[keycloak-user] Authentication throw a proxy on Undertow

Hi everybody, this is the big picture: a. frontend application with Undertow b. backend application with Undertow and Resteasy for REST API Both are using Keycloak as SSO. I'm trying to configure a proxy from A to B in order to expose backend API without CORS problems to the frontend. I asked support also to Undertow guys but the issue seems around the integration of Keycloack in Undertow. My proxy is implemented like: final ProxyClient proxyClient = new SimpleProxyClientProvider(new URI("http://localhost:8181")); final ProxyHandler proxyHandler = new ProxyHandler(proxyClient, servletHandler); proxyHandler.addRequestHeader(new HttpString("Authorization"), new ExchangeAttribute() { @Override public String readAttribute(HttpServerExchange exchange) { exchange. RefreshableKeycloakSecurityContext context = (RefreshableKeycloakSecurityContext) exchange.getSecurityContext(); return "Bearer " + context.getTokenString(); } @Override public void writeAttribute(HttpServerExchange exchange, String newValue) throws ReadOnlyAttributeException { // TODO Auto-generated method stub } }); The problem is that the exchange.getSecurityContext() is always null. Any ideas? Thanks -- Davide