google_auth_proxy

A reverse proxy that provides authentication using Google OAuth2 to validate individual accounts, or a whole google apps domain.

Architecture

    _______       ___________________       __________
    |Nginx| ----> |google_auth_proxy| ----> |upstream| 
    -------       -------------------       ----------
                          ||
                          \/
                  [google oauth2 api]

Installation

Download Prebuilt Binary or build from master with $ go get github.com/bitly/google_auth_proxy which should put the binary in $GOROOT/bin
Register an OAuth Application with Google
Configure Google Auth Proxy using config file, command line options, or environment variables
Deploy behind a SSL endpoint (example provided for Nginx)

OAuth Configuration

You will need to register an OAuth application with google, and configure it with Redirect URI(s) for the domain you intend to run google_auth_proxy on.

Create a new project: https://console.developers.google.com/project
Under "APIs & Auth", choose "Credentials"
Now, choose "Create new Client ID"
- The Application Type should be Web application
- Enter your domain in the Authorized Javascript Origins https://internal.yourcompany.com
- Enter the correct Authorized Redirect URL https://internal.yourcompany.com/oauth2/callback
  - NOTE: google_auth_proxy will only callback on the path /oauth2/callback
Under "APIs & Auth" choose "Consent Screen"
- Fill in the necessary fields and Save (this is required)
Take note of the Client ID and Client Secret

Configuration

google_auth_proxy can be configured via config file, command line options or environment variables.

Config File

An example google_auth_proxy.cfg config file is in the contrib directory. It can be used by specifying -config=/etc/google_auth_proxy.cfg

Command Line Options

Usage of google_auth_proxy:
  -authenticated-emails-file="": authenticate against emails via file (one per line)
  -client-id="": the Google OAuth Client ID: ie: "123456.apps.googleusercontent.com"
  -client-secret="": the OAuth Client Secret
  -config="": path to config file
  -cookie-domain="": an optional cookie domain to force cookies to (ie: .yourcompany.com)*
  -cookie-expire=168h0m0s: expire timeframe for cookie
  -cookie-httponly=true: set HttpOnly cookie
  -cookie-https-only=true: set HTTPS only cookie
  -cookie-secret="": the seed string for secure cookies
  -display-htpasswd-form=true: display username / password login form if an htpasswd file is provided
  -google-apps-domain=: authenticate against the given Google apps domain (may be given multiple times)
  -htpasswd-file="": additionally authenticate against a htpasswd file. Entries must be created with "htpasswd -s" for SHA encryption
  -http-address="127.0.0.1:4180": [http://]<addr>:<port> or unix://<path> to listen on for HTTP clients
  -pass-basic-auth=true: pass HTTP Basic Auth, X-Forwarded-User and X-Forwarded-Email information to upstream
  -pass-host-header=true: pass the request Host Header to upstream
  -redirect-url="": the OAuth Redirect URL. ie: "https://internalapp.yourcompany.com/oauth2/callback"
  -skip-auth-regex=: bypass authentication for requests path's that match (may be given multiple times)
  -custom templates-dir="": path to custom html templates
  -upstream=: the http url(s) of the upstream endpoint. If multiple, routing is based on path
  -version=false: print version string

Environment variables

The environment variables GOOGLE_AUTH_PROXY_CLIENT_ID, GOOGLE_AUTH_PROXY_CLIENT_SECRET, GOOGLE_AUTH_PROXY_COOKIE_SECRET, GOOGLE_AUTH_PROXY_COOKIE_DOMAIN and GOOGLE_AUTH_PROXY_COOKIE_EXPIRE can be used in place of the corresponding command-line arguments.

Example Nginx Configuration

This example has a Nginx SSL endpoint proxying to google_auth_proxy on port 4180. google_auth_proxy then authenticates requests for an upstream application running on port 8080. The external endpoint for this example would be https://internal.yourcompany.com/.

An example Nginx config follows. Note the use of Strict-Transport-Security header to pin requests to SSL via HSTS:

server {
    listen 443 default ssl;
    server_name internal.yourcompany.com;
    ssl_certificate /path/to/cert.pem;
    ssl_certificate_key /path/to/cert.key;
    add_header Strict-Transport-Security max-age=1209600;

    location / {
        proxy_pass http://127.0.0.1:4180;
        proxy_set_header Host $host;
        proxy_set_header X-Real-IP $remote_addr;
        proxy_set_header X-Scheme $scheme;
        proxy_connect_timeout 1;
        proxy_send_timeout 30;
        proxy_read_timeout 30;
    }
}

The command line to run google_auth_proxy would look like this:

./google_auth_proxy \
   --google-apps-domain="yourcompany.com"  \
   --upstream=http://127.0.0.1:8080/ \
   --cookie-secret=... \
   --cookie-https-only=true \
   --client-id=... \
   --client-secret=...

Endpoint Documentation

Google Auth Proxy responds directly to the following endpoints. All other endpoints will be proxied upstream when authenticated.

/ping - returns an 200 OK response
/oauth2/sign_in - the login page, which also doubles as a sign out page (it clears cookies)
/oauth2/start - a URL that will redirect to start the OAuth cycle
/oauth2/callback - the URL used at the end of the OAuth cycle. The oauth app will be configured with this ass the callback url.

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