Add Okta authentication documentation

doc/administration/auth/README.md

@@ -7,5 +7,6 @@ providers.
   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
+- [SAML](../../integration/saml.md) Configure GitLab as a SAML 2.0 Service Provider
+- [Okta](okta.md) Configure GitLab to sign in using Okta

doc/administration/auth/okta.md

+# Okta SSO provider
+
+Okta is a [Single Sign-on provider][okta-sso] that can be used to authenticate
+with GitLab.
+
+The following documentation enables Okta as a SAML provider.
+
+## Configure the Okta application
+
+1. On Okta go to the admin section and choose to **Add an App**.
+1. When the app screen comes up you see another button to **Create an App** and
+   choose SAML 2.0 on the next screen.
+1. Now, very important, add a logo
+   (you can choose it from https://about.gitlab.com/press/). You'll have to
+   crop and resize it.
+1. Next, you'll need the to fill in the SAML general config. Here's an example
+   image.
+
+    ![Okta admin panel view](img/okta_admin_panel.png)
+
+1. The last part of the configuration is the feedback section where you can
+   just say you're a customer and creating an app for internal use.
+1. When you have your app you'll have a few tabs on the top of the app's
+   profile. Click on the SAML 2.0 config instructions button which should
+   look like the following:
+
+    ![Okta SAML settings](img/okta_saml_settings.png)
+
+1. On the screen that comes up take note of the
+   **Identity Provider Single Sign-On URL** which you'll use for the
+   `idp_sso_target_url` on your GitLab config file.
+
+1. **Before you leave Okta make sure you add your user and groups if any.**
+
+---
+
+Now that the Okta app is configured, it's time to enable it in GitLab.
+
+## Configure GitLab
+
+1.  On your GitLab server, open the configuration file:
+
+    **For Omnibus GitLab installations**
+
+    ```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](../../integration/omniauth.md#initial-omniauth-configuration)
+    for initial settings.
+
+1.  To allow your users to use Okta to sign up without having to manually create
+    an account first, don't forget to add the following values to your
+    configuration:
+
+    **For Omnibus GitLab installations**
+
+    ```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 Okta users with existing GitLab users if
+    their email addresses match by adding the following setting:
+
+    **For Omnibus GitLab installations**
+
+    ```ruby
+    gitlab_rails['omniauth_auto_link_saml_user'] = true
+    ```
+
+    **For installations from source**
+
+    ```yaml
+    auto_link_saml_user: true
+    ```
+
+1.  Add the provider configuration.
+
+      >**Notes:**
+      >- 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).
+      >- To get the `idp_cert_fingerprint` fingerprint, first download the
+         certificate from the Okta app you registered and then run:
+         `openssl x509 -in okta.cert -noout -fingerprint`. Substitute `okta.cert`
+         with the location of your certificate.
+      >- Change the value of `idp_sso_target_url`, with the value of the
+         **Identity Provider Single Sign-On URL** from the step when you
+         configured the Okta app.
+      >- Change the value of `issuer` to a unique name, which will identify the application
+         to the IdP.
+      >- Leave `name_identifier_format` as-is.
+
+    **For Omnibus GitLab installations**
+
+    ```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://gitlab.oktapreview.com/app/gitlabdev773716_gitlabsaml_1/exk8odl81tBrjpD4B0h7/sso/saml',
+                 issuer: 'https://gitlab.example.com',
+                 name_identifier_format: 'urn:oasis:names:tc:SAML:2.0:nameid-format:transient'
+               },
+        label: 'Okta' # 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://gitlab.oktapreview.com/app/gitlabdev773716_gitlabsaml_1/exk8odl81tBrjpD4B0h7/sso/saml',
+               issuer: 'https://gitlab.example.com',
+               name_identifier_format: 'urn:oasis:names:tc:SAML:2.0:nameid-format:transient'
+             },
+        label: 'Okta' # optional label for SAML login button, defaults to "Saml"
+      }
+    ```
+
+
+1. [Reconfigure][reconf] or [restart] GitLab for Omnibus and installations
+   from source respectively for the changes to take effect.
+
+You might want to try this out on a incognito browser window.
+
+## Configuring groups
+
+>**Note:**
+Make sure the groups exist and are assigned to the Okta app.
+
+You can take a look of the [SAML documentation][saml] on external groups since
+it works the same.
+
+[okta-sso]: https://www.okta.com/products/single-sign-on/
+[saml]: ../../integration/saml.md#external-groups
+[reconf]: ../restart_gitlab.md#omnibus-gitlab-reconfigure
+[restart]: ../restart_gitlab.md#installations-from-source