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Home » Hacking News » SuSE-SA:2002:009-local and remote command execution

SuSE-SA:2002:009-local and remote command execution

by Nikola Strahija on March 12th, 2002 Content of this advisory: 1) security vulnerability resolved: openssh problem description, discussion, solution and upgrade information 2) pending vulnerabilities, solutions, workarounds 3) standard appendix (further information)


1) problem description, brief discussion, solution, upgrade information

Joost Pol discovered an off-by-one bug in a routine in the openssh code
for checking channel IDs. This bug can be exploited on the remote side
by an already authenticated user, qualifying this bug as a local security
vulnerability, and on the local side if a malicious server attacks the
connected client, qualifying this bug as a remote vulnerability.
If the error is being exploited, it leads to arbitrary code execution
in the process under attack (either a local ssh client, attacking the
userID of the client user, or a remote secure shell daemon that has
an authenticated user session running, attacking the root account of
the remote system).
Please note that the possible attack scenario is different from the usual
attack scheme because "local vulnerability" refers to the remote side and
vice versa.

There is no temporary workaround for this bug. If you comply to the
following two conditions, the impact of the error is considerably small:
1) You only connect to hosts that you consider fully trusted and
not compromised.
2) The users that connect to your servers are fully trusted (the
users have root access, for instance).


As a permanent solution, we recommend to update the openssh package to
the version that is being offered for download on our servers.

Please download the update package for your distribution and verify its
integrity by the methods listed in section 3) of this announcement.
Please note that the packages for SuSE Linux 6.4 and 7.0 are located
on the German ftp server ftp.suse.de. The SuSE Linux releases 7.1 and
newer have their openssh packages on ftp.suse.com.
Then, install the package using the command "rpm -Fhv file.rpm" to apply
the update.
Our maintenance customers are being notified individually. The packages
are being offered to install from the maintenance web.

SPECIAL INSTALL INSTRUCTIONS:
==============================
After applying the update, the secure shell daemon should be restarted
for the update to become effective. To do this, execute the following
command as root:
rcsshd restart
If you do not run a secure shell daemon, the command above is obsolete.
The secure shell daemon (sshd) is activated by default on most SuSE
products.




i386 Intel Platform:

SuSE-7.3

ftp://ftp.suse.com/pub/suse/i386/update/7.3/sec1/openssh-2.9.9p2-98.i386.rpm
21c6183843ab1a6b23bd5f820a32d564
source rpm:
ftp://ftp.suse.com/pub/suse/i386/update/7.3/zq1/openssh-2.9.9p2-98.src.rpm
566cd2c52235b872bf62ffce260c3237

SuSE-7.2

ftp://ftp.suse.com/pub/suse/i386/update/7.2/sec1/openssh-2.9.9p2-96.i386.rpm
a2a21af13f0bac95f87a683cc7199fad
source rpm:
ftp://ftp.suse.com/pub/suse/i386/update/7.2/zq1/openssh-2.9.9p2-96.src.rpm
6e5ff91227e795dc903b545f1691aaba

SuSE-7.1

ftp://ftp.suse.com/pub/suse/i386/update/7.1/sec1/openssh-2.9.9p2-98.i386.rpm
8cc626ac19a0a807d6b35790f0706af1
source rpm:
ftp://ftp.suse.com/pub/suse/i386/update/7.1/zq1/openssh-2.9.9p2-98.src.rpm
60823aaaece46cbddb884856c48214e1

SuSE-7.0
ftp://ftp.suse.de/pub/suse/i386/update/7.0/sec1/openssh-2.9.9p2-97.i386.rpm
d83d4b1f4cd83c0b6d749f2c3375a1b6
source rpm:
ftp://ftp.suse.de/pub/suse/i386/update/7.0/zq1/openssh-2.9.9p2-97.src.rpm
61cebfe1223c564826dcbb04f04090a5

SuSE-6.4
ftp://ftp.suse.de/pub/suse/i386/update/6.4/sec1/openssh-2.9.9p2-94.i386.rpm
9143ebef0b74a55fcb7220570cbbd5fe
source rpm:
ftp://ftp.suse.de/pub/suse/i386/update/6.4/zq1/openssh-2.9.9p2-94.src.rpm
002685e3ed9e3f26aa3410d433a801a0





Sparc Platform:

