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# -*- coding: utf-8 -*-
# wrapper.py
# Copyright (C) 2016 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/>.
"""
GPG wrapper for temporary keyrings
"""
import os
import shutil
import tempfile
from gnupg import GPG
from leap.common.check import leap_assert
class TempGPGWrapper(object):
"""
A context manager that wraps a temporary GPG keyring which only contains
the keys given at object creation.
"""
def __init__(self, keys=None, gpgbinary=None):
"""
Create an empty temporary keyring and import any given C{keys} into
it.
:param keys: OpenPGP key, or list of.
:type keys: OpenPGPKey or list of OpenPGPKeys
:param gpgbinary: Name for GnuPG binary executable.
:type gpgbinary: C{str}
"""
self._gpg = None
self._gpgbinary = gpgbinary
if not keys:
keys = list()
if not isinstance(keys, list):
keys = [keys]
self._keys = keys
def __enter__(self):
"""
Build and return a GPG keyring containing the keys given on
object creation.
:return: A GPG instance containing the keys given on object creation.
:rtype: gnupg.GPG
"""
self._build_keyring()
return self._gpg
def __exit__(self, exc_type, exc_value, traceback):
"""
Ensure the gpg is properly destroyed.
"""
# TODO handle exceptions and log here
self._destroy_keyring()
def _build_keyring(self):
"""
Create a GPG keyring containing the keys given on object creation.
:return: A GPG instance containing the keys given on object creation.
:rtype: gnupg.GPG
"""
privkeys = [key for key in self._keys if key and key.private is True]
publkeys = [key for key in self._keys if key and key.private is False]
# here we filter out public keys that have a correspondent
# private key in the list because the private key_data by
# itself is enough to also have the public key in the keyring,
# and we want to count the keys afterwards.
privfps = map(lambda privkey: privkey.fingerprint, privkeys)
publkeys = filter(
lambda pubkey: pubkey.fingerprint not in privfps, publkeys)
listkeys = lambda: self._gpg.list_keys()
listsecretkeys = lambda: self._gpg.list_keys(secret=True)
self._gpg = GPG(binary=self._gpgbinary,
homedir=tempfile.mkdtemp())
leap_assert(len(listkeys()) is 0, 'Keyring not empty.')
# import keys into the keyring:
# concatenating ascii-armored keys, which is correctly
# understood by GPG.
self._gpg.import_keys("".join(
[x.key_data for x in publkeys + privkeys]))
# assert the number of keys in the keyring
leap_assert(
len(listkeys()) == len(publkeys) + len(privkeys),
'Wrong number of public keys in keyring: %d, should be %d)' %
(len(listkeys()), len(publkeys) + len(privkeys)))
leap_assert(
len(listsecretkeys()) == len(privkeys),
'Wrong number of private keys in keyring: %d, should be %d)' %
(len(listsecretkeys()), len(privkeys)))
def _destroy_keyring(self):
"""
Securely erase the keyring.
"""
# TODO: implement some kind of wiping of data or a more
# secure way that
# does not write to disk.
try:
for secret in [True, False]:
for key in self._gpg.list_keys(secret=secret):
self._gpg.delete_keys(
key['fingerprint'],
secret=secret)
leap_assert(len(self._gpg.list_keys()) is 0, 'Keyring not empty!')
except:
raise
finally:
leap_assert(self._gpg.homedir != os.path.expanduser('~/.gnupg'),
"watch out! Tried to remove default gnupg home!")
shutil.rmtree(self._gpg.homedir)
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