X programs don't run from job definitions with user: root

[Daniel Manrique]

A job that has user: root and whose command invokes an X application will fail to run the application. This uses the trusted launcher whose policy regarding GUI applications is correctly set in the policy file.

For instance, mediacard/sd-performance-manual uses zenity to display results, but since it uses user:root it fails to display this to the user.

This has been confirmed in both Trusty and Precise.

I created a bogus job that just prints the environment and tries to run gedit as an example, to rule out a problem with zenity. With user: root it doesn't launch gedit and I see this in the test result:

PATH=/tmp/nest-mqsliy4c.722881a52a9cfb4a81721cbd5daab751db5659894c86162c88d8ad771ca8f815:/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin:/usr/games:/usr/local/games
PWD=/root
LANG=C.UTF-8
SHLVL=1
CHECKBOX_SHARE=/usr/lib/plainbox-providers-1/checkbox/
CHECKBOX_DATA=/home/roadmr/.cache/plainbox/sessions/pbox-z5r75cgg.session/CHECKBOX_DATA
_=/usr/bin/env
error: XDG_RUNTIME_DIR not set in the environment.

(gedit:30425): Gtk-WARNING **: cannot open display:

If I remove user: root to bypass the trusted launcher, gedit runs and I see this:

XDG_VTNR=7
SSH_AGENT_PID=1294
XDG_SESSION_ID=c1
CLUTTER_IM_MODULE=xim
SELINUX_INIT=YES
DBUS_STARTER_ADDRESS=unix:abstract=/tmp/dbus-EKG5JibWpS,guid=3ed2bbf7025a5632648f9c5a5314f52b
XDG_GREETER_DATA_DIR=/var/lib/lightdm-data/roadmr
GPG_AGENT_INFO=/run/user/1000/keyring-qjr6Mf/gpg:0:1
SHELL=/bin/bash
XDG_MENU_PREFIX=gnome-
UPSTART_SESSION=unix:abstract=/com/ubuntu/upstart-session/1000/1223
GNOME_KEYRING_CONTROL=/run/user/1000/keyring-qjr6Mf
GTK_MODULES=overlay-scrollbar:unity-gtk-module
USER=roadmr
XDG_SESSION_PATH=/org/freedesktop/DisplayManager/Session0
XDG_SEAT_PATH=/org/freedesktop/DisplayManager/Seat0
SSH_AUTH_SOCK=/run/user/1000/keyring-qjr6Mf/ssh
ZEITGEIST_DATA_PATH=/home/roadmr/.local/share/zeitgeist
DEFAULTS_PATH=/usr/share/gconf/ubuntu.default.path
SESSION_MANAGER=local/roadmr-Latitude-3440:@/tmp/.ICE-unix/1497,unix/roadmr-Latitude-3440:/tmp/.ICE-unix/1497
XDG_CONFIG_DIRS=/etc/xdg/xdg-ubuntu:/usr/share/upstart/xdg:/etc/xdg
PATH=/tmp/nest-i6rizz3y.546647aa43f3d13ad63be4b77cad89ed4ed863f3855e0ba07bdb6e58ac245cc2:/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin:/usr/games:/usr/local/games
DESKTOP_SESSION=ubuntu
JOB=xsession-init
PWD=/
XMODIFIERS=@im=ibus
LANG=C.UTF-8
GDM_LANG=en_US
MANDATORY_PATH=/usr/share/gconf/ubuntu.mandatory.path
UBUNTU_MENUPROXY=1
COMPIZ_CONFIG_PROFILE=ubuntu
IM_CONFIG_PHASE=1
GDMSESSION=ubuntu
DBUS_STARTER_BUS_TYPE=session
SESSIONTYPE=gnome-session
SHLVL=1
HOME=/home/roadmr
XDG_SEAT=seat0
GNOME_DESKTOP_SESSION_ID=this-is-deprecated
UPSTART_INSTANCE=
UPSTART_EVENTS=starting
LOGNAME=roadmr
DBUS_SESSION_BUS_ADDRESS=unix:abstract=/tmp/dbus-EKG5JibWpS,guid=3ed2bbf7025a5632648f9c5a5314f52b
QT4_IM_MODULE=xim
XDG_DATA_DIRS=/usr/share/ubuntu:/usr/share/gnome:/usr/local/share/:/usr/share/
TEXTDOMAIN=im-config
UPSTART_JOB=dbus
INSTANCE=
XDG_RUNTIME_DIR=/run/user/1000
DBUS_DEBUG_OUTPUT=1
DISPLAY=:0
CHECKBOX_SHARE=/usr/lib/plainbox-providers-1/checkbox/
XDG_CURRENT_DESKTOP=Unity
GTK_IM_MODULE=ibus
CHECKBOX_DATA=/home/roadmr/.cache/plainbox/sessions/pbox-9i28hr8e.session/CHECKBOX_DATA
TEXTDOMAINDIR=/usr/share/locale/
XAUTHORITY=/home/roadmr/.Xauthority
_=/usr/bin/env
Fontconfig warning: ignoring C.UTF-8: not a valid language tag

[Zygmunt Krynicki (zyga)]

Thanks for the details bug report. I'll see if I can fix this. The odd thing is that we pass all the client side environment to plainbox-trusted-launcher but apparently (somehow) it is not being respected. Are you sure this job got started with plainbox-trusted-launcher and not sudo?

[Daniel Manrique (roadmr)]

An easy way to reproduce it is to install plainbox (apt-get install plainbox is what I did), then:

plainbox run -i .*sd-performance.*

that'll show a policykit prompt, and then show the failed output from the job run. I know it's not using sudo because I never saw a sudo prompt and this system always requires sudo passwords so it would have asked me.

[Daniel Manrique (roadmr)]

OK, I ran plainbox with -C --trace=plainbox.runner, and I see it's selecting the RootViaPTL1ExecutionController with a score of "3" for the given job. I've never heard of PTL1 :) I thought it'd be RootViaPkexec.

Anyway, this is possibly another clue, I'll look at what PTL1 does and why it's outbidding Pkexec, and maybe we need to tweak the bid scores; or if this PTL1 controller is not behaving as it should, it could need fixing.

[Daniel Manrique (roadmr)]

DOH, PTL1 is the plainbox trusted launcher... disregard me.

[Daniel Manrique (roadmr)]

using --trace plainbox.ctrl I see this:

DEBUG plainbox.ctrl: job[mediacard/sd-performance-manual] executing ['pkexec', '--user', 'root', 'plainbox-trusted-launcher-1', '--target', '722881a52a9cfb4a81721cbd5daab751db5659894c86162c88d8ad771ca8f815', '-T', 'CHECKBOX_DATA=/home/roadmr/.cache/plainbox/sessions/pbox-hn652bgr.session/CHECKBOX_DATA', '-T', 'CHECKBOX_SHARE=/usr/lib/plainbox-providers-1/checkbox/', '-T', 'LANG=C.UTF-8', '-T', 'PATH=/tmp/nest-n9x7b28j.722881a52a9cfb4a81721cbd5daab751db5659894c86162c88d8ad771ca8f815:/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin:/usr/games:/usr/local/games'] with env None

The final "env None" looks suspicious. I'll continue trying to dig into this.

[Sylvain Pineau (sylvain-pineau)]

The trusted launcher does not keep the original env set by pkexec, so all the variables kept by setting the allow_gui in the action file definition were lost. I proposed a fix that update the existing env set by pkexec by the one provided by plainbox.