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LibAudio: Compute and verify FLAC frame header checksums

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This is currently not a failure condition, but we will print out a
message to the console informing the user of a potential corrupted file.
This commit is contained in:
kleines Filmröllchen 2023-05-18 16:01:12 +02:00 • committed by Jelle Raaijmakers
parent 70ab4566f3
commit 3b8ccd123b
3 changed files with 21 additions and 7 deletions
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19
Userland/Libraries/LibAudio/FlacLoader.cpp
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@ -24,6 +24,8 @@
#include <LibAudio/Resampler.h>
#include <LibAudio/VorbisComment.h>
#include <LibCore/File.h>
#include <LibCrypto/Checksum/ChecksumFunction.h>
#include <LibCrypto/Checksum/ChecksummingStream.h>
namespace Audio {
@ -367,9 +369,10 @@ LoaderSamples FlacLoaderPlugin::next_frame()
dbgln("FLAC Warning: Inserting seek point for sample {} failed: {}", sample_index, maybe_error.release_error());
}
BigEndianInputBitStream bit_stream { MaybeOwned<Stream>(*m_stream) };
auto checksum_stream = TRY(try_make<Crypto::Checksum::ChecksummingStream<FlacFrameHeaderCRC>>(MaybeOwned<Stream>(*m_stream)));
BigEndianInputBitStream bit_stream { MaybeOwned<Stream> { *checksum_stream } };
// TODO: Check the CRC-16 checksum (and others) by keeping track of read data
// TODO: Check the CRC-16 checksum by keeping track of read data.
// 11.22. FRAME_HEADER
u16 sync_code = LOADER_TRY(bit_stream.read_bits<u16>(14));
@ -393,7 +396,6 @@ LoaderSamples FlacLoaderPlugin::next_frame()
FLAC_VERIFY(reserved_bit == 0, LoaderError::Category::Format, "Reserved frame header end bit");
// 11.22.8. CODED NUMBER
// FIXME: sample number can be 8-56 bits, frame number can be 8-48 bits
m_current_sample_or_frame = LOADER_TRY(read_utf8_char(bit_stream));
// Conditional header variables
@ -413,17 +415,22 @@ LoaderSamples FlacLoaderPlugin::next_frame()
frame_sample_rate = LOADER_TRY(bit_stream.read_bits<u32>(16)) * 10;
}
// It does not matter whether we extract the checksum from the digest here, or extract the digest 0x00 after processing the checksum.
auto const calculated_checksum = checksum_stream->digest();
// 11.22.11. FRAME CRC
// TODO: check header checksum, see above
[[maybe_unused]] u8 checksum = LOADER_TRY(bit_stream.read_bits<u8>(8));
u8 specified_checksum = LOADER_TRY(bit_stream.read_bits<u8>(8));
VERIFY(bit_stream.is_aligned_to_byte_boundary());
if (specified_checksum != calculated_checksum)
dbgln("FLAC frame {}: Calculated header checksum {:02x} is different from specified checksum {:02x}", m_current_sample_or_frame, calculated_checksum, specified_checksum);
dbgln_if(AFLACLOADER_DEBUG, "Frame: {} samples, {}bit {}Hz, channeltype {:x}, {} number {}, header checksum {}", sample_count, bit_depth, frame_sample_rate, channel_type_num, blocking_strategy ? "sample" : "frame", m_current_sample_or_frame, checksum);
dbgln_if(AFLACLOADER_DEBUG, "Frame: {} samples, {}bit {}Hz, channeltype {:x}, {} number {}, header checksum {:02x}{}", sample_count, bit_depth, frame_sample_rate, channel_type_num, blocking_strategy ? "sample" : "frame", m_current_sample_or_frame, specified_checksum, specified_checksum != calculated_checksum ? " (checksum error)"sv : ""sv);
m_current_frame = FlacFrameHeader {
sample_count,
frame_sample_rate,
channel_type,
bit_depth,
specified_checksum,
};
u8 subframe_count = frame_channel_type_to_channel_count(channel_type);