Kerberos integration
GitLab can be configured to allow your users to sign with their Kerberos credentials.
Configuration
For GitLab to offer Kerberos token-based authentication, perform the following prerequisites. You still need to configure your system for Kerberos usage, such as specifying realms. GitLab will make use of the system's Kerberos settings.
GitLab keytab
- Create a Kerberos Service Principal for the HTTP service on your GitLab server.
If your GitLab server is
gitlab.example.com
and your Kerberos realmEXAMPLE.COM
, create a Service PrincipalHTTP/gitlab.example.com@EXAMPLE.COM
in your Kerberos database. - Create a keytab on the GitLab server for the above Service Principal, e.g.
/etc/http.keytab
.
The keytab is a sensitive file and must be readable by the GitLab user. Set ownership and protect the file appropriately:
sudo chown git /etc/http.keytab
sudo chmod 0600 /etc/http.keytab
Configure GitLab
Installations from source
Note: For source installations, make sure the
kerberos
gem group has been installed.
-
Edit the kerberos section of gitlab.yml to enable Kerberos ticket-based authentication. In most cases, you only need to enable Kerberos and specify the location of the keytab:
omniauth: enabled: true allow_single_sign_on: ['kerberos'] kerberos: # Allow the HTTP Negotiate authentication method for Git clients enabled: true # Kerberos 5 keytab file. The keytab file must be readable by the GitLab user, # and should be different from other keytabs in the system. # (default: use default keytab from Krb5 config) keytab: /etc/http.keytab
Restart GitLab for the changes to take effect.
Omnibus package installations
-
Edit
/etc/gitlab/gitlab.rb
:gitlab_rails['omniauth_enabled'] = true gitlab_rails['omniauth_allow_single_sign_on'] = ['kerberos'] gitlab_rails['kerberos_enabled'] = true gitlab_rails['kerberos_keytab'] = "/etc/http.keytab"
Reconfigure GitLab for the changes to take effect.
GitLab will now offer the negotiate
authentication method for signing in and
HTTP Git access, enabling Git clients that support this authentication protocol
to authenticate with Kerberos tokens.
Creating and linking Kerberos accounts
The Administrative user can navigate to Admin > Users > Example User > Identities
and attach a Kerberos account. Existing GitLab users can go to Profile > Account
and attach a Kerberos account. If you want to allow users without a GitLab
account to login, you should enable the option allow_single_sign_on
as
described in the Configure GitLab section. Then, the first
time a user signs in with Kerberos credentials, GitLab will create a new GitLab
user associated with the email, which is built from the Kerberos username and
realm. User accounts will be created automatically when authentication was
successful.
HTTP Git access
A linked Kerberos account enables you to git pull
and git push
using your
Kerberos account, as well as your standard GitLab credentials.
GitLab users with a linked Kerberos account can also git pull
and git push
using Kerberos tokens, i.e., without having to send their password with each
operation.
HTTP Git access with Kerberos token (passwordless authentication)
Support for Git before 2.4
Until Git version 2.4, the git
command uses only the negotiate
authentication
method if the HTTP server offers it, even if this method fails (such as when
the client does not have a Kerberos token). It is thus not possible to fall back
to username/password (also known as basic
) authentication if Kerberos
authentication fails.
For GitLab users to be able to use either basic
or negotiate
authentication
with older Git versions, it is possible to offer Kerberos ticket-based
authentication on a different port (e.g. 8443) while the standard port will
keep offering only basic
authentication.
For source installations with HTTPS
-
Edit the NGINX configuration file for GitLab (e.g.,
/etc/nginx/sites-available/gitlab-ssl
) and configure NGINX to listen to port8443
in addition to the standard HTTPS port:server { listen 0.0.0.0:443 ssl; listen [::]:443 ipv6only=on ssl default_server; listen 0.0.0.0:8443 ssl; listen [::]:8443 ipv6only=on ssl;
-
Update the Kerberos section of gitlab.yml:
kerberos: # Dedicated port: Git before 2.4 does not fall back to Basic authentication if Negotiate fails. # To support both Basic and Negotiate methods with older versions of Git, configure # nginx to proxy GitLab on an extra port (e.g. 8443) and uncomment the following lines # to dedicate this port to Kerberos authentication. (default: false) use_dedicated_port: true port: 8443 https: true
Restart GitLab and NGINX for the changes to take effect.
For Omnibus package installations
-
Edit
/etc/gitlab/gitlab.rb
:gitlab_rails['kerberos_use_dedicated_port'] = true gitlab_rails['kerberos_port'] = 8443 gitlab_rails['kerberos_https'] = true
Reconfigure GitLab for the changes to take effect.
After this change, all Git remote URLs will have to be updated to
https://gitlab.example.com:8443/mygroup/myproject.git
in order to use
Kerberos ticket-based authentication.
Upgrading from password-based to ticket-based Kerberos sign-ins
Prior to GitLab 8.10 Enterprise Edition, users had to submit their Kerberos username and password to GitLab when signing in. We will remove support for password-based Kerberos sign-ins in a future release, so we recommend that you upgrade to ticket-based sign-ins.
Depending on your existing GitLab configuration, the 'Sign in with: Kerberos Spnego' button may already be visible on your GitLab sign-in page. If not, then add the settings described above.
Once you have verified that the 'Kerberos Spnego' button works
without entering any passwords, you can proceed to disable
password-based Kerberos sign-ins. To do this you need only need to
remove the OmniAuth provider named kerberos
from your gitlab.yml
/
gitlab.rb
file.
For installations from source
-
Edit gitlab.yml and remove the
- { name: 'kerberos' }
line under omniauth providers:omniauth: # ... providers: - { name: 'kerberos' } # <-- remove this line
Restart GitLab for the changes to take effect.
For Omnibus installations
-
Edit
/etc/gitlab/gitlab.rb
and remove the{ "name" => "kerberos" }
line undergitlab_rails['omniauth_providers']
:gitlab_rails['omniauth_providers'] = [ { "name" => "kerberos" } # <-- remove this entry ]
Reconfigure GitLab for the changes to take effect.
Support for Active Directory Kerberos environments
When using Kerberos ticket-based authentication in an Active Directory domain,
it may be necessary to increase the maximum header size allowed by NGINX,
as extensions to the Kerberos protocol may result in HTTP authentication headers
larger than the default size of 8kB. Configure large_client_header_buffers
to a larger value in the NGINX configuration.