src/liblzma/common/lzip_decoder.c

   1 // SPDX-License-Identifier: 0BSD
   2
   3 ///////////////////////////////////////////////////////////////////////////////
   4 //
   5 /// \file       lzip_decoder.c
   6 /// \brief      Decodes .lz (lzip) files
   7 //
   8 //  Author:     Michał Górny
   9 //              Lasse Collin
  10 //
  11 ///////////////////////////////////////////////////////////////////////////////
  12
  13 #include "lzip_decoder.h"
  14 #include "lzma_decoder.h"
  15 #include "check.h"
  16
  17
  18 // .lz format version 0 lacks the 64-bit Member size field in the footer.
  19 #define LZIP_V0_FOOTER_SIZE 12
  20 #define LZIP_V1_FOOTER_SIZE 20
  21 #define LZIP_FOOTER_SIZE_MAX LZIP_V1_FOOTER_SIZE
  22
  23 // lc/lp/pb are hardcoded in the .lz format.
  24 #define LZIP_LC 3
  25 #define LZIP_LP 0
  26 #define LZIP_PB 2
  27
  28
  29 typedef struct {
  30         enum {
  31                 SEQ_ID_STRING,
  32                 SEQ_VERSION,
  33                 SEQ_DICT_SIZE,
  34                 SEQ_CODER_INIT,
  35                 SEQ_LZMA_STREAM,
  36                 SEQ_MEMBER_FOOTER,
  37         } sequence;
  38
  39         /// .lz member format version
  40         uint32_t version;
  41
  42         /// CRC32 of the uncompressed data in the .lz member
  43         uint32_t crc32;
  44
  45         /// Uncompressed size of the .lz member
  46         uint64_t uncompressed_size;
  47
  48         /// Compressed size of the .lz member
  49         uint64_t member_size;
  50
  51         /// Memory usage limit
  52         uint64_t memlimit;
  53
  54         /// Amount of memory actually needed
  55         uint64_t memusage;
  56
  57         /// If true, LZMA_GET_CHECK is returned after decoding the header
  58         /// fields. As all files use CRC32 this is redundant but it's
  59         /// implemented anyway since the initialization functions supports
  60         /// all other flags in addition to LZMA_TELL_ANY_CHECK.
  61         bool tell_any_check;
  62
  63         /// If true, we won't calculate or verify the CRC32 of
  64         /// the uncompressed data.
  65         bool ignore_check;
  66
  67         /// If true, we will decode concatenated .lz members and stop if
  68         /// non-.lz data is seen after at least one member has been
  69         /// successfully decoded.
  70         bool concatenated;
  71
  72         /// When decoding concatenated .lz members, this is true as long as
  73         /// we are decoding the first .lz member. This is needed to avoid
  74         /// incorrect LZMA_FORMAT_ERROR in case there is non-.lz data at
  75         /// the end of the file.
  76         bool first_member;
  77
  78         /// Reading position in the header and footer fields
  79         size_t pos;
  80
  81         /// Buffer to hold the .lz footer fields
  82         uint8_t buffer[LZIP_FOOTER_SIZE_MAX];
  83
  84         /// Options decoded from the .lz header that needed to initialize
  85         /// the LZMA1 decoder.
  86         lzma_options_lzma options;
  87
  88         /// LZMA1 decoder
  89         lzma_next_coder lzma_decoder;
  90
  91 } lzma_lzip_coder;
  92
  93
  94 static lzma_ret
  95 lzip_decode(void *coder_ptr, const lzma_allocator *allocator,
  96                 const uint8_t *restrict in, size_t *restrict in_pos,
  97                 size_t in_size, uint8_t *restrict out,
  98                 size_t *restrict out_pos, size_t out_size, lzma_action action)
  99 {
 100         lzma_lzip_coder *coder = coder_ptr;
 101
 102         while (true)
 103         switch (coder->sequence) {
 104         case SEQ_ID_STRING: {
 105                 // The "ID string" or magic bytes are "LZIP" in US-ASCII.
