Updated VNC packages fix replay and cookie vulnerabilities

Updated VNC packages are available, fixing a challenge replay and a weak
cookie vulnerability.

[Updated 10 July 2003]
Added packages for Red Hat Linux on IBM iSeries and pSeries systems.

VNC is a tool for providing a remote graphical user interface. Two
vulnerabilities have been found in versions of VNC shipped by Red Hat.

The VNC server acts as an X server, but the script for starting it
generates an MIT X cookie (which is used for X authentication) without
using a sufficiently strong random number generator. This could allow an
attacker to more easily guess the authentication cookie.

The VNC DES authentication scheme is implemented using a challenge-response
architecture, producing a random and different challenge for each
authentication attempt. A bug in the function for generating the random
challenge caused the random seed to be reset to the current time on every
authentication attempt. Therefore, two authentication attempts within the
same second could receive the same challenge. An eavesdropper could
exploit this vulnerability by replaying the response, thereby gaining
authentication.

All users of VNC are advised to upgrade to these erratum packages, which
contain patches to correct these issues.

Note that when using VNC on an untrusted network, always make sure to
tunnel it through a secure authenticated protocol such as SSH.

Before applying this update, make sure all previously released errata
relevant to your system have been applied.

To update all RPMs for your particular architecture, run:

rpm -Fvh [filenames]

where [filenames] is a list of the RPMs you wish to upgrade. Only those
RPMs which are currently installed will be updated. Those RPMs which are
not installed but included in the list will not be updated. Note that you
can also use wildcards (*.rpm) if your current directory *only* contains the
desired RPMs.

Please note that this update is also available via Red Hat Network. Many
people find this an easier way to apply updates. To use Red Hat Network,
launch the Red Hat Update Agent with the following command:

up2date

This will start an interactive process that will result in the appropriate
RPMs being upgraded on your system.

78828 - Upgrade to tightVNC 1.2.7 from 1.2.2

http://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2002-1336
http://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2002-1511
http://marc.theaimsgroup.com/?l=bugtraq&m=102753170201524

challenge, cookie, mkcookie, replay, vnc