Configuration
=============

The configuration of the @PLUGIN@ plugin is done in the `gerrit.config`
file. `auth.type` must be set to `OAUTH`:

```
[auth]
  type = OAUTH
```

Providers are configured under @PLUGIN@ section,
appended with provider suffix: e.g. `-google-oauth` or `-github-oauth`:

```
  [plugin "@PLUGIN@-google-oauth"]
    client-id = "<client-id>"
    client-secret = "<client-secret>"
    link-to-existing-openid-accounts = true

  [plugin "@PLUGIN@-github-oauth"]
    client-id = "<client-id>"
    client-secret = "<client-secret>"

  [plugin "@PLUGIN@-cas-oauth"]
    root-url = "<cas url>"
    client-id = "<client-id>"
    client-secret = "<client-secret>"
```

When one from the sections above is omitted, OAuth SSO is used.
The login form with provider selection isn’t shown. When all
sections are omitted, Gerrit will not start.

Google OAuth provider seamlessly supports linking of OAuth identity
to existing OpenID accounts. This feature is deactivated by default.
To activate it, add

```
plugin.gerrit-oauth-provider-google-oauth.link-to-existing-openid-accounts = true
```

to Google OAuth configuration section.

It is possile to restrict sign-in to accounts of one (hosted) domain for
Google OAuth. The `domain` option can be added:

```
plugin.gerrit-oauth-provider-google-oauth.domain = "mycollege.edu"
```

By default the Google OAuth provider will not set a username (used for ssh) and
the user can choose one from the web ui (needed before using ssh). It is possible
to automatically use the user part from the google apps email. This is deactivated
by default. To activate it, add:

```
plugin.gerrit-oauth-provider-google-oauth.use-email-as-username = true
```

Note: the usernames are unique in gerrit. If a username already exists this will
be ignored and the user will have to choose a different one from the web ui.

(See the spec)[https://developers.google.com/identity/protocols/OpenIDConnect#hd-param]
for more information. To protect against client-side request modification, the returned
ID token is checked to contain a matching hd claim (which is proof the account does belong
to the hosted domain). If the hd claim wasn't included in ID token or didn't match the
provided `domain` configuration option the authentication is rejected. Note: Because of
current limitation of the OAuth extension point in gerrit (blame /me for that) the user
would only see "Unauthorized" message.

### CAS OAuth

For CAS OAuth setting

```
plugin.gerrit-oauth-provider-cas-oauth.root-url = "https://example.com/cas"
```

is required, since CAS is a self-hosted application.

The plugin expects CAS to make several attributes available to it:

| Name | Description | Required |
|---|---|---|
| id | External ID | yes |
| login | Login name | no |
| email |  Email address | no |
| name | Display name | no |

## Obtaining provider authorizations

### Google

To obtain client-id and client-secret for Google OAuth, go to
[Google Developers Console](https://console.developers.google.com):

- Create a project

  ![Create a porject](images/google-1.png)

- Go inside the created project

- In "APIs & auth"/"Credentials" select "Create new Client ID" and
create Client ID for a Web application

  ![Create Client ID for a Web application](images/google-2.png)

- Enter additional information about the project, which will be
  presented to user during the authentication process

  ![Enter additional information](images/google-3.png)

- Specify authorized redirect URL: `<canonical-web-uri-of-gerrit>/oauth`

  ![Specify authorized redirect URI](images/google-4.png)

After the final step, the page will show generated client id and
secret.

![Generated id and secret](images/google-5.png)

### GitHub

To obtain client-id and client-secret for GitHub OAuth, go to
[Applications settings in your GitHub account](https://github.com/settings/applications):

- Select "Register new application" and enter information about the
  application.

  Note that it is important that authorization callback URL points to
  `<canonical-web-uri-of-gerrit>/oauth`.

  ![Register new application on GitHub](images/github-1.png)


After application is registered, the page will show generated client id and
secret.

![Generated client id and secret](images/github-2.png)

### CAS

The client-id and client-secret for CAS OAuth are part of the CAS
service definition and need to be set manually.

See
[the CAS documentation](https://apereo.github.io/cas/4.2.x/installation/OAuth-OpenId-Authentication.html#add-oauth-clients)
for an example.