 106                 const uint8_t lzip_id_string[4] = { 0x4C, 0x5A, 0x49, 0x50 };
 107
 108                 while (coder->pos < sizeof(lzip_id_string)) {
 109                         if (*in_pos >= in_size) {
 110                                 // If we are on the 2nd+ concatenated member
 111                                 // and the input ends before we can read
 112                                 // the magic bytes, we discard the bytes that
 113                                 // were already read (up to 3) and finish.
 114                                 // See the reasoning below.
 115                                 return !coder->first_member
 116                                                 && action == LZMA_FINISH
 117                                         ? LZMA_STREAM_END : LZMA_OK;
 118                         }
 119
 120                         if (in[*in_pos] != lzip_id_string[coder->pos]) {
 121                                 // The .lz format allows putting non-.lz data
 122                                 // at the end of the file. If we have seen
 123                                 // at least one valid .lz member already,
 124                                 // then we won't consume the byte at *in_pos
 125                                 // and will return LZMA_STREAM_END. This way
 126                                 // apps can easily locate and read the non-.lz
 127                                 // data after the .lz member(s).
 128                                 //
 129                                 // NOTE: If the first 1-3 bytes of the non-.lz
 130                                 // data match the .lz ID string then the first
 131                                 // 1-3 bytes of the junk will get ignored by
 132                                 // us. If apps want to properly locate the
 133                                 // trailing data they must ensure that the
 134                                 // first byte of their custom data isn't the
 135                                 // same as the first byte of .lz ID string.
 136                                 // With the liblzma API we cannot rewind the
 137                                 // input position across calls to lzma_code().
 138                                 return !coder->first_member
 139                                         ? LZMA_STREAM_END : LZMA_FORMAT_ERROR;
 140                         }
 141
 142                         ++*in_pos;
 143                         ++coder->pos;
 144                 }
 145
 146                 coder->pos = 0;
 147
 148                 coder->crc32 = 0;
 149                 coder->uncompressed_size = 0;
 150                 coder->member_size = sizeof(lzip_id_string);
 151
 152                 coder->sequence = SEQ_VERSION;
 153         }
 154
 155         // Fall through
 156
 157         case SEQ_VERSION:
 158                 if (*in_pos >= in_size)
 159                         return LZMA_OK;
 160
 161                 coder->version = in[(*in_pos)++];
 162
 163                 // We support version 0 and unextended version 1.
 164                 if (coder->version > 1)
 165                         return LZMA_OPTIONS_ERROR;
 166
 167                 ++coder->member_size;
 168                 coder->sequence = SEQ_DICT_SIZE;
 169
 170                 // .lz versions 0 and 1 use CRC32 as the integrity check
 171                 // so if the application wanted to know that
 172                 // (LZMA_TELL_ANY_CHECK) we can tell it now.
 173                 if (coder->tell_any_check)
 174                         return LZMA_GET_CHECK;
 175
 176         // Fall through
 177
 178         case SEQ_DICT_SIZE: {
 179                 if (*in_pos >= in_size)
 180                         return LZMA_OK;
 181
 182                 const uint32_t ds = in[(*in_pos)++];
 183                 ++coder->member_size;
 184
 185                 // The five lowest bits are for the base-2 logarithm of
 186                 // the dictionary size and the highest three bits are
 187                 // the fractional part (0/16 to 7/16) that will be
 188                 // subtracted to get the final value.
 189                 //
 190                 // For example, with 0xB5:
 191                 //     b2log = 21
 192                 //     fracnum = 5
 193                 //     dict_size = 2^21 - 2^21 * 5 / 16 = 1408 KiB
 194                 const uint32_t b2log = ds & 0x1F;
 195                 const uint32_t fracnum = ds >> 5;
 196
 197                 // The format versions 0 and 1 allow dictionary size in the
 198                 // range [4 KiB, 512 MiB].
