212 lines
7.1 KiB
Python
212 lines
7.1 KiB
Python
# HMAC.py - Implements the HMAC algorithm as described by RFC 2104.
|
|
#
|
|
# ===================================================================
|
|
# Portions Copyright (c) 2001, 2002, 2003 Python Software Foundation;
|
|
# All Rights Reserved
|
|
#
|
|
# This file contains code from the Python 2.2 hmac.py module (the
|
|
# "Original Code"), with modifications made after it was incorporated
|
|
# into PyCrypto (the "Modifications").
|
|
#
|
|
# To the best of our knowledge, the Python Software Foundation is the
|
|
# copyright holder of the Original Code, and has licensed it under the
|
|
# Python 2.2 license. See the file LEGAL/copy/LICENSE.python-2.2 for
|
|
# details.
|
|
#
|
|
# The Modifications to this file are dedicated to the public domain.
|
|
# To the extent that dedication to the public domain is not available,
|
|
# everyone is granted a worldwide, perpetual, royalty-free,
|
|
# non-exclusive license to exercise all rights associated with the
|
|
# contents of this file for any purpose whatsoever. No rights are
|
|
# reserved.
|
|
#
|
|
# THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
|
|
# EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
|
|
# MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
|
|
# NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS
|
|
# BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN
|
|
# ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
|
|
# CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
|
|
# SOFTWARE.
|
|
# ===================================================================
|
|
|
|
|
|
"""HMAC (Hash-based Message Authentication Code) algorithm
|
|
|
|
HMAC is a MAC defined in RFC2104_ and FIPS-198_ and constructed using
|
|
a cryptograpic hash algorithm.
|
|
It is usually named *HMAC-X*, where *X* is the hash algorithm; for
|
|
instance *HMAC-SHA1* or *HMAC-MD5*.
|
|
|
|
The strength of an HMAC depends on:
|
|
|
|
- the strength of the hash algorithm
|
|
- the length and entropy of the secret key
|
|
|
|
An example of possible usage is the following:
|
|
|
|
>>> from Crypto.Hash import HMAC
|
|
>>>
|
|
>>> secret = b'Swordfish'
|
|
>>> h = HMAC.new(secret)
|
|
>>> h.update(b'Hello')
|
|
>>> print h.hexdigest()
|
|
|
|
.. _RFC2104: http://www.ietf.org/rfc/rfc2104.txt
|
|
.. _FIPS-198: http://csrc.nist.gov/publications/fips/fips198/fips-198a.pdf
|
|
"""
|
|
|
|
# This is just a copy of the Python 2.2 HMAC module, modified to work when
|
|
# used on versions of Python before 2.2.
|
|
|
|
__revision__ = "$Id$"
|
|
|
|
__all__ = ['new', 'digest_size', 'HMAC' ]
|
|
|
|
from Crypto.Util.strxor import strxor_c
|
|
from Crypto.Util.py3compat import *
|
|
|
|
#: The size of the authentication tag produced by the MAC.
|
|
#: It matches the digest size on the underlying
|
|
#: hashing module used.
|
|
digest_size = None
|
|
|
|
class HMAC:
|
|
"""Class that implements HMAC"""
|
|
|
|
#: The size of the authentication tag produced by the MAC.
|
|
#: It matches the digest size on the underlying
|
|
#: hashing module used.
|
|
digest_size = None
|
|
|
|
def __init__(self, key, msg = None, digestmod = None):
|
|
"""Create a new HMAC object.
|
|
|
|
:Parameters:
|
|
key : byte string
|
|
secret key for the MAC object.
|
|
It must be long enough to match the expected security level of the
|
|
MAC. However, there is no benefit in using keys longer than the
|
|
`digest_size` of the underlying hash algorithm.
|
|
msg : byte string
|
|
The very first chunk of the message to authenticate.
|
|
It is equivalent to an early call to `update()`. Optional.
|
|
:Parameter digestmod:
|
|
The hash algorithm the HMAC is based on.
|
|
Default is `Crypto.Hash.MD5`.
