Zuul reverse proxy with Keycloak server

Recently I've had the same problem. I've solved it by:

1. Add to application.properties in Zuul

   zuul.sensitive-headers=Cookie,Set-Cookie

2. Introduce KeycloakFilterRoute in Zuul

   class KeycloakFilterRoute extends ZuulFilter {
   
   private static final String AUTHORIZATION_HEADER = "authorization";
   
   @Override
   public String filterType() {
       return "route";
   }
   
   @Override
   public int filterOrder() {
       return 0;
   }
   
   @Override
   public boolean shouldFilter() {
       return true;
   }
   
   @Override
   public Object run() {
       RequestContext ctx = RequestContext.getCurrentContext();
       if (ctx.getRequest().getHeader(AUTHORIZATION_HEADER) == null) {
           addKeycloakTokenToHeader(ctx);
       }
       return null;
   }
   
   private void addKeycloakTokenToHeader(RequestContext ctx) {
       RefreshableKeycloakSecurityContext securityContext = getRefreshableKeycloakSecurityContext(ctx);
       if (securityContext != null) {
           ctx.addZuulRequestHeader(AUTHORIZATION_HEADER, buildBearerToken(securityContext));
       }
   }
   
   private RefreshableKeycloakSecurityContext getRefreshableKeycloakSecurityContext(RequestContext ctx) {
       if (ctx.getRequest().getUserPrincipal() instanceof KeycloakAuthenticationToken) {
           KeycloakAuthenticationToken token = (KeycloakAuthenticationToken) ctx.getRequest().getUserPrincipal();
           return (RefreshableKeycloakSecurityContext) token.getCredentials();
       }
       return null;
   }
   
   private String buildBearerToken(RefreshableKeycloakSecurityContext securityContext) {
       return "Bearer " + securityContext.getTokenString();
   }
   

   }