Merge pull request #50047 from rallytime/bp-49605

Back-port #49605 to 2017.7

doc/topics/cloud/gce.rst

@@ -114,6 +114,12 @@ Set up the provider cloud config at ``/etc/salt/cloud.providers`` or
 
       driver: gce
 
+.. note::
+
+    Empty strings as values for ``service_account_private_key`` and ``service_account_email_address``
+    can be used on GCE instances. This will result in the service account assigned to the GCE instance
+    being used.
+
 .. note::
 
     The value provided for ``project`` must not contain underscores or spaces and

doc/topics/releases/2017.7.9.rst

@@ -4,3 +4,13 @@ In Progress: Salt 2017.7.9 Release Notes
 
 Version 2017.7.9 is an **unreleased** bugfix release for :ref:`2017.7.0 <release-2017-7-0>`.
 This release is still in progress and has not been released yet.
+
+Salt Cloud Features
+===================
+
+GCE Driver
+----------
+The GCE salt cloud driver can now be used with GCE instance credentials by
+setting the configuration paramaters ``service_account_private_key`` and
+``service_account_private_email`` to an empty string.
+

salt/cloud/clouds/gce.py

@@ -129,7 +129,8 @@ def __virtual__():
 
         parameters = details['gce']
         pathname = os.path.expanduser(parameters['service_account_private_key'])
-        if salt.utils.cloud.check_key_path_and_mode(
+        # empty pathname will tell libcloud to use instance credentials
+        if pathname and salt.utils.cloud.check_key_path_and_mode(
                 provider, pathname
         ) is False:
             return False