base/applications/mstsc/mppc.c

   1 /* -*- c-basic-offset: 8 -*-
   2    rdesktop: A Remote Desktop Protocol client.
   3    Protocol services - RDP decompression
   4    Copyright (C) Matthew Chapman <matthewc.unsw.edu.au> 1999-2008
   5
   6    This program is free software: you can redistribute it and/or modify
   7    it under the terms of the GNU General Public License as published by
   8    the Free Software Foundation, either version 3 of the License, or
   9    (at your option) any later version.
  10
  11    This program is distributed in the hope that it will be useful,
  12    but WITHOUT ANY WARRANTY; without even the implied warranty of
  13    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  14    GNU General Public License for more details.
  15
  16    You should have received a copy of the GNU General Public License
  17    along with this program.  If not, see <http://www.gnu.org/licenses/>.
  18 */
  19
  20 #include <stdio.h>
  21 #include <string.h>
  22
  23 #include "precomp.h"
  24
  25 /* mppc decompression                       */
  26 /* http://www.faqs.org/rfcs/rfc2118.html    */
  27
  28 /* Contacts:                                */
  29
  30 /* hifn contact mentioned in the faq is     */
  31 /* Robert Friend rfriend at hifn dot com    */
  32
  33 /* if you have questions regarding MPPC     */
  34 /* our contact is                           */
  35 /* Guus Dhaeze  GDhaeze at hifn dot com     */
  36
  37 /* Licensing:                               */
  38
  39 /* decompression is alright as long as we   */
  40 /* don't compress data                      */
  41
  42 /* Algorithm: */
  43
  44 /* as the rfc states the algorithm seems to */
  45 /* be LZ77 with a sliding buffer            */
  46 /* that is empty at init.                   */
  47
  48 /* the algorithm is called LZS and is       */
  49 /* patented for another couple of years.    */
  50
  51 /* more information is available in         */
  52 /* http://www.ietf.org/ietf/IPR/hifn-ipr-draft-friend-tls-lzs-compression.txt */
  53
  54
  55 RDPCOMP g_mppc_dict;
  56
  57 int
  58 mppc_expand(uint8 * data, uint32 clen, uint8 ctype, uint32 * roff, uint32 * rlen)
  59 {
  60         int k, walker_len = 0, walker;
  61         uint32 i = 0;
  62         int next_offset, match_off;
  63         int match_len;
  64         int old_offset, match_bits;
  65         RD_BOOL big = ctype & RDP_MPPC_BIG ? True : False;
  66
  67         uint8 *dict = g_mppc_dict.hist;
  68
  69         if ((ctype & RDP_MPPC_COMPRESSED) == 0)
  70         {
  71                 *roff = 0;
  72                 *rlen = clen;
  73                 return 0;
  74         }
  75
  76         if ((ctype & RDP_MPPC_RESET) != 0)
  77         {
  78                 g_mppc_dict.roff = 0;
  79         }
  80
  81         if ((ctype & RDP_MPPC_FLUSH) != 0)
  82         {
  83                 memset(dict, 0, RDP_MPPC_DICT_SIZE);
  84                 g_mppc_dict.roff = 0;
  85         }
  86
  87         *roff = 0;
  88         *rlen = 0;
  89
  90         walker = g_mppc_dict.roff;
  91
  92         next_offset = walker;
  93         old_offset = next_offset;
  94         *roff = old_offset;
  95         if (clen == 0)
  96                 return 0;
  97         clen += i;
  98
  99         do
 100         {
 101                 if (walker_len == 0)
 102                 {
 103                         if (i >= clen)
 104                                 break;
 105                         walker = data[i++] << 24;
 106                         walker_len = 8;
 107                 }
 108                 if (walker >= 0)
 109                 {
 110                         if (walker_len < 8)
 111                         {
 112                                 if (i >= clen)
 113                                 {
 114                                         if (walker != 0)
 115                                                 return -1;
 116                                         break;
 117                                 }
 118                                 walker |= (data[i++] & 0xff) << (24 - walker_len);
 119                                 walker_len += 8;
 120                         }
 121                         if (next_offset >= RDP_MPPC_DICT_SIZE)
 122                                 return -1;
 123                         dict[next_offset++] = (((uint32) walker) >> ((uint32) 24));
 124                         walker <<= 8;
 125                         walker_len -= 8;
 126                         continue;
 127                 }
 128                 walker <<= 1;
 129                 /* fetch next 8-bits */
 130                 if (--walker_len == 0)
 131                 {
 132                         if (i >= clen)
 133                                 return -1;
 134                         walker = data[i++] << 24;
 135                         walker_len = 8;
 136                 }
 137                 /* literal decoding */
 138                 if (walker >= 0)
 139                 {
 140                         if (walker_len < 8)
 141                         {
 142                                 if (i >= clen)
 143                                         return -1;
 144                                 walker |= (data[i++] & 0xff) << (24 - walker_len);
 145                                 walker_len += 8;
 146                         }
 147                         if (next_offset >= RDP_MPPC_DICT_SIZE)
 148                                 return -1;
 149                         dict[next_offset++] = (uint8) (walker >> 24 | 0x80);
 150                         walker <<= 8;
 151                         walker_len -= 8;
 152                         continue;
 153                 }
 154
 155                 /* decode offset  */
 156                 /* length pair    */
 157                 walker <<= 1;
