auth: add compute service account

lib/google/api_client/auth/compute_service_account.rb

@@ -0,0 +1,28 @@
+# Copyright 2013 Google Inc.
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#      http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+require 'faraday'
+require 'signet/oauth_2/client'
+
+module Google
+  class APIClient
+    class ComputeServiceAccount < Signet::OAuth2::Client
+      def fetch_access_token(options={})
+        options[:connection] ||= Faraday.default_connection
+        response = options[:connection].get 'http://metadata/computeMetadata/v1beta1/instance/service-accounts/default/token'
+        Signet::OAuth2.parse_json_credentials(response.body)
+      end
+    end
+  end
+end

lib/google/api_client/service_account.rb

@@ -15,3 +15,4 @@
 require 'google/api_client/auth/pkcs12'
 require 'google/api_client/auth/jwt_asserter'
 require 'google/api_client/auth/key_utils'
+require 'google/api_client/auth/compute_service_account'