Class: Dnsruby::ZoneTransfer

Inherits:
Object
  • Object
show all
Defined in:
lib/dnsruby/zone_transfer.rb

Overview

This class performs zone transfers as per RFC1034 (AXFR) and RFC1995 (IXFR).

Defined Under Namespace

Classes: Delta

Instance Attribute Summary collapse

Instance Method Summary collapse

Constructor Details

#initialize ⇒ ZoneTransfer

Returns a new instance of ZoneTransfer.



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# File 'lib/dnsruby/zone_transfer.rb', line 46

def initialize
  @server=Config.new.nameserver[0]
  @transfer_type = Types.AXFR
  @klass=Classes.IN
  @port=53
  @serial=0
  @tsig = nil
  @axfr = nil
end

Instance Attribute Details

#klass ⇒ Object

The class - defaults to IN



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# File 'lib/dnsruby/zone_transfer.rb', line 25

def klass
  @klass
end

#last_tsigstate ⇒ Object (readonly)

Returns the tsigstate of the last transfer (nil if no TSIG signed transfer has occurred)



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# File 'lib/dnsruby/zone_transfer.rb', line 33

def last_tsigstate
  @last_tsigstate
end

#port ⇒ Object

The port to connect to - defaults to 53



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# File 'lib/dnsruby/zone_transfer.rb', line 27

def port
  @port
end

#serial ⇒ Object

If using IXFR, this is the SOA serial number to start the incrementals from



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# File 'lib/dnsruby/zone_transfer.rb', line 29

def serial
  @serial
end

#server ⇒ Object

The nameserver to use for the zone transfer - defaults to system config



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# File 'lib/dnsruby/zone_transfer.rb', line 21

def server
  @server
end

#transfer_type ⇒ Object

What type of transfer to do (IXFR or AXFR) - defaults to AXFR



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# File 'lib/dnsruby/zone_transfer.rb', line 23

def transfer_type
  @transfer_type
end

#tsig ⇒ Object

The TSIG record used to sign the transfer



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# File 'lib/dnsruby/zone_transfer.rb', line 31

def tsig
  @tsig
end

Instance Method Details

#compare_serial(s1, s2) ⇒ Object

Compare two serials according to RFC 1982. Return 0 if equal, -1 if s1 is bigger, 1 if s1 is smaller.



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# File 'lib/dnsruby/zone_transfer.rb', line 220

def compare_serial(s1, s2)
  if s1 == s2
    return 0
  end
  if s1 < s2 and (s2 - s1) < (2**31)
    return 1
  end
  if s1 > s2 and (s1 - s2) > (2**31)
    return 1
  end
  if s1 < s2 and (s2 - s1) > (2**31)
    return -1
  end
  if s1 > s2 and (s1 - s2) < (2**31)
    return -1
  end
  return 0
end

#do_transfer(zone, server) ⇒ Object

:nodoc: all



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# File 'lib/dnsruby/zone_transfer.rb', line 104

def do_transfer(zone, server) #:nodoc: all
  @transfer_type = Types.new(@transfer_type)
  @state = :InitialSoa
  socket = TCPSocket.new(server, @port)
  begin
    #  Send an initial query
    msg = Message.new(zone, @transfer_type, @klass)
    if @transfer_type == Types.IXFR
      rr = RR.create("#{zone} 0 IN SOA" + '0 0 %u 0 0 0 0' % @serial)
      msg.add_authority(rr)
    end
    send_message(socket, msg)

    while (@state != :End)
      response = receive_message(socket)

      if (@state == :InitialSoa)
        rcode = response.rcode
        if (rcode != RCode.NOERROR)
          if (@transfer_type == Types.IXFR &&
                rcode == RCode.NOTIMP)
            #  IXFR didn't work - let's try AXFR
            Dnsruby.log.debug("IXFR DID NOT WORK (rcode = NOTIMP) - TRYING AXFR!!")
            @state = :InitialSoa
            @transfer_type=Types.AXFR
            #  Send an initial AXFR query
            msg = Message.new(zone, @transfer_type, @klass)
            send_message(socket, msg)
            next
          end
          raise ResolvError.new(rcode.string);
        end

