services/api/lib/can_be_an_owner.rb

   1 # Copyright (C) The Arvados Authors. All rights reserved.
   2 #
   3 # SPDX-License-Identifier: AGPL-3.0
   4
   5 # Protect referential integrity of owner_uuid columns in other tables
   6 # that can refer to the uuid column in this table.
   7
   8 module CanBeAnOwner
   9
  10   def self.included(base)
  11     base.extend(ClassMethods)
  12
  13     # Rails' "has_many" can prevent us from destroying the owner
  14     # record when other objects refer to it.
  15     ActiveRecord::Base.connection.tables.each do |t|
  16       next if t == base.table_name
  17       next if t == 'schema_migrations'
  18       klass = t.classify.constantize
  19       next unless klass and 'owner_uuid'.in?(klass.columns.collect(&:name))
  20       base.has_many(t.to_sym,
  21                     foreign_key: :owner_uuid,
  22                     primary_key: :uuid,
  23                     dependent: :restrict_with_exception)
  24     end
  25     # We need custom protection for changing an owner's primary
  26     # key. (Apart from this restriction, admins are allowed to change
  27     # UUIDs.)
  28     base.validate :restrict_uuid_change_breaking_associations
  29   end
  30
  31   module ClassMethods
  32     def install_view(type)
  33       conn = ActiveRecord::Base.connection
  34       transaction do
  35         # Check whether the temporary view has already been created
  36         # during this connection. If not, create it.
  37         conn.exec_query "SAVEPOINT check_#{type}_view"
  38         begin
  39           conn.exec_query("SELECT 1 FROM #{type}_view LIMIT 0")
  40         rescue
  41           conn.exec_query "ROLLBACK TO SAVEPOINT check_#{type}_view"
  42           sql = File.read(Rails.root.join("lib", "create_#{type}_view.sql"))
  43           conn.exec_query(sql)
  44         ensure
  45           conn.exec_query "RELEASE SAVEPOINT check_#{type}_view"
  46         end
  47       end
  48     end
  49   end
  50
  51   def descendant_project_uuids
  52     self.class.install_view('ancestor')
  53     ActiveRecord::Base.connection.
  54       exec_query('SELECT ancestor_view.uuid
  55                   FROM ancestor_view
  56                   LEFT JOIN groups ON groups.uuid=ancestor_view.uuid
  57                   WHERE ancestor_uuid = $1 AND groups.group_class = $2',
  58                   # "name" arg is a query label that appears in logs:
  59                   "descendant_project_uuids for #{self.uuid}",
  60                   # "binds" arg is an array of [col_id, value] for '$1' vars:
  61                   [[nil, self.uuid], [nil, 'project']],
  62                   ).rows.map do |project_uuid,|
  63       project_uuid
  64     end
  65   end
  66
  67   protected
  68
  69   def restrict_uuid_change_breaking_associations
  70     return true if new_record? or not uuid_changed?
  71
  72     # Check for objects that have my old uuid listed as their owner.
  73     self.class.reflect_on_all_associations(:has_many).each do |assoc|
  74       next unless assoc.foreign_key == :owner_uuid
  75       if assoc.klass.where(owner_uuid: uuid_was).any?
  76         errors.add(:uuid,
  77                    "cannot be changed on a #{self.class} that owns objects")
  78         return false
  79       end
  80     end
  81
  82     # if I owned myself before, I'll just continue to own myself with
  83     # my new uuid.
  84     if owner_uuid == uuid_was
  85       self.owner_uuid = uuid
  86     end
  87   end
  88 end