SUSE Security Announcement: Live CD 9.1 (SuSE-SA:2004:011)

2004-05-07T00:00:00
ID SECURITYVULNS:DOC:6180
Type securityvulns
Reporter Securityvulns
Modified 2004-05-07T00:00:00

Description

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


                    SuSE Security Announcement

    Package:                Live CD 9.1
    Announcement-ID:        SuSE-SA:2004:011
    Date:                   Thursday, May 6th 2004 22:30 MEST
    Affected products:      SUSE LINUX 9.1 Personal Edition Live CD
    Vulnerability Type:     remote root access
    Severity (1-10):        8
    SuSE default package:   yes
    Other affected systems: none

Content of this advisory:
    1) security vulnerability resolved: Live CD 9.1
       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

The freshly released SUSE LINUX 9.1 comes in two variants: 
* SUSE LINUX 9.1 Professional (5 CD-ROMs, 2 double sided DVDs, printed
  manuals, for Intel i386 32Bit platform and 1 DVD for the AMD 64Bit
  platform)
* SUSE LINUX 9.1 Personal (2 CD-ROMs: 1 installable CD-ROM, 1 Live CD-ROM
  for running SUSE LINUX on your PC without actually installing the
  system.)

This SUSE Security Announcement targets the Live CD that comes with the
SUSE LINUX 9.1 Personal edition. The Live CD can boot and run on any PC
that has a CD-ROM drive, offering a convenient opportunity for users
who want to try out SUSE Linux without any modification to the system
that is installed on the computer. Similar CD-ROM iso images have been
available for download from our ftp server with each release of the 
SUSE LINUX home user product for years.
Upon boot, the Live CD will automatically configure a network card if 
one has been detected. It requires user interaction for dialup 
network access.

A configuration error on the Live CD allows for a passwordless, remote 
root login to the system via ssh, if the computer has booted from the 
Live CD and if it is connected to a network. Since the CD-ROM is a 
read-only medium by definition, there is no solution for this error 
that would be persistent over a reboot from the Live CD. Manually 
killing all running instances of the secure shell daemon ("killall 
sshd" as root) after each boot cures the problem, while still exposing 
the vulnerability in the time window between startup and the killing 
of the sshd process.

It is a policy for a fresh install of SUSE LINUX products to enable 
the user to log on to the system using secure shell (ssh). During the 
installation of the system, the user is prompted for a root password.
The Live CD does not install any system on a medium and therefore does 
not ask for a root password. By consequence, passwordless logins 
should be denied on the system, regardless of whether the account in 
question is the super user account or not. The Live CD 9.1 suffers 
from this misconfiguration.
Our permanent fix for the vulnerability is to download the iso image 
of the fixed Live CD 9.1 from the URL as listed below and to burn it 
on a CD-R using a CD-burner and the software that comes with the SUSE 
LINUX 9.1 Personal or Professional (cdrecord, k3b). The new image 
still runs a secure shell daemon for remote login, but it does not 
allow remote logins on a zero-length password account, and it denies
remote root login attempts, independently from the password.

We thank Patrick Kranefeld and Fabian Franz who have reported the 
configuration neglectfulness on the SUSE LINUX 9.1 Live CD to SUSE 
Security.

Image authenticity verification:
The file LiveCD-9.1-01.iso has a length of 706349056 bytes. If you run 
the command "md5sum LiveCD-9.1-01.iso" after you have downloaded the 
file, the md5sum command should print the following md5sum:

    9f4ed1bc6b3ee582bf593fde75d5db43

This md5 sum is also contained in the file MD5SUMS in the same 
directory as the LiveCD-9.1-01.iso file. Its signature (by 
security@suse.de) is contained in the file MD5SUMS.sig.

The download location:

ftp://ftp.suse.com/pub/suse/i386/live-cd-9.1/LiveCD-9.1-01.iso
  9f4ed1bc6b3ee582bf593fde75d5db43

A note: Please use a mirror for downloading the SUSE LINUX 9.1 Live 
CD. Mirrors close to you can be found at 
http://www.suse.com/us/private/download/ftp/int_mirrors.html

2) Pending vulnerabilities in SuSE Distributions and Workarounds:

- canna
New canna packages are available on our ftp servers, fixing tmp race
conditions.

- xchat
A buffer overflow in the SOCKS5 code of the XChat program has been
fixed. New packages are available on our ftp servers.

- tcpdump
The tcpdump program contained a remote DoS condition in its ISAKMP
packet handling (CAN-2004-0183 and CAN-2004-0184).
Fixed packages are available on our ftp servers.

- lha
A buffer overflow in the header parsing routines of lha has been fixed.
Additionally lha did not properly handle pathnames within archives
(CAN-2004-0234 and CAN-2004-0235).
Fixed packages are available on our ftp 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 md5sum <name-of-the-file.rpm> 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 security@suse.de), 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 <file.rpm> to verify the signature of the package, where <file.rpm> 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 < announcement.txt | gpg --import SuSE Linux distributions version 7.1 and thereafter install the key "build@suse.de" upon installation or upgrade, provided that the package gpg is installed. The file containing the public key is placed at the toplevel directory of the first CD (pubring.gpg) and at ftp://ftp.suse.com/pub/suse/pubring.gpg-build.suse.de .

  • SuSE runs two security mailing lists to which any interested party may subscribe:

    suse-security@suse.com - general/linux/SuSE security discussion. All SuSE security announcements are sent to this list. To subscribe, send an email to <suse-security-subscribe@suse.com>.

    suse-security-announce@suse.com - SuSE's announce-only mailing list. Only SuSE's security annoucements are sent to this list. To subscribe, send an email to <suse-security-announce-subscribe@suse.com>.

    For general information or the frequently asked questions (faq) send mail to: <suse-security-info@suse.com> or <suse-security-faq@suse.com> respectively.

    ===================================================================== SuSE's security contact is <security@suse.com> or <security@suse.de>. The <security@suse.de> 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 <security@suse.de> pub 1024D/9C800ACA 2000-10-19 SuSE Package Signing Key <build@suse.de>

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Roman Drahtmüller, SuSE Security.


  • - | Roman Drahtmüller <draht@suse.de> // "You don't need eyes to see, | SuSE Linux AG - Security Phone: // you need vision!" | Nürnberg, Germany +49-911-740530 // Maxi Jazz, Faithless |
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