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 50 51 static inline bool 52 update_size(lzma_vli *size, lzma_vli add, lzma_vli limit) 53 { 54 if (limit > LZMA_VLI_MAX) 55 limit = LZMA_VLI_MAX; 56 57 if (limit < *size || limit - *size < add) 58 return true; 59 60 *size += add; 61 62 return false; 63 } 64 65 66 static inline bool 67 is_size_valid(lzma_vli size, lzma_vli reference) 68 { 69 return reference == LZMA_VLI_UNKNOWN || reference == size; 70 } 71 72 73 static lzma_ret 74 block_decode(lzma_coder *coder, lzma_allocator *allocator, 75 const uint8_t *restrict in, size_t *restrict in_pos, 76 size_t in_size, uint8_t *restrict out, 77 size_t *restrict out_pos, size_t out_size, lzma_action action) 78 { 79 switch (coder->sequence) { 80 case SEQ_CODE: { 81 const size_t in_start = *in_pos; 82 const size_t out_start = *out_pos; 83 84 const lzma_ret ret = coder->next.code(coder->next.coder, 85 allocator, in, in_pos, in_size, 86 out, out_pos, out_size, action); 87 88 const size_t in_used = *in_pos - in_start; 89 const size_t out_used = *out_pos - out_start; 90 91 // NOTE: We compare to compressed_limit here, which prevents 92 // the total size of the Block growing past LZMA_VLI_MAX. 93 if (update_size(&coder->compressed_size, in_used, 94 coder->compressed_limit) 95 || update_size(&coder->uncompressed_size, 96 out_used, 97 coder->block->uncompressed_size)) 98 return LZMA_DATA_ERROR; 99 100 lzma_check_update(&coder->check, coder->block->check, 101 out + out_start, out_used); 102 103 if (ret != LZMA_STREAM_END) 104 return ret; 105 106 // Compressed and Uncompressed Sizes are now at their final 107 // values. Verify that they match the values given to us. 108 if (!is_size_valid(coder->compressed_size, 109 coder->block->compressed_size) 110 || !is_size_valid(coder->uncompressed_size, 111 coder->block->uncompressed_size)) 112 return LZMA_DATA_ERROR; 113 114 // Copy the values into coder->block. The caller 115 // may use this information to construct Index. 116 coder->block->compressed_size = coder->compressed_size; 117 coder->block->uncompressed_size = coder->uncompressed_size; 118 119 coder->sequence = SEQ_PADDING; 120 } 121 122 // Fall through 123 124 case SEQ_PADDING: 125 // Compressed Data is padded to a multiple of four bytes. 126 while (coder->compressed_size & 3) { 127 if (*in_pos >= in_size) 128 return LZMA_OK; 129 130 // We use compressed_size here just get the Padding 131 // right. The actual Compressed Size was stored to 132 // coder->block already, and won't be modified by 133 // us anymore. 134 ++coder->compressed_size; 135 136 if (in[(*in_pos)++] != 0x00) 137 return LZMA_DATA_ERROR; 138 } 139 140 if (coder->block->check == LZMA_CHECK_NONE) 141 return LZMA_STREAM_END; 142 143 lzma_check_finish(&coder->check, coder->block->check); 144 coder->sequence = SEQ_CHECK; 145 146 // Fall through 147 148 case SEQ_CHECK: { 149 const size_t check_size = lzma_check_size(coder->block->check); 150 lzma_bufcpy(in, in_pos, in_size, coder->block->raw_check, 151 &coder->check_pos, check_size); 152 if (coder->check_pos < check_size) 153 return LZMA_OK; 154 155 // Validate the Check only if we support it. 156 // coder->check.buffer may be uninitialized 157 // when the Check ID is not supported. 158 if (lzma_check_is_supported(coder->block->check) 159 && memcmp(coder->block->raw_check, 160 coder->check.buffer.u8, 161 check_size) != 0) 162 return LZMA_DATA_ERROR; 163 164 return LZMA_STREAM_END; 165 } 166 } 167 168 return LZMA_PROG_ERROR; 169 } 170 171 172 static void 173 block_decoder_end(lzma_coder *coder, lzma_allocator *allocator) 174 { 175 lzma_next_end(&coder->next, allocator); 176 lzma_free(coder, allocator); 177 return; 178 } 179 180 181 extern lzma_ret 182 lzma_block_decoder_init(lzma_next_coder *next, lzma_allocator *allocator, 183 lzma_block *block) 184 { 185 lzma_next_coder_init(&lzma_block_decoder_init, next, allocator); 186 187 // Validate the options. lzma_block_unpadded_size() does that for us 188 // except for Uncompressed Size and filters. Filters are validated 189 // by the raw decoder. 190 if (lzma_block_unpadded_size(block) == 0 191 || !lzma_vli_is_valid(block->uncompressed_size)) 192 return LZMA_PROG_ERROR; 193 194 // Allocate and initialize *next->coder if needed. 195 if (next->coder == NULL) { 196 next->coder = lzma_alloc(sizeof(lzma_coder), allocator); 197 if (next->coder == NULL) 198 return LZMA_MEM_ERROR; 199 200 next->code = &block_decode; 201 next->end = &block_decoder_end; 202 next->coder->next = LZMA_NEXT_CODER_INIT; 203 } 204 205 // Basic initializations 206 next->coder->sequence = SEQ_CODE; 207 next->coder->block = block; 208 next->coder->compressed_size = 0; 209 next->coder->uncompressed_size = 0; 210 211 // If Compressed Size is not known, we calculate the maximum allowed 212 // value so that encoded size of the Block (including Block Padding) 213 // is still a valid VLI and a multiple of four. 214 next->coder->compressed_limit 215 = block->compressed_size == LZMA_VLI_UNKNOWN 216 ? (LZMA_VLI_MAX & ~LZMA_VLI_C(3)) 217 - block->header_size 218 - lzma_check_size(block->check) 219 : block->compressed_size; 220 221 // Initialize the check. It's caller's problem if the Check ID is not 222 // supported, and the Block decoder cannot verify the Check field. 223 // Caller can test lzma_check_is_supported(block->check). 224 next->coder->check_pos = 0; 225 lzma_check_init(&next->coder->check, block->check); 226 227 // Initialize the filter chain. 228 return lzma_raw_decoder_init(&next->coder->next, allocator, 229 block->filters); 230 } 231 232 233 extern LZMA_API(lzma_ret) 234 lzma_block_decoder(lzma_stream *strm, lzma_block *block) 235 { 236 lzma_next_strm_init(lzma_block_decoder_init, strm, block); 237 238 strm->internal->supported_actions[LZMA_RUN] = true; 239 strm->internal->supported_actions[LZMA_FINISH] = true; 240 241 return LZMA_OK; 242 } 243