93 lines
3.6 KiB
OCaml
93 lines
3.6 KiB
OCaml
open Types
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open Utils
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let parse_header (reader : reader) =
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let max_size = 6 in
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match List.init max_size (fun offset -> unpack_short_be reader.data (offset * 2)) with
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| [ id; flags; num_questions; num_answers; num_authorities; num_additionals ] ->
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( { reader with pointer = reader.pointer + (max_size * 2) }
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, { id; flags; num_questions; num_answers; num_authorities; num_additionals } )
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| _ -> failwith "Invalid number of fields"
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;;
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let rec parse_question (reader : reader) =
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let name, offset_name = decode_name reader in
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let data = bytes_forward reader.data (reader.pointer + offset_name) in
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let max_size = 2 in
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match List.init max_size (fun offset -> unpack_short_be data (offset * 2)) with
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| [ type_; class_ ] ->
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( { reader with pointer = reader.pointer + offset_name + (max_size * 2) }
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, { name; type_; class_ } )
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| _ -> failwith "Invalid number of fields"
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and decode_name reader =
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let rec read_parts parts pos =
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let length = int_of_char (Bytes.get reader.data (reader.pointer + pos)) in
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if length = 0
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then 1, parts
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else if length land 0b1100_0000 <> 0
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then (
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let decoded_name = decode_compressed_name reader length in
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2, decoded_name :: parts)
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else (
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let part = Bytes.sub_string reader.data (reader.pointer + pos + 1) length in
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let last_length, parts' = read_parts (parts @ [ part ]) (pos + 1 + length) in
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last_length + length + 1, parts')
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in
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let offset, parts = read_parts [] 0 in
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String.to_bytes (String.concat "." parts), offset
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and decode_compressed_name reader length =
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let pointer =
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(length land 0b0011_1111) + int_of_char (Bytes.get reader.data (reader.pointer + 1))
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in
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String.of_bytes (fst (decode_name { reader with pointer }))
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;;
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let parse_record reader =
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let name, offset_name = decode_name reader in
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let data = bytes_forward reader.data (offset_name + reader.pointer) in
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let data_len = unpack_short_be data 8 in
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let record_len = 10 in
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let type_ = unpack_short_be data 0 in
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( { reader with pointer = reader.pointer + offset_name + record_len + data_len }
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, { name
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; type_
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; class_ = unpack_short_be data 2
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; ttl = unpack_int_be data 4
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; data =
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(let raw_data = Bytes.sub data record_len data_len in
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match type_ with
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| v when v = DNSType.ns ->
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print_endline "aaaaaaaaaaaaa";
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let r1, r2 =
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decode_name
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{ reader with pointer = reader.pointer + offset_name + record_len }
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in
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Printf.printf "%s - %d\n" (String.of_bytes r1) r2;
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r1
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| v when v = DNSType.a -> String.to_bytes (get_ip raw_data)
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| _ -> raw_data)
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} )
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;;
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let parse_dns_packet data =
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let rec create_list reader n fn acc =
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if n = 0
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then reader, List.rev acc
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else (
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let next_reader, res = fn reader in
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create_list next_reader (n - 1) fn (res :: acc))
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in
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let reader, header = parse_header { data; pointer = 0 } in
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let reader2, questions = create_list reader header.num_questions parse_question [] in
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let reader3, answers = create_list reader2 header.num_answers parse_record [] in
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let reader4, authorities = create_list reader3 header.num_authorities parse_record [] in
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let _, additionals = create_list reader4 header.num_additionals parse_record [] in
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(* print_endline (Debug.dns_header header);
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List.iter (fun el -> print_endline (Debug.dns_question el)) questions;
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List.iter (fun el -> print_endline (Debug.dns_record el)) answers;
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List.iter (fun el -> print_endline (Debug.dns_record el)) authorities;
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List.iter (fun el -> print_endline (Debug.dns_record el)) additionals; *)
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{ header; questions; answers; authorities; additionals }
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;;
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