Applying Security to an API

Using a Basic Auth handler

In most of the real-world use cases of REST, when a consumer attempts to access a privileged resource, access will be denied unless the consumer's credentials are provided in an Authorization header. The ESB profile of WSO2 EI has the capability to validate the credentials of the consumer (that is provided in the Authorization header) against the credentials of users that are registered in the user store connected to the server. This validation is done using the following basic auth handler that is built into the ESB. When a REST API is created, this handler should be added to the API configuration in order to enable basic auth.

Using a custom basic auth handler

If required, you can implement a custom basic auth handler (instead of the default handler explained above). The following example of a primitive security handler serves as a template that can be used to write your own security handler to secure an API in the ESB profile.

Click here to expand...

The custom Basic Auth handler in this sample simply verifies whether the request uses username: admin and password: admin. Following is the code for this handler:

package org.wso2.rest;
import org.apache.commons.codec.binary.Base64;
import org.apache.synapse.MessageContext;
import org.apache.synapse.core.axis2.Axis2MessageContext;
import org.apache.synapse.core.axis2.Axis2Sender;
import org.apache.synapse.rest.Handler;
 
import java.util.Map;
 
public class BasicAuthHandler implements Handler {
    public void addProperty(String s, Object o) {
        //To change body of implemented methods use File | Settings | File Templates.
    }

    public Map getProperties() {
        return null;  //To change body of implemented methods use File | Settings | File Templates.
    }

    public boolean handleRequest(MessageContext messageContext) {

        org.apache.axis2.context.MessageContext axis2MessageContext
                = ((Axis2MessageContext) messageContext).getAxis2MessageContext();
        Object headers = axis2MessageContext.getProperty(
                org.apache.axis2.context.MessageContext.TRANSPORT_HEADERS);

        if (headers != null && headers instanceof Map) {
            Map headersMap = (Map) headers;
            if (headersMap.get("Authorization") == null) {
                headersMap.clear();
                axis2MessageContext.setProperty("HTTP_SC", "401");
                headersMap.put("WWW-Authenticate", "Basic realm=\"WSO2 ESB\"");
                axis2MessageContext.setProperty("NO_ENTITY_BODY", new Boolean("true"));
                messageContext.setProperty("RESPONSE", "true");
                messageContext.setTo(null);
                Axis2Sender.sendBack(messageContext);
                return false;

            } else {
                String authHeader = (String) headersMap.get("Authorization");
                if (processSecurity(credentials)) {
                    return true;
                } else {
                    headersMap.clear();
                    axis2MessageContext.setProperty("HTTP_SC", "403");
                    axis2MessageContext.setProperty("NO_ENTITY_BODY", new Boolean("true"));
                    messageContext.setProperty("RESPONSE", "true");
                    messageContext.setTo(null);
                    Axis2Sender.sendBack(messageContext);
                    return false;
                }
            }
        }
        return false;
    }
 
    public boolean handleResponse(MessageContext messageContext) {
        return true;
    }

    public boolean processSecurity(String credentials) {
        String decodedCredentials = new String(new Base64().decode(credentials.getBytes()));
        String usernName = decodedCredentials.split(":")[0];
        String password = decodedCredentials.split(":")[1];
        if ("admin".equals(username) && "admin".equals(password)) {
            return true;
        } else {
            return false;
        }
    }
}

You can build the project (mvn clean install) for this handler by accessing its source here:

https://github.com/wso2/product-esb/tree/v5.0.0/modules/samples/integration-scenarios/starbucks_sample/BasicAuth-handler

When building the sample using the source ensure you update pom.xml with the online repository. To do this, add the following section before <dependencies>tag in pom.xml:

<repositories>
	<repository>
	   <id>wso2-nexus</id>
	   <name>WSO2 internal Repository</name>
	   <url>http://maven.wso2.org/nexus/content/groups/wso2-public/</url>
	   <releases>
		  <enabled>true</enabled>
		  <updatePolicy>daily</updatePolicy>
		  <checksumPolicy>ignore</checksumPolicy>
	   </releases>
	 </repository>
	 <repository>
	   <id>wso2-maven2-repository</id>
	   <name>WSO2 Maven2 Repository</name>
	   <url>http://dist.wso2.org/maven2</url>
	   <snapshots>
	     <enabled>false</enabled>
	   </snapshots>
	   <releases>
		 <enabled>true</enabled>
		 <updatePolicy>never</updatePolicy>
		 <checksumPolicy>fail</checksumPolicy>
	   </releases>
	</repository>
</repositories>

