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# Copyright 2011 OpenStack Foundation
# All Rights Reserved.
#
# 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.
"""
Routines for URL-safe encrypting/decrypting
"""
import base64
from Crypto.Cipher import AES
from Crypto import Random
from Crypto.Random import random
# NOTE(jokke): simplified transition to py3, behaves like py2 xrange
from six.moves import range
def urlsafe_encrypt(key, plaintext, blocksize=16):
"""
Encrypts plaintext. Resulting ciphertext will contain URL-safe characters
:param key: AES secret key
:param plaintext: Input text to be encrypted
:param blocksize: Non-zero integer multiple of AES blocksize in bytes (16)
:returns : Resulting ciphertext
"""
def pad(text):
"""
Pads text to be encrypted
"""
pad_length = (blocksize - len(text) % blocksize)
sr = random.StrongRandom()
pad = ''.join(chr(sr.randint(1, 0xFF)) for i in range(pad_length - 1))
# We use chr(0) as a delimiter between text and padding
return text + chr(0) + pad
# random initial 16 bytes for CBC
init_vector = Random.get_random_bytes(16)
cypher = AES.new(key, AES.MODE_CBC, init_vector)
padded = cypher.encrypt(pad(str(plaintext)))
return base64.urlsafe_b64encode(init_vector + padded)
def urlsafe_decrypt(key, ciphertext):
"""
Decrypts URL-safe base64 encoded ciphertext
:param key: AES secret key
:param ciphertext: The encrypted text to decrypt
:returns : Resulting plaintext
"""
# Cast from unicode
ciphertext = base64.urlsafe_b64decode(str(ciphertext))
cypher = AES.new(key, AES.MODE_CBC, ciphertext[:16])
padded = cypher.decrypt(ciphertext[16:])
return padded[:padded.rfind(chr(0))]
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