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bpo-45509: Check gzip headers for corrupted fields #29028

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bpo-45509: Check gzip headers for corrupted fields #29028

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617e064
Check gzip headers for corrupted fields
rhpvorderman Oct 18, 2021
3d5bb47
Minor performance tweaks to _read_gzip_header
rhpvorderman Nov 24, 2021
e68e76e
Optimize _read_gzip_header for the most common code paths
rhpvorderman Nov 24, 2021
2dfc96c
Merge branch 'main' into bpo-45509
hauntsaninja Jan 30, 2023
65108b6
Merge branch 'main' into bpo-45509
rhpvorderman Apr 10, 2026
64ad8e9
Update test_gzip.py
rhpvorderman Apr 10, 2026
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Minor performance tweaks to _read_gzip_header 
Call the bool method and cache the result for faster truth checking.
Do not test for empty bytes but use "not magic" instead for faster truth checking.
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@rhpvorderman
rhpvorderman committed Nov 24, 2021
commit 3d5bb4726fd4122233849d2f47e00f97b6aff2ea
4 changes: 2 additions & 2 deletions Lib/gzip.py
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Expand Up @@ -421,7 +421,7 @@ def _read_gzip_header(fp):
Returns last mtime if header was present or None otherwise.
'''
magic = fp.read(2)
if magic == b'':
if not magic:
return None

if magic != b'\037\213':
Expand All @@ -432,7 +432,7 @@ def _read_gzip_header(fp):
raise BadGzipFile('Unknown compression method')

# FHCRC will be checked often. So save the result of the check.
fhcrc = flag & FHCRC
fhcrc = bool(flag & FHCRC)
# Only create and append to a list of header parts when FHCRC is set.
# In the most common use cases FHCRC is not set. So we optimize for those
# cases.
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