        if (response.question[0].qtype != @transfer_type)
          raise ResolvError.new("invalid question section")
        end

        if (response.header.ancount == 0 && @transfer_type == Types.IXFR)
          Dnsruby.log.debug("IXFR DID NOT WORK (ancount = 0) - TRYING AXFR!!")
          #  IXFR didn't work - let's try AXFR
          @transfer_type=Types.AXFR
          #  Send an initial AXFR query
          @state = :InitialSoa
          msg = Message.new(zone, @transfer_type, @klass)
          send_message(socket, msg)
          next
        end
      end

      response.each_answer { |rr|
        parseRR(rr)
      }
      if (@state == :End &&
            response.tsigstate == :Intermediate)
        raise ResolvError.new("last message must be signed")
      end
      if (@state == :End && @tsig)
        if (response.tsigstate != :Verified)
          @last_tsigstate = :Failed
          raise ResolvError.new("Zone transfer not correctly signed")
        end
        @last_tsigstate = :Verified
      end
    end
    #  This could return with an IXFR response, or an AXFR response.
    #  If it fails completely, then try to send an AXFR query.
    #  Once the query has been sent, then enter the main response loop.
    #  Unless we know we're definitely AXFR, we should be prepared for either IXFR or AXFR
    #  AXFR response : The first and the last RR of the response is the SOA record of the zone.
    #                  The whole zone is returned inbetween.
    #  IXFR response : one or more difference sequences is returned.  The list of difference
    #                  sequences is preceded and followed by a copy of the server's current
    #                  version of the SOA.
    #                  Each difference sequence represents one update to the zone (one SOA
    #                  serial change) consisting of deleted RRs and added RRs.  The first RR
    #                  of the deleted RRs is the older SOA RR and the first RR of the added
    #                  RRs is the newer SOA RR.
    socket.close
    if (@axfr!=nil)
      return @axfr
    end
    return @ixfr
  rescue Exception => e
    socket.close
    raise e
  end
end

#parseRR(rec) ⇒ Object

:nodoc: all



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# File 'lib/dnsruby/zone_transfer.rb', line 239

def parseRR(rec) #:nodoc: all
  name = rec.name
  type = rec.type
  delta = Delta.new

  case @state
  when :InitialSoa
    if (type != Types.SOA)
      raise ResolvError.new("missing initial SOA")
    end
    @initialsoa = rec
    #  Remember the serial number in the initial SOA; we need it
    #  to recognize the end of an IXFR.
    @end_serial = rec.serial
    #         if ((@transfer_type == Types.IXFR) && (@end_serial <= @serial))
    if ((@transfer_type == Types.IXFR) && (compare_serial(@end_serial, @serial) >= 0))
      Dnsruby.log.debug("zone up to date")
      raise ZoneSerialError.new("IXFR up to date: expected serial " +
          @serial.to_s + " , got " + rec.serial.to_s);
      @state = :End
    else
      @state = :FirstData
    end
  when :FirstData
    #  If the transfer begins with 1 SOA, it's an AXFR.
    #  If it begins with 2 SOAs, it's an IXFR.
    if (@transfer_type == Types.IXFR && type == Types.SOA &&
          rec.serial == @serial)
      Dnsruby.log.debug("IXFR response - using IXFR")
      @rtype = Types.IXFR
      @ixfr = []
      @state = :Ixfr_DelSoa
    else
      Dnsruby.log.debug("AXFR response - using AXFR")
      @rtype = Types.AXFR
      @transfer_type = Types.AXFR
      @axfr = []
      @axfr << @initialsoa
      @state = :Axfr
    end
    parseRR(rec) # Restart...
    return

  when :Ixfr_DelSoa
    delta = Delta.new
    @ixfr.push(delta)
    delta.start = rec.serial
    delta.deletes << rec
    @state = :Ixfr_Del

  when :Ixfr_Del
    if (type == Types.SOA)
      @current_serial = rec.serial
      @state = :Ixfr_AddSoa
      parseRR(rec); # Restart...
      return;
    end
    delta = @ixfr[@ixfr.length - 1]
    delta.deletes << rec

  when :Ixfr_AddSoa
    delta = @ixfr[@ixfr.length - 1]
    delta.end = rec.serial
    delta.adds << rec
    @state = :Ixfr_Add

