Traefik Forward Auth

A minimal forward authentication service that provides OAuth/SSO login and authentication for the traefik reverse proxy/load balancer.

Fork notes

This is yet another fork of thomseddon/traefik-forward-auth. I have merged several pull requests that have not (yet?) been merged upstream:

• thomseddon#77
• thomseddon#159
• thomseddon#281
• thomseddon#295
• thomseddon#327

I have also updated all the dependencies, and switched to building with Go 1.19. The Dockerfile has been switched from Alpine to using the official Go container for building the binary and a distroless image for runtime.

I wrote a blog post about how I use this. Note that I only use the Generic OAuth provider. I haven't tried using the other providers, but all the tests still pass.

This version now builds against Traefik 2.9, so you should be able to use all of the latest matchers, but ClientIP does not appear to be working as you might expect. It seems to be a better bet to match against the X-Forwarded-For header.

Why?

• Seamlessly overlays any http service with a single endpoint (see: url-path in Configuration)
• Supports multiple providers including Google and OpenID Connect (supported by Azure, Github, Salesforce etc.)
• 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
  • Provider Setup
• Configuration
  • Overview
  • Option Details
• Concepts
  • Forwarded Headers
  • User Restriction
  • Applying Authentication
    • Global Authentication
    • Selective Ingress Authentication in Kubernetes
    • Selective Container Authentication in Swarm
    • Rules Based Authentication
  • Operation Modes
    • Overlay Mode
    • Auth Host Mode
  • Logging Out
• Copyright
• License

Releases

Releases of this fork are published to the GitHub Container Registry.

I currently only publish a latest tag.

Upgrade Guide

This fork should be backwards-compatible with upstream releases.

Usage

Simple:

See below for instructions on how to setup your Provider Setup.

docker-compose.yml:

services:
  traefik:
    image: traefik:v3.0
    command: --providers.docker
    ports:
      - "8085:80"
    volumes:
      - /var/run/docker.sock:/var/run/docker.sock

  traefik-forward-auth:
    image: ghcr.io/jordemort/traefik-forward-auth:latest
    environment:
      - PROVIDERS_GOOGLE_CLIENT_ID=your-client-id
      - PROVIDERS_GOOGLE_CLIENT_SECRET=your-client-secret
      - SECRET=something-random
      - INSECURE_COOKIE=true # Example assumes no https, do not use in production
    labels:
      - "traefik.http.middlewares.traefik-forward-auth.forwardauth.address=http://traefik-forward-auth:4181"
      - "traefik.http.middlewares.traefik-forward-auth.forwardauth.authResponseHeaders=X-Forwarded-User"
      - "traefik.http.services.traefik-forward-auth.loadbalancer.server.port=4181"

  whoami:
    image: containous/whoami
    labels:
      - "traefik.http.routers.whoami.rule=Host(`whoami.mycompany.com`)"
      - "traefik.http.routers.whoami.middlewares=traefik-forward-auth"

Advanced:

Please see the examples directory for a more complete docker-compose.yml or kubernetes/simple-separate-pod.

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

Provider Setup

Below are some general notes on provider setup, specific instructions and examples for a number of providers can be found on the Provider Setup wiki page.

Google

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)

You must set the providers.google.client-id and providers.google.client-secret config options.

OpenID Connect

Any provider that supports OpenID Connect 1.0 can be configured via the OIDC config options below.

You must set the providers.oidc.issuer-url, providers.oidc.client-id and providers.oidc.client-secret config options.

Please see the Provider Setup wiki page for examples.

Generic OAuth2

For providers that don't support OpenID Connect, we also have the Generic OAuth2 provider where you can statically configure the OAuth2 and "user" endpoints.

You must set:

• providers.generic-oauth.auth-url - URL the client should be sent to authenticate the authenticate
• providers.generic-oauth.token-url - URL the service should call to exchange an auth code for an access token
• providers.generic-oauth.user-url - URL used to retrieve user info (service makes a GET request)
• providers.generic-oauth.client-id - Client ID
• providers.generic-oauth.client-secret - Client Secret

You can also set:

• providers.generic-oauth.scope- Any scopes that should be included in the request (default: profile, email)
• providers.generic-oauth.token-style - How token is presented when querying the User URL. Can be header or query, defaults to header. With header the token is provided in an Authorization header, with query the token is provided in the access_token query string value.

Please see the Provider Setup wiki page for examples.

