Copilot commented on code in PR #3855:
URL: https://github.com/apache/avro/pull/3855#discussion_r3564864645
##########
lang/perl/lib/Avro/DataFileReader.pm:
##########
@@ -215,24 +231,128 @@ sub read_block_header {
my $marker = substr $block, -(MARKER_SIZE), MARKER_SIZE, '';
$datafile->{block_marker} = $marker;
+ ## The decompressed size of a block is capped to guard against a block with
+ ## a very high compression ratio expanding to far more memory than its
+ ## compressed size. The limit is the AVRO_MAX_DECOMPRESS_LENGTH environment
+ ## variable, or DEFAULT_MAX_DECOMPRESS_LENGTH. (Note: block_max_size is a
+ ## writer-side flush threshold measured in compressed bytes and is not
reused
+ ## here to avoid conflating the two units.)
+ my $limit = _max_decompress_length();
+
## this is our new reader
$datafile->{reader} = do {
if ($codec eq 'deflate') {
- IO::Uncompress::RawInflate->new(\$block);
+ my $z = IO::Uncompress::RawInflate->new(\$block)
+ or croak "Error inflating block:
$IO::Uncompress::RawInflate::RawInflateError";
+ my $uncompressed = _inflate_bounded($z, $limit);
+ _open_decompressed(\$uncompressed);
}
elsif ($codec eq 'bzip2') {
- my $uncompressed;
- bunzip2 \$block => \$uncompressed;
- do { open $fh, '<', \$uncompressed; $fh };
+ my $z = IO::Uncompress::Bunzip2->new(\$block)
+ or croak "Error decompressing bzip2 block:
$IO::Uncompress::Bunzip2::Bunzip2Error";
+ my $uncompressed = _inflate_bounded($z, $limit);
+ _open_decompressed(\$uncompressed);
}
elsif ($codec eq 'zstandard') {
- do { open $fh, '<', \(decompress(\$block)); $fh };
+ my $uncompressed = _zstd_decompress_bounded(\$block, $limit);
+ _open_decompressed(\$uncompressed);
}
};
return;
}
+## Open an in-memory read handle over the decompressed block, surfacing any
+## failure via croak rather than leaving $datafile->{reader} undefined (which
+## would fail later with a less clear error). The handle keeps a reference to
+## the scalar, so the caller's buffer stays alive for the lifetime of the read.
+sub _open_decompressed {
+ my ($uncompressed_ref) = @_;
+ open my $fh, '<', $uncompressed_ref
+ or croak "Error opening decompressed block for reading: $!";
+ return $fh;
+}
+
+## Read from a streaming decompressor in chunks, rejecting the block as soon as
+## its decompressed size would exceed $limit so an over-large (or malicious)
+## block is not fully materialized in memory. Each read is sized to the
+## remaining budget (capped at 64 KiB) so the buffer overshoots $limit by at
+## most one byte before the check fires.
+sub _inflate_bounded {
+ my ($z, $limit) = @_;
+ my $uncompressed = '';
+ my $chunk;
+ my $status;
+ while (1) {
+ my $budget = $limit - bytes::length($uncompressed) + 1;
+ my $to_read = $budget < 65536 ? $budget : 65536;
+ $status = $z->read($chunk, $to_read);
+ last unless defined $status && $status > 0;
+ $uncompressed .= $chunk;
+ _check_decompress_length(bytes::length($uncompressed), $limit);
+ }
+ if (!defined $status || $status < 0) {
+ croak "Error decompressing block: " . $z->error;
+ }
+ return $uncompressed;
+}
+
+## Streaming zstandard decompression, bounded the same way as _inflate_bounded
so
+## a high-ratio block is rejected before its full form is materialized.
+sub _zstd_decompress_bounded {
+ my ($block_ref, $limit) = @_;
+ # Load the zstandard decompressor lazily so the reader still loads and
works
+ # for other codecs when Compress::Zstd::Decompressor is unavailable (e.g.
an
+ # older Compress::Zstd distribution that lacks the Decompressor submodule).
+ unless (eval { require Compress::Zstd::Decompressor; 1 }) {
+ Avro::DataFile::Error::UnsupportedCodec->throw(
+ "Cannot read zstandard-compressed block:
Compress::Zstd::Decompressor is not available"
+ );
+ }
Review Comment:
The zstandard path now requires `Compress::Zstd::Decompressor`, but the Perl
distribution only declares `requires 'Compress::Zstd'` (no minimum version) and
existing tests (e.g. `t/04_datafile.t`) exercise zstandard read/write
unconditionally. In environments where `Compress::Zstd` is present but lacks
the `Decompressor` submodule, this change will make zstandard decoding fail
with `UnsupportedCodec` and can break the test suite/CPAN installs unexpectedly.
Consider updating the Perl prerequisites to require a `Compress::Zstd`
version that provides `Compress::Zstd::Decompressor`, and/or adjusting existing
zstandard tests to SKIP when `Compress::Zstd::Decompressor` is unavailable so
the suite remains portable.
##########
lang/perl/lib/Avro/DataFileReader.pm:
##########
@@ -207,6 +212,17 @@ sub read_block_header {
return if $codec eq 'null';
+ ## Guard against an attacker-controlled block_size triggering a huge
+ ## allocation for the compressed block itself, before any decompression
+ ## happens. When the reader is configured with block_max_size, reject a
+ ## block whose declared compressed size exceeds that bound up front.
+ my $block_max = $datafile->{block_max_size};
+ if (defined $block_max && $datafile->{block_size} > $block_max) {
+ Avro::DataFile::Error::CompressedBlockSize->throw(
+ "Compressed block size $datafile->{block_size} exceeds the
configured block_max_size of $block_max bytes"
+ );
+ }
+
## we need to read the entire block into memory, to inflate it
my $nread = read $fh, my $block, $datafile->{block_size} + MARKER_SIZE
or croak "Error reading from file: $!";
Review Comment:
`read` is currently checked with `or croak`, which treats a short read / EOF
as an “error” (often with `$!` unset) and can yield confusing downstream
failures (bad marker / decompressor errors) on truncated or malformed files.
It’s safer to verify the exact byte count and throw a clear error on short
reads.
--
This is an automated message from the Apache Git Service.
To respond to the message, please log on to GitHub and use the
URL above to go to the specific comment.
To unsubscribe, e-mail: [email protected]
For queries about this service, please contact Infrastructure at:
[email protected]
