Archive of FreeBSD Security general posting, FreeBSD Security Advisory: FreeBSD-SA-00:62.top [REISSUED]

07/11/00, FreeBSD Security Advisory: FreeBSD-SA-00:62.top [REISSUED]
From: FreeBSD Security Advisories <security-advisories@FreeBSD.ORG>

Generated by MHonArc

CSIM Logo WelcomeCourses
Faculty, Student, Staff
Projects and reports
Conferences, workshop and seminars
Laboratories and reasearch facilities
Information related to CSIM
Information non-related to CSIM
Address, map, phone, etc.
Search

[Date Prev] [Date Next] [Thread Prev] [Thread Next] [Date Index] [Thread Index]


To: FreeBSD Security Advisories <security-advisories@FreeBSD.ORG>
Subject: FreeBSD Security Advisory: FreeBSD-SA-00:62.top [REISSUED]
From: FreeBSD Security Advisories <security-advisories@FreeBSD.ORG>
Date: Mon, 6 Nov 2000 12:01:10 -0800 (PST)
Delivered-To: freebsd-security-notifications@freebsd.org
Mail-from: From owner-freebsd-security-notifications@FreeBSD.ORG Tue Nov 7 03:07:06 2000
Reply-To: postmaster@FreeBSD.ORG
Sender: owner-freebsd-security-notifications@FreeBSD.ORG

-----BEGIN PGP SIGNED MESSAGE-----

=============================================================================
FreeBSD-SA-00:62                                           Security Advisory
                                                                FreeBSD, Inc.

Topic:          top allows reading of kernel memory [REISSUED]

Category:       core
Module:         top
Announced:      2000-11-01
Reissued:       2000-11-06
Credits:        vort@wiretapped.net via OpenBSD
Affects:        FreeBSD 3.x (all releases), FreeBSD 4.x (all releases prior
                to 4.2), FreeBSD 3.5.1-STABLE and 4.1.1-STABLE prior
                to the correction date.
Corrected:      2000-11-04 (FreeBSD 4.1.1-STABLE)
                2000-11-05 (FreeBSD 3.5.1-STABLE)
FreeBSD only:   NO

0.   Revision History

v1.0  2000-11-01  Initial release
v1.1  2000-11-06  Updated patch released.

I.   Background

top is a utility for displaying current system resource statistics
such as process CPU and memory use.  It is externally-maintained,
contributed software which is included in FreeBSD by default.

II.  Problem Description

A "format string vulnerability" was discovered in the top(1) utility
which allows unprivileged local users to cause the top process to
execute arbitrary code.  The top utility runs with increased
privileges as a member of the kmem group, which allows it to read from
kernel memory (but not write to 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.

All released versions of FreeBSD prior to the correction date
including 4.0, 4.1, 4.1.1 and 3.5.1 are vulnerable to this problem,
but it was fixed in the 4.1.1-STABLE branch prior to the release of
FreeBSD 4.2-RELEASE.

III. Impact

Local users can read privileged data from kernel memory which may
provide information allowing them to further increase their local or
remote system access privileges.

IV.  Workaround

Remove the setgid bit on the top utilities.  This has the side-effect
that users who are not a member of the kmem group or who are not the
superuser cannot use the top utility.

# chmod g-s /usr/bin/top

V.   Solution

One of the following:

1) Upgrade your vulnerable FreeBSD system to 4.1.1-STABLE or
3.5.1-STABLE after the respective correction dates.

2) Apply the patch below and recompile the relevant files:

NOTE: The original version of this advisory contained an incomplete
patch which does not fully eliminate the security vulnerability. The
additional vulnerability was pointed out by Przemyslaw Frasunek
<venglin@freebsd.lublin.pl>.

