pd.if.org Git - zpackage/blob - lzma/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 typedef struct {
  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 } lzma_index_coder;
  54
  55
  56 static lzma_ret
  57 index_decode(void *coder_ptr, 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         lzma_index_coder *coder = coder_ptr;
  66
  67         // Similar optimization as in index_encoder.c
  68         const size_t in_start = *in_pos;
  69         lzma_ret ret = LZMA_OK;
  70
  71         while (*in_pos < in_size)
  72         switch (coder->sequence) {
  73         case SEQ_INDICATOR:
  74                 // Return LZMA_DATA_ERROR instead of e.g. LZMA_PROG_ERROR or
  75                 // LZMA_FORMAT_ERROR, because a typical usage case for Index
  76                 // decoder is when parsing the Stream backwards. If seeking
  77                 // backward from the Stream Footer gives us something that
  78                 // doesn't begin with Index Indicator, the file is considered
  79                 // corrupt, not "programming error" or "unrecognized file
  80                 // format". One could argue that the application should
  81                 // verify the Index Indicator before trying to decode the
  82                 // Index, but well, I suppose it is simpler this way.
  83                 if (in[(*in_pos)++] != 0x00)
  84                         return LZMA_DATA_ERROR;
  85
  86                 coder->sequence = SEQ_COUNT;
  87                 break;
  88
  89         case SEQ_COUNT:
  90                 ret = lzma_vli_decode(&coder->count, &coder->pos,
  91                                 in, in_pos, in_size);
  92                 if (ret != LZMA_STREAM_END)
  93                         goto out;
  94
  95                 coder->pos = 0;
  96                 coder->sequence = SEQ_MEMUSAGE;
  97
  98         // Fall through
  99
 100         case SEQ_MEMUSAGE:
 101                 if (lzma_index_memusage(1, coder->count) > coder->memlimit) {
 102                         ret = LZMA_MEMLIMIT_ERROR;
 103                         goto out;
 104                 }
 105
 106                 // Tell the Index handling code how many Records this
 107                 // Index has to allow it to allocate memory more efficiently.
 108                 lzma_index_prealloc(coder->index, coder->count);
 109
 110                 ret = LZMA_OK;
 111                 coder->sequence = coder->count == 0
 112                                 ? SEQ_PADDING_INIT : SEQ_UNPADDED;
 113                 break;
 114
 115         case SEQ_UNPADDED:
 116         case SEQ_UNCOMPRESSED: {
 117                 lzma_vli *size = coder->sequence == SEQ_UNPADDED
 118                                 ? &coder->unpadded_size
 119                                 : &coder->uncompressed_size;
 120
 121                 ret = lzma_vli_decode(size, &coder->pos,
 122                                 in, in_pos, in_size);
 123                 if (ret != LZMA_STREAM_END)
 124                         goto out;
 125
 126                 ret = LZMA_OK;
 127                 coder->pos = 0;
 128
 129                 if (coder->sequence == SEQ_UNPADDED) {
 130                         // Validate that encoded Unpadded Size isn't too small
 131                         // or too big.
 132                         if (coder->unpadded_size < UNPADDED_SIZE_MIN
 133                                         || coder->unpadded_size
 134                                                 > UNPADDED_SIZE_MAX)
 135                                 return LZMA_DATA_ERROR;
 136
 137                         coder->sequence = SEQ_UNCOMPRESSED;
 138                 } else {
 139                         // Add the decoded Record to the Index.
 140                         return_if_error(lzma_index_append(
 141                                         coder->index, allocator,
 142                                         coder->unpadded_size,
 143                                         coder->uncompressed_size));
 144
 145                         // Check if this was the last Record.
 146                         coder->sequence = --coder->count == 0
 147                                         ? SEQ_PADDING_INIT
 148                                         : SEQ_UNPADDED;
 149                 }
 150
 151                 break;
 152         }
 153
 154         case SEQ_PADDING_INIT:
 155                 coder->pos = lzma_index_padding_size(coder->index);
 156                 coder->sequence = SEQ_PADDING;
 157
 158         // Fall through
 159
 160         case SEQ_PADDING:
 161                 if (coder->pos > 0) {
 162                         --coder->pos;
 163                         if (in[(*in_pos)++] != 0x00)
 164                                 return LZMA_DATA_ERROR;
 165
 166                         break;
 167                 }
 168
 169                 // Finish the CRC32 calculation.
 170                 coder->crc32 = lzma_crc32(in + in_start,
 171                                 *in_pos - in_start, coder->crc32);
 172
 173                 coder->sequence = SEQ_CRC32;
 174
 175         // Fall through
 176
 177         case SEQ_CRC32:
 178                 do {
 179                         if (*in_pos == in_size)
 180                                 return LZMA_OK;
 181
 182                         if (((coder->crc32 >> (coder->pos * 8)) & 0xFF)
 183                                         != in[(*in_pos)++])
 184                                 return LZMA_DATA_ERROR;
 185
 186                 } while (++coder->pos < 4);
 187
 188                 // Decoding was successful, now we can let the application
 189                 // see the decoded Index.
 190                 *coder->index_ptr = coder->index;
 191
 192                 // Make index NULL so we don't free it unintentionally.
