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Home » Hacking News » SuSE-SA:2002:024-openssh


by Nikola Strahija on July 3rd, 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

SuSE Security has issued two warnings and one SuSE Security Announcement
on 25th and 26th of June concerning the vulnerabilities found in the
openssh package that is contained and installed by default on most SuSE
products. For a few days, the nature of the errors were unknown to the
public, making it difficult for distributors to provide proper solutions
against the problem. Now that details of the errors have been disclosed,
we hereby re-release SuSE Security Announcement SuSE-SA:2002:023 (openssh)
under a new announcement ID with links to a set of update packages that
represent SuSE's permanent fix for the problems found.

After closer investigation it turned out that the packages in SuSE
products were not vulnerable to the problems if the admin did not change
the configuration file of the secure shell daemon (/etc/ssh/sshd_config).
In particular, the administrator must actively have set the sshd_config
option PAMAuthenticationViaKbdInt to "yes" for the installation to become
vulnerable. Since the SuSE openssh packages are compiled without S/KEY
support, they are not vulnerable to the second bug that is triggered by
the option ChallengeResponseAuthentication if it is set to "yes" (default).
The two configuration options correspond to the two security problems
found in openssh.

Our SuSE Linux distributions have seen a version upgrade from version
2.9.9p2 to 3.3p1 on Tuesday last week. In order to provide properly
functioning packages for our products, we have decided to return to the
commonly known stable version 2.9.9p2 with the necessary patch to fix
the vulnerability for the SuSE Linux distributions 6.4 up to 7.3 and
for our server products. SuSE Linux 8.0 came with the newer version
3.0.2p1 and will therefore be upgraded to openssh-3.4p1.
We think that adding the patches to the existing versions without
a version upgrade is best-service for our customers because we can
provide a solution that we know not to break anything else.
For more information about the bugs in openssh please visit the openssh
project homepage at and read the SuSE Security
Announcements at

Please download the update package for your distribution and verify its
integrity by the methods listed in section 3) of this announcement.
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.

* For SuSE Linux 6.4 through 7.3, the now offered packages are a version
downgrade. The rpm command refuses to install the package unless you
either use the "--force --nodeps" or the "--oldpackage" commandline
option in addition to the "-Fhv" option.
* For the update package to become effective, you have to restart the
running parent ssh daemon with the following command:
rcsshd stop ; rcsshd start
If you perform the update and the daemon restart via a remote secure
shell connection, you might want to play safe by running the command
echo "rcsshd stop; rcsshd start"|at now + 3 minutes
from a root shell. If your running instance of sshd gets killed for
some reason, then your sshd will start again after three minutes.
Afterwards, make sure that remote login to your host is possible.

In addition to the usual update packages, we have started providing
"patch" packages a few days ago. The patch-rpm is an addition to the
standard rpm package that consists of the binary changes to the package
only. As such, these patch-rpm packages consume considerably less space
to save resources during download and storage.
We will officially announce the availability of this new packaging
technique at SuSE shortly.

i386 Intel Platform:
source rpm:

source rpm:

source rpm:

source rpm:

source rpm:

source rpm:

Sparc Platform:
source rpm:

source rpm:

source rpm:

AXP Alpha Platform:
source rpm:

source rpm:

source rpm:

PPC Power PC Platform:
source rpm:

source rpm:

source rpm:

source rpm:


2) Pending vulnerabilities in SuSE Distributions and Workarounds:

- We are investigating if recently found weaknesses in resolver libraries
on BSD systems affect the SuSE Linux glibc as well.

- crontab/cron
Paul Starzetz found a small bug in crontab that allows a local user to
read the contents of the (read-protected) file /var/spool/cron/deny due
to an inherited file descriptor from the crontab command that runs the
editor to change the user's crontab. We will fix this problem in future
releases, but due to the minor severity of the bug we don't provide
update packages.

- mozilla
Cross-dependencies between mozilla and other packages in SuSE Linux
products keep us from providing version upgrades for the mozilla
packages. Fixing security bugs in our packages is usually done by
adding the necessary patches to the existing version to ensure the
compatibility and consistency that is expected from our products.
In some cases (as with the mozilla package) the complexity of the
issue does not allow to add patches any more. By consequence,
security related issues in mozilla cannot be addressed.
As a service to our user community, we provide packages of newer
mozilla versions at
These packages have been verified to run fine; they are not located
in the update directory of the distribution in question because
we cannot make any claims about the compatibility with the other
packages in the product. Security-aware users are encouraged to
install the packages from the projects/ directory.

- ghostscript
RedHat released a security announcement concerning a problem in
ghostscript, which could be exploited to gain privilege of the print
server user. We are investigating whether SuSE Linux is affected.

- fetchmail
we are in the process of releasing a security update for fetchmail
that corrects a vulnerability that could be exploited by hostile
mail servers.


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
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.
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:

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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