Article version: Enterprise Server 2.17
Using CAS
CAS is a single sign-on (SSO) protocol for multiple web applications. A CAS user account does not take up a user license until the user signs in.
If you want to authenticate users without adding them to your identity provider, you can configure built-in authentication. For more information, see "Allowing built-in authentication for users outside your identity provider."
Username considerations with CAS
GitHub Enterprise Server usernames can only contain alphanumeric characters and dashes (-). GitHub Enterprise Server will normalize any non-alphanumeric character in your account's username into a dash. For example, a username of gregory.st.john 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 Server 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 Server:
| 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@example.com | 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 Server 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 Server username. |
Configuring CAS
Warning: Before configuring CAS on your GitHub Enterprise Server 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.
- In the upper-right corner of any page, click .
- In the left sidebar, click Management Console.
- In the left sidebar, click Authentication.
- Select CAS.
- Optionally, select Allow built-in authentication to invite users to use built-in authentication if they don’t belong to your GitHub Enterprise Server instance's identity provider.
- 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 Server, you can use the
ghe-ssl-ca-certificate-installcommand to install it as a trusted certificate.