lib/dnspython/dns/hash.py

   1 # Copyright (C) 2010 Nominum, Inc.
   2 #
   3 # Permission to use, copy, modify, and distribute this software and its
   4 # documentation for any purpose with or without fee is hereby granted,
   5 # provided that the above copyright notice and this permission notice
   6 # appear in all copies.
   7 #
   8 # THE SOFTWARE IS PROVIDED "AS IS" AND NOMINUM DISCLAIMS ALL WARRANTIES
   9 # WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
  10 # MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL NOMINUM BE LIABLE FOR
  11 # ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
  12 # WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
  13 # ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT
  14 # OF OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
  15
  16 """Hashing backwards compatibility wrapper"""
  17
  18 import sys
  19
  20 _hashes = None
  21
  22 def _need_later_python(alg):
  23     def func(*args, **kwargs):
  24         raise NotImplementedError("TSIG algorithm " + alg +
  25                                   " requires Python 2.5.2 or later")
  26     return func
  27
  28 def _setup():
  29     global _hashes
  30     _hashes = {}
  31     try:
  32         import hashlib
  33         _hashes['MD5'] = hashlib.md5
  34         _hashes['SHA1'] = hashlib.sha1
  35         _hashes['SHA224'] = hashlib.sha224
  36         _hashes['SHA256'] = hashlib.sha256
  37         if sys.hexversion >= 0x02050200:
  38             _hashes['SHA384'] = hashlib.sha384
  39             _hashes['SHA512'] = hashlib.sha512
  40         else:
  41             _hashes['SHA384'] = _need_later_python('SHA384')
  42             _hashes['SHA512'] = _need_later_python('SHA512')
  43
  44         if sys.hexversion < 0x02050000:
  45             # hashlib doesn't conform to PEP 247: API for
  46             # Cryptographic Hash Functions, which hmac before python
  47             # 2.5 requires, so add the necessary items.
  48             class HashlibWrapper:
  49                 def __init__(self, basehash):
  50                     self.basehash = basehash
  51                     self.digest_size = self.basehash().digest_size
  52
  53                 def new(self, *args, **kwargs):
  54                     return self.basehash(*args, **kwargs)
  55
  56             for name in _hashes:
  57                 _hashes[name] = HashlibWrapper(_hashes[name])
  58
  59     except ImportError:
  60         import md5, sha
  61         _hashes['MD5'] =  md5
  62         _hashes['SHA1'] = sha
  63
  64 def get(algorithm):
  65     if _hashes is None:
  66         _setup()
  67     return _hashes[algorithm.upper()]