Linux Advisory Watch – July 9, 2004

This
week,
advisories were released for webmin, pavuk, kernel, mailman, rsync,
Esearch, Apache, XFree86, libpng, Shorewall, tripwire and httpd. 
The distributors include Debian, Fedora, FreeBSD, Gentoo, Mandrake, Red
Hat and Suse.

Kerberos, Part I

Introduction

Kerberos
is an authentication system developed by the Athena Project at MIT.
When a user logs in, Kerberos authenticates that user (using a
password), and provides the user with a way to prove her identity to
other servers and hosts scattered around the network.

This
authentication is then used by programs such as rlogin to allow the
user to login to other hosts without a password (in place of the
.rhosts file). This authentication method can also used by the mail
system in order to guarantee that mail is delivered to the correct
person, as well as to guarantee that the sender is who he claims to be.

The
overall effect of installing Kerberos and the numerous other programs
that go with it is to virtually eliminate the ability of users to
“spoof” the system into believing they are someone else. Unfortunately,
installing Kerberos is very intrusive, requiring the modification or
replacement of numerous standard programs.

Implementation

Implementing
Kerberos on the client isn’t too difficult, however, it’s a different
story implementing a server. The document The Moron’s Guide to Kerberos
does a good job of explaining Kerberos in more detail, as well as
guiding users and administrators through the process of creating and
using the server. It is available at the following URL:

http://www.isi.edu/gost/brian/security/kerberos.html

Most
distributions include support for Kerberos. Distributions that use PAM
are much easier to configure. Applications normally require recompiling
to support using Kerberos as the authentication mechanism, but PAM
resolves those issues by allowing you to ‘plug-in’ a Kerberos
authentication module.

Kerberos
isn’t for everyone. Install the client support for your distribution if
you require it to connect to a Kerberos server on your network. Install
the Kerberos server if you have to support a large number of
distributed clients and require the extra authentication.

Generally,
using the Secure Shell is a fine alternative for authenticating users
before logging into remote machines or transferring files.

Next
week, we will explore how Kerberos actually works.

Security
Tip Written by Dave Wreski (ben@guardiandigital.com)
Additional tips are available at the following URL:
http://www.linuxsecurity.com/tips/

—–

LinuxSecurity
Feature Extras:

Open
Source Leaving Microsoft Sitting on the Fence? – The open source
model, with special regard to Linux, has no doubt become a formidable
competitor to the once sole giant of the software industry,
Microsoft. It is expected when the market share of an industry leader
becomes threatened, retaliation with new product or service offerings
and marketing campaigns refuting the claims of the new found
competition are inevitable. However, in the case of
Microsoft, it seems they have not taken a solid or plausible position
on the use of open source applications as an alternative to Windows.

Interview with Brian
Wotring, Lead Developer for the Osiris Project – Brian Wotring is
currently the lead developer for the Osiris project and president of
Host Integrity, Inc. He is also the founder of knowngoods.org, an
online database of known good file signatures. Brian is the co-author
of Mac OS X Security and a long-standing member of the Shmoo Group, an
organization of security and cryptography professionals.

Guardian
Digital Launches Next Generation Secure Mail Suite –
Guardian Digital, the premier open source security company, announced
the availability of the next generation Secure Mail Suite, the
industry’s most secure open source corporate email system. This latest
edition has been optimized to support the changing needs of enterprise
and small business customers while continually providing protection
from the latest in email security threats.

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