Accessing Claim Aware Services using STS Secured with Non-repudiation

Usually, WSO2 Identity Server (IS) Security Token Service (STS) is secured using UsernameToken. By doing so, claims related to a particular user can be easily retrieved from a userstore.

However, there can be situations where STS is secured using non-repudiation, in which case the users are authenticated by signing the Request for Security Token (RST) using their private key. At the STS side, claims should be retrieved based on the user's X.509 certificate's Common Name (CN), if the STS trusts the user.

An extension point is used to address this scenario in WSO2 Identity Server. A custom attribute finder for non-repudiation scenario is written and given to IS to execute. This section discusses how to achieve this using WSO2 Identity Server and WSO2 Enterprise Service Bus. Additionally, an STS Sample is used which can be downloaded here. This sts-sample includes executables as well as the source files with an Eclipse project that was configured using Maven.

Use the following steps to run this scenario:

Adding a Custom Attribute Finder to IS

The following is the source code of a custom attribute finder. It simply parses the distinguished name of the certificate and extracts the value of CN, which is used as the identifier to query the user store for claims.

package org.wso2.carbon.identity.resource.sts.attributeservice.x509;
 
import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;
import org.apache.rahas.RahasData;
import org.apache.rahas.impl.util.SAMLAttributeCallback;
import org.opensaml.SAMLException;
import org.wso2.carbon.identity.provider.AttributeCallbackHandler;
import org.wso2.carbon.identity.provider.IdentityAttributeService;
 
public class X509AttributeService extends AttributeCallbackHandler implements IdentityAttributeService {
 
    private static Log log = LogFactory.getLog(X509AttributeService.class);
 
    public void handle(SAMLAttributeCallback attrCallback) throws SAMLException {
        RahasData data = null;
        String userIdentifier = null;
        String[] splitArr;
     
        try {
                data = attrCallback.getData();
                splitArr = data.getPrincipal().getName().split(",")[0].split("=");
     
                if (splitArr.length == 2) {
                    userIdentifier = splitArr[1];
                    loadClaims(userIdentifier);
                    processClaimData(data, data.getClaimElem());
                    populateClaimValues(userIdentifier, attrCallback);
                }   
        }   
        catch (Exception e) {
            log.error("Error occuerd while populating claim data", e); 
        }   
    }   
}

You can download the compiled version of this - org.wso2.carbon.identity.resource.sts.attributeservice.x509-1.0.0.jar - from here.

Copy this into the {IS_HOME}/repository/components/dropins folder.

Configuring Key Stores

The following steps generate a key pair for the particular user you are interested in client's key store, and add his/her certificate to IS' key store.

If you are using the key store of the sts-sample downloaded (which is located at sts-sample/src/main/resources/keystore/wso2carbon.jks), and if you want to test with the "admin" user, skip step 1.

Generate a new key pair in client's key store with the CN "admin" (or any other, if you want to test a different user in the IS user store).
```
keytool -genkey -keyalg RSA -alias admin -keypass admin123 -keystore path/to/client/wso2carbon.jks -storepass wso2carbon -dname "CN=admin"
```

Generate a certificate from the key pair.

keytool -export -alias admin -file path/to/admin.cert -keystore path/to/client/wso2carbon.jks -storepass wso2carbon

Import the new certificate to {IS_HOME}/repository/resources/security/wso2carbon.jks.

keytool -import -alias admin -file path/to/admin.cert -keystore path/to/server/wso2carbon.jks -storepass wso2carbon

When it asks "Trust this certificate? [no]:" at the end of above command, enter yes.

Running the Servers

In ESB, change the "Offset" value to 1 in {ESB_HOME}/repository/conf/carbon.xml. This allows you to run both IS and ESB servers parallelly. IS runs on the default port 9443 and ESB on 9444.

Start both servers by executing the following:

{IS_HOME}/bin/wso2server.sh and {ESB_HOME}/bin/wso2server.sh on Linux.

or

{IS_HOME}/bin/wso2server.bat and {ESB_HOME}/bin/wso2server.bat on Windows.

Securing an Echo Service (the Relying Party) in ESB

Add a custom policy to the registry.
1. Create a new collection (which is essentially a folder) to maintain custom policies.
2. Add the service-policy.xml located at 'sts-sample/src/main/resources/' to this collection.
Secure the echo service with the custom policy.
1. Go to the Services list and click the Unsecured link of the echo service.
2. Select Yes in the "Enable Security?" option.
3. Give the path of the policy file we uploaded to registry, in the Policy From Registry section at the end of the page.
4. Click Next.
5. In the following page, select wso2carbon.jks as the Trusted Key Store.

The end service is successfully configured now.

