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,
  54                 const lzma_allocator *allocator lzma_attribute((__unused__)),
  55                 const uint8_t *restrict in, size_t *restrict in_pos,
  56                 size_t in_size, uint8_t *restrict out,
  57                 size_t *restrict out_pos, size_t out_size,
  58                 lzma_action action)
  59 {
  60         lzma_alone_coder *coder = coder_ptr;
  61
  62         while (*out_pos < out_size
  63                         && (coder->sequence == SEQ_CODE || *in_pos < in_size))
  64         switch (coder->sequence) {
  65         case SEQ_PROPERTIES:
  66                 if (lzma_lzma_lclppb_decode(&coder->options, in[*in_pos]))
  67                         return LZMA_FORMAT_ERROR;
  68
  69                 coder->sequence = SEQ_DICTIONARY_SIZE;
  70                 ++*in_pos;
  71                 break;
  72
  73         case SEQ_DICTIONARY_SIZE:
  74                 coder->options.dict_size
  75                                 |= (size_t)(in[*in_pos]) << (coder->pos * 8);
  76
  77                 if (++coder->pos == 4) {
  78                         if (coder->picky && coder->options.dict_size
  79                                         != UINT32_MAX) {
  80                                 // A hack to ditch tons of false positives:
  81                                 // We allow only dictionary sizes that are
  82                                 // 2^n or 2^n + 2^(n-1). LZMA_Alone created
  83                                 // only files with 2^n, but accepts any
  84                                 // dictionary size.
  85                                 uint32_t d = coder->options.dict_size - 1;
  86                                 d |= d >> 2;
  87                                 d |= d >> 3;
  88                                 d |= d >> 4;
  89                                 d |= d >> 8;
  90                                 d |= d >> 16;
  91                                 ++d;
  92
  93                                 if (d != coder->options.dict_size)
  94                                         return LZMA_FORMAT_ERROR;
  95                         }
  96
  97                         coder->pos = 0;
  98                         coder->sequence = SEQ_UNCOMPRESSED_SIZE;
  99                 }
 100
 101                 ++*in_pos;
 102                 break;
 103
 104         case SEQ_UNCOMPRESSED_SIZE:
 105                 coder->uncompressed_size
 106                                 |= (lzma_vli)(in[*in_pos]) << (coder->pos * 8);
 107                 ++*in_pos;
 108                 if (++coder->pos < 8)
 109                         break;
 110
 111                 // Another hack to ditch false positives: Assume that
 112                 // if the uncompressed size is known, it must be less
 113                 // than 256 GiB.
 114                 if (coder->picky
 115                                 && coder->uncompressed_size != LZMA_VLI_UNKNOWN
 116                                 && coder->uncompressed_size
 117                                         >= (LZMA_VLI_C(1) << 38))
 118                         return LZMA_FORMAT_ERROR;
 119
 120                 // Calculate the memory usage so that it is ready
 121                 // for SEQ_CODER_INIT.
 122                 coder->memusage = lzma_lzma_decoder_memusage(&coder->options)
 123                                 + LZMA_MEMUSAGE_BASE;
 124
 125                 coder->pos = 0;
 126                 coder->sequence = SEQ_CODER_INIT;
 127
 128         // Fall through
 129
 130         case SEQ_CODER_INIT: {
 131                 if (coder->memusage > coder->memlimit)
 132                         return LZMA_MEMLIMIT_ERROR;
 133
 134                 lzma_filter_info filters[2] = {
 135                         {
 136                                 .init = &lzma_lzma_decoder_init,
 137                                 .options = &coder->options,
 138                         }, {
 139                                 .init = NULL,
 140                         }
 141                 };
 142
 143                 const lzma_ret ret = lzma_next_filter_init(&coder->next,
 144                                 allocator, filters);
 145                 if (ret != LZMA_OK)
 146                         return ret;
 147
 148                 // Use a hack to set the uncompressed size.
 149                 lzma_lz_decoder_uncompressed(coder->next.coder,
 150                                 coder->uncompressed_size);
 151
 152                 coder->sequence = SEQ_CODE;
 153                 break;
 154         }
 155
 156         case SEQ_CODE: {
 157                 return coder->next.code(coder->next.coder,
 158                                 allocator, in, in_pos, in_size,
 159                                 out, out_pos, out_size, action);
 160         }
 161
 162         default:
 163                 return LZMA_PROG_ERROR;
 164         }
 165
 166         return LZMA_OK;
 167 }
 168
 169
 170 static void
 171 alone_decoder_end(void *coder_ptr, const lzma_allocator *allocator)
 172 {
 173         lzma_alone_coder *coder = coder_ptr;
 174         lzma_next_end(&coder->next, allocator);
 175         lzma_free(coder, allocator);
 176         return;
 177 }
 178
 179
 180 static lzma_ret
 181 alone_decoder_memconfig(void *coder_ptr, uint64_t *memusage,
 182                 uint64_t *old_memlimit, uint64_t new_memlimit)
 183 {
 184         lzma_alone_coder *coder = coder_ptr;
 185
 186         *memusage = coder->memusage;
 187         *old_memlimit = coder->memlimit;
 188
 189         if (new_memlimit != 0) {
 190                 if (new_memlimit < coder->memusage)
 191                         return LZMA_MEMLIMIT_ERROR;
 192
 193                 coder->memlimit = new_memlimit;
 194         }
 195
 196         return LZMA_OK;
 197 }
 198
 199
 200 extern lzma_ret
 201 lzma_alone_decoder_init(lzma_next_coder *next, const lzma_allocator *allocator,
 202                 uint64_t memlimit, bool picky)
 203 {
 204         lzma_next_coder_init(&lzma_alone_decoder_init, next, allocator);
 205
 206         lzma_alone_coder *coder = next->coder;
 207
 208         if (coder == NULL) {
 209                 coder = lzma_alloc(sizeof(lzma_alone_coder), allocator);
 210                 if (coder == NULL)
 211                         return LZMA_MEM_ERROR;
 212
 213                 next->coder = coder;
 214                 next->code = &alone_decode;
 215                 next->end = &alone_decoder_end;
 216                 next->memconfig = &alone_decoder_memconfig;
 217                 coder->next = LZMA_NEXT_CODER_INIT;
 218         }
 219
 220         coder->sequence = SEQ_PROPERTIES;
 221         coder->picky = picky;
 222         coder->pos = 0;
 223         coder->options.dict_size = 0;
 224         coder->options.preset_dict = NULL;
 225         coder->options.preset_dict_size = 0;
 226         coder->uncompressed_size = 0;
 227         coder->memlimit = my_max(1, memlimit);
 228         coder->memusage = LZMA_MEMUSAGE_BASE;
 229
 230         return LZMA_OK;
 231 }
 232
 233
 234 extern LZMA_API(lzma_ret)
 235 lzma_alone_decoder(lzma_stream *strm, uint64_t memlimit)
 236 {
 237         lzma_next_strm_init(lzma_alone_decoder_init, strm, memlimit, false);
 238
 239         strm->internal->supported_actions[LZMA_RUN] = true;
 240         strm->internal->supported_actions[LZMA_FINISH] = true;
 241
 242         return LZMA_OK;
 243 }