This library provides a lightweight HTTP client for Xsuaa /oauth/token and /token_keys endpoints, as specified here.
Additionally, it offers an API with the XsuaaTokenFlows class to support the following token flows:
- Jwt Bearer Token Flow.
The token exchange concept aims to segregate service-specific access scopes into separate tokens. For instance, if Service A and Service B have different scopes, the goal is to avoid having a single Jwt token containing all scopes. To achieve principal propagation in that scenario, Service A could use a Jwt Bearer Token Flow before making requests to Service B on behalf of the user. To do so, he would exchange the user's access token for Service A for an access token of the same user for Service B. - Client Credentials Flow.
The Client Credentials (RFC 6749, section 4.4) are employed by clients to acquire an access token without a user context. This is useful for non-interactive applications (e.g., CLI, batch job, or service-2-service communication) where the token is issued to the application itself, instead of an end-user for accessing resources without principal propagation. - Refresh Token Flow.
A Refresh Token (RFC 6749, section 1.5) flow enables obtaining a new access token if the current one becomes invalid or expires. - Password Token Flow.
Resource owner password credentials (i.e., username and password) can be used directly as an authorization grant to obtain an access token (RFC 6749, section 1.3.3). These credentials should be employed only when there is a high degree of trust between the resource owner and the client.
Note: The Authorization Code Grant Flow requires a browser and is typically initiated by an API gateway, such as an Application Router. However, other flows might need to be triggered programmatically, such as swapping one token for another or refreshing a token prior to its expiration. When creating an Xsuaa service instance, an OAuth client is generated, and the client Identity (client ID and secret or client certificate and key) are supplied when you bind your application to the Xsuaa service instance. With these elements in place, you can leverage the token flows in your Java application.
For Spring Boot applications TokenFlows come autoconfigured with our spring-security or spring-xsuaa libraries and can be easily consumed by autowiring the XsuaaTokenFlows Bean. For more details see 1.1. Configuration for Spring Applications section.
For a Java EE application you will need to provide
OAuth2ServiceConfiguration and HttpClientFactory to set up XsuaaTokenFlows. See 1.2. Configuration for Java EE Applications section for more details.
There is also a Cache provided that caches up to 1000 tokens for 10 minutes. For Spring Boot autoconfigured XsuaaTokenFlows it is only possible to disable cache per each request.
If you want to change cache settings you have to overwrite the autoconfigured XsuaaTokenFlows Bean.
See more details in Cache section.
In context of a Spring Boot application you can leverage autoconfiguration provided by the following library:
<dependency>
<groupId>com.sap.cloud.security</groupId>
<artifactId>resourceserver-security-spring-boot-starter</artifactId>
<version>3.5.6</version>
</dependency>In context of Spring Applications you will need the following dependencies:
<dependency>
<groupId>com.sap.cloud.security.xsuaa</groupId>
<artifactId>token-client</artifactId>
<version>3.5.6</version>
</dependency>
<dependency>
<groupId>org.apache.httpcomponents</groupId>
<artifactId>httpclient</artifactId>
</dependency>As autoconfiguration requires Spring Boot specific dependencies, it is enabled when using resourceserver-security-spring-boot-starter Spring Boot Starter.
Then spring-security library autoconfigures beans, that are required to initialize the Token Flows API.
| Auto-configuration class | Description |
|---|---|
| XsuaaTokenFlowAutoConfiguration | Configures a XsuaaTokenFlows bean with the xsuaaServiceConfiguration Bean and tokenFlowHttpClient Bean |
To consume the XsuaaTokenFlows class, you simply need to @Autowire it like this:
@Autowired
private XsuaaTokenFlows xsuaaTokenFlows;For non Spring Boot Applications or if the XsuaaTokenFlowAutoConfiguration doesn't fit to your use case you can provide your own XsuaaTokenFlows Bean.
import com.sap.cloud.security.annotation.Beta;
import com.sap.cloud.security.client.HttpClientFactory;
import com.sap.cloud.security.config.OAuth2ServiceConfiguration;
import com.sap.cloud.security.xsuaa.tokenflows.XsuaaTokenFlows;
@Configuration
public class CustomConfiguration {
@Bean
public OAuth2ServiceConfiguration customServiceConfiguration() {
return OAuth2ServiceConfigurationBuilder.forService(Service.XSUAA)
.withClientId(...)
