Fri, 10 Apr 2026 09:35:42 +0000 https://bugs.horde.org/ticket/4670 unable to open zip files on Mac OS X The "Download all attachments in zip file" option sometimes results in a file that cannot be opened by the default zip handler (BOMArchiveHelper) on Mac OS X. Zipinfo reports the contents of the file properly. The file can be "repaired" using the following steps: zipnote file.zip >tmp zipnote -w file.zip <tmp In doing this we noted that 12 bytes per file get dropped from the archive. The mailing list reports two other zip handlers having problems with IMP generated zip files: 7-Zip and Stuffit 11. In Horde/Compress/zip.php I found at line 346: /* "Data descriptor" segment (optional but necessary if archive is not served as file). */ $fr .= pack('V', $crc); $fr .= pack('V', $c_len); $fr .= pack('V', $unc_len); This amounts to 12 bytes that gets added for each file in the archive. These are the 12 bytes that zipnote is stripping out for each file. PKWare's appnote.txt indicates there is confusion in the use of the data descriptor segment (should it have a signature, should it only be used in stream processing, which bit to set if it will be used) and promises a future appnote to resolve the confusion. Since we did not want to touch every Macintosh on campus to set it to use a different default zip handler we went ahead and commented out the data descriptor segment. Thu, 16 Nov 2006 11:53:47 +0000 https://bugs.horde.org/ticket/4670#t26199 Fixed in HEAD and FW_3 - thanks for the analysis and fix! Thu, 16 Nov 2006 19:51:08 +0000 https://bugs.horde.org/ticket/4670#t26244