external/public-domain/xz/dist/src/liblzma/common/index_decoder.c

   1 ///////////////////////////////////////////////////////////////////////////////
   2 //
   3 /// \file       index_decoder.c
   4 /// \brief      Decodes the Index field
   5 //
   6 //  Author:     Lasse Collin
   7 //
   8 //  This file has been put into the public domain.
   9 //  You can do whatever you want with this file.
  10 //
  11 ///////////////////////////////////////////////////////////////////////////////
  12
  13 #include "index.h"
  14 #include "check.h"
  15
  16
  17 struct lzma_coder_s {
  18         enum {
  19                 SEQ_INDICATOR,
  20                 SEQ_COUNT,
  21                 SEQ_MEMUSAGE,
  22                 SEQ_UNPADDED,
  23                 SEQ_UNCOMPRESSED,
  24                 SEQ_PADDING_INIT,
  25                 SEQ_PADDING,
  26                 SEQ_CRC32,
  27         } sequence;
  28
  29         /// Memory usage limit
  30         uint64_t memlimit;
  31
  32         /// Target Index
  33         lzma_index *index;
  34
  35         /// Pointer give by the application, which is set after
  36         /// successful decoding.
  37         lzma_index **index_ptr;
  38
  39         /// Number of Records left to decode.
  40         lzma_vli count;
  41
  42         /// The most recent Unpadded Size field
  43         lzma_vli unpadded_size;
  44
  45         /// The most recent Uncompressed Size field
  46         lzma_vli uncompressed_size;
  47
  48         /// Position in integers
  49         size_t pos;
  50
  51         /// CRC32 of the List of Records field
  52         uint32_t crc32;
  53 };
  54
  55
  56 static lzma_ret
  57 index_decode(lzma_coder *coder, const lzma_allocator *allocator,
  58                 const uint8_t *restrict in, size_t *restrict in_pos,
  59                 size_t in_size,
  60                 uint8_t *restrict out lzma_attribute((__unused__)),
  61                 size_t *restrict out_pos lzma_attribute((__unused__)),
  62                 size_t out_size lzma_attribute((__unused__)),
  63                 lzma_action action lzma_attribute((__unused__)))
  64 {
  65         // Similar optimization as in index_encoder.c
  66         const size_t in_start = *in_pos;
  67         lzma_ret ret = LZMA_OK;
  68
  69         while (*in_pos < in_size)
  70         switch (coder->sequence) {
  71         case SEQ_INDICATOR:
  72                 // Return LZMA_DATA_ERROR instead of e.g. LZMA_PROG_ERROR or
  73                 // LZMA_FORMAT_ERROR, because a typical usage case for Index
  74                 // decoder is when parsing the Stream backwards. If seeking
  75                 // backward from the Stream Footer gives us something that
  76                 // doesn't begin with Index Indicator, the file is considered
  77                 // corrupt, not "programming error" or "unrecognized file
  78                 // format". One could argue that the application should
  79                 // verify the Index Indicator before trying to decode the
  80                 // Index, but well, I suppose it is simpler this way.
  81                 if (in[(*in_pos)++] != 0x00)
  82                         return LZMA_DATA_ERROR;
  83
  84                 coder->sequence = SEQ_COUNT;
  85                 break;
  86
  87         case SEQ_COUNT:
  88                 ret = lzma_vli_decode(&coder->count, &coder->pos,
  89                                 in, in_pos, in_size);
  90                 if (ret != LZMA_STREAM_END)
  91                         goto out;
  92
  93                 coder->pos = 0;
  94                 coder->sequence = SEQ_MEMUSAGE;
  95
  96         // Fall through
  97
  98         case SEQ_MEMUSAGE:
  99                 if (lzma_index_memusage(1, coder->count) > coder->memlimit) {
 100                         ret = LZMA_MEMLIMIT_ERROR;
 101                         goto out;
 102                 }
 103
 104                 // Tell the Index handling code how many Records this
 105                 // Index has to allow it to allocate memory more efficiently.
