132 lines
4.3 KiB
Python
132 lines
4.3 KiB
Python
"""HMAC (Keyed-Hashing for Message Authentication) Python module.
|
|
|
|
Implements the HMAC algorithm as described by RFC 2104.
|
|
"""
|
|
|
|
import warnings as _warnings
|
|
from _operator import _compare_digest as compare_digest
|
|
|
|
trans_5C = bytes((x ^ 0x5C) for x in range(256))
|
|
trans_36 = bytes((x ^ 0x36) for x in range(256))
|
|
|
|
# The size of the digests returned by HMAC depends on the underlying
|
|
# hashing module used. Use digest_size from the instance of HMAC instead.
|
|
digest_size = None
|
|
|
|
|
|
|
|
class HMAC:
|
|
"""RFC 2104 HMAC class. Also complies with RFC 4231.
|
|
|
|
This supports the API for Cryptographic Hash Functions (PEP 247).
|
|
"""
|
|
blocksize = 64 # 512-bit HMAC; can be changed in subclasses.
|
|
|
|
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. *OR*
|
|
A hashlib constructor returning a new hash object.
|
|
Defaults to hashlib.md5.
|
|
|
|
Note: key and msg must be bytes objects.
|
|
"""
|
|
|
|
if not isinstance(key, bytes):
|
|
raise TypeError("key: expected bytes, but got %r" % type(key).__name__)
|
|
|
|
if digestmod is None:
|
|
import hashlib
|
|
digestmod = hashlib.md5
|
|
|
|
if callable(digestmod):
|
|
self.digest_cons = digestmod
|
|
else:
|
|
self.digest_cons = lambda d=b'': digestmod.new(d)
|
|
|
|
self.outer = self.digest_cons()
|
|
self.inner = self.digest_cons()
|
|
self.digest_size = self.inner.digest_size
|
|
|
|
if hasattr(self.inner, 'block_size'):
|
|
blocksize = self.inner.block_size
|
|
if blocksize < 16:
|
|
_warnings.warn('block_size of %d seems too small; using our '
|
|
'default of %d.' % (blocksize, self.blocksize),
|
|
RuntimeWarning, 2)
|
|
blocksize = self.blocksize
|
|
else:
|
|
_warnings.warn('No block_size attribute on given digest object; '
|
|
'Assuming %d.' % (self.blocksize),
|
|
RuntimeWarning, 2)
|
|
blocksize = self.blocksize
|
|
|
|
if len(key) > blocksize:
|
|
key = self.digest_cons(key).digest()
|
|
|
|
key = key + bytes(blocksize - len(key))
|
|
self.outer.update(key.translate(trans_5C))
|
|
self.inner.update(key.translate(trans_36))
|
|
if msg is not None:
|
|
self.update(msg)
|
|
|
|
def update(self, msg):
|
|
"""Update this hashing object with the string msg.
|
|
"""
|
|
if not isinstance(msg, bytes):
|
|
raise TypeError("expected bytes, but got %r" % type(msg).__name__)
|
|
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.
|
|
"""
|
|
# Call __new__ directly to avoid the expensive __init__.
|
|
other = self.__class__.__new__(self.__class__)
|
|
other.digest_cons = self.digest_cons
|
|
other.digest_size = self.digest_size
|
|
other.inner = self.inner.copy()
|
|
other.outer = self.outer.copy()
|
|
return other
|
|
|
|
def _current(self):
|
|
"""Return a hash object for the current state.
|
|
|
|
To be used only internally with digest() and hexdigest().
|
|
"""
|
|
h = self.outer.copy()
|
|
h.update(self.inner.digest())
|
|
return h
|
|
|
|
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._current()
|
|
return h.digest()
|
|
|
|
def hexdigest(self):
|
|
"""Like digest(), but returns a string of hexadecimal digits instead.
|
|
"""
|
|
h = self._current()
|
|
return h.hexdigest()
|
|
|
|
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)
|