kissgyorgy
commented
1 month ago Here is how to make such a file:
$ cat somefile.txt | zip > zip64.zip
$ zip -F zip64.zip --out zip64-without-cd.zip
$ zipdetails zip64-without-cd.zip
0000 LOCAL HEADER #1 04034B50
0004 Extract Zip Spec 2D '4.5'
0005 Extract OS 00 'MS-DOS'
0006 General Purpose Flag 0000
[Bits 1-2] 0 'Normal Compression'
0008 Compression Method 0008 'Deflated'
000A Last Mod Time 58F75520 'Tue Jul 23 10:41:00 2024'
000E CRC 79AADA01
0012 Compressed Length FFFFFFFF
0016 Uncompressed Length FFFFFFFF
001A Filename Length 0001
001C Extra Length 0014
001E Filename '-'
001F Extra ID #0001 0001 'ZIP64'
0021 Length 0010
0023 Uncompressed Size 000000000000005E
002B Compressed Size 000000000000004D
0033 PAYLOAD -
.1..0...........R.....7&.|.9b...db....'.
..`.JzQ.i......4..j..M..1..4...].S,/
0080 CENTRAL HEADER #1 02014B50
0084 Created Zip Spec 1E '3.0'
0085 Created OS 03 'Unix'
0086 Extract Zip Spec 2D '4.5'
0087 Extract OS 00 'MS-DOS'
0088 General Purpose Flag 0000
[Bits 1-2] 0 'Normal Compression'
008A Compression Method 0008 'Deflated'
008C Last Mod Time 58F75520 'Tue Jul 23 10:41:00 2024'
0090 CRC 79AADA01
0094 Compressed Length 0000004D
0098 Uncompressed Length 0000005E
009C Filename Length 0001
009E Extra Length 0000
00A0 Comment Length 0000
00A2 Disk Start 0000
00A4 Int File Attributes 0001
[Bit 0] 1 Text Data
00A6 Ext File Attributes 11800000
00AA Local Header Offset 00000000
00AE Filename '-'
ADD 0 77 CENTRAL HEADER ref Local #1: -
00AF END CENTRAL HEADER 06054B50
00B3 Number of this disk 0000
00B5 Central Dir Disk no 0000
00B7 Entries in this disk 0001
00B9 Total Entries 0001
00BB Size of Central Dir 0000002F
00BF Offset to Central Dir 00000080
00C3 Comment Length 0000
Done
We have identified a possibility for the zip handler to miss label a zip file (zip, zip64).
Its possible for a zip file to contain FFFF values (indicating it's a zip64) but it does not hold a zip64 End of Central Directory.
If that happens, the zip handler will just raise an InvalidInputFormat and skip the valid zip file