 158                 if (--walker_len < (big ? 3 : 2))
 159                 {
 160                         if (i >= clen)
 161                                 return -1;
 162                         walker |= (data[i++] & 0xff) << (24 - walker_len);
 163                         walker_len += 8;
 164                 }
 165
 166                 if (big)
 167                 {
 168                         /* offset decoding where offset len is:
 169                            -63: 11111 followed by the lower 6 bits of the value
 170                            64-319: 11110 followed by the lower 8 bits of the value ( value - 64 )
 171                            320-2367: 1110 followed by lower 11 bits of the value ( value - 320 )
 172                            2368-65535: 110 followed by lower 16 bits of the value ( value - 2368 )
 173                          */
 174                         switch (((uint32) walker) >> ((uint32) 29))
 175                         {
 176                                 case 7: /* - 63 */
 177                                         for (; walker_len < 9; walker_len += 8)
 178                                         {
 179                                                 if (i >= clen)
 180                                                         return -1;
 181                                                 walker |= (data[i++] & 0xff) << (24 - walker_len);
 182                                         }
 183                                         walker <<= 3;
 184                                         match_off = ((uint32) walker) >> ((uint32) 26);
 185                                         walker <<= 6;
 186                                         walker_len -= 9;
 187                                         break;
 188
 189                                 case 6: /* 64 - 319 */
 190                                         for (; walker_len < 11; walker_len += 8)
 191                                         {
 192                                                 if (i >= clen)
 193                                                         return -1;
 194                                                 walker |= (data[i++] & 0xff) << (24 - walker_len);
 195                                         }
 196
 197                                         walker <<= 3;
 198                                         match_off = (((uint32) walker) >> ((uint32) 24)) + 64;
 199                                         walker <<= 8;
 200                                         walker_len -= 11;
 201                                         break;
 202
 203                                 case 5:
 204                                 case 4: /* 320 - 2367 */
 205                                         for (; walker_len < 13; walker_len += 8)
 206                                         {
 207                                                 if (i >= clen)
 208                                                         return -1;
 209                                                 walker |= (data[i++] & 0xff) << (24 - walker_len);
 210                                         }
 211
 212                                         walker <<= 2;
 213                                         match_off = (((uint32) walker) >> ((uint32) 21)) + 320;
 214                                         walker <<= 11;
 215                                         walker_len -= 13;
 216                                         break;
 217
 218                                 default:        /* 2368 - 65535 */
 219                                         for (; walker_len < 17; walker_len += 8)
 220                                         {
 221                                                 if (i >= clen)
 222                                                         return -1;
 223                                                 walker |= (data[i++] & 0xff) << (24 - walker_len);
 224                                         }
 225
 226                                         walker <<= 1;
 227                                         match_off = (((uint32) walker) >> ((uint32) 16)) + 2368;
 228                                         walker <<= 16;
 229                                         walker_len -= 17;
 230                                         break;
 231                         }
 232                 }
 233                 else
 234                 {
 235                         /* offset decoding where offset len is:
 236                            -63: 1111 followed by the lower 6 bits of the value
 237                            64-319: 1110 followed by the lower 8 bits of the value ( value - 64 )
 238                            320-8191: 110 followed by the lower 13 bits of the value ( value - 320 )
 239                          */
 240                         switch (((uint32) walker) >> ((uint32) 30))
 241                         {
 242                                 case 3: /* - 63 */
 243                                         if (walker_len < 8)
 244                                         {
 245                                                 if (i >= clen)
 246                                                         return -1;
 247                                                 walker |= (data[i++] & 0xff) << (24 - walker_len);
 248                                                 walker_len += 8;
 249                                         }
 250                                         walker <<= 2;
 251                                         match_off = ((uint32) walker) >> ((uint32) 26);
 252                                         walker <<= 6;
 253                                         walker_len -= 8;
 254                                         break;
 255
 256                                 case 2: /* 64 - 319 */
 257                                         for (; walker_len < 10; walker_len += 8)
