RyanSkraba commented on code in PR #3861:
URL: https://github.com/apache/avro/pull/3861#discussion_r3610597907
##########
lang/py/avro/io.py:
##########
@@ -393,12 +459,28 @@ def skip_double(self) -> None:
self.skip(8)
def skip_bytes(self) -> None:
- self.skip(self.read_long())
+ # The length prefix is attacker-controlled: a negative value would seek
+ # backwards (corrupting the decoder position, e.g. an infinite loop
+ # during schema resolution) and an oversized value past EOF. Validate
it
+ # the same way ``read`` does before skipping.
+ n = self.read_long()
+ if n < 0:
+ raise avro.errors.InvalidAvroBinaryEncoding(f"Requested {n} bytes
to skip, expected positive integer.")
Review Comment:
Redundant with skip(n) also checking negative bytes -- remove or align error
messages?
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