Show volume attachment host information for services

When fetching the attachments associated with a volume, Cinder
only return the host information (host_name) if the request
is coming from an admin otherwise returns None.
This is the correct behavior but with a little caveat.
When Glance is configured to use Cinder as it's backend, it
also requires the volume attachment information to find out
which attachments exists for a specific host.
This helps make smart decisions on wheather we want to
disconnect a volume or not[1]. The problem currently is, the
``host_name`` field is not exposed to other openstack
services, like glance.
This patch enables services like Glance API to be able
to fetch the ``host_name`` information for attachments
by checking the ``service`` role in the context of the
request. This helps ensures any non-admin user, apart
from the admin or service category shouldn't be able
to view the ``host_name`` information for attachments.

[1] https://review.opendev.org/c/openstack/glance_store/+/962408

Change-Id: Icea868bf6619f3ab0a00c4e72185f07e66e4a932
Signed-off-by: Rajat Dhasmana <rajatdhasmana@gmail.com>

cinder/api/v2/views/volumes.py

@@ -90,7 +90,7 @@ class ViewBuilder(common.ViewBuilder):
         }
         ctxt = request.environ['cinder.context']
 
-        attachments = self._get_attachments(volume, ctxt.is_admin)
+        attachments = self._get_attachments(volume, ctxt)
         volume_ref['volume']['attachments'] = attachments
 
         if ctxt.is_admin:
@@ -113,7 +113,7 @@ class ViewBuilder(common.ViewBuilder):
         """Determine if volume is encrypted."""
         return volume.get('encryption_key_id') is not None
 
-    def _get_attachments(self, volume, is_admin):
+    def _get_attachments(self, volume, ctxt):
         """Retrieve the attachments of the volume object."""
         attachments = []
 
@@ -124,12 +124,17 @@ class ViewBuilder(common.ViewBuilder):
                      'attachment_id': attachment.get('id'),
                      'volume_id': attachment.get('volume_id'),
                      'server_id': attachment.get('instance_uuid'),
-                     'host_name': attachment.get('attached_host'),
+                     'host_name': None,
                      'device': attachment.get('mountpoint'),
                      'attached_at': attachment.get('attach_time'),
                      }
-                if not is_admin:
-                    a['host_name'] = None
+                # When glance is cinder backed, we require the
+                # host_name to determine when to detach a multiattach
+                # volume. Glance always uses service credentials to
+                # request Cinder so we are not exposing the host value
+                # to end users (non-admin).
+                if ctxt.is_admin or 'service' in ctxt.roles:
+                    a['host_name'] = attachment.get('attached_host')
                 attachments.append(a)
 
         return attachments

cinder/tests/unit/api/v3/test_volumes.py

@@ -1086,6 +1086,8 @@ class VolumeApiTest(test.TestCase):
                           {'revert': {'snapshot_id': fake_snapshot['id']}})
 
     def test_view_get_attachments(self):
+        req = fakes.HTTPRequest.blank('/v3/volumes')
+        context = req.environ['cinder.context']
         fake_volume = self._fake_create_volume()
         fake_volume['attach_status'] = fields.VolumeAttachStatus.ATTACHING
         att_time = datetime.datetime(2017, 8, 31, 21, 55, 7,
@@ -1117,7 +1119,8 @@ class VolumeApiTest(test.TestCase):
 
         # get_attachments should only return attachments with the
         # attached status = ATTACHED
-        attachments = ViewBuilder()._get_attachments(fake_volume, True)
+        context.is_admin = True
+        attachments = ViewBuilder()._get_attachments(fake_volume, context)
 
         self.assertEqual(1, len(attachments))
         self.assertEqual(fake.UUID3, attachments[0]['attachment_id'])
@@ -1128,9 +1131,16 @@ class VolumeApiTest(test.TestCase):
         self.assertEqual(att_time, attachments[0]['attached_at'])
 
         # When admin context is false (non-admin), host_name will be None
-        attachments = ViewBuilder()._get_attachments(fake_volume, False)
+        context.is_admin = False
+        attachments = ViewBuilder()._get_attachments(fake_volume, context)
         self.assertIsNone(attachments[0]['host_name'])
 
+        # When the request is coming from another service (glance),
+        # We should be able to see 'host_name'
+        context.roles.append('service')
+        attachments = ViewBuilder()._get_attachments(fake_volume, context)
+        self.assertEqual('host1', attachments[0]['host_name'])
+
     @ddt.data(('created_at=gt:', 0), ('created_at=lt:', 2))
     @ddt.unpack
     def test_volume_index_filter_by_created_at_with_gt_and_lt(self, change,