1.1.2 Ensure separate partition exists for /tmp (Scored)
Profile Applicability
Level 2 - Server Level 2 - Workstation
Description
The /tmp
directory is a world-writable directory used for temporary storage by all users and some applications.
Rationale
Since the /tmp
directory is intended to be world-writable, there is a risk of resource exhaustion if it is not bound to a separate partition. In addition, making /tmp
its own file system allows an administrator to set the noexec
option on the mount, making /tmp
useless for an attacker to install executable code. It would also prevent an attacker from establishing a hardlink to a system setuid
program and wait for it to be updated. Once the program was updated, the hardlink would be broken and the attacker would have his own copy of the program. If the program happened to have a security vulnerability, the attacker could continue to exploit the known flaw.
Audit
Run the following command and verify output shows /tmp
is mounted:
# mount | grep /tmp tmpfs on /tmp type tmpfs (rw,nosuid,nodev,noexec,relatime)
Remediation
For new installations, during installation create a custom partition setup and specify a separate partition for /tmp
.
For systems that were previously installed, create a new partition for /tmp
if not using tmpfs
.
Run the following commands to enable systemd /tmp
mounting:
# systemctl unmask tmp.mount # systemctl enable tmp.mount
Edit /etc/systemd/system/local-fs.target.wants/tmp.mount
to configure the /tmp
mount:
[Mount] What=tmpfs Where=/tmp Type=tmpfs Options=mode=1777,strictatime,noexec,nodev,nosuid
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.
References
AJ Lewis, “LVM HOWTO”, http://tldp.org/HOWTO/LVM-HOWTO/