408 lines
12 KiB
Ruby
408 lines
12 KiB
Ruby
# -*- coding: binary -*-
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#
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# $Id: RR.rb,v 1.19 2006/07/28 07:33:36 bluemonk Exp $
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#
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require 'net/dns/names/names'
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require 'net/dns/rr/types'
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require 'net/dns/rr/classes'
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%w[a ns mx cname txt soa ptr aaaa mr srv].each do |file|
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require "net/dns/rr/#{file}"
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end
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module Net # :nodoc:
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module DNS
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# =Name
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#
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# Net::DNS::RR - DNS Resource Record class
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#
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# =Synopsis
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#
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# require 'net/dns/rr'
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#
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# =Description
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#
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# The Net::DNS::RR is the base class for DNS Resource
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# Record (RR) objects. A RR is a pack of data that represents
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# resources for a DNS zone. The form in which this data is
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# shows can be drawed as follow:
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#
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# "name ttl class type data"
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#
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# The +name+ is the name of the resource, like an canonical
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# name for an +A+ record (internet ip address). The +ttl+ is the
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# time to live, expressed in seconds. +type+ and +class+ are
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# respectively the type of resource (+A+ for ip addresses, +NS+
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# for nameservers, and so on) and the class, which is almost
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# always +IN+, the Internet class. At the end, +data+ is the
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# value associated to the name for that particular type of
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# resource record. An example:
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#
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# # A record for IP address
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# "www.example.com 86400 IN A 172.16.100.1"
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#
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# # NS record for name server
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# "www.example.com 86400 IN NS ns.example.com"
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#
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# A new RR object can be created in 2 ways: passing a string
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# such the ones above, or specifying each field as the pair
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# of an hash. See the Net::DNS::RR.new method for details.
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#
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# =Error classes
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#
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# Some error classes has been defined for the Net::DNS::RR class,
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# which are listed here to keep a light and browsable main documentation.
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# We have:
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#
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# * RRArgumentError: Generic argument error for class Net::DNS::RR
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# * RRDataError: Error in parsing binary data, maybe from a malformed packet
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#
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# =Copyright
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#
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# Copyright (c) 2006 Marco Ceresa
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#
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# All rights reserved. This program is free software; you may redistribute
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# it and/or modify it under the same terms as Ruby itself.
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#
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class RR
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include Net::DNS::Names
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# Regexp matching an RR string
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RR_REGEXP = Regexp.new("^\\s*(\\S+)\\s*(\\d+)?\\s+(" +
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Net::DNS::RR::Classes.regexp +
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"|CLASS\\d+)?\\s*(" +
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Net::DNS::RR::Types.regexp +
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"|TYPE\\d+)?\\s*(.*)$", Regexp::IGNORECASE, 'n')
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# Dimension of the sum of class, type, TTL and rdlength fields in a
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# RR portion of the packet, in bytes
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RRFIXEDSZ = 10
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# Name of the RR
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attr_reader :name
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# TTL time (in seconds) of the RR
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attr_reader :ttl
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# Data belonging to that appropriate class,
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# not to be used (use real accessors instead)
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attr_reader :rdata
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# Create a new instance of Net::DNS::RR class, or an instance of
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# any of the subclass of the appropriate type.
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#
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# Argument can be a string or an hash. With a sting, we can pass
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# a RR resource record in the canonical format:
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#
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# a = Net::DNS::RR.new("foo.example.com. 86400 A 10.1.2.3")
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# mx = Net::DNS::RR.new("example.com. 7200 MX 10 mailhost.example.com.")
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# cname = Net::DNS::RR.new("www.example.com 300 IN CNAME www1.example.com")
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# txt = Net::DNS::RR.new('baz.example.com 3600 HS TXT "text record"')
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#
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# Incidentally, +a+, +mx+, +cname+ and +txt+ objects will be instances of
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# respectively Net::DNS::RR::A, Net::DNS::RR::MX, Net::DNS::RR::CNAME and
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# Net::DNS::RR::TXT classes.
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#
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# The name and RR data are required; all other informations are optional.
