Custom mediator

An OAuth 2.0 mediator is used as a callback during the OAuth 2.0 message processing to perform customized post processing.

Write an OAuth20 mediator

To write a mediator, implement the interface...

com.ibm.oauth.core.api.oauth20.mediator.OAuth20Mediator

We can implement one or more mediate* methods to perform custom post processing.

void init(OAuthComponentConfiguration config)

Method called by a factory when an instance of this object is created.

void mediateAuthorize(AttributeList attributeList)

Method called by the core component after basic message validation and processing to allow any post custom processing by the component consumer in the processAuthorization method.

void mediateAuthorizeException(AttributeList attributeList, OAuthException exception)

Method called by the core component when the protocol exception happens to allow any post custom processing by the component consumer in the processAuthorization method.

void mediateResource(AttributeList attributeList)

Method called by the core component after basic message validation and processing to allow any post custom processing by the component consumer in the processResourceRequest method.

void mediateResourceException(AttributeList attributeList, OAuthException exception)

Method called by the core component when protocol exception happens to allow any post custom processing by the component consumer in the processResourceRequest method.

void mediateToken(AttributeList attributeList)

Method called by the core component after basic message validation and processing to allow any post custom processing by the component consumer in the processTokenRequest method.

void mediateTokenException(AttributeList attributeList, OAuthException exception)

Method called by the core component when protocol exception happens to allow any post custom processing by the component consumer in the processTokenRequest method.

Enable OAuth20 mediator for an OAuth provider

To add a customized mediator to a specific OAuth20 service provider, update the configuration file for the service provider, for example, OAuthConfigSample.xml. Locate the oauth20.mediator.classnames parameter and add the class name for the mediators. We can also specify multiple class names for mediators for the oauth20.mediator.classnames parameters. If multiple mediators are specified, those mediators are started in the order they are specified in the parameter. The following example shows a sample custom mediator entry in the provider configuration file:

<parameter name="oauth20.mediator.classnames" type="cc" customizable="false">

  <value>org.acme.oauth2.sampleMediator</value>

  <value>org.acme.oauth2.sampleMediator2</value>

</parameter>

The following code sample implements the credential validation using WebSphere Application Server user registry in the resource owner password credentials flow.

package com.ibm.ws.security.oauth20.mediator;

import com.ibm.oauth.core.api.attributes.AttributeList;
import com.ibm.oauth.core.api.config.OAuthComponentConfiguration;
import com.ibm.oauth.core.api.error.OAuthException;
import com.ibm.oauth.core.api.error.oauth20.OAuth20MediatorException;
import com.ibm.oauth.core.api.oauth20.mediator.OAuth20Mediator;
import com.ibm.oauth.core.internal.oauth20.OAuth20Constants;
import com.ibm.websphere.security.CustomRegistryException;
import com.ibm.websphere.security.PasswordCheckFailedException;
import com.ibm.websphere.security.UserRegistry;

import java.rmi.RemoteException;
import java.util.logging.Level;
import java.util.logging.Logger;

import javax.naming.InitialContext;
import javax.naming.NamingException;

public class ResourceOwnerValidationMedidator implements OAuth20Mediator {
  private static final String CLASS = ResourceOwnerValidationMedidator.class.getName();
  private static final Logger LOG = Logger.getLogger(CLASS);
  private UserRegistry reg = null;

  public void init(OAuthComponentConfiguration config) {
    try {
      InitialContext ctx = new InitialContext();
      reg = (UserRegistry) ctx.lookup("UserRegistry");
    } catch(NamingException ne) {
      LOG.log(Level.SEVERE, "Cannot lookup UserRegistry", ne);
    }  }  public void mediateAuthorize(AttributeList attributeList)
    throws OAuth20MediatorException {
    // nothing to do here
  }  public void mediateAuthorizeException(AttributeList attributeList,
                                        OAuthException exception)
    throws OAuth20MediatorException {
    // nothing to do here
  }  public void mediateResource(AttributeList attributeList)
    throws OAuth20MediatorException {
    // nothing to do here
  }  public void mediateResourceException(AttributeList attributeList,
                                       OAuthException exception)
    throws OAuth20MediatorException {
    // nothing to do here
  }  public void mediateToken(AttributeList attributeList)
    throws OAuth20MediatorException {
    final String methodName = "mediateToken";
    LOG.entering(CLASS, methodName, attributeList);
    if("password".equals(attributeList.getAttributeValueByName("grant_type"))) {
      String username = attributeList.getAttributeValueByName("username");
      String password = attributeList.getAttributeValueByName("password");
      try {
        reg.checkPassword(username, password);
      } catch (PasswordCheckFailedException e) {
        throw new OAuth20MediatorException("User doesn't exist or the
                                           password doesn't match.", e);
      } catch (CustomRegistryException e) {
        throw new OAuth20MediatorException("Cannot validate resource owner.", e);
      } catch (RemoteException e) {
        throw new OAuth20MediatorException("Cannot validate resource owner.", e);
      } 
    }    LOG.exiting(CLASS, methodName);
  }  public void mediateTokenException(AttributeList attributeList,
                                    OAuthException exception)
    throws OAuth20MediatorException {
    final String methodName = "mediateTokenException";
    LOG.entering(CLASS, methodName, new Object[] {attributeList, exception});
    if("password".equals(attributeList.getAttributeValueByName("grant_type"))) {
      // clear sensitive data
      attributeList.setAttribute("access_token",
                                 OAuth20Constants.ATTRTYPE_RESPONSE_ATTRIBUTE,
                                 new String[0]);
      attributeList.setAttribute("refresh_token",
                                 OAuth20Constants.ATTRTYPE_RESPONSE_ATTRIBUTE,
                                 new String[0]);
    }    LOG.exiting(CLASS, methodName);
  }}

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