Traefik Forward Auth

A minimal forward authentication service that provides Google oauth based login and authentication for the traefik reverse proxy/load balancer.

Why?

• Seamlessly overlays any http service with a single endpoint (see: url-path in Configuration)
• Supports multiple domains/subdomains by dynamically generating redirect_uri's
• Allows authentication to be selectively applied/bypassed based on request parameters (see rules in Configuration))
• Supports use of centralised authentication host/redirect_uri (see auth-host in Configuration))
• Allows authentication to persist across multiple domains (see Cookie Domains)
• Supports extended authentication beyond Google token lifetime (see: lifetime in Configuration)

Contents

• Releases
• Usage
  • Simple
  • Advanced
  • OAuth Configuration
• Configuration
  • Overview
  • Option Details
• Concepts
  • Forwarded Headers
  • User Restriction
  • Operation Modes
    • Overlay Mode
    • Auth Host Mode
• Copyright
• License

Releases

We recommend using the 2 tag on docker hub.

You can also use the latest incremental releases found on docker hub and github.

Upgrade Guide

v2 was released in June 2019, whilst this is fully backwards compatible, a number of configuration options were modified, please see the upgrade guide to prevent warnings on startup and ensure you are using the current configuration.

Usage

Simple:

See below for instructions on how to setup your OAuth Configuration.

docker-compose.yml:

version: '3'

services:
  traefik:
    image: traefik:1.7
    ports:
      - "8085:80"
    volumes:
      - ./traefik.toml:/traefik.toml
      - /var/run/docker.sock:/var/run/docker.sock

  traefik-forward-auth:
    image: thomseddon/traefik-forward-auth:2
    environment:
      - CLIENT_ID=your-client-id
      - CLIENT_SECRET=your-client-secret
      - SECRET=something-random
      - INSECURE_COOKIE=true # Example assumes no https, do not use in production

  whoami:
    image: emilevauge/whoami:latest
    labels:
      - "traefik.frontend.rule=Host:whoami.mycompany.com"

traefik.toml:

[entryPoints]
    [entryPoints.http]
    address = ":80"

    [entryPoints.http.auth.forward]
    address = "http://traefik-forward-auth:4181"
    authResponseHeaders = ["X-Forwarded-User"]

[docker]
endpoint = "unix:///var/run/docker.sock"
network = "traefik"

Advanced:

Please see the examples directory for a more complete docker-compose.yml and full traefik.toml.

Also in the examples directory is docker-compose-auth-host.yml which shows how to configure a central auth host, along with some other options.

OAuth Configuration

Head to https://console.developers.google.com and make sure you've switched to the correct email account.

Create a new project then search for and select "Credentials" in the search bar. Fill out the "OAuth Consent Screen" tab.

Click "Create Credentials" > "OAuth client ID". Select "Web Application", fill in the name of your app, skip "Authorized JavaScript origins" and fill "Authorized redirect URIs" with all the domains you will allow authentication from, appended with the url-path (e.g. https://app.test.com/_oauth)

Configuration

Overview

The following configuration options are supported:

Usage:
  traefik-forward-auth [OPTIONS]

Application Options:
  --log-level=[trace|debug|info|warn|error|fatal|panic] Log level (default: warn) [$LOG_LEVEL]
  --log-format=[text|json|pretty]                       Log format (default: text) [$LOG_FORMAT]
  --auth-host=                                          Single host to use when returning from 3rd party auth [$AUTH_HOST]
  --config=                                             Path to config file [$CONFIG]
  --cookie-domain=                                      Domain to set auth cookie on, can be set multiple times [$COOKIE_DOMAIN]
  --insecure-cookie                                     Use insecure cookies [$INSECURE_COOKIE]
  --cookie-name=                                        Cookie Name (default: _forward_auth) [$COOKIE_NAME]
  --csrf-cookie-name=                                   CSRF Cookie Name (default: _forward_auth_csrf) [$CSRF_COOKIE_NAME]
  --default-action=[auth|allow]                         Default action (default: auth) [$DEFAULT_ACTION]
  --domain=                                             Only allow given email domains, can be set multiple times [$DOMAIN]
  --lifetime=                                           Lifetime in seconds (default: 43200) [$LIFETIME]
  --url-path=                                           Callback URL Path (default: /_oauth) [$URL_PATH]
  --secret=                                             Secret used for signing (required) [$SECRET]
  --whitelist=                                          Only allow given email addresses, can be set multiple times [$WHITELIST]
  --rules.<name>.<param>=                               Rule definitions, param can be: "action" or "rule"

