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LibCompress: Process XZ filters in reverse order

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XZ writes filters in the order that they are used during compression, so
we need to process them in the reverse order while decompression.

This wasn't noticed earlier because we only supported the LZMA2 filter.
This commit is contained in:
Tim Schumacher 2023-10-22 19:47:50 +02:00 • committed by Jelle Raaijmakers
parent 6a7b9b85a4
commit f0b08e9dea
1 changed files with 14 additions and 3 deletions
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17
Userland/Libraries/LibCompress/Xz.cpp
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@ -316,6 +316,13 @@ ErrorOr<void> XzDecompressor::load_next_block(u8 encoded_block_header_size)
m_current_block_expected_uncompressed_size.clear();
}
// We need to process the filters in reverse order, since they are listed in the order that they have been applied in.
struct FilterEntry {
u64 id;
ByteBuffer properties;
};
Vector<FilterEntry, 4> filters;
// 3.1.5. List of Filter Flags:
// "The number of Filter Flags fields is stored in the Block Flags
// field (see Section 3.1.2)."
@ -330,12 +337,16 @@ ErrorOr<void> XzDecompressor::load_next_block(u8 encoded_block_header_size)
auto filter_properties = TRY(ByteBuffer::create_uninitialized(size_of_properties));
TRY(header_stream.read_until_filled(filter_properties));
filters.empend(filter_id, move(filter_properties));
}
for (auto& filter : filters.in_reverse()) {
// 5.3.1. LZMA2
if (filter_id == 0x21) {
if (size_of_properties < sizeof(XzFilterLzma2Properties))
if (filter.id == 0x21) {
if (filter.properties.size() < sizeof(XzFilterLzma2Properties))
return Error::from_string_literal("XZ LZMA2 filter has a smaller-than-needed properties size");
auto const* properties = reinterpret_cast<XzFilterLzma2Properties*>(filter_properties.data());
auto const* properties = reinterpret_cast<XzFilterLzma2Properties*>(filter.properties.data());
TRY(properties->validate());
new_block_stream = TRY(Lzma2Decompressor::create_from_raw_stream(move(new_block_stream), properties->dictionary_size()));