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 typedef struct {
  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 } lzma_block_coder;
  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(void *coder_ptr, 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         lzma_block_coder *coder = coder_ptr;
  83
  84         switch (coder->sequence) {
  85         case SEQ_CODE: {
  86                 const size_t in_start = *in_pos;
  87                 const size_t out_start = *out_pos;
  88
  89                 const lzma_ret ret = coder->next.code(coder->next.coder,
  90                                 allocator, in, in_pos, in_size,
  91                                 out, out_pos, out_size, action);
  92
  93                 const size_t in_used = *in_pos - in_start;
  94                 const size_t out_used = *out_pos - out_start;
  95
  96                 // NOTE: We compare to compressed_limit here, which prevents
  97                 // the total size of the Block growing past LZMA_VLI_MAX.
  98                 if (update_size(&coder->compressed_size, in_used,
  99                                         coder->compressed_limit)
 100                                 || update_size(&coder->uncompressed_size,
 101                                         out_used,
 102                                         coder->block->uncompressed_size))
 103                         return LZMA_DATA_ERROR;
 104
 105                 if (!coder->ignore_check)
 106                         lzma_check_update(&coder->check, coder->block->check,
 107                                         out + out_start, out_used);
 108
 109                 if (ret != LZMA_STREAM_END)
 110                         return ret;
 111
 112                 // Compressed and Uncompressed Sizes are now at their final
 113                 // values. Verify that they match the values given to us.
 114                 if (!is_size_valid(coder->compressed_size,
 115                                         coder->block->compressed_size)
 116                                 || !is_size_valid(coder->uncompressed_size,
 117                                         coder->block->uncompressed_size))
 118                         return LZMA_DATA_ERROR;
 119
 120                 // Copy the values into coder->block. The caller
 121                 // may use this information to construct Index.
 122                 coder->block->compressed_size = coder->compressed_size;
 123                 coder->block->uncompressed_size = coder->uncompressed_size;
 124
 125                 coder->sequence = SEQ_PADDING;
 126         }
 127
 128         // Fall through
 129
 130         case SEQ_PADDING:
 131                 // Compressed Data is padded to a multiple of four bytes.
 132                 while (coder->compressed_size & 3) {
 133                         if (*in_pos >= in_size)
 134                                 return LZMA_OK;
 135
 136                         // We use compressed_size here just get the Padding
 137                         // right. The actual Compressed Size was stored to
 138                         // coder->block already, and won't be modified by
 139                         // us anymore.
 140                         ++coder->compressed_size;
 141
 142                         if (in[(*in_pos)++] != 0x00)
 143                                 return LZMA_DATA_ERROR;
 144                 }
 145
 146                 if (coder->block->check == LZMA_CHECK_NONE)
 147                         return LZMA_STREAM_END;
 148
 149                 if (!coder->ignore_check)
 150                         lzma_check_finish(&coder->check, coder->block->check);
 151
 152                 coder->sequence = SEQ_CHECK;
 153
 154         // Fall through
 155
 156         case SEQ_CHECK: {
 157                 const size_t check_size = lzma_check_size(coder->block->check);
 158                 lzma_bufcpy(in, in_pos, in_size, coder->block->raw_check,
 159                                 &coder->check_pos, check_size);
 160                 if (coder->check_pos < check_size)
 161                         return LZMA_OK;
 162
 163                 // Validate the Check only if we support it.
 164                 // coder->check.buffer may be uninitialized
 165                 // when the Check ID is not supported.
 166                 if (!coder->ignore_check
 167                                 && lzma_check_is_supported(coder->block->check)
 168                                 && memcmp(coder->block->raw_check,
 169                                         coder->check.buffer.u8,
 170                                         check_size) != 0)
 171                         return LZMA_DATA_ERROR;
 172
 173                 return LZMA_STREAM_END;
 174         }
 175         }
 176
 177         return LZMA_PROG_ERROR;
 178 }
 179
 180
 181 static void
 182 block_decoder_end(void *coder_ptr, const lzma_allocator *allocator)
 183 {
 184         lzma_block_coder *coder = coder_ptr;
 185         lzma_next_end(&coder->next, allocator);
 186         lzma_free(coder, allocator);
 187         return;
 188 }
 189
 190
 191 extern lzma_ret
 192 lzma_block_decoder_init(lzma_next_coder *next, const lzma_allocator *allocator,
 193                 lzma_block *block)
 194 {
 195         lzma_next_coder_init(&lzma_block_decoder_init, next, allocator);
 196
 197         // Validate the options. lzma_block_unpadded_size() does that for us
 198         // except for Uncompressed Size and filters. Filters are validated
 199         // by the raw decoder.
 200         if (lzma_block_unpadded_size(block) == 0
 201                         || !lzma_vli_is_valid(block->uncompressed_size))
 202                 return LZMA_PROG_ERROR;
 203
 204         // Allocate *next->coder if needed.
 205         lzma_block_coder *coder = next->coder;
 206         if (coder == NULL) {
 207                 coder = lzma_alloc(sizeof(lzma_block_coder), allocator);
 208                 if (coder == NULL)
 209                         return LZMA_MEM_ERROR;
 210
 211                 next->coder = coder;
 212                 next->code = &block_decode;
 213                 next->end = &block_decoder_end;
 214                 coder->next = LZMA_NEXT_CODER_INIT;
 215         }
 216
 217         // Basic initializations
 218         coder->sequence = SEQ_CODE;
 219         coder->block = block;
 220         coder->compressed_size = 0;
 221         coder->uncompressed_size = 0;
 222
 223         // If Compressed Size is not known, we calculate the maximum allowed
 224         // value so that encoded size of the Block (including Block Padding)
 225         // is still a valid VLI and a multiple of four.
 226         coder->compressed_limit
 227                         = block->compressed_size == LZMA_VLI_UNKNOWN
 228                                 ? (LZMA_VLI_MAX & ~LZMA_VLI_C(3))
 229                                         - block->header_size
 230                                         - lzma_check_size(block->check)
 231                                 : block->compressed_size;
 232
 233         // Initialize the check. It's caller's problem if the Check ID is not
 234         // supported, and the Block decoder cannot verify the Check field.
 235         // Caller can test lzma_check_is_supported(block->check).
 236         coder->check_pos = 0;
 237         lzma_check_init(&coder->check, block->check);
 238
 239         coder->ignore_check = block->version >= 1
 240                         ? block->ignore_check : false;
 241
 242         // Initialize the filter chain.
 243         return lzma_raw_decoder_init(&coder->next, allocator,
 244                         block->filters);
 245 }
 246
 247
 248 extern LZMA_API(lzma_ret)
 249 lzma_block_decoder(lzma_stream *strm, lzma_block *block)
 250 {
 251         lzma_next_strm_init(lzma_block_decoder_init, strm, block);
 252
 253         strm->internal->supported_actions[LZMA_RUN] = true;
 254         strm->internal->supported_actions[LZMA_FINISH] = true;
 255
 256         return LZMA_OK;
 257 }