Cinder configuration option can leak secret key from Ceph backend ---

### Summary ### This vulnerability is present only when Cinder has a Ceph backend *and* the ``rbd_keyring_conf`` option in the Cinder configuration file is set. (The option is unset by default.) Under these circumstances, the keyring content may be leaked to a regular user.

### Affected Services / Software ### Cinder, Pike, Queens, Rocky, Stein, Train

### Discussion ### When the ``rbd_keyring_conf`` option is set, a user who creates a volume and then does a local attach of that volume using the Cinder REST API, may discover the keyring content for the Ceph cluster. (This does not apply to the normal Nova attach process. The user must contact the Cinder REST API directly for this exploit.)

If this user then gains access to the Ceph cluster independently of Cinder, these credentials may be used to access any volume in the cluster.

This issue was reported by Raphael Glon of OVH.

NOTE: This issue is different from OSSA-2019-003, through which Ceph credentials could be leaked from the Nova REST API during error conditions, but we suggest you take this opportunity to review that security advisory and make sure your system has been updated or patched to address it:

https://security.openstack.org/ossa/OSSA-2019-003.html

### Recommended Actions ### Any installation currently using the ``rbd_keyring_conf`` option should immediately stop using that option. In order for Cinder backups to continue working, the Ceph keyring secrets should be deployed directly on cinder-backup hosts in their standard location:

/etc/ceph/<cluster_name>.client.<user_name>.keyring

The ``rbd_keyring_conf`` is deprecated in the Ussuri release and will be removed early in the 'V' development cycle. There is no replacement planned for this functionality.

### Contacts / References ### Author: Brian Rosmaita, Red Hat This OSSN : https://wiki.openstack.org/wiki/OSSN/OSSN-0085 Original LaunchPad Bug : https://bugs.launchpad.net/cinder/+bug/1849624 Mailing List : [Security] tag on openstack-discuss@lists.openstack.org OpenStack Security Project : https://launchpad.net/~openstack-ossg