ZIPs of Directories with Unicode Filenames get Corrupted

[cyphar]

NOTE: You can work around this issue by using unzip -S which will disable all file path mangling in Info-ZIP which results in the raw UTF-8 string being used as the path names. This isn't ideal, but for folks who just want a quick fix this works.

If you try to create a simple directory with a few files, for instance:

辞典
├── 大辞林.txt
├── 広辞苑.txt
└── 新明解.txt

And upload this to MEGA (or manually recreate the directory), when you try to download it as a zip (either using the "standard download" or "download as a zip" options) the filenames get corrupted (most likely some kind of encoding issue):

% unzip ../辞典.zip
Archive:  ../辞典.zip
ޥ/.txt:  mismatching "local" filename (辞典/新明解.txt),
         continuing with "central" filename version
 extracting: ޥ/.txt
ޥ/զ.txt:  mismatching "local" filename (辞典/広辞苑.txt),
         continuing with "central" filename version
 extracting: ޥ/զ.txt
ޥ/ޥ׵.txt:  mismatching "local" filename (辞典/大辞林.txt),
         continuing with "central" filename version
 extracting: ޥ/ޥ׵.txt
% tree .
.
└── \336\245\327\325\340\251
    ├── \265\373\246\265\304\336\272\372.txt
    ├── \325\246\342\336\245\327\336\357\346.txt
    └── \325\361\272\336\245\327\265\327\371.txt
% tree -N .
.
└── ޥ
    ├── .txt
    ├── զ.txt
    └── ޥ׵.txt

Apparently the "local" filenames are not getting corrupted (given the output) but if you look at the central index the names are all screwed up:

% unzip -Z ../辞典.zip
Archive:  ../辞典.zip
Zip file size: 505 bytes, number of entries: 3
-rw----     2.0 fat        0 bl stor 21-Sep-26 16:48 ޥ/.txt
-rw----     2.0 fat        0 bl stor 21-Sep-26 16:48 ޥ/զ.txt
-rw----     2.0 fat        0 bl stor 21-Sep-26 16:48 ޥ/ޥ׵.txt
3 files, 0 bytes uncompressed, 0 bytes compressed:  0.0%

[cyphar]

After looking at the spec and the ZIP archives both Info-ZIP and MEGA generate, it seems unclear to me why unzip is confused. Bit 11 is set on both the central directory and local file metadata, which means that Info-ZIP should be interpreting the pathnames as UTF-8.

However I suspect it's getting confused because the MEGA zip file also includes the Unicode Path Extra Field (0x7075) extension (which is suggested against by the spec -- the spec says you should only use one of the two mechanims for UTF-8 paths) but contrary to the spec only sets it in the local metadata and not the global directory (resulting in Info-ZIP detecting it as a conflict). The solution would appear to be fairly simple -- either don't include the 0x7075 extension at all or include it in the global directory as well.

[cyphar]

This logic was added by 201b50e, seemingly because bit 11 isn't supported on Windows? In any case, the extra data should be added to the central directory as well.

[sakethv-mega]

Hello, thank you for the report. This has been escalated to our development team for further investigation and resolution.

Thank you.