src/liblzma/common/block_decoder.c

   1 ///////////////////////////////////////////////////////////////////////////////
   2 //
   3 /// \file       block_decoder.c
   4 /// \brief      Decodes .xz Blocks
   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 "block_decoder.h"
  14 #include "filter_decoder.h"
  15 #include "check.h"
  16
  17
  18 struct lzma_coder_s {
  19         enum {
  20                 SEQ_CODE,
  21                 SEQ_PADDING,
  22                 SEQ_CHECK,
  23         } sequence;
  24
  25         /// The filters in the chain; initialized with lzma_raw_decoder_init().
  26         lzma_next_coder next;
  27
  28         /// Decoding options; we also write Compressed Size and Uncompressed
  29         /// Size back to this structure when the decoding has been finished.
  30         lzma_block *block;
  31
  32         /// Compressed Size calculated while decoding
  33         lzma_vli compressed_size;
  34
  35         /// Uncompressed Size calculated while decoding
  36         lzma_vli uncompressed_size;
  37
  38         /// Maximum allowed Compressed Size; this takes into account the
  39         /// size of the Block Header and Check fields when Compressed Size
  40         /// is unknown.
  41         lzma_vli compressed_limit;
  42
  43         /// Position when reading the Check field
  44         size_t check_pos;
  45
  46         /// Check of the uncompressed data
  47         lzma_check_state check;
  48 };
  49
  50
  51 static inline bool
  52 update_size(lzma_vli *size, lzma_vli add, lzma_vli limit)
  53 {
  54         if (limit > LZMA_VLI_MAX)
  55                 limit = LZMA_VLI_MAX;
  56
  57         if (limit < *size || limit - *size < add)
  58                 return true;
  59
  60         *size += add;
  61
  62         return false;
  63 }
  64
  65
  66 static inline bool
  67 is_size_valid(lzma_vli size, lzma_vli reference)
  68 {
  69         return reference == LZMA_VLI_UNKNOWN || reference == size;
  70 }
  71
  72
  73 static lzma_ret
  74 block_decode(lzma_coder *coder, lzma_allocator *allocator,
  75                 const uint8_t *restrict in, size_t *restrict in_pos,
  76                 size_t in_size, uint8_t *restrict out,
  77                 size_t *restrict out_pos, size_t out_size, lzma_action action)
  78 {
  79         switch (coder->sequence) {
  80         case SEQ_CODE: {
  81                 const size_t in_start = *in_pos;
  82                 const size_t out_start = *out_pos;
  83
  84                 const lzma_ret ret = coder->next.code(coder->next.coder,
  85                                 allocator, in, in_pos, in_size,
  86                                 out, out_pos, out_size, action);
  87
  88                 const size_t in_used = *in_pos - in_start;
  89                 const size_t out_used = *out_pos - out_start;
  90
  91                 // NOTE: We compare to compressed_limit here, which prevents
  92                 // the total size of the Block growing past LZMA_VLI_MAX.
  93                 if (update_size(&coder->compressed_size, in_used,
  94                                         coder->compressed_limit)
  95                                 || update_size(&coder->uncompressed_size,
  96                                         out_used,
  97                                         coder->block->uncompressed_size))
  98                         return LZMA_DATA_ERROR;
  99
 100                 lzma_check_update(&coder->check, coder->block->check,
 101                                 out + out_start, out_used);
 102
 103                 if (ret != LZMA_STREAM_END)
 104                         return ret;
 105
 106                 // Compressed and Uncompressed Sizes are now at their final
 107                 // values. Verify that they match the values given to us.
 108                 if (!is_size_valid(coder->compressed_size,
 109                                         coder->block->compressed_size)
 110                                 || !is_size_valid(coder->uncompressed_size,
 111                                         coder->block->uncompressed_size))
 112                         return LZMA_DATA_ERROR;
 113
 114                 // Copy the values into coder->block. The caller
 115                 // may use this information to construct Index.
 116                 coder->block->compressed_size = coder->compressed_size;
 117                 coder->block->uncompressed_size = coder->uncompressed_size;
 118
 119                 coder->sequence = SEQ_PADDING;
 120         }
 121
 122         // Fall through
 123
 124         case SEQ_PADDING:
 125                 // Compressed Data is padded to a multiple of four bytes.
 126                 while (coder->compressed_size & 3) {
 127                         if (*in_pos >= in_size)
 128                                 return LZMA_OK;
 129
 130                         // We use compressed_size here just get the Padding
 131                         // right. The actual Compressed Size was stored to
 132                         // coder->block already, and won't be modified by
 133                         // us anymore.
