Small oversight in 3.11 gzip.decompress implementation with regards to backwards compatibility

[rhpvorderman]

BPO	45507
Nosy	@ambv, @rhpvorderman
PRs	bpo-45507: Throw EOF error when gzip headers or trailers are truncated #29023 bpo-45507: EOFErrors should be thrown for truncated gzip members #29029

^{Note: these values reflect the state of the issue at the time it was migrated and might not reflect the current state.}

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GitHub fields:

assignee = None
closed_at = <Date 2021-11-19.18:44:42.893>
created_at = <Date 2021-10-18.08:51:32.403>
labels = ['type-bug', 'library', '3.11']
title = 'Small oversight in 3.11 gzip.decompress implementation with regards to backwards compatibility'
updated_at = <Date 2021-11-19.18:44:42.892>
user = 'https://github.com/rhpvorderman'

bugs.python.org fields:

activity = <Date 2021-11-19.18:44:42.892>
actor = 'lukasz.langa'
assignee = 'none'
closed = True
closed_date = <Date 2021-11-19.18:44:42.893>
closer = 'lukasz.langa'
components = ['Library (Lib)']
creation = <Date 2021-10-18.08:51:32.403>
creator = 'rhpvorderman'
dependencies = []
files = []
hgrepos = []
issue_num = 45507
keywords = ['patch']
message_count = 5.0
messages = ['404165', '404169', '405782', '406603', '406608']
nosy_count = 2.0
nosy_names = ['lukasz.langa', 'rhpvorderman']
pr_nums = ['29023', '29029']
priority = 'normal'
resolution = 'fixed'
stage = 'resolved'
status = 'closed'
superseder = None
type = 'behavior'
url = 'https://bugs.python.org/issue45507'
versions = ['Python 3.11']

[rhpvorderman]

A 'struct.error: unpack requires a buffer of 8 bytes' is thrown when a gzip trailer is truncated instead of an EOFError such as in the 3.10 and prior releases.

[rhpvorderman]

It turns out there is a bug where FNAME and/or FCOMMENT flags are set in the header, but no error is thrown when NAME and COMMENT fields are missing.

[rhpvorderman]

bump. This is a regression introduced by #27941

[ambv]

New changeset 0ff3d95 by Ruben Vorderman in branch 'main':
bpo-45507: EOFErrors should be thrown for truncated gzip members (GH-29029)
0ff3d95

[ambv]

Thanks for noticing, Ruben! ✨ 🍰 ✨