FreeBSD Ports Security Advisory: FreeBSD-SA-00:44.xlockmore

FreeBSD Security Advisories security-advisories at
Mon Aug 28 12:49:20 PDT 2000


FreeBSD-SA-00:44                                           Security Advisory
                                                                FreeBSD, Inc.

Topic:          xlockmore port allows reading of password file

Category:       ports
Module:         xlockmore
Announced:      2000-08-28
Credits:        bind <bind at SUBTERRAIN.NET>
Affects:        Ports collection prior to the correction date.
Corrected:      2000-08-15
Vendor status:  Updated version released
FreeBSD only:   NO

I.   Background

xlockmore is a utility for locking console access to an X terminal.

II.  Problem Description

The xlockmore port, versions 4.17 and below, installs the setuid root
binary xlock, which contains a vulnerability due to incorrect use of
the syslog() function. The xlock program correctly drops root
privileges prior to the point of vulnerability, however it may retain
in memory part of the hashed password database for the user accounts
on the system.

Attackers who can retrieve hashed password information from the memory
space of the process can mount attacks against the user account
passwords and possibly gain access to accounts on the system if

The xlockmore 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 3700 third-party applications in a ready-to-install
format. The ports collections shipped with FreeBSD 3.5-RELEASE and
4.1-RELEASE contain this problem, since it was discovered after the

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

Unprivileged local users may be able to gain unauthorised access to
parts of the /etc/spwd.db file, allowing them to mount guessing
attacks against user passwords.

If you have not chosen to install the xlockmore port/package, then your
system is not vulnerable to this problem.

IV.  Workaround

One of the following:

Deinstall the xlockmore port/package, if you have installed it.

V.   Solution

One of the following:

1) Upgrade your entire ports collection and rebuild the xlockmore port.

2) Deinstall the old package and install a new package dated after the
correction date, obtained from:

NOTE: It may be several days before updated packages are available.

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

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:

Version: 2.6.2


This is the moderated mailing list freebsd-announce.
The list contains announcements of new FreeBSD capabilities,
important events and project milestones.
See also the FreeBSD Web pages at

To Unsubscribe: send mail to majordomo at
with "unsubscribe freebsd-announce" in the body of the message

More information about the freebsd-announce mailing list