Package: kernel
Announcement ID: SUSE-SA:2009:047
Date: Fri, 02 Oct 2009 10:00:00 +0000
Affected Products: All SUSE Linux and openSUSE products
Vulnerability Type: remote denial of service
Severity (1-10): 6
SUSE Default Package: yes
Cross-References: CVE-2008-4609
FICORA #193744
CERT VU#943657
Content of This Advisory:
1) Security Vulnerability Resolved:
TCP/IP denial of service attacks
Problem Description
2) Solution or Work-Around
3) Special Instructions and Notes
4) Pending Vulnerabilities, Solutions, and Work-Arounds:
Please see SUSE Security Summary Report.
5) Authenticity Verification and Additional Information
______________________________________________________________________________
1) Problem Description and Brief Discussion
Outpost24 AB researchers Robert E. Lee and Jack C. Louis have found
TCP/IP denial of service vulnerabilities which allow remote attackers
to allocate resources (memory and socket slots) on a targeted system
indefinitely and so may cause a denial of the services on the
attacked machine.
The attack requires the attacker to be able to establish TCP/IP
connections on the machine. If all incoming connections are blocked,
the system is not affected.
The attacks itself are exploiting specific design limitations in the
TCP/IP protocol.
The upstream Linux kernel developers decided not to release updates at
this time, so SUSE also does not plan to release updates to resolve
this issue. Refer to the Workarounds section for suggestions on
limiting the attack.
Further references and information on this issue can be found on the
CERT-FI page:
https://www.cert.fi/haavoittuvuudet/2008/tcp-vulnerabilities.html
And in a generic paper on TCP/IP denial of service attacks:
http://www.cpni.gov.uk/Docs/tn-03-09-security-assessment-TCP.pdf
SUSE wishes to thank Outpost AB and CERT-FI for reporting these issues.
2) Solution or Work-Around
As these attacks look like valid accesses to your internet facing
services generally blocking them will not be possible.
Options are to by-host limit incoming TCP/IP connections (before they
are accepted) or block out sub nets if you see attacks coming from them.
With today's botnets this will be difficult as any such blocks could
be worked around by attackers.
3) Special Instructions and Notes
Denial of service attack patterns these days are mostly flooding
using large distributed botnets.
Attackers will probably chose these more common methods instead of
this more subtle one.
______________________________________________________________________________
4) Pending Vulnerabilities, Solutions, and Work-Arounds:
See SUSE Security Summary Report.
______________________________________________________________________________
5) Authenticity Verification and Additional Information
- Announcement authenticity verification:
SUSE security announcements are published via mailing lists and on Web
sites. The authenticity and integrity of a SUSE security announcement is
guaranteed by a cryptographic signature in each announcement. All SUSE
security announcements are published with a valid signature.
To verify the signature of the announcement, save it as text into a file
and run the command
gpg --verify
replacing
announcement. The output for a valid signature looks like:
gpg: Signature made
gpg: Good signature from "SuSE Security Team
where
If the security team's key is not contained in your key ring, you can
import it from the first installation CD. To import the key, use the
command
gpg --import gpg-pubkey-3d25d3d9-36e12d04.asc
- Package authenticity verification:
SUSE update packages are available on many mirror FTP servers all over the
world. While this service is considered valuable and important to the free
and open source software community, the authenticity and the integrity of
a package needs to be verified to ensure that it has not been tampered
with.
The internal 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, replacing
filename of the RPM package downloaded. The package is unmodified if it
contains a valid signature from build@suse.de with the key ID 9C800ACA.
This key is automatically imported into the RPM database (on
RPMv4-based distributions) and the gpg key ring of 'root' during
installation. You can also find it on the first installation CD and at
the end of this announcement.
- SUSE runs two security mailing lists to which any interested party may
subscribe:
opensuse-security@opensuse.org
- General Linux and SUSE security discussion.
All SUSE security announcements are sent to this list.
To subscribe, send an e-mail to
opensuse-security-announce@opensuse.org
- SUSE's announce-only mailing list.
Only SUSE's security announcements are sent to this list.
To subscribe, send an e-mail to
=====================================================================
SUSE's security contact is
The
=====================================================================
______________________________________________________________________________
The information in this advisory may be distributed or reproduced,
provided that the advisory is not modified in any way. In particular, the
clear text signature should show proof of the authenticity of the text.
SUSE Linux Products GmbH provides 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
