Chapter 4. Workstation Security

33

Add more complexity by capitalizing at least one letter, such as H.

o7H@f@,7gmHwg.

Finally, do not use the example password above on any of your systems.

While creating secure passwords is imperative, managing them properly is also important, especially

for system administrators within larger organizations. The next section will detail good practices for

creating and managing user passwords within an organization.

4.3.2. Creating User Passwords Within an Organization

If there are a significant number of users in an organization, the system administrator has two basic

options available to force the use of good passwords. They can create passwords for the user, or they

can let the user create his own passwords, while verifying the passwords are of acceptable quality.

Creating the passwords for the users ensures that the passwords are good, but it becomes a daunting

task as the organization grows. It also increases the risk of users writing their passwords down.

For these reasons, system administrators prefer to have the user create their own passwords, but ac 

tively verify that the passwords are good and, in some cases, force users to change their passwords

periodically through password aging.

4.3.2.1. Forcing Strong Passwords

To protect the network from intrusion it is a good idea for system administrators to verify that

the passwords used within an organization are strong ones. When a user is asked to create or

change his password, he can use the command line application

passwd

, which is PAM aware

and will therefore check to see if the password is easy to crack or too short in length via the

pam_cracklib.so

Pluggable Authentication manager (PAM) module. Since PAM is customizable,

it is possible to add further password integrity checkers, such as

pam_passwdqc

(available from

http://www.openwall.com/passwdqc/) or to write your own module. For a list of available PAM

modules, see http://www.kernel.prg/pub/linux/libs/pam/modules.html. For more information about

PAM, see the chapter titled Pluggable Authentication Modules (PAM) in the Official Red Hat Linux

Reference Guide.

It should be noted, however, that the check performed on passwords at the time of their creation

will not discover bad passwords as effectively as running a password cracking program against the

passwords within the organization.

There are many password cracking programs available for Red Hat Linux, although none ship with

the operating system. Below is a brief list of some of the more popular password cracking programs:

John The Ripper   A fast and flexible password cracking program. It allows the use of

multiple word lists and is capable of brute force password cracking. It is available at

http://www.openwall.com/john/.

Crack   Perhaps the most well

known password cracking

software, Crack

is

also very fast, though not as easy to use as John The Ripper. It can be found at

http://www.users.dircon.co.uk/~crypto/index.html

Slurpie   Slurpie is similar to John The Ripper and Crack except it is designed to run

on multiple computers simultaneously, creating a distributed password cracking attack.

It can be found along with a number of other distributed attack security evaluation tools at

http://www.ussrback.com/distributed.htm