# Password Provider

A Password Provider is an implementation of the Java interface ome.security.auth.PasswordProvider. Several implementations exist currently:

- ome.security.auth.JdbcPasswordProvider is the most common provider, and uses the “password” table for storing passwords hashed using MD5 and salt per user.

- ome.security.auth.FilePasswordProvider is rarely used, but in some scenarios may be useful since it permits setting usernames and passwords in a plain text file.

- ome.security.auth.LdapPasswordProvider is a highly configurable provider which provides READ-ONLY access to an LDAP server and can create users and groups on the fly. See LDAP plugin design for more information.

The `omero.security.password_provider` property (see Security) defines the implementation of PasswordProvider that will be used to authenticate users. Chains of password providers can be created using ome.security.auth.PasswordProviders. For instance, the default server authentication uses chainedPasswordProvider which first checks the `LdapPasswordProvider` and then falls back to the `JdbcPasswordProvider`.

To write your own provider, you can either subclass from ome.security.auth.ConfigurablePasswordProvider as the providers above do, or write your own implementation from scratch. You will need to define your object and optionally your new chained password providers in a Spring XML file matching the pattern `ome/services/db-*.xml`. See Extending OMERO.server more for information.

## Things to keep in mind

- All the existing implementations take care to publish a LoginAttemptMessage so that any LoginAttemptListener implementation can properly react to failed logins. Your implementation should probably do the same.

- When dealing with chains of password providers, an implementation can safely return null from `checkPassword` to say “I don’t know anything about this”. This is only important if you configure your own chained password provider with your new implementation as one of the elements.

- Due to the service dependency order, new password providers defined in the Spring XML file should be configured with lazy initialization (lazy-init=”true”) so that the beans are only created when needed.