How to launch a QProcess with root rights?

Question

I need to launch gphoto2 from a Qt program. I do this:

QString gphotoProgram = "/usr/bin/gphoto2";
QStringList gphotoArguments;
gphotoArguments << "--capture-image";
QProcess *gphotoProcess = new QProcess(this);
gphotoProcess->start(gphotoProgram, gphotoArguments);

but it never enters the Running state this way, as gphoto2 usually needs admin rights to be launched on command line.

How can I start this QProcess with proper rights to make gphoto2 working?

Edit: I precise that I would prefer the user to not have to enter a password, which means gksudo, kdesudo or any other graphical solution is not a valid option for me.

Piperpiperaceous

Answer 1

I would strongly recommend finding a way to allow gphoto2 to be run with the logged in user's permissions. Perhaps this article has some helpful info.

Mcburney

This page was helpful indeed, thanks a lot! For the posterity, here is the needed command line to do to enable any user of the group plugdev: /usr/lib/libgphoto2/print-camera-list udev-rules version 0.98 group plugdev mode 0660 > /etc/udev/rules.d/90-libgphoto2.rules – Novelize

Answer 2

If you have a distribution with sudo enabled, try to add "gksudo" to the command line of your process:

QString gphotoProgram = "gksudo /usr/bin/gphoto2"

If the user account is authorized as a sudo-er, it will ask the user password so that the program can run with root rights.

Lepido

I forgot to precise that I would prefer not to use a graphical interface to enter a password, as the user may not know it. I edited the question accordingly. – Novelize

If the security mechanism demands a password (and most often it does), you won't be able to bypass that. – Pifer

If you want to bypass the password authentication, the only way to do it is to set up a background process with root privileges (daemon, server, etc.) wrapping your gphoto2 needs. Your application just have to communicate with the server with a socket. But I think it is a bad idea, as it is an open gate to security problems... Maybe you should try to understand why admin rigths are needed, and if there is some alternatives to that. – Lepido

... as a side note, I think that if gphoto needs admin rights, it is because it is using USB devices directly, and access rights must be set correctly for them. Have a look at the following page: gphoto.org/doc/manual/permissions-usb.html , and see if you can configure things so that no root privilege is needed for USB cameras – Lepido

Answer 3

You can also use PolicyKit to start QProcess with sudo rights.

pkexec command

QString gphotoProgram = "pkexec /usr/bin/gphoto2";

Known

@ChrisV I want to implement this in windows. Help me out. – Known

Answer 4

Don't GNOME and KDE still have their own graphical sudo wrappers? (I'm a Windows guy myself.) You could use QProcess to launch "sudo" and let it take care of the elevation and subsequent gphoto launch.

Sanmiguel

I forgot to precise that I would prefer not to use a graphical interface to enter a password, as the user may not know it. I edited the question accordingly. – Novelize