.withCertificate(...)
.withPrivateKey(...)
.withUrl(...)
.withCertUrl(...).build();
}
@Bean
public CloseableHttpClient customHttpClient(OAuth2ServiceConfiguration customServiceConfiguration) {
return HttpClientFactory.create(customServiceConfiguration.getClientIdentity());
}
@Bean
public XsuaaTokenFlows customTokenFlows(CloseableHttpClient customHttpClient, OAuth2ServiceConfiguration customServiceConfiguration) {
return new XsuaaTokenFlows(
new DefaultOAuth2TokenService(customHttpClient),
new XsuaaDefaultEndpoints(customServiceConfiguration),
customServiceConfiguration.getClientIdentity()
);
}
}See the OAuth2ServiceConfiguration section and HttpClientFactory for more detailed information about the involved classes.
<dependency>
<groupId>com.sap.cloud.security.xsuaa</groupId>
<artifactId>token-client</artifactId>
<version>3.5.6</version>
</dependency>
<dependency>
<groupId>org.apache.httpcomponents</groupId>
<artifactId>httpclient</artifactId>
</dependency>XsuaaTokenFlows tokenFlows = new XsuaaTokenFlows(
new DefaultOAuth2TokenService(CloseableHttpClient),
new XsuaaDefaultEndpoints(OAuth2ServiceConfiguration),
OAuth2ServiceConfiguration.getClientIdentity()));The XsuaaTokenFlows needs to be instantiated with a DefaultOAuth2TokenService, XsuaaDefaultEndpoints and ClientIdentity.
-
OAuth2ServiceConfigurationis placeholder for the Identity service configuration, see here how to initialize it -
CloseableHttpClientis a placeholder for the Apache HTTP client, see here how to initialize it
OAuth2ServiceConfiguration holds the information from the respective Identity service binding and is used in XsuaaTokenFlows initialization.
When using spring-xsuaa or spring-security client libraries, a readily configured OAuth2ServiceConfiguration is accessible via XsuaaServiceConfiguration Bean.
Alternatively, the env library provides a convenient way to obtain bound Identity service configurations by reading information from the VCAP_SERVICES environment variable or K8s secrets and mapping it to an instance of the OAuth2ServiceConfiguration class. You can use it as follows:
OAuth2ServiceConfiguration config = Environments.getCurrent().getXsuaaConfiguration();If you need to fetch a token from a specific Identity service instance that is not bound to your application, e.g. the uaa service configuration of your job scheduler, you need to initialize an OAuth2ServiceConfiguration manually. You can use the OAuth2ServiceConfigurationBuilder provided by the env library for this purpose.
OAuth2ServiceConfigurationBuilder builder = OAuth2ServiceConfigurationBuilder.forService(Service.XSUAA);
OAuth2ServiceConfiguration config = builder.withClientId(...)
.withClientSecret(...)
.withCertificate(...)
.withPrivateKey(...)
.withUrl(...)
.withCertUrl(...).build();To utilize an externally managed certificate in
-
Java EE application: you need to modify the
OAuth2ServiceConfigurationinstance with the external key:OAuth2ServiceConfigurationBuilder builder = OAuth2ServiceConfigurationBuilder.fromConfiguration(Environments.getCurrent().getXsuaaConfiguration()); OAuth2ServiceConfiguration config = builder.withPrivateKey("-----BEGIN RSA PRIVATE KEY ... END RSA PRIVATE KEY-----").build();
-
Spring Boot applications: A
ClientCertificateneeds to be instantiated with the external key and theXsuaaTokenFlowsbean needs to be overwritten using thisClientCertificateinstance.
