Mercurial > libervia-backend
view src/memory/crypto.py @ 1196:268278d9aef2
misc: forgotten to change distribute_setup.py to ez_setup.py in MANIFEST.in
author | Goffi <goffi@goffi.org> |
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date | Mon, 15 Sep 2014 13:29:38 +0200 |
parents | 77cd312d32c4 |
children | 069ad98b360d |
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#!/usr/bin/python # -*- coding: utf-8 -*- # SAT: a jabber client # Copyright (C) 2009, 2010, 2011, 2012, 2013, 2014 Jérôme Poisson (goffi@goffi.org) # Copyright (C) 2013, 2014 Adrien Cossa (souliane@mailoo.org) # This program is free software: you can redistribute it and/or modify # it under the terms of the GNU Affero General Public License as published by # the Free Software Foundation, either version 3 of the License, or # (at your option) any later version. # This program is distributed in the hope that it will be useful, # but WITHOUT ANY WARRANTY; without even the implied warranty of # MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the # GNU Affero General Public License for more details. # You should have received a copy of the GNU Affero General Public License # along with this program. If not, see <http://www.gnu.org/licenses/>. try: from Crypto.Cipher import AES from Crypto.Protocol.KDF import PBKDF2 except ImportError: raise Exception("PyCrypto is not installed.") from os import urandom from base64 import b64encode, b64decode from twisted.internet.threads import deferToThread from twisted.internet.defer import succeed class BlockCipher(object): BLOCK_SIZE = AES.block_size # 16 bits MAX_KEY_SIZE = AES.key_size[-1] # 32 bits = AES-256 IV_SIZE = BLOCK_SIZE # initialization vector size, 16 bits @classmethod def encrypt(cls, key, text, leave_empty=True): """Encrypt a message. Based on http://stackoverflow.com/a/12525165 @param key (unicode): the encryption key @param text (unicode): the text to encrypt @param leave_empty (bool): if True, empty text will be returned "as is" @return: Deferred: base-64 encoded str """ if leave_empty and text == '': return succeed(text) iv = BlockCipher.getRandomKey() key = key.encode('utf-8') key = key[:BlockCipher.MAX_KEY_SIZE] if len(key) >= BlockCipher.MAX_KEY_SIZE else BlockCipher.pad(key) cipher = AES.new(key, AES.MODE_CFB, iv) d = deferToThread(cipher.encrypt, BlockCipher.pad(text.encode('utf-8'))) d.addCallback(lambda ciphertext: b64encode(iv + ciphertext)) return d @classmethod def decrypt(cls, key, ciphertext, leave_empty=True): """Decrypt a message. Based on http://stackoverflow.com/a/12525165 @param key (unicode): the decryption key @param ciphertext (base-64 encoded str): the text to decrypt @param leave_empty (bool): if True, empty ciphertext will be returned "as is" @return: Deferred: str or None if the password could not be decrypted """ if leave_empty and ciphertext == '': return succeed('') ciphertext = b64decode(ciphertext) iv, ciphertext = ciphertext[:BlockCipher.IV_SIZE], ciphertext[BlockCipher.IV_SIZE:] key = key.encode('utf-8') key = key[:BlockCipher.MAX_KEY_SIZE] if len(key) >= BlockCipher.MAX_KEY_SIZE else BlockCipher.pad(key) cipher = AES.new(key, AES.MODE_CFB, iv) d = deferToThread(cipher.decrypt, ciphertext) d.addCallback(lambda text: BlockCipher.unpad(text)) # XXX: cipher.decrypt gives no way to make the distinction between # a decrypted empty value and a decryption failure... both return # the empty value. Fortunately, we detect empty passwords beforehand # thanks to the "leave_empty" parameter which is used by default. d.addCallback(lambda text: text.decode('utf-8') if text else None) return d @classmethod def getRandomKey(cls, size=None, base64=False): """Return a random key suitable for block cipher encryption. Note: a good value for the key length is to make it as long as the block size. @param size: key length in bytes, positive or null (default: BlockCipher.IV_SIZE) @param base64: if True, encode the result to base-64 @return: str (eventually base-64 encoded) """ if size is None or size < 0: size = BlockCipher.IV_SIZE key = urandom(size) return b64encode(key) if base64 else key @classmethod def pad(self, s): """Method from http://stackoverflow.com/a/12525165""" bs = BlockCipher.BLOCK_SIZE return s + (bs - len(s) % bs) * chr(bs - len(s) % bs) @classmethod def unpad(self, s): """Method from http://stackoverflow.com/a/12525165""" return s[0:-ord(s[-1])] class PasswordHasher(object): SALT_LEN = 16 # 128 bits @classmethod def hash(cls, password, salt=None, leave_empty=True): """Hash a password. @param password (str): the password to hash @param salt (base-64 encoded str): if not None, use the given salt instead of a random value @param leave_empty (bool): if True, empty password will be returned "as is" @return: Deferred: base-64 encoded str """ if leave_empty and password == '': return succeed(password) salt = b64decode(salt)[:PasswordHasher.SALT_LEN] if salt else urandom(PasswordHasher.SALT_LEN) d = deferToThread(PBKDF2, password, salt) d.addCallback(lambda hashed: b64encode(salt + hashed)) return d @classmethod def verify(cls, attempt, hashed): """Verify a password attempt. @param attempt (str): the attempt to check @param hashed (str): the hash of the password @return: Deferred: boolean """ leave_empty = hashed == '' d = PasswordHasher.hash(attempt, hashed, leave_empty) d.addCallback(lambda hashed_attempt: hashed_attempt == hashed) return d