Novell LINUX ENTERPRISE SERVER 10 - INSTALLATION AND ADMINISTRATION 04-08-2006 Installation Manual page 896

more about X Window System security mechanisms in the man page of Xsecurity
(man Xsecurity).
SSH (secure shell) can be used to encrypt a network connection completely and forward
it to an X server transparently without the encryption mechanism being perceived by
the user. This is also called X forwarding. X forwarding is achieved by simulating an
X server on the server side and setting a DISPLAY variable for the shell on the remote
host. Further details about SSH can be found in
erations
WARNING
If you do not consider the host where you log in to be a secure host, do not
use X forwarding. With X forwarding enabled, an attacker could authenticate
via your SSH connection to intrude on your X server and sniff your keyboard
input, for instance.
50.1.9 Buffer Overflows and Format String
As discussed in
buffer overflows and format string bugs should be classified as issues concerning both
local and network security. As with the local variants of such bugs, buffer overflows
in network programs, when successfully exploited, are mostly used to obtain root
permissions. Even if that is not the case, an attacker could use the bug to gain access
to an unprivileged local account to exploit any other vulnerabilities that might exist on
the system.
Buffer overflows and format string bugs exploitable over a network link are certainly
the most frequent form of remote attacks in general. Exploits for these—programs to
exploit these newly-found security holes—are often posted on the security mailing lists.
They can be used to target the vulnerability without knowing the details of the code.
Over the years, experience has shown that the availability of exploit codes has contribut-
ed to more secure operating systems, obviously due to the fact that operating system
makers were forced to fix the problems in their software. With free software, anyone
has access to the source code (SUSE Linux Enterprise comes with all available source
codes) and anyone who finds a vulnerability and its exploit code can submit a patch to
fix the corresponding bug.
896 Installation and Administration
(page 839).
Bugs
Section 50.1.5, "Buffer Overflows and Format String Bugs"
Chapter 45, SSH: Secure Network Op-
(page 893),