src/liblzma/common/alone_decoder.c

   1 ///////////////////////////////////////////////////////////////////////////////
   2 //
   3 /// \file       alone_decoder.c
   4 /// \brief      Decoder for LZMA_Alone files
   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 "alone_decoder.h"
  14 #include "lzma_decoder.h"
  15 #include "lz_decoder.h"
  16
  17
  18 typedef struct {
  19         lzma_next_coder next;
  20
  21         enum {
  22                 SEQ_PROPERTIES,
  23                 SEQ_DICTIONARY_SIZE,
  24                 SEQ_UNCOMPRESSED_SIZE,
  25                 SEQ_CODER_INIT,
  26                 SEQ_CODE,
  27         } sequence;
  28
  29         /// If true, reject files that are unlikely to be .lzma files.
  30         /// If false, more non-.lzma files get accepted and will give
  31         /// LZMA_DATA_ERROR either immediately or after a few output bytes.
  32         bool picky;
  33
  34         /// Position in the header fields
  35         size_t pos;
  36
  37         /// Uncompressed size decoded from the header
  38         lzma_vli uncompressed_size;
  39
  40         /// Memory usage limit
  41         uint64_t memlimit;
  42
  43         /// Amount of memory actually needed (only an estimate)
  44         uint64_t memusage;
  45
  46         /// Options decoded from the header needed to initialize
  47         /// the LZMA decoder
  48         lzma_options_lzma options;
  49 } lzma_alone_coder;
  50
  51
  52 static lzma_ret
  53 alone_decode(void *coder_ptr, const lzma_allocator *allocator,
  54                 const uint8_t *restrict in, size_t *restrict in_pos,
  55                 size_t in_size, uint8_t *restrict out,
  56                 size_t *restrict out_pos, size_t out_size,
  57                 lzma_action action)
  58 {
  59         lzma_alone_coder *coder = coder_ptr;
  60
  61         while (*out_pos < out_size
  62                         && (coder->sequence == SEQ_CODE || *in_pos < in_size))
  63         switch (coder->sequence) {
  64         case SEQ_PROPERTIES:
  65                 if (lzma_lzma_lclppb_decode(&coder->options, in[*in_pos]))
  66                         return LZMA_FORMAT_ERROR;
  67
  68                 coder->sequence = SEQ_DICTIONARY_SIZE;
  69                 ++*in_pos;
  70                 break;
  71
  72         case SEQ_DICTIONARY_SIZE:
  73                 coder->options.dict_size
  74                                 |= (size_t)(in[*in_pos]) << (coder->pos * 8);
  75
  76                 if (++coder->pos == 4) {
  77                         if (coder->picky && coder->options.dict_size
  78                                         != UINT32_MAX) {
  79                                 // A hack to ditch tons of false positives:
  80                                 // We allow only dictionary sizes that are
  81                                 // 2^n or 2^n + 2^(n-1). LZMA_Alone created
  82                                 // only files with 2^n, but accepts any
  83                                 // dictionary size.
  84                                 uint32_t d = coder->options.dict_size - 1;
  85                                 d |= d >> 2;
  86                                 d |= d >> 3;
  87                                 d |= d >> 4;
  88                                 d |= d >> 8;
  89                                 d |= d >> 16;
  90                                 ++d;
  91
  92                                 if (d != coder->options.dict_size)
  93                                         return LZMA_FORMAT_ERROR;
  94                         }
  95
  96                         coder->pos = 0;
  97                         coder->sequence = SEQ_UNCOMPRESSED_SIZE;
  98                 }
  99
 100                 ++*in_pos;
 101                 break;
 102
 103         case SEQ_UNCOMPRESSED_SIZE:
 104                 coder->uncompressed_size
 105                                 |= (lzma_vli)(in[*in_pos]) << (coder->pos * 8);
 106                 ++*in_pos;
 107                 if (++coder->pos < 8)
 108                         break;
 109
 110                 // Another hack to ditch false positives: Assume that
 111                 // if the uncompressed size is known, it must be less
 112                 // than 256 GiB.
 113                 //
 114                 // FIXME? Without picky we allow > LZMA_VLI_MAX which doesn't
 115                 // really matter in this specific situation (> LZMA_VLI_MAX is
 116                 // safe in the LZMA decoder) but it's somewhat weird still.
 117                 if (coder->picky
 118                                 && coder->uncompressed_size != LZMA_VLI_UNKNOWN
 119                                 && coder->uncompressed_size
 120                                         >= (LZMA_VLI_C(1) << 38))
 121                         return LZMA_FORMAT_ERROR;
 122
 123                 // Use LZMA_FILTER_LZMA1EXT features to specify the
 124                 // uncompressed size and that the end marker is allowed
 125                 // even when the uncompressed size is known. Both .lzma
 126                 // header and LZMA1EXT use UINT64_MAX indicate that size
 127                 // is unknown.