 199                 if (b2log < 12 || b2log > 29 || (b2log == 12 && fracnum > 0))
 200                         return LZMA_DATA_ERROR;
 201
 202                 //   2^[b2log] - 2^[b2log] * [fracnum] / 16
 203                 // = 2^[b2log] - [fracnum] * 2^([b2log] - 4)
 204                 coder->options.dict_size = (UINT32_C(1) << b2log)
 205                                 - (fracnum << (b2log - 4));
 206
 207                 assert(coder->options.dict_size >= 4096);
 208                 assert(coder->options.dict_size <= (UINT32_C(512) << 20));
 209
 210                 coder->options.preset_dict = NULL;
 211                 coder->options.lc = LZIP_LC;
 212                 coder->options.lp = LZIP_LP;
 213                 coder->options.pb = LZIP_PB;
 214
 215                 // Calculate the memory usage.
 216                 coder->memusage = lzma_lzma_decoder_memusage(&coder->options)
 217                                 + LZMA_MEMUSAGE_BASE;
 218
 219                 // Initialization is a separate step because if we return
 220                 // LZMA_MEMLIMIT_ERROR we need to be able to restart after
 221                 // the memlimit has been increased.
 222                 coder->sequence = SEQ_CODER_INIT;
 223         }
 224
 225         // Fall through
 226
 227         case SEQ_CODER_INIT: {
 228                 if (coder->memusage > coder->memlimit)
 229                         return LZMA_MEMLIMIT_ERROR;
 230
 231                 const lzma_filter_info filters[2] = {
 232                         {
 233                                 .id = LZMA_FILTER_LZMA1,
 234                                 .init = &lzma_lzma_decoder_init,
 235                                 .options = &coder->options,
 236                         }, {
 237                                 .init = NULL,
 238                         }
 239                 };
 240
 241                 return_if_error(lzma_next_filter_init(&coder->lzma_decoder,
 242                                 allocator, filters));
 243
 244                 coder->crc32 = 0;
 245                 coder->sequence = SEQ_LZMA_STREAM;
 246         }
 247
 248         // Fall through
 249
 250         case SEQ_LZMA_STREAM: {
 251                 const size_t in_start = *in_pos;
 252                 const size_t out_start = *out_pos;
 253
 254                 const lzma_ret ret = coder->lzma_decoder.code(
 255                                 coder->lzma_decoder.coder, allocator,
 256                                 in, in_pos, in_size, out, out_pos, out_size,
 257                                 action);
 258
 259                 const size_t out_used = *out_pos - out_start;
 260
 261                 coder->member_size += *in_pos - in_start;
 262                 coder->uncompressed_size += out_used;
 263
 264                 // Don't update the CRC32 if the integrity check will be
 265                 // ignored or if there was no new output. The latter is
 266                 // important in case out == NULL to avoid null pointer + 0
 267                 // which is undefined behavior.
 268                 if (!coder->ignore_check && out_used > 0)
 269                         coder->crc32 = lzma_crc32(out + out_start, out_used,
 270                                         coder->crc32);
 271
 272                 if (ret != LZMA_STREAM_END)
 273                         return ret;
 274
 275                 coder->sequence = SEQ_MEMBER_FOOTER;
 276         }
 277
 278         // Fall through
 279
 280         case SEQ_MEMBER_FOOTER: {
 281                 // The footer of .lz version 0 lacks the Member size field.
 282                 // This is the only difference between version 0 and
 283                 // unextended version 1 formats.
 284                 const size_t footer_size = coder->version == 0
 285                                 ? LZIP_V0_FOOTER_SIZE
 286                                 : LZIP_V1_FOOTER_SIZE;
 287
 288                 // Copy the CRC32, Data size, and Member size fields to
 289                 // the internal buffer.
 290                 lzma_bufcpy(in, in_pos, in_size, coder->buffer, &coder->pos,
 291                                 footer_size);
 292
 293                 // Return if we didn't get the whole footer yet.
 294                 if (coder->pos < footer_size)
 295                         return LZMA_OK;
 296
 297                 coder->pos = 0;
 298                 coder->member_size += footer_size;
 299
 300                 // Check that the footer fields match the observed data.
 301                 if (!coder->ignore_check
 302                                 && coder->crc32 != read32le(&coder->buffer[0]))
 303                         return LZMA_DATA_ERROR;
 304
 305                 if (coder->uncompressed_size != read64le(&coder->buffer[4]))
 306                         return LZMA_DATA_ERROR;
 307
 308                 if (coder->version > 0) {
 309                         // .lz version 0 has no Member size field.
