saml.md

# SAML OmniAuth Provider

GitLab can be configured to act as a SAML 2.0 Service Provider (SP). This allows
GitLab to consume assertions from a SAML 2.0 Identity Provider (IdP) such as
Microsoft ADFS to authenticate users.

First configure SAML 2.0 support in GitLab, then register the GitLab application
in your SAML IdP:

1.  Make sure GitLab is configured with HTTPS.
    See [Using HTTPS](../install/installation.md#using-https) for instructions.

1.  On your GitLab server, open the configuration file.

    For omnibus package:

    ```sh
      sudo editor /etc/gitlab/gitlab.rb
    ```

    For installations from source:

    ```sh
      cd /home/git/gitlab

      sudo -u git -H editor config/gitlab.yml
    ```

1.  See [Initial OmniAuth Configuration](omniauth.md#initial-omniauth-configuration)
    for initial settings.

1.  To allow your users to use SAML to sign up without having to manually create
    an account first, don't forget to add the following values to your configuration:

    For omnibus package:

    ```ruby
      gitlab_rails['omniauth_allow_single_sign_on'] = ['saml']
      gitlab_rails['omniauth_block_auto_created_users'] = false
    ```

    For installations from source:

    ```yaml
      allow_single_sign_on: ["saml"]
      block_auto_created_users: false
    ```

1.  You can also automatically link SAML users with existing GitLab users if their
    email addresses match by adding the following setting:

    For omnibus package:

    ```ruby
      gitlab_rails['omniauth_auto_link_saml_user'] = true
    ```

    For installations from source:

    ```yaml
      auto_link_saml_user: true
    ```

1.  Add the provider configuration:

    For omnibus package:

    ```ruby
      gitlab_rails['omniauth_providers'] = [
        {
          name: 'saml',
          args: {
                   assertion_consumer_service_url: 'https://gitlab.example.com/users/auth/saml/callback',
                   idp_cert_fingerprint: '43:51:43:a1:b5:fc:8b:b7:0a:3a:a9:b1:0f:66:73:a8',
                   idp_sso_target_url: 'https://login.example.com/idp',
                   issuer: 'https://gitlab.example.com',
                   name_identifier_format: 'urn:oasis:names:tc:SAML:2.0:nameid-format:transient'
                 },
          label: 'Company Login' # optional label for SAML login button, defaults to "Saml"
        }
      ]
    ```

    For installations from source:

    ```yaml
      - {
          name: 'saml',
          args: {
                 assertion_consumer_service_url: 'https://gitlab.example.com/users/auth/saml/callback',
                 idp_cert_fingerprint: '43:51:43:a1:b5:fc:8b:b7:0a:3a:a9:b1:0f:66:73:a8',
                 idp_sso_target_url: 'https://login.example.com/idp',
                 issuer: 'https://gitlab.example.com',
                 name_identifier_format: 'urn:oasis:names:tc:SAML:2.0:nameid-format:transient'
               },
          label: 'Company Login' # optional label for SAML login button, defaults to "Saml"
        }
    ```

1.  Change the value for `assertion_consumer_service_url` to match the HTTPS endpoint
    of GitLab (append `users/auth/saml/callback` to the HTTPS URL of your GitLab
    installation to generate the correct value).

1.  Change the values of `idp_cert_fingerprint`, `idp_sso_target_url`,
    `name_identifier_format` to match your IdP. Check
    [the omniauth-saml documentation](https://github.com/omniauth/omniauth-saml)
    for details on these options.

1.  Change the value of `issuer` to a unique name, which will identify the application
    to the IdP.

1.  Restart GitLab for the changes to take effect.

1.  Register the GitLab SP in your SAML 2.0 IdP, using the application name specified
    in `issuer`.

To ease configuration, most IdP accept a metadata URL for the application to provide
configuration information to the IdP. To build the metadata URL for GitLab, append
`users/auth/saml/metadata` to the HTTPS URL of your GitLab installation, for instance:
   ```
   https://gitlab.example.com/users/auth/saml/metadata
   ```

At a minimum the IdP *must* provide a claim containing the user's email address, using
claim name `email` or `mail`. The email will be used to automatically generate the GitLab
username. GitLab will also use claims with name `name`, `first_name`, `last_name`
(see [the omniauth-saml gem](https://github.com/omniauth/omniauth-saml/blob/master/lib/omniauth/strategies/saml.rb)
for supported claims).

On the sign in page there should now be a SAML button below the regular sign in form.
Click the icon to begin the authentication process. If everything goes well the user
will be returned to GitLab and will be signed in.

## Troubleshooting

### 500 error after login

If you see a "500 error" in GitLab when you are redirected back from the SAML sign in page,
this likely indicates that GitLab could not get the email address for the SAML user.

Make sure the IdP provides a claim containing the user's email address, using claim name
`email` or `mail`.

### Redirect back to login screen with no evident error

If after signing in into your SAML server you are redirected back to the sign in page and
no error is displayed, check your `production.log` file. It will most likely contain the
message `Can't verify CSRF token authenticity`. This means that there is an error during
the SAML request, but this error never reaches GitLab due to the CSRF check.

To bypass this you can add `skip_before_action :verify_authenticity_token` to the
`omniauth_callbacks_controller.rb` file. This will allow the error to hit GitLab,
where it can then be seen in the usual logs, or as a flash message in the login
screen.

### Invalid audience

This error means that the IdP doesn't recognize GitLab as a valid sender and
receiver of SAML requests. Make sure to add the GitLab callback URL to the approved
audiences of the IdP server.

### Missing claims

The IdP server needs to pass certain information in order for GitLab to either
create an account, or match the login information to an existing account. `email`
is the minimum amount of information that needs to be passed. If the IdP server
is not providing this information, all SAML requests will fail.

Make sure this information is provided.

### Key validation error, Digest mismatch or Fingerprint mismatch

These errors all come from a similar place, the SAML certificate. SAML requests
need to be validated using a fingerprint, a certificate or a validator.

For this you need take the following into account:

- If no certificate is provided in the settings, a fingerprint or fingerprint
  validator needs to be provided and the response from the server must contain
  a certificate (`<ds:KeyInfo><ds:X509Data><ds:X509Certificate>`)
- If a certificate is provided in the settings, it is no longer necessary for
  the request to contain one. In this case the fingerprint or fingerprint
  validators are optional

Make sure that one of the above described scenarios is valid, or the requests will
fail with one of the mentioned errors.