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|soft-auth|allow]               Default action (default: auth) [$DEFAULT_ACTION]
      --default-provider=[google|oidc|generic-oauth]        Default provider (default: google) [$DEFAULT_PROVIDER]
      --domain=                                             Only allow given email domains, comma separated, can be set multiple times [$DOMAIN]
      --header-names=                                       User header names, comma separated (default: X-Forwarded-User) [$HEADER_NAMES]
      --lifetime=                                           Lifetime in seconds (default: 43200) [$LIFETIME]
      --match-whitelist-or-domain                           Allow users that match *either* whitelist or domain (enabled by default in v3) [$MATCH_WHITELIST_OR_DOMAIN]
      --url-path=                                           Callback URL Path (default: /_oauth) [$URL_PATH]
      --secret=                                             Secret used for signing (required) [$SECRET]
      --soft-auth-user=                                     If set, username used in header if unauthorized with soft-auth action [$SOFT_AUTH_USER]
      --user-id-path=                                       Dot notation path of a UserID for use with whitelist and X-Forwarded-User (default: email) [$USER_ID_PATH]
      --whitelist=                                          Only allow given UserID, comma separated, can be set multiple times [$WHITELIST]
      --port=                                               Port to listen on (default: 4181) [$PORT]
      --probe-token=                                        Static probe token which is always passed [$PROBE_TOKEN]
      --probe-token-user=                                   User authenticated with static probe token (default: probe) [$PROBE_TOKEN_USER]
      --rule.<name>.<param>=                                Rule definitions, param can be: "action", "rule" or "provider"
      --trusted-ip-address=                                 List of trusted IP addresses or IP networks (in CIDR notation) that are considered authenticated [$TRUSTED_IP_ADDRESS]

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 (default: select_account) [$PROVIDERS_GOOGLE_PROMPT]

OIDC Provider:
      --providers.oidc.issuer-url=                          Issuer URL [$PROVIDERS_OIDC_ISSUER_URL]
      --providers.oidc.client-id=                           Client ID [$PROVIDERS_OIDC_CLIENT_ID]
      --providers.oidc.client-secret=                       Client Secret [$PROVIDERS_OIDC_CLIENT_SECRET]
      --providers.oidc.scope=                               Scopes (default: profile, email) [$PROVIDERS_OIDC_SCOPE]
      --providers.oidc.prompt=                              Optional prompt query [$PROVIDERS_OIDC_PROMPT]
      --providers.oidc.resource=                            Optional resource indicator [$PROVIDERS_OIDC_RESOURCE]

Generic OAuth2 Provider:
      --providers.generic-oauth.auth-url=                   Auth/Login URL [$PROVIDERS_GENERIC_OAUTH_AUTH_URL]
      --providers.generic-oauth.token-url=                  Token URL [$PROVIDERS_GENERIC_OAUTH_TOKEN_URL]
      --providers.generic-oauth.user-url=                   URL used to retrieve user info [$PROVIDERS_GENERIC_OAUTH_USER_URL]
      --providers.generic-oauth.client-id=                  Client ID [$PROVIDERS_GENERIC_OAUTH_CLIENT_ID]
      --providers.generic-oauth.client-secret=              Client Secret [$PROVIDERS_GENERIC_OAUTH_CLIENT_SECRET]
      --providers.generic-oauth.token-style=[header|query]  How token is presented when querying the User URL (default: header) [$PROVIDERS_GENERIC_OAUTH_TOKEN_STYLE]
      --providers.generic-oauth.scope=                      Scopes (default: profile, email) [$PROVIDERS_GENERIC_OAUTH_SCOPE]
      --providers.generic-oauth.prompt=                     Optional prompt query [$PROVIDERS_GENERIC_OAUTH_PROMPT]
      --providers.generic-oauth.resource=                   Optional resource indicator [$PROVIDERS_GENERIC_OAUTH_RESOURCE]

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, soft-auth, or allow.

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

• default-provider

  Set the default provider to use for authentication, this can be overridden within rules. Valid options are currently google or oidc.

  Default: google

• 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)

• match-whitelist-or-domain

  When enabled, users will be permitted if they match either the whitelist or domain parameters.

  This will be enabled by default in v3, but is disabled by default in v2 to maintain backwards compatibility.

  Default: false

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

• 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.

• rule

  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)
      • soft-auth
      • allow
    • domains - optional, same usage as domain
    • provider - same usage as default-provider, supported values:
      • google
      • oidc
    • rule - a rule to match a request, this uses traefik's v3 rule parser for which you can find the documentation here: https://docs.traefik.io/v3.0/routing/routers/#rule, supported values are summarised here:
      • Header(`key`, `value`)
      • HeaderRegexp(`key`, `regexp`)
      • Host(`example.com`)
      • HostRegexp(`^[a-z]+.example.com`)
      • Method(`OPTIONS`)
      • Path(`path`)
      • PathRegexp(`^/articles/{category}/[0-9]+$`)
      • PathPrefix(`/products/`)
      • Query(`foo=bar`)
    • whitelist - optional, same usage as whitelist`](#whitelist)

  For example:

  # Allow requests that being with `/api/public` and contain the `Content-Type` header with a value of `application/json`
  rule.1.action = allow
  rule.1.rule = PathPrefix(`/api/public`) && Header(`Content-Type`, `application/json`)
  
  # Allow requests that have the exact path `/public`
  rule.two.action = allow
  rule.two.rule = Path(`/public`)
  
  # Use OpenID Connect provider (must be configured) for requests that begin with `/github`
  rule.oidc.action = auth
  rule.oidc.provider = oidc
  rule.oidc.rule = PathPrefix(`/github`)
  
  # Allow jane@example.com to `/janes-eyes-only`
  rule.two.action = allow
  rule.two.rule = Path(`/janes-eyes-only`)
  rule.two.whitelist = jane@example.com
  

  Note: It is possible to break your redirect flow with rules, please be careful not to create an allow rule that matches your redirect_uri unless you know what you're doing. This limitation is being tracked in in #101 and the behaviour will change in future releases.

