mirror of https://git.tukaani.org/xz.git
121 lines
3.7 KiB
C
121 lines
3.7 KiB
C
///////////////////////////////////////////////////////////////////////////////
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//
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/// \file block_header_decoder.c
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/// \brief Decodes Block Header from .lzma files
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//
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// Copyright (C) 2007 Lasse Collin
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//
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// This library is free software; you can redistribute it and/or
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// modify it under the terms of the GNU Lesser General Public
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// License as published by the Free Software Foundation; either
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// version 2.1 of the License, or (at your option) any later version.
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//
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// This library is distributed in the hope that it will be useful,
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// but WITHOUT ANY WARRANTY; without even the implied warranty of
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// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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// Lesser General Public License for more details.
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//
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///////////////////////////////////////////////////////////////////////////////
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#include "common.h"
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#include "check.h"
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static void
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free_properties(lzma_block *options, lzma_allocator *allocator)
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{
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// Free allocated filter options. The last array member is not
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// touched after the initialization in the beginning of
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// lzma_block_header_decode(), so we don't need to touch that here.
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for (size_t i = 0; i < LZMA_FILTERS_MAX; ++i) {
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lzma_free(options->filters[i].options, allocator);
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options->filters[i].id = LZMA_VLI_UNKNOWN;
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options->filters[i].options = NULL;
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}
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return;
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}
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extern LZMA_API lzma_ret
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lzma_block_header_decode(lzma_block *options,
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lzma_allocator *allocator, const uint8_t *in)
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{
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// NOTE: We consider the header to be corrupt not only when the
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// CRC32 doesn't match, but also when variable-length integers
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// are invalid or over 63 bits, or if the header is too small
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// to contain the claimed information.
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// Initialize the filter options array. This way the caller can
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// safely free() the options even if an error occurs in this function.
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for (size_t i = 0; i <= LZMA_FILTERS_MAX; ++i) {
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options->filters[i].id = LZMA_VLI_UNKNOWN;
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options->filters[i].options = NULL;
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}
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// Validate Block Header Size and Check type. The caller must have
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// already set these, so it is a programming error if this test fails.
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if (lzma_block_header_size_decode(in[0]) != options->header_size
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|| (unsigned int)(options->check) > LZMA_CHECK_ID_MAX)
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return LZMA_PROG_ERROR;
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// Exclude the CRC32 field.
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const size_t in_size = options->header_size - 4;
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// Verify CRC32
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if (lzma_crc32(in, in_size, 0) != integer_read_32(in + in_size))
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return LZMA_DATA_ERROR;
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// Check for unsupported flags.
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if (in[1] & 0x3C)
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return LZMA_OPTIONS_ERROR;
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// Start after the Block Header Size and Block Flags fields.
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size_t in_pos = 2;
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// Compressed Size
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if (in[1] & 0x40) {
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return_if_error(lzma_vli_decode(&options->compressed_size,
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NULL, in, &in_pos, in_size));
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// Validate Compressed Size. This checks that it isn't zero
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// and that the total size of the Block is a valid VLI.
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if (lzma_block_unpadded_size(options) == 0)
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return LZMA_DATA_ERROR;
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} else {
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options->compressed_size = LZMA_VLI_UNKNOWN;
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}
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// Uncompressed Size
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if (in[1] & 0x80)
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return_if_error(lzma_vli_decode(&options->uncompressed_size,
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NULL, in, &in_pos, in_size));
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else
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options->uncompressed_size = LZMA_VLI_UNKNOWN;
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// Filter Flags
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const size_t filter_count = (in[1] & 3) + 1;
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for (size_t i = 0; i < filter_count; ++i) {
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const lzma_ret ret = lzma_filter_flags_decode(
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&options->filters[i], allocator,
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in, &in_pos, in_size);
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if (ret != LZMA_OK) {
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free_properties(options, allocator);
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return ret;
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}
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}
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// Padding
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while (in_pos < in_size) {
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if (in[in_pos++] != 0x00) {
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free_properties(options, allocator);
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// Possibly some new field present so use
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// LZMA_OPTIONS_ERROR instead of LZMA_DATA_ERROR.
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return LZMA_OPTIONS_ERROR;
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}
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}
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return LZMA_OK;
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}
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