 106                 lzma_index_prealloc(coder->index, coder->count);
 107
 108                 ret = LZMA_OK;
 109                 coder->sequence = coder->count == 0
 110                                 ? SEQ_PADDING_INIT : SEQ_UNPADDED;
 111                 break;
 112
 113         case SEQ_UNPADDED:
 114         case SEQ_UNCOMPRESSED: {
 115                 lzma_vli *size = coder->sequence == SEQ_UNPADDED
 116                                 ? &coder->unpadded_size
 117                                 : &coder->uncompressed_size;
 118
 119                 ret = lzma_vli_decode(size, &coder->pos,
 120                                 in, in_pos, in_size);
 121                 if (ret != LZMA_STREAM_END)
 122                         goto out;
 123
 124                 ret = LZMA_OK;
 125                 coder->pos = 0;
 126
 127                 if (coder->sequence == SEQ_UNPADDED) {
 128                         // Validate that encoded Unpadded Size isn't too small
 129                         // or too big.
 130                         if (coder->unpadded_size < UNPADDED_SIZE_MIN
 131                                         || coder->unpadded_size
 132                                                 > UNPADDED_SIZE_MAX)
 133                                 return LZMA_DATA_ERROR;
 134
 135                         coder->sequence = SEQ_UNCOMPRESSED;
 136                 } else {
 137                         // Add the decoded Record to the Index.
 138                         return_if_error(lzma_index_append(
 139                                         coder->index, allocator,
 140                                         coder->unpadded_size,
 141                                         coder->uncompressed_size));
 142
 143                         // Check if this was the last Record.
 144                         coder->sequence = --coder->count == 0
 145                                         ? SEQ_PADDING_INIT
 146                                         : SEQ_UNPADDED;
 147                 }
 148
 149                 break;
 150         }
 151
 152         case SEQ_PADDING_INIT:
 153                 coder->pos = lzma_index_padding_size(coder->index);
 154                 coder->sequence = SEQ_PADDING;
 155
 156         // Fall through
 157
 158         case SEQ_PADDING:
 159                 if (coder->pos > 0) {
 160                         --coder->pos;
 161                         if (in[(*in_pos)++] != 0x00)
 162                                 return LZMA_DATA_ERROR;
 163
 164                         break;
 165                 }
 166
 167                 // Finish the CRC32 calculation.
 168                 coder->crc32 = lzma_crc32(in + in_start,
 169                                 *in_pos - in_start, coder->crc32);
 170
 171                 coder->sequence = SEQ_CRC32;
 172
 173         // Fall through
 174
 175         case SEQ_CRC32:
 176                 do {
 177                         if (*in_pos == in_size)
 178                                 return LZMA_OK;
 179
 180                         if (((coder->crc32 >> (coder->pos * 8)) & 0xFF)
 181                                         != in[(*in_pos)++])
 182                                 return LZMA_DATA_ERROR;
 183
 184                 } while (++coder->pos < 4);
 185
 186                 // Decoding was successful, now we can let the application
 187                 // see the decoded Index.
 188                 *coder->index_ptr = coder->index;
 189
 190                 // Make index NULL so we don't free it unintentionally.
 191                 coder->index = NULL;
 192
 193                 return LZMA_STREAM_END;
 194
 195         default:
 196                 assert(0);
 197                 return LZMA_PROG_ERROR;
 198         }
 199
 200 out:
 201         // Update the CRC32,
 202         coder->crc32 = lzma_crc32(in + in_start,
 203                         *in_pos - in_start, coder->crc32);
 204
 205         return ret;
 206 }
 207
 208
 209 static void
 210 index_decoder_end(lzma_coder *coder, const lzma_allocator *allocator)
 211 {
 212         lzma_index_end(coder->index, allocator);
 213         lzma_free(coder, allocator);
 214         return;
 215 }
 216
 217
 218 static lzma_ret
 219 index_decoder_memconfig(lzma_coder *coder, uint64_t *memusage,
 220                 uint64_t *old_memlimit, uint64_t new_memlimit)
 221 {
 222         *memusage = lzma_index_memusage(1, coder->count);
 223         *old_memlimit = coder->memlimit;
 224
 225         if (new_memlimit != 0) {
 226                 if (new_memlimit < *memusage)
 227                         return LZMA_MEMLIMIT_ERROR;
 228
 229                 coder->memlimit = new_memlimit;
 230         }
 231
 232         return LZMA_OK;
 233 }
 234
 235
 236 static lzma_ret
 237 index_decoder_reset(lzma_coder *coder, const lzma_allocator *allocator,
 238                 lzma_index **i, uint64_t memlimit)
 239 {
 240         // Remember the pointer given by the application. We will set it
 241         // to point to the decoded Index only if decoding is successful.
