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# mac.py - module for checking value signatures
# coding: utf-8
#
# Copyright (C) 2014 Arthur de Jong
#
# This library is free software; you can redistribute it and/or
# modify it under the terms of the GNU Lesser General Public
# License as published by the Free Software Foundation; either
# version 2.1 of the License, or (at your option) any later version.
#
# This library is distributed in the hope that it will be useful,
# but WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
# Lesser General Public License for more details.
#
# You should have received a copy of the GNU Lesser General Public
# License along with this library; if not, write to the Free Software
# Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
# 02110-1301 USA
import base64
import hashlib
import hmac
HMAC_SHA1 = 'http://www.w3.org/2000/09/xmldsig#hmac-sha1'
class ValueMAC(object):
def __init__(self, mac, value_mac=None):
self.mac = mac
self.value_mac = None
self.parse(value_mac)
def parse(self, value_mac):
from pskc.parse import g_e_v
if value_mac is None:
return
value = g_e_v(value_mac, '.')
if value is not None:
self.value_mac = base64.b64decode(value)
def check(self, value):
if value is None or self.value_mac is None:
return
algorithm = self.mac.algorithm
key = self.mac.key
if algorithm == HMAC_SHA1 and key is not None:
h = hmac.new(key, value, hashlib.sha1).digest()
return h == self.value_mac
class MAC(object):
def __init__(self, pskc, mac_method=None):
from pskc.encryption import EncryptedValue
self.algorithm = None
self.mac_key = EncryptedValue(pskc.encryption)
self.parse(mac_method)
def parse(self, mac_method):
"""Read encryption information from the EncryptionKey XML tree."""
from pskc.parse import g_e_v, namespaces
if mac_method is None:
return
self.algorithm = mac_method.attrib.get('Algorithm')
self.mac_key.parse(mac_method.find(
'pskc:MACKey', namespaces=namespaces))
mac_key_reference = g_e_v(mac_method, 'pskc:MACKeyReference')
@property
def key(self):
return self.mac_key.decrypt()
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