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annotate Lib/hmac.py @ 25838:8540887bcec6 2.2

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Backport of 2.183: Fix memory leak in add_subclass() found by NealN with valgrind.
author Guido van Rossum <guido@python.org>
date Fri, 18 Oct 2002 13:42:21 +0000
parents bb8716095a81
children c3a67ce58245
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19862
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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
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6 import string
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7
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8 def _strxor(s1, s2):
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9 """Utility method. XOR the two strings s1 and s2 (must have same length).
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10 """
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11 return "".join(map(lambda x, y: chr(ord(x) ^ ord(y)), s1, s2))
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12
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13 # The size of the digests returned by HMAC depends on the underlying
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14 # hashing module used.
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15 digest_size = None
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16
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17 class HMAC:
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18 """RFC2104 HMAC class.
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19
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20 This supports the API for Cryptographic Hash Functions (PEP 247).
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21 """
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22
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23 def __init__(self, key, msg = None, digestmod = None):
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24 """Create a new HMAC object.
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25
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26 key: key for the keyed hash object.
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27 msg: Initial input for the hash, if provided.
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28 digestmod: A module supporting PEP 247. Defaults to the md5 module.
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29 """
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30 if digestmod == None:
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31 import md5
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32 digestmod = md5
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33
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34 self.digestmod = digestmod
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35 self.outer = digestmod.new()
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36 self.inner = digestmod.new()
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37 self.digest_size = digestmod.digest_size
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38
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39 blocksize = 64
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40 ipad = "\x36" * blocksize
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41 opad = "\x5C" * blocksize
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42
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43 if len(key) > blocksize:
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44 key = digestmod.new(key).digest()
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45
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46 key = key + chr(0) * (blocksize - len(key))
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47 self.outer.update(_strxor(key, opad))
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48 self.inner.update(_strxor(key, ipad))
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49 if (msg):
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50 self.update(msg)
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51
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52 ## def clear(self):
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53 ## raise NotImplementedError, "clear() method not available in HMAC."
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54
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55 def update(self, msg):
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56 """Update this hashing object with the string msg.
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57 """
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58 self.inner.update(msg)
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59
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60 def copy(self):
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61 """Return a separate copy of this hashing object.
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62
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63 An update to this copy won't affect the original object.
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64 """
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65 other = HMAC("")
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66 other.digestmod = self.digestmod
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67 other.inner = self.inner.copy()
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68 other.outer = self.outer.copy()
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69 return other
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70
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71 def digest(self):
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72 """Return the hash value of this hashing object.
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73
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74 This returns a string containing 8-bit data. The object is
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75 not altered in any way by this function; you can continue
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76 updating the object after calling this function.
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77 """
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78 h = self.outer.copy()
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79 h.update(self.inner.digest())
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80 return h.digest()
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81
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82 def hexdigest(self):
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83 """Like digest(), but returns a string of hexadecimal digits instead.
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84 """
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85 return "".join([string.zfill(hex(ord(x))[2:], 2)
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86 for x in tuple(self.digest())])
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87
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88 def new(key, msg = None, digestmod = None):
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89 """Create a new hashing object and return it.
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90
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91 key: The starting key for the hash.
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92 msg: if available, will immediately be hashed into the object's starting
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93 state.
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94
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95 You can now feed arbitrary strings into the object using its update()
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96 method, and can ask for the hash value at any time by calling its digest()
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97 method.
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98 """
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99 return HMAC(key, msg, digestmod)