Description

Spring Cloud Config Server may not use Vault token sent by clients using a X-CONFIG-TOKEN header when making requests to Vault.

Your application may be affected by this if the following are true:

1. You have Spring Vault on the classpath of your Spring Cloud Config Server and
2. You are using the X-CONFIG-TOKEN header to send a Vault token to the Spring Cloud Config Server for the Config Server to use when making requests to Vault and
3. You are using the default Spring Vault SessionManager implementation LifecycleAwareSessionManager or a SessionManager implementation that persists the Vault token such as SimpleSessionManager.

In this case the SessionManager persists the first token it retrieves and will continue to use that token even if client requests to the Spring Cloud Config Server include a X-CONFIG-TOKEN header with a different value.

Affected Spring Products and Versions

Spring Cloud Config:

• 2.2.1.RELEASE - 4.2.1

Mitigation

Users of affected versions should upgrade to the corresponding fixed version.

NOTE: Spring Cloud Config 3.0.x and 2.2.x are no longer under open source or commercial support. Users of these versions are encouraged to upgrade to a supported version.

No other mitigation steps are necessary.

If you cannot upgrade, then you can either:

1. Remove Spring Vault from the classpath if it is not needed or
2. Implement your own SessionManager that does not persist the Vault token and provide a bean using that implementation in a @Configuration class. For example:

public class StatelessSessionManager implements SessionManager {

	private final ClientAuthentication clientAuthentication;

	private final ReentrantLock lock = new ReentrantLock();

	public StatelessSessionManager(ClientAuthentication clientAuthentication) {
		Assert.notNull(clientAuthentication, "ClientAuthentication must not be null");
		this.clientAuthentication = clientAuthentication;
	}

	public VaultToken getSessionToken() {
		this.lock.lock();
		try {
			return this.clientAuthentication.login();
		}
		finally {
			this.lock.unlock();
		}
	}

}

@Configuration
public class MySessionManagerConfiguration extends SpringVaultClientConfiguration {

	private final VaultEnvironmentProperties vaultProperties;

	public MySessionManagerConfiguration(VaultEnvironmentProperties vaultProperties, ConfigTokenProvider configTokenProvider, List authProviders) {
		super(vaultProperties, configTokenProvider, authProviders);
		this.vaultProperties = vaultProperties;
	}

	@Bean
	@Primary
	public SessionManager sessionManager() {
		if (vaultProperties.getAuthentication() == null && !StringUtils.hasText(vaultProperties.getToken())) {
			return new StatelessSessionManager(clientAuthentication());
		}
		return super.sessionManager();
	}
}

Credit

This vulnerability was discovered and responsibly reported by Max Brauer and Mohammad Shamsi.

References

• https://nvd.nist.gov/vuln-metrics/cvss/v3-calculator?vector=AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:N&version=3.1