Lib/hashlib.py

   1 # $Id$
   2 #
   3 #  Copyright (C) 2005   Gregory P. Smith (greg@krypto.org)
   4 #  Licensed to PSF under a Contributor Agreement.
   5 #
   6
   7 __doc__ = """hashlib module - A common interface to many hash functions.
   8
   9 new(name, string='') - returns a new hash object implementing the
  10                        given hash function; initializing the hash
  11                        using the given string data.
  12
  13 Named constructor functions are also available, these are much faster
  14 than using new():
  15
  16 md5(), sha1(), sha224(), sha256(), sha384(), and sha512()
  17
  18 More algorithms may be available on your platform but the above are
  19 guaranteed to exist.
  20
  21 NOTE: If you want the adler32 or crc32 hash functions they are available in
  22 the zlib module.
  23
  24 Choose your hash function wisely.  Some have known collision weaknesses.
  25 sha384 and sha512 will be slow on 32 bit platforms.
  26
  27 Hash objects have these methods:
  28  - update(arg): Update the hash object with the string arg. Repeated calls
  29                 are equivalent to a single call with the concatenation of all
  30                 the arguments.
  31  - digest():    Return the digest of the strings passed to the update() method
  32                 so far. This may contain non-ASCII characters, including
  33                 NUL bytes.
  34  - hexdigest(): Like digest() except the digest is returned as a string of
  35                 double length, containing only hexadecimal digits.
  36  - copy():      Return a copy (clone) of the hash object. This can be used to
  37                 efficiently compute the digests of strings that share a common
  38                 initial substring.
  39
  40 For example, to obtain the digest of the string 'Nobody inspects the
  41 spammish repetition':
  42
  43     >>> import hashlib
  44     >>> m = hashlib.md5()
  45     >>> m.update("Nobody inspects")
  46     >>> m.update(" the spammish repetition")
  47     >>> m.digest()
  48     '\\xbbd\\x9c\\x83\\xdd\\x1e\\xa5\\xc9\\xd9\\xde\\xc9\\xa1\\x8d\\xf0\\xff\\xe9'
  49
  50 More condensed:
  51
  52     >>> hashlib.sha224("Nobody inspects the spammish repetition").hexdigest()
  53     'a4337bc45a8fc544c03f52dc550cd6e1e87021bc896588bd79e901e2'
  54
  55 """
  56
  57
  58 def __get_builtin_constructor(name):
  59     if name in ('SHA1', 'sha1'):
  60         import _sha
  61         return _sha.new
  62     elif name in ('MD5', 'md5'):
  63         import _md5
  64         return _md5.new
  65     elif name in ('SHA256', 'sha256', 'SHA224', 'sha224'):
  66         import _sha256
  67         bs = name[3:]
  68         if bs == '256':
  69             return _sha256.sha256
  70         elif bs == '224':
  71             return _sha256.sha224
  72     elif name in ('SHA512', 'sha512', 'SHA384', 'sha384'):
  73         import _sha512
  74         bs = name[3:]
  75         if bs == '512':
  76             return _sha512.sha512
  77         elif bs == '384':
  78             return _sha512.sha384
  79
  80     raise ValueError, "unsupported hash type"
  81
  82
  83 def __py_new(name, string=''):
  84     """new(name, string='') - Return a new hashing object using the named algorithm;
  85     optionally initialized with a string.
  86     """
  87     return __get_builtin_constructor(name)(string)
  88
  89
  90 def __hash_new(name, string=''):
  91     """new(name, string='') - Return a new hashing object using the named algorithm;
  92     optionally initialized with a string.
  93     """
  94     try:
  95         return _hashlib.new(name, string)
  96     except ValueError:
  97         # If the _hashlib module (OpenSSL) doesn't support the named
  98         # hash, try using our builtin implementations.
  99         # This allows for SHA224/256 and SHA384/512 support even though
 100         # the OpenSSL library prior to 0.9.8 doesn't provide them.
 101         return __get_builtin_constructor(name)(string)
 102
 103
 104 try:
 105     import _hashlib
 106     # use the wrapper of the C implementation
 107     new = __hash_new
 108
 109     for opensslFuncName in filter(lambda n: n.startswith('openssl_'), dir(_hashlib)):
 110         funcName = opensslFuncName[len('openssl_'):]
 111         try:
 112             # try them all, some may not work due to the OpenSSL
 113             # version not supporting that algorithm.
 114             f = getattr(_hashlib, opensslFuncName)
 115             f()
 116             # Use the C function directly (very fast)
 117             exec funcName + ' = f'
 118         except ValueError:
 119             try:
 120                 # Use the builtin implementation directly (fast)
 121                 exec funcName + ' = __get_builtin_constructor(funcName)'
 122             except ValueError:
 123                 # this one has no builtin implementation, don't define it
 124                 pass
 125     # clean up our locals
 126     del f
 127     del opensslFuncName
 128     del funcName
 129
 130 except ImportError:
 131     # We don't have the _hashlib OpenSSL module?
 132     # use the built in legacy interfaces via a wrapper function
 133     new = __py_new
 134
 135     # lookup the C function to use directly for the named constructors
 136     md5 = __get_builtin_constructor('md5')
 137     sha1 = __get_builtin_constructor('sha1')
 138     sha224 = __get_builtin_constructor('sha224')
 139     sha256 = __get_builtin_constructor('sha256')
 140     sha384 = __get_builtin_constructor('sha384')
 141     sha512 = __get_builtin_constructor('sha512')