 128                 coder->options.ext_flags = LZMA_LZMA1EXT_ALLOW_EOPM;
 129                 lzma_set_ext_size(coder->options, coder->uncompressed_size);
 130
 131                 // Calculate the memory usage so that it is ready
 132                 // for SEQ_CODER_INIT.
 133                 coder->memusage = lzma_lzma_decoder_memusage(&coder->options)
 134                                 + LZMA_MEMUSAGE_BASE;
 135
 136                 coder->pos = 0;
 137                 coder->sequence = SEQ_CODER_INIT;
 138
 139         // Fall through
 140
 141         case SEQ_CODER_INIT: {
 142                 if (coder->memusage > coder->memlimit)
 143                         return LZMA_MEMLIMIT_ERROR;
 144
 145                 lzma_filter_info filters[2] = {
 146                         {
 147                                 .id = LZMA_FILTER_LZMA1EXT,
 148                                 .init = &lzma_lzma_decoder_init,
 149                                 .options = &coder->options,
 150                         }, {
 151                                 .init = NULL,
 152                         }
 153                 };
 154
 155                 return_if_error(lzma_next_filter_init(&coder->next,
 156                                 allocator, filters));
 157
 158                 coder->sequence = SEQ_CODE;
 159                 break;
 160         }
 161
 162         case SEQ_CODE: {
 163                 return coder->next.code(coder->next.coder,
 164                                 allocator, in, in_pos, in_size,
 165                                 out, out_pos, out_size, action);
 166         }
 167
 168         default:
 169                 return LZMA_PROG_ERROR;
 170         }
 171
 172         return LZMA_OK;
 173 }
 174
 175
 176 static void
 177 alone_decoder_end(void *coder_ptr, const lzma_allocator *allocator)
 178 {
 179         lzma_alone_coder *coder = coder_ptr;
 180         lzma_next_end(&coder->next, allocator);
 181         lzma_free(coder, allocator);
 182         return;
 183 }
 184
 185
 186 static lzma_ret
 187 alone_decoder_memconfig(void *coder_ptr, uint64_t *memusage,
 188                 uint64_t *old_memlimit, uint64_t new_memlimit)
 189 {
 190         lzma_alone_coder *coder = coder_ptr;
 191
 192         *memusage = coder->memusage;
 193         *old_memlimit = coder->memlimit;
 194
 195         if (new_memlimit != 0) {
 196                 if (new_memlimit < coder->memusage)
 197                         return LZMA_MEMLIMIT_ERROR;
 198
 199                 coder->memlimit = new_memlimit;
 200         }
 201
 202         return LZMA_OK;
 203 }
 204
 205
 206 extern lzma_ret
 207 lzma_alone_decoder_init(lzma_next_coder *next, const lzma_allocator *allocator,
 208                 uint64_t memlimit, bool picky)
 209 {
 210         lzma_next_coder_init(&lzma_alone_decoder_init, next, allocator);
 211
 212         lzma_alone_coder *coder = next->coder;
 213
 214         if (coder == NULL) {
 215                 coder = lzma_alloc(sizeof(lzma_alone_coder), allocator);
 216                 if (coder == NULL)
 217                         return LZMA_MEM_ERROR;
 218
 219                 next->coder = coder;
 220                 next->code = &alone_decode;
 221                 next->end = &alone_decoder_end;
 222                 next->memconfig = &alone_decoder_memconfig;
 223                 coder->next = LZMA_NEXT_CODER_INIT;
 224         }
 225
 226         coder->sequence = SEQ_PROPERTIES;
 227         coder->picky = picky;
 228         coder->pos = 0;
 229         coder->options.dict_size = 0;
 230         coder->options.preset_dict = NULL;
 231         coder->options.preset_dict_size = 0;
 232         coder->uncompressed_size = 0;
 233         coder->memlimit = my_max(1, memlimit);
 234         coder->memusage = LZMA_MEMUSAGE_BASE;
 235
 236         return LZMA_OK;
 237 }
 238
 239
 240 extern LZMA_API(lzma_ret)
 241 lzma_alone_decoder(lzma_stream *strm, uint64_t memlimit)
 242 {
 243         lzma_next_strm_init(lzma_alone_decoder_init, strm, memlimit, false);
 244
 245         strm->internal->supported_actions[LZMA_RUN] = true;
 246         strm->internal->supported_actions[LZMA_FINISH] = true;
 247
 248         return LZMA_OK;
 249 }