Annotation of /trunk/ModularRex/ScriptEngines/Lib/hmac.py
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| 1 : | mikkopa | 52 | """HMAC (Keyed-Hashing for Message Authentication) Python module. |
| 2 : | |||
| 3 : | Implements the HMAC algorithm as described by RFC 2104. | ||
| 4 : | """ | ||
| 5 : | |||
| 6 : | def _strxor(s1, s2): | ||
| 7 : | """Utility method. XOR the two strings s1 and s2 (must have same length). | ||
| 8 : | """ | ||
| 9 : | return "".join(map(lambda x, y: chr(ord(x) ^ ord(y)), s1, s2)) | ||
| 10 : | |||
| 11 : | # The size of the digests returned by HMAC depends on the underlying | ||
| 12 : | # hashing module used. | ||
| 13 : | digest_size = None | ||
| 14 : | |||
| 15 : | # A unique object passed by HMAC.copy() to the HMAC constructor, in order | ||
| 16 : | # that the latter return very quickly. HMAC("") in contrast is quite | ||
| 17 : | # expensive. | ||
| 18 : | _secret_backdoor_key = [] | ||
| 19 : | |||
| 20 : | class HMAC: | ||
| 21 : | """RFC2104 HMAC class. | ||
| 22 : | |||
| 23 : | This supports the API for Cryptographic Hash Functions (PEP 247). | ||
| 24 : | """ | ||
| 25 : | |||
| 26 : | def __init__(self, key, msg = None, digestmod = None): | ||
| 27 : | """Create a new HMAC object. | ||
| 28 : | |||
| 29 : | key: key for the keyed hash object. | ||
| 30 : | msg: Initial input for the hash, if provided. | ||
| 31 : | digestmod: A module supporting PEP 247. Defaults to the md5 module. | ||
| 32 : | """ | ||
| 33 : | |||
| 34 : | if key is _secret_backdoor_key: # cheap | ||
| 35 : | return | ||
| 36 : | |||
| 37 : | if digestmod is None: | ||
| 38 : | import md5 | ||
| 39 : | digestmod = md5 | ||
| 40 : | |||
| 41 : | self.digestmod = digestmod | ||
| 42 : | self.outer = digestmod.new() | ||
| 43 : | self.inner = digestmod.new() | ||
| 44 : | self.digest_size = digestmod.digest_size | ||
| 45 : | |||
| 46 : | blocksize = 64 | ||
| 47 : | ipad = "\x36" * blocksize | ||
| 48 : | opad = "\x5C" * blocksize | ||
| 49 : | |||
| 50 : | if len(key) > blocksize: | ||
| 51 : | key = digestmod.new(key).digest() | ||
| 52 : | |||
| 53 : | key = key + chr(0) * (blocksize - len(key)) | ||
| 54 : | self.outer.update(_strxor(key, opad)) | ||
| 55 : | self.inner.update(_strxor(key, ipad)) | ||
| 56 : | if msg is not None: | ||
| 57 : | self.update(msg) | ||
| 58 : | |||
| 59 : | ## def clear(self): | ||
| 60 : | ## raise NotImplementedError, "clear() method not available in HMAC." | ||
| 61 : | |||
| 62 : | def update(self, msg): | ||
| 63 : | """Update this hashing object with the string msg. | ||
| 64 : | """ | ||
| 65 : | self.inner.update(msg) | ||
| 66 : | |||
| 67 : | def copy(self): | ||
| 68 : | """Return a separate copy of this hashing object. | ||
| 69 : | |||
| 70 : | An update to this copy won't affect the original object. | ||
| 71 : | """ | ||
| 72 : | other = HMAC(_secret_backdoor_key) | ||
| 73 : | other.digestmod = self.digestmod | ||
| 74 : | other.digest_size = self.digest_size | ||
| 75 : | other.inner = self.inner.copy() | ||
| 76 : | other.outer = self.outer.copy() | ||
| 77 : | return other | ||
| 78 : | |||
| 79 : | def digest(self): | ||
| 80 : | """Return the hash value of this hashing object. | ||
| 81 : | |||
| 82 : | This returns a string containing 8-bit data. The object is | ||
| 83 : | not altered in any way by this function; you can continue | ||
| 84 : | updating the object after calling this function. | ||
| 85 : | """ | ||
| 86 : | h = self.outer.copy() | ||
| 87 : | h.update(self.inner.digest()) | ||
| 88 : | return h.digest() | ||
| 89 : | |||
| 90 : | def hexdigest(self): | ||
| 91 : | """Like digest(), but returns a string of hexadecimal digits instead. | ||
| 92 : | """ | ||
| 93 : | return "".join([hex(ord(x))[2:].zfill(2) | ||
| 94 : | for x in tuple(self.digest())]) | ||
| 95 : | |||
| 96 : | def new(key, msg = None, digestmod = None): | ||
| 97 : | """Create a new hashing object and return it. | ||
| 98 : | |||
| 99 : | key: The starting key for the hash. | ||
| 100 : | msg: if available, will immediately be hashed into the object's starting | ||
| 101 : | state. | ||
| 102 : | |||
| 103 : | You can now feed arbitrary strings into the object using its update() | ||
| 104 : | method, and can ask for the hash value at any time by calling its digest() | ||
| 105 : | method. | ||
| 106 : | """ | ||
| 107 : | return HMAC(key, msg, digestmod) |
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