[feature] keymanager: background update keys

Port of the original commit:
8f1fe8dd4a54fd2bdda2fc78c339ce9b3d0fc331
by Zara Gebru that introduced updating keys in the background.

This was made in the legacy leapcode/keymanager repo, but was lost in
the merge to the unified bitmask-dev.

Original commit message follows:
--------------------------------

- refresh random key in random time
- add get key by fingerprint
- refactor nicknym methods to own file
- tests

- note this do not include a check for
revoked key, since that need some changes
in gnupg

- Related: #6089

1 files changed, 132 insertions, 0 deletions

diff --git a/src/leap/bitmask/keymanager/refresher.py b/src/leap/bitmask/keymanager/refresher.py
new file mode 100644
index 0000000..cd9db28
--- /dev/null
+++ b/src/leap/bitmask/keymanager/refresher.py
@@ -0,0 +1,132 @@
+# -*- coding: utf-8 -*-
+# refresher.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/>.
+
+
+"""
+A service which continuous refreshes the (public) key directories randomly in a random time interval.
+"""
+
+import logging
+
+from twisted.internet.task import LoopingCall
+from twisted.internet import defer
+from random import choice, randrange
+
+DEBUG_STOP_REFRESH = "Stop to refresh the key directory ..."
+DEBUG_START_REFRESH = "Start to refresh the key directory ..."
+ERROR_UNEQUAL_FINGERPRINTS = "[WARNING] Your provider might be cheat on you, " \
+                             "and gave a wrong key back. Fingerprints are unequal, old %s new %s "
+
+MIN_RANDOM_INTERVAL_RANGE = 4 * 60  # four minutes
+MAX_RANDOM_INTERVAL_RANGE = 6 * 60  # six minutes
+
+logger = logging.getLogger(__name__)
+
+
+class RandomRefreshPublicKey(object):
+
+    def __init__(self, openpgp, keymanager):
+        """
+        Initialize the RandomRefreshPublicKey.
+        :param openpgp: Openpgp object.
+        :param keymanager: The key manager.
+        """
+        self._openpgp = openpgp
+        self._keymanger = keymanager
+        self._loop = LoopingCall(self._refresh_continuous)
+        self._loop.interval = self._random_interval_to_refersh()
+
+    def start(self):
+        """
+        Start the looping call with random interval
+        [MIN_RANDOM_INTERVAL_RANGE, MAX_RANDOM_INTERVAL_RANGE]
+        :return: LoopingCall to start the service.
+        :rtype: A deferred.
+        """
+        self._loop.start(self._random_interval_to_refersh(), False)
+        logger.debug(DEBUG_START_REFRESH)
+
+    def stop(self):
+        """
+        Stop the looping call with random interval.
+        """
+        self._loop.stop()
+        logger.debug(DEBUG_STOP_REFRESH)
+
+    @defer.inlineCallbacks
+    def _get_random_key(self):
+        """
+        Get a random key of all the keys in a users key doc.
+        :return: A random key.
+        :rtype: A deferred.
+        """
+        # TODO maybe make a check first if key is active and get another one then.
+        keys = yield self._openpgp.get_all_keys()
+        defer.returnValue(None if keys is None or keys == [] else choice(keys))
+
+    @defer.inlineCallbacks
+    def _refresh_continuous(self):
+        """
+        The LoopingCall to refresh the key doc continuously.
+        """
+        self._loop.interval = self._random_interval_to_refersh()
+        yield self.maybe_refresh_key()
+
+    @defer.inlineCallbacks
+    def _maybe_unactivate_key(self, key):
+        """
+        Unactivate a given key.
+        :param key: The key to be unactivated.
+        """
+        if key.is_expired() and key.is_active():  # TODO or is_revoked
+            yield self._openpgp.unactivate_key(key.address)
+            key.set_unactive()
+
+    @defer.inlineCallbacks
+    def maybe_refresh_key(self):
+        """
+        Get key from nicknym and try to refresh.
+        """
+        old_key = yield self._get_random_key()
+
+        if old_key is None:
+            defer.returnValue(None)
+
+        old_updated_key = yield self._keymanger._nicknym.\
+            fetch_key_with_fingerprint(old_key.fingerprint)
+
+        if old_updated_key.fingerprint != old_key.fingerprint:
+            logger.error(ERROR_UNEQUAL_FINGERPRINTS %
+                         (old_key.fingerprint, old_updated_key.fingerprint))
+            defer.returnValue(None)
+
+        yield self._maybe_unactivate_key(old_updated_key)
+        yield self._openpgp.put_key(old_updated_key)
+
+        # No new fetch by address needed, bc that will happen before sending an email
+        # could be discussed since fetching before sending an email leaks information.
+
+    def _random_interval_to_refersh(self):
+        """
+        Random interval.
+        :return: A number in this interval.
+        """
+        return randrange(MIN_RANDOM_INTERVAL_RANGE, MAX_RANDOM_INTERVAL_RANGE)
+
+
+
+