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Home » Hacking News » SuSE-SA:2002:026-bind, glibc

SuSE-SA:2002:026-bind, glibc

by Nikola Strahija on July 11th, 2002 Content of this advisory: 1) security vulnerability resolved: buffer overflow in dig, host, and nslookup utilities. 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

A vulnerability has been discovered in some resolver library
functions. The affected code goes back to the resolver library
shipped as part of BIND4; code derived from it has been included
in later BIND releases as well as the GNU libc.

The bug itself is a buffer overflow that can be triggered if a
DNS server sends multiple CNAME records in a DNS response.

This bug has been fixed for the gethostbyXXX class of functions
in GNU libc in 1999. Unfortunately, there is similar code in the
getnetbyXXX functions in recent glibc implementations, and
the code is enabled by default. However, these functions are
used by very few applications only, such as ifconfig and ifuser,
which makes exploits less likely.

We will make updated glibc packages available as they have gone
through our build system, but without separate announcements.

Until glibc patches are available, we recommend that you disable
DNS lookups of network names in nsswitch.conf. Simply replace the
line containing the tag "networks:" with this line:

networks: files

In the unlikely event that you've configured any name to network
mapping via DNS, make sure you copy this information to
/etc/networks.

The resolver bug is also present in the libbind library included
in BIND. This library is used by utilities from the bindutil package.

We are therefore providing security updates for bind8 that
address this vulnerability. As communicated previously (1),
the SuSE security team is not providing fixes for BIND4 anymore.

The bind9 packages shipped by SuSE are not vulnerable.

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

Apply the updata packages (bindutil, bind8) package using

rpm -Fvh bind*.rpm

If you are running the BIND name server, you should restart the name
server process by issuing

rcnamed restart

Our maintenance customers are being notified individually. The
packages are being offered to install from the maintenance web.

References:
(1) http://www.suse.de/de/support/security/adv004_ssh.html


______________________________________________________________________________

2) Pending vulnerabilities in SuSE Distributions and Workarounds:

- There is a format string bug in the "nn" news reader that can
be exploited by a malicious NNTP server to execute arbitrary
commands within the client user's account. We will be releasing
updated packages.

______________________________________________________________________________

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 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
pub 1024D/9C800ACA 2000-10-19 SuSE Package Signing Key


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