/usr/lib/python3/dist-packages/cryptography/fernet.py is in python3-cryptography 1.2.3-1.
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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 | # This file is dual licensed under the terms of the Apache License, Version
# 2.0, and the BSD License. See the LICENSE file in the root of this repository
# for complete details.
from __future__ import absolute_import, division, print_function
import base64
import binascii
import os
import struct
import time
import six
from cryptography.exceptions import InvalidSignature
from cryptography.hazmat.backends import default_backend
from cryptography.hazmat.primitives import hashes, padding
from cryptography.hazmat.primitives.ciphers import Cipher, algorithms, modes
from cryptography.hazmat.primitives.hmac import HMAC
class InvalidToken(Exception):
pass
_MAX_CLOCK_SKEW = 60
class Fernet(object):
def __init__(self, key, backend=None):
if backend is None:
backend = default_backend()
key = base64.urlsafe_b64decode(key)
if len(key) != 32:
raise ValueError(
"Fernet key must be 32 url-safe base64-encoded bytes."
)
self._signing_key = key[:16]
self._encryption_key = key[16:]
self._backend = backend
@classmethod
def generate_key(cls):
return base64.urlsafe_b64encode(os.urandom(32))
def encrypt(self, data):
current_time = int(time.time())
iv = os.urandom(16)
return self._encrypt_from_parts(data, current_time, iv)
def _encrypt_from_parts(self, data, current_time, iv):
if not isinstance(data, bytes):
raise TypeError("data must be bytes.")
padder = padding.PKCS7(algorithms.AES.block_size).padder()
padded_data = padder.update(data) + padder.finalize()
encryptor = Cipher(
algorithms.AES(self._encryption_key), modes.CBC(iv), self._backend
).encryptor()
ciphertext = encryptor.update(padded_data) + encryptor.finalize()
basic_parts = (
b"\x80" + struct.pack(">Q", current_time) + iv + ciphertext
)
h = HMAC(self._signing_key, hashes.SHA256(), backend=self._backend)
h.update(basic_parts)
hmac = h.finalize()
return base64.urlsafe_b64encode(basic_parts + hmac)
def decrypt(self, token, ttl=None):
if not isinstance(token, bytes):
raise TypeError("token must be bytes.")
current_time = int(time.time())
try:
data = base64.urlsafe_b64decode(token)
except (TypeError, binascii.Error):
raise InvalidToken
if not data or six.indexbytes(data, 0) != 0x80:
raise InvalidToken
try:
timestamp, = struct.unpack(">Q", data[1:9])
except struct.error:
raise InvalidToken
if ttl is not None:
if timestamp + ttl < current_time:
raise InvalidToken
if current_time + _MAX_CLOCK_SKEW < timestamp:
raise InvalidToken
h = HMAC(self._signing_key, hashes.SHA256(), backend=self._backend)
h.update(data[:-32])
try:
h.verify(data[-32:])
except InvalidSignature:
raise InvalidToken
iv = data[9:25]
ciphertext = data[25:-32]
decryptor = Cipher(
algorithms.AES(self._encryption_key), modes.CBC(iv), self._backend
).decryptor()
plaintext_padded = decryptor.update(ciphertext)
try:
plaintext_padded += decryptor.finalize()
except ValueError:
raise InvalidToken
unpadder = padding.PKCS7(algorithms.AES.block_size).unpadder()
unpadded = unpadder.update(plaintext_padded)
try:
unpadded += unpadder.finalize()
except ValueError:
raise InvalidToken
return unpadded
class MultiFernet(object):
def __init__(self, fernets):
fernets = list(fernets)
if not fernets:
raise ValueError(
"MultiFernet requires at least one Fernet instance"
)
self._fernets = fernets
def encrypt(self, msg):
return self._fernets[0].encrypt(msg)
def decrypt(self, msg, ttl=None):
for f in self._fernets:
try:
return f.decrypt(msg, ttl)
except InvalidToken:
pass
raise InvalidToken
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