module Net # :nodoc: module DNS module Names # :nodoc: all INT16SZ = 2 # Expand a compressed name in a DNS Packet object. Please # see RFC1025 for an explanation of how the compression # in DNS packets works, how may it be useful and how should # be handled. # # This method accept two parameters: a raw packet data and an # offset, which indicates the point in the packet in which the # parsing has arrived. # def dn_expand(packet,offset) name = "" packetlen = packet.size while true raise ExpandError, "offset is greater than packet lenght!" if packetlen < (offset+1) len = packet.unpack("@#{offset} C")[0] if len == 0 offset += 1 break elsif (len & 0xC0) == 0xC0 raise ExpandError, "Packet ended before offset expand" if packetlen < (offset+INT16SZ) ptr = packet.unpack("@#{offset} n")[0] ptr &= 0x3FFF name2 = dn_expand(packet,ptr)[0] raise ExpandError, "Packet is malformed!" if name2 == nil name += name2 offset += INT16SZ break else offset += 1 raise ExpandError, "No expansion found" if packetlen < (offset+len) elem = packet[offset..offset+len-1] name += "#{elem}." offset += len end end return [name,offset] # name.chomp(".") if trailing dot has to be omitted end def pack_name(name) if name.size > 63 raise ArgumentError, "Label data cannot exceed 63 chars" end arr = name.split(".") str = "" arr.each do |elem| str += [elem.size,elem].pack("Ca*") end str += [0].pack("C") str end def names_array(name) arr = name.split(".") ar = [] string = "" arr.size.times do |i| x = i+1 elem = arr[-x] len = elem.size string = ((string.reverse)+([len,elem].pack("Ca*")).reverse).reverse ar.unshift(string) end return ar end def dn_comp(name,offset,compnames) names = {} ptr = 0 str = "" arr = names_array(name) arr.each do |entry| if compnames.has_key?(entry) ptr = 0xC000 | compnames[entry] str += [ptr].pack("n") offset += INT16SZ break else len = entry.unpack("C")[0] elem = entry[1..len] str += [len,elem].pack("Ca*") names.update({"#{entry}" => offset}) offset += len end end return str,offset,names end def valid?(name) 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 return name else raise ArgumentError, "Invalid FQDN: #{name}" end end end # module Names end # module DNS end # module Net class ExpandError < StandardError # :nodoc: end