SuSE-7.3

ftp://ftp.suse.com/pub/suse/sparc/update/7.3/sec1/openssh-2.9.9p2-36.sparc.rpm
d8e2819c511a58e6fe02e4dcfe4aa73a
source rpm:
ftp://ftp.suse.com/pub/suse/sparc/update/7.3/zq1/openssh-2.9.9p2-36.src.rpm
ffb28fc074984c25aab75a227b9cf813

SuSE-7.1

ftp://ftp.suse.com/pub/suse/sparc/update/7.1/sec1/openssh-2.9.9p2-36.sparc.rpm
c50b9c170b6b734e15285af8fc718fd7
source rpm:
ftp://ftp.suse.com/pub/suse/sparc/update/7.1/zq1/openssh-2.9.9p2-36.src.rpm
5cf9ca6a8817399168a730bedca30667

SuSE-7.0

ftp://ftp.suse.de/pub/suse/sparc/update/7.0/sec1/openssh-2.9.9p2-36.sparc.rpm
d066f6898ed32dee71056a6d1a8be232
source rpm:
ftp://ftp.suse.de/pub/suse/sparc/update/7.0/zq1/openssh-2.9.9p2-36.src.rpm
bbacf2fbe5a776fe0324137a727e50ac





AXP Alpha Platform:

SuSE-7.1

ftp://ftp.suse.com/pub/suse/axp/update/7.1/sec1/openssh-2.9.9p2-39.alpha.rpm
b452ee9f9895fa3e6cf4faaa90ae95b4
source rpm:
ftp://ftp.suse.com/pub/suse/axp/update/7.1/zq1/openssh-2.9.9p2-39.src.rpm
7206777180ee646ecb80d788bf2162b4

SuSE-7.0
ftp://ftp.suse.de/pub/suse/axp/update/7.0/sec1/openssh-2.9.9p2-38.alpha.rpm
4c9c6648961be0143f1e916d1d341a22
source rpm:
ftp://ftp.suse.de/pub/suse/axp/update/7.0/zq1/openssh-2.9.9p2-38.src.rpm
b91b0ccd84e3d687e443157fe965a692

SuSE-6.4
ftp://ftp.suse.de/pub/suse/axp/update/6.4/sec1/openssh-2.9.9p2-37.alpha.rpm
c611ef5467d99739346a4c3952bc4f5f
source rpm:
ftp://ftp.suse.de/pub/suse/axp/update/6.4/zq1/openssh-2.9.9p2-37.src.rpm
10ca72afe81285d7ae2b70789091e024





PPC Power PC Platform:

SuSE-7.3
ftp://ftp.suse.com/pub/suse/ppc/update/7.3/sec1/openssh-2.9.9p2-69.ppc.rpm
5eb3b1cf92f25d85389d40878777a3ea
source rpm:
ftp://ftp.suse.com/pub/suse/ppc/update/7.3/zq1/openssh-2.9.9p2-69.src.rpm
172e3720f9a4146513c59b57a0232048

SuSE-7.1
ftp://ftp.suse.com/pub/suse/ppc/update/7.1/sec1/openssh-2.9.9p2-69.ppc.rpm
b1a2fa0bbecc721ec847ed81a0dc99c4
source rpm:
ftp://ftp.suse.com/pub/suse/ppc/update/7.1/zq1/openssh-2.9.9p2-69.src.rpm
748ff97c3c08d6a912b89df84da79b42

SuSE-7.0
ftp://ftp.suse.de/pub/suse/ppc/update/7.0/sec1/openssh-2.9.9p2-68.ppc.rpm
6c36b2ab8e38befc5ee9ff44ac1a666b
source rpm:
ftp://ftp.suse.de/pub/suse/ppc/update/7.0/zq1/openssh-2.9.9p2-68.src.rpm
7e50623f5832d23e4d54b9409acdfdfc

SuSE-6.4
ftp://ftp.suse.de/pub/suse/ppc/update/6.4/sec1/openssh-2.9.9p2-67.ppc.rpm
4ee55305ea565867f7da0485a737ae6c
source rpm:
ftp://ftp.suse.de/pub/suse/ppc/update/6.4/zq1/openssh-2.9.9p2-67.src.rpm
27d2d33466da141dceb42a0a13c57f0c




______________________________________________________________________________

2) Pending vulnerabilities in SuSE Distributions and Workarounds:

