1---
2stage: Ecosystem
3group: Integrations
4info: To determine the technical writer assigned to the Stage/Group associated with this page, see https://about.gitlab.com/handbook/engineering/ux/technical-writing/#assignments
5---
6
7# CAS OmniAuth Provider **(FREE SELF)**
8
9To enable the CAS OmniAuth provider you must register your application with your
10CAS instance. This requires the service URL GitLab supplies to CAS. It should be
11something like: `https://gitlab.example.com:443/users/auth/cas3/callback?url`.
12Handling for Single Logout (SLO) is enabled by default, so you only have to
13configure CAS for back-channel logout.
14
151. On your GitLab server, open the configuration file.
16
17   For Omnibus package:
18
19   ```shell
20   sudo editor /etc/gitlab/gitlab.rb
21   ```
22
23   For installations from source:
24
25   ```shell
26   cd /home/git/gitlab
27
28   sudo -u git -H editor config/gitlab.yml
29   ```
30
311. See [Configure initial settings](omniauth.md#configure-initial-settings) for initial settings.
32
331. Add the provider configuration:
34
35   For Omnibus package:
36
37   ```ruby
38   gitlab_rails['omniauth_providers'] = [
39     {
40       name: "cas3",
41       label: "Provider name", # optional label for login button, defaults to "Cas3"
42       args: {
43           url: "CAS_SERVER",
44           login_url: "/CAS_PATH/login",
45           service_validate_url: "/CAS_PATH/p3/serviceValidate",
46           logout_url: "/CAS_PATH/logout"
47       }
48     }
49   ]
50   ```
51
52   For installations from source:
53
54   ```yaml
55   - { name: 'cas3',
56       label: 'Provider name', # optional label for login button, defaults to "Cas3"
57       args: {
58         url: 'CAS_SERVER',
59         login_url: '/CAS_PATH/login',
60         service_validate_url: '/CAS_PATH/p3/serviceValidate',
61         logout_url: '/CAS_PATH/logout' } }
62   ```
63
641. Change 'CAS_PATH' to the root of your CAS instance (such as `cas`).
65
661. If your CAS instance does not use default TGC lifetimes, update the `cas3.session_duration` to at least the current TGC maximum lifetime. To explicitly disable SLO, regardless of CAS settings, set this to 0.
67
681. Save the configuration file.
69
701. [Reconfigure](../administration/restart_gitlab.md#omnibus-gitlab-reconfigure) or
71   [restart GitLab](../administration/restart_gitlab.md#installations-from-source) for the changes to
72   take effect if you installed GitLab via Omnibus or from source respectively.
73
74On the sign in page there should now be a CAS tab in the sign in form.
75