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
|
# Licensed under the Apache License, Version 2.0 (the "License");
# you may not use this file except in compliance with the License.
# You may obtain a copy of the License at
#
# http://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS,
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or
# implied.
# See the License for the specific language governing permissions and
# limitations under the License.
from __future__ import absolute_import, division, print_function
import six
from cryptography import utils
from cryptography.exceptions import UnsupportedAlgorithm, _Reasons
from cryptography.hazmat.backends.interfaces import DSABackend
from cryptography.hazmat.primitives import interfaces
def _check_dsa_parameters(modulus, subgroup_order, generator):
if (
not isinstance(modulus, six.integer_types) or
not isinstance(subgroup_order, six.integer_types) or
not isinstance(generator, six.integer_types)
):
raise TypeError("DSA parameters must be integers")
if (utils.bit_length(modulus),
utils.bit_length(subgroup_order)) not in (
(1024, 160),
(2048, 256),
(3072, 256)):
raise ValueError("modulus and subgroup_order lengths must be "
"one of these pairs (1024, 160) or (2048, 256) "
"or (3072, 256)")
if generator <= 1 or generator >= modulus:
raise ValueError("generator must be > 1 and < modulus")
@utils.register_interface(interfaces.DSAParameters)
class DSAParameters(object):
def __init__(self, modulus, subgroup_order, generator):
_check_dsa_parameters(modulus, subgroup_order, generator)
self._modulus = modulus
self._subgroup_order = subgroup_order
self._generator = generator
@classmethod
def generate(cls, key_size, backend):
if not isinstance(backend, DSABackend):
raise UnsupportedAlgorithm(
"Backend object does not implement DSABackend",
_Reasons.BACKEND_MISSING_INTERFACE
)
return backend.generate_dsa_parameters(key_size)
@property
def modulus(self):
return self._modulus
@property
def subgroup_order(self):
return self._subgroup_order
@property
def generator(self):
return self._generator
@property
def p(self):
return self.modulus
@property
def q(self):
return self.subgroup_order
@property
def g(self):
return self.generator
@utils.register_interface(interfaces.DSAPrivateKey)
class DSAPrivateKey(object):
def __init__(self, modulus, subgroup_order, generator, x, y):
_check_dsa_parameters(modulus, subgroup_order, generator)
if (
not isinstance(x, six.integer_types) or
not isinstance(y, six.integer_types)
):
raise TypeError("DSAPrivateKey arguments must be integers")
if x <= 0 or x >= subgroup_order:
raise ValueError("x must be > 0 and < subgroup_order")
if y != pow(generator, x, modulus):
raise ValueError("y must be equal to (generator ** x % modulus)")
self._modulus = modulus
self._subgroup_order = subgroup_order
self._generator = generator
self._x = x
self._y = y
@classmethod
def generate(cls, parameters, backend):
if not isinstance(backend, DSABackend):
raise UnsupportedAlgorithm(
"Backend object does not implement DSABackend",
_Reasons.BACKEND_MISSING_INTERFACE
)
return backend.generate_dsa_private_key(parameters)
def signer(self, algorithm, backend):
if not isinstance(backend, DSABackend):
raise UnsupportedAlgorithm(
"Backend object does not implement DSABackend",
_Reasons.BACKEND_MISSING_INTERFACE
)
return backend.create_dsa_signature_ctx(self, algorithm)
@property
def key_size(self):
return utils.bit_length(self._modulus)
def public_key(self):
return DSAPublicKey(self._modulus, self._subgroup_order,
self._generator, self.y)
@property
def x(self):
return self._x
@property
def y(self):
return self._y
def parameters(self):
return DSAParameters(self._modulus, self._subgroup_order,
self._generator)
@utils.register_interface(interfaces.DSAPublicKey)
class DSAPublicKey(object):
def __init__(self, modulus, subgroup_order, generator, y):
_check_dsa_parameters(modulus, subgroup_order, generator)
if not isinstance(y, six.integer_types):
raise TypeError("y must be an integer")
self._modulus = modulus
self._subgroup_order = subgroup_order
self._generator = generator
self._y = y
def verifier(self, signature, algorithm, backend):
if not isinstance(backend, DSABackend):
raise UnsupportedAlgorithm(
"Backend object does not implement DSABackend",
_Reasons.BACKEND_MISSING_INTERFACE
)
return backend.create_dsa_verification_ctx(self, signature,
algorithm)
@property
def key_size(self):
return utils.bit_length(self._modulus)
@property
def y(self):
return self._y
def parameters(self):
return DSAParameters(self._modulus, self._subgroup_order,
self._generator)
|