Add ESB's Echo Service as a Trusted Service of STS

In the Security Token Service page (Main > Manage > Security Token Service) of the WSO2 Identity Server, Add new trusted service with the following details:

Endpoint Address = http://localhost:8281/services/echo

Certificate Alias = wso2carbon

Secure STS with Non-repudiation

Click Apply on the above screen.
Select "Yes" in the "Enable Security?" option.
Select scenario 2 - Non-repudiation, and click Next.
On the following page, as we did for ESB, select 'wos2carbon.jks' as the Trusted Key Store.

Ensure Necessary Claims are Added to the User

The echo service requires first name and the email address as the claims (refer service-policy.xml).
Check the user profile of the particular user ("admin" in default case) to make sure the values for those claims are available.

Both ESB and IS are now configured.

Testing with the STS Client

The following are the (partially clipped) sources that make up the Client.

Client.java can invoke token issue binding on STS, as well as send the request to the echo service.

public class Client {
 
    ...
     
    public static void main(String[] args) {
        Client client = new Client();
        client.run();
    }
 
    private void run() {
        try {
            loadConfigurations();
 
            // set the trust store as a system property for communication over
            // TLS.
            System.setProperty("javax.net.ssl.trustStore", keystorePath);
            System.setProperty("javax.net.ssl.trustStorePassword", keystorePwd);
 
            // create configuration context
            ConfigurationContext configCtx = ConfigurationContextFactory
                    .createConfigurationContextFromFileSystem(repoPath);
 
            // create STS client
            STSClient stsClient = new STSClient(configCtx);
            stsClient.setRstTemplate(getRSTTemplate());
 
            String action = null;
            String responseTokenID = null;
 
            action = TrustUtil.getActionValue(RahasConstants.VERSION_05_02,
                    RahasConstants.RST_ACTION_ISSUE);
            stsClient.setAction(action);
 
            // request the security token from STS.
            Token responseToken;
             
            Policy stsPolicy = loadPolicy(stsPolicyPath);
 
            // add rampart config assertion to the ws-sec policies
            RampartConfig rampartConfig = buildRampartConfig();
            stsPolicy.addAssertion(rampartConfig);
             
            responseToken = stsClient.requestSecurityToken(null, stsEPR, stsPolicy, relyingPartyEPR);
 
            // store the obtained token in token store to be used in future
            // communication.
            TokenStorage store = TrustUtil.getTokenStore(configCtx);
            responseTokenID = responseToken.getId();
            store.add(responseToken);
 
            // print token
            System.out.println(responseToken.getToken().toString());
 
            ...
 
            //Send the token to relying party
            if (enableRelyingParty) {
                /* Invoke secured service using the obtained token */
                OMElement responseElem = null;
 
                // create service client
                ServiceClient serClient = new ServiceClient(configCtx, null);
 
                // engage modules
                serClient.engageModule("addressing");
                serClient.engageModule("rampart");
 
                // load policy of secured service
                Policy sec_policy = loadPolicy(relyingPartyPolicyPath);
 
                // add rampart config to the ws-sec policies
                sec_policy.addAssertion(rampartConfig);
 
                // set in/out security policies in client opts
                serClient.getOptions().setProperty(RampartMessageData.KEY_RAMPART_POLICY,
                        sec_policy);
 
                // Set the token id as a property in the Axis2 client scope, so that
                // this will be picked up when creating the secure message to invoke
                // the endpoint.
                serClient.getOptions().setProperty(RampartMessageData.KEY_CUSTOM_ISSUED_TOKEN,
                        responseTokenID);
 
                // set action of the Hello Service to be invoked.
                serClient.getOptions().setAction("urn:echoString");
                serClient.getOptions().setTo(new EndpointReference(relyingPartyEPR));
 
                // invoke the service
                responseElem = serClient.sendReceive(getPayload(echoRequestMsg));
                // cleanup transports
                serClient.getOptions().setCallTransportCleanup(true);
 
                System.out.println(responseElem.toString());
                 
                System.exit(0);
            }
        } catch (IOException e) {
            e.printStackTrace();
        } catch (TrustException e) {
            e.printStackTrace();
        } catch (XMLStreamException e) {
            e.printStackTrace();
        }
    }
 
    private OMElement getRSTTemplate() throws TrustException {
        OMFactory omFac = OMAbstractFactory.getOMFactory();
        OMElement element = omFac.createOMElement(SP11Constants.REQUEST_SECURITY_TOKEN_TEMPLATE);
 
        if (ClientConstants.SAML_TOKEN_TYPE_20.equals(tokenType)) {
            TrustUtil.createTokenTypeElement(RahasConstants.VERSION_05_02, element).setText(
                    RahasConstants.TOK_TYPE_SAML_20);
        } else if (ClientConstants.SAML_TOKEN_TYPE_11.equals(tokenType)) {
            TrustUtil.createTokenTypeElement(RahasConstants.VERSION_05_02, element).setText(
                    RahasConstants.TOK_TYPE_SAML_10);
        }
 
