Wrong extract version set in local headers for files located beyond zip64 limit
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Descripción
Bug report
Bug description:
When creating a zip file which contains a file large enough to push additional files beyond the ZIP64_LIMIT, the extract version is correctly incremented to 4.5 in the Central Header, but not in the Local Header. This mismatch is usually ignored, but more picky implementations fail when validating the zip file.
When the Local Header is being generated, the extract version that is used does not account for the fact that if the header is located farther than the ZIP64_LIMIT, the ZIP64_VERSION is needed since to reference the header offset the Central Header needs to store the offset in the Extra Bits.
Repro
Create a directory with a file over the ZIP64_LIMIT and a file after it, then zip the directory:
>tree source_dir/ -h
source_dir/
├── [4.7G] 5_gig_file.dat
└── [ 229] t
# Zip the test directory
out_file = "outputs/test.zip"
source_dir = "source_dir"
with zipfile.ZipFile(out_file, "w") as zipf:
for root, _dirs, files in os.walk(source_dir):
for file in files:
file_path = os.path.join(root, file)
arc_path = pathlib.Path(file_path).relative_to(source_dir)
zipf.write(file_path, arcname=arc_path)
print(f"generated {out_file}")
Using zipdetails we can see the extract_version in the local header does not match the central header:
> zipdetails outputs/test.zip
...
12A05F240 LOCAL HEADER #2 04034B50
12A05F244 Extract Zip Spec 14 '2.0'
12A05F245 Extract OS 00 'MS-DOS'
12A05F246 General Purpose Flag 0000
12A05F248 Compression Method 0000 'Stored'
12A05F24A Last Mod Time 58DCB5CE 'Fri Jun 28 22:46:28 2024'
12A05F24E CRC BB63C172
12A05F252 Compressed Length 000000E5
12A05F256 Uncompressed Length 000000E5
12A05F25A Filename Length 0008
12A05F25C Extra Length 0000
12A05F25E Filename 'test.TXT'
...
12A05F39B CENTRAL HEADER #2 02014B50
12A05F39F Created Zip Spec 2D '4.5'
12A05F3A0 Created OS 00 'MS-DOS'
12A05F3A1 Extract Zip Spec 2D '4.5'
12A05F3A2 Extract OS 00 'MS-DOS'
12A05F3A3 General Purpose Flag 0000
12A05F3A5 Compression Method 0000 'Stored'
12A05F3A7 Last Mod Time 58DCB5CE 'Fri Jun 28 22:46:28 2024'
12A05F3AB CRC BB63C172
12A05F3AF Compressed Length 000000E5
12A05F3B3 Uncompressed Length 000000E5
12A05F3B7 Filename Length 0008
12A05F3B9 Extra Length 000C
12A05F3BB Comment Length 0000
12A05F3BD Disk Start 0000
12A05F3BF Int File Attributes 0000
[Bit 0] 0 'Binary Data'
12A05F3C1 Ext File Attributes 81B60000
12A05F3C5 Local Header Offset FFFFFFFF
12A05F3C9 Filename 'test.TXT'
12A05F3D1 Extra ID #0001 0001 'ZIP64'
12A05F3D3 Length 0008
12A05F3D5 Offset to Central 000000012A05F240
Dir
12A05F3DD ZIP64 END CENTRAL DIR 06064B50
RECORD
12A05F3E1 Size of record 000000000000002C
12A05F3E9 Created Zip Spec 2D '4.5'
12A05F3EA Created OS 00 'MS-DOS'
12A05F3EB Extract Zip Spec 2D '4.5'
12A05F3EC Extract OS 00 'MS-DOS'
12A05F3ED Number of this disk 00000000
12A05F3F1 Central Dir Disk no 00000000
12A05F3F5 Entries in this disk 0000000000000002
12A05F3FD Total Entries 0000000000000002
12A05F405 Size of Central Dir 0000000000000092
12A05F40D Offset to Central dir 000000012A05F34B
12A05F415 ZIP64 END CENTRAL DIR 07064B50
LOCATOR
12A05F419 Central Dir Disk no 00000000
12A05F41D Offset to Central dir 000000012A05F3DD
12A05F425 Total no of Disks 00000001
12A05F429 END CENTRAL HEADER 06054B50
12A05F42D Number of this disk 0000
12A05F42F Central Dir Disk no 0000
12A05F431 Entries in this disk 0002
12A05F433 Total Entries 0002
12A05F435 Size of Central Dir 00000092
12A05F439 Offset to Central Dir FFFFFFFF
12A05F43D Comment Length 0000
The zip -F command also warns about the mismatch:
zip --version
Copyright (c) 1990-2008 Info-ZIP - Type 'zip "-L"' for software license.
This is Zip 3.0 (July 5th 2008), by Info-ZIP.
...
> zip -F outputs/test.zip --out out2.zip
Fix archive (-F) - assume mostly intact archive
Zip entry offsets do not need adjusting
copying: 5_gig_file.dat
copying: test.TXT
zip warning: Local Version Needed To Extract does not match CD: test.TXT
CPython versions tested on:
3.10, CPython main branch
Operating systems tested on:
Linux, Windows
Linked PRs
- gh-121177
Guía de contribución
Primeros pasos
- Lee el issue completo y luego la guía de contribución del proyecto.
- Comenta en el issue que vas a ocuparte — evita que dos personas hagan lo mismo.
- Haz un fork del repositorio y trabaja en una rama.
- Abre un pull request que haga referencia al número del issue.
Línea de trabajo
Comienza en la ruta de escritura de archivos de zipfile.ZipFile y sigue cómo se elige la versión necesaria para la extracción para los encabezados local y central cuando el desplazamiento de una entrada supera ZIP64_LIMIT. Reproduce el archivo con un archivo que supere el límite, inspecciónalo con zipdetails y compara las versiones de los encabezados local y central. Se considera terminado cuando los encabezados coinciden y ya no aparece la advertencia de zip -F.
Escrito por el modelo de indexación a partir del texto del issue.
Evaluación
- Stack tecnológico
- python
- Área
- tooling
- Tipo de issue
- Error
- Dificultad
- 4/5
- Tiempo estimado
- 3-5 días
- Estado de actividad
- Estancado
- Claridad
- Bastante claro
- Aptitud para principiantes
- 35/100