src/liblzma/common/block_decoder.c

   1 ///////////////////////////////////////////////////////////////////////////////
   2 //
   3 /// \file       block_decoder.c
   4 /// \brief      Decodes .lzma Blocks
   5 //
   6 //  Copyright (C) 2007 Lasse Collin
   7 //
   8 //  This library is free software; you can redistribute it and/or
   9 //  modify it under the terms of the GNU Lesser General Public
  10 //  License as published by the Free Software Foundation; either
  11 //  version 2.1 of the License, or (at your option) any later version.
  12 //
  13 //  This library is distributed in the hope that it will be useful,
  14 //  but WITHOUT ANY WARRANTY; without even the implied warranty of
  15 //  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  16 //  Lesser General Public License for more details.
  17 //
  18 ///////////////////////////////////////////////////////////////////////////////
  19
  20 #include "block_decoder.h"
  21 #include "filter_decoder.h"
  22 #include "check.h"
  23
  24
  25 struct lzma_coder_s {
  26         enum {
  27                 SEQ_CODE,
  28                 SEQ_PADDING,
  29                 SEQ_CHECK,
  30         } sequence;
  31
  32         /// The filters in the chain; initialized with lzma_raw_decoder_init().
  33         lzma_next_coder next;
  34
  35         /// Decoding options; we also write Compressed Size and Uncompressed
  36         /// Size back to this structure when the decoding has been finished.
  37         lzma_block *options;
  38
  39         /// Compressed Size calculated while decoding
  40         lzma_vli compressed_size;
  41
  42         /// Uncompressed Size calculated while decoding
  43         lzma_vli uncompressed_size;
  44
  45         /// Maximum allowed Compressed Size; this takes into account the
  46         /// size of the Block Header and Check fields when Compressed Size
  47         /// is unknown.
  48         lzma_vli compressed_limit;
  49
  50         /// Position when reading the Check field
  51         size_t check_pos;
  52
  53         /// Check of the uncompressed data
  54         lzma_check_state check;
  55 };
  56
  57
  58 static inline bool
  59 update_size(lzma_vli *size, lzma_vli add, lzma_vli limit)
  60 {
  61         if (limit > LZMA_VLI_MAX)
  62                 limit = LZMA_VLI_MAX;
  63
  64         if (limit < *size || limit - *size < add)
  65                 return true;
  66
  67         *size += add;
  68
  69         return false;
  70 }
  71
  72
  73 static inline bool
  74 is_size_valid(lzma_vli size, lzma_vli reference)
  75 {
  76         return reference == LZMA_VLI_UNKNOWN || reference == size;
  77 }
  78
  79
  80 static lzma_ret
  81 block_decode(lzma_coder *coder, lzma_allocator *allocator,
  82                 const uint8_t *restrict in, size_t *restrict in_pos,
  83                 size_t in_size, uint8_t *restrict out,
  84                 size_t *restrict out_pos, size_t out_size, lzma_action action)
  85 {
  86         switch (coder->sequence) {
  87         case SEQ_CODE: {
  88                 const size_t in_start = *in_pos;
  89                 const size_t out_start = *out_pos;
  90
  91                 const lzma_ret ret = coder->next.code(coder->next.coder,
  92                                 allocator, in, in_pos, in_size,
  93                                 out, out_pos, out_size, action);
  94
  95                 const size_t in_used = *in_pos - in_start;
  96                 const size_t out_used = *out_pos - out_start;
  97
  98                 // NOTE: We compare to compressed_limit here, which prevents
  99                 // the total size of the Block growing past LZMA_VLI_MAX.
 100                 if (update_size(&coder->compressed_size, in_used,
 101                                         coder->compressed_limit)
 102                                 || update_size(&coder->uncompressed_size,
 103                                         out_used,
 104                                         coder->options->uncompressed_size))
 105                         return LZMA_DATA_ERROR;
 106
 107                 lzma_check_update(&coder->check, coder->options->check,
 108                                 out + out_start, out_used);
 109
 110                 if (ret != LZMA_STREAM_END)
 111                         return ret;
 112
 113                 // Compressed and Uncompressed Sizes are now at their final
 114                 // values. Verify that they match the values given to us.
 115                 if (!is_size_valid(coder->compressed_size,
 116                                         coder->options->compressed_size)
 117                                 || !is_size_valid(coder->uncompressed_size,
 118                                         coder->options->uncompressed_size))
 119                         return LZMA_DATA_ERROR;
 120
 121                 // Copy the values into coder->options. The caller
 122                 // may use this information to construct Index.
 123                 coder->options->compressed_size = coder->compressed_size;
 124                 coder->options->uncompressed_size = coder->uncompressed_size;
 125
 126                 coder->sequence = SEQ_PADDING;
 127         }
 128
 129         // Fall through
 130
 131         case SEQ_PADDING:
 132                 // Compressed Data is padded to a multiple of four bytes.
