[3] | 1 | """HMAC (Keyed-Hashing for Message Authentication) Python module. |
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| 2 | |
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| 3 | Implements the HMAC algorithm as described by RFC 2104. |
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| 4 | |
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| 5 | This is just a copy of the Python 2.2 HMAC module, modified to work when |
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| 6 | used on versions of Python before 2.2. |
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| 7 | """ |
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| 8 | |
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| 9 | __revision__ = "$Id: HMAC.py,v 1.5 2002/07/25 17:19:02 z3p Exp $" |
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| 10 | |
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| 11 | import string |
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| 12 | |
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| 13 | def _strxor(s1, s2): |
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| 14 | """Utility method. XOR the two strings s1 and s2 (must have same length). |
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| 15 | """ |
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| 16 | return "".join(map(lambda x, y: chr(ord(x) ^ ord(y)), s1, s2)) |
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| 17 | |
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| 18 | # The size of the digests returned by HMAC depends on the underlying |
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| 19 | # hashing module used. |
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| 20 | digest_size = None |
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| 21 | |
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| 22 | class HMAC: |
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| 23 | """RFC2104 HMAC class. |
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| 24 | |
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| 25 | This supports the API for Cryptographic Hash Functions (PEP 247). |
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| 26 | """ |
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| 27 | |
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| 28 | def __init__(self, key, msg = None, digestmod = None): |
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| 29 | """Create a new HMAC object. |
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| 30 | |
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| 31 | key: key for the keyed hash object. |
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| 32 | msg: Initial input for the hash, if provided. |
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| 33 | digestmod: A module supporting PEP 247. Defaults to the md5 module. |
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| 34 | """ |
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| 35 | if digestmod == None: |
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| 36 | import md5 |
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| 37 | digestmod = md5 |
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| 38 | |
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| 39 | self.digestmod = digestmod |
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| 40 | self.outer = digestmod.new() |
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| 41 | self.inner = digestmod.new() |
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| 42 | try: |
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| 43 | self.digest_size = digestmod.digest_size |
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| 44 | except AttributeError: |
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| 45 | self.digest_size = len(self.outer.digest()) |
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| 46 | |
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| 47 | blocksize = 64 |
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| 48 | ipad = "\x36" * blocksize |
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| 49 | opad = "\x5C" * blocksize |
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| 50 | |
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| 51 | if len(key) > blocksize: |
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| 52 | key = digestmod.new(key).digest() |
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| 53 | |
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| 54 | key = key + chr(0) * (blocksize - len(key)) |
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| 55 | self.outer.update(_strxor(key, opad)) |
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| 56 | self.inner.update(_strxor(key, ipad)) |
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| 57 | if (msg): |
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| 58 | self.update(msg) |
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| 59 | |
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| 60 | ## def clear(self): |
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| 61 | ## raise NotImplementedError, "clear() method not available in HMAC." |
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| 62 | |
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| 63 | def update(self, msg): |
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| 64 | """Update this hashing object with the string msg. |
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| 65 | """ |
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| 66 | self.inner.update(msg) |
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| 67 | |
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| 68 | def copy(self): |
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| 69 | """Return a separate copy of this hashing object. |
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| 70 | |
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| 71 | An update to this copy won't affect the original object. |
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| 72 | """ |
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| 73 | other = HMAC("") |
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| 74 | other.digestmod = self.digestmod |
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| 75 | other.inner = self.inner.copy() |
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| 76 | other.outer = self.outer.copy() |
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| 77 | return other |
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| 78 | |
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| 79 | def digest(self): |
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| 80 | """Return the hash value of this hashing object. |
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| 81 | |
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| 82 | This returns a string containing 8-bit data. The object is |
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| 83 | not altered in any way by this function; you can continue |
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| 84 | updating the object after calling this function. |
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| 85 | """ |
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| 86 | h = self.outer.copy() |
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| 87 | h.update(self.inner.digest()) |
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| 88 | return h.digest() |
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| 89 | |
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| 90 | def hexdigest(self): |
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| 91 | """Like digest(), but returns a string of hexadecimal digits instead. |
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| 92 | """ |
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| 93 | return "".join([string.zfill(hex(ord(x))[2:], 2) |
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| 94 | for x in tuple(self.digest())]) |
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| 95 | |
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| 96 | def new(key, msg = None, digestmod = None): |
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| 97 | """Create a new hashing object and return it. |
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| 98 | |
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| 99 | key: The starting key for the hash. |
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| 100 | msg: if available, will immediately be hashed into the object's starting |
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| 101 | state. |
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| 102 | |
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| 103 | You can now feed arbitrary strings into the object using its update() |
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| 104 | method, and can ask for the hash value at any time by calling its digest() |
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| 105 | method. |
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| 106 | """ |
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| 107 | return HMAC(key, msg, digestmod) |
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| 108 | |
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