external/public-domain/xz/dist/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         /// True if the integrity check won't be calculated and verified.
  50         bool ignore_check;
  51 };
  52
  53
  54 static inline bool
  55 update_size(lzma_vli *size, lzma_vli add, lzma_vli limit)
  56 {
  57         if (limit > LZMA_VLI_MAX)
  58                 limit = LZMA_VLI_MAX;
  59
  60         if (limit < *size || limit - *size < add)
  61                 return true;
  62
  63         *size += add;
  64
  65         return false;
  66 }
  67
  68
  69 static inline bool
  70 is_size_valid(lzma_vli size, lzma_vli reference)
  71 {
  72         return reference == LZMA_VLI_UNKNOWN || reference == size;
  73 }
  74
  75
  76 static lzma_ret
  77 block_decode(lzma_coder *coder, const lzma_allocator *allocator,
  78                 const uint8_t *restrict in, size_t *restrict in_pos,
  79                 size_t in_size, uint8_t *restrict out,
  80                 size_t *restrict out_pos, size_t out_size, lzma_action action)
  81 {
  82         switch (coder->sequence) {
  83         case SEQ_CODE: {
  84                 const size_t in_start = *in_pos;
  85                 const size_t out_start = *out_pos;
  86
  87                 const lzma_ret ret = coder->next.code(coder->next.coder,
  88                                 allocator, in, in_pos, in_size,
  89                                 out, out_pos, out_size, action);
  90
  91                 const size_t in_used = *in_pos - in_start;
  92                 const size_t out_used = *out_pos - out_start;
  93
  94                 // NOTE: We compare to compressed_limit here, which prevents
  95                 // the total size of the Block growing past LZMA_VLI_MAX.
  96                 if (update_size(&coder->compressed_size, in_used,
  97                                         coder->compressed_limit)
  98                                 || update_size(&coder->uncompressed_size,
  99                                         out_used,
 100                                         coder->block->uncompressed_size))
 101                         return LZMA_DATA_ERROR;
 102
 103                 if (!coder->ignore_check)
 104                         lzma_check_update(&coder->check, coder->block->check,
 105                                         out + out_start, out_used);
 106
 107                 if (ret != LZMA_STREAM_END)
 108                         return ret;
 109
 110                 // Compressed and Uncompressed Sizes are now at their final
 111                 // values. Verify that they match the values given to us.
 112                 if (!is_size_valid(coder->compressed_size,
 113                                         coder->block->compressed_size)
 114                                 || !is_size_valid(coder->uncompressed_size,
 115                                         coder->block->uncompressed_size))
 116                         return LZMA_DATA_ERROR;
 117
 118                 // Copy the values into coder->block. The caller
 119                 // may use this information to construct Index.
 120                 coder->block->compressed_size = coder->compressed_size;
 121                 coder->block->uncompressed_size = coder->uncompressed_size;
 122
 123                 coder->sequence = SEQ_PADDING;
 124         }
 125
 126         // Fall through
 127
 128         case SEQ_PADDING:
 129                 // Compressed Data is padded to a multiple of four bytes.
 130                 while (coder->compressed_size & 3) {
 131                         if (*in_pos >= in_size)
 132                                 return LZMA_OK;
 133
 134                         // We use compressed_size here just get the Padding
 135                         // right. The actual Compressed Size was stored to
 136                         // coder->block already, and won't be modified by
 137                         // us anymore.
 138                         ++coder->compressed_size;
 139
 140                         if (in[(*in_pos)++] != 0x00)
 141                                 return LZMA_DATA_ERROR;
 142                 }
 143
 144                 if (coder->block->check == LZMA_CHECK_NONE)
 145                         return LZMA_STREAM_END;
 146
 147                 if (!coder->ignore_check)
 148                         lzma_check_finish(&coder->check, coder->block->check);
 149
 150                 coder->sequence = SEQ_CHECK;
 151
 152         // Fall through
 153
 154         case SEQ_CHECK: {
 155                 const size_t check_size = lzma_check_size(coder->block->check);
 156                 lzma_bufcpy(in, in_pos, in_size, coder->block->raw_check,
 157                                 &coder->check_pos, check_size);
 158                 if (coder->check_pos < check_size)
 159                         return LZMA_OK;
 160
 161                 // Validate the Check only if we support it.