 310                         if (coder->member_size != read64le(&coder->buffer[12]))
 311                                 return LZMA_DATA_ERROR;
 312                 }
 313
 314                 // Decoding is finished if we weren't requested to decode
 315                 // more than one .lz member.
 316                 if (!coder->concatenated)
 317                         return LZMA_STREAM_END;
 318
 319                 coder->first_member = false;
 320                 coder->sequence = SEQ_ID_STRING;
 321                 break;
 322         }
 323
 324         default:
 325                 assert(0);
 326                 return LZMA_PROG_ERROR;
 327         }
 328
 329         // Never reached
 330 }
 331
 332
 333 static void
 334 lzip_decoder_end(void *coder_ptr, const lzma_allocator *allocator)
 335 {
 336         lzma_lzip_coder *coder = coder_ptr;
 337         lzma_next_end(&coder->lzma_decoder, allocator);
 338         lzma_free(coder, allocator);
 339         return;
 340 }
 341
 342
 343 static lzma_check
 344 lzip_decoder_get_check(const void *coder_ptr lzma_attribute((__unused__)))
 345 {
 346         return LZMA_CHECK_CRC32;
 347 }
 348
 349
 350 static lzma_ret
 351 lzip_decoder_memconfig(void *coder_ptr, uint64_t *memusage,
 352                 uint64_t *old_memlimit, uint64_t new_memlimit)
 353 {
 354         lzma_lzip_coder *coder = coder_ptr;
 355
 356         *memusage = coder->memusage;
 357         *old_memlimit = coder->memlimit;
 358
 359         if (new_memlimit != 0) {
 360                 if (new_memlimit < coder->memusage)
 361                         return LZMA_MEMLIMIT_ERROR;
 362
 363                 coder->memlimit = new_memlimit;
 364         }
 365
 366         return LZMA_OK;
 367 }
 368
 369
 370 extern lzma_ret
 371 lzma_lzip_decoder_init(
 372                 lzma_next_coder *next, const lzma_allocator *allocator,
 373                 uint64_t memlimit, uint32_t flags)
 374 {
 375         lzma_next_coder_init(&lzma_lzip_decoder_init, next, allocator);
 376
 377         if (flags & ~LZMA_SUPPORTED_FLAGS)
 378                 return LZMA_OPTIONS_ERROR;
 379
 380         lzma_lzip_coder *coder = next->coder;
 381         if (coder == NULL) {
 382                 coder = lzma_alloc(sizeof(lzma_lzip_coder), allocator);
 383                 if (coder == NULL)
 384                         return LZMA_MEM_ERROR;
 385
 386                 next->coder = coder;
 387                 next->code = &lzip_decode;
 388                 next->end = &lzip_decoder_end;
 389                 next->get_check = &lzip_decoder_get_check;
 390                 next->memconfig = &lzip_decoder_memconfig;
 391
 392                 coder->lzma_decoder = LZMA_NEXT_CODER_INIT;
 393         }
 394
 395         coder->sequence = SEQ_ID_STRING;
 396         coder->memlimit = my_max(1, memlimit);
 397         coder->memusage = LZMA_MEMUSAGE_BASE;
 398         coder->tell_any_check = (flags & LZMA_TELL_ANY_CHECK) != 0;
 399         coder->ignore_check = (flags & LZMA_IGNORE_CHECK) != 0;
 400         coder->concatenated = (flags & LZMA_CONCATENATED) != 0;
 401         coder->first_member = true;
 402         coder->pos = 0;
 403
 404         return LZMA_OK;
 405 }
 406
 407
 408 extern LZMA_API(lzma_ret)
 409 lzma_lzip_decoder(lzma_stream *strm, uint64_t memlimit, uint32_t flags)
 410 {
 411         lzma_next_strm_init(lzma_lzip_decoder_init, strm, memlimit, flags);
 412
 413         strm->internal->supported_actions[LZMA_RUN] = true;
 414         strm->internal->supported_actions[LZMA_FINISH] = true;
 415
 416         return LZMA_OK;
 417 }