Spring Security SAML 2.0 LogoutRequest should contain session indexes

Expected Behavior

Currently "LogoutRequest" is missing "SessionIndex" attributes, some IdPs might have a problem with accepting such requests. It would be great if we could have it implemented as it was in the currently deprecated SAML Library. IMHO, OpenSamlLogoutRequestResolver should have implemented similar logic to https://github.com/spring-projects/spring-security-saml/blob/main/core/src/main/java/org/springframework/security/saml/websso/SingleLogoutProfileImpl.java#L110

Current Behavior

Saml2LogoutRequestResolver constructs "LogoutRequest" with usage of OpenSamlLogoutRequestResolver which does not add SessionIndex to "LogoutRequest" , so that IdP returns "urn:oasis:names:tc:SAML:2.0:status:Requester" response code, and SLO is not conducted in proper way

Version

5.6

Comment From: jzheaux

@Olbix, thanks for the suggestion.

I think session indexes will need to be remembered in the Saml2AuthenticatedPrincipal at login time so that they can be retrieved when formulating a LogoutRequest.

Are you able to provide a PR that adds this feature?

Comment From: boukewoudstra

Just sharing a workaround for the time being using a custom Saml2LogoutRequestResolver:

    // Customize the saml2 logout request resolver in order to add the sessionIndex which is needed for single logout
    @Bean
    public Saml2LogoutRequestResolver logoutRequestResolver(RelyingPartyRegistrationRepository relyingPartyRepository) {
        OpenSaml4LogoutRequestResolver logoutRequestResolver = new OpenSaml4LogoutRequestResolver(new DefaultRelyingPartyRegistrationResolver(relyingPartyRepository));
        logoutRequestResolver.setParametersConsumer((parameters) -> {
            Saml2AuthenticatedPrincipal principal = (Saml2AuthenticatedPrincipal) parameters.getAuthentication().getPrincipal();
            LogoutRequest logoutRequest = parameters.getLogoutRequest();
            SessionIndex sessionIndex = new MySessionIndex("urn:oasis:names:tc:SAML:2.0:protocol", "SessionIndex", "saml2p");
            sessionIndex.setValue(principal.getFirstAttribute("sessionIndex"));
            logoutRequest.getSessionIndexes().add(sessionIndex);
        });
        return logoutRequestResolver;
    }

In combination with a custom SessionIndex since it it a protected class:

public class MySessionIndex extends XSStringImpl implements SessionIndex {

    public MySessionIndex(String namespaceURI, String elementLocalName, String namespacePrefix) {
        super(namespaceURI, elementLocalName, namespacePrefix);
    }
}

and a custom authenticationProvider:

    @Bean
    public OpenSaml4AuthenticationProvider authenticationProvider(){
        OpenSaml4AuthenticationProvider authenticationProvider = new OpenSaml4AuthenticationProvider();
        authenticationProvider.setResponseAuthenticationConverter(responseToken -> {
            Saml2Authentication saml2Authentication = OpenSaml4AuthenticationProvider
                    .createDefaultResponseAuthenticationConverter()
                    .convert(responseToken);

            Assertion assertion = CollectionUtils.firstElement(responseToken.getResponse().getAssertions());
            AuthnStatement statement = CollectionUtils.firstElement(assertion.getAuthnStatements());
            String sessionIndex = statement.getSessionIndex();
            var customAuthorities = AuthorityUtils.createAuthorityList("ROLE_USER", "ROLE_TEST");

            DefaultSaml2AuthenticatedPrincipal principal = (DefaultSaml2AuthenticatedPrincipal) saml2Authentication.getPrincipal();
            principal.getAttributes().put("sessionIndex", List.of(sessionIndex));
            return new Saml2Authentication(principal, saml2Authentication.getSaml2Response(), customAuthorities);
        });
        return authenticationProvider;
    }

and wiring it all together:

      http
            .saml2Login(saml2 -> {
                saml2.authenticationManager(new ProviderManager(this.getApplicationContext().getBean(OpenSaml4AuthenticationProvider.class)));
            })
            .saml2Logout(saml2 -> {
                saml2.logoutRequest(logout -> {
                   logout.logoutRequestResolver(this.getApplicationContext().getBean(Saml2LogoutRequestResolver.class));
                });
            })