 134                         ++coder->compressed_size;
 135
 136                         if (in[(*in_pos)++] != 0x00)
 137                                 return LZMA_DATA_ERROR;
 138                 }
 139
 140                 if (coder->block->check == LZMA_CHECK_NONE)
 141                         return LZMA_STREAM_END;
 142
 143                 lzma_check_finish(&coder->check, coder->block->check);
 144                 coder->sequence = SEQ_CHECK;
 145
 146         // Fall through
 147
 148         case SEQ_CHECK: {
 149                 const bool chksup = lzma_check_is_supported(
 150                                 coder->block->check);
 151
 152                 while (*in_pos < in_size) {
 153                         // coder->check.buffer[] may be uninitialized when
 154                         // the Check ID is not supported.
 155                         if (chksup && coder->check.buffer.u8[coder->check_pos]
 156                                         != in[*in_pos]) {
 157                                 ++*in_pos;
 158                                 return LZMA_DATA_ERROR;
 159                         }
 160
 161                         ++*in_pos;
 162
 163                         if (++coder->check_pos == lzma_check_size(
 164                                         coder->block->check))
 165                                 return LZMA_STREAM_END;
 166                 }
 167
 168                 return LZMA_OK;
 169         }
 170         }
 171
 172         return LZMA_PROG_ERROR;
 173 }
 174
 175
 176 static void
 177 block_decoder_end(lzma_coder *coder, lzma_allocator *allocator)
 178 {
 179         lzma_next_end(&coder->next, allocator);
 180         lzma_free(coder, allocator);
 181         return;
 182 }
 183
 184
 185 extern lzma_ret
 186 lzma_block_decoder_init(lzma_next_coder *next, lzma_allocator *allocator,
 187                 lzma_block *block)
 188 {
 189         lzma_next_coder_init(lzma_block_decoder_init, next, allocator);
 190
 191         // Validate the options. lzma_block_unpadded_size() does that for us
 192         // except for Uncompressed Size and filters. Filters are validated
 193         // by the raw decoder.
 194         if (lzma_block_unpadded_size(block) == 0
 195                         || !lzma_vli_is_valid(block->uncompressed_size))
 196                 return LZMA_PROG_ERROR;
 197
 198         // Allocate and initialize *next->coder if needed.
 199         if (next->coder == NULL) {
 200                 next->coder = lzma_alloc(sizeof(lzma_coder), allocator);
 201                 if (next->coder == NULL)
 202                         return LZMA_MEM_ERROR;
 203
 204                 next->code = &block_decode;
 205                 next->end = &block_decoder_end;
 206                 next->coder->next = LZMA_NEXT_CODER_INIT;
 207         }
 208
 209         // Basic initializations
 210         next->coder->sequence = SEQ_CODE;
 211         next->coder->block = block;
 212         next->coder->compressed_size = 0;
 213         next->coder->uncompressed_size = 0;
 214
 215         // If Compressed Size is not known, we calculate the maximum allowed
 216         // value so that encoded size of the Block (including Block Padding)
 217         // is still a valid VLI and a multiple of four.
 218         next->coder->compressed_limit
 219                         = block->compressed_size == LZMA_VLI_UNKNOWN
 220                                 ? (LZMA_VLI_MAX & ~LZMA_VLI_C(3))
 221                                         - block->header_size
 222                                         - lzma_check_size(block->check)
 223                                 : block->compressed_size;
 224
 225         // Initialize the check. It's caller's problem if the Check ID is not
 226         // supported, and the Block decoder cannot verify the Check field.
 227         // Caller can test lzma_check_is_supported(block->check).
 228         next->coder->check_pos = 0;
 229         lzma_check_init(&next->coder->check, block->check);
 230
 231         // Initialize the filter chain.
 232         return lzma_raw_decoder_init(&next->coder->next, allocator,
 233                         block->filters);
 234 }
 235
 236
 237 extern LZMA_API(lzma_ret)
 238 lzma_block_decoder(lzma_stream *strm, lzma_block *block)
 239 {
 240         lzma_next_strm_init(lzma_block_decoder_init, strm, block);
 241
 242         strm->internal->supported_actions[LZMA_RUN] = true;
 243         strm->internal->supported_actions[LZMA_FINISH] = true;
 244
 245         return LZMA_OK;
 246 }