PCLZIP_ERR_BAD_FORMAT (-10) : Invalid archive structure during plugin update

[LongTail Video]

Currently, as part of our JW Player plugin we include several player skins so that users can customize the look of the JW Player. These skins are packaged as zip archives.

For a while now we've been getting reports from our users having difficulty performing the automated update/install. These users are receiving a PCLZIP error which claims the plugin archive is invalid.

From looking at the source code I see that WordPress first attempts to use the ZipArchive PHP module to unzip plugin packages. This always works for users updating our plugin. If this is not available it then uses a fallback library called PCLZIP. After some experimentation, it seems that PCLZIP has difficulty unzipping archives that contain archives.

Is this a known issue from your experience? If so, is there a workaround other than removing the zip skins from our plugin package?

Nesting archives typically isn't a good idea.

Thanks for reporting the issue. Can you confirm that this is reproduce-able every time when PCLZIP extracts a zip-file containing another zip?

Technically there should be no difference which type of files reside inside a zip. I don't know why this should be a bad idea to have a zip in a zip technically. I never had problems with that on desktop or shell, so if this actually happens every time with PCLZIP (and not the PHP ZIP extenstion), this is most likely a flaw with PCLZIP (as this is a PCLZIP error constant). I couldn't find any information if zip in zip is problematic on the PCLZIP homepage.

If this is reproduceable, it's probably worth to check if WP still has the latest PCLZIP version bundled and to report this problem as well to the PCLZIP project.

Thanks for the response. I have no problem actually reproducing this issue. I looked into the PCLZIP version and from what I can tell WordPress is using the latest version.

I'll look into reporting the issue to the PCLZIP project.

Just Triag'ing the ticket, Setting Priority to low, only due to the complexity of PclZip and the limited impact (A small percentage of plugins will use zip's in their zip's)

Can duplicate this issue with this file: http://downloads.wordpress.org/plugin/jw-player-plugin-for-wordpress.1.3.3.zip however, I cant duplicate it with a simple archive within an archive however, so it might be dependant on archive in a subfolder, or a particular compression application used by WordPress.org or maybe the size of the archives.

Looking at the strings within PclZip, it appears as if it thinks some files finish half way through, which causes a problem(Invalid archive structure) when it can't find the next file header mid-way through the compressed file data.. Unfortnately, I'm not good enough to follow some of the cryptics within PclZip, but it looks like privReadEndCentralDir() might be returning the incorrect offsets (Note, This is the function we had to patch for 64bit systems when initially introduced)