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std.compress.zstandard: verify checksum in decodeFrameAlloc()

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This commit is contained in:
dweiller 2023-01-28 22:02:08 +11:00
parent 3bfba36548
commit e92575d3d4
1 changed files with 21 additions and 12 deletions
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33
lib/std/compress/zstandard/decompress.zig
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@ -573,6 +573,11 @@ const literal_table_size_max = 1 << types.compressed_block.table_accuracy_log_ma
const match_table_size_max = 1 << types.compressed_block.table_accuracy_log_max.match;
const offset_table_size_max = 1 << types.compressed_block.table_accuracy_log_max.match;
pub fn computeChecksum(hasher: *std.hash.XxHash64) u32 {
const hash = hasher.final();
return @intCast(u32, hash & 0xFFFFFFFF);
}
const FrameError = error{
DictionaryIdFlagUnsupported,
ChecksumFailure,
@ -601,24 +606,20 @@ pub fn decodeZStandardFrame(
if (dest.len < content_size) return error.ContentTooLarge;
const should_compute_checksum = frame_header.descriptor.content_checksum_flag and verify_checksum;
var hash_state = if (should_compute_checksum) std.hash.XxHash64.init(0) else undefined;
var hasher_opt = if (should_compute_checksum) std.hash.XxHash64.init(0) else null;
const written_count = try decodeFrameBlocks(
dest,
src[consumed_count..],
&consumed_count,
if (should_compute_checksum) &hash_state else null,
if (hasher_opt) |*hasher| hasher else null,
);
if (frame_header.descriptor.content_checksum_flag) {
const checksum = readIntSlice(u32, src[consumed_count .. consumed_count + 4]);
consumed_count += 4;
if (verify_checksum) {
const hash = hash_state.final();
const hash_low_bytes = hash & 0xFFFFFFFF;
if (checksum != hash_low_bytes) {
return error.ChecksumFailure;
}
if (hasher_opt) |*hasher| {
if (checksum != computeChecksum(hasher)) return error.ChecksumFailure;
}
}
return ReadWriteCount{ .read_count = consumed_count, .write_count = written_count };
@ -649,7 +650,7 @@ pub fn decodeZStandardFrameAlloc(
@intCast(usize, window_size_raw);
const should_compute_checksum = frame_header.descriptor.content_checksum_flag and verify_checksum;
var hash = if (should_compute_checksum) std.hash.XxHash64.init(0) else null;
var hasher_opt = if (should_compute_checksum) std.hash.XxHash64.init(0) else null;
const block_size_maximum = @min(1 << 17, window_size);
@ -707,12 +708,20 @@ pub fn decodeZStandardFrameAlloc(
const written_slice = ring_buffer.sliceLast(written_size);
try result.appendSlice(written_slice.first);
try result.appendSlice(written_slice.second);
if (hash) |*hash_state| {
hash_state.update(written_slice.first);
hash_state.update(written_slice.second);
if (hasher_opt) |*hasher| {
hasher.update(written_slice.first);
hasher.update(written_slice.second);
}
if (block_header.last_block) break;
}
if (frame_header.descriptor.content_checksum_flag) {
const checksum = readIntSlice(u32, src[consumed_count .. consumed_count + 4]);
consumed_count += 4;
if (hasher_opt) |*hasher| {
if (checksum != computeChecksum(hasher)) return error.ChecksumFailure;
}
}
return result.toOwnedSlice();
}