- All kernel versions from 2.4.14 to 2.4.18-pre8 are known to have a bug
in the connection tracking module for the IRC-DCC (Internet Relay Chat
Direct Client-to-Client) protocol that would make it possible to open
arbitrary unwanted ports for expected inbound dcc connections.
SuSE are in the process of preparing update packages for this
vulnerability for administrators who have installed a kernel from
one of the update directories on ftp.suse.com. The respective update will
also cover the DoS problem in the kernel modules for the cipe tunnel
software that we reported about earlier. We will release these new kernel
packages as soon as we can assure the quality and stability that is
expected from SuSE kernel packages. As a temporary workaround, we
recommend to remove the kernel module in question with the following
command: "rm /lib/modules/*/kernel/net/ipv4/netfilter/*irc*"
In addition to removing the kernel module on your file system, you should
make sure that the kernel module is not loaded into your running kernel.
Use the command "lsmod" to view the loaded modules, and "rmmod" to remove
a loaded kernel module. In doubt, reboot your server.

The module (and the netfilter engine as a whole) are not used by default
on SuSE Linux installations. Please note that the SuSE Linux Firewall on
CD product uses a 2.2-series kernel which is not affected by this problem.


- ucd-snmpd
The UCD snmpd contains various security releated bugs.
We are currently reviewing the code and available fixes to ensure
they all get fixed. Patches will be available as soon as possible.
It is strongly recommended to filter SNMP (TCP and UDP packets
with destination of port 161) traffic.

- mod_ssl
We are currently testing update packages for the apache web server. These
packages contain the mod_ssl Secure Socket Layer apache module, which is
subject to a weakness (buffer overflow).
The availability of the update packages is a matter of hours. The
SuSE Security announcement for the apache webserver will follow very soon
after the packages have been published on our ftp server.

______________________________________________________________________________

3) standard appendix: authenticity verification, additional information

- Package authenticity verification:

SuSE update packages are available on many mirror ftp servers all over
the world. While this service is being considered valuable and important
to the free and open source software community, many users wish to be
sure about the origin of the package and its content before installing
the package. There are two verification methods that can be used
independently from each other to prove the authenticity of a downloaded
file or rpm package:
1) md5sums as provided in the (cryptographically signed) announcement.
2) using the internal gpg signatures of the rpm package.

1) execute the command
md5sum
after you downloaded the file from a SuSE ftp server or its mirrors.
Then, compare the resulting md5sum with the one that is listed in the
announcement. Since the announcement containing the checksums is
cryptographically signed (usually using the key [email protected]),
the checksums show proof of the authenticity of the package.
We disrecommend to subscribe to security lists which cause the
email message containing the announcement to be modified so that
the signature does not match after transport through the mailing
list software.
Downsides: You must be able to verify the authenticity of the
announcement in the first place. If RPM packages are being rebuilt
and a new version of a package is published on the ftp server, all
md5 sums for the files are useless.

2) rpm package signatures provide an easy way to verify the authenticity
of an rpm package. Use the command
rpm -v --checksig
to verify the signature of the package, where is the
filename of the rpm package that you have downloaded. Of course,
package authenticity verification can only target an uninstalled rpm
package file.
Prerequisites:
a) gpg is installed
b) The package is signed using a certain key. The public part of this
key must be installed by the gpg program in the directory
~/.gnupg/ under the user's home directory who performs the
signature verification (usually root). You can import the key
that is used by SuSE in rpm packages for SuSE Linux by saving
this announcement to a file ("announcement.txt") and
running the command (do "su -" to be root):
gpg --batch; gpg .

[email protected]
- SuSE's announce-only mailing list.
Only SuSE's security annoucements are sent to this list.
To subscribe, send an email to
.

For general information or the frequently asked questions (faq)
send mail to:
or
respectively.

=====================================================================
SuSE's security contact is or .
The public key is listed below.
=====================================================================
______________________________________________________________________________

The information in this advisory may be distributed or reproduced,
provided that the advisory is not modified in any way. In particular,
it is desired that the cleartext signature shows proof of the
authenticity of the text.
SuSE GmbH makes no warranties of any kind whatsoever with respect
to the information contained in this security advisory.

Type Bits/KeyID Date User ID
pub 2048R/3D25D3D9 1999-03-06 SuSE Security Team
pub 1024D/9C800ACA 2000-10-19 SuSE Package Signing Key

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Roman Drahtmüller,
SuSE Security.
- --
- -
| Roman Drahtmüller // "You don't need eyes to see, |
SuSE GmbH - Security Phone: // you need vision!"
| Nürnberg, Germany +49-911-740530 // Maxi Jazz, Faithless |
- -

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