Adding support for additional username/password-based authentication backends

ArchivesSpace supports LDAP-based authentication out of the box, but you can authenticate against other password-based user directories by defining your own authentication handler, creating a plug-in, and configuring your ArchivesSpace instance to use it. If you would rather not have to create your own handler, there is a plug-in available that uses OAUTH user authentication that you can add to your ArchivesSpace installation.

Creating a new authentication handler class to use in a plug-in

An authentication handler is just a class that implements a couple of key methods:

• initialize(opts) – An object constructor which receives the configuration block specified in the system’s configuration.
• name – A zero-argument method which just returns a string that identifies the instance of your handler. The format of this string isn’t important: it just gets stored as a user attribute (in the ArchivesSpace database) to make it possible to tell which authentication source a user last successfully authenticated against.
• authenticate(username, password) – a method which checks whether password is the correct password for username. If the password is correct, returns an instance of JSONModel(:user). Otherwise, returns nil.

A new instance of your handler will be created for each login attempt, so there’s no need to handle concurrency in your implementation.

Your authenticate method can do whatever is required to check that the provided password is correct, with the only constraint being that it must return either nil or a JSONModel(:user) instance.

The JSONModel(:user) class (whose JSON schema is defined in common/schemas/user.rb) defines the set of properties that the system needs for a user. When you return a JSONModel(:user) object, its values will be used to create an ArchivesSpace user (if a user by that name didn’t exist already), or update the existing user (if they were already known).

Note: The JSONModel(:user) class validates the values you give it against its JSON schema and throws an JSONModel::ValidationException if anything isn’t right. If this happens within your handler, the exception will be logged and the authentication request will fail.

A skeleton implementation

Suppose you already have a database with a table containing users that should be able to log in to ArchivesSpace. Below is a sketch of an authentication handler that will connect to this database and use it for authentication.

  # For this example we'll use the Sequel database toolkit.  Note that
  # this isn't necessary--you could use whatever database library you
  # like here.
  require 'sequel'

  class MyDatabaseAuth

    # For easy access to the JSONModel(:user) class
    include JSONModel


    def initialize(definition)
      # Store the database connection details for use at
      # authentication time.
      @db_url = definition[:db_url] or raise "Need a value for :db_url"
    end


    # Just for informational purposes.  Return a string containing our
    # database URL.
    def name
      "MyDatabaseAuth - #{@db_url}"
    end


    def authenticate(username, password)
      # Open a connection to the database
      Sequel.connect(@db_url) do |db|

        # Check whether we have an entry for the given username
        # and password in our database's "users" table
        user = db[:users].filter(:username => username,
                                 :password => password).
                          first

        if !user
          # The user couldn't be found, or their password was wrong.
          # Authentication failed.
          return nil
        end

        # Build and return a JSONModel(:user) instance from fields in the database
        JSONModel(:user).from_hash(:username => username,
                                   :name => user[:user_full_name])

      end
    end

  end

In order to use your new authentication handler, you’ll need to add it to the plug-in architecture in ArchivesSpace and enable it. Create a new directory, called our_auth perhaps, in the plugins directory of your ArchivesSpace installation. Inside that directory create this directory hierarchy backend/model/ and place the new class file there. Next, configure the new handler.

Modifying your configuration

To have ArchivesSpace invoke your new authentication handler, just add a new entry to the :authentication_sources configuration block in the config/config.rb file.

A configuration for the above example might be as follows:

 AppConfig[:authentication_sources] = [{
                                         :model => 'MyDatabaseAuth',
                                         :db_url => 'jdbc:mysql://localhost:3306/somedb?user=myuser&password=mypassword',
                                       }]

Add the plug-in to the list of plug-ins already enabled

In the config/config.rb file, find the setting of AppConfig[:plugins] and add a reference to the new plug-in there. For example, if you named it our_auth, the AppConfig[:plugins] setting may look something like this:

AppConfig[:plugins] = [‘local’, ‘hello_world’, ‘our_auth’]

Restart your ArchivesSpace installation and you should now see authentication requests hitting your new handler.