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# If omitted, the +TTL+ defaults to 10800, +type+ default to +A+ and the RR class
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# defaults to +IN+. Omitting the optional fields is useful for creating the
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# empty RDATA sections required for certain dynamic update operations.
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# All names must be fully qualified. The trailing dot (.) is optional.
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#
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# The preferred method is however passing an hash with keys and values:
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#
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# rr = Net::DNS::RR.new(
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# :name => "foo.example.com",
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# :ttl => 86400,
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# :cls => "IN",
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# :type => "A",
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# :address => "10.1.2.3"
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# )
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#
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# rr = Net::DNS::RR.new(
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# :name => "foo.example.com",
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# :rdata => "10.1.2.3"
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# )
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#
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# Name and data are required; all the others fields are optionals like
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# we've seen before. The data field can be specified either with the
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# right name of the resource (+:address+ in the example above) or with
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# the generic key +:rdata+. Consult documentation to find the exact name
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# for the resource in each subclass.
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#
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def initialize(arg)
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case arg
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when String
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instance = new_from_string(arg)
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when Hash
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instance = new_from_hash(arg)
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else
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raise RRArgumentError, "Invalid argument, must be a RR string or an hash of values"
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end
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if @type.to_s == "ANY"
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@cls = Net::DNS::RR::Classes.new("IN")
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end
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build_pack
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set_type
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instance
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end
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# Return a new RR object of the correct type (like Net::DNS::RR::A
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# if the type is A) from a binary string, usually obtained from
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# network stream.
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#
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# This method is used when parsing a binary packet by the Packet
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# class.
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#
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def RR.parse(data)
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o = allocate
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obj,offset = o.send(:new_from_binary, data, 0)
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return obj
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end
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# Same as RR.parse, but takes an entire packet binary data to
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# perform name expansion. Default when analizing a packet
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# just received from a network stream.
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#
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# Return an instance of appropriate class and the offset
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# pointing at the end of the data parsed.
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#
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def RR.parse_packet(data,offset)
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o = allocate
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o.send(:new_from_binary,data,offset)
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end
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# Return the RR object in binary data format, suitable
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# for using in network streams, with names compressed.
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# Must pass as arguments the offset inside the packet
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# and an hash of compressed names.
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#
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# This method is to be used in other classes and is
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# not intended for user space programs.
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#
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# TO FIX in one of the future releases
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#
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def comp_data(offset,compnames)
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type,cls = @type.to_i, @cls.to_i
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str,offset,names = dn_comp(@name,offset,compnames)
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str += [type,cls,@ttl,@rdlength].pack("n2 N n")
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offset += Net::DNS::RRFIXEDSZ
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return str,offset,names
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end
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# Return the RR object in binary data format, suitable
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# for using in network streams.
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#
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# raw_data = rr.data
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# puts "RR is #{raw_data.size} bytes long"
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#
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def data
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type,cls = @type.to_i, @cls.to_i
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str = pack_name(@name)
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return str + [type,cls,@ttl,@rdlength].pack("n2 N n") + get_data
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end
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# Canonical inspect method
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#
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# mx = Net::DNS::RR.new("example.com. 7200 MX 10 mailhost.example.com.")
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# #=> example.com. 7200 IN MX 10 mailhost.example.com.
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#
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def inspect
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data = get_inspect
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# Returns the preformatted string
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if @name.size < 24
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[@name, @ttl.to_s, @cls.to_s, @type.to_s,
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data].pack("A24 A8 A8 A8 A*")
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else
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to_a.join(" ")
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end
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end
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# Returns the RR in a string format.
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#
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# mx = Net::DNS::RR.new("example.com. 7200 MX 10 mailhost.example.com.")
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# mx.to_s
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# #=> "example.com. 7200 IN MX 10 mailhost.example.com."
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#
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def to_s
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"#{self.inspect}"
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end
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# Returns an array with all the fields for the RR record.
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#
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# mx = Net::DNS::RR.new("example.com. 7200 MX 10 mailhost.example.com.")
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# mx.to_a
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# #=> ["example.com.",7200,"IN","MX","10 mailhost.example.com."]
