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I am a root user, and suppose I want to run any application as another user. Is this possible, without switching to another user?

Something like

# google-chrome user=abc

I am actually executing a CLI program as a non-root user. I have set the sticky bit on and I am using setuid, so the program runs with root privileges. Now I am using system() within the program to invoke a GUI app. But I don't want to run it as root, so I want to temporarily drop root privileges only for that call.

Glorfindel
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adnan kamili
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4 Answers4

10

Short answer: "Yes, this is possible".

if you like to execute a non-X application then just use the following command:

sudo -u abc command

If you like to run some X application as another user but with your own desktop first you need to create a helper script, that will make your life simpler

  • create a bin folder under your home directory:

mkdir -p ~/bin

and using your favorite text editor create a file ~/bin/xsudo as follows:

#!/bin/bash
# (C) serge 2012
# The script is licensed to all users of StackExchange family free of charge
# Fixes/Enhancements to the script are greatly appreciated. 
# 
# SUDO_ASKPASS has to be set to the path of ssh-askpass
# fix the following two lines if your distribution does not match this autodetection
. /etc/profile.d/gnome-ssh-askpass.sh
export SUDO_ASKPASS="${SSH_ASKPASS}"

SUDOUSERNAME="$1"
shift
xauth nlist "${DISPLAY}"|sudo -HA -u $SUDOUSERNAME env --unset=XAUTHORITY \
bash -c "xauth nmerge - ; $*"

then make it executable:

chmod +x ~/bin/xsudo

and use it the same way as sudo but without any switches:

xsudo user application

Enjoy.

P.S. Starting xsession from the root account is strongly discouraged!

Serge
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  • Did you try it ? I'm afraid this particular example can't work. – jlliagre Sep 29 '12 at 10:56
  • Yes, because in order to start an X application from another user session you have to allow access to you display. But this is also possible. Unfortunately I do not remember how exactly this to be done. – Serge Sep 29 '12 at 11:03
  • @jlliagre However, I remember how to start an X app on the same host in a tricky way: `ssh -X abc@localhost google-chrome` :) – Serge Sep 29 '12 at 11:07
  • Hmm... I'm writing in comments what you already posted 22 mins ago... – Serge Sep 29 '12 at 11:15
  • But you still have 6 up votes for a non working solution while I only got one for a correct one. StackExchange model is sometimes quite frustrating ... – jlliagre Sep 29 '12 at 13:24
  • @jlliagre 1) it is working solution as the question is clear: "Is it possible for root to execute a command as non-root"; and then: "Say..." 2) I do not look at votes at all: very often I see that for absolutely equivalent answer people voting in favor of the one who has higher reputation regardless of the fact that the first answer was given by the other person with score of 1. – Serge Sep 29 '12 at 15:14
  • `DISPLAY=:0 sudo -u abc google-chrome` ? (Assuming same machine, at least) – Izkata Sep 29 '12 at 18:18
  • @lzkata DISPLAY=:0.0 is already set in my case (am starting the sudo form Xterminal window). I need to solve XAuth problem to provide complete answer, but now have no time to refresh my mind, thanks any way) – Serge Sep 29 '12 at 18:52
  • @jlliagre Take a look, please – Serge Sep 30 '12 at 11:30
9

A portable solution would be:

su abc -c google-chrome

However, as google-chrome is requiring X11 access, this will likely fail unless you unsecured it, which would be a very bad idea, especially while running as root.

If X11 tunelling/forwarding is allowed, a better way would be

ssh -X abc@localhost google-chrome

or

ssh -Y abc@localhost google-chrome
jlliagre
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  • Why would the ssh approach be any better? Wouldn't this still run using the root user's X session? – Steve May 13 '18 at 21:04
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    @Steve Using `su abc -c google-chrome` will likely fail in the first place because `abc` cannot use root's session, `.Xauthority` being unreadable for `abc`. – jlliagre May 13 '18 at 21:22
  • Oops sorry I misunderstood you, I thought you meant it would be better from a security perspective – Steve May 13 '18 at 21:24
1
#! /bin/bash
#  (GPL3+) Alberto Salvia Novella (es20490446e)


execute () {
    function="${1}"
    command="${2}"
    error=$(eval "${command}" 2>&1 >"/dev/null")

    if [ ${?} -ne 0 ]; then
        echo "${function}: $error"
        exit 1
    fi
}


executeAsNonAdmin () {
    function="${1}"
    command="${2}"

    eval setPasswordAsker="SUDO_ASKPASS=/usr/libexec/openssh/ssh-askpass"
    run="runuser ${SUDO_USER} --session-command=\"${setPasswordAsker}\" --command=\"${command}\""
    execute "${function}" "${run}"
}


executeAsNonAdmin "" "${@}"
Alberto Salvia Novella
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1

There is a way to run chromium when logged in to the root user. If you open it normally, it will give you an error like "chromium cannot be run as root."

To run it without the error, right click your desktop, create a new launcher with the command: chromium-browser --user-data-dir. You can name it what you want, save it, when you open it, it will give you the chromium browser. (Works in Ubuntu 10.04.4 LTS)

HopelessN00b
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user299161
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