RFC4034, section 4 The NSEC resource record lists two separate things: the next owner name (in the canonical ordering of the zone) that contains authoritative data or a delegation point NS RRset, and the set of RR types present at the NSEC RR's owner name [RFC3845]. The complete set of NSEC RRs in a zone indicates which authoritative RRsets exist in a zone and also form a chain of authoritative owner names in the zone. This information is used to provide authenticated denial of existence for DNS data, as described in [RFC4035].
# File lib/Dnsruby/resource/NSEC.rb, line 105 def self.decode_types(bytes) types = [] #RFC4034 section 4.1.2 #The RR type space is split into 256 window blocks, each representing #the low-order 8 bits of the 16-bit RR type space. Each block that #has at least one active RR type is encoded using a single octet #window number (from 0 to 255), a single octet bitmap length (from 1 #to 32) indicating the number of octets used for the window block's #bitmap, and up to 32 octets (256 bits) of bitmap. #Blocks are present in the NSEC RR RDATA in increasing numerical #order. # Type Bit Maps Field = ( Window Block # | Bitmap Length | Bitmap )+ # where "|" denotes concatenation. pos = 0 while (pos < bytes.length) #So, read the first two octets if (bytes.length-pos < 2) raise DecodeError.new("NSEC : Expected window number and bitmap length octets") end window_number = bytes[pos] bitmap_length = bytes[pos+1] if (window_number.class == String) # Ruby 1.9 window_number = window_number.getbyte(0) bitmap_length = bitmap_length.getbyte(0) end pos += 2 bitmap = bytes[pos,bitmap_length] pos += bitmap_length #Each bitmap encodes the low-order 8 bits of RR types within the #window block, in network bit order. The first bit is bit 0. For #window block 0, bit 1 corresponds to RR type 1 (A), bit 2 corresponds #to RR type 2 (NS), and so forth. For window block 1, bit 1 #corresponds to RR type 257, and bit 2 to RR type 258. If a bit is #set, it indicates that an RRset of that type is present for the NSEC #RR's owner name. If a bit is clear, it indicates that no RRset of #that type is present for the NSEC RR's owner name. index = 0 bitmap.each_byte do |char| if char.to_i != 0 # decode these RR types 0..8.times do |i| if (((1 << (7-i)) & char) == (1 << (7-i))) type = Types.new((256 * window_number) + (8 * index) + i) #Bits representing pseudo-types MUST be clear, as they do not appear #in zone data. If encountered, they MUST be ignored upon being read. if (!([Types::OPT, Types::TSIG].include?(type))) types.push(type) end end end end index += 1 end end return types end
# File lib/Dnsruby/resource/NSEC.rb, line 170 def self.encode_types(nsec) output="" #types represents all 65536 possible RR types. #Split up types into sets of 256 different types. type_codes = [] nsec.types.each do |type| type_codes.push(type.code) end type_codes.sort! window = -1 0.step(65536,256) { |step| # Gather up the RR types for this set of 256 types_to_go = [] while (!type_codes.empty? && type_codes[0] < step) types_to_go.push(type_codes[0]) # And delete them from type_codes type_codes=type_codes.last(type_codes.length-1) break if (type_codes.empty?) end if (!types_to_go.empty?) # Then create the bitmap for them bitmap="" # keep on adding them until there's none left pos = 0 bitmap_pos = 0 while (!types_to_go.empty?) # Check the next eight byte = 0 pos += 8 while (types_to_go[0] < pos + step-256) byte = byte | (1 << (pos-1-(types_to_go[0] - (step-256) ))) # Add it to the list # And remove it from the to_go queue types_to_go =types_to_go.last(types_to_go.length-1) break if (types_to_go.empty?) end bitmap += " " if (bitmap[bitmap_pos].class == String) bitmap.setbyte(bitmap_pos, byte) # Ruby 1.9 else bitmap[bitmap_pos]=byte end bitmap_pos+=1 end # Now add data to output bytes start = output.length (2+bitmap.length).times do output += " " end if (output[start].class == String) output.setbyte(start, window) output.setbyte(start+1, bitmap.length) bitmap.length.times do |i| output.setbyte(start+2+i, bitmap[i].getbyte(0)) end else output[start] = window output[start+1] = bitmap.length bitmap.length.times do |i| output[start+2+i] = bitmap[i] end end end window += 1 # Are there any more types after this? if (type_codes.empty?) # If not, then break (so we don't add more zeros) break end } if (output[0].class == String) output = output.force_encoding("ascii-8bit") end return output end
# File lib/Dnsruby/resource/NSEC.rb, line 76 def self.get_types(t) types = nil if (t.instance_of?Array) # from the wire, already decoded types =t elsif (t.instance_of?String) if (index = t.index";") t = t[0, index] end if (index = t.index")") t = t[0, index] end # List of mnemonics types=[] mnemonics = t.split(" ") mnemonics.each do |m| type = Types.new(m) types.push(type) end else raise DecodeError.new("Unknown format of types for Dnsruby::RR::NSEC") end return types end
# File lib/Dnsruby/resource/NSEC.rb, line 101 def add_type(t) self.types=(@types + [t]) end
# File lib/Dnsruby/resource/NSEC.rb, line 45 def check_name_in_range(n) # Check if the name is covered by this record if (@name.wild?) return check_name_in_wildcard_range(n) end if (name.canonically_before(n) && (n.canonically_before(next_domain))) return true end return false end
# File lib/Dnsruby/resource/NSEC.rb, line 56 def check_name_in_wildcard_range(n) # Check if the name is covered by this record return false if !@name.wild? return false if @next_domain.canonically_before(n) # Now just check that the wildcard is *before* the name # Strip the first label ("*") and then compare n2 = Name.create(@name) n2.labels.delete_at(0) return false if n.canonically_before(n2) return true end
# File lib/Dnsruby/resource/NSEC.rb, line 166 def encode_types NSEC.encode_types(self) end
# File lib/Dnsruby/resource/NSEC.rb, line 257 def from_string(input) if (input.length > 0) data = input.split(" ") self.next_domain=(data[0]) len = data[0].length+ 1 if (data[1] == "(") len = len + data[1].length end self.types=(input[len, input.length-len]) @types = NSEC.get_types(input[len, input.length-len]) end end
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