src/networks/direct_connect/dcKey.ml

   1 (* Compute the key from $Lock xxxxx yyyyy| using 'gen_key xxxxx' *)
   2
   3
   4 (*************************************************************************)
   5 (* the key is quite easily :) computed from the lock                     *)
   6 (* key[x]= ns(lock[x]^lock[x-1])                                      *)
   7 (*   ns is a nibble swap (switch the upper 4 bits with the lower 4 bits) *)
   8 (* exception:                                                            *)
   9 (* key[0] is a bit different                                             *)
  10 (* let's name A and B the 2 last bytes of the lock                       *)
  11 (* key[0]= ns(lock[0]^A^B^0x05)         ; 0x05 is a kind of magic nibble *)
  12 (*************************************************************************)
  13
  14 (*
  15
  16 $Lock 17lM=.U=*@Q&HvoG2=HJcLH:-,Q=5R=xMvRo-ET4;nMZYxnP,P_&oHFmc%B Pk=.l>r?nZz-VKmlf&z|
  17
  18 $Key 5/%DCN096%/(181)(18)(7)1(183)(134)q(166)(17)w(230)(227)(145)(130)W(240)W (146)(242)@'q(16)(215)(198)(128)v(246)TS(179)B(211)/%DCN036%/(134)(17)(6)(240)U2q0(18)a(227)(199)(199)(240)(151)(148)r(224)(178)(224)dv|
  19
  20 *)
  21
  22 let char_is_extra ch buf =
  23     match ch with
  24     | 0 -> Printf.bprintf buf "/%%DCN000%%/"
  25     | 5 -> Printf.bprintf buf "/%%DCN005%%/"
  26     | 36 -> Printf.bprintf buf "/%%DCN036%%/"
  27     | 96 -> Printf.bprintf buf "/%%DCN096%%/"
  28     | 124 -> Printf.bprintf buf "/%%DCN124%%/"
  29     | 126 -> Printf.bprintf buf "/%%DCN126%%/"
  30     | _ -> Buffer.add_char buf (char_of_int ch)
  31
  32 let get s pos = int_of_char s.[pos]
  33
  34 let calculate_key s =
  35   let buf = Buffer.create 100 in
  36   let len = String.length s in
  37
  38 (* first byte *)
  39
  40   let u = (get s 0) land 255 in        (*  u=(((unsigned int)(lck->str[0]))&255); *)
  41   let l = (get s (len-1)) land 255 in  (* l=(((unsigned int)(lck->str[lck->len-1]))&255); *)
  42   let o = (get s (len-2)) land 255 in  (*  o=(((unsigned int)(lck->str[lck->len-2]))&255); *)
  43
  44   let u = u lxor l lxor o lxor 0x05 in (* u=u^l^o^0x05; *)
  45
  46   let v = (((u lsl 8) lor u) lsr 4) land 255 in (*  v=(((u<<8)|u)>>4)&255; *)
  47
  48   char_is_extra v buf;
  49 (*    match v with
  50     | 0 | 5 -> Printf.bprintf buf "/%%DCN%03d%%/" v
  51     | 36 -> Printf.bprintf buf "/%%DCN036%%/"
  52     | 96 -> Printf.bprintf buf "/%%DCN096%%/"
  53     | _ -> Buffer.add_char buf (char_of_int v) *)
  54   for i = 1 to len - 1 do
  55     let u = (get s i) land 255 in
  56     let l = (get s (i-1)) land 255 in
  57     let u = u lxor l in
  58     let v = (((u lsl 8) lor u) lsr 4) land 255 in (*  v=(((u<<8)|u)>>4)&255; *)
  59     char_is_extra v buf;
  60   done;
  61   Buffer.contents buf
  62
  63 let char_percent =  int_of_char '%'
  64 let char_z =  int_of_char 'z'
  65
  66 let create_key = "MLDonkey"
  67 (*  let len = 80 + Random.int 15  in
  68   let key = String.create len in
  69   for i = 0 to len - 1 do
  70     key.[i] <- char_of_int (char_percent + Random.int (char_z - char_percent))
  71   done;
  72   key *)
  73
  74