OAuth2 Authenticating Proxy

Simple proxy application to add an OAuth2 access token to any request passing through

This application will take any incoming HTTP request and attach a valid OAuth2 token in a standard Authorization header as Bearer {{TOKEN}}. This comes in handy if you have a trusted application making requests that should be authorized automatically.
To do so, the proxy automatically fetches an access token from the authorization server you configured. It will try to refresh it automatically and reuse an existing token, if possible.

Attention: Using this proxy can be dangerous. Make sure you strictly limit access to it!

Installation

We strongly recommend using the proxy in a Docker stack, e.g. docker-compose:

version: 3.7
services:
  proxy:
    image: ghcr.io/matchory/oauth2-authenticating-proxy:latest
    expose:
      - 8080
    volumes:
      - "./proxy.yaml:/proxy/config.yaml:ro"

Configuration

The proxy supports passing configuration from environment variables or from a YAML configuration file. Environment variables will always take precedence over values found in the configuration file.
The following options are supported:

Option	Environment variable	Default	Description
listen_port	LISTEN_PORT	8080	Network port to listen on.
skip_tls_verify	SKIP_TLS_VERIFY	false	Whether to skip TLS certificate validation.
client_id	CLIENT_ID	-	OAuth2 client ID to authenticate with.
client_secret	CLIENT_SECRET	-	OAuth2 client secret to authenticate with.
token_endpoint	TOKEN_ENDPOINT	-	Fully qualified URL of your OAuth2 token endpoint.
scopes	SCOPES	-	List of scopes to request for the token.
upstream_scheme	UPSTREAM_SCHEME	https	URL scheme to use for upstream connections.
upstream_host	UPSTREAM_HOST	-	Host to forward requests to. Optional.
allowed_hosts	ALLOWED_HOSTS	-	List of allowed hosts to forward to. Optional.

Usage

After spinning up the image with correct configuration, you should be able to send HTTP requests without an Authorization header to the proxy and see requests with the header, and a valid token arrive at your back service.

Upstream hosts

When proxying a request, it needs to be sent to the proxy host instead of the actual, intended host. To make this possible, you'll need some way to tell the proxy server where to send the modified request to. The OAuth2 proxy provides you with three different ways to resolve the target host:

1. Set the upstream_host configuration directive
   If all you ever need to do is send requests to a single upstream, you can set the hostname (without a protocol) in your configuration file (or using the UPSTREAM_HOST environment variable), and all requests will be forwarded to that host.
2. Set the Forward request header
   To dynamically set the forward host, you can set the Forward header on your requests. This will even take precedence over the configured upstream host from variant 1. To make it harder to shoot yourself in the foot, you can (and should!) configure the allowed_hosts setting with all hosts you explicitly want to talk to.
3. Set the Host request header independently
   Depending on the type of library you use, you have the possibility to set the Host header independently of the request URI: The proxy uses the value of the host header as the fallback value, if none of the other two methods resolved a hostname.