 133                 while (coder->compressed_size & 3) {
 134                         // We use compressed_size here just get the Padding
 135                         // right. The actual Compressed Size was stored to
 136                         // coder->options already, and won't be modified by
 137                         // us anymore.
 138                         ++coder->compressed_size;
 139
 140                         if (*in_pos >= in_size)
 141                                 return LZMA_OK;
 142
 143                         if (in[(*in_pos)++] != 0x00)
 144                                 return LZMA_DATA_ERROR;
 145                 }
 146
 147                 if (coder->options->check == LZMA_CHECK_NONE)
 148                         return LZMA_STREAM_END;
 149
 150                 lzma_check_finish(&coder->check, coder->options->check);
 151                 coder->sequence = SEQ_CHECK;
 152
 153         // Fall through
 154
 155         case SEQ_CHECK: {
 156                 const bool chksup = lzma_check_is_supported(
 157                                 coder->options->check);
 158
 159                 while (*in_pos < in_size) {
 160                         // coder->check.buffer[] may be uninitialized when
 161                         // the Check ID is not supported.
 162                         if (chksup && coder->check.buffer.u8[coder->check_pos]
 163                                         != in[*in_pos]) {
 164                                 ++*in_pos;
 165                                 return LZMA_DATA_ERROR;
 166                         }
 167
 168                         ++*in_pos;
 169
 170                         if (++coder->check_pos == lzma_check_size(
 171                                         coder->options->check))
 172                                 return LZMA_STREAM_END;
 173                 }
 174
 175                 return LZMA_OK;
 176         }
 177         }
 178
 179         return LZMA_PROG_ERROR;
 180 }
 181
 182
 183 static void
 184 block_decoder_end(lzma_coder *coder, lzma_allocator *allocator)
 185 {
 186         lzma_next_end(&coder->next, allocator);
 187         lzma_free(coder, allocator);
 188         return;
 189 }
 190
 191
 192 extern lzma_ret
 193 lzma_block_decoder_init(lzma_next_coder *next, lzma_allocator *allocator,
 194                 lzma_block *options)
 195 {
 196         lzma_next_coder_init(lzma_block_decoder_init, next, allocator);
 197
 198         // Validate the options. lzma_block_unpadded_size() does that for us
 199         // except for Uncompressed Size and filters. Filters are validated
 200         // by the raw decoder.
 201         if (lzma_block_unpadded_size(options) == 0
 202                         || !lzma_vli_is_valid(options->uncompressed_size))
 203                 return LZMA_PROG_ERROR;
 204
 205         // Allocate and initialize *next->coder if needed.
 206         if (next->coder == NULL) {
 207                 next->coder = lzma_alloc(sizeof(lzma_coder), allocator);
 208                 if (next->coder == NULL)
 209                         return LZMA_MEM_ERROR;
 210
 211                 next->code = &block_decode;
 212                 next->end = &block_decoder_end;
 213                 next->coder->next = LZMA_NEXT_CODER_INIT;
 214         }
 215
 216         // Basic initializations
 217         next->coder->sequence = SEQ_CODE;
 218         next->coder->options = options;
 219         next->coder->compressed_size = 0;
 220         next->coder->uncompressed_size = 0;
 221
 222         // If Compressed Size is not known, we calculate the maximum allowed
 223         // value so that encoded size of the Block (including Block Padding)
 224         // is still a valid VLI and a multiple of four.
 225         next->coder->compressed_limit
 226                         = options->compressed_size == LZMA_VLI_UNKNOWN
 227                                 ? (LZMA_VLI_MAX & ~LZMA_VLI_C(3))
 228                                         - options->header_size
 229                                         - lzma_check_size(options->check)
 230                                 : options->compressed_size;
 231
 232         // Initialize the check. It's caller's problem if the Check ID is not
 233         // supported, and the Block decoder cannot verify the Check field.
 234         // Caller can test lzma_checks[options->check].
 235         next->coder->check_pos = 0;
 236         lzma_check_init(&next->coder->check, options->check);
 237
 238         // Initialize the filter chain.
 239         return lzma_raw_decoder_init(&next->coder->next, allocator,
 240                         options->filters);
 241 }
 242
 243
 244 extern LZMA_API lzma_ret
 245 lzma_block_decoder(lzma_stream *strm, lzma_block *options)
 246 {
 247         lzma_next_strm_init(lzma_block_decoder_init, strm, options);
 248
 249         strm->internal->supported_actions[LZMA_RUN] = true;
 250         strm->internal->supported_actions[LZMA_FINISH] = true;
 251
 252         return LZMA_OK;
 253 }