Gorouter should be able to redirect HTTP to HTTPS traffic

Is this a security vulnerability?

no.

Issue

While HTTP is dying off, many browsers still don't use HTTPS out-of-the-box. Unless your browser has HSTS set for the domain, most browsers will initially go for HTTP when the user just enters the domain's name without a https:// prefix.

Gorouter now supports both http and https traffic, there is no means to tell a user arriving at port 80 to go get upgraded to TLS at port 443.
The current option if you don't want port 80 to be used for traffic, is to close it completely. Which is inconvenient as users will first see "connection refused" errors and then have to manually type the "https://" prefix in their address bar.

It would be much nicer to have an option enable_redirect_to_ssl which works in two ways:

1. If a request arrived at port 80 it gets redirected to port 443
2. If a request arrived at port 443 but x-forwarded-proto is set to http, this means gorouter is behind a proxy who forwarded http traffic to gorouter's https port, so the connection is not fully secure. The user will also see a redirect to https.

Affected Versions

All

Context

In our deployments we use HAProxy BOSH-release as a front-end proxy before Gorouter. HAProxy also supports redirects but it's hard to know there which domains should be redirected. The reason why redirects should not be "blind" is potential security threats of cache poisoning and others if such systems are used.

Gorouter on the other hand, knows all routes because it receives them from NATS, so it would be the better candidate to serve "verified" redirects as it knows if a given host header exists on the platform or not.

Steps to Reproduce

1. curl -H 'host: cat-videos.cf-app.com' http://cf-app.com

Expected result

HTTP/1.1 301 Moved Permanently
content-length: 0
location: https://cat-videos.cf-app.com/

Current result

Either

Connection refused

or

<cat videos served from port 80>

Possible Fix

• Introduce a new spec property enable_redirect_to_ssl: <bool> (default false)

The first property will be read by a new middleware in gorouter that comes after lookup.go and will return a 301 to the client with the domain presented in the host header. The middleware will send the redirect if either

• the request came in via http, or
• the request contains a x-forwarded-proto: http header

Start with router/router.go to understand the HTTP and HTTPS listeners, then inspect the middleware boundary after lookup.go described in the issue. Trace how route specifications are received from NATS and how the host header is validated. Use the provided curl command to verify that the configured behavior returns a 301 with the expected HTTPS location.