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FreeBSD-SA-00:48                                           Security Advisory

                                                                FreeBSD, Inc.



Topic:          xchat port inappropriately handles URLs



Category:       ports

Module:         xchat, xchat-devel

Announced:      2000-09-13

Affects:        Ports collection.

Corrected:      2000-08-27

Vendor status:  Updated version released

FreeBSD only:   NO



I.   Background



Xchat is a popular graphical IRC client.



II.  Problem Description



The xchat IRC client provides the ability to launch URLs displayed in

an IRC window in a web browser by right clicking on the URL. However

this was handled incorrectly in versions prior to 1.4.3, and prior to

1.5.7 in the 1.5 development series, and allowed a malicious IRC user

to embed command strings in a URL which could cause an arbitrary

command to be executed as the local user if the URL were to be

"launched" in a browser as described above.



The xchat port is not installed by default, nor is it "part of

FreeBSD" as such: it is part of the FreeBSD ports collection, which

contains over 3800 third-party applications in a ready-to-install

format. The ports collections shipped with FreeBSD 4.0 and 3.5.1

contain this problem since it was discovered after the release.



FreeBSD makes no claim about the security of these third-party

applications, although an effort is underway to provide a security

audit of the most security-critical ports.



III. Impact



Remote IRC users can cause an arbitrary command to be executed by the

local user, if they attempt to launch a malformed URL by right

clicking on it.



If you have not chosen to install the xchat or xchat-devel

ports/packages, then your system is not vulnerable to this problem.



IV.  Workaround



Do not attempt to launch URLs which contain the ` (backtick) character.



V.   Solution



One of the following:



1) Upgrade your entire ports collection and rebuild the xchat or

xchat-devel port.



2) Deinstall the old package and install a new package dated after the

correction date, obtained from:



http://ftp.FreeBSD.org/pub/FreeBSD/ports/i386/packages-3-stable/irc/xchat-1.4.3.tgz

http://ftp.FreeBSD.org/pub/FreeBSD/ports/i386/packages-4-stable/irc/xchat-1.4.3.tgz

http://ftp.FreeBSD.org/pub/FreeBSD/ports/alpha/packages-4-stable/irc/xchat-1.4.3.tgz

http://ftp.FreeBSD.org/pub/FreeBSD/ports/i386/packages-5-current/irc/xchat-1.4.3.tgz

http://ftp.FreeBSD.org/pub/FreeBSD/ports/alpha/packages-5-current/irc/xchat-1.4.3.tgz



3) download a new port skeleton for the xchat port from:



http://www.freebsd.org/ports/



and use it to rebuild the port.



4) Use the portcheckout utility to automate option (3) above. The

portcheckout port is available in /usr/ports/devel/portcheckout or the

package can be obtained from:



http://ftp.FreeBSD.org/pub/FreeBSD/ports/i386/packages-3-stable/devel/portcheckout-2.0.tgz

http://ftp.FreeBSD.org/pub/FreeBSD/ports/i386/packages-4-stable/devel/portcheckout-2.0.tgz

http://ftp.FreeBSD.org/pub/FreeBSD/ports/alpha/packages-4-stable/devel/portcheckout-2.0.tgz

http://ftp.FreeBSD.org/pub/FreeBSD/ports/i386/packages-5-current/devel/portcheckout-2.0.tgz

http://ftp.FreeBSD.org/pub/FreeBSD/ports/alpha/packages-5-current/devel/portcheckout-2.0.tgz



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