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- ------------------------------------------------------------------------ Debian Security Advisory DSA-1603-1
[email protected] http://www.debian.org/security/ Florian Weimer
July 08, 2008
http://www.debian.org/security/faq
- ------------------------------------------------------------------------
Package : bind9
Vulnerability : DNS cache poisoning
Problem type : remote
Debian-specific: no
CVE Id(s) : CVE-2008-1447
CERT advisory : VU#800113
Dan Kaminsky discovered that properties inherent to the DNS protocol
lead to practical DNS cache poisoning attacks. Among other things,
successful attacks can lead to misdirected web traffic and email
rerouting.
This update changes Debian's BIND 9 packages to implement the
recommended countermeasure: UDP query source port randomization. This
change increases the size of the space from which an attacker has to
guess values in a backwards-compatible fashion and makes successful
attacks significantly more difficult.
Note that this security update changes BIND network behavior in a
fundamental way, and the following steps are recommended to ensure a
smooth upgrade.
1. Make sure that your network configuration is compatible with source
port randomization. If you guard your resolver with a stateless packet
filter, you may need to make sure that no non-DNS services listen on on
the 1024--65535 UDP port range and open it at the packet filter. For
instance, packet filters based on etch's Linux 2.6.18 kernel only
support stateless filtering of IPv6 packets, and are therefore pose this additional difficulty. (If you use IPv4 with iptables and ESTABLISHED
rules, networking changes are likely not required.)
2. Install the BIND 9 upgrade, using "apt-get update" followed by
"apt-get install bind9". Verify that the named process has been
restarted and answers recursive queries. (If all queries result in
timeouts, this indicates that networking changes are necessary; see the
first step.)
3. Verify that source port randomization is active. Check that the /var/log/daemon.log file does not contain messages of the following
form
named[6106]: /etc/bind/named.conf.options:28: using specific
query-source port suppresses port randomization and can be insecure.
right after the "listening on IPv6 interface" and "listening on IPv4
interface" messages logged by BIND upon startup. If these messages are present, you should remove the indicated lines from the configuration,
or replace the port numbers contained within them with "*" sign (e.g.,
replace "port 53" with "port *").
For additional certainty, use tcpdump or some other network monitoring
tool to check for varying UDP source ports. If there is a NAT device
in front of your resolver, make sure that it does not defeat the
effect of source port randomization.
4. If you cannot activate source port randomization, consider
configuring BIND 9 to forward queries to a resolver which can, possibly
over a VPN such as OpenVPN to create the necessary trusted network link.
(Use BIND's forward-only mode in this case.)
Other caching resolvers distributed by Debian (PowerDNS, MaraDNS,
Unbound) already employ source port randomization, and no updated
packages are needed. BIND 9.5 up to and including version
1:9.5.0.dfsg-4 only implements a weak form of source port
randomization and needs to be updated as well. For information on
BIND 8, see DSA-1604-1, and for the status of the libc stub resolver,
see DSA-1605-1.
The updated bind9 packages contain changes originally scheduled for
the next stable point release, including the changed IP address of L.ROOT-SERVERS.NET (Debian bug #449148).
For the stable distribution (etch), this problem has been fixed in
version 9.3.4-2etch3.
For the unstable distribution (sid), this problem will be fixed soon.
We recommend that you upgrade your bind9 package.
Upgrade instructions
- --------------------
wget url
will fetch the file for you
dpkg -i file.deb
will install the referenced file.
If you are using the apt-get package manager, use the line for
sources.list as given below:
apt-get update
will update the internal database
apt-get upgrade
will install corrected packages
You may use an automated update by adding the resources from the
footer to the proper configuration.
Debian GNU/Linux 4.0 alias etch
- -------------------------------
Debian (stable)
- ---------------
Stable updates are available for alpha, amd64, arm, hppa, i386, ia64, mips, mipsel, powerpc, s390 and sparc.
Source archives:
http://security.debian.org/pool/updates/main/b/bind9/bind9_9.3.4-2etch3.dsc
Size/MD5 checksum: 897 aeb15f8babb1e6e38367b9f19fea87da
http://security.debian.org/pool/updates/main/b/bind9/bind9_9.3.4.orig.tar.gz
Size/MD5 checksum: 4043577 198181d47c58a0a9c0265862cd5557b0
http://security.debian.org/pool/updates/main/b/bind9/bind9_9.3.4-2etch3.diff.gz
Size/MD5 checksum: 302126 521abea46b1104f2251cc398f30af303
Architecture independent packages:
http://security.debian.org/pool/updates/main/b/bind9/bind9-doc_9.3.4-2etch3_all.deb
Size/MD5 checksum: 189560 46ff778db82d2e171d292ecac93ea9b6
alpha architecture (DEC Alpha)
http://security.debian.org/pool/updates/main/b/bind9/libisccc0_9.3.4-2etch3_alpha.deb
Size/MD5 checksum: 98154 bbdbcd3d0840f5ffcf4eaddf5a8c253f
http://security.debian.org/pool/updates/main/b/bind9/libbind-dev_9.3.4-2etch3_alpha.deb
Size/MD5 checksum: 1407380 ca8995875e76a25de6f32a47f62ea876
http://security.debian.org/pool/updates/main/b/bind9/lwresd_9.3.4-2etch3_alpha.deb
Size/MD5 checksum: 226088 93100774ae6da891caf9fa27a2134cdf
http://security.debian.org/pool/updates/main/b/bind9/libisccfg1_9.3.4-2etch3_alpha.deb
Size/MD5 checksum: 112616 bca5dcca8abff15f4f9cc911f9f94818
http://security.debian.org/pool/updates/main/b/bind9/bind9_9.3.4-2etch3_alpha.deb
Size/MD5 checksum: 322286 677fdcf8e9a8c272a08ed47a79e09209
http://security.debian.org/pool/updates/main/b/bind9/libisc11_9.3.4-2etch3_alpha.deb
Size/MD5 checksum: 190084 87d64554a1cdde9f58cc850f7d5961a1
http://security.debian.org/pool/updates/main/b/bind9/libbind9-0_9.3.4-2etch3_alpha.deb
Size/MD5 checksum: 96508 48ba9fc0e884f093e95988bd4e088b9c
http://security.debian.org/pool/updates/main/b/bind9/libdns22_9.3.4-2etch3_alpha.deb
Size/MD5 checksum: 564862 7b23948d7c741d4f287698d28385ce71
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