 258                                         {
 259                                                 if (i >= clen)
 260                                                         return -1;
 261                                                 walker |= (data[i++] & 0xff) << (24 - walker_len);
 262                                         }
 263
 264                                         walker <<= 2;
 265                                         match_off = (((uint32) walker) >> ((uint32) 24)) + 64;
 266                                         walker <<= 8;
 267                                         walker_len -= 10;
 268                                         break;
 269
 270                                 default:        /* 320 - 8191 */
 271                                         for (; walker_len < 14; walker_len += 8)
 272                                         {
 273                                                 if (i >= clen)
 274                                                         return -1;
 275                                                 walker |= (data[i++] & 0xff) << (24 - walker_len);
 276                                         }
 277
 278                                         match_off = (walker >> 18) + 320;
 279                                         walker <<= 14;
 280                                         walker_len -= 14;
 281                                         break;
 282                         }
 283                 }
 284                 if (walker_len == 0)
 285                 {
 286                         if (i >= clen)
 287                                 return -1;
 288                         walker = data[i++] << 24;
 289                         walker_len = 8;
 290                 }
 291
 292                 /* decode length of match */
 293                 match_len = 0;
 294                 if (walker >= 0)
 295                 {               /* special case - length of 3 is in bit 0 */
 296                         match_len = 3;
 297                         walker <<= 1;
 298                         walker_len--;
 299                 }
 300                 else
 301                 {
 302                         /* this is how it works len of:
 303                            4-7: 10 followed by 2 bits of the value
 304                            8-15: 110 followed by 3 bits of the value
 305                            16-31: 1110 followed by 4 bits of the value
 306                            32-63: .... and so forth
 307                            64-127:
 308                            128-255:
 309                            256-511:
 310                            512-1023:
 311                            1024-2047:
 312                            2048-4095:
 313                            4096-8191:
 314
 315                            i.e. 4097 is encoded as: 111111111110 000000000001
 316                            meaning 4096 + 1...
 317                          */
 318                         match_bits = big ? 14 : 11;     /* 11 or 14 bits of value at most */
 319                         do
 320                         {
 321                                 walker <<= 1;
 322                                 if (--walker_len == 0)
 323                                 {
 324                                         if (i >= clen)
 325                                                 return -1;
 326                                         walker = data[i++] << 24;
 327                                         walker_len = 8;
 328                                 }
 329                                 if (walker >= 0)
 330                                         break;
 331                                 if (--match_bits == 0)
 332                                 {
 333                                         return -1;
 334                                 }
 335                         }
 336                         while (1);
 337                         match_len = (big ? 16 : 13) - match_bits;
 338                         walker <<= 1;
 339                         if (--walker_len < match_len)
 340                         {
 341                                 for (; walker_len < match_len; walker_len += 8)
 342                                 {
 343                                         if (i >= clen)
 344                                         {
 345                                                 return -1;
 346                                         }
 347                                         walker |= (data[i++] & 0xff) << (24 - walker_len);
 348                                 }
 349                         }
 350
 351                         match_bits = match_len;
 352                         match_len =
 353                                 ((walker >> (32 - match_bits)) & (~(-1 << match_bits))) | (1 <<
 354                                                                                            match_bits);
 355                         walker <<= match_bits;
 356                         walker_len -= match_bits;
 357                 }
 358                 if (next_offset + match_len >= RDP_MPPC_DICT_SIZE)
 359                 {
 360                         return -1;
 361                 }
 362                 /* memory areas can overlap - meaning we can't use memXXX functions */
 363                 k = (next_offset - match_off) & (big ? 65535 : 8191);
 364                 do
 365                 {
 366                         dict[next_offset++] = dict[k++];
 367                 }
 368                 while (--match_len != 0);
 369         }
 370         while (1);
 371
 372         /* store history offset */
 373         g_mppc_dict.roff = next_offset;
 374
 375         *roff = old_offset;
 376         *rlen = next_offset - old_offset;
 377
 378         return 0;
 379 }