = nmap.new_socket()
+	socket:set_timeout(500 * 1000)
+	socket:connect(host.ip, port, Bestopt)
+	socket:send(HalfHTTP)
+	try(socket:receive())
+	TimeWithout = nmap.clock()
+end
+
+-- does a half http request but sends another 
+-- header value after 10 seconds
+local function slowThread2(host,port)
+	local socket,status
+	local catch = function()
+		-- note the time the socket timedout
+		TimeWith = nmap.clock()
+		stdnse.print_debug("2 try")
+	end
+	local try = nmap.new_try(catch)	
+	socket = nmap.new_socket()
+	socket:set_timeout(500 * 1000)
+	socket:connect(host.ip, port, Bestopt)
+	socket:send(HalfHTTP)
+	stdnse.sleep(10)	
+	socket:send("X-a: b\r\n")	
+	try(socket:receive())
+	TimeWith = nmap.clock()
+end
+
+action = function(host,port)
+
+	local slowloris  = {
+		title = "Slowloris DOS attack",
+		description = [[
+Slowloris tries to keep many connections to the target web server open and hold them open as long as possible.
+It accomplishes this by opening connections to the target web server and sending a partial request. By doing 
+so, it starves the http server's resources causing Denial Of Service. 
+		]],
+		references = {
+		  'http://ha.ckers.org/slowloris/',
+		},
+		dates = {
+		  disclosure = {year = '2009', month = '09', day = '17'},
+		},
+		exploit_results = {},
+	}	
+	
+	local report = vulns.Report:new(SCRIPT_NAME, host, port)
+	slowloris.state = vulns.STATE.NOT_VULN
+
+	_, _, Bestopt = comm.tryssl(host, port, "GET / \r\n\r\n", {}) -- first determine if we need ssl
+	HalfHTTP = "POST /" .. tostring(math.random(100000, 900000)) .. " HTTP/1.1\r\n" ..
+	                  "Host: " .. host.ip .. "\r\n" ..
+	                  "User-Agent: " .. http.USER_AGENT .. "\r\n; " ..
+	                  "Content-Length: 42\r\n"
+	-- both threads run at the same time
+	local thread1 = stdnse.new_thread(slowThread1, host, port)
+	local thread2 = stdnse.new_thread(slowThread2, host, port)
+	while true do -- wait for both threads to die 
+		if coroutine.status(thread1) == "dead" and  coroutine.status(thread2) == "dead" then
+			break
+		end
+		stdnse.sleep(1)
+	end
+	-- compare times
+	local diff = TimeWith - TimeWithout 
+	stdnse.print_debug("Time difference is: %d",diff)
+	-- if second connection died 10 or more seconds after the first 
+	-- it means that sending additional data prolonged the connection's time 
+	-- and the server is vulnerable to slowloris attack
+	if diff >= 10	then 
+		stdnse.print_debug("Difference is greater or equal to 10 seconds.")
+		slowloris.state = vulns.STATE.VULN
+	end
+	return report:make_output(slowloris)
+end

scripts/script.db

@@ -30,8 +30,8 @@ Entry { filename = "broadcast-dhcp-discover.nse", categories = { "broadcast", "s
 Entry { filename = "broadcast-dhcp6-discover.nse", categories = { "broadcast", "safe", } }
 Entry { filename = "broadcast-dns-service-discovery.nse", categories = { "broadcast", "safe", } }
 Entry { filename = "broadcast-dropbox-listener.nse", categories = { "broadcast", "safe", } }
-Entry { filename = "broadcast-eigrp-discovery.nse", categories = { "discovery", "broadcast", "safe", } }
+Entry { filename = "broadcast-eigrp-discovery.nse", categories = { "broadcast", "discovery", "safe", } }
-Entry { filename = "broadcast-igmp-discovery.nse", categories = { "discovery", "safe", "broadcast", } }
+Entry { filename = "broadcast-igmp-discovery.nse", categories = { "broadcast", "discovery", "safe", } }
 Entry { filename = "broadcast-listener.nse", categories = { "broadcast", "safe", } }
 Entry { filename = "broadcast-ms-sql-discover.nse", categories = { "broadcast", "safe", } }
 Entry { filename = "broadcast-netbios-master-browser.nse", categories = { "broadcast", "safe", } }
@@ -180,6 +180,7 @@ Entry { filename = "http-robots.txt.nse", categories = { "default", "discovery",
 Entry { filename = "http-robtex-reverse-ip.nse", categories = { "discovery", "external", "safe", } }
 Entry { filename = "http-robtex-shared-ns.nse", categories = { "discovery", "external", "safe", } }
 Entry { filename = "http-sitemap-generator.nse", categories = { "discovery", "intrusive", } }
+Entry { filename = "http-slowloris-check.nse", categories = { "safe", "vuln", } }
 Entry { filename = "http-slowloris.nse", categories = { "dos", "intrusive", } }
 Entry { filename = "http-sql-injection.nse", categories = { "intrusive", "vuln", } }
 Entry { filename = "http-title.nse", categories = { "default", "discovery", "safe", } }
@@ -251,8 +252,8 @@ Entry { filename = "modbus-discover.nse", categories = { "discovery", "intrusive
 Entry { filename = "mongodb-brute.nse", categories = { "brute", "intrusive", } }
 Entry { filename = "mongodb-databases.nse", categories = { "default", "discovery", "safe", } }
 Entry { filename = "mongodb-info.nse", categories = { "default", "discovery", "safe", } }
-Entry { filename = "mrinfo.nse", categories = { "discovery", "safe", "broadcast"} }
+Entry { filename = "mrinfo.nse", categories = { "broadcast", "discovery", "safe", } }
-Entry { filename = "mtrace.nse", categories = { "discovery", "safe", "broadcast"} }
+
 Entry { filename = "ms-sql-brute.nse", categories = { "brute", "intrusive", } }
 Entry { filename = "ms-sql-config.nse", categories = { "discovery", "safe", } }
 Entry { filename = "ms-sql-dac.nse", categories = { "discovery", "safe", } }
@@ -263,6 +264,7 @@ Entry { filename = "ms-sql-info.nse", categories = { "default", "discovery", "sa
 Entry { filename = "ms-sql-query.nse", categories = { "discovery", "safe", } }
 Entry { filename = "ms-sql-tables.nse", categories = { "discovery", "safe", } }
 Entry { filename = "ms-sql-xp-cmdshell.nse", categories = { "intrusive", } }
+Entry { filename = "mtrace.nse", categories = { "broadcast", "discovery", "safe", } }
 Entry { filename = "mysql-audit.nse", categories = { "discovery", "safe", } }
 Entry { filename = "mysql-brute.nse", categories = { "brute", "intrusive", } }
 Entry { filename = "mysql-databases.nse", categories = { "discovery", "intrusive", } }