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How to run CEWE photo creator on Debian

November 5, 2018

Hi

This post describes how I debug an issue with a proprietary software. I hope this will give you some hint on how to proceed should you face a similar issue. If you’re in a hurry, you can read the TL;DR; version at the end.

After the summer vacations, I’ve decided to offer a photo-book to my mother. I searched for open-source solution but the printed results were lackluster.

Unfortunately, the only possible solution was to use professional service. Some of these services offer a web application to create photo books, but this is painful to use on a slow DSL line. Other services provide a program named CEWE. This proprietary program can be downloaded for Windows, Mac and, lo and behold: Linux !

The download goes quite fast as the downloaded program is a Perl script that does the actual download. I would have preferred a proper Debian package, but at least Linux amd64 is supported.

Once installed, CEWE program is available as an executable and a bunch of shared libraries.

This program works quite well to create a photo album. I won’t go into the details there.

I ran into trouble when trying to connect the application to the service site to order the photo-book: the connection fails with a cryptic message “error code 10000”.

Commercial support was not much help as they insisted that I check my proxy settings. I downloaded again CEWE from another photo service. The new CEWE installation gave me the same error. This showed that the issue was on my side and not on the server’s side.

Given that the error occurred quite fast when trying to connect, I guessed that the connection setup was going south. Since the URL shown in the installation script began with https, I had to check for SSL issues.

I checked certificate issues: curl had no problem connecting to the server mentioned in the Perl script. Wireshark showed that the connection to the server was reset by the server quite fast. I wondered which version of SSL was used by CEWE and ran ldd. To my surprise, I found that ldd did not list libssl. Something weird was going on: SSL was required but CEWE was not linked to libssl…

I used another trick: explore all the menus of the application. This was a good move as I found a checkbox to enable debug report in CEWE in “Options -> paramètres -> Service” menu (that may be “options-> parameters -> support” in English CEWE). When set, debug traces are also shown on standard output of CEWE,

And, somewhere in the debug traces, I found:

W (2018-10-30T18:36:37.143) [ 0] ==> QSslSocket: cannot resolve SSLv3_client_method <==

So CEWE was looking for SSL symbols even though ldd did not require libssl…

I guessed that CEWE was using dlopen to open the ssl library. But which file was opened by dlopen ?

Most likely, the guys who wrote the call to dlopen did not want to handle file names with so version (i.e. like libssl.so.1.0.2), and added code to open directly libssl.so. This file is provided by libssl-dev package, which was already installed on my system.

But wait, CEWE was probably written for Debian stable with an older libssl. I tried libssl1.0-dev.. which conflicts with libssl-dev. Oh well, I can live with that for a while…

And that was it ! With libssl1.0-dev installed, CEWE was able to connect to the photo service web site without problems.

So here’s the TL;DR; version. To run CEWE on Debian, run:

sudo apt install libssl1.0-dev

Last but not least, here are some suggestions for CEWE:

  • use libssl1.1. as libssl1.0 is deprecated and will be removed from Debian
  • place the debug checkbox in “System” widget. This widget was the first I opened when I began troubleshooting. “Service” does not mean much to me. Having this checkbox in both “Service” and “System” widgets would not harm

All the best

[ Edit: I first blamed CEWE for loading libssl in a non-standard way. libssl is actually loaded by QtNetwork. Depending on the way Qt is built, SSL is either disabled (-no-openssl option), loaded by dlopen (default) or loaded with dynamic linking (-openssl-linked). The way Qt is built is CEWE choice. Thanks Uli Schlachter for the heads-up]

 

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From → computer, Debian

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