Either save this advisory to a file, or download the patch and
detached PGP signature from the following locations, and verify the
signature using your PGP utility.

ftp://ftp.freebsd.org/pub/FreeBSD/CERT/patches/SA-00:62/top.patch.v1.1
ftp://ftp.freebsd.org/pub/FreeBSD/CERT/patches/SA-00:62/top.patch.v1.1.asc

Execute the following commands as root:

# cd /usr/src/contrib/top
# patch -p < /path/to/patch_or_advisory
# cd /usr/src/usr.bin/top
# make depend && make all install

Patch for vulnerable systems:

    Index: display.c
    ===================================================================
    RCS file: /mnt/ncvs/src/contrib/top/display.c,v
    retrieving revision 1.4
    retrieving revision 1.5
    diff -u -r1.4 -r1.5
    --- display.c	1999/01/09 20:20:33	1.4
    +++ display.c	2000/10/04 23:34:16	1.5
    @@ -829,7 +831,7 @@
         register int i;
     
         /* first, format the message */
    -    (void) sprintf(next_msg, msgfmt, a1, a2, a3);
    +    (void) snprintf(next_msg, sizeof(next_msg), msgfmt, a1, a2, a3);
     
         if (msglen > 0)
         {
    Index: top.c
    ===================================================================
    RCS file: /mnt/ncvs/src/contrib/top/top.c,v
    retrieving revision 1.4
    retrieving revision 1.5
    diff -u -r1.4 -r1.5
    --- top.c	1999/01/09 20:20:34	1.4
    +++ top.c	2000/10/04 23:34:16	1.5
    @@ -807,7 +809,7 @@
     				{
     				    if ((errmsg = kill_procs(tempbuf2)) != NULL)
     				    {
    -					new_message(MT_standout, errmsg);
    +					new_message(MT_standout, "%s", errmsg);
     					putchar('\r');
     					no_command = Yes;
     				    }
    Index: top.c
    ===================================================================
    RCS file: /mnt/ncvs/src/contrib/top/top.c,v
    retrieving revision 1.5
    retrieving revision 1.6
    diff -u -r1.5 -r1.6
    --- top.c	2000/10/04 23:34:16	1.5
    +++ top.c	2000/11/03 22:00:10	1.6
    @@ -826,7 +826,7 @@
     				{
     				    if ((errmsg = renice_procs(tempbuf2)) != NULL)
     				    {
    -					new_message(MT_standout, errmsg);
    +					new_message(MT_standout, "%s", errmsg);
     					putchar('\r');
     					no_command = Yes;
     				    }

-----BEGIN PGP SIGNATURE-----
Version: GnuPG v1.0.4 (FreeBSD)
Comment: For info see http://www.gnupg.org

iQCVAwUBOgcN7lUuHi5z0oilAQFqJgP/bn4SN6FaNvazYMaVzypsEgWzofK/kdlu
iWXcdZVkoFZlF4J7e6M/wRn0xS1lvNPlv5yNF4bYa7lnZHeNzS/58v94+Sze2ooV
bgML9JzhfaM0Ps+/mAXO4FzGi+WryTkdZGl9KVkwT+QwuRer/bz4GoJvnrsGuBpf
dXoovvpgwiA=
=hVPb
-----END PGP SIGNATURE-----


To Unsubscribe: send mail to majordomo@FreeBSD.org
with "unsubscribe freebsd-security-notifications" in the body of the message


Previous message sorted by date: FreeBSD Security Advisory: FreeBSD-SA-00:61.tcpdump [REISSUED]
Next message sorted by date: FreeBSD Ports Security Advisory: FreeBSD-SA-00:64.global
Previous message sorted by thread: FreeBSD Security Advisory: FreeBSD-SA-00:61.tcpdump [REISSUED]
Next message by thread: FreeBSD Ports Security Advisory: FreeBSD-SA-00:64.global
Main Index
Thread Index

CSIM home pageWMailAccount managementCSIM LibraryNetwork test toolsSearch CSIM directories
Contact us: Olivier Nicole CSIM    SET    AIT Last update: Nov 2000