# Authentication and Authorization

GitLab integrates with the following external authentication and authorization
providers.

- [LDAP](ldap.md) Includes Active Directory, Apple Open Directory, Open LDAP,
  and 389 Server
- [OmniAuth](../../integration/omniauth.md) Sign in via Twitter, GitHub, GitLab.com, Google,
  Bitbucket, Facebook, Shibboleth, Crowd and Azure
- [SAML](../../integration/saml.md) Configure GitLab as a SAML 2.0 Service Provider
- [CAS](../../integration/cas.md) Configure GitLab to sign in using CAS