CAS is a single sign-on (SSO) protocol for multiple web applications. A CAS user account does not take up a license seat until the user signs in to your Enterprise instance.

Username considerations with CAS

GitHub Enterprise usernames can only contain alphanumeric characters and dashes (-). GitHub Enterprise will normalize any non-alphanumeric character in your account's username into a dash. For example, a username of will be normalized to gregory-st-john. Note that normalized usernames also can't start or end with a dash. They also can't contain two consecutive dashes.

Usernames created from email addresses are created from the normalized characters that precede the @ character.

If multiple accounts are normalized into the same GitHub Enterprise username, only the first user account is created. Subsequent users with the same username won't be able to sign in.

This table gives examples of how usernames are normalized in GitHub Enterprise:

Username Normalized username Result
Ms.Bubbles ms-bubbles This username is created successfully.
!Ms.Bubbles -ms-bubbles This username is not created, because it starts with a dash.
Ms.Bubbles! ms-bubbles- This username is not created, because it ends with a dash.
Ms!!Bubbles ms--bubbles This username is not created, because it contains two consecutive dashes.
Ms!Bubbles ms-bubbles This username is not created. Although the normalized username is valid, it already exists. ms-bubbles This username is not created. Although the normalized username is valid, it already exists.

Two-factor authentication

When using SAML or CAS, two-factor authentication is not supported or managed on the GitHub Enterprise appliance, but may be supported by the external authentication provider. Two-factor authentication enforcement on organizations is not available. For more information about enforcing two-factor authentication on organizations, see "Requiring two-factor authentication in your organization."

CAS attributes

The following attributes are available.

Attribute name Type Description
username Required The GitHub Enterprise username.

Configuring CAS

Warning: Before configuring CAS on your GitHub Enterprise instance, note that users will not be able to use their CAS usernames and passwords to authenticate API requests or Git operations over HTTP/HTTPS. Instead, they will need to create an access token.

  1. In the upper-right corner of any page, click . Rocketship icon for accessing site admin settings

  2. In the left sidebar, click Management Console. Management Console tab in the left sidebar

  3. In the left sidebar, click Authentication. Authentication tab

  4. Select CAS. CAS select

  5. In the Server URL field, type the full URL of your CAS server. If your CAS server uses a certificate that can't be validated by GitHub Enterprise, you can use the ghe-ssl-ca-certificate-install command to install it as a trusted certificate.