Google Provider:
  --providers.google.client-id=                         Client ID [$PROVIDERS_GOOGLE_CLIENT_ID]
  --providers.google.client-secret=                     Client Secret [$PROVIDERS_GOOGLE_CLIENT_SECRET]
  --providers.google.prompt=                            Space separated list of OpenID prompt options [$PROVIDERS_GOOGLE_PROMPT]

Help Options:
  -h, --help                                            Show this help message

All options can be supplied in any of the following ways, in the following precedence (first is highest precedence):

1. Command Arguments/Flags - As shown above
2. Environment Variables - As shown in square brackets above
3. File
   1. Use INI format (e.g. url-path = _oauthpath)
   2. Specify the file location via the --config flag or $CONFIG environment variable
   3. Can be specified multiple times, each file will be read in the order they are passed

Option Details

• auth-host

  When set, when a user returns from authentication with a 3rd party provider they will always be forwarded to this host. By using one central host, this means you only need to add this auth-host as a valid redirect uri to your 3rd party provider.

  The host should be specified without protocol or path, for example:

  --auth-host="auth.example.com"
  

  For more details, please also read the Auth Host Mode, operation mode in the concepts section.

  Please Note - this should be considered advanced usage, if you are having problems please try disabling this option and then re-read the Auth Host Mode section.

• config

  Used to specify the path to a configuration file, can be set multiple times, each file will be read in the order they are passed. Options should be set in an INI format, for example:

  url-path = _oauthpath
  

• cookie-domain

  When set, if a user successfully completes authentication, then if the host of the original request requiring authentication is a subdomain of a given cookie domain, then the authentication cookie will be set for the higher level cookie domain. This means that a cookie can allow access to multiple subdomains without re-authentication. Can be specificed multiple times.

  For example:

  --cookie-domain="example.com"  --cookie-domain="test.org"
  

  For example, if the cookie domain test.com has been set, and a request comes in on app1.test.com, following authentication the auth cookie will be set for the whole test.com domain. As such, if another request is forwarded for authentication from app2.test.com, the original cookie will be sent and so the request will be allowed without further authentication.

  Beware however, if using cookie domains whilst running multiple instances of traefik/traefik-forward-auth for the same domain, the cookies will clash. You can fix this by using a different cookie-name in each host/cluster or by using the same cookie-secret in both instances.

• insecure-cookie

  If you are not using HTTPS between the client and traefik, you will need to pass the insecure-cookie option which will mean the Secure attribute on the cookie will not be set.

• cookie-name

  Set the name of the cookie set following successful authentication.

  Default: _forward_auth

• csrf-cookie-name

  Set the name of the temporary CSRF cookie set during authentication.

  Default: _forward_auth_csrf

• default-action

  Specifies the behavior when a request does not match any rules. Valid options are auth or allow.

  Default: auth (i.e. all requests require authentication)

• domain

  When set, only users matching a given domain will be permitted to access.

  For example, setting --domain=example.com --domain=test.org would mean that only users from example.com or test.org will be permitted. So thom@example.com would be allowed but thom@another.com would not.

  For more details, please also read User Restriction in the concepts section.

• lifetime

  How long a successful authentication session should last, in seconds.

  Default: 43200 (12 hours)

• url-path

  Customise the path that this service uses to handle the callback following authentication.

  Default: /_oauth

  Please note that when using the default Overlay Mode requests to this exact path will be intercepted by this service and not forwarded to your application. Use this option (or Auth Host Mode) if the default /_oauth path will collide with an existing route in your application.

