ID: 28500
Title: Ensure /tmp is a separate partition.
Target: Command: findmnt --kernel /tmp
Rationale: Making /tmp its own file system allows an administrator to set additional mount options such as 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 hard link to a system setuid program and wait for it to be updated. Once the program was updated, the hard link 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. This can be accomplished by either mounting tmpfs to /tmp, or creating a separate partition for /tmp.
Remediation: First ensure that systemd is correctly configured to ensure that /tmp will be mounted at boot time. # systemctl unmask tmp.mount For specific configuration requirements of the /tmp mount for your environment, modify /etc/fstab or tmp.mount. Example of /etc/fstab configured tmpfs file system with specific mount options: tmpfs 0 /tmp tmpfs defaults,rw,nosuid,nodev,noexec,relatime,size=2G 0 Example of tmp.mount configured tmpfs file system with specific mount options: [Unit] Description=Temporary Directory /tmp ConditionPathIsSymbolicLink=!/tmp DefaultDependencies=no Conflicts=umount.target Before=local-fs.target umount.target After=swap.target [Mount] What=tmpfs Where=/tmp Type=tmpfs.
Description: The /tmp directory is a world-writable directory used for temporary storage by all users and some applications.
ID: 28500 Title: Ensure /tmp is a separate partition. Target: Command: findmnt --kernel /tmp
Rationale: Making /tmp its own file system allows an administrator to set additional mount options such as 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 hard link to a system setuid program and wait for it to be updated. Once the program was updated, the hard link 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. This can be accomplished by either mounting tmpfs to /tmp, or creating a separate partition for /tmp.
Remediation: First ensure that systemd is correctly configured to ensure that /tmp will be mounted at boot time. # systemctl unmask tmp.mount For specific configuration requirements of the /tmp mount for your environment, modify /etc/fstab or tmp.mount. Example of /etc/fstab configured tmpfs file system with specific mount options: tmpfs 0 /tmp tmpfs defaults,rw,nosuid,nodev,noexec,relatime,size=2G 0 Example of tmp.mount configured tmpfs file system with specific mount options: [Unit] Description=Temporary Directory /tmp ConditionPathIsSymbolicLink=!/tmp DefaultDependencies=no Conflicts=umount.target Before=local-fs.target umount.target After=swap.target [Mount] What=tmpfs Where=/tmp Type=tmpfs.
Description: The /tmp directory is a world-writable directory used for temporary storage by all users and some applications.
Checks:
c:findmnt --kernel /tmp -> r:\s*/tmp\s c:systemctl is-enabled tmp.mount -> r:generated|enabled