sudo shouldn't preserve caller's HOME environment variable by default

[Ｖ字龍(Vdragon)]

Currently Ubuntu hard-coded sudo to preserve HOME environment variable to point to sudo caller's home directory by default(refer bug #760140) however this is dangerous and error-prone because the program run by root may create files (e.g. $HOME/.Xauthority , program config files) into caller's HOME directory **AS ROOT** which, will cause issue when users run the same program as their normal users' account again and even make the user failed to login(due to .Xauthority file owner is incorrect)

In my opinion the Ubuntu patch(keep_home_by_default.patch)(no, Debian is NOT affected by this issue) that makes $HOME variable keep in sudo is INSANE and should be reverted(Ubuntu should use the safest configuration to general users by default), any user wish to run command as root using their HOME directory should set env_keep in /etc/sudoers themselves and acknowledging the consequences.

[RootSudo - Community Help Wiki](https://help.ubuntu.com/community/RootSudo) wrongly tells that graphical application shouldn't be launched by sudo, but in fact the real issue falls into this bug.

ProblemType: Bug
DistroRelease: Ubuntu 14.04
Package: sudo 1.8.9p5-1ubuntu1
ProcVersionSignature: Ubuntu 3.16.0-17.23-lowlatency 3.16.3
Uname: Linux 3.16.0-17-lowlatency i686
ApportVersion: 2.14.1-0ubuntu3.4
Architecture: i386
CurrentDesktop: KDE
Date: Thu Sep 25 00:08:44 2014
InstallationDate: Installed on 2013-03-08 (564 days ago)
InstallationMedia: Ubuntu 12.10 "Quantal Quetzal" - Release i386 (20121017.2)
SourcePackage: sudo
UpgradeStatus: Upgraded to trusty on 2014-04-19 (158 days ago)
VisudoCheck:
 /etc/sudoers: parsed OK
 /etc/sudoers.d/Preserve_input_method_required_environmental_variables: parsed OK
 /etc/sudoers.d/README: parsed OK
modified.conffile..etc.sudoers.d.README: [modified]
mtime.conffile..etc.sudoers.d.README: 2014-09-24T22:26:35.734703

[Launchpad Janitor (janitor)]

Status changed to 'Confirmed' because the bug affects multiple users.

[erio (eri0)]

Is this the keep_home_by_default first submission?

http://bazaar.launchpad.net/~vorlon/ubuntu/natty/sudo/keep_home_by_default/files

The file env.c has the table initial_keepenv_table that lists HOME and it is used in init_envtables . What could break from correcting this?

[Seth Arnold (seth-arnold)]

If HOME is removed, then e.g. vim, bash, etc., will use /root/.vimrc, /root/.bashrc, etc rather than the user's ~/.vimrc, ~/.bashrc, etc. While it's a bad idea to run X clients via sudo, they too would likely look in the wrong locations for configuration files, and there's a chance that X11 clients may not even be able to connect to the X11 server if they are aimed at the wrong .Xauthority file.

Thanks

[林博仁(Buo-ren Lin) (brlin)]

@seth-arnold
Sorry for the very~ late reply, my aplogies.

> If HOME is removed, then e.g. vim, bash, etc., will use /root/.vimrc, /root/.bashrc,
> etc rather than the user's ~/.vimrc, ~/.bashrc, etc.
You shouldn't expect finding your config files when using other user's account(including root).
If you need the same configuration simply create a symbolic link then.

> there's a chance that X11 clients may not even be able to connect to the X11
> server if they are aimed at the wrong .Xauthority file.
In fact X11 clients doesn't require SUDO_USER's .Xauthority file to run, all you have to to is to run `xhost +SI:localuser:root` to allow X server be accessed by root user then you can run `sudo whatever-x11-application` without setting SUDO_USER's HOME directory (unless the application itself does not allow running as root, such as recent release of Kate and Dolphin).

In summary,

1. Setting SUDO_USER's home directory as HOME of root is not the proper method to "let my stuff in my home directory to be accessed by root" and will cause numerous disasters(such as https://www.ptt.cc/bbs/Linux/M.1498509926.A.AC9.html which forces me to review this bug)
2. "Running X11 applications as root" isn't a reason to keep this patch as well, as it can **still** runnable as root without setting SUDO_USER's home directory.

[Dan Streetman (ddstreet)]

I marked this as a dup of bug 1556302, as there seems to be more recent movement in that bug, and both bugs want the same thing - to revert the Ubuntu-only patch 'keep_home_by_default.patch'.