CocoMUD client

# Copyright (c) 2016, LE GOFF Vincent

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"""This file contains the 'safe' system of CocoMUD, ways to crypt/encrypt.

This feature requires:

    pbkdf2

    pyaes

The module contains a class named 'Safe', that should be insantiated

in order to manipulate the encrypting

/decrypting mechanism.  This class requires a passphrase in

argument.  You can insantiate it as follows:

>>> from safe import Safe

>>> safe = Safe(file=".passphrase")

>>> # (If the file doesn't exist, it will be created with an auto-generated

>>> # passphrase.)

>>> # Alternatively you can specify the passphrase directly

>>> safe = Safe(passphrase="Dsm18fvdjP9sz801,9DJA.1356gndYJz987v")

>>> # Store encrypted data

>>> safe.store("login", "kredh")

>>> safe.store("password", "YoudWishIToldYou")

>>> # Retrieve the data (can be later)

>>> login = safe.retrieve("login")

>>> password = safe.retrieve("password")

Note that datas that is not a string (like a bool or float) will be

saved as unprotected data.  If you want to save it encrypted, you can

convert it to string.

"""

import base64

import os

import pickle

import pyaes

from pbkdf2 import PBKDF2

class Safe:

    """A safe object, to encrypt/decrypt information.

    The Safe class requires a passphrase to be created.  This is a

    string of characters that adds to the security of encryption.

    Obviously, it needs to remain similar to decrypt information that

    has been encrypted.  Other optional parameters are also possible:

        secret: the path of the file in which to store crypted data.

    """

    def __init__(self, passphrase=None, file=None, secret="data.crypt",

            load=True):

        self.salt_seed = 'mkhgts465wef4fwtdd'

        self.passphrase = passphrase

        self.secret = secret

        self.passphrase_size = 64

        self.key_size = 32

        self.block_size = 16

        self.iv_size = 16

        self.salt_size = 8

        self.data = {}

        if file and os.path.exists(file):

            with open(file, "r") as pass_file:

                self.passphrase = pass_file.read()

        if not self.passphrase:

            self.passphrase = base64.b64encode(os.urandom(

                    self.passphrase_size))

            if file:

                with open(file, "wb") as pass_file:

                    pass_file.write(self.passphrase)

        # Load the secret file

        if load:

            self.load()

    def get_salt_from_key(self, key):

        return PBKDF2(key, self.salt_seed).read(self.salt_size)

    def encrypt(self, plaintext, salt):

        """Pad plaintext, then encrypt it.

        The encryption occurs with a new, randomly initialised cipher.

        This method will not preserve trailing whitespace in plaintext!.

        """

        # Initialise Cipher Randomly

        init_vector = os.urandom(self.iv_size)

        # Prepare cipher key

        key = PBKDF2(self.passphrase, salt).read(self.key_size)

        cipher = pyaes.AESModeOfOperationCBC(key, iv=init_vector)

        bs = self.block_size

        if isinstance(plaintext, str):

            plaintext = plaintext.encode("utf-8")

        return init_vector + cipher.encrypt(plaintext + \

                b" " * (bs - (len(plaintext) % bs)))

    def decrypt(self, ciphertext, salt):

        """Reconstruct the cipher object and decrypt.

        This method will not preserve trailing whitespace in the

        retrieved value.

        """

        # Prepare cipher key

        key = PBKDF2(self.passphrase, salt).read(self.key_size)

        # Extract IV

        init_vector = ciphertext[:self.iv_size]

        ciphertext = ciphertext[self.iv_size:]

        cipher = pyaes.AESModeOfOperationCBC(key, iv=init_vector)

        decrypted = cipher.decrypt(ciphertext).rstrip(b" ")

        return decrypted.decode("utf-8")

    def load(self):

        """Load the data from the 'secret' file if exists."""

        if os.path.exists(self.secret):

            with open(self.secret, "rb") as file:

                upic = pickle.Unpickler(file, encoding="utf-8")

                self.data = upic.load()

            if not isinstance(self.data, dict):

                raise ValueError("the data contained in the file " \

                            "'{}' is not a dictionary".format(self.secret))

    def retrieve(self, key, *default):

        """Retrieve and decrypt the specified key.

        If the key isn't present in the dictionary, either

        return default if specified, or raise a KeyError.

        If the value at this location isn't a string, return it as is.

        """

        if key not in self.data:

            if default:

                return default[0]

            raise KeyError(key)

        value = self.data[key]

        if isinstance(value, (bytes, str)):

            salt = self.get_salt_from_key(key)

            return self.decrypt(value, salt)

        return value

    def store(self, key, value):

        """Store the key in the file.

        If the key already exists, replaces it.

        If the value is not a string, it will be stored

        WITHOUT encryption.

        """

        if isinstance(value, str):

            salt = self.get_salt_from_key(key)

            crypted = self.encrypt(value, salt)

            self.data[key] = crypted

        else:

            self.data[key] = value

        # Write the new data in the file

        self.save()

    def save(self):

        """Save the data in the secret file."""

        with open(self.secret, "wb") as file:

            pic = pickle.Pickler(file)

            pic.dump(self.data)