sux "cannot set terminal process group ...." error

[H.-Dirk Schmitt]

After migration from precise to raring I can't use sux in a reliable manner.

1. After invocation I got the error message:
bash: cannot set terminal process group (-1): Inappropriate ioctl for device bash: no job control in this shell

2. Pressing Ctrl+C kills the entire session

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ProblemType: Bug
DistroRelease: Ubuntu 13.04
Package: sux 1.0.1-6
ProcVersionSignature: Ubuntu 3.8.0-31.46-generic 3.8.13.8
Uname: Linux 3.8.0-31-generic x86_64
NonfreeKernelModules: nvidia
ApportVersion: 2.9.2-0ubuntu8.4
Architecture: amd64
Date: Wed Sep 11 15:15:19 2013
MarkForUpload: True
PackageArchitecture: all
SourcePackage: sux
UpgradeStatus: No upgrade log present (probably fresh install)

[H.-Dirk Schmitt (dirk-computer42)]

After web research is seems that the bug is introduced by the schange of the login package from 1:4.1.4.2 (presice/quantal) to 1:4.1.5.1 (raring/saucy)

> shadow (1:4.1.5-1) unstable; urgency=low
>
> * The "Charolais" release.
>
> [ Nicolas FRANCOIS (Nekral) ]
> * New upstream release:
> - su: Fix possible tty hijacking by dropping the controlling terminal when
> executing a command (CVE-2005-4890). Closes: #628843
> ...

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[Launchpad Janitor (janitor)]

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

[infernet (guattari)]

Same here. It occurs on:

sudo su username -

[mancha (mancha1)]

Hello.

This is due to changes introduced in su in shadow 4.1.5 to address CVE-2005-4890. They amount, in sum, to dropping the controlling TTY when su is used non-interactively.

While the threat of command injection does exist, shadow's omni-directional solution is overkill.

As I documented back in May (http://seclists.org/oss-sec/2013/q2/374), crippling "su -c" when escalating privileges (i.e. callee is root) is unwarranted. After all, we're not really worried about root injecting commands to a non-privileged user.

Feel free to use the patch I constructed that addresses the issue being reported when sux (or any other su frontend/wrapper) invokes su non-interactively to escalate privs:

http://sf.net/projects/mancha/files/misc/shadow-4.1.5.1_CVE-2005-4890_relax.diff

--mancha