 162                 // coder->check.buffer may be uninitialized
 163                 // when the Check ID is not supported.
 164                 if (!coder->ignore_check
 165                                 && lzma_check_is_supported(coder->block->check)
 166                                 && memcmp(coder->block->raw_check,
 167                                         coder->check.buffer.u8,
 168                                         check_size) != 0)
 169                         return LZMA_DATA_ERROR;
 170
 171                 return LZMA_STREAM_END;
 172         }
 173         }
 174
 175         return LZMA_PROG_ERROR;
 176 }
 177
 178
 179 static void
 180 block_decoder_end(lzma_coder *coder, const lzma_allocator *allocator)
 181 {
 182         lzma_next_end(&coder->next, allocator);
 183         lzma_free(coder, allocator);
 184         return;
 185 }
 186
 187
 188 extern lzma_ret
 189 lzma_block_decoder_init(lzma_next_coder *next, const lzma_allocator *allocator,
 190                 lzma_block *block)
 191 {
 192         lzma_next_coder_init(&lzma_block_decoder_init, next, allocator);
 193
 194         // Validate the options. lzma_block_unpadded_size() does that for us
 195         // except for Uncompressed Size and filters. Filters are validated
 196         // by the raw decoder.
 197         if (lzma_block_unpadded_size(block) == 0
 198                         || !lzma_vli_is_valid(block->uncompressed_size))
 199                 return LZMA_PROG_ERROR;
 200
 201         // Allocate and initialize *next->coder if needed.
 202         if (next->coder == NULL) {
 203                 next->coder = lzma_alloc(sizeof(lzma_coder), allocator);
 204                 if (next->coder == NULL)
 205                         return LZMA_MEM_ERROR;
 206
 207                 next->code = &block_decode;
 208                 next->end = &block_decoder_end;
 209                 next->coder->next = LZMA_NEXT_CODER_INIT;
 210         }
 211
 212         // Basic initializations
 213         next->coder->sequence = SEQ_CODE;
 214         next->coder->block = block;
 215         next->coder->compressed_size = 0;
 216         next->coder->uncompressed_size = 0;
 217
 218         // If Compressed Size is not known, we calculate the maximum allowed
 219         // value so that encoded size of the Block (including Block Padding)
 220         // is still a valid VLI and a multiple of four.
 221         next->coder->compressed_limit
 222                         = block->compressed_size == LZMA_VLI_UNKNOWN
 223                                 ? (LZMA_VLI_MAX & ~LZMA_VLI_C(3))
 224                                         - block->header_size
 225                                         - lzma_check_size(block->check)
 226                                 : block->compressed_size;
 227
 228         // Initialize the check. It's caller's problem if the Check ID is not
 229         // supported, and the Block decoder cannot verify the Check field.
 230         // Caller can test lzma_check_is_supported(block->check).
 231         next->coder->check_pos = 0;
 232         lzma_check_init(&next->coder->check, block->check);
 233
 234         next->coder->ignore_check = block->version >= 1
 235                         ? block->ignore_check : false;
 236
 237         // Initialize the filter chain.
 238         return lzma_raw_decoder_init(&next->coder->next, allocator,
 239                         block->filters);
 240 }
 241
 242
 243 extern LZMA_API(lzma_ret)
 244 lzma_block_decoder(lzma_stream *strm, lzma_block *block)
 245 {
 246         lzma_next_strm_init(lzma_block_decoder_init, strm, block);
 247
 248         strm->internal->supported_actions[LZMA_RUN] = true;
 249         strm->internal->supported_actions[LZMA_FINISH] = true;
 250
 251         return LZMA_OK;
 252 }