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