auth-server

A very simple standalone authentication server Express app.

It can be used for protecting web sites with NGINX subrequest authentication.

• Use auth_request /auth in NGINX conf.
• When user requests protected area, NGINX makes an internal request to /auth. If 201 is returned, protected contents are served. Anything else, NGINX responds with 401.
• /auth is reverse proxied to Express app auth-server which handles authentication. Cookies are passed on as well, so the auth server can check for a JWT.
• Auth server sets httpOnly cookie containing a JWT.
• JWT updated with new expiry each time a user visits protected area.
• Default rate limit of 15 /login requests every 15 minutes.

How to use

Refer to this tutorial on my blog:

https://gock.net/blog/2020/nginx-subrequest-authentication-server/

Configure .env

• AUTH_PORT - Listening port of application (default: 3000)
• AUTH_PASSWORD - Authentication password
• AUTH_TOKEN_SECRET - JWT secret
• AUTH_COOKIE_SECURE - Secure attribute on authentication cookie sent from server. Set to true to enable, or if AUTH_COOKIE_SECURE is missing, defaults to true.

Refer to dotenv documentation for formatting.

You can define a custom auth routine in auth.js. See auth.example.js for an example. If you don't configure a auth.js it will use default simple AUTH_PASSWORD password based authentication.

Development

Install nodemon globally.

Install dependencies

yarn

Start dev server

yarn watch

Be aware that the authentication cookie used by default uses the secure attribute thus the demo will only work when connecting via

• HTTPS to a non-local IP address, or
• HTTPS to a hostname other than "localhost", or
• HTTP/HTTPS to localhost.

Production

Start with npm start, or use one of the strategies below

PM2

Install with pm2

pm2 start ./app.js --name auth

Docker

sudo docker build -t auth-server .
sudo docker run -it -p 3000:3000 -e AUTH_PASSWORD=test -e AUTH_TOKEN_SECRET=verysecret auth-server

Example NGINX conf

Use the following in our NGINX server conf.

# optional:
# internal redirect to /login if there is a auth failure, delete or comment this out if you don't want this behaviour and just show a generic 401 error
error_page 401 /login;

location / {
    auth_request /auth;

    # pass Set-Cookie headers from the subrequest response back to requestor
    auth_request_set $auth_cookie $upstream_http_set_cookie;
    add_header Set-Cookie $auth_cookie;

    auth_request_set $auth_status $upstream_status;

    try_files $uri $uri/ /index.html;
}

location = /auth {
    # internaly only, /auth can not be accessed from outside
    internal;

    # internal proxy to auth-server running on port 3000, responses expected from proxy:
    #   2xx response = access allowed via auth_request
    #   401 or 403 response = access denied via auth_request
    #   anything else = error
    proxy_pass http://localhost:3000;

    # don't pass request body to proxied server, we only need the headers which are passed on by default
    proxy_pass_request_body off;

    # there is no content length since we stripped the request body
    proxy_set_header Content-Length "";

    # let proxy server know more details of request
    proxy_set_header X-Original-URI $request_uri;
    proxy_set_header X-Original-Remote-Addr $remote_addr;
    proxy_set_header X-Original-Host $host;
}

# these are handled by the proxy as part of the auth routines
location ~ ^/(login|logged-in|logout)$ {
    proxy_pass http://localhost:3000;
    proxy_set_header X-Original-URI $request_uri;
    proxy_set_header X-Original-Remote-Addr $remote_addr;
    proxy_set_header X-Original-Host $host;
}

# this CSS is used by the three requests above and is served by the proxy
location = /css/skeleton.css {
    proxy_pass http://localhost:3000;
}

# optional location block
# if you have other location blocks, be sure to add auth_request there too otherwise these requests won't get protected, for example
location ~* \.(js|css|png|jpg|jpeg|gif|ico)$ {
    expires 90d;
    log_not_found off;
    auth_request /auth;
}

References

• Skeleton CSS
• NGINX sub request authentication
• Using JWTs with NodeJS tutorial
• jsonwebtoken node module