        if (ClientConstants.SUBJECT_CONFIRMATION_BEARER.equals(subjectConfirmationMethod)) {
            TrustUtil.createKeyTypeElement(RahasConstants.VERSION_05_02, element,
                    RahasConstants.KEY_TYPE_BEARER);
        } else if (ClientConstants.SUBJECT_CONFIRMATION_HOLDER_OF_KEY
                .equals(subjectConfirmationMethod)) {
            TrustUtil.createKeyTypeElement(RahasConstants.VERSION_05_02, element,
                    RahasConstants.KEY_TYPE_SYMM_KEY);
        }
 
        // request claims in the token.
        OMElement claimElement = TrustUtil.createClaims(RahasConstants.VERSION_05_02, element,claimDialect);
        // Populate the <Claims/> element with the <ClaimType/> elements
        addClaimType(claimElement, claimUris);
 
        return element;
    }
 
    private void addClaimType(OMElement parent, String[] claimUris) {
        OMElement element = null;
        // For each and every claim uri, create an <ClaimType/> elem
        for (String attr : claimUris) {
            element = parent.getOMFactory()
                    .createOMElement(
                            new QName("http://schemas.xmlsoap.org/ws/2005/05/identity",
                                    "ClaimType", "wsid"), parent);
            element.addAttribute(parent.getOMFactory().createOMAttribute("Uri", null, attr));
        }
    }
 
    private Policy loadPolicy(String policyPath) throws XMLStreamException, FileNotFoundException {
        StAXOMBuilder omBuilder = new StAXOMBuilder(policyPath);
        return PolicyEngine.getPolicy(omBuilder.getDocumentElement());
    }
 
    private RampartConfig buildRampartConfig() {
        RampartConfig rampartConfig = new RampartConfig();
        rampartConfig.setUser(username);
        rampartConfig.setEncryptionUser(encryptionUser);
        rampartConfig.setUserCertAlias(userCertAlias);
        rampartConfig.setPwCbClass(pwdCallbackClass);
 
        Properties cryptoProperties = new Properties();
        cryptoProperties.put("org.apache.ws.security.crypto.merlin.keystore.type", "JKS");
        cryptoProperties.put("org.apache.ws.security.crypto.merlin.file", keystorePath);
        cryptoProperties
                .put("org.apache.ws.security.crypto.merlin.keystore.password", keystorePwd);
 
        CryptoConfig cryptoConfig = new CryptoConfig();
        cryptoConfig.setProvider("org.apache.ws.security.components.crypto.Merlin");
        cryptoConfig.setProp(cryptoProperties);
 
        rampartConfig.setEncrCryptoConfig(cryptoConfig);
        rampartConfig.setSigCryptoConfig(cryptoConfig);
 
        return rampartConfig;
    }
 
    private OMElement getPayload(String value) {
        OMFactory factory = null;
        OMNamespace ns = null;
        OMElement elem = null;
        OMElement childElem = null;
 
        factory = OMAbstractFactory.getOMFactory();
        ns = factory.createOMNamespace("http://echo.services.core.carbon.wso2.org", "ns");
        elem = factory.createOMElement("echoString", ns);
        childElem = factory.createOMElement("in", null);
        childElem.setText(value);
        elem.addChild(childElem);
 
        return elem;
    }
     
    ...
}

PasswordCBHandler.java is used by the underlying Rampart module to get the password of the key alias which is used to sign the request.

public class PasswordCBHandler implements CallbackHandler{
     
    ...
     
    public void handle(Callback[] callbacks) throws IOException, UnsupportedCallbackException {
 
        readUsernamePasswordFromProperties();
         
        WSPasswordCallback pwcb = (WSPasswordCallback) callbacks[0];
        String id = pwcb.getIdentifier();
        int usage = pwcb.getUsage();
 
        if (usage == WSPasswordCallback.USERNAME_TOKEN) {
 
           if (username.equals(id)) {
               pwcb.setPassword(password);
           }
        } else if (usage == WSPasswordCallback.SIGNATURE || usage == WSPasswordCallback.DECRYPT) {
 
            if (keyAlias.equals(id)) {
                pwcb.setPassword(keyPassword);
            }
        }
    }
     
    ...
}

You can configure the client by using the 'sts-sample/src/main/resources/client.properties' file. By default, it is configured to run the client in SAML2 and 'Bearer' subject confirmation modes using "admin" as the user.

There are scripts named sts-client.sh and sts-client.bat included in the sts-sample download. By using them, you can directly run the client without much hassle.

Upon execution, you can see an output similar to the following: