text: #!/usr/bin/env python
  
  # Copyright (c) 2014 clowwindy
  #
  # Permission is hereby granted, free of charge, to any person obtaining a copy
  # of this software and associated documentation files (the "Software"), to deal
  # in the Software without restriction, including without limitation the rights
  # to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
  # copies of the Software, and to permit persons to whom the Software is
  # furnished to do so, subject to the following conditions:
  #
  # The above copyright notice and this permission notice shall be included in
  # all copies or substantial portions of the Software.
  #
  # THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
  # IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
  # FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
  # AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
  # LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
  # OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
  # SOFTWARE.
  
  from __future__ import absolute_import, division, print_function, \
      with_statement
  
  import sys
  import xlog
  
  __all__ = ['ciphers']
  
  has_m2 = True
  try:
      __import__('M2Crypto')
  except ImportError:
      has_m2 = False
  
  
  def create_cipher(alg, key, iv, op, key_as_bytes=0, d=None, salt=None, i=1,
                    padding=1):
  
      import M2Crypto.EVP
      return M2Crypto.EVP.Cipher(alg.replace('-', '_'), key, iv, op,
                                 key_as_bytes=0, d='md5', salt=None, i=1,
                                 padding=1)
  
  
  def err(alg, key, iv, op, key_as_bytes=0, d=None, salt=None, i=1, padding=1):
      xlog.error(('M2Crypto is required to use %s, please run'
                     ' `apt-get install python-m2crypto`') % alg)
      sys.exit(1)
  
  
  if has_m2:
      ciphers = {
          b'aes-128-cfb': (16, 16, create_cipher),
          b'aes-192-cfb': (24, 16, create_cipher),
          b'aes-256-cfb': (32, 16, create_cipher),
          b'bf-cfb': (16, 8, create_cipher),
          b'camellia-128-cfb': (16, 16, create_cipher),
          b'camellia-192-cfb': (24, 16, create_cipher),
          b'camellia-256-cfb': (32, 16, create_cipher),
          b'cast5-cfb': (16, 8, create_cipher),
          b'des-cfb': (8, 8, create_cipher),
          b'idea-cfb': (16, 8, create_cipher),
          b'rc2-cfb': (16, 8, create_cipher),
          b'rc4': (16, 0, create_cipher),
          b'seed-cfb': (16, 16, create_cipher),
      }
  else:
      ciphers = {}
  
  
  def run_method(method):
      from shadowsocks.crypto import util
  
      cipher = create_cipher(method, b'k' * 32, b'i' * 16, 1)
      decipher = create_cipher(method, b'k' * 32, b'i' * 16, 0)
  
      util.run_cipher(cipher, decipher)
  
  
  def check_env():
      # skip this test on pypy and Python 3
      try:
          import __pypy__
          del __pypy__
          from nose.plugins.skip import SkipTest
          raise SkipTest
      except ImportError:
          pass
      if bytes != str:
          from nose.plugins.skip import SkipTest
          raise SkipTest
  
  
  def test_aes_128_cfb():
      check_env()
      run_method(b'aes-128-cfb')
  
  
  def test_aes_256_cfb():
      check_env()
      run_method(b'aes-256-cfb')
  
  
  def test_bf_cfb():
      check_env()
      run_method(b'bf-cfb')
  
  
  def test_rc4():
      check_env()
      run_method(b'rc4')
  
  
  if __name__ == '__main__':
      test_aes_128_cfb()
  