modoboa/modoboa/core/password_hashers/base.py

"""
Base password hashers.

Contains weak hashers (the original ones) available with Modoboa.
"""
import crypt
import hashlib
import base64
import string
from random import Random
from django.utils.crypto import constant_time_compare


class PasswordHasher(object):
    """
    Base class of all hashers.
    """
    def encrypt(self, clearvalue):
        """Encrypt a password.

        The format used to store passwords is the same than dovecot's one::

          {SCHEME}<hash>

        <hash> may differ according to the used scheme.

        :param str clearvalue: clear password
        :rtype: str
        :return: encrypted password
        """
        return '%s%s' % (self.scheme, self._encrypt(clearvalue))

    def verify(self, clearvalue, hashed_value):
        """Verify a password against a hashed value.

        :param str clearvalue: clear password
        :param str hashed_value: password previously hashed
        :return: True if passwords match, False otherwise
        """
        return constant_time_compare(
            self._encrypt(clearvalue, hashed_value),
            hashed_value
        )


class PLAINHasher(PasswordHasher):
    """
    Plain (ie. clear) password hasher.
    """
    @property
    def scheme(self):
        return '{PLAIN}'

    def _encrypt(self, clearvalue, salt=None):
        return clearvalue


class CRYPTHasher(PasswordHasher):
    """
    crypt password hasher.

    Uses python `crypt` standard module.
    """
    @property
    def scheme(self):
        return '{CRYPT}'

    def _encrypt(self, clearvalue, salt=None):
        if salt is None:
            salt = "".join(Random().sample(string.letters + string.digits, 2))
        return crypt.crypt(clearvalue, salt)


class MD5Hasher(PasswordHasher):
    """
    MD5 password hasher.

    Uses python `hashlib` standard module.
    """
    @property
    def scheme(self):
        return '{MD5}'

    def _encrypt(self, clearvalue, salt=None):
        obj = hashlib.md5(clearvalue)
        return obj.hexdigest()


class SHA256Hasher(PasswordHasher):
    """
    SHA256 password hasher.

    Uses python `hashlib` and `base64` standard modules.
    """
    @property
    def scheme(self):
        return '{SHA256}'

    def _encrypt(self, clearvalue, salt=None):
        return base64.b64encode(hashlib.sha256(clearvalue).digest())