disallow boot from volume from specifying arbitrary volumes

Fix a vulnerability in volume attachment in nova-volume, affecting the
boot-from-volume feature.  By passing a specific volume ID, an
authenticated user may be able to boot from a volume they don't own,
potentially resulting in full access to that 3rd-party volume.
Folsom setups making use of Cinder are not affected.

Fixes bug: 1069904, CVE-2013-0208
Change-Id: I5f7c8d20d3ebf33ce1ce64bf0a8418bd2b5a6411

nova/compute/api.py

@@ -507,6 +507,11 @@ def _create_instance(self, context, instance_type,
                         security_group, block_device_mapping)
                 instances.append(instance)
                 instance_uuids.append(instance['uuid'])
+                self._validate_bdm(context, instance)
+                # send a state update notification for the initial create to
+                # show it going from non-existent to BUILDING
+                notifications.send_update_with_states(context, instance, None,
+                        vm_states.BUILDING, None, None, service="api")
 
         # In the case of any exceptions, attempt DB cleanup and rollback the
         # quota reservations.
@@ -623,6 +628,23 @@ def _update_block_device_mapping(self, elevated_context,
             self.db.block_device_mapping_update_or_create(elevated_context,
                                                           values)
 
+    def _validate_bdm(self, context, instance):
+        for bdm in self.db.block_device_mapping_get_all_by_instance(
+                context, instance['uuid']):
+            # NOTE(vish): For now, just make sure the volumes are accessible.
+            snapshot_id = bdm.get('snapshot_id')
+            volume_id = bdm.get('volume_id')
+            if volume_id is not None:
+                try:
+                    self.volume_api.get(context, volume_id)
+                except Exception:
+                    raise exception.InvalidBDMVolume(id=volume_id)
+            elif snapshot_id is not None:
+                try:
+                    self.volume_api.get_snapshot(context, snapshot_id)
+                except Exception:
+                    raise exception.InvalidBDMSnapshot(id=snapshot_id)
+
     def _populate_instance_for_bdm(self, context, instance, instance_type,
             image, block_device_mapping):
         """Populate instance block device mapping information."""
@@ -735,11 +757,6 @@ def create_db_entry_for_new_instance(self, context, instance_type, image,
         self._populate_instance_for_bdm(context, instance,
                 instance_type, image, block_device_mapping)
 
-        # send a state update notification for the initial create to
-        # show it going from non-existent to BUILDING
-        notifications.send_update_with_states(context, instance, None,
-                vm_states.BUILDING, None, None, service="api")
-
         return instance
 
     def _check_create_policies(self, context, availability_zone,

nova/exception.py

@@ -223,6 +223,20 @@ class InvalidSnapshot(Invalid):
     message = _("Invalid snapshot") + ": %(reason)s"
 
 
+class InvalidBDM(Invalid):
+    message = _("Block Device Mapping is Invalid.")
+
+
+class InvalidBDMSnapshot(InvalidBDM):
+    message = _("Block Device Mapping is Invalid: "
+                "failed to get snapshot %(id)s.")
+
+
+class InvalidBDMVolume(InvalidBDM):
+    message = _("Block Device Mapping is Invalid: "
+                "failed to get volume %(id)s.")
+
+
 class VolumeUnattached(Invalid):
     message = _("Volume %(volume_id)s is not attached to anything")