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SAP CP Java Security Client Library

Token Validation for Java applications.

  • Loads Identity Service Configuration from VCAP_SERVICES environment. The Environments serves as central entry point to get or parse the OAuth2ServiceConfiguration within SAP Cloud Platform.
  • Decodes and parses encoded JSON Web Tokens (Token) and provides convenient access to token header parameters and claims. A Java implementation of JSON Web Token (JWT) - RFC 7519.
  • Validates the decoded token. The JwtValidatorBuilder comprises the following mandatory checks:
    • Is the JWT used before the exp (expiration) time and eventually is it used after the nbf (not before) time (JwtTimestampValidator)?
    • Is the JWT issued by a trust worthy identity service (JwtIssuerValidator)?
      In case of XSUAA does the JWT provide a valid jku token header parameter that points to a JWKS url from a trust worthy identity service (XsuaaJkuValidator) as it matches the uaa domain?
    • Is the JWT intended for the OAuth2 client of this application? The aud (audience) claim identifies the recipients the JWT is issued for (JwtAudienceValidator).
    • Is the JWT signed with the public key of the trust-worthy identity service? With that it also makes sure that the payload and the header of the JWT is unchanged (JwtSignatureValidator)?
  • Provides thread-local cache (SecurityContext) to store the decoded and validated token.
  • Furthermore, it provides an authenticator (TokenAuthenticator) that validates bearer tokens contained in the authorization header of HTTP requests. The authenticator is used in SAP Java Buildpack, as well as in the /samples/java-security-usage*.

Open Source libs used

  • JSON Parser Reference implementation: json.org
  • No crypto library. Leverages Public Key Infrastructure (PKI) provided by Java Security Framework to verify digital signatures.

Supported Environments

  • Cloud Foundry
  • Planned: Kubernetes

Supported Identity Services

  • XSUAA
  • as of version 2.8.0 IAS

Supported Algorithms

JWS Algorithm Description
RS256 RSA256 RSASSA-PKCS1-v1_5 with SHA-256

Configuration

Maven Dependencies

<dependency>
    <groupId>com.sap.cloud.security</groupId>
    <artifactId>java-security</artifactId>
    <version>2.8.4</version>
</dependency>
<dependency>
    <groupId>org.apache.httpcomponents</groupId>
    <artifactId>httpclient</artifactId>
</dependency>

Logging

This library uses slf4j for logging. It only ships the slf4j-api module and no actual logger implementation. For the logging to work slf4j needs to find a valid logger implementation at runtime. If your app is deployed via buildpack then you will have one available and logging should just work.

If there is no valid logger binding at runtime you will see an error message like this:

SLF4J: Failed to load class "org.slf4j.impl.StaticLoggerBinder".
SLF4J: Defaulting to no-operation (NOP) logger implementation

In this case you need to add a logger implementation dependency to your application. See the slf4j documentation for more information and a list of available logger options.

Basic Usage

Setup Step 1: Load the Service Configuration(s)

OAuth2ServiceConfiguration serviceConfig = Environments.getCurrent().getXsuaaConfiguration();

Note: By default Environments auto-detects the environment: Cloud Foundry or Kubernetes.

Alternatively you can also specify the Service Configuration by your own:

OAuth2ServiceConfiguration serviceConfig = OAuth2ServiceConfigurationBuilder.forService(Service.XSUAA)
      .withProperty(CFConstants.XSUAA.APP_ID, "appid")
      .withProperty(CFConstants.XSUAA.UAA_DOMAIN, "authentication.sap.hana.ondemand.com")
      .withUrl("https://paas.authentication.sap.hana.ondemand.com")
      .withClientId("oauth-client")
      .withClientSecret("oauth-client-secret")
      .build();

Setup Step 2: Setup Validators

Now configure the JwtValidatorBuilder once with the service configuration from the previous step.

CombiningValidator<Token> validators = JwtValidatorBuilder.getInstance(serviceConfig).build();

Note: By default JwtValidatorBuilder builds a CombiningValidator. For the Signature validation it needs to fetch the Json Web Token Keys (jwks) from the OAuth server. In case the token does not provide a jku header parameter it also requests the Open-ID Provider Configuration from the OAuth Server to determine the jwks_uri. The used Apache Rest client can be customized via the JwtValidatorBuilder builder.

[Optional] Step 2.1: Add Validation Listeners for Audit Log

Optionally, you can add a validation listener to the validator to be able to get called back whenever a token is validated. Here you may want to emit logs to the audit log service.

JwtValidatorBuilder.getInstance(serviceConfig).withValidatorListener(validationListener);

The validation listener needs to implement the ValidationListener interface to be able to receive callbacks on validation success or failure.

Create a Token Object

This decodes an encoded JSON Web Token (JWT) and parses its json header and payload. The Token interface provides a simple access to its JWT header parameters and its claims. You can find the claim constants in the (TokenClaims) class.

String authorizationHeader = "Bearer eyJhbGciOiJGUzI1NiJ2.eyJhh...";
Token token = new XsuaaToken(authorizationHeader);

Validate Token to check Authentication

ValidationResult result = validators.validate(token);

if(result.isErroneous()) {
   logger.warn("User is not authenticated: " + result.getErrorDescription());
}

Cache validated Token (thread-locally)

SecurityContext.setToken(token);

Get information from Token

Token token = SecurityContext.getToken();

String email = token.getClaimAsString(TokenClaims.EMAIL);
List<String> scopes = token.getClaimAsStringList(TokenClaims.XSUAA.SCOPES);
java.security.Principal principal = token.getPrincipal();
Instant expiredAt = token.getExpiration();
String keyId = token.getHeaderParameterAsString(TokenHeader.KEY_ID);
...