|
|
:Type digestmod:
|
|
A hash module or object instantiated from `Crypto.Hash`
|
|
"""
|
|
if digestmod is None:
|
|
from . import MD5
|
|
digestmod = MD5
|
|
|
|
self.digestmod = digestmod
|
|
self.outer = digestmod.new()
|
|
self.inner = digestmod.new()
|
|
try:
|
|
self.digest_size = digestmod.digest_size
|
|
except AttributeError:
|
|
self.digest_size = len(self.outer.digest())
|
|
|
|
try:
|
|
# The block size is 128 bytes for SHA384 and SHA512 and 64 bytes
|
|
# for the others hash function
|
|
blocksize = digestmod.block_size
|
|
except AttributeError:
|
|
blocksize = 64
|
|
|
|
ipad = 0x36
|
|
opad = 0x5C
|
|
|
|
if len(key) > blocksize:
|
|
key = digestmod.new(key).digest()
|
|
|
|
key = key + bchr(0) * (blocksize - len(key))
|
|
self.outer.update(strxor_c(key, opad))
|
|
self.inner.update(strxor_c(key, ipad))
|
|
if (msg):
|
|
self.update(msg)
|
|
|
|
def update(self, msg):
|
|
"""Continue authentication of a message by consuming the next chunk of data.
|
|
|
|
Repeated calls are equivalent to a single call with the concatenation
|
|
of all the arguments. In other words:
|
|
|
|
>>> m.update(a); m.update(b)
|
|
|
|
is equivalent to:
|
|
|
|
>>> m.update(a+b)
|
|
|
|
:Parameters:
|
|
msg : byte string
|
|
The next chunk of the message being authenticated
|
|
"""
|
|
|
|
self.inner.update(msg)
|
|
|
|
def copy(self):
|
|
"""Return a copy ("clone") of the MAC object.
|
|
|
|
The copy will have the same internal state as the original MAC
|
|
object.
|
|
This can be used to efficiently compute the MAC of strings that
|
|
share a common initial substring.
|
|
|
|
:Returns: An `HMAC` object
|
|
"""
|
|
other = HMAC(b(""))
|
|
other.digestmod = self.digestmod
|
|
other.inner = self.inner.copy()
|
|
other.outer = self.outer.copy()
|
|
return other
|
|
|
|
def digest(self):
|
|
"""Return the **binary** (non-printable) MAC of the message that has
|
|
been authenticated so far.
|
|
|
|
This method does not change the state of the MAC object.
|
|
You can continue updating the object after calling this function.
|
|
|
|
:Return: A byte string of `digest_size` bytes. It may contain non-ASCII
|
|
characters, including null bytes.
|
|
"""
|
|
h = self.outer.copy()
|
|
h.update(self.inner.digest())
|
|
return h.digest()
|
|
|
|
def hexdigest(self):
|
|
"""Return the **printable** MAC of the message that has been
|
|
authenticated so far.
|
|
|
|
This method does not change the state of the MAC object.
|
|
|
|
:Return: A string of 2* `digest_size` bytes. It contains only
|
|
hexadecimal ASCII digits.
|
|
"""
|
|
return "".join(["%02x" % bord(x)
|
|
for x in tuple(self.digest())])
|
|
|
|
def new(key, msg = None, digestmod = None):
|
|
"""Create a new HMAC object.
|
|
|
|
:Parameters:
|
|
key : byte string
|
|
key for the MAC object.
|
|
It must be long enough to match the expected security level of the
|
|
MAC. However, there is no benefit in using keys longer than the
|
|
`digest_size` of the underlying hash algorithm.
|
|
msg : byte string
|
|
The very first chunk of the message to authenticate.
|
|
It is equivalent to an early call to `HMAC.update()`.
|
|
Optional.
|
|
:Parameter digestmod:
|
|
The hash to use to implement the HMAC. Default is `Crypto.Hash.MD5`.
|
|
:Type digestmod:
|
|
A hash module or instantiated object from `Crypto.Hash`
|
|
:Returns: An `HMAC` object
|
|
"""
|
|
return HMAC(key, msg, digestmod)
|
|
|