Created attachment 87897 [details]
Slides from LibreOffice2013 presentation
LibreOffice is in the process of assembling slides from our last conference and one of our presenters gave us a PDF export [see attachment] of PowerPoint slides which opens in Adobe Acrobat on Windows without a password, but gives a "Password required" prompt on Evince 3.4.0 on Ubuntu 12.04.3.
Testing with pdf2ps 9.05, gives the following error:
" **** This file uses an unknown standard security handler revision: 6"
...which looks like this bug:
(I stole the title from bug 3498, but I believe this is a separate issue :-)
FWIW Adobe Acrobat on Linux doesn't open the file here either.
GhostScript also is unable to open it, but mupdf can do so.
The mupdf src has this comment about /R 6:
* Compute an encryption key (PDF 1.7 ExtensionLevel 8 algorithm)
* Adobe has not yet released the details, so the algorithm reference is:
That will be needed to handle this document.
Created attachment 88038 [details]
Slides from LibreOffice2013 presentation - cleaned with MuPDF
(In reply to comment #2)
> GhostScript also is unable to open it, but mupdf can do so.
Excellent. Looks like we can mupdf to convert the PDF files.
Build MuPDF from source (3379bea "Remove duplicated line.") and use mutool to massage a (seemingly) encrypted PDF into something more standard.
qubit@loopbackoffice:~/src/mupdf/build/debug/mutool clean LibO\ Conf\ 2013\ as\ presented.pdf LibO-Conf-2013_cleaned-with-mupdf.pdf
Evince can open the output PDF properly.
This is no longer reproducible since support has been added to poppler a while ago. This is also documented in the referenced LibreOffice bug report.