Don't allow direct calls to Microservices. Only allow through API Gateway

Question

Maybe this is a strange question (I\'m new with Microservices). But I\'m looking for some info on how proceed with this. Does not need to be Spring specific, but that\'s the

Answer 1

Use a reverse proxy. We use Nginx for the same purpose. Api gateways should always be deployed behind a load balancer for production scenarios to avoid the gateway being a single point of failure. Also, the gateway and services are deployed in a VPC.

Answer 2

Generally, such kind of situation are handled by implementing proper OAuth server wherein only your API gateway will handle the token validation. Any direct call to microservice will not have proper token exchange and hence requests will be aborted.

In case, you have deployed your micro-services on any cloud then you can acheive this by exposing routes to only API gateway. And yes, firewall blocking, IP whitelisting are some of the other ways in restricting the access to your microservices.

Answer 3

Assuming that you have a firewall in place, you could restrict inbound traffic to server to the ports that your Zuul endpoints are exposed on and disallow anyone from accessing the microservices' ports directly.

If you want to avoid going the firewall route, you could force the endpoints to check for a specific HTTP header or something that is set by Zuul prior to forwarding a request, but that would be hacky and easy to circumvent. Based on my past experiences, the "right" way would be to do this via a firewall. Your app should be responsible for dealing with requests. Your firewall should be responsible for deciding who can hit specific endpoints.

Answer 4

The right way to do this with AWS API Gateway would be with the recently launched 'VPC Link' integration, which secures the connection between API Gateway and your backend inside your VPC.

https://aws.amazon.com/about-aws/whats-new/2017/11/amazon-api-gateway-supports-endpoint-integrations-with-private-vpcs/

Answer 5

Hey I finally find a solution to accept request just from the API Gateway by using microservices architecture, for that you can create a filter, and like Zuul act as a proxy, checking the header 'X-Forwarded-Host', if it doesn't match with the gateway service then return an Unauthorised exception.

public class CustomGatewayFilter extends GenericFilterBean {

@Override
public void doFilter(ServletRequest req, ServletResponse resp, FilterChain chain)
        throws IOException, ServletException {

    HttpServletRequest request = (HttpServletRequest) req;
    HttpServletResponse response = (HttpServletResponse) resp;

    String proxyForwardedHostHeader = request.getHeader("X-Forwarded-Host");

    if (proxyForwardedHostHeader == null || !proxyForwardedHostHeader.equals(GatewayConstant.getGatewayURL())) {
        UnauthorisedException unauthorisedException = new UnauthorisedException("Unauthorized Access",
                "Unauthorized Access, you should pass through the API gateway");
        byte[] responseToSend = restResponseBytes(unauthorisedException.getErrorResponse());
        ((HttpServletResponse) response).setHeader("Content-Type", "application/json");
        ((HttpServletResponse) response).setStatus(401);
        response.getOutputStream().write(responseToSend);
        return;
    }
    chain.doFilter(request, response);
}

private byte[] restResponseBytes(ErrorResponse errorResponse) throws IOException {
    String serialized = new ObjectMapper().writeValueAsString(errorResponse);
    return serialized.getBytes();
}

}

do not forget to add your custom filter in SpringSecurity Configuration

.and().addFilterBefore(new CustomGatewayFilter(), ConcurrentSessionFilter.class);