HP-UX System Administrator's Guide: Security Management HP-UX 11i v3 (B3921-90020, September 2010)

Problem 2: The user database is not functioning properly. If you need to check the
user database, enter the following command:
# userdbck
The userdbck command identifies and repairs problems in the user database.
2.6 Handling setuid and setgid Programs
Because they pose a potential security risk to the system, note which programs are
setuid (set user ID) and setgid (set group ID) programs. A system attacker can
exploit setuid and setgid programs, most often in one of two ways:
• By having a setuid or setgid program execute commands defined by the
attacker, either interactively or by script.
• By substituting bogus data for the data created by a program.
Follow these guidelines to secure setuid and setgid programs:
• Watch for any changes to setuid and setgid programs.
• Investigate further any programs that appear to be unnecessary setuid programs.
• Change the permission of a program that is unnecessarily a setuid program to
a setgid program. See chmod(1) and chmod(2) for more information.
The long form of the ls command (ll or ls -l) shows setuid programs by
listing S or s instead of - or x for the owner-execute permission. It shows setgid
programs by listing S or s instead of - or x for the group-execute permission.
You can expect to find setuid and setgid system files, but they should have
the same permissions as provided by the factory media, unless you have customized
them.
• Do not allow users to normally have setuid programs, especially when they use
setuid to users other than themselves.
• Examine the code of all programs imported from external sources for destructive
programs known as Trojan Horses. Never restore or install a setuid program for
which you have no source to examine.
• To allow users access to certain superuser programs, HP recommends that you
use Restricted SMH. Restricted SMH allows non-superusers to access particular
areas of SMH. See smh(1M) for details.
2.6.1 Why setuid and setgid Programs Can Be Risky
Whenever any program is executed, it creates a process with four ID numbers—real
and effective user ID (ruid and euid) and real and effective group ID (rgid and
egid). Typically, these ID pairs are identical.
However, running a setuid or setgid program changes the euid or egid of the
process from that associated with the owner to that of the object. The processes spawned
50 Administering User and System Security