Alternatively you can provide the certificate key property programmatically by defining default property.@SpringBootApplication public class Application { public static void main(String[] args) { SpringApplication application = new SpringApplication(Application.class); Properties properties = new Properties(); properties.put("xsuaa.key", "-----BEGIN RSA PRIVATE KEY ... END RSA PRIVATE KEY-----"); // when using spring-xsuaa properties.put("sap.security.services.xsuaa.key", "-----BEGIN RSA PRIVATE KEY ... END RSA PRIVATE KEY-----"); // when using spring-security application.setDefaultProperties(properties); application.run(args); } }
ℹ️ For testing purposes only
keycan be overwritten inapplication.ymlproperties file.# spring-xsuaa xsuaa: key: -----BEGIN RSA PRIVATE KEY ... END RSA PRIVATE KEY----- # spring-security sap.security.services.xsuaa: key: -----BEGIN RSA PRIVATE KEY ... END RSA PRIVATE KEY-----
❗ DO NOT disclose your key or secret in publicly available places e.g. repository in GitHub.com
💡 Note that if you are only using the token-client library without the java-security or spring-security, you will need to define the env dependency in your pom.xml:
<dependency>
<groupId>com.sap.cloud.security</groupId>
<artifactId>env</artifactId>
</dependency>HttpClientFactory creates an HTTP client that will make the requests to the corresponding Identity service.
When using resourceserver-security-spring-boot-starter Spring Boot Starter client library, a readily configured CloseableHttpClient is accessible via tokenFlowHttpClient Bean that uses the HttpClientFactory internally to set up the HTTP Client for token flows.
The Token Client library includes a default implementation DefaultHttpClientFactory, of the HttpClientFactory interface. It creates a preconfigured Apache HttpClient 4 with the given ClientIdentity for the Identity service instance.
To acquire the HTTP client, use the following code:
CloseableHttpClient client = HttpClientFactory.createClient(ClientIdentity clientIdentity); // you can obtain ClientIdentity by invoking the OAuthServiceConfiguration.getClientIdentity() methodDefaultHttpClientFactory HTTP Clients are configured in the following way:
- connection pool
- maximum of 200 total connections
- 50 connections per route.
- connection and connection request timeouts - 5 seconds
- socket timeout 30 seconds
ℹ️ These values are intended as an initial configuration, and you should monitor your application's performance and provide your own HttpClientFactory implementation, if you observe performance degradation.
For more information, refer to the Troubleshooting section.
By default, the OAuth2TokenService implementations (DefaultOAuth2TokenService and XsuaaOAuth2TokenService) are caching tokens internally.
By default up to 1000 tokens are cached for 10 minutes and the statistics are disabled.
The Cache can be individually configured by configuring TokenCacheConfiguration class. XsuaaTokenFlows need to be then initialized with the DefaultOAuth2TokenService or XsuaaOAuth2TokenService that takes TokenCacheConfiguration as a constructor parameter.
TokenCacheConfiguration tokenCache = TokenCacheConfiguration.getInstance(
Duration cacheDuration,
int cacheSize,
Duration tokenExpirationDelta,
boolean cacheStatisticsEnabled);
OAuth2TokenService tokenService = new DefaultOAuth2TokenService(CloseableHttpClient, tokenCache);
XsuaaTokenFlows tokenFlows = new XsuaaTokenFlows(tokenService, ..., ...);The cache can be disabled by using the TokenCacheConfiguration.cacheDisabled() configuration as follows:
OAuth2TokenService tokenService = new DefaultOAuth2TokenService(CloseableHttpClient, TokenCacheConfiguration.cacheDisabled());
XsuaaTokenFlows tokenFlows = new XsuaaTokenFlows(tokenService, ..., ...);❗ In order to leverage the cache it makes sense to have only one reference to the OAuth2TokenService implementation or to the XsuaaTokenFlows.
tokenFlows.clientCredentialsTokenFlow().disableCache(true).execute();AbstractOAuth2TokenService tokenService = new DefaultOAuth2TokenService(CloseableHttpClient);
XsuaaTokenFlows tokenFlows = new XsuaaTokenFlows(tokenService, ..., ...);
// runtime in case of reoccurring issues
tokenService.clearCache();The XsuaaTokenFlows provides a builder-pattern API that allows applications to easily create and execute each flow, guiding developers to only set properties that are relevant for the respective token flow.
