(************************************************************************)
(* This file is part of SKS.  SKS is free software; you can
   redistribute it and/or modify it under the terms of the GNU General
   Public License as published by the Free Software Foundation; either
   version 2 of the License, or (at your option) any later version.

   This program is distributed in the hope that it will be useful, but
   WITHOUT ANY WARRANTY; without even the implied warranty of
   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
   General Public License for more details.

   You should have received a copy of the GNU General Public License
   along with this program; if not, write to the Free Software
   Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307
   USA *)
(***********************************************************************)

open StdLabels
open MoreLabels

open Common
open Packet
open Printf

exception Overlong_mpi
exception Partial_body_length of int

(********************************************************)

(** parse new-style packet length *)
let parse_new_packet_length cin = 
  let byte1 = cin#read_byte in
  if byte1 <= 191 then byte1  (* one-octet length *)
  else if byte1 <= 223  then (* two-octet length *) 
    let byte2 = cin#read_byte in 
    (byte1 - 192) lsl 8 + byte2 + 192
  else if byte1 = 255 then (* five-octet length *)
    let byte2 = cin#read_byte in 
    let byte3 = cin#read_byte in
    let byte4 = cin#read_byte in
    let byte5 = cin#read_byte in
    (byte2 lsl 24) lor (byte3 lsl 16) lor (byte4 lsl 8) lor byte5
  else (* partial body length *)
    raise (Partial_body_length (1 lsl (byte1 land 0x1f)))

(********************************************************)

let read_packet cin = 
  let packet_tag = cin#read_byte in
  if ((packet_tag lsr 7) land 1 <> 1) 
  then failwith (sprintf "Bit 7 of packet tag was not 1 as expected: %x" 
		   packet_tag);
  match (packet_tag lsr 6) land 1 with

      0 -> (* old format *)
	let content_tag = (packet_tag land 0b111100) lsr 2
	and length_type = packet_tag land 0b11
	in 
	(match length_type with
	     0 | 1 | 2 -> 
	       let length_length = 1 lsl length_type in
	       let length_str = cin#read_string length_length in
	       let length = Utils.int_from_bstring length_str 
			      ~pos:0 ~len:length_length in
	       { content_tag = content_tag;
		 packet_type = content_tag_to_ptype content_tag;
		 packet_length = length;
		 packet_body = cin#read_string length;
	       }
	       
	   | 3 -> (* indeterminate length header --- extends to end of file *)
	       failwith "Unexpected indeterminate length packet"
	   | _ -> 
	       failwith "Unexpected length type"
	)

    | 1 -> (* new_format *)
	let content_tag = packet_tag land 0b111111 in
	let length = parse_new_packet_length cin in
	{ (* packet_tag = packet_tag; *)
	  content_tag = content_tag;
	  packet_type = content_tag_to_ptype content_tag;
	  packet_length = length;
	  packet_body = cin#read_string length;
	}

    | _ -> raise (Bug "ParsePGP.read_packet: expected 0/1 value")

    
(********************************************************)

let offset_read_packet cin = 
  let offset = LargeFile.pos_in cin#inchan in
  let packet = read_packet cin in
  (offset,packet)

(********************************************************)

let offset_length_read_packet cin = 
  let offset = pos_in cin#inchan in
  let packet = read_packet cin in
  let final_offset = pos_in cin#inchan in
  (packet,offset,final_offset - offset)

(********************************************************)

let read_mpi cin = 
  let byte1 = cin#read_byte in
  try
    let byte2 = cin#read_byte in
    let length = (byte1 lsl 8) + byte2 in
    let data = cin#read_string 
		 ((length + 7)/8)
    in
    { mpi_bits = length; mpi_data = data }
  with
      End_of_file -> raise Overlong_mpi

(********************************************************)

let parse_pubkey_info packet = 
  let cin = new Channel.string_in_channel packet.packet_body 0 in
  let version = cin#read_byte in
  let creation_time = cin#read_int64_size 4 in
  let (algorithm,mpi,expiration) = 
    match version with
      | 4 -> 
	  let algorithm = cin#read_byte in
	  let mpi = read_mpi cin in
	  (algorithm,mpi,None)
      | 2 | 3 ->
	  let expiration = cin#read_int_size 2 in
	  let algorithm = cin#read_byte in
	  let mpi = read_mpi cin in
	  (algorithm,mpi,Some expiration)
      | _ -> failwith (sprintf "Unexpected pubkey version: %d" version)
  in
  { pk_version = version;
    pk_ctime = creation_time;
    pk_expiration = (match expiration with Some 0 -> None | x -> x);
    pk_alg = algorithm;
    pk_keylen = mpi.mpi_bits;
  }
  
(********************************************************)


(** Parsing of signature subpackets *)

