this post was submitted on 28 May 2024
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22
Elevate privileges between Python program ( and Inter-process_communication ) (self.linux)
submitted 5 months ago by SpongeB0B to c/[email protected]
10 comments fedilink hide all child comments
 

Hi everyone,

I have a Python program (A) that run under a regular user account. (good)

When some events occur in (A) I need to modify my nftables and only the root is allowed to do so.

I've come up with 3 ways to do that (if you know other please share) but I don't which would be the best.

  1. Make a sudo call from (A) with from subprocess import run but I will need to store the password ! and I don't think is possible to keep it encrypted and decrypted when need it (it's a flaw)
    .
  2. Make (A) writing a file with the requests. Create a (B) daemon (that run as root) that check that file every X and do the necessary
    .
  3. Make (A) do an IPC ( Linux socket ) to (B) daemon (that run as root) and does the necessary.

I suppose that the solution 2 is less heavy that the 3 ? But if I'm not mistaken it will react also slower ?

Thanks.

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[–] [email protected] 9 points 5 months ago

If your command doesn't change (doesn't require dynamic input), sudoers file can make specific command+argument run without password required.

https://www.cyberciti.biz/faq/linux-unix-running-sudo-command-without-a-password/ (ctrl+f search "A better solution")

(You can also use wildcards in sudoers file but with nftables I imagine it's a big security risk)

[–] [email protected] 4 points 5 months ago* (last edited 5 months ago) (1 children)
  1. Is the usual solution, but instead of file use unix socket and user/group permissions as auth - the running user has to be part of some group so that the control client (A) can access the control socket of (B) daemon.

Alternatively you could use capabilities:

https://stackoverflow.com/a/414258

https://man7.org/linux/man-pages/man7/capabilities.7.html

[–] SpongeB0B 2 points 5 months ago (1 children)

Thank you very much @taaz

So you say 2 but with unix socket so it the same as my proposal number 3 ? no ?

I'll check capabilities

[–] [email protected] 2 points 5 months ago

Yeah kinda, unix socket does count as ipc

[–] [email protected] 1 points 5 months ago (1 children)

You could try pkexec insted of sudo. Pkexec pops up the password prompt in a window insted of prompting in the terminal.

[–] [email protected] 3 points 5 months ago (1 children)

It's a good way of solving it. It's not scriptable though as it requires user-input.

[–] SpongeB0B 3 points 5 months ago (1 children)

indeed I need it to be scriptable.

[–] [email protected] 1 points 5 months ago

Then implement polkit perhaps? https://polkit.pages.freedesktop.org/polkit/polkit-apps.html

Basically the root using bit is handled via polkit. Three unprivileged bit calls the privileged bit via polkit.

[–] [email protected] 1 points 5 months ago* (last edited 5 months ago)

Method 2 could use inotify to wake up when the file changes. It wouldn't have to poll. Method 3 could launch from inetd so it wouldn't have to always be running if these events are infrequent.

[–] [email protected] 0 points 5 months ago

Have you looked into the suid bit? You can set it on the file, then change the script owner to root and it runs in elevated mode: https://linuxhandbook.com/suid-sgid-sticky-bit/