view sat/memory/crypto.py @ 3942:a92eef737703

plugin XEP-0373: download public keys if they are not found in local storage: public keys were only obtained from PEP notifications, however this wasn't working if the entity was not in our roster. Now if no public key is retrieved from local storage, the public key node is requested, and an error is raised if nothing is found. This allows the use of OX with entities which are not in roster. rel 380
author Goffi <goffi@goffi.org>
date Sat, 15 Oct 2022 20:38:33 +0200
parents be6d91572633
children 524856bd7b19
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#!/usr/bin/env python3

# SAT: a jabber client
# Copyright (C) 2009-2021 Jérôme Poisson (goffi@goffi.org)
# Copyright (C) 2013-2016 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/>.

from os import urandom
from base64 import b64encode, b64decode
from cryptography.hazmat.primitives import hashes
from cryptography.hazmat.primitives.kdf.pbkdf2 import PBKDF2HMAC
from cryptography.hazmat.primitives.ciphers import Cipher, algorithms, modes
from cryptography.hazmat.backends import default_backend


crypto_backend = default_backend()


class BlockCipher:

    BLOCK_SIZE = 16
    MAX_KEY_SIZE = 32
    IV_SIZE = BLOCK_SIZE  # initialization vector size, 16 bits

    @staticmethod
    def encrypt(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 (D(str)): base-64 encoded encrypted message
        """
        if leave_empty and text == "":
            return ""
        iv = BlockCipher.getRandomKey()
        key = key.encode()
        key = (
            key[: BlockCipher.MAX_KEY_SIZE]
            if len(key) >= BlockCipher.MAX_KEY_SIZE
            else BlockCipher.pad(key)
        )

        cipher = Cipher(algorithms.AES(key), modes.CFB8(iv), backend=crypto_backend)
        encryptor = cipher.encryptor()
        encrypted = encryptor.update(BlockCipher.pad(text.encode())) + encryptor.finalize()
        return b64encode(iv + encrypted).decode()

    @staticmethod
    def decrypt(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 ""
        ciphertext = b64decode(ciphertext)
        iv, ciphertext = (
            ciphertext[: BlockCipher.IV_SIZE],
            ciphertext[BlockCipher.IV_SIZE :],
        )
        key = key.encode()
        key = (
            key[: BlockCipher.MAX_KEY_SIZE]
            if len(key) >= BlockCipher.MAX_KEY_SIZE
            else BlockCipher.pad(key)
        )

        cipher = Cipher(algorithms.AES(key), modes.CFB8(iv), backend=crypto_backend)
        decryptor = cipher.decryptor()
        decrypted = decryptor.update(ciphertext) + decryptor.finalize()
        return BlockCipher.unpad(decrypted)

    @staticmethod
    def getRandomKey(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

    @staticmethod
    def pad(s):
        """Method from http://stackoverflow.com/a/12525165"""
        bs = BlockCipher.BLOCK_SIZE
        return s + (bs - len(s) % bs) * (chr(bs - len(s) % bs)).encode()

    @staticmethod
    def unpad(s):
        """Method from http://stackoverflow.com/a/12525165"""
        s = s.decode()
        return s[0 : -ord(s[-1])]


class PasswordHasher:

    SALT_LEN = 16  # 128 bits

    @staticmethod
    def hash(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 ""
        salt = (
            b64decode(salt)[: PasswordHasher.SALT_LEN]
            if salt
            else urandom(PasswordHasher.SALT_LEN)
        )

        # we use PyCrypto's PBKDF2 arguments while porting to crytography, to stay
        # compatible with existing installations. But this is temporary and we need
        # to update them to more secure values.
        kdf = PBKDF2HMAC(
            # FIXME: SHA1() is not secure, it is used here for historical reasons
            #   and must be changed as soon as possible
            algorithm=hashes.SHA1(),
            length=16,
            salt=salt,
            iterations=1000,
            backend=crypto_backend
        )
        key = kdf.derive(password.encode())
        return b64encode(salt + key).decode()

    @staticmethod
    def verify(attempt, pwd_hash):
        """Verify a password attempt.

        @param attempt (str): the attempt to check
        @param pwd_hash (str): the hash of the password
        @return: Deferred: boolean
        """
        assert isinstance(attempt, str)
        assert isinstance(pwd_hash, str)
        leave_empty = pwd_hash == ""
        attempt_hash = PasswordHasher.hash(attempt, pwd_hash, leave_empty)
        assert isinstance(attempt_hash, str)
        return attempt_hash == pwd_hash