Alternatively, you can download the JAR file from the following location, copy it to the <EI_HOME>/lib directory, and restart WSO2 EI:

https://github.com/wso2/product-esb/blob/v5.0.0/modules/samples/integration-scenarios/starbucks_sample/bin/WSO2-REST-BasicAuth-Handler-1.0-SNAPSHOT.jar

Add the handler to the REST API:

<api xmlns="http://ws.apache.org/ns/synapse" name="StockQuoteAPI" context="/stockquote">
   <resource methods="GET" uri-template="/view/{symbol}">
      <inSequence>
         <payloadFactory media-type="xml">
            <format>
               <m0:getQuote xmlns:m0="http://services.samples">
                  <m0:request>
                     <m0:symbol>$1</m0:symbol>
                  </m0:request>
               </m0:getQuote>
            </format>
            <args>
               <arg evaluator="xml" expression="get-property('uri.var.symbol')"/>
            </args>
         </payloadFactory>
         <header name="Action" scope="default" value="urn:getQuote"/>
         <send>
            <endpoint>
               <address uri="http://localhost:9000/services/SimpleStockQuoteService" format="soap11"/>
            </endpoint>
         </send>
      </inSequence>
      <outSequence>
         <send/>
      </outSequence>
      <faultSequence/>
   </resource>
   <handlers>
     <handler class="org.wso2.rest.BasicAuthHandler"/>
    </handlers>
</api>

You can now send a request to the secured API.

Using Kerberos to secure the REST API

First, you need to set up the Kerberos server and create the credentials for the ESB server (which hold the REST API). For example, let's set up Active Directory as the kerberos server (KDC):

Download Apache Directory Studio and install the product.
In Active Directory(AD), create a new user as shown below.

Username esbservice
Be sure to select Password does not expire, and deselect User must change password.
Open a terminal and execute the following command to set the Service Principal Name (spn) for the ESB server:
```
setspn -s HTTP/myserver esbservice
```
You will now have the following:

Username esbservice
Service Principal Name HTTP/myserver
Open a terminal and execute the command shown below to g enerate the keytab file for the above service. The keytab file contains the password for the service.
```
ktpass /out wso2.keytab /princ HTTP/myserver@WSO2.TEST /mapuser esbservice /pass servicePassword /crypto All /ptype KRB5_NT_PRINCIPAL
```

Follow the steps given below to apply the Kerberos handler to the ESB server:

Download the WSO2-REST-KerberosAuth-Handler-1.0.0-SNAPSHOT.jar file and copy it to the <EI_HOME>/lib directory.

Create the following REST API and add the Kerberos handler to secure it with Kerberos authentication. Be sure to replace the handler configurations as described below.

<api xmlns="http://ws.apache.org/ns/synapse"
    name="HealthCheckAPI"
    context="/HealthCheck">
  <resource methods="GET" url-mapping="/status" faultSequence="fault">
     <inSequence>
        <payloadFactory media-type="json">
           <format>{"Status":"OK"}</format>
           <args/>
        </payloadFactory>
        <log>
           <property name="JSON-Payload" expression="json-eval($.)"/>
        </log>
        <property name="NO_ENTITY_BODY" scope="axis2" action="remove"/>
        <property name="messageType"
                  value="application/json"
                  scope="axis2"
                  type="STRING"/>
        <respond/>
     </inSequence>
  </resource>
  <handlers>
     <handler class="org.wso2.rest.handler.KerberosAuthHandler">
        <property name="realm" value="WSO2.TEST"/>
        <property name="keyTabFilePath" value="<PATH_TO_KEYTAB_FILE>"/>
        <property name="serverPrincipal" value="HTTP/myserver@WSO2.TEST"/>
     </handler>
  </handlers>
</api>

Kerberos handler parameters:

Property	Description
keyTabFilePath	The file path to the KeyTab file that was generated for the ESB server. Note that this file contains the password corresponding to the server principal name.
serverPrincipal	This is the server principal name (spn) that was generated for the ESB server.

You have now configured a REST API which is secured with the Kerberos authentication.

