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Chapter 16. Hardening block storage on Red Hat OpenStack Platform
OpenStack Block Storage (cinder) is a service that provides software (services and libraries) to self-service manage persistent block-level storage devices. This creates on-demand access to Block Storage resources for use with Compute (nova) instances. This creates software-defined storage through abstraction by virtualizing pools of block storage to a variety of back-end storage devices which can be either software implementations or traditional hardware storage products. The primary functions of this is to manage the creation, attachment, and detachment of the block devices. The consumer requires no knowledge of the type of back-end storage equipment or where it is located.
Compute instances store and retrieve block storage using industry-standard storage protocols such as iSCSI, ATA over Ethernet, or Fibre-Channel. These resources are managed and configured using OpenStack native standard HTTP RESTful API.
16.1. Set the max size for the body of a request
If the maximum body size per request is not defined, the attacker can craft an arbitrary OSAPI request of large size, causing the service to crash and finally resulting in a Denial Of Service attack. Assigning t he maximum value ensures that any malicious oversized request gets blocked ensuring continued availability of the service.
Review whether max_request_body_size under the [oslo_middleware] section in cinder.conf is set to 114688.
16.2. Enable volume encryption
Unencrypted volume data makes volume-hosting platforms especially high-value targets for attackers, as it allows the attacker to read the data for many different VMs. In addition, the physical storage medium could be stolen, remounted, and accessed from a different machine. Encrypting volume data and volume backups can help mitgate these risks and provides defense-in-depth to volume-hosting platforms. Block Storage (cinder) is able to encrypt volume data before it is written to disk, so consider enabling volume encryption, and using Barbican for private key storage.
16.3. Volume Wiping
There are multiple ways to wipe a block storage device. The traditional approach is to set the lvm_type to thin, and then use the volume_clear parameter. Alternatively, if the volume encryption feature is used, then volume wiping is not necessary if the volume encryption key is deleted.
Previously, lvm_type=default was used to signify a wipe. While this method still works, lvm_type=default is not recommended for setting secure delete.
The volume_clear parameter can accept either zero or shred as arguments. zero will write a single pass of zeroes to the device. The shred operation will write three passes of predetermined bit patterns.
