iemejia commented on code in PR #3864:
URL: https://github.com/apache/avro/pull/3864#discussion_r3567581847
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lang/perl/lib/Avro/BinaryDecoder.pm:
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@@ -206,7 +371,14 @@ sub decode_enum {
my ($writer_schema, $reader_schema, $reader) = @_;
my $index = decode_int($class, @_);
- my $w_data = $writer_schema->symbols->[$index];
+ my $symbols = $writer_schema->symbols;
+ ## A negative or out-of-range index is malformed; reject it before indexing
+ ## (Perl's negative indexing would otherwise select the wrong symbol).
+ if ($index < 0 || $index >= scalar @$symbols) {
+ throw Avro::Schema::Error::Parse(
+ "Enum symbol index $index out of range for " . scalar(@$symbols) .
" symbols");
+ }
Review Comment:
Unlike skip_union (where the branch index selects *which* schema to skip, so
a wrong index desyncs the stream), the enum index doesn't affect skipping: an
enum is encoded as just the index varint with nothing following it, so
skip_enum reads the varint and moves on regardless of the value. An
out-of-range index is therefore skipped correctly without desync or allocation,
so validating it here would only be for parity with decode_enum, not
correctness/safety. I've left skip_enum as skip_int to keep the skip path
minimal; happy to add the schema-aware check if you'd prefer strict parity.
##########
lang/perl/lib/Avro/BinaryDecoder.pm:
##########
@@ -273,7 +502,8 @@ sub decode_array {
sub skip_map {
my $class = shift;
my ($schema, $reader) = @_;
- skip_block($reader, sub {
+ # Map entries always carry a >= 1 byte key, so pass a positive minimum.
+ skip_block($reader, 1 + _min_bytes_per_element($schema->values), sub {
Review Comment:
Similarly, an empty map key is skipped correctly (a 0-length string = a
1-byte length prefix and no data), so it doesn't desync or over-read during
projection — decode_map rejects it for data validity, but skip only needs to
advance past it. So there's no correctness/security impact here; it's a
decode-vs-skip strictness parity point. Left as-is to keep skip minimal.
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