SuSE: UPDATE: 'openssh' Privilege escalation vulnerability
Summary
______________________________________________________________________________
SuSE Security Announcement
Package: openssh
Announcement-ID: SuSE-SA:2001:045
Date: Thursday, Dec 6th 2001 21:30 MET
Affected SuSE versions: 6.4, 7.0, 7.1, 7.2, 7.3
Vulnerability Type: local privilege escalation
Severity (1-10): 5
SuSE default package: yes
Other affected systems: systems running openssh
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) Re-release of SuSE Security Announcement SuSE-SA:2001:044, brief history,
Clarification, new problem fixed, upgrade information.
This is a re-release of the SuSE Security Announcement SuSE-SA:2001:044,
adding another bugfix for the openssh package as well as more detailed
information about the vulnerabilities to prevent misunderstandings.
The currently supported SuSE distributions 6.4 and newer come with two
implementations of the secure shell protocol: The package names are
"ssh" and "openssh".
Brief history:
In 1998, a vulnerability of the secure shell protocol in version 1 has
been discovered and named "crc32 compensation attack". The vulnerability
allows an attacker to insert arbitrary sequences into the ssh-1 protocol
layer. At that time, an added patch fixed the problem in the ssh
implementation (visible in the client-side verbose output of the ssh
command (-v): "Installing crc compensation attack detector.").
In early 2001, Michal Zalewski discovered that the widely used patch
was defective and opened another security hole which is being actively
exploited today. SuSE Security announcement SuSE-SA:2001:004, published
February 16th 2001, available at *[1], addresses this defective patch,
among other issues.
Clarification/Apology:
Our last openssh security announcement SuSE-SA:2001:044 (*[3]) may falsely
lead to assume that the openssh-2.9.9p2 update packages on our ftp
server fix the vulnerabilities known as crc32 compensation attack.
This is incorrect since the openssh-2.3.0 packages released with SuSE
Security announcement SuSE-SA:2000:047 in November 2000, available at
*[2], already fixed the mentioned (among other) problems. The release
of the openssh-2.9.9p2 update packages obsoletes the openssh-2.3.0 update
packages.
We explicitly regret the used wording and apologize to the openssh
development team, in particular Markus Friedl and Theo De Raadt, and
thank them for their excellent work on the project.
Scanning utilities that can be found on the internet connect to port 22
of a server and read the version string. It should be noted that the bare
knowlege of the secure shell protocol version string does not allow to
determine whether a running secure shell daemon is actually vulnerable
to the defective fix for the crc32 compensation attack.
SuSE security receive dozens of requests about statements if the daemons
in use are vulnerable or not. Please see reference *[1].
New problem fixed:
This re-release of SuSE Security Announcement SuSE-SA:2001:044 (please
see reference *[3] below) adds another patch to the openssh-2.9.9p2
packages: A bug allows a local attacker on the server to specify
environment variables that can influence the login process if the
"UseLogin" configuration option on the server side is set to "yes".
If exploited, the local attacker on the secure shell server can execute
arbitrary commands as root.
In the default configuration of the package, the UseLogin option is set
to "no", which means that the administrator of the server must have set
the option to "yes" manually before the bug can be exploited.
Users who upgraded their SuSE openssh package before December 6th 2001
should upgrade their package again. Use the command "rpm -q openssh"
to see which version/release of the package you have installed, and
compare this version with the one as listed below.
Upgrade information:
You can find out which implementation of the ssh protocol you are using
with the command "rpm -qf /usr/bin/ssh".
If you use the ssh-1.2.* package, please read Reference *[1].
If you use the openssh-* package, please download the rpm package for
your distribution from the URL list below, verify its integrity using
the methods as described in section 3) of this security announcement
and install the package using the command
rpm -Uhv file.rpm
where file.rpm is the filename of the package that you have downloaded.
