100 lines
3.0 KiB
Python
100 lines
3.0 KiB
Python
"""HMAC (Keyed-Hashing for Message Authentication) Python module.
|
|
|
|
Implements the HMAC algorithm as described by RFC 2104.
|
|
"""
|
|
|
|
import string
|
|
|
|
def _strxor(s1, s2):
|
|
"""Utility method. XOR the two strings s1 and s2 (must have same length).
|
|
"""
|
|
return "".join(map(lambda x, y: chr(ord(x) ^ ord(y)), s1, s2))
|
|
|
|
# The size of the digests returned by HMAC depends on the underlying
|
|
# hashing module used.
|
|
digest_size = None
|
|
|
|
class HMAC:
|
|
"""RFC2104 HMAC class.
|
|
|
|
This supports the API for Cryptographic Hash Functions (PEP 247).
|
|
"""
|
|
|
|
def __init__(self, key, msg = None, digestmod = None):
|
|
"""Create a new HMAC object.
|
|
|
|
key: key for the keyed hash object.
|
|
msg: Initial input for the hash, if provided.
|
|
digestmod: A module supporting PEP 247. Defaults to the md5 module.
|
|
"""
|
|
if digestmod == None:
|
|
import md5
|
|
digestmod = md5
|
|
|
|
self.digestmod = digestmod
|
|
self.outer = digestmod.new()
|
|
self.inner = digestmod.new()
|
|
self.digest_size = digestmod.digest_size
|
|
|
|
blocksize = 64
|
|
ipad = "\x36" * blocksize
|
|
opad = "\x5C" * blocksize
|
|
|
|
if len(key) > blocksize:
|
|
key = digestmod.new(key).digest()
|
|
|
|
key = key + chr(0) * (blocksize - len(key))
|
|
self.outer.update(_strxor(key, opad))
|
|
self.inner.update(_strxor(key, ipad))
|
|
if (msg):
|
|
self.update(msg)
|
|
|
|
## def clear(self):
|
|
## raise NotImplementedError, "clear() method not available in HMAC."
|
|
|
|
def update(self, msg):
|
|
"""Update this hashing object with the string msg.
|
|
"""
|
|
self.inner.update(msg)
|
|
|
|
def copy(self):
|
|
"""Return a separate copy of this hashing object.
|
|
|
|
An update to this copy won't affect the original object.
|
|
"""
|
|
other = HMAC("")
|
|
other.digestmod = self.digestmod
|
|
other.inner = self.inner.copy()
|
|
other.outer = self.outer.copy()
|
|
return other
|
|
|
|
def digest(self):
|
|
"""Return the hash value of this hashing object.
|
|
|
|
This returns a string containing 8-bit data. The object is
|
|
not altered in any way by this function; you can continue
|
|
updating the object after calling this function.
|
|
"""
|
|
h = self.outer.copy()
|
|
h.update(self.inner.digest())
|
|
return h.digest()
|
|
|
|
def hexdigest(self):
|
|
"""Like digest(), but returns a string of hexadecimal digits instead.
|
|
"""
|
|
return "".join([string.zfill(hex(ord(x))[2:], 2)
|
|
for x in tuple(self.digest())])
|
|
|
|
def new(key, msg = None, digestmod = None):
|
|
"""Create a new hashing object and return it.
|
|
|
|
key: The starting key for the hash.
|
|
msg: if available, will immediately be hashed into the object's starting
|
|
state.
|
|
|
|
You can now feed arbitrary strings into the object using its update()
|
|
method, and can ask for the hash value at any time by calling its digest()
|
|
method.
|
|
"""
|
|
return HMAC(key, msg, digestmod)
|