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# vim: tabstop=4 shiftwidth=4 softtabstop=4 | ||
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# Copyright 2013 Red Hat, Inc. | ||
# | ||
# 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. | ||
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import base64 | ||
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from Crypto.Hash import HMAC | ||
from Crypto import Random | ||
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from cinder.openstack.common.gettextutils import _ # noqa | ||
from cinder.openstack.common import importutils | ||
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class CryptoutilsException(Exception): | ||
"""Generic Exception for Crypto utilities.""" | ||
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message = _("An unknown error occurred in crypto utils.") | ||
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class CipherBlockLengthTooBig(CryptoutilsException): | ||
"""The block size is too big.""" | ||
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def __init__(self, requested, permitted): | ||
msg = _("Block size of %(given)d is too big, max = %(maximum)d") | ||
message = msg % {'given': requested, 'maximum': permitted} | ||
super(CryptoutilsException, self).__init__(message) | ||
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class HKDFOutputLengthTooLong(CryptoutilsException): | ||
"""The amount of Key Material asked is too much.""" | ||
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def __init__(self, requested, permitted): | ||
msg = _("Length of %(given)d is too long, max = %(maximum)d") | ||
message = msg % {'given': requested, 'maximum': permitted} | ||
super(CryptoutilsException, self).__init__(message) | ||
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class HKDF(object): | ||
"""An HMAC-based Key Derivation Function implementation (RFC5869) | ||
This class creates an object that allows to use HKDF to derive keys. | ||
""" | ||
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def __init__(self, hashtype='SHA256'): | ||
self.hashfn = importutils.import_module('Crypto.Hash.' + hashtype) | ||
self.max_okm_length = 255 * self.hashfn.digest_size | ||
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def extract(self, ikm, salt=None): | ||
"""An extract function that can be used to derive a robust key given | ||
weak Input Key Material (IKM) which could be a password. | ||
Returns a pseudorandom key (of HashLen octets) | ||
:param ikm: input keying material (ex a password) | ||
:param salt: optional salt value (a non-secret random value) | ||
""" | ||
if salt is None: | ||
salt = '\x00' * self.hashfn.digest_size | ||
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return HMAC.new(salt, ikm, self.hashfn).digest() | ||
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def expand(self, prk, info, length): | ||
"""An expand function that will return arbitrary length output that can | ||
be used as keys. | ||
Returns a buffer usable as key material. | ||
:param prk: a pseudorandom key of at least HashLen octets | ||
:param info: optional string (can be a zero-length string) | ||
:param length: length of output keying material (<= 255 * HashLen) | ||
""" | ||
if length > self.max_okm_length: | ||
raise HKDFOutputLengthTooLong(length, self.max_okm_length) | ||
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N = (length + self.hashfn.digest_size - 1) / self.hashfn.digest_size | ||
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okm = "" | ||
tmp = "" | ||
for block in range(1, N + 1): | ||
tmp = HMAC.new(prk, tmp + info + chr(block), self.hashfn).digest() | ||
okm += tmp | ||
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return okm[:length] | ||
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MAX_CB_SIZE = 256 | ||
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class SymmetricCrypto(object): | ||
"""Symmetric Key Crypto object. | ||
This class creates a Symmetric Key Crypto object that can be used | ||
to encrypt, decrypt, or sign arbitrary data. | ||
:param enctype: Encryption Cipher name (default: AES) | ||
:param hashtype: Hash/HMAC type name (default: SHA256) | ||
""" | ||
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def __init__(self, enctype='AES', hashtype='SHA256'): | ||
self.cipher = importutils.import_module('Crypto.Cipher.' + enctype) | ||
self.hashfn = importutils.import_module('Crypto.Hash.' + hashtype) | ||
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def new_key(self, size): | ||
return Random.new().read(size) | ||
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def encrypt(self, key, msg, b64encode=True): | ||
"""Encrypt the provided msg and returns the cyphertext optionally | ||
base64 encoded. | ||
Uses AES-128-CBC with a Random IV by default. | ||
The plaintext is padded to reach blocksize length. | ||
The last byte of the block is the length of the padding. | ||
The length of the padding does not include the length byte itself. | ||
:param key: The Encryption key. | ||
:param msg: the plain text. | ||
:returns encblock: a block of encrypted data. | ||
""" | ||
iv = Random.new().read(self.cipher.block_size) | ||
cipher = self.cipher.new(key, self.cipher.MODE_CBC, iv) | ||
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# CBC mode requires a fixed block size. Append padding and length of | ||
# padding. | ||
if self.cipher.block_size > MAX_CB_SIZE: | ||
raise CipherBlockLengthTooBig(self.cipher.block_size, MAX_CB_SIZE) | ||
r = len(msg) % self.cipher.block_size | ||
padlen = self.cipher.block_size - r - 1 | ||
msg += '\x00' * padlen | ||
msg += chr(padlen) | ||
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enc = iv + cipher.encrypt(msg) | ||
if b64encode: | ||
enc = base64.b64encode(enc) | ||
return enc | ||
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def decrypt(self, key, msg, b64decode=True): | ||
"""Decrypts the provided ciphertext, optionally base 64 encoded, and | ||
returns the plaintext message, after padding is removed. | ||
Uses AES-128-CBC with an IV by default. | ||
:param key: The Encryption key. | ||
:param msg: the ciphetext, the first block is the IV | ||
""" | ||
if b64decode: | ||
msg = base64.b64decode(msg) | ||
iv = msg[:self.cipher.block_size] | ||
cipher = self.cipher.new(key, self.cipher.MODE_CBC, iv) | ||
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padded = cipher.decrypt(msg[self.cipher.block_size:]) | ||
l = ord(padded[-1]) + 1 | ||
plain = padded[:-l] | ||
return plain | ||
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def sign(self, key, msg, b64encode=True): | ||
"""Signs a message string and returns a base64 encoded signature. | ||
Uses HMAC-SHA-256 by default. | ||
:param key: The Signing key. | ||
:param msg: the message to sign. | ||
""" | ||
h = HMAC.new(key, msg, self.hashfn) | ||
out = h.digest() | ||
if b64encode: | ||
out = base64.b64encode(out) | ||
return out |