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Home » Hacking News » SuSE-SA:2002:019-dhcp/dhcp-server

SuSE-SA:2002:019-dhcp/dhcp-server

by Nikola Strahija on May 22nd, 2002 Content of this advisory: 1) security vulnerability resolved: format string bug in dynamic DNS code 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 "Dynamic Host Configuration Protocol" (DHCP) server from the Internet
Software Consortium allows hosts on a TCP/IP network to request and be
assigned IP addresses, and also to discover information about the network
to which they are attached.

A remote exploitable format string vulnerability was found in the logging
routines of the dynamic DNS code of dhcpd. This vulnerability allows an
attacker, usually within the LAN served by the DHCP server, to get remote
root access to the host running dhcpd.

The dhcp/dhcp-server package is not installed by default nor is the
dynamic DNS feature enabled by default.
As temporary workaround the dynamic DNS feature could be disabled via
dhcpd's config file with the following lines:
ddns-update-style none;
ddns-updates off;
After updating the package or modifying the config file you have to run:
rcdhcpd restart
as root to restart all instances of running dhcpd processes.

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/n2/dhcp-server-3.0.1rc6-8.i386.rpm
754569c059f5f2c4f71397f6c6498f53
source rpm:
ftp://ftp.suse.com/pub/suse/i386/update/8.0/zq1/dhcp-3.0.1rc6-8.src.rpm
82ab4455ae86a932a746778ca0cf06f1

SuSE-7.3
ftp://ftp.suse.com/pub/suse/i386/update/7.3/n2/dhcp-3.0rc12-47.i386.rpm
58bdf5e4e0622ba280fad0d649a36bdd
source rpm:
ftp://ftp.suse.com/pub/suse/i386/update/7.3/zq1/dhcp-3.0rc12-47.src.rpm
20abdc3bad4810971aa4cc959c133a9e

SuSE-7.2
ftp://ftp.suse.com/pub/suse/i386/update/7.2/n2/dhcp-3.0rc4-27.i386.rpm
826ffc2524ad6a6b3b746e3c5e0e5413
source rpm:
ftp://ftp.suse.com/pub/suse/i386/update/7.2/zq1/dhcp-3.0rc4-27.src.rpm
7bfd527698beef5a83e60577e7e02cfb



Sparc Platform:

SuSE-7.3
ftp://ftp.suse.com/pub/suse/sparc/update/7.3/n2/dhcp-3.0rc12-22.sparc.rpm
15ec49d27e7f8b61ec22616484e43996
source rpm:
ftp://ftp.suse.com/pub/suse/sparc/update/7.3/zq1/dhcp-3.0rc12-22.src.rpm
1e3f0ee6da5684a49b31908f0e6ac9dd



PPC Power PC Platform:

SuSE-7.3
ftp://ftp.suse.com/pub/suse/ppc/update/7.3/n2/dhcp-3.0rc12-32.ppc.rpm
76914c072100dff6fdf781ed81f7afeb
source rpm:
ftp://ftp.suse.com/pub/suse/ppc/update/7.3/zq1/dhcp-3.0rc12-32.src.rpm
9ac78f35a529c24315f11184555c7f81



______________________________________________________________________________

2) Pending vulnerabilities in SuSE Distributions and Workarounds:

- tcpdump/libpcap
Various security and non-security related bugs were found in the code
of tcpdump and libpcap. New RPMs are currently being build.


______________________________________________________________________________

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

- -----BEGIN PGP PUBLIC KEY BLOCK-----
Version: GnuPG v1.0.6 (GNU/Linux)
Comment: For info see http://www.gnupg.org


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