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#!/usr/bin/env python
# -*- coding: utf-8 -*-
# The MIT License (MIT)
#
# Copyright (c) 2014 Storj Labs
#
# Permission is hereby granted, free of charge, to any person obtaining a copy
# of this software and associated documentation files (the "Software"), to deal
# in the Software without restriction, including without limitation the rights
# to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
# copies of the Software, and to permit persons to whom the Software is
# furnished to do so, subject to the following conditions:
#
# The above copyright notice and this permission notice shall be included in
# all copies or substantial portions of the Software.
#
# THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
# IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
# FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
# AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
# LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
# OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
# SOFTWARE.
from Cryptodome.Cipher import AES
from Cryptodome.Util import Counter
from file_encryptor.settings import CHUNK_SIZE
from file_encryptor import key_generators
def encrypt_file_inline(filename, passphrase):
"""Encrypt file inline, with an optional passphrase.
If you set the passphrase to None, a default is used.
This will make you vulnerable to confirmation attacks
and learn-partial-information attacks.
:param filename: The name of the file to encrypt.
:type filename: str
:param passphrase: The passphrase used to decrypt the file.
:type passphrase: str or None
:returns: The key required to decrypt the file.
:rtype: str
"""
key = key_generators.key_from_file(filename, passphrase)
inline_transform(filename, key)
return key
def decrypt_file_inline(filename, key):
"""Decrypt file inline with given key.
The given key must be the same that was
returned by encrypt_file_inline.
:param filename: The name of the file to decrypt.
:type filename: str
:param key: The key used to decrypt the file.
:type key: str
"""
inline_transform(filename, key)
def decrypt_generator(filename, key):
"""Stream decrypted file with given key.
The given key must be the same that was
returned by encrypt_file_inline.
:param filename: The name of the file to decrypt.
:type filename: str
:param key: The key used to decrypt the file.
:type key: str
:returns: A generator that streams decrypted file chunks.
:rtype: generator
"""
for chunk, _ in iter_transform(filename, key):
yield chunk
def inline_transform(filename, key):
"""Encrypt file inline.
Encrypts a given file with the given key,
and replaces it directly without any extra
space requirement.
:param filename: The name of the file to encrypt.
:type filename: str
:param key: The key used to encrypt the file.
:type key: str
"""
pos = 0
for chunk, fp in iter_transform(filename, key):
fp.seek(pos)
fp.write(chunk)
fp.flush()
pos = fp.tell()
def iter_transform(filename, key):
"""Generate encrypted file with given key.
This generator function reads the file
in chunks and encrypts them using AES-CTR,
with the specified key.
:param filename: The name of the file to encrypt.
:type filename: str
:param key: The key used to encrypt the file.
:type key: str
:returns: A generator that produces encrypted file chunks.
:rtype: generator
"""
# We are not specifying the IV here.
aes = AES.new(key, AES.MODE_CTR, counter=Counter.new(128))
with open(filename, 'rb+') as f:
for chunk in iter(lambda: f.read(CHUNK_SIZE), b''):
yield aes.encrypt(chunk), f
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