The Security.Auth package implements an authentication framework that is suitable for OpenID 2.0, OAuth 2.0 and later for OpenID Connect. It allows an application to authenticate users using an external authorization server such as Google, Facebook, Google +, Twitter and others.

See OpenID Authentication 2.0 - Final

See OpenID Connect Core 1.0

See Facebook API: The Login Flow for Web (without JavaScript SDK)

Despite their subtle differences, all these authentication frameworks share almost a common flow. The API provided by Security.Auth defines an abstraction suitable for all these frameworks.

There are basically two steps that an application must implement:

  • Discovery: to resolve and use the OpenID provider and redirect the user to the provider authentication form.
  • Verify: to decode the authentication and check its result.

The authentication process is the following:

  • The application should redirect the user to the authentication URL.
  • The OpenID provider authenticate the user and redirects the user to the callback CB.
  • The association is decoded from the callback parameter.
  • The Verify procedure is called with the association to check the result and obtain the authentication results.


The initialization process must be done before each two steps (discovery and verify). The Authentication manager must be declared and configured.

Mgr   : Security.Auth.Manager;

For the configuration, the Initialize procedure is called to configure the Auth realm and set the authentication return callback URL. The return callback must be a valid URL that is based on the realm. Example:

Mgr.Initialize (Name      => "",
                Return_To => "",
                Realm     => "openid");

After this initialization, the authentication manager can be used in the authentication process.

OpenID Configuration

The Open ID provider needs the following configuration parameters:

openid.realm          The OpenID realm parameter passed in the authentication URL.
openid.callback_url   The OpenID return_to parameter.


The Google+ authentication is based on OAuth 2.0 and the OpenID Connect Basic Client Profile.


Discovery: creating the authentication URL

The first step is to create an authentication URL to which the user must be redirected. In this step, we have to create an OpenID manager, discover the OpenID provider, do the association and get an End_Point. The OpenID provider is specified as an URL, below is an example for Google OpenID:

Provider : constant String := "";
OP       : Security.Auth.End_Point;
Assoc    : constant Security.Auth.Association_Access := new Security.Auth.Association;

The following steps are performed:

  • The Discover procedure is called to retrieve from the OpenID provider the XRDS stream and identify the provider. An End_Point is returned in OP.
  • The Associate procedure is called to make the association with the End_Point. The Association record holds session, and authentication.
Mgr.Discover (Provider, OP);  --  Yadis discovery (get the XRDS file).
Mgr.Associate (OP, Assoc.all);--  Associate and get an end-point with a key.

After this first step, you must manage to save the association in the HTTP session. Then you must redirect to the authentication URL that is obtained by using:

Auth_URL : constant String := Mgr.Get_Authentication_URL (OP, Assoc.all);

Verify: acknowledge the authentication in the callback URL

The second step is done when the user has finished the authentication successfully or not. For this step, the application must get back the association that was saved in the session. It must also prepare a parameters object that allows the OpenID framework to get the URI parameters from the return callback.

Assoc      : Association_Access := ...;  --  Get the association saved in the session.
Credential : Security.Auth.Authentication;
Params     : Auth_Params;

The auth manager must be initialized and the Verify procedure is called with the association, parameters and the authentication result. The Get_Status function must be used to check that the authentication succeeded.

Mgr.Verify (Assoc.all, Params, Credential);
if Security.Auth.Get_Status (Credential) = Security.Auth.AUTHENTICATED then ...  -- Success.

Principal creation

After the user is successfully authenticated, a user principal can be created and saved in the session. The user principal can then be used to assign permissions to that user and enforce the application permissions using the security policy manger.

P : Security.Auth.Principal_Access := Security.Auth.Create_Principal (Credential);