Add documentation for using reCAPTCHA

doc/integration/README.md

@@ -13,6 +13,7 @@ See the documentation below for details on how to configure these services.
 - [Slack](slack.md) Integrate with the Slack chat service
 - [OAuth2 provider](oauth_provider.md) OAuth2 application creation
 - [Gmail actions buttons](gmail_action_buttons_for_gitlab.md) Adds GitLab actions to messages
+- [reCAPTCHA](recaptcha.md) Configure GitLab to use Google reCAPTCHA for new users
 
 GitLab Enterprise Edition contains [advanced JIRA support](http://doc.gitlab.com/ee/integration/jira.html) and [advanced Jenkins support](http://doc.gitlab.com/ee/integration/jenkins.html).
 

doc/integration/recaptcha.md

+# reCAPTCHA
+
+GitLab leverages [Google's reCAPTCHA](https://www.google.com/recaptcha/intro/index.html)
+to protect against spam and abuse. GitLab displays the CAPTCHA form on the sign-up page
+to confirm that a real user, not a bot, is attempting to create an account.
+
+## Configuration
+
+To use reCAPTCHA, first you must create a public and private key.
+
+1. Go to the URL: https://www.google.com/recaptcha/admin
+
+1. Fill out the form necessary to obtain reCAPTCHA keys.
+
+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.  Enable reCAPTCHA and add the settings:
+
+    For omnibus package:
+
+    ```ruby
+      gitlab_rails['recaptcha_enabled'] = true
+      gitlab_rails['recaptcha_public_key'] = 'YOUR_PUBLIC_KEY'
+      gitlab_rails['recaptcha_private_key'] = 'YOUR_PUBLIC_KEY'
+    ```
+
+    For installation from source:
+
+    ```
+      recaptcha:
+        enabled: true
+        public_key: 'YOUR_PUBLIC_KEY'
+        private_key: 'YOUR_PRIVATE_KEY'
+    ```
+
+1.  Change 'YOUR_PUBLIC_KEY' to the public key from step 2.
+
+1.  Change 'YOUR_PRIVATE_KEY' to the private key from step 2.
+
+1.  Save the configuration file.
+
+1.  Restart GitLab.