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# -*- coding: binary -*-
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module Net # :nodoc:
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  module DNS 
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    module Names # :nodoc: all
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      INT16SZ = 2
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      # Expand a compressed name in a DNS Packet object. Please
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      # see RFC1025 for an explanation of how the compression
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      # in DNS packets works, how may it be useful and how should
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      # be handled.
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      #
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      # This method accept two parameters: a raw packet data and an
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      # offset, which indicates the point in the packet in which the
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      # parsing has arrived.
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      #
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      def dn_expand(packet,offset)
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        name = ""
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        packetlen = packet.size
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        while true
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          raise ExpandError, "offset is greater than packet length!" if packetlen < (offset+1)
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          len = packet.unpack("@#{offset} C")[0]
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          if len == 0
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            offset += 1
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            break
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          elsif (len & 0xC0) == 0xC0
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            raise ExpandError, "Packet ended before offset expand" if packetlen < (offset+INT16SZ)
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            ptr = packet.unpack("@#{offset} n")[0]
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            ptr &= 0x3FFF
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            name2 = dn_expand(packet,ptr)[0]
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            raise ExpandError, "Packet is malformed!" if name2 == nil
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            name += name2
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            offset += INT16SZ
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            break
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          else
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            offset += 1
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            raise ExpandError, "No expansion found" if packetlen < (offset+len)
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            elem = packet[offset..offset+len-1]
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            name += "#{elem}."
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            offset += len
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          end
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        end
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        return [name,offset] # name.chomp(".") if trailing dot has to be omitted
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      end
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      def pack_name(name)
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        if name.size > 255
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          raise ArgumentError, "Name data cannot exceed 255 chars"
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        end
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        arr = name.split(".")
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        str = ""
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        arr.each do |elem|
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          if elem.size > 63
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            raise ArgumentError, "Label data cannot exceed 63 chars"
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          end
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          str += [elem.size,elem].pack("Ca*")
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        end
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        str += [0].pack("C")
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        str
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      end
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      def names_array(name)
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        arr = name.split(".")
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        ar = []
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        string = ""
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        arr.size.times do |i|
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          x = i+1
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          elem = arr[-x]
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          len = elem.size
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          string = ((string.reverse)+([len,elem].pack("Ca*")).reverse).reverse
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          ar.unshift(string)
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        end
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        return ar
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      end
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      def dn_comp(name,offset,compnames)
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        names = {}
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        ptr = 0
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        str = ""
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        arr = names_array(name)
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        arr.each do |entry|
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          if compnames.has_key?(entry)
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            ptr = 0xC000 | compnames[entry]
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            str += [ptr].pack("n")
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            offset += INT16SZ
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            break
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          else
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            len = entry.unpack("C")[0]
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            elem = entry[1..len]
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            str += [len,elem].pack("Ca*")
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            names.update({"#{entry}" => offset})
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            offset += len
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          end
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        end
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        return str,offset,names
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      end
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      def valid?(name)
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        if name =~ /^([a-z0-9]([-a-z0-9]*[a-z0-9])?\.)+((a[cdefgilmnoqrstuwxz]|aero|arpa)|(b[abdefghijmnorstvwyz]|biz)|(c[acdfghiklmnorsuvxyz]|cat|com|coop)|d[ejkmoz]|(e[ceghrstu]|edu)|f[ijkmor]|(g[abdefghilmnpqrstuwy]|gov)|h[kmnrtu]|(i[delmnoqrst]|info|int)|(j[emop]|jobs)|k[eghimnprwyz]|l[abcikrstuvy]|(m[acdghklmnopqrstuvwxyz]|mil|mobi|museum)|(n[acefgilopruz]|name|net)|(om|org)|(p[aefghklmnrstwy]|pro)|qa|r[eouw]|s[abcdeghijklmnortvyz]|(t[cdfghjklmnoprtvwz]|travel)|u[agkmsyz]|v[aceginu]|w[fs]|y[etu]|z[amw])$/i
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          return name
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        else
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          raise ArgumentError, "Invalid FQDN: #{name}"
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        end
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      end
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    end # module Names
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  end # module DNS
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end # module Net
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class ExpandError < StandardError # :nodoc:
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end
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