Running application with user privillegions.

JonB

@nicholas_ru
There are 3 ways I know of under Linux:

Invoke su or sudo or runuser or setpriv or others to run your program. Depending on your flavor you may be able to pass a password on the command line, standard input, environment variable or similar.
Use polkit and pkexec to configure the system to run certain programs with certain privileges. It does not require a login or password once set up.
Make your executable file setuid to root or another user so it always runs with that user's privileges. It does not require a login or password.

QProcess is nothing but a wrapper around Linux exec-type system calls. Nothing special about it. It could be used to run any of the above.

nicholas_ru

please, describe code for this action, i am beginner.

JonB

@nicholas_ru
You need to investigate these alternatives to decide which suits your use case the best. You can use man pages or Google. They don't really require "programming" at your side. You should start with: what is it you are trying to do which requires running as another user and why? Why do you want to run what as root from where? Will you only be running this yourself, within your own organization or for distribution to others in the outside world? And btw is this to be a command line or UI Qt application?

Joe von Habsburg

I used to before on js many years ago, maybe that command help you

// echo your-password | sudo -S your-command

QString command = QString("echo %1 | sudo -S %2").arg(1234).arg("ifconfig")
rocess->start(command)

nicholas_ru

Debian running, for example, /usr/sbin/gparted, automatically with root requesting(without entering command sudo).How implementation this is, i am don't know.

Joe von Habsburg

@nicholas_ru said in Running application with user privillegions.:

Debian running, for example, gparted, automatically with root requesting(without entering command sudo).How implementation this is, i am don't know.

I don't understand what you mean. Are you saying that the gparted command runs as root but doesn't ask for a password, whereas other applications do?

For example, you may have entered a password for the sudo command in the same terminal before, or you may have granted permissions for the gparted command. These are Linux-related tasks.

If you need run command on qproccess with sudo and password: https://superuser.com/questions/67765/sudo-with-password-in-one-command-line

jsulm

@nicholas_ru said in Running application with user privillegions.:

How implementation this is, i am don't know.

This was answered by @JonB :
"Make your executable file setuid to root or another user so it always runs with that user's privileges. It does not require a login or password."

Peter Watson

@fnaf free Could you please provide an example or some sample code for this? I’m still a beginner and trying to understand how it works.

Joe von Habsburg

You could ask ai or search on google

sudo cp your_program.exe /usr/local/bin/your_program
sudo chmod +x /usr/local/bin/your_program

These are Linux-related tasks.

JonB

@Joe-von-Habsburg said in Running application with user privillegions.:

sudo chmod +x /usr/local/bin/your_program

It's already executable after the copy, and chmod +x does nothing more than it already is. It does not make the executable run as root. You want/intended instead:

chmod u+s path-to-executable

so it will look like:

root@ubuntu-22:~/QtTests/C++/sudopassword/build/Desktop-Debug# chmod u+s fred
root@ubuntu-22:~/QtTests/C++/sudopassword/build/Desktop-Debug# ls -l fred
-rwsr-xr-x 1 root root 379112 Mar 30 08:48 fred

Note the -rws, the s there.

Note that you will need to repeat the chmod every time after you recompile/recopy your executable. If you redistribute your executable then wherever it gets installed the root user would need to choose to run the chmod u+s there once, you cannot distribute (I don't think) with the executable owned by root and setuid.

nicholas_ru

You have ubuntu. I have Debian. This is method change chmod, not exit for programmers.First post with running command very nice,but not full.

JonB

@nicholas_ru
Did you even try it?? Debian man page https://manpages.debian.org/bookworm/coreutils/chmod.1.en.html

Each MODE is of the form '[ugoa]*([-+=]([rwxXst]*|[ugo]))+|[-+=][0-7]+'.

How else would you setuid under Debian? No point my suggesting things if they do work but you say they do not.

.First post with running command very nice,but not full.

If you mean @Joe-von-Habsburg 's QString command = QString("echo %1 | sudo -S %2").arg(1234).arg("ifconfig") it won't work as written if passed to QProcess::start().... But I am getting a bit dispirited trying to help you so up to you.

Joe von Habsburg

@JonB said in Running application with user privillegions.:

But I am getting a bit dispirited trying to help you so up to you.

:(

@nicholas_ru said in Running application with user privillegions.:

You have ubuntu. I have Debian. This is method change chmod, not exit for programmers.First post with running command very nice,but not full.

so ? linux is linux and there is a qt forum. we try to help you

JonB

@Joe-von-Habsburg said in Running application with user privillegions.:

But I am getting a bit dispirited trying to help you so up to you.

:(

To be clear: it is the OP I am getting "dispirited" trying to help, not your posts! :)

He could use your code approach (perhaps, if that is what he wants), just that it needs changing to work. But since we (at least I) don't even know exactly what he wants I have not corrected it so far, waiting to see.....

nicholas_ru

@JonB i am think in Qt framework must be integrated this is function.

JonB

@nicholas_ru No idea what you mean. You have plenty of answers & suggestions above, so over to you to do something....

nicholas_ru

@JonB if QProcess running with root true, if without false.

JonB

@nicholas_ru
Again, I don't know what that phrase means. You might trying typing in your questions/answers with full detail in your native language into Google and asking it to translate to English, that may give a more meaningful question.

We have explained what the possibilities are for running programs under Linux setuid/as root. You have to pick one. You have to try the suggestions you have been given. I don't even believe what you said about chmod u+s not being available under your Debian. Qt as a framework has nothing to say or do about setuid. QProcess can be used to run other programs in the standard Linux exec-type way. Just because you say "i am think in Qt framework must be integrated this is function." does not make it so there is magically something else in Qt we have not discussed.

At this point I don't think anybody here knows what you actually want, what your problem is or what you have tried from the suggestions.

SimonSchroeder

There is a reason why you can't just run anything with root privileges. And under normal circumstance you should not try to circumvent it. The most important question is if you really need to run something as root (while your own software is not started with root privileges). Qt does not provide anything special to run a process as root. You need to use OS functionality to run an elevated process (you can use QProcess to start sudo or use any of the other methods mentioned before). In the case of sudo it is up to you to ask the user for the password and hand it to sudo. But, even this is a bad idea because it is really easy to leak the password for an attacker.