(** parse sigsubpacket length *)
let parse_sigsubpacket_length cin = 
  let byte1 = cin#read_byte in
  if byte1 < 192 then byte1 (* one octet length *)
  else if byte1  < 255 then
    let byte2 = cin#read_byte in
    ((byte1 - 192) lsl 8) + (byte2) + 192
  else if byte1 = 255 then (* five-octet length *)
    let byte2 = cin#read_byte in 
    let byte3 = cin#read_byte in
    let byte4 = cin#read_byte in
    let byte5 = cin#read_byte in
    (byte2 lsl 24) lor (byte3 lsl 16) lor (byte4 lsl 8) lor byte5
  else
    failwith "Unable to parse sigsubpacket length"
    
let read_sigsubpacket cin = 
  let length = parse_sigsubpacket_length cin in
  let ssp_type = cin#read_byte land 0x7f in
  let body = cin#read_string (length - 1) in
  { ssp_length = length - 1;
    ssp_type = ssp_type;
    ssp_body = body;
  }

let get_hashed_subpacket_string cin = 
  let version = cin#read_byte in
  if version <> 4 then 
    failwith "Attempt to parse non-v4 signature as v4 signature";
  let sigtype = cin#read_byte in
  let key_alg = cin#read_byte in
  let hash_alg = cin#read_byte in
  let hashed_subpacket_count = cin#read_int_size 2 in
  (* now we can start reading the hashed sub-packets *)
  cin#read_string hashed_subpacket_count 

(** return list of signature sub-packets *)
let read_subpackets cin length = 
  let subpacket_string = cin#read_string length in
  let cin = new Channel.string_in_channel subpacket_string 0 in
  let rec loop list = 
    match (try Some (read_sigsubpacket cin) 
	   with End_of_file -> None)
    with
      | Some subpack -> loop (subpack::list)
      | None -> List.rev list
  in 
  loop []
    
let read_mpis cin = 
  let rec loop list = 
    match (try (Some (read_mpi cin))
	   with End_of_file -> None)
    with
      | Some mpi -> loop (mpi::list)
      | None -> List.rev list
  in
  loop []

let parse_signature packet = 
  let cin = new Channel.string_in_channel packet.packet_body 0 in
  let version = cin#read_byte in
  match version with

    | 2 | 3 ->
	cin#skip 1; (* length packet which must be 5 *)
	let sigtype = cin#read_byte in
	let ctime = cin#read_int64_size 4 in
	let keyid = cin#read_string 8 in
	let pk_alg = cin#read_byte in
	let hash_alg = cin#read_byte in
	let hash_value = cin#read_string 2 in
	let mpis = read_mpis cin in
	V3sig { v3s_sigtype = sigtype;
		v3s_ctime = ctime;
		v3s_keyid = keyid;
		v3s_pk_alg = pk_alg;
		v3s_hash_alg = hash_alg;
		v3s_hash_value = hash_value;
		v3s_mpis = mpis;
	      }

    | 4 ->
	let sigtype = cin#read_byte in
	let pk_alg = cin#read_byte in
	let hash_alg = cin#read_byte in

	let hashed_subpacket_bytes = cin#read_int_size 2 in
	let hashed_subpackets = read_subpackets cin hashed_subpacket_bytes in

	let unhashed_subpacket_bytes = cin#read_int_size 2 in
	let unhashed_subpackets = read_subpackets cin unhashed_subpacket_bytes in
	
	let hash_value = cin#read_string 2 in
	let mpis = read_mpis cin in
	V4sig { v4s_sigtype = sigtype;
		v4s_pk_alg = pk_alg;
		v4s_hashed_subpackets = hashed_subpackets;
		v4s_unhashed_subpackets = unhashed_subpackets;
		v4s_hash_value = hash_value;
		v4s_mpis = mpis;
	      }
	

    | _ -> failwith (sprintf "Unexpected signature version: %d" version)
	  

let ssp_ctime_id = 2
let ssp_exptime_id = 3

let int32_of_string s = 
  let cin = new Channel.string_in_channel s 0 in
  cin#read_int32

let int64_of_string s = 
  let cin = new Channel.string_in_channel s 0 in
  cin#read_int64_size (String.length s)

let get_times sign = match sign with
  | V3sig sign ->
      (Some sign.v3s_ctime, None)
  | V4sig sign ->
      let hashed_subpackets = sign.v4s_hashed_subpackets in
      let (ctime,exptime_delta) = 
	List.fold_left hashed_subpackets ~init:(None,None)
	  ~f:(fun (ctime,exptime) ssp -> 
		if ssp.ssp_type = ssp_ctime_id && ssp.ssp_length = 4 then
		  (Some (int64_of_string ssp.ssp_body),exptime)
		else if ssp.ssp_type = ssp_exptime_id && ssp.ssp_length = 4 then
		  (ctime,Some (int64_of_string ssp.ssp_body))
		else
		  (ctime,exptime)
	     )
      in
      match (ctime,exptime_delta) with
	| (Some x,None) -> (Some x,None)
	| (None,_) -> (None,None)
	| (Some x,Some y) -> (Some x,Some (Int64.add x y))