1207753Smm/////////////////////////////////////////////////////////////////////////////// 2207753Smm// 3207753Smm/// \file block_header_decoder.c 4207753Smm/// \brief Decodes Block Header from .xz files 5207753Smm// 6207753Smm// Author: Lasse Collin 7207753Smm// 8207753Smm// This file has been put into the public domain. 9207753Smm// You can do whatever you want with this file. 10207753Smm// 11207753Smm/////////////////////////////////////////////////////////////////////////////// 12207753Smm 13207753Smm#include "common.h" 14207753Smm#include "check.h" 15207753Smm 16207753Smm 17207753Smmstatic void 18278433Srpaulofree_properties(lzma_block *block, const lzma_allocator *allocator) 19207753Smm{ 20207753Smm // Free allocated filter options. The last array member is not 21207753Smm // touched after the initialization in the beginning of 22207753Smm // lzma_block_header_decode(), so we don't need to touch that here. 23207753Smm for (size_t i = 0; i < LZMA_FILTERS_MAX; ++i) { 24207753Smm lzma_free(block->filters[i].options, allocator); 25207753Smm block->filters[i].id = LZMA_VLI_UNKNOWN; 26207753Smm block->filters[i].options = NULL; 27207753Smm } 28207753Smm 29207753Smm return; 30207753Smm} 31207753Smm 32207753Smm 33207753Smmextern LZMA_API(lzma_ret) 34207753Smmlzma_block_header_decode(lzma_block *block, 35278433Srpaulo const lzma_allocator *allocator, const uint8_t *in) 36207753Smm{ 37207753Smm // NOTE: We consider the header to be corrupt not only when the 38207753Smm // CRC32 doesn't match, but also when variable-length integers 39207753Smm // are invalid or over 63 bits, or if the header is too small 40207753Smm // to contain the claimed information. 41207753Smm 42207753Smm // Initialize the filter options array. This way the caller can 43207753Smm // safely free() the options even if an error occurs in this function. 44207753Smm for (size_t i = 0; i <= LZMA_FILTERS_MAX; ++i) { 45207753Smm block->filters[i].id = LZMA_VLI_UNKNOWN; 46207753Smm block->filters[i].options = NULL; 47207753Smm } 48207753Smm 49278433Srpaulo // Versions 0 and 1 are supported. If a newer version was specified, 50278433Srpaulo // we need to downgrade it. 51278433Srpaulo if (block->version > 1) 52278433Srpaulo block->version = 1; 53207753Smm 54278433Srpaulo // This isn't a Block Header option, but since the decompressor will 55278433Srpaulo // read it if version >= 1, it's better to initialize it here than 56278433Srpaulo // to expect the caller to do it since in almost all cases this 57278433Srpaulo // should be false. 58278433Srpaulo block->ignore_check = false; 59278433Srpaulo 60207753Smm // Validate Block Header Size and Check type. The caller must have 61207753Smm // already set these, so it is a programming error if this test fails. 62207753Smm if (lzma_block_header_size_decode(in[0]) != block->header_size 63207753Smm || (unsigned int)(block->check) > LZMA_CHECK_ID_MAX) 64207753Smm return LZMA_PROG_ERROR; 65207753Smm 66207753Smm // Exclude the CRC32 field. 67207753Smm const size_t in_size = block->header_size - 4; 68207753Smm 69207753Smm // Verify CRC32 70360523Sdelphij if (lzma_crc32(in, in_size, 0) != read32le(in + in_size)) 71207753Smm return LZMA_DATA_ERROR; 72207753Smm 73207753Smm // Check for unsupported flags. 74207753Smm if (in[1] & 0x3C) 75207753Smm return LZMA_OPTIONS_ERROR; 76207753Smm 77207753Smm // Start after the Block Header Size and Block Flags fields. 78207753Smm size_t in_pos = 2; 79207753Smm 80207753Smm // Compressed Size 81207753Smm if (in[1] & 0x40) { 82207753Smm return_if_error(lzma_vli_decode(&block->compressed_size, 83207753Smm NULL, in, &in_pos, in_size)); 84207753Smm 85207753Smm // Validate Compressed Size. This checks that it isn't zero 86207753Smm // and that the total size of the Block is a valid VLI. 87207753Smm if (lzma_block_unpadded_size(block) == 0) 88207753Smm return LZMA_DATA_ERROR; 89207753Smm } else { 90207753Smm block->compressed_size = LZMA_VLI_UNKNOWN; 91207753Smm } 92207753Smm 93207753Smm // Uncompressed Size 94207753Smm if (in[1] & 0x80) 95207753Smm return_if_error(lzma_vli_decode(&block->uncompressed_size, 96207753Smm NULL, in, &in_pos, in_size)); 97207753Smm else 98207753Smm block->uncompressed_size = LZMA_VLI_UNKNOWN; 99207753Smm 100207753Smm // Filter Flags 101360523Sdelphij const size_t filter_count = (in[1] & 3U) + 1; 102207753Smm for (size_t i = 0; i < filter_count; ++i) { 103207753Smm const lzma_ret ret = lzma_filter_flags_decode( 104207753Smm &block->filters[i], allocator, 105207753Smm in, &in_pos, in_size); 106207753Smm if (ret != LZMA_OK) { 107207753Smm free_properties(block, allocator); 108207753Smm return ret; 109207753Smm } 110207753Smm } 111207753Smm 112207753Smm // Padding 113207753Smm while (in_pos < in_size) { 114207753Smm if (in[in_pos++] != 0x00) { 115207753Smm free_properties(block, allocator); 116207753Smm 117207753Smm // Possibly some new field present so use 118207753Smm // LZMA_OPTIONS_ERROR instead of LZMA_DATA_ERROR. 119207753Smm return LZMA_OPTIONS_ERROR; 120207753Smm } 121207753Smm } 122207753Smm 123207753Smm return LZMA_OK; 124207753Smm} 125