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Sicherheit: Umgehung von Zugriffsrechten in shadow
Aktuelle Meldungen Distributionen
Name: Umgehung von Zugriffsrechten in shadow
ID: SuSE-SA:2002:017
Distribution: SUSE
Plattformen: SUSE Linux 8.0
Datum: Fr, 17. Mai 2002, 13:00
Referenzen: Keine Angabe
Applikationen: Shadow

Originalnachricht

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

______________________________________________________________________________

SuSE Security Announcement

Package: shadow/pam-modules
Announcement-ID: SuSE-SA:2002:017
Date: Thu May 16 12:00:00 MEST 2002
Affected products: 8.0
Vulnerability Type: local privilege escalation
Severity (1-10): 5
SuSE default package: yes
Other affected systems: No.

Content of this advisory:
1) security vulnerability resolved: write() disruption in shadow utils
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 shadow package contains several useful programs to maintain the
entries in the /etc/passwd and /etc/shadow files.
The SuSE Security Team discovered a vulnerability that allows local
attackers to destroy the contents of these files or to extend the group
privileges of certain users. This is possible by setting evil filesize
limits before invoking one of the programs modifying the system files.
Depening on the permissions of the system binaries this allows a local
attacker to gain root privileges in the worst case. This however is not
possible in a default installation.
The bug has been fixed by ensuring the integrity of the data written
to temporary files before moving them to the appropriate location of the
system. There is no workaround so we recommend an update in any case.
It is necessary to update the shadow package as well as the pam-modules
package in order to prevent the truncation attacks.

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.


i386 Intel Platform:

SuSE-8.0
ftp://ftp.suse.com/pub/suse/i386/update/8.0/a1/shadow-4.0.2-88.i386.rpm
a4e0d03ecf7707eb7ca1f0422cae89f1
pam-modules-2002.3.9-31.i386.rpm
70322584f014ac3e2dc2dad0beecdefb

source rpm:
ftp://ftp.suse.com/pub/suse/i386/update/8.0/zq1/shadow-4.0.2-88.src.rpm
33af2433d9a8822202e9f6ebdc6d3e2c
pam-modules-2002.3.9-31.src.rpm
1bc5bbd169ffe5c35caa0a4ce681dcc0

______________________________________________________________________________

2) Pending vulnerabilities in SuSE Distributions and Workarounds:

- leafnode
The permissions of "/etc/leafnode" have been corrected. Please
update
to the newly available packages if you use leafnode.

- xf86, xmodules, xloader
Incorrect permission checks in certain X11 functions allow local attackers
to read or write shared memory segments they should not have access to.
Corrected packages will soon be 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 Linux AG 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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--
~
~ perl self.pl
~ $_='print"\$_=\47$_\47;eval"';eval
~ krahmer@suse.de - SuSE Security Team
~



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