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Linux Advisory Watch: August 19th 2005
Source: LinuxSecurity.com Contributors - Posted by Benjamin D. Thomas
This week, advisories were released for amd64, fetchmail, Mozilla, heartbeat,
clamav, lam, vim, evolution, audit, evolution, mc, kdeaddons, kdeadmin, kdebase,
kdedu, kdegames, kdegraphics, kdemultimedia, kdenetwork, kdepim, kdesdk, kdetoys,
kdeutils, kdevelop, kdewebdev, koffice, xpdf, arts, kdepim, epiphany, kdbg,
doxygen, ncpfs, gaim, pcre, tar, vnc, metacity, cups, pygtk, shadow-utils, and
netpbm. The distributors include Debian, Fedora, Gentoo, an Red Hat.
Internet
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Hacks From Pax: PHP Web Application Security, Part II
Another common cause of PHP application holes is improper sanitization of user
provided data. For example, if you allow a user to fill out a form and then
pass data from a field on that form to a function like system() or exec() the
data could contain something malicious, like an ; rm -rf * command tacked onto
it.
Never trust user provided data.
Beware functions that launch system commands, think long and hard about checking any data that is passed to them.
Another related but common security flaw in PHP applications is
a SQL injection vulnerability. The magic_quotes_gpc option can
mitigate this, but as with register_globals you should not assume
this setting is on.
For example, in your PHP script you might ask the user for a
user id and password, and then check for the user by passing
the database a query.
SELECT * FROM users WHERE name='$username' AND pass='$password';
However, if the user logging in is malicious and devious, he
may enter the following as his password:
' OR '1'='1
This causes your query to become:
SELECT * FROM users WHERE name='known_user' AND pass='' OR '1'='1';
The user has just logged in with no password, and your
application has been penetrated. To avoid this, check for
the status of magic_quotes_gpc() using the ini_get() function
and if it is disabled, pass all user input that must be included
in a query through addslashes(). This will escape the single
or double quotes in the user input with backslashes, thereby
thwarting the attempted SQL injection attack.
Use magic_quotes_gpc, but don't assume it is on or depend on it.
The addslashes() function should be used on user data passed to SQL queries.
Again, you simply cannot trust user provided data.
The PHP online manual contains an entire chapter on PHP security. It's an excellent
resource, and goes into much more detail on the PHP security issues I've discussed
in this article. Until next time, stay secure, and don't blindly trust any user
provided data.
Linux File
& Directory Permissions Mistakes - One common mistake Linux administrators
make is having file and directory permissions that are far too liberal and
allow access beyond that which is needed for proper system operations. A full
explanation of unix file permissions is beyond the scope of this article,
so I'll assume you are familiar with the usage of such tools as chmod, chown,
and chgrp. If you'd like a refresher, one is available right here on linuxsecurity.com.
Introduction:
Buffer Overflow Vulnerabilities - Buffer overflows are a leading type
of security vulnerability. This paper explains what a buffer overflow is,
how it can be exploited, and what countermeasures can be taken to prevent
the use of buffer overflow vulnerabilities.
Getting
to Know Linux Security: File Permissions - Welcome to the first
tutorial in the 'Getting to Know Linux Security' series. The topic explored
is Linux file permissions. It offers an easy to follow explanation of how
to read permissions, and how to set them using chmod. This guide is intended
for users new to Linux security, therefore very simple. If the feedback is
good, I'll consider creating more complex guides for advanced users. Please
let us know what you think and how these can be improved.
Take advantage of our Linux Security discussion
list! This mailing list is for general security-related questions and comments.
To subscribe send an e-mail to security-discuss-request@linuxsecurity.com
with "subscribe" as the subject.
Thank you for reading the LinuxSecurity.com
weekly security newsletter. The purpose of this document is to provide our readers
with a quick summary of each week's most relevant Linux security headline.
This update fixes several problems where the audit system is
used on systems with SE Linux disabled, it provides a sample CAPP configuration,
adds new auditd config option to keep all logs instead of rotating them,
and does some sanity checks on some rules before sending them to the kernel.
http://www.linuxsecurity.com/content/view/120088
A flaw was discovered in Xpdf in that an attacker could construct
a carefully crafted PDF file that would cause Xpdf to consume all available
disk space in /tmp when opened.
http://www.linuxsecurity.com/content/view/120114
Fedora Core 3 Update: xpdf-3.00-10.6.FC3
15th, August, 2005
A flaw was discovered in Xpdf in that an attacker could construct
a carefully crafted PDF file that would cause Xpdf to consume all available
disk space in /tmp when opened.
http://www.linuxsecurity.com/content/view/120115
Ben Burton notified the KDE security team about several tempfile
handling related vulnerabilities in langen2kvtml, a conversion script
for kvoctrain.
http://www.linuxsecurity.com/content/view/120117
Ben Burton notified the KDE security team about several tempfile
handling related vulnerabilities in langen2kvtml, a conversion script
for kvoctrain. The script must be manually invoked.
http://www.linuxsecurity.com/content/view/120137
Updated acroread packages that fix a security issue are now
available. This update has been rated as having critical security impact
by the Red Hat Security Response Team.
http://www.linuxsecurity.com/content/view/120125
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