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 framework I'm using at the moment.

Example: Lets say we have two Microservices

a) http://myurlfortesting.com:8085/api/rest/serviceone

b) http://myurlfortesting.com:8090/api/rest/servicetwo

and we have setup Spring Zuul (acting as the API Gateway) with the following rules that forward the incoming calls:

/rest/one -> http://myurlfortesting.com:8085/api/rest/serviceone

/rest/two -> http://myurlfortesting.com:8090/api/rest/servicetwo

The question... Is there a way to stop users from directly accessing the services mentioned in A and B (only allow the ones that come through the API Gateway)?

Can this be done with Springs Zuul (Acting as a API Gateway) by setting up some extra filters or do we set it up in Microservices endpoints?

Would even like to know if there is a way to not even processing the direct calls on the Microservices endpoints that don't come via the API Gateway.

Maybe this is solved with server specific rules and has nothing to do with Spring?

Many thanks,

/D

Answer 1

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 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.