Set a [JWT](https://tools.ietf.org/html/rfc7519) signature to a random string. This is needed for all OAuth2 providers that you choose to configure. *Keep this random string around!*
You'll need it each time you start a chronograf server because it is used to verify user authorization. If you are running multiple chronograf servers in an HA configuration set the `TOKEN_SECRET` on each to allow users to stay logged in. If you want to log all users out every time the server restarts, change the value of `TOKEN_SECRET` to a different value on each restart.
To create a Github OAuth Application follow the [Register your app](https://developer.github.com/guides/basics-of-authentication/#registering-your-app) instructions.
Essentially, you'll register your application [here](https://github.com/settings/applications/new)
The `Homepage URL` should be Chronograf's full server name and port. If you are running it locally for example, make it `http://localhost:8888`
You will need to obtain a client ID and an application secret by following the steps under "Basic Steps" [here](https://developers.google.com/identity/protocols/OAuth2). Chronograf will also need to be publicly accessible via a fully qualified domain name so that Google properly redirects users back to the application.
Similar to Github's organization restriction, Google authentication can be restricted to permit access to Chronograf from only specific domains. These are configured using the `GOOGLE_DOMAINS` ENV or the `--google-domains` switch. Multiple domains are separated with a comma. For example, if we wanted to permit access only from biffspleasurepalace.com and savetheclocktower.com the ENV would be set as follows:
To obtain a client ID and application secret for Heroku, you will need to follow the guide posted [here](https://devcenter.heroku.com/articles/oauth#register-client). Once your application has been created, those two values should be inserted into the following ENVs:
Like the other OAuth2 providers, access to Chronograf via Heroku can be restricted to members of specific Heroku organizations. This is controlled using the `HEROKU_ORGS` ENV or the `--heroku-organizations` switch and is comma-separated. If we wanted to permit access from the `hill-valley-preservation-society` orgization and `the-pinheads` organization, we would use the following ENV:
*`GENERIC_TOKEN_URL` : OAuth 2.0 provider's token endpoint [endpoint](https://tools.ietf.org/html/rfc6749#section-3.2) is used by the client to obtain an access token
*`TOKEN_SECRET` : Used to validate OAuth [state](https://tools.ietf.org/html/rfc6749#section-4.1.1) response. (see above)
By default, auth will remain valid for 30 days via a cookie stored in the browser. This duration can be changed with the environment variable `AUTH_DURATION`. For example, to change it to 1 hour, use:
```sh
export AUTH_DURATION=1h
```
The duration uses the golang [time duration format](https://golang.org/pkg/time/#ParseDuration), so the largest time unit is `h` (hours). So to change it to 45 days, use:
```sh
export AUTH_DURATION=1080h
```
Additionally, for greater security, if you want to require re-authentication every time the browser is closed, set `AUTH_DURATION` to `0`. This will make the cookie transient (aka "in-memory").
