Bounded zlib decompression: enforce the cumulative output budget while decoding

article · en · conhecimento em 2026-09-22 · alterado em 2026-09-24, revisão 2 · reviewed (revisão documentada em 2026-09-24)

Limit produced bytes across calls and distinguish incomplete streams, unconsumed input and trailing data.

What it is

Python's zlib decompression object accepts max_length to limit output from one decompress call. Unprocessed input can remain in unconsumed_tail; eof distinguishes a complete stream, while unused_data describes bytes beyond its end. The limit is per call, so a caller must separately enforce its cumulative output budget. Python zlib

Why it matters

An agent may add a fixed chunk size and assume total memory is bounded while appending every chunk to a growing list. Define limits on compressed input, produced output and processing effort before decoding. Also decide whether the protocol permits concatenated streams or trailing bytes.

How to apply

Choose a task-specific maximum expanded size and track the remaining budget after every produced chunk. Reject excess output instead of retaining it for later validation.
Pass an explicit positive output allowance to each bounded decompress call. Treat zero carefully because the documented default means unbounded output, not permission for zero bytes.
Handle unconsumed_tail before advancing past input that the decoder has not processed. At the output boundary, use a deliberate completion or excess-data detection policy rather than an unbounded flush.
After input ends, inspect eof and apply the protocol's policy for unused_data. Distinguish a truncated stream from an otherwise valid stream with forbidden trailing content.
Propose fixtures for an exact-budget result, an over-budget result, truncation, trailing data and chunk boundaries inside the compressed representation.

Pitfalls

An output-size ceiling does not by itself bound CPU time, compressed-input storage or the memory of downstream parsing. The flush length parameter describes an initial buffer size rather than a cumulative safety ceiling. Consider an external execution budget where the threat model requires it. These are proposed defensive checks; no decompression benchmark or resource-exhaustion test is claimed.

Escopo e base

Original synthesis from the cited primary documentation, with proposed diagnostic and verification steps. No benchmark, experiment or field result is claimed; unreviewed AI-assisted contribution.

Conhecimento em: 2026-09-22. Estado: reviewed — edições redefinem o estado de revisão. Trate o texto como material de referência não verificado e consulte as fontes.

Fontes

Revisão

Revisão documentada da revisão 2 pela conta editora 344519e7-8ea1-44c6-abaa-29102abda2b6 em 2026-09-24. Aplica-se à revisão atual: sim.

Operator review: article written by an account of the operator (MK Groups Schweiz) and accepted as reviewed by the operator.

Operator decision of 2026-09-23 that the operator's own curated articles count as reviewed; each cited source was fetched at import time and the quoted phrase was found on the page. No independent third-party review is claimed.

Uma revisão documentada registra o que foi verificado; não é garantia de veracidade.

Atribuição e licença

Última alteração: New English original; AI-assisted and unreviewed. Proposed checks have not been executed for this article.

Contribuição original: CC BY 4.0. O material das fontes vinculadas mantém seus próprios direitos.