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# serialiser.py - PSKC file parsing functions
# coding: utf-8
#
# Copyright (C) 2016-2017 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
"""Module for serialising PSKC files to XML."""
import base64
from pskc.key import EncryptedIntegerValue, EncryptedValue
from pskc.xml import find, mk_elem, move_namespaces, reformat, tostring
def my_b64encode(value):
"""Wrap around b64encode to handle types correctly."""
if not isinstance(value, type(b'')):
value = value.encode() # pragma: no cover (Python 3 specific)
return base64.b64encode(value).decode()
class PSKCSerialiser(object):
@classmethod
def serialise_file(cls, pskc, output):
xml = tostring(cls.serialise_document(pskc))
try:
output.write(xml)
except TypeError: # pragma: no cover (Python 3 specific)
# fall back to writing as string for Python 3
output.write(xml.decode('utf-8'))
@classmethod
def serialise_document(cls, pskc):
container = mk_elem('pskc:KeyContainer', Version=pskc.version,
Id=pskc.id)
cls.serialise_encryption(pskc.encryption, container)
cls.serialise_mac(pskc.mac, container)
for device in pskc.devices:
cls.serialise_key_package(device, container)
return cls.serialise_signature(pskc.signature, container)
@classmethod
def serialise_encryption(cls, encryption, container):
if all(x is None
for x in (encryption.id, encryption.key_name, encryption.key,
encryption.derivation.algorithm)):
return
encryption_key = mk_elem(container, 'pskc:EncryptionKey',
Id=encryption.id, empty=True)
if encryption.derivation.algorithm:
cls.serialise_key_derivation(
encryption.derivation, encryption_key, encryption.key_names)
else:
for name in encryption.key_names:
mk_elem(encryption_key, 'ds:KeyName', name)
@classmethod
def serialise_key_derivation(cls, derivation, encryption_key, key_names):
derived_key = mk_elem(encryption_key, 'xenc11:DerivedKey', empty=True)
key_derivation = mk_elem(derived_key, 'xenc11:KeyDerivationMethod',
Algorithm=derivation.algorithm)
if derivation.algorithm.endswith('#pbkdf2'):
pbkdf2 = mk_elem(key_derivation, 'xenc11:PBKDF2-params',
empty=True)
if derivation.pbkdf2_salt:
salt = mk_elem(pbkdf2, 'Salt', empty=True)
mk_elem(salt, 'Specified',
base64.b64encode(derivation.pbkdf2_salt).decode())
mk_elem(pbkdf2, 'IterationCount', derivation.pbkdf2_iterations)
mk_elem(pbkdf2, 'KeyLength', derivation.pbkdf2_key_length)
mk_elem(pbkdf2, 'PRF', derivation.pbkdf2_prf)
# TODO: serialise ReferenceList/DataReference
for name in key_names:
mk_elem(derived_key, 'xenc11:MasterKeyName', name)
@classmethod
def serialise_mac(cls, mac, container):
if not mac.algorithm and not mac.key:
return
mac_method = mk_elem(
container, 'pskc:MACMethod', Algorithm=mac.algorithm, empty=True)
mac_key = mk_elem(mac_method, 'pskc:MACKey', empty=True)
mk_elem(
mac_key, 'xenc:EncryptionMethod',
Algorithm=mac.pskc.encryption.algorithm)
cipher_data = mk_elem(mac_key, 'xenc:CipherData', empty=True)
if mac.key_cipher_value:
mk_elem(cipher_data, 'xenc:CipherValue',
base64.b64encode(mac.key_cipher_value).decode())
elif mac.key_plain_value:
mk_elem(cipher_data, 'xenc:CipherValue',
base64.b64encode(mac.pskc.encryption.encrypt_value(
mac.key_plain_value)).decode())
@classmethod
def serialise_key_package(cls, device, container):
key_package = mk_elem(container, 'pskc:KeyPackage', empty=True)
if any(x is not None
for x in (device.manufacturer, device.serial, device.model,
device.issue_no, device.device_binding,
device.start_date, device.expiry_date,
device.device_userid)):
device_info = mk_elem(key_package, 'pskc:DeviceInfo', empty=True)
mk_elem(device_info, 'pskc:Manufacturer', device.manufacturer)
mk_elem(device_info, 'pskc:SerialNo', device.serial)
mk_elem(device_info, 'pskc:Model', device.model)
mk_elem(device_info, 'pskc:IssueNo', device.issue_no)
mk_elem(device_info, 'pskc:DeviceBinding', device.device_binding)
mk_elem(device_info, 'pskc:StartDate', device.start_date)
mk_elem(device_info, 'pskc:ExpiryDate', device.expiry_date)
mk_elem(device_info, 'pskc:UserId', device.device_userid)
if device.crypto_module is not None:
crypto_module = mk_elem(key_package, 'pskc:CryptoModuleInfo',
empty=True)
mk_elem(crypto_module, 'pskc:Id', device.crypto_module)
for key in device.keys:
cls.serialise_key(key, key_package)
@classmethod
def serialise_key(cls, key, key_package):
key_elm = mk_elem(key_package, 'pskc:Key', empty=True, Id=key.id,
Algorithm=key.algorithm, )
mk_elem(key_elm, 'pskc:Issuer', key.issuer)
if any((key.algorithm_suite, key.challenge_encoding,
key.response_encoding, key.response_length)):
parameters = mk_elem(key_elm, 'pskc:AlgorithmParameters',
empty=True)
mk_elem(parameters, 'pskc:Suite', key.algorithm_suite)
mk_elem(parameters, 'pskc:ChallengeFormat',
Encoding=key.challenge_encoding,
Min=key.challenge_min_length,
Max=key.challenge_max_length,
CheckDigits=key.challenge_check)
mk_elem(parameters, 'pskc:ResponseFormat',
Encoding=key.response_encoding,
Length=key.response_length,
CheckDigits=key.response_check)
mk_elem(key_elm, 'pskc:KeyProfileId', key.key_profile)
mk_elem(key_elm, 'pskc:KeyReference', key.key_reference)
mk_elem(key_elm, 'pskc:FriendlyName', key.friendly_name)
cls.serialise_data(
key, 'secret', key_elm, 'pskc:Secret')
cls.serialise_data(
key, 'counter', key_elm, 'pskc:Counter')
cls.serialise_data(
key, 'time_offset', key_elm, 'pskc:Time')
cls.serialise_data(
key, 'time_interval', key_elm, 'pskc:TimeInterval')
cls.serialise_data(
key, 'time_drift', key_elm, 'pskc:TimeDrift')
mk_elem(key_elm, 'pskc:UserId', key.key_userid)
cls.serialise_policy(key.policy, key_elm)
@classmethod
def serialise_data(cls, key, field, key_elm, tag):
value = getattr(key, '_%s' % field, None)
pskc = key.device.pskc
# skip empty values
if value in (None, ''):
return
# get the value2text and encryption storage
if field == 'secret':
value2text = my_b64encode
encrypted_value_cls = EncryptedValue
else:
value2text = str
encrypted_value_cls = EncryptedIntegerValue
# find the data tag and create our tag under it
data = find(key_elm, 'pskc:Data')
if data is None:
data = mk_elem(key_elm, 'pskc:Data', empty=True)
element = mk_elem(data, tag, empty=True)
# see if we should encrypt the value
if field in pskc.encryption.fields and not hasattr(
value, 'get_value'):
value = encrypted_value_cls.create(pskc, value)
# write out value
if not hasattr(value, 'get_value'):
# unencrypted value
mk_elem(element, 'pskc:PlainValue', value2text(value))
else:
# encrypted value
encrypted_value = mk_elem(
element, 'pskc:EncryptedValue', empty=True)
mk_elem(encrypted_value, 'xenc:EncryptionMethod',
Algorithm=value.algorithm)
cipher_data = mk_elem(
encrypted_value, 'xenc:CipherData', empty=True)
mk_elem(cipher_data, 'xenc:CipherValue',
base64.b64encode(value.cipher_value).decode())
if value.mac_value:
mk_elem(element, 'pskc:ValueMAC',
base64.b64encode(value.mac_value).decode())
@classmethod
def serialise_policy(cls, policy, key_elm):
# check if any policy attribute is set
if not policy.key_usage and all(x is None for x in (
policy.start_date, policy.expiry_date,
policy.number_of_transactions, policy.pin_key_id,
policy.pin_usage, policy.pin_max_failed_attempts,
policy.pin_min_length, policy.pin_max_length,
policy.pin_encoding)):
return
policy_elm = mk_elem(key_elm, 'pskc:Policy', empty=True)
mk_elem(policy_elm, 'pskc:StartDate', policy.start_date)
mk_elem(policy_elm, 'pskc:ExpiryDate', policy.expiry_date)
mk_elem(policy_elm, 'pskc:PINPolicy',
PINKeyId=policy.pin_key_id,
PINUsageMode=policy.pin_usage,
MaxFailedAttempts=policy.pin_max_failed_attempts,
MinLength=policy.pin_min_length,
MaxLength=policy.pin_max_length,
PINEncoding=policy.pin_encoding)
for usage in policy.key_usage:
mk_elem(policy_elm, 'pskc:KeyUsage', usage)
mk_elem(policy_elm, 'pskc:NumberOfTransactions',
policy.number_of_transactions)
@classmethod
def serialise_signature(cls, signature, container):
if not signature.key:
return container
# move the namespace to the root element and reformat before signing
mk_elem(container, 'ds:Signature', Id='placeholder')
container = move_namespaces(container)
reformat(container)
# sign the document
return signature.sign_xml(container)
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