 193                 coder->index = NULL;
 194
 195                 return LZMA_STREAM_END;
 196
 197         default:
 198                 assert(0);
 199                 return LZMA_PROG_ERROR;
 200         }
 201
 202 out:
 203         // Update the CRC32,
 204         coder->crc32 = lzma_crc32(in + in_start,
 205                         *in_pos - in_start, coder->crc32);
 206
 207         return ret;
 208 }
 209
 210
 211 static void
 212 index_decoder_end(void *coder_ptr, const lzma_allocator *allocator)
 213 {
 214         lzma_index_coder *coder = coder_ptr;
 215         lzma_index_end(coder->index, allocator);
 216         lzma_free(coder, allocator);
 217         return;
 218 }
 219
 220
 221 static lzma_ret
 222 index_decoder_memconfig(void *coder_ptr, uint64_t *memusage,
 223                 uint64_t *old_memlimit, uint64_t new_memlimit)
 224 {
 225         lzma_index_coder *coder = coder_ptr;
 226
 227         *memusage = lzma_index_memusage(1, coder->count);
 228         *old_memlimit = coder->memlimit;
 229
 230         if (new_memlimit != 0) {
 231                 if (new_memlimit < *memusage)
 232                         return LZMA_MEMLIMIT_ERROR;
 233
 234                 coder->memlimit = new_memlimit;
 235         }
 236
 237         return LZMA_OK;
 238 }
 239
 240
 241 static lzma_ret
 242 index_decoder_reset(lzma_index_coder *coder, const lzma_allocator *allocator,
 243                 lzma_index **i, uint64_t memlimit)
 244 {
 245         // Remember the pointer given by the application. We will set it
 246         // to point to the decoded Index only if decoding is successful.
 247         // Before that, keep it NULL so that applications can always safely
 248         // pass it to lzma_index_end() no matter did decoding succeed or not.
 249         coder->index_ptr = i;
 250         *i = NULL;
 251
 252         // We always allocate a new lzma_index.
 253         coder->index = lzma_index_init(allocator);
 254         if (coder->index == NULL)
 255                 return LZMA_MEM_ERROR;
 256
 257         // Initialize the rest.
 258         coder->sequence = SEQ_INDICATOR;
 259         coder->memlimit = my_max(1, memlimit);
 260         coder->count = 0; // Needs to be initialized due to _memconfig().
 261         coder->pos = 0;
 262         coder->crc32 = 0;
 263
 264         return LZMA_OK;
 265 }
 266
 267
 268 static lzma_ret
 269 index_decoder_init(lzma_next_coder *next, const lzma_allocator *allocator,
 270                 lzma_index **i, uint64_t memlimit)
 271 {
 272         lzma_next_coder_init(&index_decoder_init, next, allocator);
 273
 274         if (i == NULL)
 275                 return LZMA_PROG_ERROR;
 276
 277         lzma_index_coder *coder = next->coder;
 278         if (coder == NULL) {
 279                 coder = lzma_alloc(sizeof(lzma_index_coder), allocator);
 280                 if (coder == NULL)
 281                         return LZMA_MEM_ERROR;
 282
 283                 next->coder = coder;
 284                 next->code = &index_decode;
 285                 next->end = &index_decoder_end;
 286                 next->memconfig = &index_decoder_memconfig;
 287                 coder->index = NULL;
 288         } else {
 289                 lzma_index_end(coder->index, allocator);
 290         }
 291
 292         return index_decoder_reset(coder, allocator, i, memlimit);
 293 }
 294
 295
 296 extern LZMA_API(lzma_ret)
 297 lzma_index_decoder(lzma_stream *strm, lzma_index **i, uint64_t memlimit)
 298 {
 299         lzma_next_strm_init(index_decoder_init, strm, i, memlimit);
 300
 301         strm->internal->supported_actions[LZMA_RUN] = true;
 302         strm->internal->supported_actions[LZMA_FINISH] = true;
 303
 304         return LZMA_OK;
 305 }
 306
 307
 308 extern LZMA_API(lzma_ret)
 309 lzma_index_buffer_decode(lzma_index **i, uint64_t *memlimit,
 310                 const lzma_allocator *allocator,
 311                 const uint8_t *in, size_t *in_pos, size_t in_size)
 312 {
 313         // Sanity checks
 314         if (i == NULL || memlimit == NULL
 315                         || in == NULL || in_pos == NULL || *in_pos > in_size)
 316                 return LZMA_PROG_ERROR;
 317
 318         // Initialize the decoder.
 319         lzma_index_coder coder;
 320         return_if_error(index_decoder_reset(&coder, allocator, i, *memlimit));
 321
 322         // Store the input start position so that we can restore it in case
 323         // of an error.
 324         const size_t in_start = *in_pos;
 325
 326         // Do the actual decoding.
 327         lzma_ret ret = index_decode(&coder, allocator, in, in_pos, in_size,
 328                         NULL, NULL, 0, LZMA_RUN);
 329
 330         if (ret == LZMA_STREAM_END) {
 331                 ret = LZMA_OK;
 332         } else {
 333                 // Something went wrong, free the Index structure and restore
 334                 // the input position.
 335                 lzma_index_end(coder.index, allocator);
 336                 *in_pos = in_start;
 337
 338                 if (ret == LZMA_OK) {
 339                         // The input is truncated or otherwise corrupt.
 340                         // Use LZMA_DATA_ERROR instead of LZMA_BUF_ERROR
 341                         // like lzma_vli_decode() does in single-call mode.
 342                         ret = LZMA_DATA_ERROR;
 343
 344                 } else if (ret == LZMA_MEMLIMIT_ERROR) {
 345                         // Tell the caller how much memory would have
 346                         // been needed.
 347                         *memlimit = lzma_index_memusage(1, coder.count);
 348                 }
 349         }
 350
 351         return ret;
 352 }