1 # $Id$ 2 # 3 # Copyright (C) 2005 Gregory P. Smith (greg (at] 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 # This tuple and __get_builtin_constructor() must be modified if a new 58 # always available algorithm is added. 59 __always_supported = ('md5', 'sha1', 'sha224', 'sha256', 'sha384', 'sha512') 60 61 algorithms = __always_supported 62 63 __all__ = __always_supported + ('new', 'algorithms') 64 65 66 def __get_builtin_constructor(name): 67 try: 68 if name in ('SHA1', 'sha1'): 69 import _sha 70 return _sha.new 71 elif name in ('MD5', 'md5'): 72 import _md5 73 return _md5.new 74 elif name in ('SHA256', 'sha256', 'SHA224', 'sha224'): 75 import _sha256 76 bs = name[3:] 77 if bs == '256': 78 return _sha256.sha256 79 elif bs == '224': 80 return _sha256.sha224 81 elif name in ('SHA512', 'sha512', 'SHA384', 'sha384'): 82 import _sha512 83 bs = name[3:] 84 if bs == '512': 85 return _sha512.sha512 86 elif bs == '384': 87 return _sha512.sha384 88 except ImportError: 89 pass # no extension module, this hash is unsupported. 90 91 raise ValueError('unsupported hash type ' + name) 92 93 94 def __get_openssl_constructor(name): 95 try: 96 f = getattr(_hashlib, 'openssl_' + name) 97 # Allow the C module to raise ValueError. The function will be 98 # defined but the hash not actually available thanks to OpenSSL. 99 f() 100 # Use the C function directly (very fast) 101 return f 102 except (AttributeError, ValueError): 103 return __get_builtin_constructor(name) 104 105 106 def __py_new(name, string=''): 107 """new(name, string='') - Return a new hashing object using the named algorithm; 108 optionally initialized with a string. 109 """ 110 return __get_builtin_constructor(name)(string) 111 112 113 def __hash_new(name, string=''): 114 """new(name, string='') - Return a new hashing object using the named algorithm; 115 optionally initialized with a string. 116 """ 117 try: 118 return _hashlib.new(name, string) 119 except ValueError: 120 # If the _hashlib module (OpenSSL) doesn't support the named 121 # hash, try using our builtin implementations. 122 # This allows for SHA224/256 and SHA384/512 support even though 123 # the OpenSSL library prior to 0.9.8 doesn't provide them. 124 return __get_builtin_constructor(name)(string) 125 126 127 try: 128 import _hashlib 129 new = __hash_new 130 __get_hash = __get_openssl_constructor 131 except ImportError: 132 new = __py_new 133 __get_hash = __get_builtin_constructor 134 135 for __func_name in __always_supported: 136 # try them all, some may not work due to the OpenSSL 137 # version not supporting that algorithm. 138 try: 139 globals()[__func_name] = __get_hash(__func_name) 140 except ValueError: 141 import logging 142 logging.exception('code for hash %s was not found.', __func_name) 143 144 # Cleanup locals() 145 del __always_supported, __func_name, __get_hash 146 del __py_new, __hash_new, __get_openssl_constructor 147
