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+# -*- coding: utf-8 -*-
+# __init__.py
+# Copyright (C) 2014 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/>.
+
+"""
+Validation levels implementation for key managment.
+
+See:
+ https://leap.se/en/docs/design/transitional-key-validation
+"""
+
+
+from datetime import datetime
+
+
+class ValidationLevel(object):
+ """
+ A validation level
+
+ Meant to be used to compare levels or get its string representation.
+ """
+ def __init__(self, name, value):
+ self.name = name
+ self.value = value
+
+ def __cmp__(self, other):
+ return cmp(self.value, other.value)
+
+ def __str__(self):
+ return self.name
+
+ def __repr__(self):
+ return "<ValidationLevel: %s (%d)>" % (self.name, self.value)
+
+
+class _ValidationLevels(object):
+ """
+ Handler class to manage validation levels. It should have only one global
+ instance 'ValidationLevels'.
+
+ The levels are attributes of the instance and can be used like:
+ ValidationLevels.Weak_Chain
+ ValidationLevels.get("Weak_Chain")
+ """
+ _level_names = ("Weak_Chain",
+ "Provider_Trust",
+ "Provider_Endorsement",
+ "Third_Party_Endorsement",
+ "Third_Party_Consensus",
+ "Historically_Auditing",
+ "Known_Key",
+ "Fingerprint")
+
+ def __init__(self):
+ for name in self._level_names:
+ setattr(self, name,
+ ValidationLevel(name, self._level_names.index(name)))
+
+ def get(self, name):
+ """
+ Get the ValidationLevel of a name
+
+ :param name: name of the level
+ :type name: str
+ :rtype: ValidationLevel
+ """
+ return getattr(self, name)
+
+ def __iter__(self):
+ return iter(self._level_names)
+
+
+ValidationLevels = _ValidationLevels()
+
+
+def can_upgrade(new_key, old_key):
+ """
+ :type new_key: EncryptionKey
+ :type old_key: EncryptionKey
+ :rtype: bool
+ """
+ # First contact
+ if old_key is None:
+ return True
+
+ # An update of the same key
+ if new_key.fingerprint == old_key.fingerprint:
+ return True
+
+ # Manually verified fingerprint
+ if new_key.validation == ValidationLevels.Fingerprint:
+ return True
+
+ # Expired key and higher validation level
+ if (old_key.expiry_date is not None and
+ old_key.expiry_date < datetime.now() and
+ new_key.validation >= old_key.validation):
+ return True
+
+ # No expiration date and higher validation level
+ if (old_key.expiry_date is None and
+ new_key.validation > old_key.validation):
+ return True
+
+ # Not successfully used and strict high validation level
+ if (not (old_key.sign_used and old_key.encr_used) and
+ new_key.validation > old_key.validation):
+ return True
+
+ # New key signed by the old key
+ # XXX: signatures are using key-ids instead of fingerprints
+ key_id = old_key.fingerprint[-16:]
+ if key_id in new_key.signatures:
+ return True
+
+ return False