SuSE Inc. Information for VU#542971

Multiple vendors' Domain Name System (DNS) stub resolvers vulnerable to buffer overflow via network name and address lookups

Status

Affected

Vendor Statement

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

______________________________________________________________________________

                        SuSE Security Announcement

        Package:                bind, glibc
       Announcement-ID:        SuSE-SA:2002:026
       Date:                   Tue Jul 09 2002
       Affected products:      7.0, 7.1, 7.2, 7.3, 8.0
SuSE Linux Enterprise Server for S/390,
SuSE Linux Database Server,
SuSE eMail Server III,
SuSE Linux Enterprise Server,
SuSE Linux Firewall on CD
       Vulnerability Type:     buffer overflow
       Severity (1-10):        3
       SuSE default package:   yes
Cross References: CERT CA-2002-19; CVE CAN-2002-0651

    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 <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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Vendor Information

The vendor has not provided us with any further information regarding this vulnerability.

Vendor References

None

Addendum

The CERT/CC has no additional comments at this time.

If you have feedback, comments, or additional information about this vulnerability, please send us email.