• trusted-ip-address

  This option adds an IP address or an IP network given in CIDR notation to the list of trusted networks. Requests originating from a trusted network are considered authenticated and are never redirected to an OAuth IDP. The option can be used multiple times to add many trusted address ranges.

  • --trusted-ip-address=2.3.4.5 adds a single IP (2.3.4.5) as a trusted IP.
  • --trusted-ip-address=30.1.0.0/16 adds the address range from 30.1.0.1 to 30.1.255.254 as a trusted range

  The list of trusted networks is initially empty.

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 both whitelist and domain, then the default behaviour is for only whitelist to be used and domain will be effectively ignored. You can allow users matching either whitelist or domain by passing the match-whitelist-or-domain parameter (this will be the default behaviour in v3). If you set domains or whitelist on a rule, 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 below in the Applying Authentication section.

Applying Authentication

Authentication can be applied in a variety of ways, either globally across all requests, or selectively to specific containers/ingresses.

Global Authentication

This can be achieved by enabling forward authentication for an entire entrypoint, for example, with http only:

--entryPoints.http.address=:80
--entrypoints.http.http.middlewares=traefik-forward-auth # "default-traefik-forward-auth" on kubernetes

Or https:

--entryPoints.http.address=:80
--entryPoints.http.http.redirections.entryPoint.to=https
--entryPoints.http.http.redirections.entryPoint.scheme=https
--entryPoints.https.address=:443
--entrypoints.https.http.middlewares=traefik-forward-auth # "default-traefik-forward-auth" on kubernetes

Note: Traefik prepends the namespace to the name of middleware defined via a kubernetes resource. This is handled automatically when referencing the middleware from another resource in the same namespace (so the namespace does not need to be prepended when referenced). However the full name, including the namespace, must be used when referenced from static configuration (e.g. command arguments or config file), hence you must prepend the namespace to your traefik-forward-auth middleware reference, as shown in the comments above (e.g. default-traefik-forward-auth if your middleware is named traefik-forward-auth and is defined in the default namespace).

Selective Ingress Authentication in Kubernetes

If you choose not to enable forward authentication for a specific entrypoint, you can apply the middleware to selected ingressroutes:

apiVersion: traefik.containo.us/v1alpha1
kind: IngressRoute
metadata:
  name: whoami
  labels:
    app: whoami
spec:
  entryPoints:
    - http
  routes:
  - match: Host(`whoami.example.com`)
    kind: Rule
    services:
      - name: whoami
        port: 80
    middlewares:
      - name: traefik-forward-auth

See the examples directory for more examples.

Selective Container Authentication in Swarm

You can apply labels to selected containers:

whoami:
  image: containous/whoami
  labels:
    - "traefik.http.routers.whoami.rule=Host(`whoami.example.com`)"
    - "traefik.http.routers.whoami.middlewares=traefik-forward-auth"

See the examples directory for more examples.

Rules Based Authentication

You can also leverage the rules config to selectively apply authentication via traefik-forward-auth. For example if you enabled global authentication by enabling forward authentication for an entire entrypoint, you can still exclude some patterns from requiring authentication:

# Allow requests to 'dash.example.com'
rule.1.action = allow
rule.1.rule = Host(`dash.example.com`)

# Allow requests to `app.example.com/public`
rule.two.action = allow
rule.two.rule = Host(`app.example.com`) && Path(`/public`)

Operation Modes

Overlay Mode

Overlay is the default operation mode, in this mode the authorisation endpoint is overlaid 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 or this kubernetes example).

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 and the ingressroute resource in a kubernetes example.

Logging in

The service provides an endpoint to allow users to explicitly login. This is useful for routes in which the auth action is soft-auth.

You can set redirect query parameter to redirect on login (defaults to /).

Logging Out

The service provides an endpoint to clear a users session and "log them out". The path is created by appending /logout to your configured path and so with the default settings it will be: /_oauth/logout.

You can set redirect query parameter to redirect on logout (defaults to /). Note that the user will not have a valid auth cookie after being logged out.

Note: This only clears the auth cookie from the users browser and as this service is stateless, it does not invalidate the cookie against future use. So if the cookie was recorded, for example, it could continue to be used for the duration of the cookie lifetime.

Copyright

2018 Thom Seddon

License

MIT