1 # $Id: hashlib.py 52533 2006-10-29 18:01:12Z georg.brandl $

     2 #

     3 #  Copyright (C) 2005   Gregory P. Smith (greg@electricrain.com)

     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 Choose your hash function wisely.  Some have known collision weaknesses.

    22 sha384 and sha512 will be slow on 32 bit platforms.

    23 

    24 Hash objects have these methods:

    25  - update(arg): Update the hash object with the string arg. Repeated calls

    26                 are equivalent to a single call with the concatenation of all

    27                 the arguments.

    28  - digest():    Return the digest of the strings passed to the update() method

    29                 so far. This may contain non-ASCII characters, including

    30                 NUL bytes.

    31  - hexdigest(): Like digest() except the digest is returned as a string of

    32                 double length, containing only hexadecimal digits.

    33  - copy():      Return a copy (clone) of the hash object. This can be used to

    34                 efficiently compute the digests of strings that share a common

    35                 initial substring.

    36 

    37 For example, to obtain the digest of the string 'Nobody inspects the

    38 spammish repetition':

    39 

    40     >>> import hashlib

    41     >>> m = hashlib.md5()

    42     >>> m.update("Nobody inspects")

    43     >>> m.update(" the spammish repetition")

    44     >>> m.digest()

    45     '\xbbd\x9c\x83\xdd\x1e\xa5\xc9\xd9\xde\xc9\xa1\x8d\xf0\xff\xe9'

    46 

    47 More condensed:

    48 

    49     >>> hashlib.sha224("Nobody inspects the spammish repetition").hexdigest()

    50     'a4337bc45a8fc544c03f52dc550cd6e1e87021bc896588bd79e901e2'

    51 

    52 """

    53 

    54 

    55 def __get_builtin_constructor(name):

    56     if name in ('SHA1', 'sha1'):

    57         import _sha

    58         return _sha.new

    59     elif name in ('MD5', 'md5'):

    60         import _md5

    61         return _md5.new

    62     elif name in ('SHA256', 'sha256', 'SHA224', 'sha224'):

    63         import _sha256

    64         bs = name[3:]

    65         if bs == '256':

    66             return _sha256.sha256

    67         elif bs == '224':

    68             return _sha256.sha224

    69     elif name in ('SHA512', 'sha512', 'SHA384', 'sha384'):

    70         import _sha512

    71         bs = name[3:]

    72         if bs == '512':

    73             return _sha512.sha512

    74         elif bs == '384':

    75             return _sha512.sha384

    76 

    77     raise ValueError, "unsupported hash type"

    78 

    79 

    80 def __py_new(name, string=''):

    81     """new(name, string='') - Return a new hashing object using the named algorithm;

    82     optionally initialized with a string.

    83     """

    84     return __get_builtin_constructor(name)(string)

    85 

    86 

    87 def __hash_new(name, string=''):

    88     """new(name, string='') - Return a new hashing object using the named algorithm;

    89     optionally initialized with a string.

    90     """

    91     try:

    92         return _hashlib.new(name, string)

    93     except ValueError:

    94         # If the _hashlib module (OpenSSL) doesn't support the named

    95         # hash, try using our builtin implementations.

    96         # This allows for SHA224/256 and SHA384/512 support even though

    97         # the OpenSSL library prior to 0.9.8 doesn't provide them.

    98         return __get_builtin_constructor(name)(string)

    99 

   100 

   101 try:

   102     import _hashlib

   103     # use the wrapper of the C implementation

   104     new = __hash_new

   105 

   106     for opensslFuncName in filter(lambda n: n.startswith('openssl_'), dir(_hashlib)):

   107         funcName = opensslFuncName[len('openssl_'):]

   108         try:

   109             # try them all, some may not work due to the OpenSSL

   110             # version not supporting that algorithm.

   111             f = getattr(_hashlib, opensslFuncName)

   112             f()

   113             # Use the C function directly (very fast)

   114             exec funcName + ' = f'

   115         except ValueError:

   116             try:

   117                 # Use the builtin implementation directly (fast)

   118                 exec funcName + ' = __get_builtin_constructor(funcName)'

   119             except ValueError:

   120                 # this one has no builtin implementation, don't define it

   121                 pass

   122     # clean up our locals

   123     del f

   124     del opensslFuncName

   125     del funcName

   126 

   127 except ImportError:

   128     # We don't have the _hashlib OpenSSL module?

   129     # use the built in legacy interfaces via a wrapper function

   130     new = __py_new

   131 

   132     # lookup the C function to use directly for the named constructors

   133     md5 = __get_builtin_constructor('md5')

   134     sha1 = __get_builtin_constructor('sha1')

   135     sha224 = __get_builtin_constructor('sha224')

   136     sha256 = __get_builtin_constructor('sha256')

   137     sha384 = __get_builtin_constructor('sha384')

   138     sha512 = __get_builtin_constructor('sha512')