[imp] "Download All Attachments" for SMIME signed mails creates corrupted zip

[André Lang]

Hello list !

Horde Groupware Webmail Edition 1.2.2
Horde: 3.3.3
IMP: 4.3.3

Reproducible behavior (tested on two different hosts):
- send an S/MIME signed mail containing one or more attachments to a
Horde recipient
- open the mail in IMP
- choose "Download all attachments as zip file"

Result:
- zip file gets downloaded, but is very small (100-300 Bytes)
- zip file can be opened and is not completely corrupt, but contains
only the zip file index header - the real file data is missing. A hex
editor shows an intact "PK" file identification at the beginning as well
as the file names of the attachments.

Note:
- Separate download of each of the attachments works
- enabling/disabling S/MIME in conf.php and the user settings makes no
difference
- openssl is properly installed within PHP

Is there anything I can do about it or should I file a bug ticket ?

André