References:
*[1]: SUSE – Open-Source-Lösungen für Enterprise Server und Cloud | SUSE
*[2]: SUSE – Open-Source-Lösungen für Enterprise Server und Cloud | SUSE
*[3]: SUSE – Open-Source-Lösungen für Enterprise Server und Cloud | SUSE
SPECIAL INSTALL INSTRUCTIONS:
The sshd secure shell daemon on the server side has to be restarted for
the new package to become active. If you are logged on on the console,
the simple command "rcsshd restart" should do this for you.
If you are logged on via secure shell, you should make sure that you
do not terminate the connections that are established through the running
secure shell daemon/its children. In this case, kill the daemon after
package installation using the command
kill -TERM `cat /var/run/sshd.pid`
and then restart the daemon with the command
/usr/sbin/sshd
as root.
Then, verify that the login procedure works as before. One of the main
changes in the new openssh package is that the file
$HOME/.ssh/authorized_keys2 is only read by the server if the file
$HOME/.ssh/authorized_keys does not exist and if protocol version 2 is
being used. The file $HOME/.ssh/authorized_keys2 can be removed after
its contents have been added to $HOME/.ssh/authorized_keys.
The two configuration files /etc/ssh/sshd_config (server side) and
/etc/ssh/ssh_config (client side) contained in the openssh package
do not get overwritten upon installation or upgrade, if you have changed
them manually. Instead, the new configuration files are written with a
.rpmnew suffix. The defaults as provided in the SuSE package make an
effort to establish both convenience as well as security.
NOTE: Packages for SuSE Linux distributions 7.0 and older containing
cryptographic software are located on our German ftp server ftp.suse.de
for legal reasons. Packages for all other distributions (7.1 and newer)
can be found at their regular path at ftp.suse.com.
i386 Intel Platform:
SuSE-7.3
f3d60cce6d62dbf79c36a849811c19d7
source rpm:
4246e40b1e5a7b4456f2bb4c05177126
SuSE-7.2
3764a15b17b0823c6fa2e8e4aee5af69
source rpm:
e9cccadf767cb80e3c588266d6886153
SuSE-7.1
4dbcdb2a544cadd36749baea890bc38e
source rpm:
04400597a1b9526bc78344e8e523fa40
SuSE-7.0
29dcc882bf30cbe88c94b07bb84e7216
source rpm:
b852431e4711d7f45a8bd180532325b0
SuSE-6.4
8cfe1e9d2dd964851acb42e1e13311b9
source rpm:
a3686e39258d03c99fc2ba3573325c2a
Sparc Platform:
SuSE-7.3
32d3a1c735d2c27cb580fedeeed3a135
source rpm:
82540b2297b2d03d45118b3c23a72bf8
SuSE-7.1
The update packages for the SuSE Linux 7.1 Sparc distributions are not
available yet. The package can soon be found at
SuSE-7.0
638891762f09e01b83e9c39c184ce9ea
source rpm:
ad3520ad8907c585f84facb742fc03bf
AXP Alpha Platform:
SuSE-7.1
04e815054c9bc3a1b0a1ddda8c6e2d10
source rpm:
32c39e29517fc8269f252f7cc6f18bce
The update packages for the SuSE Linux AXP/Alpha distributions before
SuSE-7.1 are not available on our ftp server yet. These packages can be
found at the usual location in the update paths on ftp.suse.de.
PPC Power PC Platform:
SuSE-7.3
4b056c828675898bf482e9ecb4f91a0b
source rpm:
e10ed49e7319c244caf324a64f16c738
SuSE-7.1
163126a80ff0167b34c041348ef5c3c4
source rpm:
948862c53dc62e921b03766c986a4de2
SuSE-7.0
aff3785ac9670daa0e06445ad9b5a2b9
source rpm:
ccfb132470cb61b52688fc12f1352b12
SuSE-6.4
ae20b7379474735126636aed05f6eeee
source rpm:
2351d7667c02a1ad33e21bd39196cf0a
______________________________________________________________________________
2) Pending vulnerabilities in SuSE Distributions and Workarounds:
- We are currently testing kernel update packages for the recently
found local security flaw in the ELF binary loader in the Linux
kernel of all v2.4 versions and expect to be able to announce these
update rpm packages soon with a re-release of our kernel security
announcement.
______________________________________________________________________________
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
References
