1 files changed, 124 insertions, 0 deletions
diff --git a/src/leap/keymanager/validation.py b/src/leap/keymanager/validation.py
new file mode 100644
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+++ b/src/leap/keymanager/validation.py
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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)
+
+
+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
+    if old_key.key_id in new_key.signatures:
+        return True
+
+    return False