 242         // Before that, keep it NULL so that applications can always safely
 243         // pass it to lzma_index_end() no matter did decoding succeed or not.
 244         coder->index_ptr = i;
 245         *i = NULL;
 246
 247         // We always allocate a new lzma_index.
 248         coder->index = lzma_index_init(allocator);
 249         if (coder->index == NULL)
 250                 return LZMA_MEM_ERROR;
 251
 252         // Initialize the rest.
 253         coder->sequence = SEQ_INDICATOR;
 254         coder->memlimit = memlimit;
 255         coder->count = 0; // Needs to be initialized due to _memconfig().
 256         coder->pos = 0;
 257         coder->crc32 = 0;
 258
 259         return LZMA_OK;
 260 }
 261
 262
 263 static lzma_ret
 264 index_decoder_init(lzma_next_coder *next, const lzma_allocator *allocator,
 265                 lzma_index **i, uint64_t memlimit)
 266 {
 267         lzma_next_coder_init(&index_decoder_init, next, allocator);
 268
 269         if (i == NULL || memlimit == 0)
 270                 return LZMA_PROG_ERROR;
 271
 272         if (next->coder == NULL) {
 273                 next->coder = lzma_alloc(sizeof(lzma_coder), allocator);
 274                 if (next->coder == NULL)
 275                         return LZMA_MEM_ERROR;
 276
 277                 next->code = &index_decode;
 278                 next->end = &index_decoder_end;
 279                 next->memconfig = &index_decoder_memconfig;
 280                 next->coder->index = NULL;
 281         } else {
 282                 lzma_index_end(next->coder->index, allocator);
 283         }
 284
 285         return index_decoder_reset(next->coder, allocator, i, memlimit);
 286 }
 287
 288
 289 extern LZMA_API(lzma_ret)
 290 lzma_index_decoder(lzma_stream *strm, lzma_index **i, uint64_t memlimit)
 291 {
 292         lzma_next_strm_init(index_decoder_init, strm, i, memlimit);
 293
 294         strm->internal->supported_actions[LZMA_RUN] = true;
 295         strm->internal->supported_actions[LZMA_FINISH] = true;
 296
 297         return LZMA_OK;
 298 }
 299
 300
 301 extern LZMA_API(lzma_ret)
 302 lzma_index_buffer_decode(lzma_index **i, uint64_t *memlimit,
 303                 const lzma_allocator *allocator,
 304                 const uint8_t *in, size_t *in_pos, size_t in_size)
 305 {
 306         // Sanity checks
 307         if (i == NULL || memlimit == NULL
 308                         || in == NULL || in_pos == NULL || *in_pos > in_size)
 309                 return LZMA_PROG_ERROR;
 310
 311         // Initialize the decoder.
 312         lzma_coder coder;
 313         return_if_error(index_decoder_reset(&coder, allocator, i, *memlimit));
 314
 315         // Store the input start position so that we can restore it in case
 316         // of an error.
 317         const size_t in_start = *in_pos;
 318
 319         // Do the actual decoding.
 320         lzma_ret ret = index_decode(&coder, allocator, in, in_pos, in_size,
 321                         NULL, NULL, 0, LZMA_RUN);
 322
 323         if (ret == LZMA_STREAM_END) {
 324                 ret = LZMA_OK;
 325         } else {
 326                 // Something went wrong, free the Index structure and restore
 327                 // the input position.
 328                 lzma_index_end(coder.index, allocator);
 329                 *in_pos = in_start;
 330
 331                 if (ret == LZMA_OK) {
 332                         // The input is truncated or otherwise corrupt.
 333                         // Use LZMA_DATA_ERROR instead of LZMA_BUF_ERROR
 334                         // like lzma_vli_decode() does in single-call mode.
 335                         ret = LZMA_DATA_ERROR;
 336
 337                 } else if (ret == LZMA_MEMLIMIT_ERROR) {
 338                         // Tell the caller how much memory would have
 339                         // been needed.
 340                         *memlimit = lzma_index_memusage(1, coder.count);
 341                 }
 342         }
 343
 344         return ret;
 345 }