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Sigurnosni propust programskog paketa ntp

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______________________________________________________________________________

SUSE Security Announcement

Package: ntp
Announcement-ID: SUSE-SA:2014:001
Date: Monday, Jan 20 15:13:37 CET 2014
Affected products: all NTP server installations
Vulnerability Type: DDoS reflection attacks
Severity (1-10): 7
SUSE default package: no
Cross References: CVE-2013-5211

Content of this advisory:
1) security vulnerability resolved:
– DDoS reflection attacks in ntpd
problem description
2) solution/workaround
3) special instructions and notes
4) package location and checksums
5) pending vulnerabilities, solutions, workarounds:
– none
6) standard appendix (further information)

______________________________________________________________________________

1) problem description, brief discussion

The “monlist” command of the NTP protocol is currently abused in a DDoS
reflection attack. This is done by spoofing packets from addresses to which
the attack is directed to. The ntp installations itself are not target of
the attack, but they are part of the DDoS network which the attacker is
driving. It is therefore necessary to restrict ntp configurations to not
answer spoofed “monlist” requests. It is not necessary to update the ntp
software itself.

Additional information can be found here:

https://www.cert-bund.de/advisoryshort/CB-K14-0020%20UPDATE%202
http://www.kb.cert.org/vuls/id/348126

A more comprehensive description on how you can secure your
infrastructure against NTP DDoS reflection attacks can be found here:

http://www.team-cymru.org/ReadingRoom/Templates/secure-ntp-template.html

2) solution/workaround

To ensure that your ntpd installation can not participate in a DDoS attack,
add the following line to your configuration:

restrict default noquery

3) special instructions and notes

After applying the configuration changes, restart the ntp daemon.

4) package location and checksums

not applicable

______________________________________________________________________________

5) Pending vulnerabilities in SUSE Distributions and Workarounds:

none

______________________________________________________________________________

6) 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 recommend against subscribing to security lists that cause the
e-mail 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
file name 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 top-level 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 announcements 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 clear-text 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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