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
|
# 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.
import six
from cryptography.hazmat.primitives import hmac
def hkdf_extract(algorithm, ikm, salt, backend):
h = hmac.HMAC(salt, algorithm, backend=backend)
h.update(ikm)
return h.finalize()
def hkdf_expand(algorithm, prk, info, length, backend):
output = [b'']
counter = 1
while (algorithm.digest_size // 8) * len(output) < length:
h = hmac.HMAC(prk, algorithm, backend=backend)
h.update(output[-1])
h.update(info)
h.update(six.int2byte(counter))
output.append(h.finalize())
counter += 1
return b"".join(output)[:length]
def hkdf_derive(key, length, salt, info, algorithm, backend):
if info is None:
info = b""
if salt is None:
salt = b"\x00" * (algorithm.digest_size // 8)
return hkdf_expand(
algorithm,
hkdf_extract(algorithm, key, salt, backend=backend),
info,
length,
backend=backend
)
|
