from __future__ import absolute_import import os import abc try: from keyczar import keyczar except ImportError: pass from keyring.backend import Crypter from keyring import errors def has_keyczar(): with errors.ExceptionRaisedContext() as exc: keyczar.__name__ return not bool(exc) class BaseCrypter(Crypter): """Base Keyczar keyset encryption and decryption. The keyset initialisation is deferred until required. """ @abc.abstractproperty def keyset_location(self): """Location for the main keyset that may be encrypted or not""" pass @abc.abstractproperty def encrypting_keyset_location(self): """Location for the encrypting keyset. Use None to indicate that the main keyset is not encrypted """ pass @property def crypter(self): """The actual keyczar crypter""" if not hasattr(self, '_crypter'): # initialise the Keyczar keysets if not self.keyset_location: raise ValueError('No encrypted keyset location!') reader = keyczar.readers.CreateReader(self.keyset_location) if self.encrypting_keyset_location: encrypting_keyczar = keyczar.Crypter.Read( self.encrypting_keyset_location) reader = keyczar.readers.EncryptedReader(reader, encrypting_keyczar) self._crypter = keyczar.Crypter(reader) return self._crypter def encrypt(self, value): """Encrypt the value. """ if not value: return '' return self.crypter.Encrypt(value) def decrypt(self, value): """Decrypt the value. """ if not value: return '' return self.crypter.Decrypt(value) class Crypter(BaseCrypter): """A Keyczar crypter using locations specified in the constructor """ def __init__(self, keyset_location, encrypting_keyset_location=None): self._keyset_location = keyset_location self._encrypting_keyset_location = encrypting_keyset_location @property def keyset_location(self): return self._keyset_location @property def encrypting_keyset_location(self): return self._encrypting_keyset_location class EnvironCrypter(BaseCrypter): """A Keyczar crypter using locations specified by environment vars """ KEYSET_ENV_VAR = 'KEYRING_KEYCZAR_ENCRYPTED_LOCATION' ENC_KEYSET_ENV_VAR = 'KEYRING_KEYCZAR_ENCRYPTING_LOCATION' @property def keyset_location(self): val = os.environ.get(self.KEYSET_ENV_VAR) if not val: raise ValueError('%s environment value not set' % self.KEYSET_ENV_VAR) return val @property def encrypting_keyset_location(self): return os.environ.get(self.ENC_KEYSET_ENV_VAR)