146 lines
4.9 KiB
Python
146 lines
4.9 KiB
Python
# $Id$
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#
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# Copyright (C) 2005 Gregory P. Smith (greg@krypto.org)
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# Licensed to PSF under a Contributor Agreement.
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#
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__doc__ = """hashlib module - A common interface to many hash functions.
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new(name, string='') - returns a new hash object implementing the
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given hash function; initializing the hash
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using the given string data.
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Named constructor functions are also available, these are much faster
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than using new():
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md5(), sha1(), sha224(), sha256(), sha384(), and sha512()
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More algorithms may be available on your platform but the above are
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guaranteed to exist.
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NOTE: If you want the adler32 or crc32 hash functions they are available in
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the zlib module.
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Choose your hash function wisely. Some have known collision weaknesses.
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sha384 and sha512 will be slow on 32 bit platforms.
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Hash objects have these methods:
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- update(arg): Update the hash object with the string arg. Repeated calls
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are equivalent to a single call with the concatenation of all
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the arguments.
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- digest(): Return the digest of the strings passed to the update() method
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so far. This may contain non-ASCII characters, including
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NUL bytes.
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- hexdigest(): Like digest() except the digest is returned as a string of
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double length, containing only hexadecimal digits.
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- copy(): Return a copy (clone) of the hash object. This can be used to
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efficiently compute the digests of strings that share a common
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initial substring.
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For example, to obtain the digest of the string 'Nobody inspects the
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spammish repetition':
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>>> import hashlib
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>>> m = hashlib.md5()
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>>> m.update("Nobody inspects")
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>>> m.update(" the spammish repetition")
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>>> m.digest()
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'\\xbbd\\x9c\\x83\\xdd\\x1e\\xa5\\xc9\\xd9\\xde\\xc9\\xa1\\x8d\\xf0\\xff\\xe9'
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More condensed:
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>>> hashlib.sha224("Nobody inspects the spammish repetition").hexdigest()
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'a4337bc45a8fc544c03f52dc550cd6e1e87021bc896588bd79e901e2'
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"""
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# This tuple and __get_builtin_constructor() must be modified if a new
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# always available algorithm is added.
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__always_supported = ('md5', 'sha1', 'sha224', 'sha256', 'sha384', 'sha512')
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algorithms = __always_supported
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__all__ = __always_supported + ('new', 'algorithms')
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def __get_builtin_constructor(name):
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try:
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if name in ('SHA1', 'sha1'):
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import _sha
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return _sha.new
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elif name in ('MD5', 'md5'):
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import _md5
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return _md5.new
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elif name in ('SHA256', 'sha256', 'SHA224', 'sha224'):
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import _sha256
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bs = name[3:]
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if bs == '256':
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return _sha256.sha256
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elif bs == '224':
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return _sha256.sha224
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elif name in ('SHA512', 'sha512', 'SHA384', 'sha384'):
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import _sha512
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bs = name[3:]
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if bs == '512':
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return _sha512.sha512
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elif bs == '384':
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return _sha512.sha384
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except ImportError:
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pass # no extension module, this hash is unsupported.
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raise ValueError('unsupported hash type ' + name)
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def __get_openssl_constructor(name):
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try:
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f = getattr(_hashlib, 'openssl_' + name)
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# Allow the C module to raise ValueError. The function will be
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# defined but the hash not actually available thanks to OpenSSL.
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f()
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# Use the C function directly (very fast)
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return f
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except (AttributeError, ValueError):
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return __get_builtin_constructor(name)
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def __py_new(name, string=''):
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"""new(name, string='') - Return a new hashing object using the named algorithm;
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optionally initialized with a string.
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"""
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return __get_builtin_constructor(name)(string)
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def __hash_new(name, string=''):
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"""new(name, string='') - Return a new hashing object using the named algorithm;
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optionally initialized with a string.
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"""
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try:
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return _hashlib.new(name, string)
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except ValueError:
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# If the _hashlib module (OpenSSL) doesn't support the named
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# hash, try using our builtin implementations.
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# This allows for SHA224/256 and SHA384/512 support even though
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# the OpenSSL library prior to 0.9.8 doesn't provide them.
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return __get_builtin_constructor(name)(string)
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try:
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import _hashlib
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new = __hash_new
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__get_hash = __get_openssl_constructor
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except ImportError:
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new = __py_new
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__get_hash = __get_builtin_constructor
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for __func_name in __always_supported:
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# try them all, some may not work due to the OpenSSL
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# version not supporting that algorithm.
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try:
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globals()[__func_name] = __get_hash(__func_name)
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except ValueError:
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import logging
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logging.exception('code for hash %s was not found.', __func_name)
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# Cleanup locals()
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del __always_supported, __func_name, __get_hash
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del __py_new, __hash_new, __get_openssl_constructor
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