1 files changed, 100 insertions, 0 deletions
diff --git a/app/controllers/concerns/import/github_oauth.rb b/app/controllers/concerns/import/github_oauth.rb
new file mode 100644
index 00000000000..d53022aabf2
--- /dev/null
+++ b/app/controllers/concerns/import/github_oauth.rb
@@ -0,0 +1,100 @@
+# frozen_string_literal: true
+
+module Import
+  module GithubOauth
+    extend ActiveSupport::Concern
+
+    OAuthConfigMissingError = Class.new(StandardError)
+
+    included do
+      rescue_from OAuthConfigMissingError, with: :missing_oauth_config
+    end
+
+    private
+
+    def provider_auth
+      return if session[access_token_key].present?
+
+      go_to_provider_for_permissions unless ci_cd_only?
+    end
+
+    def ci_cd_only?
+      %w[1 true].include?(params[:ci_cd_only])
+    end
+
+    def go_to_provider_for_permissions
+      redirect_to authorize_url
+    end
+
+    def oauth_client
+      raise OAuthConfigMissingError unless oauth_config
+
+      oauth_client_from_config
+    end
+
+    def oauth_client_from_config
+      @oauth_client_from_config ||= ::OAuth2::Client.new(
+        oauth_config.app_id,
+        oauth_config.app_secret,
+        oauth_options.merge(ssl: { verify: oauth_config['verify_ssl'] })
+      )
+    end
+
+    def oauth_config
+      @oauth_config ||= Gitlab::Auth::OAuth::Provider.config_for('github')
+    end
+
+    def oauth_options
+      return unless oauth_config
+
+      oauth_config.dig('args', 'client_options').deep_symbolize_keys
+    end
+
+    def authorize_url
+      state = SecureRandom.base64(64)
+      session[auth_state_key] = state
+      if Feature.enabled?(:remove_legacy_github_client)
+        oauth_client.auth_code.authorize_url(
+          redirect_uri: callback_import_url,
+          scope: 'repo, user, user:email',
+          state: state
+        )
+      else
+        client.authorize_url(callback_import_url, state)
+      end
+    end
+
+    def get_token(code)
+      if Feature.enabled?(:remove_legacy_github_client)
+        oauth_client.auth_code.get_token(code).token
+      else
+        client.get_token(code)
+      end
+    end
+
+    def missing_oauth_config
+      session[access_token_key] = nil
+
+      message = _('Missing OAuth configuration for GitHub.')
+
+      respond_to do |format|
+        format.json do
+          render json: { errors: message }, status: :unauthorized
+        end
+
+        format.any do
+          redirect_to new_import_url,
+            alert: message
+        end
+      end
+    end
+
+    def callback_import_url
+      public_send("users_import_#{provider_name}_callback_url", extra_import_params.merge({ namespace_id: params[:namespace_id] })) # rubocop:disable GitlabSecurity/PublicSend
+    end
+
+    def extra_import_params
+      {}
+    end
+  end
+end