1 # $Id: hashlib.py 66093 2008-08-31 16:34:18Z gregory.p.smith $

     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')