  when :Ixfr_Add
    if (type == Types.SOA)
      soa_serial = rec.serial
      if (soa_serial == @end_serial)
        @state = :End
        return
      elsif (soa_serial != @current_serial)
        raise ZoneSerialError.new("IXFR out of sync: expected serial " +
            @current_serial.to_s + " , got " + soa_serial.to_s);
      else
        @state = :Ixfr_DelSoa
        parseRR(rec); # Restart...
        return;
      end
    end
    delta = @ixfr[@ixfr.length - 1]
    delta.adds << rec

  when :Axfr
    #  Old BINDs sent cross class A records for non IN classes.
    if (type == Types.A && rec.klass() != @klass)
    else
      if (type == Types.SOA)
        @state = :End
      else
        @axfr << rec
      end
    end
  when :End
    raise ResolvError.new("extra data in zone transfer")

  else
    raise ResolvError.new("invalid state for zone transfer")
  end
end

#receive_message(socket) ⇒ Object

:nodoc: all

Raises:



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# File 'lib/dnsruby/zone_transfer.rb', line 361

def receive_message(socket) #:nodoc: all
  buf = tcp_read(socket, 2)
  answersize = buf.unpack('n')[0]
  #  Some servers (e.g. dnscache) apparently hang up on some connections.
  #  Thanks to Matt Palmer for the fix.
  raise ResolvError.new("Server did not send a valid answer") if answersize.nil?
  buf = tcp_read(socket, answersize)
  msg = Message.decode(buf)
  if (@tsig)
    if !@tsig.verify_envelope(msg, buf)
      Dnsruby.log.error("Bad signature on zone transfer - closing connection")
      raise ResolvError.new("Bad signature on zone transfer")
    end
  end
  return msg
end

#send_message(socket, msg) ⇒ Object

:nodoc: all



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# File 'lib/dnsruby/zone_transfer.rb', line 342

def send_message(socket, msg) #:nodoc: all
  if (@tsig)
    @tsig.apply(msg)
    @tsig = msg.tsig
  end
  query_packet = msg.encode
  lenmsg = [query_packet.length].pack('n')
  socket.send(lenmsg, 0)
  socket.send(query_packet, 0)
end

#tcp_read(socket, len) ⇒ Object

:nodoc: all



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# File 'lib/dnsruby/zone_transfer.rb', line 353

def tcp_read(socket, len) #:nodoc: all
  buf=""
  while (buf.length < len) and not socket.eof? do
    buf += socket.read(len-buf.length)
  end
  return buf
end

#transfer(zone) ⇒ Object

Perform a zone transfer (RFC1995)

If an IXFR query is unsuccessful, then AXFR is tried (and @transfer_type is set
to AXFR)
TCP is used as the only transport

If AXFR is performed, then the zone will be returned as a set of records :

      zt = Dnsruby::ZoneTransfer.new
      zt.transfer_type = Dnsruby::Types.AXFR
      zt.server = "ns0.validation-test-servers.nominet.org.uk"
      zone = zt.transfer("validation-test-servers.nominet.org.uk")
      soa = zone[0]
      rec1 = zone[1]
      print zone.to_s

If IXFR is performed, then the incrementals will be returned as a set of Deltas.
Each Delta contains the start and end SOA serial number, as well as an array of
adds and deletes that occurred between the start and end.

       zt = Dnsruby::ZoneTransfer.new
       zt.transfer_type = Dnsruby::Types.IXFR
       zt.server = "ns0.validation-test-servers.nominet.org.uk"
       zt.serial = 2007090401
       deltas = zt.transfer("validation-test-servers.nominet.org.uk")
       assert_equal("Should show up in transfer", deltas[0].adds[1].data)



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# File 'lib/dnsruby/zone_transfer.rb', line 82

def transfer(zone)
  servers = @server
  if (servers.class == String)
    servers=[servers]
  end
  xfr = nil
  exception = nil
  servers.each do |server|
    begin
      server=Config.resolve_server(server)
      xfr = do_transfer(zone, server)
      break
    rescue Exception => e
      exception = e
    end
  end
  if (xfr == nil && exception != nil)
    raise exception
  end
  return xfr
end