tools/descramble.c

   1 /***************************************************************************
   2  *             __________               __   ___.
   3  *   Open      \______   \ ____   ____ |  | _\_ |__   _______  ___
   4  *   Source     |       _//  _ \_/ ___\|  |/ /| __ \ /  _ \  \/  /
   5  *   Jukebox    |    |   (  <_> )  \___|    < | \_\ (  <_> > <  <
   6  *   Firmware   |____|_  /\____/ \___  >__|_ \|___  /\____/__/\_ \
   7  *                     \/            \/     \/    \/            \/
   8  * $Id$
   9  *
  10  * Copyright (C) 2002 by Björn Stenberg
  11  *
  12  * This program is free software; you can redistribute it and/or
  13  * modify it under the terms of the GNU General Public License
  14  * as published by the Free Software Foundation; either version 2
  15  * of the License, or (at your option) any later version.
  16  *
  17  * This software is distributed on an "AS IS" basis, WITHOUT WARRANTY OF ANY
  18  * KIND, either express or implied.
  19  *
  20  ****************************************************************************/
  21
  22 #include <stdio.h>
  23 #include <stdlib.h>
  24 #include <string.h>
  25
  26 #include "iriver.h"
  27 #include "gigabeat.h"
  28
  29 int iaudio_decode(char *iname, char *oname);
  30
  31 unsigned int le2int(unsigned char* buf)
  32 {
  33    unsigned int res = (buf[3] << 24) | (buf[2] << 16) | (buf[1] << 8) | buf[0];
  34
  35    return res;
  36 }
  37
  38 void int2le(unsigned int val, unsigned char* addr)
  39 {
  40     addr[0] = val & 0xFF;
  41     addr[1] = (val >> 8) & 0xff;
  42     addr[2] = (val >> 16) & 0xff;
  43     addr[3] = (val >> 24) & 0xff;
  44 }
  45
  46 void usage(void)
  47 {
  48     printf("usage: descramble [options] <input file> <output file>\n");
  49     printf("options:\n"
  50            "\t-fm     Archos FM recorder format\n"
  51            "\t-v2     Archos V2 recorder format\n"
  52            "\t-mm     Archos Multimedia format\n"
  53            "\t-iriver iRiver format\n"
  54            "\t-gigabeat Toshiba Gigabeat format\n"
  55            "\t-iaudio iAudio format\n"
  56           "\nNo option assumes Archos standard player/recorder format.\n");
  57     exit(1);
  58 }
  59
  60 int main (int argc, char** argv)
  61 {
  62     unsigned long length,i,slen;
  63     unsigned char *inbuf,*outbuf;
  64     char *iname = argv[1];
  65     char *oname = argv[2];
  66     unsigned char header[32];
  67     int headerlen = 6;
  68     int descramble = 1;
  69     FILE* file;
  70
  71     if (argc < 3) {
  72         usage();
  73     }
  74
  75     if (!strcmp(argv[1], "-fm") || !strcmp(argv[1], "-v2")) {
  76         headerlen = 24;
  77         iname = argv[2];
  78         oname = argv[3];
  79     }
  80
  81     if (!strcmp(argv[1], "-mm")) {
  82         headerlen = 16;
  83         iname = argv[2];
  84         oname = argv[3];
  85         descramble = 0;
  86     }
  87
  88     if(!strcmp(argv[1], "-iriver")) {
  89         /* iRiver code dealt with in the iriver.c code */
  90         iname = argv[2];
  91         oname = argv[3];
  92         return iriver_decode(iname, oname, FALSE, STRIP_NONE) ? -1 : 0;
  93     }
  94     if(!strcmp(argv[1], "-gigabeat")) {
  95         iname = argv[2];
  96         oname = argv[3];
  97         gigabeat_code(iname, oname);
  98         return 0;
  99     }
 100
 101     if(!strcmp(argv[1], "-iaudio")) {
 102         iname = argv[2];
 103         oname = argv[3];
 104         return iaudio_decode(iname, oname);
 105     }
 106
 107     /* open file and check size */
 108     file = fopen(iname,"rb");
 109     if (!file) {
 110        perror(iname);
 111        return -1;
 112     }
 113     fseek(file,0,SEEK_END);
 114     length = ftell(file) - headerlen; /* skip header */
 115     fseek(file,0,SEEK_SET);
 116     i = fread(header, 1, headerlen, file);
 117     if ( !i ) {
 118        perror(iname);
 119        return -1;
 120     }
 121
 122     inbuf = malloc(length);
 123     outbuf = malloc(length);
 124     if ( !inbuf || !outbuf ) {
 125        printf("out of memory!\n");
 126        return -1;
 127     }
 128
 129     /* read file */
 130     i=fread(inbuf,1,length,file);
 131     if ( !i ) {
 132        perror(iname);
 133        return -1;
 134     }
 135     fclose(file);
 136
 137     if (descramble) {
 138         /* descramble */
 139         slen = length/4;
 140         for (i = 0; i < length; i++) {
