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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
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