1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
|
# key.py - module for handling keys from pskc files
# coding: utf-8
#
# Copyright (C) 2014-2022 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 that handles keys stored in PSKC files."""
import array
import binascii
from pskc.policy import Policy
class EncryptedValue(object):
"""A container for an encrypted value."""
def __init__(self, cipher_value, mac_value, algorithm):
self.cipher_value = cipher_value
self.mac_value = mac_value
self.algorithm = algorithm
@classmethod
def create(cls, pskc, value):
"""Construct an encrypted value from a plaintext value."""
# force conversion to bytestring on Python 3
if not isinstance(value, (type(b''), bytearray)):
value = value.encode() # pragma: no cover (Python 3 specific)
cipher_value = pskc.encryption.encrypt_value(value)
mac_value = None
if pskc.mac.algorithm:
mac_value = pskc.mac.generate_mac(cipher_value)
return cls(cipher_value, mac_value, pskc.encryption.algorithm)
def get_value(self, pskc):
"""Provide the decrypted value."""
from pskc.exceptions import DecryptionError
plaintext = pskc.encryption.decrypt_value(
self.cipher_value, self.algorithm)
# allow MAC over plaintext or ciphertext
# (RFC 6030 implies MAC over ciphertext but older draft used
# MAC over plaintext)
if self.mac_value and self.mac_value not in (
pskc.mac.generate_mac(self.cipher_value),
pskc.mac.generate_mac(plaintext)):
raise DecryptionError('MAC value does not match')
return plaintext
class EncryptedIntegerValue(EncryptedValue):
"""Class representing an encrypted integer value."""
@classmethod
def create(cls, pskc, value):
"""Construct an encrypted value from a plaintext value."""
value = '%x' % value
n = len(value)
value = binascii.unhexlify(value.zfill(n + (n & 1)))
return super(EncryptedIntegerValue, cls).create(pskc, value)
def get_value(self, pskc):
"""Provide the decrypted integer value."""
value = super(EncryptedIntegerValue, self).get_value(pskc)
# try to handle value as ASCII representation
if value.isdigit():
return int(value)
# fall back to do big-endian decoding
result = 0
for x in array.array('B', value):
result = (result << 8) + x
return result
class DataTypeProperty(object):
"""A data descriptor that delegates actions to DataType instances."""
def __init__(self, name, doc):
self.name = name
self.__doc__ = doc
def __get__(self, obj, objtype):
value = getattr(obj, '_' + self.name, None)
if hasattr(value, 'get_value'):
return value.get_value(obj.device.pskc)
else:
return value
def __set__(self, obj, val):
setattr(obj, '_' + self.name, val)
class DeviceProperty(object):
"""A data descriptor that delegates actions to the Device instance."""
def __init__(self, name):
self.name = name
def __get__(self, obj, objtype):
return getattr(obj.device, self.name)
def __set__(self, obj, val):
setattr(obj.device, self.name, val)
class Key(object):
"""Representation of a single key from a PSKC file.
Instances of this class provide the following properties:
id: unique key identifier (should be constant between interchanges)
algorithm: identifier of the PSKC algorithm profile (URI)
secret: the secret key itself (binary form, automatically decrypted)
counter: event counter for event-based OTP
time_offset: time offset for time-based OTP algorithms (in intervals)
time_interval: time interval for time-based OTP in seconds
time_drift: device clock drift (negative means device is slow)
issuer: party that issued the key
key_profile: reference to pre-shared key profile information
key_reference: reference to an external key
friendly_name: human-readable name for the secret key
key_userid: user distinguished name associated with the key
algorithm_suite: additional algorithm characteristics (e.g. used hash)
challenge_encoding: format of the challenge for CR devices
challenge_min_length: minimum accepted challenge length by device
challenge_max_length: maximum size challenge accepted by the device
challenge_check: whether the device will check an embedded check digit
response_encoding: format of the response the device will generate
response_length: the length of the response of the device
response_check: whether the device appends a Luhn check digit
policy: reference to policy information (see Policy class)
This class also provides access to the manufacturer, serial, model,
issue_no, device_binding, start_date, expiry_date, device_userid and
crypto_module properties of the Device class.
"""
def __init__(self, device):
self.device = device
self.id = None
self.algorithm = None
self.issuer = None
self.key_profile = None
self.key_reference = None
self.friendly_name = None
self.key_userid = None
self.algorithm_suite = None
self.challenge_encoding = None
self.challenge_min_length = None
self.challenge_max_length = None
self.challenge_check = None
self.response_encoding = None
self.response_length = None
self.response_check = None
self.policy = Policy(self)
secret = DataTypeProperty(
'secret', 'The secret key itself.')
counter = DataTypeProperty(
'counter', 'An event counter for event-based OTP.')
time_offset = DataTypeProperty(
'time_offset',
'A time offset for time-based OTP (number of intervals).')
time_interval = DataTypeProperty(
'time_interval', 'A time interval in seconds.')
time_drift = DataTypeProperty(
'time_drift', 'Device clock drift value (number of time intervals).')
manufacturer = DeviceProperty('manufacturer')
serial = DeviceProperty('serial')
model = DeviceProperty('model')
issue_no = DeviceProperty('issue_no')
device_binding = DeviceProperty('device_binding')
start_date = DeviceProperty('start_date')
expiry_date = DeviceProperty('expiry_date')
device_userid = DeviceProperty('device_userid')
crypto_module = DeviceProperty('crypto_module')
def check(self):
"""Check if all MACs in the message are valid."""
if all(x is not False for x in (
self.secret, self.counter, self.time_offset,
self.time_interval, self.time_drift)):
return True
@property
def userid(self):
"""User identifier (either the key or device userid)."""
return self.key_userid or self.device_userid
|