1.1.2.5.1 Ensure separate partition exists for /var/tmp

Information

The /var/tmp directory is a world-writable directory used for temporary storage by all users and some applications. Temporary files residing in /var/tmp are to be preserved between reboots.

The default installation only creates a single / partition. Since the /var/tmp directory is world-writable, there is a risk of resource exhaustion. In addition, other operations on the system could fill up the disk unrelated to /var/tmp and cause potential disruption to daemons as the disk is full.

Configuring /var/tmp as its own file system allows an administrator to set additional mount options such as noexec/nosuid/nodev These options limit an attacker's ability to create exploits on the system.

Solution

For new installations, during installation create a custom partition setup and specify a separate partition for /var/tmp

For systems that were previously installed, create a new partition and configure /etc/fstab as appropriate.

Impact:

Resizing filesystems is a common activity in cloud-hosted servers. Separate filesystem partitions may prevent successful resizing or may require the installation of additional tools solely for the purpose of resizing operations. The use of these additional tools may introduce their own security considerations.

See Also

https://workbench.cisecurity.org/benchmarks/18959