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 typedef struct { 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 } lzma_block_coder; 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(void *coder_ptr, 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 lzma_block_coder *coder = coder_ptr; 83 84 switch (coder->sequence) { 85 case SEQ_CODE: { 86 const size_t in_start = *in_pos; 87 const size_t out_start = *out_pos; 88 89 const lzma_ret ret = coder->next.code(coder->next.coder, 90 allocator, in, in_pos, in_size, 91 out, out_pos, out_size, action); 92 93 const size_t in_used = *in_pos - in_start; 94 const size_t out_used = *out_pos - out_start; 95 96 // NOTE: We compare to compressed_limit here, which prevents 97 // the total size of the Block growing past LZMA_VLI_MAX. 98 if (update_size(&coder->compressed_size, in_used, 99 coder->compressed_limit) 100 || update_size(&coder->uncompressed_size, 101 out_used, 102 coder->block->uncompressed_size)) 103 return LZMA_DATA_ERROR; 104 105 if (!coder->ignore_check) 106 lzma_check_update(&coder->check, coder->block->check, 107 out + out_start, out_used); 108 109 if (ret != LZMA_STREAM_END) 110 return ret; 111 112 // Compressed and Uncompressed Sizes are now at their final 113 // values. Verify that they match the values given to us. 114 if (!is_size_valid(coder->compressed_size, 115 coder->block->compressed_size) 116 || !is_size_valid(coder->uncompressed_size, 117 coder->block->uncompressed_size)) 118 return LZMA_DATA_ERROR; 119 120 // Copy the values into coder->block. The caller 121 // may use this information to construct Index. 122 coder->block->compressed_size = coder->compressed_size; 123 coder->block->uncompressed_size = coder->uncompressed_size; 124 125 coder->sequence = SEQ_PADDING; 126 } 127 128 // Fall through 129 130 case SEQ_PADDING: 131 // Compressed Data is padded to a multiple of four bytes. 132 while (coder->compressed_size & 3) { 133 if (*in_pos >= in_size) 134 return LZMA_OK; 135 136 // We use compressed_size here just get the Padding 137 // right. The actual Compressed Size was stored to 138 // coder->block already, and won't be modified by 139 // us anymore. 140 ++coder->compressed_size; 141 142 if (in[(*in_pos)++] != 0x00) 143 return LZMA_DATA_ERROR; 144 } 145 146 if (coder->block->check == LZMA_CHECK_NONE) 147 return LZMA_STREAM_END; 148 149 if (!coder->ignore_check) 150 lzma_check_finish(&coder->check, coder->block->check); 151 152 coder->sequence = SEQ_CHECK; 153 154 // Fall through 155 156 case SEQ_CHECK: { 157 const size_t check_size = lzma_check_size(coder->block->check); 158 lzma_bufcpy(in, in_pos, in_size, coder->block->raw_check, 159 &coder->check_pos, check_size); 160 if (coder->check_pos < check_size) 161 return LZMA_OK; 162 163 // Validate the Check only if we support it. 164 // coder->check.buffer may be uninitialized 165 // when the Check ID is not supported. 166 if (!coder->ignore_check 167 && lzma_check_is_supported(coder->block->check) 168 && memcmp(coder->block->raw_check, 169 coder->check.buffer.u8, 170 check_size) != 0) 171 return LZMA_DATA_ERROR; 172 173 return LZMA_STREAM_END; 174 } 175 } 176 177 return LZMA_PROG_ERROR; 178 } 179 180 181 static void 182 block_decoder_end(void *coder_ptr, const lzma_allocator *allocator) 183 { 184 lzma_block_coder *coder = coder_ptr; 185 lzma_next_end(&coder->next, allocator); 186 lzma_free(coder, allocator); 187 return; 188 } 189 190 191 extern lzma_ret 192 lzma_block_decoder_init(lzma_next_coder *next, const lzma_allocator *allocator, 193 lzma_block *block) 194 { 195 lzma_next_coder_init(&lzma_block_decoder_init, next, allocator); 196 197 // Validate the options. lzma_block_unpadded_size() does that for us 198 // except for Uncompressed Size and filters. Filters are validated 199 // by the raw decoder. 200 if (lzma_block_unpadded_size(block) == 0 201 || !lzma_vli_is_valid(block->uncompressed_size)) 202 return LZMA_PROG_ERROR; 203 204 // Allocate *next->coder if needed. 205 lzma_block_coder *coder = next->coder; 206 if (coder == NULL) { 207 coder = lzma_alloc(sizeof(lzma_block_coder), allocator); 208 if (coder == NULL) 209 return LZMA_MEM_ERROR; 210 211 next->coder = coder; 212 next->code = &block_decode; 213 next->end = &block_decoder_end; 214 coder->next = LZMA_NEXT_CODER_INIT; 215 } 216 217 // Basic initializations 218 coder->sequence = SEQ_CODE; 219 coder->block = block; 220 coder->compressed_size = 0; 221 coder->uncompressed_size = 0; 222 223 // If Compressed Size is not known, we calculate the maximum allowed 224 // value so that encoded size of the Block (including Block Padding) 225 // is still a valid VLI and a multiple of four. 226 coder->compressed_limit 227 = block->compressed_size == LZMA_VLI_UNKNOWN 228 ? (LZMA_VLI_MAX & ~LZMA_VLI_C(3)) 229 - block->header_size 230 - lzma_check_size(block->check) 231 : block->compressed_size; 232 233 // Initialize the check. It's caller's problem if the Check ID is not 234 // supported, and the Block decoder cannot verify the Check field. 235 // Caller can test lzma_check_is_supported(block->check). 236 coder->check_pos = 0; 237 lzma_check_init(&coder->check, block->check); 238 239 coder->ignore_check = block->version >= 1 240 ? block->ignore_check : false; 241 242 // Initialize the filter chain. 243 return lzma_raw_decoder_init(&coder->next, allocator, 244 block->filters); 245 } 246 247 248 extern LZMA_API(lzma_ret) 249 lzma_block_decoder(lzma_stream *strm, lzma_block *block) 250 { 251 lzma_next_strm_init(lzma_block_decoder_init, strm, block); 252 253 strm->internal->supported_actions[LZMA_RUN] = true; 254 strm->internal->supported_actions[LZMA_FINISH] = true; 255 256 return LZMA_OK; 257 } 258