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