Using an OAuth base security token

You can generate an OAuth base security token using WSO2 Identity Server, and then use that token when invoking your API to connect to a REST endpoint. This approach involves the following tasks:

Create a custom handler that will validate the token
Create an API that points to the REST endpoint and includes the custom handler
Create an OAuth application in Identity Server and get the access token
Invoke the API with the access token

Creating the custom handler

The custom handler must extend AbstractHandler and implement ManagedLifecycle as shown in the following example. You can download the Maven project for this example at https://github.com/wso2-docs/ESB/tree/master/ESB-Artifacts/OAuthHandler_Sample

package org.wso2.handler;

import org.apache.axis2.AxisFault;
import org.apache.axis2.client.Options;
import org.apache.axis2.client.ServiceClient;
import org.apache.axis2.context.ConfigurationContext;
import org.apache.axis2.context.ConfigurationContextFactory;
import org.apache.axis2.transport.http.HTTPConstants;
import org.apache.axis2.transport.http.HttpTransportProperties;
import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;
import org.apache.http.HttpHeaders;
import org.apache.synapse.core.axis2.Axis2MessageContext;
import org.wso2.carbon.identity.oauth2.stub.OAuth2TokenValidationServiceStub;
import org.wso2.carbon.identity.oauth2.stub.dto.OAuth2TokenValidationRequestDTO;
import org.apache.synapse.ManagedLifecycle;
import org.apache.synapse.MessageContext;
import org.apache.synapse.core.SynapseEnvironment;
import org.apache.synapse.rest.AbstractHandler;
import org.wso2.carbon.identity.oauth2.stub.dto.OAuth2TokenValidationRequestDTO_OAuth2AccessToken;

import java.util.Map;

public class SimpleOauthHandler extends AbstractHandler implements ManagedLifecycle {

    private static final String CONSUMER_KEY_HEADER = "Bearer";
    private static final String OAUTH_HEADER_SPLITTER = ",";
    private static final String CONSUMER_KEY_SEGMENT_DELIMITER = " ";
    private static final String OAUTH_TOKEN_VALIDATOR_SERVICE = "oauth2TokenValidationService";
    private static final String IDP_LOGIN_USERNAME = "identityServerUserName";
    private static final String IDP_LOGIN_PASSWORD = "identityServerPw";
    private ConfigurationContext configContext;
    private static final Log log = LogFactory.getLog(SimpleOauthHandler.class);

    @Override
    public boolean handleRequest(MessageContext msgCtx) {
        if (this.getConfigContext() == null) {
            log.error("Configuration Context is null");
            return false;
        }
        try{
            //Read parameters from axis2.xml
            String identityServerUrl =
                    msgCtx.getConfiguration().getAxisConfiguration().getParameter(
                            OAUTH_TOKEN_VALIDATOR_SERVICE).getValue().toString();
            String username =
                    msgCtx.getConfiguration().getAxisConfiguration().getParameter(
                            IDP_LOGIN_USERNAME).getValue().toString();
            String password =
                    msgCtx.getConfiguration().getAxisConfiguration().getParameter(
                            IDP_LOGIN_PASSWORD).getValue().toString();
            OAuth2TokenValidationServiceStub stub =
                    new OAuth2TokenValidationServiceStub(this.getConfigContext(), identityServerUrl);
            ServiceClient client = stub._getServiceClient();
            Options options = client.getOptions();
            HttpTransportProperties.Authenticator authenticator = new HttpTransportProperties.Authenticator();
            authenticator.setUsername(username);
            authenticator.setPassword(password);
            authenticator.setPreemptiveAuthentication(true);
            options.setProperty(HTTPConstants.AUTHENTICATE, authenticator);
            client.setOptions(options);
            OAuth2TokenValidationRequestDTO dto = this.createOAuthValidatorDTO(msgCtx);
            return stub.validate(dto).getValid();
        }catch(Exception e){
            log.error("Error occurred while processing the message", e);
            return false;
        }
    }
    private OAuth2TokenValidationRequestDTO createOAuthValidatorDTO(MessageContext msgCtx) {
        OAuth2TokenValidationRequestDTO dto = new OAuth2TokenValidationRequestDTO();
        Map headers = (Map) ((Axis2MessageContext) msgCtx).getAxis2MessageContext().
                getProperty(org.apache.axis2.context.MessageContext.TRANSPORT_HEADERS);
        String apiKey = null;
        if (headers != null) {
            apiKey = extractCustomerKeyFromAuthHeader(headers);
        }
        OAuth2TokenValidationRequestDTO_OAuth2AccessToken token =
                new OAuth2TokenValidationRequestDTO_OAuth2AccessToken();
        token.setTokenType("bearer");
        token.setIdentifier(apiKey);
        dto.setAccessToken(token);
        return dto;
    }
    private String extractCustomerKeyFromAuthHeader(Map headersMap) {
        //From 1.0.7 version of this component onwards remove the OAuth authorization header from
        // the message is configurable. So we dont need to remove headers at this point.
        String authHeader = (String) headersMap.get(HttpHeaders.AUTHORIZATION);
        if (authHeader == null) {
            return null;
        }
        if (authHeader.startsWith("OAuth ") || authHeader.startsWith("oauth ")) {
            authHeader = authHeader.substring(authHeader.indexOf("o"));
        }
        String[] headers = authHeader.split(OAUTH_HEADER_SPLITTER);
        if (headers != null) {
            for (String header : headers) {
                String[] elements = header.split(CONSUMER_KEY_SEGMENT_DELIMITER);
                if (elements != null && elements.length > 1) {
                    boolean isConsumerKeyHeaderAvailable = false;
                    for (String element : elements) {
                        if (!"".equals(element.trim())) {
                            if (CONSUMER_KEY_HEADER.equals(element.trim())) {
                                isConsumerKeyHeaderAvailable = true;
                            } else if (isConsumerKeyHeaderAvailable) {
                                return removeLeadingAndTrailing(element.trim());
                            }
                        }
                    }
                }
            }
        }
        return null;
    }
    private String removeLeadingAndTrailing(String base) {
        String result = base;
        if (base.startsWith("\"") || base.endsWith("\"")) {
            result = base.replace("\"", "");
        }
        return result.trim();
    }
    @Override
    public boolean handleResponse(MessageContext messageContext) {
        return true;
    }
    @Override
    public void init(SynapseEnvironment synapseEnvironment) {
        try {
            this.configContext =
                    ConfigurationContextFactory.createConfigurationContextFromFileSystem(null, null);
        } catch (AxisFault axisFault) {
            log.error("Error occurred while initializing Configuration Context", axisFault);
        }
    }
    @Override
    public void destroy() {
        this.configContext = null;
    }
    private ConfigurationContext getConfigContext() {
        return configContext;
    }
}