 141             unsigned long addr = ((i % slen) << 2) + i/slen;
 142             unsigned char data = inbuf[i];
 143             data = ~((data >> 1) | ((data << 7) & 0x80)); /* poor man's ROR */
 144             outbuf[addr] = data;
 145         }
 146     }
 147     else {
 148         void* tmpptr;
 149         unsigned int j=0;
 150         int stringlen = 32;
 151         int unpackedsize;
 152         unsigned char xorstring[32];
 153
 154         unpackedsize = header[4] | header[5] << 8;
 155         unpackedsize |= header[6] << 16 | header[7] << 24;
 156
 157         length = header[8] | header[9] << 8;
 158         length |= header[10] << 16 | header[11] << 24;
 159
 160         /* calculate the xor string used */
 161         for (i=0; i<(unsigned long)stringlen; i++) {
 162             int top=0, topchar=0, c;
 163             int bytecount[256];
 164             memset(bytecount, 0, sizeof(bytecount));
 165
 166             /* gather byte frequency statistics */
 167             for (c=i; c<(int)length; c+=stringlen)
 168                 bytecount[inbuf[c]]++;
 169
 170             /* find the most frequent byte */
 171             for (c=0; c<256; c++) {
 172                 if (bytecount[c] > top) {
 173                     top = bytecount[c];
 174                     topchar = c;
 175                 }
 176             }
 177             xorstring[i] = topchar;
 178         }
 179         printf("XOR string: %.*s\n", stringlen, xorstring);
 180
 181         /* xor the buffer */
 182         for (i=0; i<length; i++)
 183             outbuf[i] = inbuf[i] ^ xorstring[i & (stringlen-1)];
 184
 185         /* unpack */
 186         tmpptr = realloc(inbuf, unpackedsize);
 187         memset(tmpptr, 0, unpackedsize);
 188         inbuf = outbuf;
 189         outbuf = tmpptr;
 190
 191         for (i=0; i<length;) {
 192             int bit;
 193             int head = inbuf[i++];
 194
 195             for (bit=0; bit<8 && i<length; bit++) {
 196                 if (head & (1 << (bit))) {
 197                     outbuf[j++] = inbuf[i++];
 198                 }
 199                 else {
 200                     int x;
 201                     int byte1 = inbuf[i];
 202                     int byte2 = inbuf[i+1];
 203                     int count = (byte2 & 0x0f) + 3;
 204                     int src =
 205                         (j & 0xfffff000) + (byte1 | ((byte2 & 0xf0)<<4)) + 18;
 206                     if (src > (int)j)
 207                         src -= 0x1000;
 208
 209                     for (x=0; x<count; x++)
 210                         outbuf[j++] = outbuf[src+x];
 211                     i += 2;
 212                 }
 213             }
 214         }
 215         length = j;
 216     }
 217
 218     /* write file */
 219     file = fopen(oname,"wb");
 220     if ( !file ) {
 221        perror(argv[2]);
 222        return -1;
 223     }
 224     if ( !fwrite(outbuf,length,1,file) ) {
 225        perror(argv[2]);
 226        return -1;
 227     }
 228     fclose(file);
 229
 230     free(inbuf);
 231     free(outbuf);
 232
 233     return 0;
 234 }
 235
 236 int iaudio_decode(char *iname, char *oname)
 237 {
 238     size_t len;
 239     int length;
 240     FILE *file;
 241     char *outbuf;
 242     int i;
 243     unsigned char sum = 0;
 244     unsigned char filesum;
 245
 246     file = fopen(iname, "rb");
 247     if (!file) {
 248         perror(iname);
 249         return -1;
 250     }
 251     fseek(file,0,SEEK_END);
 252     length = ftell(file);
 253
 254     fseek(file,0,SEEK_SET);
 255     outbuf = malloc(length);
 256
 257     if ( !outbuf ) {
 258         printf("out of memory!\n");
 259         return -1;
 260     }
 261
 262     len = fread(outbuf, 1, length, file);
 263     if(len < (size_t)length) {
 264         perror(iname);
 265         return -2;
 266     }
 267
 268     fclose(file);
 269
 270     for(i = 0; i < length-0x1030;i++)
 271         sum += outbuf[0x1030 + i];
 272
 273     filesum = outbuf[0x102b];
 274
 275     if(filesum != sum) {
 276         printf("Checksum mismatch!\n");
 277         return -1;
 278     }
 279
 280     file = fopen(oname, "wb");
 281     if (!file) {
 282         perror(oname);
 283         return -3;
 284     }
 285
 286     len = fwrite(outbuf+0x1030, 1, length-0x1030, file);
 287     if(len < (size_t)length-0x1030) {
 288         perror(oname);
 289         return -4;
 290     }
 291
 292     fclose(file);
 293     return 0;
 294 }