• secret

  Used to sign cookies authentication, should be a random (e.g. openssl rand -hex 16)

• whitelist

  When set, only specified users will be permitted.

  For example, setting --whitelist=thom@example.com --whitelist=alice@example.com would mean that only those two exact users will be permitted. So thom@example.com would be allowed but john@example.com would not.

  For more details, please also read User Restriction in the concepts section.

• rules

  Specify selective authentication rules. Rules are specified in the following format: rule.<name>.<param>=<value>

  • <name> can be any string and is only used to group rules together
  • <param> can be:
    • action - same usage as default-action, supported values:
      • auth (default)
      • allow
    • rule - a rule to match a request, this uses traefik's v2 rule parser for which you can find the documentation here: https://docs.traefik.io/v2.0/routing/routers/#rule, supported values are summarised here:
      • Headers(`key`, `value`)
      • HeadersRegexp(`key`, `regexp`)
      • Host(`example.com`, ...)
      • HostRegexp(`example.com`, `{subdomain:[a-z]+}.example.com`, ...)
      • Method(methods, ...)
      • Path(`path`, `/articles/{category}/{id:[0-9]+}`, ...)
      • PathPrefix(`/products/`, `/articles/{category}/{id:[0-9]+}`)
      • Query(`foo=bar`, `bar=baz`)
    • whitelist - optional, same usage as whitelist.
    • domains - optional, same usage as domain.

  For example:

  rule.1.action = allow
  rule.1.rule = PathPrefix(`/api/public`) && Headers(`Content-Type`, `application/json`)
  
  rule.two.action = allow
  rule.two.rule = Path(`/public`)
  

  In the above example, the first rule would allow requests that begin with /api/public and contain the Content-Type header with a value of application/json. It would also allow requests that had the exact path /public.

Concepts

User Restriction

You can restrict who can login with the following parameters:

• domain - Use this to limit logins to a specific domain, e.g. test.com only
• whitelist - Use this to only allow specific users to login e.g. thom@test.com only

Note, if you pass whitelist then only this is checked and domain is effectively ignored. If you set domains or whitelist on a rules, the global configuration is ignored.

Forwarded Headers

The authenticated user is set in the X-Forwarded-User header, to pass this on add this to the authResponseHeaders config option in traefik, as shown here.

Operation Modes

Overlay Mode

Overlay is the default operation mode, in this mode the authorisation endpoint is overlayed onto any domain. By default the /_oauth path is used, this can be customised using the url-path option.

The user flow will be:

1. Request to www.myapp.com/home
2. User redirected to Google login
3. After Google login, user is redirected to www.myapp.com/_oauth
4. Token, user and CSRF cookie is validated (this request in intercepted and is never passed to your application)
5. User is redirected to www.myapp.com/home
6. Request is allowed

As the hostname in the redirect_uri is dynamically generated based on the original request, every hostname must be permitted in the Google OAuth console (e.g. www.myappp.com would need to be added in the above example)

Auth Host Mode

This is an optional mode of operation that is useful when dealing with a large number of subdomains, it is activated by using the auth-host config option (see this example docker-compose.yml).

For example, if you have a few applications: app1.test.com, app2.test.com, appN.test.com, adding every domain to Google's console can become laborious. To utilise an auth host, permit domain level cookies by setting the cookie domain to test.com then set the auth-host to: auth.test.com.

The user flow will then be:

1. Request to app10.test.com/home/page
2. User redirected to Google login
3. After Google login, user is redirected to auth.test.com/_oauth
4. Token, user and CSRF cookie is validated, auth cookie is set to test.com
5. User is redirected to app10.test.com/home/page
6. Request is allowed

With this setup, only auth.test.com must be permitted in the Google console.

Two criteria must be met for an auth-host to be used:

1. Request matches given cookie-domain
2. auth-host is also subdomain of same cookie-domain

Please note: For Auth Host mode to work, you must ensure that requests to your auth-host are routed to the traefik-forward-auth container, as demonstrated with the service labels in the docker-compose-auth.yml example.

Copyright

2018 Thom Seddon

License

MIT