Creating the API

You will now create an API named TestGoogle that connects to the following endpoint: https://www.google.lk/search?q=wso2

In WSO2 EI Management Console, go to Manage -> Service Bus and click Source View.

Insert the following XML configuration into the source view before the closing </definitions> tag to create the TestGoogle API:

 <api xmlns="http://ws.apache.org/ns/synapse"
     name="TestGoogle"
     context="/search">
   <resource methods="GET">
      <inSequence>
         <log level="full">
           <property name="STATUS" value="***** REQUEST HITS IN SEQUENCE *****"/>
         </log>
         <send>
            <endpoint>
               <http method="get" uri-template="https://www.google.lk/search?q=wso2"/>
            </endpoint>
         </send>
      </inSequence>
   </resource>
   <handlers>
       <handler class="org.wso2.handler.SimpleOauthHandler"/>
   </handlers>
</api>

Notice that the <handlers> tag contains the reference to the custom handler class.

Copy the custom handler.jar to the <EI_HOME>/lib directory.

Open <EI_HOME>/repository/axis2/axis2.xml and add the following parameters:

<!-- OAuth2 Token Validation Service -->
<parameter name="oauth2TokenValidationService">https://localhost:9444/services/OAuth2TokenValidationService</parameter>
<!-- Server credentials -->
<parameter name="identityServerUserName">admin</parameter>
<parameter name="identityServerPw">admin</parameter>

Restart WSO2 EI.

Getting the OAuth token

You will now use Identity Server to create an OAuth application and generate the security token.

Start WSO2 Identity Server and log into the management console.
On the Main tab, click Add under Service Providers, and then add a service provider .
Note the access token URL and embed it in a cURL request to get the token. For example, use the following command and replace <client-id> and <client secret> with the actual values:

curl -v -k -X POST --user <client-id>:<client secret> -H "Content-Type: application/x-www-form-urlencoded;charset=UTF-8" -d 'grant_type=password&username=admin&password=admin' https://localhost:9444/oauth2/token

Identity Server returns the access token, which you can now use when invoking the API. For example:

curl -v -X GET -H "Authorization: Bearer ca1799fc84986bd87c120ba499838a7" http://localhost:8280/search

Using a policy file to authenticate with a secured back-end service

You can connect a REST client to a secured back-end service (such as a SOAP service) through an API that reads from a policy file.

