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# -*- coding: utf-8 -*-
# crypto.py
# Copyright (C) 2013 LEAP
#
# This program is free software: you can redistribute it and/or modify
# it under the terms of the GNU 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 General Public License for more details.
#
# You should have received a copy of the GNU General Public License
# along with this program. If not, see <http://www.gnu.org/licenses/>.
"""
Cryptographic utilities for Soledad.
"""
from binascii import b2a_base64
from hashlib import sha256
from leap.common.keymanager import KeyManager
from leap.soledad.util import GPGWrapper
class NoSymmetricSecret(Exception):
"""
Raised when trying to get a hashed passphrase.
"""
class SoledadCrypto(object):
"""
General cryptographic functionality.
"""
def __init__(self, gnupg_home, symkey=None):
"""
Initialize the crypto object.
@param gnupg_home: Home of the gpg instance.
@type gnupg_home: str
@param symkey: A key to use for symmetric encryption.
@type symkey: str
"""
self._gpg = GPGWrapper(gnupghome=gnupg_home)
self._symkey = symkey
def encrypt(self, data, recipients=None, sign=None, passphrase=None,
symmetric=False):
"""
Encrypt data.
@param data: the data to be encrypted
@type data: str
@param recipients: to whom C{data} should be encrypted
@type recipients: list or str
@param sign: the fingerprint of key to be used for signature
@type sign: str
@param passphrase: the passphrase to be used for encryption
@type passphrase: str
@param symmetric: whether the encryption scheme should be symmetric
@type symmetric: bool
@return: the encrypted data
@rtype: str
"""
return str(self._gpg.encrypt(data, recipients, sign=sign,
passphrase=passphrase,
symmetric=symmetric))
def encrypt_symmetric(self, data, passphrase, sign=None):
"""
Encrypt C{data} using a {password}.
@param data: the data to be encrypted
@type data: str
@param passphrase: the passphrase to use for encryption
@type passphrase: str
@param data: the data to be encrypted
@param sign: the fingerprint of key to be used for signature
@type sign: str
@return: the encrypted data
@rtype: str
"""
return self.encrypt(data, sign=sign,
passphrase=passphrase,
symmetric=True)
def decrypt(self, data, passphrase=None):
"""
Decrypt data.
@param data: the data to be decrypted
@type data: str
@param passphrase: the passphrase to be used for decryption
@type passphrase: str
@return: the decrypted data
@rtype: str
"""
return str(self._gpg.decrypt(data, passphrase=passphrase))
def decrypt_symmetric(self, data, passphrase):
"""
Decrypt data using symmetric secret.
@param data: the data to be decrypted
@type data: str
@param passphrase: the passphrase to use for decryption
@type passphrase: str
@return: the decrypted data
@rtype: str
"""
return self.decrypt(data, passphrase=passphrase)
def is_encrypted(self, data):
"""
Test whether some chunk of data is a cyphertext.
@param data: the data to be tested
@type data: str
@return: whether the data is a cyphertext
@rtype: bool
"""
return self._gpg.is_encrypted(data)
def is_encrypted_sym(self, data):
"""
Test whether some chunk of data was encrypted with a symmetric key.
@return: whether data is encrypted to a symmetric key
@rtype: bool
"""
return self._gpg.is_encrypted_sym(data)
def is_encrypted_asym(self, data):
"""
Test whether some chunk of data was encrypted to an OpenPGP private
key.
@return: whether data is encrypted to an OpenPGP private key
@rtype: bool
"""
return self._gpg.is_encrypted_asym(data)
def _hash_passphrase(self, suffix):
"""
Generate a passphrase for symmetric encryption.
The password is derived from C{suffix} and the secret for
symmetric encryption previously loaded.
@param suffix: Will be appended to the symmetric key before hashing.
@type suffix: str
@return: the passphrase
@rtype: str
@raise NoSymmetricSecret: if no symmetric secret was supplied.
"""
if self._symkey is None:
raise NoSymmetricSecret()
return b2a_base64(
sha256('%s%s' % (self._symkey, suffix)).digest())[:-1]
#
# symkey setters/getters
#
def _get_symkey(self):
return self._symkey
def _set_symkey(self, symkey):
self._symkey = symkey
symkey = property(_get_symkey, _set_symkey,
doc='The key used for symmetric encryption')
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