Get further information from VCAP_SERVICES

In case you need further details from VCAP_SERVICES system environment variable, which are not exposed by OAuth2ServiceConfiguration interface you can use the DefaultJsonObject class for Json parsing.

Example:

String vcapServices = System.getenv(CFConstants.VCAP_SERVICES);
JsonObject serviceJsonObject = new DefaultJsonObject(vcapServices).getJsonObjects(Service.XSUAA.getCFName()).get(0);
Map<String, String> xsuaaConfigMap = serviceJsonObject.getKeyValueMap();
Map<String, String> credentialsMap = serviceJsonObject.getJsonObject(CFConstants.CREDENTIALS).getKeyValueMap();

Token based authentication

The servlet authenticator part of this library makes it easy to integrate token based authentication into your java application. For the integration of different Identity Services the TokenAuthenticator interface was created. Right now there are these implementations:

Depending on the application's needs the TokenAuthenticator can be customized.

IAS to Xsuaa token exchange

XsuaaTokenAuthenticator supports seamless token exchange between IAS and Xsuaa. Token exchange between IAS and Xsuaa means that calling a web application endpoint with an IAS Token will work like calling the endpoint with Xsuaa Token. This functionality is disabled by default. Requirement for token exchange is token-client dependency with all its' transitive dependencies(shouldn't be excluded) in the project.

<dependency>
    <groupId>com.sap.cloud.security.xsuaa</groupId>
    <artifactId>token-client</artifactId>
</dependency>

Steps to enable token exchange:

  1. Set environment variable IAS_XSUAA_XCHANGE_ENABLED to any value except false or empty
  2. Make sure token-client is not excluded from the project

The authenticator is used in the following sample.

Test Utilities

You can find the JUnit test utilities documented here.

Enable local testing for XSUAA Identity Service

When you like to test/debug your secured application rest API locally (offline) you need to provide custom VCAP_SERVICES before you run the application. The security library requires the following key value pairs in the VCAP_SERVICES under xsuaa/credentials for jwt validation:

  • "uaadomain" : "localhost"
  • "verificationkey" : "<public key your jwt token is signed with>"

Before calling the service you need to provide a digitally signed JWT token to simulate that you are an authenticated user. You can use the JWTGenerator, which is provided with java-security-test test library.

Now you can test the service manually in the browser using a REST client such as Postman chrome plugin and provide the generated JWT token as Authorization header to access the secured functions.

A detailed step-by-step description and a sample can be found here.

Troubleshoot

In case you face issues, file an issue on Github and provide these details:

Get buildpack version

The buildpack being used is defined in your deployment descriptor e.g. as part of the manifest.yml file via the buildpacks attribute.

If it is set to sap_java_buildpack then the newest available version of the SAP Java buildpack is used. Use command cf buildpacks to get the exact version of sap_java_buildpack:

buildpack                       position   enabled   locked   filename                                             stack
java_buildpack                  2          true      false    java_buildpack-cached-cflinuxfs3-v4.31.1.zip         cflinuxfs3
.
.
.
sap_java_buildpack              12         true      false    sap_java_buildpack-v1.26.1.zip
sap_java_buildpack_1_26         13         true      false    sap_java_buildpack-v1.26.1.zip
sap_java_buildpack_1_25         14         true      false    sap_java_buildpack-v1.25.0.zip

Increase log level to DEBUG

This depends on the SLF4J implementation, you make use of (see also here). You have to set the debug log level for this package com.sap.cloud.security.

... when using SAP Java Buildpack

You should also increase the logging level in your application. This can be done by setting the SET_LOGGING_LEVEL environment variable for your application. You can do this as part of your deployment descriptor such as manifest.yml with the env section like so:

env:
    SET_LOGGING_LEVEL: '{com.sap.xs.security: DEBUG, com.sap.cloud.security: DEBUG}'

After you have made changes to the deployment descriptor you need do re-deploy your app.

For a running application this can also be done with the cf command line tool:

cf set-env <your app name> SET_LOGGING_LEVEL "{com.sap.xs.security: DEBUG, com.sap.cloud.security: DEBUG}"

You need to restage your application for the changes to take effect.

Known Issues

This module requires the JSON-Java library.

If you have classpath related issues involving JSON you should take a look at the Troubleshooting JSON class path issues document.

ServletContext.getAccessToken() returns null

SecurityContext caches only sucessfully validated tokens thread-locally, i.e. within the same thread. Please increase the log level as described here in order to check whether the token validation fails and for which reason.

In case you use SAP Java Buildpack for token validation, make sure that your J2EE Servlet is annotated with a scope check, like:

@ServletSecurity(@HttpConstraint(rolesAllowed = { "yourScope" }))

Or, alternatively in src/main/webapp/WEB-INF/web.xml:

<web-app...
  <security-constraint>
        <web-resource-collection>
            <web-resource-name>All SAP Cloud Platform users</web-resource-name>
            <url-pattern>/*</url-pattern>
        </web-resource-collection>
        <auth-constraint>
            <role-name>YourScope</role-name>
        </auth-constraint>
    </security-constraint>
</web-app>

In case your application provides no scopes, consider the documentation here.

Specs und References

  1. JSON Web Token
  2. OpenID Connect Core 1.0 incorporating errata set 1
  3. OpenID Connect Core 1.0 incorporating errata set 1 - ID Token Validation

Samples

  • Xsuaa Sample
    demonstrating how to leverage java-security library to perform authentication and authorization checks within a Java application when bound to a xsuaa service. Furthermore it documents how to implement JUnit Tests using java-security-test library.

  • Ias Sample
    demonstrating how to leverage java-security library to perform authentication checks within a Java application when bound to a ias identity service. Furthermore it documents how to implement JUnit Tests using java-security-test library.