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We keep seeing people concerned about data leakage and thorough deletion of data from volumes on volume deletion [1][2], and Cinder currently only worries about the data leakage, not the stealing of the physical disks. In order to clarify this for administrators and to reduce the number of specs proposed to address this issue we are adding additional documentation on security aspects as well as data leakage. This patch was decided as an action from the discussion during the Wallaby PTG [3]. [1]: https://review.opendev.org/#/c/758375/ [2]: https://review.opendev.org/#/c/759553/ [3]: https://wiki.openstack.org/wiki/CinderWallabyPTGSummary#Two_proposed_specs_on_the_same_topic_.28mutually_assured_destruction.29 Change-Id: I9f8d413cf8337e75241ad24c85692135b34a17fc Implements: blueprint specify-data-secure-deletion
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Security
Network traffic
Depending on your deployment's security requirements, you might be required to encrypt network traffic. This can be accomplished with TLS.
There are multiple deployment options, with the most common and recommended ones being:
- Only encrypt traffic between clients and public endpoints. This approach results in fewer certificates to manage, and we refer to it as public TLS. Public endpoints, in this sense, are endpoints only exposed to end-users. Traffic between internal endpoints is not encrypted.
- Leverages TLS for all endpoints in the entire deployment, including internal endpoints of the OpenStack services and with auxiliary services such as the database and the message broker.
You can look at TripleO's documentation on TLS for examples on how to do this.
Cinder drivers should support secure TLS/SSL communication between
the cinder volume service and the backend, as configured by the
driver_ssl_cert_verify and
driver_ssl_cert_path options in
cinder.conf.
If unsure whether your driver supports TLS/SSL, please check the
driver's specific page in the volume-drivers page or contact the vendor.
Data at rest
Volumes' data can be secured at rest using Cinder's volume encryption feature.
For encryption keys Cinder uses a Key management service, with Barbican being the recommended service.
More information on encryption can be found on the volume-encryption
section.
Data leakage
Some users and admins worry about data leakage between OpenStack projects or users caused by a new volume containing partial or full data from a previously deleted volume.
These concerns are sometimes instigated by the
volume_clear and volume_clear_size
configuration options, but these options are only relevant to the LVM
driver, and only when using thick volumes (which are not the default,
thin volumes are).
Writing data on a Cinder volume as a generic mechanism to prevent data leakage is not implemented for other drivers because it does not ensure that the data will be actually erased on the physical disks, as the storage solution could be doing copy-on-write or other optimizations.
Thin provisioned volumes return zeros for unallocated blocks, so we don't have to worry about data leakage. As for thick volumes, each of the individual Cinder drivers must ensure that data from a deleted volume can never leak to a newly created volume.
This prevents other OpenStack projects and users from being able to get data from deleted volumes, but since the data may still be present on the physical disks, somebody with physical access to the disks may still be able to retrieve that data.
For those concerned with this, we recommend using encrypted volumes or read your storage solution's documentation or contact your vendor to see if they have some kind of clear policy option available on their storage solution.