/gdata/tlslite/utils/hmac.py
Python | 104 lines | 94 code | 1 blank | 9 comment | 2 complexity | db9b1a48e4d95d87c10755bef5c1a9d3 MD5 | raw file
1"""HMAC (Keyed-Hashing for Message Authentication) Python module. 2 3Implements the HMAC algorithm as described by RFC 2104. 4 5(This file is modified from the standard library version to do faster 6copying) 7""" 8 9def _strxor(s1, s2): 10 """Utility method. XOR the two strings s1 and s2 (must have same length). 11 """ 12 return "".join(map(lambda x, y: chr(ord(x) ^ ord(y)), s1, s2)) 13 14# The size of the digests returned by HMAC depends on the underlying 15# hashing module used. 16digest_size = None 17 18class HMAC: 19 """RFC2104 HMAC class. 20 21 This supports the API for Cryptographic Hash Functions (PEP 247). 22 """ 23 24 def __init__(self, key, msg = None, digestmod = None): 25 """Create a new HMAC object. 26 27 key: key for the keyed hash object. 28 msg: Initial input for the hash, if provided. 29 digestmod: A module supporting PEP 247. Defaults to the md5 module. 30 """ 31 if digestmod is None: 32 import md5 33 digestmod = md5 34 35 if key == None: #TREVNEW - for faster copying 36 return #TREVNEW 37 38 self.digestmod = digestmod 39 self.outer = digestmod.new() 40 self.inner = digestmod.new() 41 self.digest_size = digestmod.digest_size 42 43 blocksize = 64 44 ipad = "\x36" * blocksize 45 opad = "\x5C" * blocksize 46 47 if len(key) > blocksize: 48 key = digestmod.new(key).digest() 49 50 key = key + chr(0) * (blocksize - len(key)) 51 self.outer.update(_strxor(key, opad)) 52 self.inner.update(_strxor(key, ipad)) 53 if msg is not None: 54 self.update(msg) 55 56## def clear(self): 57## raise NotImplementedError, "clear() method not available in HMAC." 58 59 def update(self, msg): 60 """Update this hashing object with the string msg. 61 """ 62 self.inner.update(msg) 63 64 def copy(self): 65 """Return a separate copy of this hashing object. 66 67 An update to this copy won't affect the original object. 68 """ 69 other = HMAC(None) #TREVNEW - for faster copying 70 other.digest_size = self.digest_size #TREVNEW 71 other.digestmod = self.digestmod 72 other.inner = self.inner.copy() 73 other.outer = self.outer.copy() 74 return other 75 76 def digest(self): 77 """Return the hash value of this hashing object. 78 79 This returns a string containing 8-bit data. The object is 80 not altered in any way by this function; you can continue 81 updating the object after calling this function. 82 """ 83 h = self.outer.copy() 84 h.update(self.inner.digest()) 85 return h.digest() 86 87 def hexdigest(self): 88 """Like digest(), but returns a string of hexadecimal digits instead. 89 """ 90 return "".join([hex(ord(x))[2:].zfill(2) 91 for x in tuple(self.digest())]) 92 93def new(key, msg = None, digestmod = None): 94 """Create a new hashing object and return it. 95 96 key: The starting key for the hash. 97 msg: if available, will immediately be hashed into the object's starting 98 state. 99 100 You can now feed arbitrary strings into the object using its update() 101 method, and can ask for the hash value at any time by calling its digest() 102 method. 103 """ 104 return HMAC(key, msg, digestmod)