Writing Custom Authentication Handlers

WSO2 App Manager provides SAML SSO as its default authentication mechanism. For information on the implementation of handlers, go to the source code. Similarly, you can extend App Manager to support any custom authentication mechanism by writing your own authentication handler class. This custom handler must extend org.apache.synapse.rest.AbstractHandler class and implement the handleRequest() and handleResponse() methods.

Given below is an example implementation:

package org.wso2.carbon.apimgt.gateway.handlers.security;

import org.apache.synapse.MessageContext;
import org.apache.synapse.core.axis2.Axis2MessageContext;
import org.apache.synapse.rest.AbstractHandler;

import java.util.Map;

public class CustomAPIAuthenticationHandler extends AbstractHandler {

    public boolean handleRequest(MessageContext messageContext) {
        try {
            if (authenticate(messageContext)) {
                return true;
            }
        } catch (APISecurityException e) {
            e.printStackTrace();
        }
        return false;
    }

    public boolean handleResponse(MessageContext messageContext) {
        return true;  
    }

    public boolean authenticate(MessageContext synCtx) throws APISecurityException {
        Map headers = getTransportHeaders(synCtx);
        String authHeader = getAuthorizationHeader(headers);
        if (authHeader.startsWith("userName")) {
            return true;
        }
        return false;
    }

    private String getAuthorizationHeader(Map headers) {
        return (String) headers.get("Authorization");
    }

    private Map getTransportHeaders(MessageContext messageContext) {
        return (Map) ((Axis2MessageContext) messageContext).getAxis2MessageContext().
                getProperty(org.apache.axis2.context.MessageContext.TRANSPORT_HEADERS);
    }
}

Follow the steps below to write a custom authentication handler.

Implement the custom handler according to the above example.
Build the class and copy the JAR file to <PRODUCT_HOME>/repository/components/lib/ folder.
Log in to the management console and click Service Bus and then click Source View in the Main menu.
In the ESB configuration that opens, the following line appears. This is the current authentication handler used in App Manager.
```
<handler class="org.wso2.carbon.appmgt.gateway.handlers.security.saml2.SAML2AuthenticationHandler"/>
```
Replace the above line with the handler that you created to engage your custom handler to the App Manager instance. According to this example, it is as follows:
```
<handler class="org.wso2.carbon.appmgt.gateway.handlers.security.saml2.CustomAPIAuthenticationHandler"/>
```