First, you configure the ESB profile to expose the API to the REST client. For example:

<definitions xmlns="http://ws.apache.org/ns/synapse">
   <localEntry key="sec_policy"
               src="file:repository/samples/resources/policy/policy_3.xml"/>
  <api name="StockQuoteAPI" context="/stockquote">
      <resource methods="GET" uri-template="/view/{symbol}">e
         <inSequence trace="enable">
            <header name="Action" value="urn:getQuote"/>
            <payloadFactory>
               <format>
                  <m0:getQuote xmlns:m0="http://services.samples">
                     <m0:request>
                        <m0:symbol>$1</m0:symbol>
                     </m0:request>
                  </m0:getQuote>
               </format>
               <args>
                  <arg expression="get-property('uri.var.symbol')"/>
               </args>
            </payloadFactory>
            <send>
               <endpoint name="rest">
                  <address uri="http://localhost:9000/services/SecureStockQuoteService"
                           format="soap11">
                     <enableAddressing/>
                     <enableSec policy="sec_policy"/>
                  </address>
               </endpoint>
            </send>
            </inSequence>
         <outSequence trace="enable">
            <header xmlns:wsse="http://docs.oasis-open.org/wss/2004/01/oasis-200401-wss-wssecurity-secext-1.0.xsd"
                    name="wsse:Security"
                    action="remove"/>
            <send/>
         </outSequence>
      </resource>
      <resource methods="POST">
         <inSequence>
            <property name="FORCE_SC_ACCEPTED" value="true" scope="axis2"/>
            <property name="OUT_ONLY" value="true"/>
            <send>
               <endpoint>
                  <address uri="http://localhost:9000/services/SimpleStockQuoteService"
                           format="soap11"/>
               </endpoint>
            </send>
         </inSequence>
      </resource>
   </api>
</definitions>

The policy file stores the security parameters that are going to authenticated by the back-end service. You specify the policy file with the localEntry property, which in this example we've named sec_policy:

<localEntry key="sec_policy"
               src="file:repository/samples/resources/policy/policy_3.xml"/>

You use then reference the policy file by its localEntry name when enabling the security policy for the end point:

<address uri="http://localhost:9000/services/SecureStockQuoteService"
    format="soap11">
    <enableAddressing/>
    <enableSec policy="sec_policy"/>
</address>

In the outSequence property, the security header must be removed before sending the response back to the REST client.

<outSequence trace="enable">
            <header xmlns:wsse="http://docs.oasis-open.org/wss/2004/01/oasis-200401-wss-wssecurity-secext-1.0.xsd"
                    name="wsse:Security"
                    action="remove"/>

To test this API configuration, you must run the SecureStockQuoteService, which is bundled in the samples folder, as the back-end server. Start this sample as described in /wiki/spaces/EI6xx/pages/49610865. This sample uses Apache Rampart as the back-end security implementation. Therefore, you need to download and install the unlimited strength policy files for your JDK before using Apache Rampart.

To download and install the unlimited strength policy files:

Go to http://www.oracle.com/technetwork/java/javase/downloads/jce8-download-2133166.html, and download the unlimited strength JCE policy files for your JDK version.
Uncompress and extract the downloaded ZIP file. This creates a directory named JCE that contains the local_policy.jar and US_export_policy.jar files.
In your Java installation directory, go to the jre/lib/security directory, make a copy of the existing local_policy.jar and US_export_policy.jar files, and then replace the original policy files with the policy files you extracted in the previous step.

Now that you have set up the API and the secured back-end SOAP service, you are ready to test this configuration with the following curl command.

curl -v http://127.0.0.1:8280/stockquote/view/IBM

Observe that the REST client is getting the correct response (the wsse:Security header is removed from the decrypted message) while going through the secured back-end service and the API implemented in the WSO2 EI. You can use a TCP monitoring tool such as tcpmon to monitor the message sent from the the ESB profile and the response message received by the ESB profile. For a tutorial on using tcpmon, see: http://technonstop.com/tcpmon-tutorial

Transforming Basic Auth to WS-Security

REST clients typically use Basic Auth over HTTP to authenticate the user name and password, but if the back-end service uses WS-Security, you can configure the API to transform the authentication from Basic Auth to WS-Security.

To achieve this transformation, you configure the ESB profile to expose the API to the REST client as shown in the previous example, but you add the HTTPS protocol and Basic Auth handler to the configuration as shown below:

<definitions xmlns="http://ws.apache.org/ns/synapse">
  <localEntry key="sec_policy"
src="file:repository/samples/resources/policy/policy_3.xml"/>
  <api name="StockQuoteAPI" context="/stockquote">
    <resource methods="GET" uri-template="/view/{symbol}" protocol="https" >
     ...
    </resource>
    <handlers>
      <handler class="org.wso2.rest.BasicAuthHandler"/>
    </handlers>
  </api>
</definitions>

This configuration allows two-fold security: the client authenticates with the API using Basic Auth over HTTPS, and then the API sends the request to the back-end service using the security policy. You can test this configuration using the following command:

 curl -v -k -H "Authorization: Basic YWRtaW46YWRtaW4=" https://localhost:8243/stockquote/view/IBM

Username	esbservice
Service Principal Name	HTTP/myserver