Custom OAuth Grant-Type Support in APIManager

According to OAuth 2.0 Spec , there are four main grant-types support is available in an OAuth 2.0 authorization server. It supports custom grant type also. WSO2 IS supports OAuth 2.0 spec and it can act as OAuth 2.0 authorization server.

WSO2 APIManager uses OAuth tokens for API Security. (APIManager uses IS OAuth component to achieve OAuth support). User can write his own gran-type support for API security.

For this, he has to write; 

1. GrantTypeHandler : Write the grant type implementation in the handler class. For this implementation user can use AuthorizationGrantHandler  interface or by extending AbstractAuthorizationGrantHandler
2. GrantTypeValidator: This implementation will validates all the request which are sent to token endpoint. For this implementation, use the "AbstractValidator" class which is available in Amber library from Apache.

Eg: For example, If i want to authorize the requests based on certificates (e.g.;. Grant-type is "cert-auth",) 

OauthHandler:

package org.test.oauth;

import org.wso2.carbon.identity.oauth2.IdentityOAuth2Exception;
import org.wso2.carbon.identity.oauth2.model.RequestParameter;
import org.wso2.carbon.identity.oauth2.token.OAuthTokenReqMessageContext;
import org.wso2.carbon.identity.oauth2.token.handlers.grant.AbstractAuthorizationGrantHandler;
import org.wso2.carbon.identity.oauth2.dto.OAuth2AccessTokenReqDTO;

public class CertificateGrantHandler extends AbstractAuthorizationGrantHandler{

public static final String CERTIFICATE = "sslclientcertb64";

@Override

    public boolean validateGrant(OAuthTokenReqMessageContext tokReqMsgCtx)

            throws IdentityOAuth2Exception {

        boolean authStatus = false;

        

    OAuth2AccessTokenReqDTO oAuth2AccessTokenReqDTO = tokReqMsgCtx.getOauth2AccessTokenReqDTO();

   

    String clientCert = null;

    // extract request parameters

        RequestParameter[] parameters = oAuth2AccessTokenReqDTO.getRequestParameters();

        // find out client certificate

        for(RequestParameter parameter : parameters){

            if(CERTIFICATE.equals(parameter.getKey())){

                if(parameter.getValue() != null && parameter.getValue().length > 0){

                clientCert = parameter.getValue()[0];

                }

            }

        }        

    return authStatus;

    }

}

Validator:


package org.test.oauth;

import org.apache.amber.oauth2.common.validators.AbstractValidator;
import javax.servlet.http.HttpServletRequest;

public class CertificateGrantValidator  extends AbstractValidator {

    public OauthCertificateGrantValidator() {

        // mobile number must be in the request parameter
        requiredParams.add(OauthCertificateGrantHandler.CERTIFICATE);
    }
}

Add the new grant-type in the identity.xml of the APIManager.

eg:

<SupportedGrantType>
<GrantTypeName>cert_auth</GrantTypeName>
<GrantTypeHandlerImplClass>org.test.oauth.CertificateGrantHandler</GrantTypeHandlerImplClass>
<GrantTypeValidatorImplClass>org.test.oauth.CertificateGrantValidator</GrantTypeValidatorImplClass>
</SupportedGrantType>

Generate token using;
curl -k -d "grant_type=cert_auth&sslclientcertb64=" -H "Authorization: Basic , Content-Type: application/x-www-form-urlencoded" http://localhost:8280/token

Register Axis2 MessageBuilder Programmatically

For each  Content-type, we define message builders and formatters in the axis2 configuration(axis2.xml). Those Builders and Formatters are global configuration. In some cases, we need to handle  certain messages belong to a certain content-type  in different manner.

For example, We configure text/xml content-type messages to be handled by a message builder implementaion in axis2 configuration. But, if same content-ype messages to be handled in different manner in a different message flow, we can register MessageBuilder/Formatter programmatically in that particular message flow. This will not affect the normal message building process for the same content -type messages in other flows.

Eg:
Registering PlainTextBuilder implementation to handle SOAP messages.

Builder messagebuilder = null;
Class c = Class.forName("org.apache.axis2.format.PlainTextBuilder");

Object obj = c.newInstance();
if (obj instanceof Builder) {
messagebuilder = (Builder) obj;
}
org.apache.axis2.context.MessageContext axis2MsgContext;
axis2MsgContext.getConfigurationContext().getAxisConfiguration().addMessageBuilder("text/xml", messagebuilder);

Adding URL parameters in WSO2 APIManager

It is a common use case, where users might want to add URL parameters  which are evaluated dynamically in their endpoints.
We can use same approach what we do in ESB, but it may confuse users on how to implement it in APIManager.
APIManager supports adding custom sequences for the API mediation logic. There are few ways available to add custom mediation plugins.
One, which we can simply use for this requirement is, store the mediation logic in registry as a sequence and select that in the in/out flow of the API invocation when publishing API.

Eg:

If we want to invoke the API with something like(note: we pass PhoneNumber parameter)
http://localhost:8280/dimtry/1.0?PhoneNumber=+16506697051 and send to the backend: http://ws.cdyne.com/phoneverify/phoneverify.asmx/CheckPhoneNumber? PhoneNumber=+16506697051&LicenseKey=0"

In the above example, backend service expects two URL parameters for the GET call to return proper response. But user will pass only one parameter(i.e.: phone number). We need to extract that user parameter and within api mediation logic we need to add another license key parameter too.

To achieve this, When publish an API define HTTP endpoint with parameters and assign values to those parameters in the custom sequence.

Eg: <http uri-template=" http://ws.cdyne.com/phoneverify/phoneverify.asmx/CheckPhoneNumber?Phonenumber={uri.var.PhoneNumber}&LicenseKey={uri.var.LicenseKey}"/>


Here, you need to pass two parameters, which can be passed through the custom sequence. Edit the existing log-in message sequence like below and save;(you can create new sequence and save it)

<sequence xmlns="http://ws.apache.org/ns/synapse" name="log_in_message">

                <property name="uri.var.LicenseKey" value="0" scope="default" type="STRING"/>

                <property name="uri.var.PhoneNumber" expression="substring-after(get-property('To'),'/dimtry/1.0?PhoneNumber=')" scope="default" type="STRING"/>

</sequence>

If you check above sequence,  phonumber is extracted from incoming request using an xpath and hardcoded a value for licensekey, which user can modify according to his requirement.
Now when  we create and publish the api, select above insequence.

APIConfiguration:

Send a GET request for the API like;

http://localhost:8280/dimtry/1.0?PhoneNumber=+16506697051

You will get response;