FreeBSD Security Advisory FreeBSD-SA-01:65.libgtop

FreeBSD Security Advisories security-advisories at
Tue Dec 11 09:01:04 PST 2001


FreeBSD-SA-01:65                                            Security Advisory
                                                                FreeBSD, Inc.

Topic:          Buffer overflow in libgtop_server

Category:       ports
Module:         libgtop
Announced:      2001-12-11
Credits:        Flavio Veloso <flaviovs at>
Affects:        Ports collection prior to the correction date
Corrected:      2001-11-29 15:06:19 UTC
FreeBSD only:   NO

I.   Background

libgtop is a library for gtop, the GNOME version of the top command.
The top command is a tool to display and update information about the
top cpu processes.

II.  Problem Description

The libgtop port versions prior to libgtop-1.0.12_1 contain a stack
buffer overflow in libgtop_server, allowing an arbitrary amount of
data from the client application (assumed to be gtop) to be read
into a fixed-sized buffer.  A local attacker can exploit this bug to
cause libgtop_server to execute arbitrary code. libgtop_server runs
with increased privileges as a member of group kmem, which allows
it to read kernel memory (but not write it).  A process with the
ability to read from kernel memory can monitor privileged data such as
network traffic, disk buffers and terminal activity, and may be able
to leverage this to obtain further privileges on the local system or
on other systems, including root privileges.

The libgtop 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 6000 third-party applications in a ready-to-install
format. The ports collection shipped with FreeBSD 4.4 contains 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

A successful exploit of this stack buffer overflow would allow an
attacker arbitrary access to kernel memory, possibly acquiring
information allowing further increases in privileges.

No exploit is known to exist at this time, and it is not known
whether this buffer overflow is exploitable even in theory.  In any
case, local access to the machine on which libgtop_server is running
is required to attempt an attack.

IV.  Workaround

1) Deinstall the libgtop port/package if you have it installed.


2) Remove the setgid bit from the libgtop_server executable by
executing the following command as root:

# chmod g-s `which libgtop_server`

V.   Solution

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

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


Packages are not automatically generated for the alpha architecture at
this time due to lack of build resources.

NOTE: It may be several days before updated packages are available. Be
sure to check the file creation date on the package, because the
version number of the software has not changed.

3) Download a new port skeleton for the libgtop 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:

VI.  Correction details

The following list contains the revision numbers of each file that was
corrected in the FreeBSD ports collection.

Path                                                             Revision
- -------------------------------------------------------------------------
ports/devel/libgtop/Makefile                                         1.45
ports/devel/libgtop/files/patch-src::daemon::gnuserv.c                1.1
- -------------------------------------------------------------------------

VII. References




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