1 class Link < ArvadosModel
4 include CommonApiTemplate
5 serialize :properties, Hash
6 before_create :permission_to_attach_to_objects
7 before_update :permission_to_attach_to_objects
8 after_update :maybe_invalidate_permissions_cache
9 after_create :maybe_invalidate_permissions_cache
10 after_destroy :maybe_invalidate_permissions_cache
15 api_accessible :user, extend: :common do |t|
20 t.add :head, :if => :head
21 t.add :tail, :if => :tail
26 @properties ||= Hash.new
32 def permission_to_attach_to_objects
33 # Anonymous users cannot write links
34 return false if !current_user
36 # All users can write links that don't affect permissions
37 return true if self.link_class != 'permission'
39 # Administrators can grant permissions
40 return true if current_user.is_admin
42 # All users can grant permissions on objects they own
43 head_obj = self.class.
44 kind_class(self.head_uuid).
45 where('uuid=?',head_uuid).
48 return true if head_obj.owner_uuid == current_user.uuid
51 # Users with "can_grant" permission on an object can grant
52 # permissions on that object
53 has_grant_permission = self.class.
54 where('link_class=? AND name=? AND tail_uuid=? AND head_uuid=?',
55 'permission', 'can_grant', current_user.uuid, self.head_uuid).
57 return true if has_grant_permission
63 def maybe_invalidate_permissions_cache
64 if self.link_class == 'permission'
65 # Clearing the entire permissions cache can generate many
66 # unnecessary queries if many active users are not affected by
67 # this change. In such cases it would be better to search cached
68 # permissions for head_uuid and tail_uuid, and invalidate the
69 # cache for only those users. (This would require a browseable
71 User.invalidate_permissions_cache