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#
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def to_a
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[@name,@ttl,@cls.to_s,@type.to_s,get_inspect]
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end
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# Type accessor
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def type
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@type.to_s
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end
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# Class accessor
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def cls
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@cls.to_s
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end
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private
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#---
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# New RR with argument in string form
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#---
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def new_from_string(rrstring)
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unless rrstring =~ RR_REGEXP
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raise RRArgumentError,
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"Format error for RR string (maybe CLASS and TYPE not valid?)"
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end
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# Name of RR - mandatory
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begin
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@name = $1.downcase
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rescue NoMethodError
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raise RRArgumentError, "Missing name field in RR string #{rrstring}"
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end
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# Time to live for RR, default 3 hours
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@ttl = $2 ? $2.to_i : 10800
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# RR class, default to IN
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@cls = Net::DNS::RR::Classes.new $3
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# RR type, default to A
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@type = Net::DNS::RR::Types.new $4
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# All the rest is data
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@rdata = $5 ? $5.strip : ""
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if self.class == Net::DNS::RR
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(eval "Net::DNS::RR::#@type").new(rrstring)
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else
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subclass_new_from_string(@rdata)
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self.class
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end
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end
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def new_from_hash(args)
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# Name field is mandatory
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unless args.has_key? :name
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raise RRArgumentError, "RR argument error: need at least RR name"
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end
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@name = args[:name].downcase
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@ttl = args[:ttl] ? args[:ttl].to_i : 10800 # Default 3 hours
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@type = Net::DNS::RR::Types.new args[:type]
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@cls = Net::DNS::RR::Classes.new args[:cls]
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@rdata = args[:rdata] ? args[:rdata].strip : ""
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@rdlength = args[:rdlength] || @rdata.size
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if self.class == Net::DNS::RR
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(eval "Net::DNS::RR::#@type").new(args)
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else
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hash = args - [:name,:ttl,:type,:cls]
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if hash.has_key? :rdata
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subclass_new_from_string(hash[:rdata])
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else
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subclass_new_from_hash(hash)
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end
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self.class
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end
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end # new_from_hash
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def new_from_binary(data,offset)
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if self.class == Net::DNS::RR
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temp = dn_expand(data,offset)[1]
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type = Net::DNS::RR::Types.new data.unpack("@#{temp} n")[0]
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return unless Net::DNS::RR.const_defined?(type.to_s)
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(eval "Net::DNS::RR::#{type}").parse_packet(data,offset)
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else
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@name,offset = dn_expand(data,offset)
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rrtype,cls,@ttl,@rdlength = data.unpack("@#{offset} n2 N n")
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@type = Net::DNS::RR::Types.new rrtype
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@cls = Net::DNS::RR::Classes.new cls
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offset += RRFIXEDSZ
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offset = subclass_new_from_binary(data,offset)
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build_pack
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set_type
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return [self,offset]
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end
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# rescue StandardError => err
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# raise RRDataError, "Caught exception, maybe packet malformed: #{err}"
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end
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# Methods to be overridden by subclasses
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def subclass_new_from_array(arr)
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end
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def subclass_new_from_string(str)
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end
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def subclass_new_from_hash(hash)
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end
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def subclass_new_from_binary(data,offset)
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end
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def build_pack
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end
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def set_type
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end
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def get_inspect
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@rdata
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end
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def get_data
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@rdata
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end
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# NEW new method :)
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def self.new(*args)
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o = allocate
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obj = o.send(:initialize,*args)
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if self == Net::DNS::RR
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return obj
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else
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return o
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end
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end
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end # class RR
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end # module DNS
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end # module Net
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class RRArgumentError < ArgumentError # :nodoc:
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end
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class RRDataError < StandardError # :nodoc:
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end
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module ExtendHash # :nodoc:
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# Performs a sort of group difference
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# operation on hashes or arrays
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#
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# a = {:a=>1,:b=>2,:c=>3}
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# b = {:a=>1,:b=>2}
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# c = [:a,:c]
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# a-b #=> {:c=>3}
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# a-c #=> {:b=>2}
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#
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def -(oth)
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case oth
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when Hash
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delete_if {|k,v| oth.has_key? k}
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when Array
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delete_if {|k,v| oth.include? k}
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end
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end
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end
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class Hash # :nodoc:
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include ExtendHash
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end
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