Administrator's Guide

• Do not permit individual users to own a device special file other than for a terminal
device or personal printer.
• Before putting a disk or other mountable device of unknown origin into service,
check its files for device special files and setuid programs. See Section 5.9.
5.8 Protecting Disk Partitions and Logical Volumes
A Logical Volume Manager (LVM) is a common disk management tool. LVM divides up
the disk more easily than disk partitions, and the volumes can span multiple disks. Volumes
are logical devices that appear as a physical disk partition. You can use a volume as a
virtual disk partition for such applications as creating a file system or a database.
Following are some security considerations regarding disk partitions and logical volumes:
• Ensure that the device special files for disk partitions and logical volumes are
readable only by root and perhaps by an account used for disk backups. See
Section 5.7.
• Because ownership and permissions are stored in the inode, anyone with write
permission to a mounted partition can set the user ID for any file in that partition.
The file is subject to change regardless of the owner, bypassing the chmod system
call and other security checks.
If the device special file is writable, a user can open that file and access the raw
disk. The user can then directly edit the file system, read files, or change file
permissions and owners.
Make sure the file permissions forbid access to the device special file and allow
only root to read.
• If a program, such as a database application, requires direct access to the partition,
reserve that partition exclusively for the program. Do not mount a partition as a file
system if users can access the partition directly. If you do mount a partition as a file
system, users could edit the underlying file system.
Inform program users that the file's security is enforced by its permission settings
rather than by the HP-UX file system.
5.9 Security Guidelines for Mounting and Unmounting File Systems
The mount command enables you to attach removable file systems and disk or disk
partitions to an existing file tree. The mount command uses a file called /etc/fstab,
which contains a list of available file systems and their corresponding mount points.
Make the /etc/fstab file writable only by root, but readable by others. For more
information on mounting file systems, see fstab(4).
104 File System Security