# Authentication and AuthorizationGitLab integrates with the following external authentication and authorizationproviders.-[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