Adds an optional custom icon to the oAuth login label

app/helpers/auth_helper.rb

@@ -17,7 +17,7 @@ module AuthHelper
   end
 
   def provider_has_icon?(name)
-    PROVIDERS_WITH_ICONS.include?(name.to_s)
+    PROVIDERS_WITH_ICONS.include?(name.to_s) || icon_for_provider(name.to_s)
   end
 
   def qa_class_for_provider(provider)
@@ -35,6 +35,10 @@ module AuthHelper
     Gitlab::Auth::OAuth::Provider.label_for(name)
   end
 
+  def icon_for_provider(name)
+    Gitlab::OAuth::Provider.icon_for(name)
+  end
+
   def form_based_provider_priority
     ['crowd', /^ldap/, 'kerberos']
   end
@@ -109,7 +113,9 @@ module AuthHelper
   def provider_image_tag(provider, size = 64)
     label = label_for_provider(provider)
 
-    if provider_has_icon?(provider)
+    if icon_for_provider(provider)
+      image_tag(icon_for_provider(provider), alt: label, title: "Sign in with #{label}")
+    elsif provider_has_icon?(provider)
       file_name = "#{provider.to_s.split('_').first}_#{size}.png"
 
       image_tag("auth_buttons/#{file_name}", alt: label, title: "Sign in with #{label}")

doc/administration/auth/oidc.md

@@ -34,6 +34,7 @@ The OpenID Connect will provide you with a client details and secret for you to
    gitlab_rails['omniauth_providers'] = [
      { 'name' => 'openid_connect',
        'label' => '<your_oidc_label>',
+       'icon' => '<url_to_custom_provider_icon>',
        'args' => {
          'name' => 'openid_connect',
          'scope' => ['openid','profile'],
@@ -58,6 +59,7 @@ The OpenID Connect will provide you with a client details and secret for you to
    ```yaml
      - { name: 'openid_connect',
          label: '<your_oidc_label>',
+         icon: '<url_to_custom_provider_icon>',
          args: {
            name: 'openid_connect',
            scope: ['openid','profile'],
@@ -82,6 +84,8 @@ The OpenID Connect will provide you with a client details and secret for you to
 
 1. For the configuration above, change the values for the provider to match your OpenID Connect client setup. Use the following as a guide:
    - `<your_oidc_label>` is the label that will be displayed on the login page.
+   - `<url_to_custom_provider_icon>` (optional) is the icon that will be displayed on the login page. Icons for the major social login platforms are built-in into Gitlab,
+     but can be overridden by specifying this parameter.
    - `<your_oidc_url>` (optional) is the URL that points to the OpenID Connect provider. For example, `https://example.com/auth/realms/your-realm`.
      If this value is not provided, the URL is constructed from the `client_options` in the following format: `<client_options.scheme>://<client_options.host>:<client_options.port>`.
    - If `discovery` is set to `true`, the OpenID Connect provider will try to auto discover the client options using `<your_oidc_url>/.well-known/openid-configuration`. Defaults to `false`.

lib/gitlab/auth/o_auth/provider.rb

@@ -75,6 +75,12 @@ module Gitlab
           config = config_for(name)
           (config && config['label']) || LABELS[name] || name.titleize
         end
+
+        def self.icon_for(name)
+          name = name.to_s
+          config = config_for(name)
+          config && config['icon']
+        end
       end
     end
   end