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 if (coder->picky 114 && coder->uncompressed_size != LZMA_VLI_UNKNOWN 115 && coder->uncompressed_size 116 >= (LZMA_VLI_C(1) << 38)) 117 return LZMA_FORMAT_ERROR; 118 119 // Calculate the memory usage so that it is ready 120 // for SEQ_CODER_INIT. 121 coder->memusage = lzma_lzma_decoder_memusage(&coder->options) 122 + LZMA_MEMUSAGE_BASE; 123 124 coder->pos = 0; 125 coder->sequence = SEQ_CODER_INIT; 126 127 // Fall through 128 129 case SEQ_CODER_INIT: { 130 if (coder->memusage > coder->memlimit) 131 return LZMA_MEMLIMIT_ERROR; 132 133 lzma_filter_info filters[2] = { 134 { 135 .init = &lzma_lzma_decoder_init, 136 .options = &coder->options, 137 }, { 138 .init = NULL, 139 } 140 }; 141 142 const lzma_ret ret = lzma_next_filter_init(&coder->next, 143 allocator, filters); 144 if (ret != LZMA_OK) 145 return ret; 146 147 // Use a hack to set the uncompressed size. 148 lzma_lz_decoder_uncompressed(coder->next.coder, 149 coder->uncompressed_size); 150 151 coder->sequence = SEQ_CODE; 152 break; 153 } 154 155 case SEQ_CODE: { 156 return coder->next.code(coder->next.coder, 157 allocator, in, in_pos, in_size, 158 out, out_pos, out_size, action); 159 } 160 161 default: 162 return LZMA_PROG_ERROR; 163 } 164 165 return LZMA_OK; 166 } 167 168 169 static void 170 alone_decoder_end(void *coder_ptr, const lzma_allocator *allocator) 171 { 172 lzma_alone_coder *coder = coder_ptr; 173 lzma_next_end(&coder->next, allocator); 174 lzma_free(coder, allocator); 175 return; 176 } 177 178 179 static lzma_ret 180 alone_decoder_memconfig(void *coder_ptr, uint64_t *memusage, 181 uint64_t *old_memlimit, uint64_t new_memlimit) 182 { 183 lzma_alone_coder *coder = coder_ptr; 184 185 *memusage = coder->memusage; 186 *old_memlimit = coder->memlimit; 187 188 if (new_memlimit != 0) { 189 if (new_memlimit < coder->memusage) 190 return LZMA_MEMLIMIT_ERROR; 191 192 coder->memlimit = new_memlimit; 193 } 194 195 return LZMA_OK; 196 } 197 198 199 extern lzma_ret 200 lzma_alone_decoder_init(lzma_next_coder *next, const lzma_allocator *allocator, 201 uint64_t memlimit, bool picky) 202 { 203 lzma_next_coder_init(&lzma_alone_decoder_init, next, allocator); 204 205 lzma_alone_coder *coder = next->coder; 206 207 if (coder == NULL) { 208 coder = lzma_alloc(sizeof(lzma_alone_coder), allocator); 209 if (coder == NULL) 210 return LZMA_MEM_ERROR; 211 212 next->coder = coder; 213 next->code = &alone_decode; 214 next->end = &alone_decoder_end; 215 next->memconfig = &alone_decoder_memconfig; 216 coder->next = LZMA_NEXT_CODER_INIT; 217 } 218 219 coder->sequence = SEQ_PROPERTIES; 220 coder->picky = picky; 221 coder->pos = 0; 222 coder->options.dict_size = 0; 223 coder->options.preset_dict = NULL; 224 coder->options.preset_dict_size = 0; 225 coder->uncompressed_size = 0; 226 coder->memlimit = my_max(1, memlimit); 227 coder->memusage = LZMA_MEMUSAGE_BASE; 228 229 return LZMA_OK; 230 } 231 232 233 extern LZMA_API(lzma_ret) 234 lzma_alone_decoder(lzma_stream *strm, uint64_t memlimit) 235 { 236 lzma_next_strm_init(lzma_alone_decoder_init, strm, memlimit, false); 237 238 strm->internal->supported_actions[LZMA_RUN] = true; 239 strm->internal->supported_actions[LZMA_FINISH] = true; 240 241 return LZMA_OK; 242 } 243