In order to exchange an access token for a different service:
OAuth2TokenResponse tokenResponse = tokenFlows.jwtBearerTokenFlow()
.bearerToken(bearerToken)
.zoneId("MY_ZONE_ID") // optional
.scopes("READ") // optional restriction of granted scopes
.disableCache(true) // optionally disables token cache for the request
.execute();Obtain a client credentials token:
OAuth2TokenResponse clientCredentialsToken = tokenFlows.clientCredentialsTokenFlow()
.zoneId("MY_ZONE_ID") // optional
.disableCache(true) // optionally disables token cache for the request
.execute();In case you have a refresh token and want to obtain an access token:
OAuth2TokenResponse refreshToken = tokenFlows.refreshTokenFlow()
.refreshToken(<refresh_token>)
.subdomain(jwtToken.getSubdomain()) // this is optional
.disableCache(true) // optionally disables token cache for request
.execute();In order to obtain an access token for a user:
OAuth2TokenResponse tokenResponse = tokenFlows.passwordTokenFlow()
.subdomain(jwtToken.getSubdomain())
.username(<username>)
.password(<user password>)
.disableCache(true) // optionally disables token cache for request
.execute();To troubleshoot problems with the token client, you can set the logging level for the
com.sap.cloud.security package to DEBUG.
Have a look at the Logging section for more information on logging for Java EE applications.
If you need more detailed network data in your logs, you can also enable debugging for your HTTP client. For more information see Apache HTTP Client logging documentation.
❗Note that this might leak encoded tokens into your logs. Use with caution!
If you observe performance degradation for token validation or token flows, HttpClient configuration should be adjusted according to your platform's requirements, infrastructure, and anticipated load. You should monitor the performance of your HttpClient under various loads and adjust these parameters accordingly to achieve optimal performance.
You may need to configure the timeouts to specify how long to wait until a connection is established and how long a socket should be kept open (i.e. how long to wait for the (next) data package). As the SSL handshake is time-consuming, it might be recommended to configure an HTTP connection pool to reuse connections by keeping the sockets open. See also Baeldung: HttpClient Connection Management.
To adjust the HttpClient parameters you will need to provide your own implementation of HttpClientFactory interface.
- Create an SPI configuration file with name
com.sap.cloud.security.client.HttpClientFactoryinsrc/main/resources/META-INF/servicesdirectory - Enter the fully qualified name of your
HttpClientFactoryimplementation class, e.g.com.mypackage.CustomHttpClientFactory - The implementation could look like:
public class CustomHttpClientFactory implements HttpClientFactory {
public CloseableHttpClient createClient(ClientIdentity clientIdentity) throws HttpClientException {
// here comes your implementation
}
}CloseableHttpClient implementation always disable redirects
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.
{\"error\":\"unauthorized\",\"error_description\":\"Unable to map issuer, [http://subdomain.localhost:8080/uaa/oauth/token] , to a single registered provider\"}Token exchange is only supported within the same Identity zone/tenant. That means, that you have to call the /oauth/token endpoint of the same subdomain, that was used for the original token. This can be achieved by configuring the JWT Bearer Token Flow the following way:
tokenFlows.jwtBearerTokenFlow().token(jwtToken).subdomain(jwtToken.getSubdomain());
For Spring applications error like
java.lang.IllegalStateException: Failed to load ApplicationContext
Caused by: org.springframework.beans.factory.UnsatisfiedDependencyException: Error creating bean with name 'securityConfiguration': Unsatisfied dependency expressed through field 'xsuaaTokenFlows'
nested exception is java.lang.NoClassDefFoundError: org/apache/http/client/HttpClientindicates that mandatory org.apache.httpcomponents:httpclient dependency is missing in your POM.