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Date: Tue, 30 May 2017 22:52:45 +0100
From: Alan Cox <gnomes@...rguk.ukuu.org.uk>
To: "Serge E. Hallyn" <serge@...lyn.com>
Cc: Peter Dolding <oiaohm@...il.com>, Kees Cook <keescook@...omium.org>,
Daniel Micay <danielmicay@...il.com>, Matt Brown <matt@...tt.com>,
Greg KH
<gregkh@...uxfoundation.org>, Jiri Slaby <jslaby@...e.com>,
Andrew Morton
<akpm@...ux-foundation.org>,
Jann Horn <jannh@...gle.com>, James Morris
<jmorris@...ei.org>,
"kernel-hardening@...ts.openwall.com"
<kernel-hardening@...ts.openwall.com>,
linux-security-module
<linux-security-module@...r.kernel.org>,
linux-kernel
<linux-kernel@...r.kernel.org>
Subject: Re: Re: [PATCH v6 0/2] security: tty: make
TIOCSTI ioctl require CAP_SYS_ADMIN
> > So tty stuff should under a tty capabilities.
>
> (last reply on this)
>
> Currently capabilities.7 says
>
> * employ the TIOCSTI ioctl(2) to insert characters into the input queue of a
> terminal other than the caller's controlling terminal;
>
> for CAP_SYS_ADMIN.
>
> So you can create a new CAP_SYS_TIOCSSTI if you like, and offer a patch where
> *both* CAP_SYS_ADMIN and CAP_SYS_ADMIN suffice. Again, see CAP_SYSLOG for a
> prior example.
Even then it wouldn't be useful because the attacker can use every other
interface in the tty layer, many of which you can't magic away behind a
capability bit. And the applications would need changing to use the
feature - at which point any theoretical broken apps can instead be fixed
to use a pty/tty pair and actually fix the real problem.
Alan
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