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From: Alan Cox <gnomes@lxorguk.ukuu.org.uk>
To: "Serge E. Hallyn" <serge@hallyn.com>
Cc: Peter Dolding <oiaohm@gmail.com>,
	Kees Cook <keescook@chromium.org>,
	Daniel Micay <danielmicay@gmail.com>, Matt Brown <matt@nmatt.com>,
	Greg KH <gregkh@linuxfoundation.org>,
	Jiri Slaby <jslaby@suse.com>,
	Andrew Morton <akpm@linux-foundation.org>,
	Jann Horn <jannh@google.com>, James Morris <jmorris@namei.org>,
	"kernel-hardening@lists.openwall.com"
	<kernel-hardening@lists.openwall.com>,
	linux-security-module <linux-security-module@vger.kernel.org>,
	linux-kernel <linux-kernel@vger.kernel.org>
Subject: Re: [kernel-hardening] Re: [PATCH v6 0/2] security: tty: make TIOCSTI ioctl require CAP_SYS_ADMIN
Date: Tue, 30 May 2017 22:52:45 +0100	[thread overview]
Message-ID: <20170530225245.092497be@alans-desktop> (raw)
In-Reply-To: <20170530155235.GA11861@mail.hallyn.com>

> > 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

  reply	other threads:[~2017-05-30 21:52 UTC|newest]

Thread overview: 32+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2017-05-05 23:20 [kernel-hardening] [PATCH v6 0/2] security: tty: make TIOCSTI ioctl require CAP_SYS_ADMIN Matt Brown
2017-05-05 23:20 ` [kernel-hardening] [PATCH v6 1/2] security: tty: Add owner user namespace to tty_struct Matt Brown
2017-05-05 23:20 ` [kernel-hardening] [PATCH v6 2/2] security: tty: make TIOCSTI ioctl require CAP_SYS_ADMIN Matt Brown
2017-05-18 13:31   ` [kernel-hardening] " Greg KH
2017-05-19  4:51     ` Matt Brown
2017-05-10 20:29 ` [kernel-hardening] Re: [PATCH v6 0/2] " Alan Cox
2017-05-10 21:02   ` Daniel Micay
2017-05-13 19:52   ` Matt Brown
2017-05-15  4:45     ` Nicolas Belouin
2017-05-15 20:57     ` Alan Cox
2017-05-15 23:10       ` Peter Dolding
2017-05-16  4:15         ` Matt Brown
2017-05-16  9:01           ` Peter Dolding
2017-05-16 12:22             ` Matt Brown
2017-05-16 14:28               ` Kees Cook
2017-05-16 15:48                 ` Serge E. Hallyn
2017-05-16 22:05                   ` Peter Dolding
2017-05-16 21:43                 ` Peter Dolding
2017-05-16 21:54                   ` Matt Brown
2017-05-17 16:41                 ` Alan Cox
2017-05-17 18:25                   ` Daniel Micay
2017-05-17 23:04                     ` Boris Lukashev
2017-05-18  3:18                     ` Kees Cook
2017-05-19  2:48                       ` Peter Dolding
2017-05-19  4:08                         ` Boris Lukashev
2017-05-19 14:33                         ` Serge E. Hallyn
2017-05-29 10:42                           ` Peter Dolding
2017-05-30 15:52                             ` Serge E. Hallyn
2017-05-30 21:52                               ` Alan Cox [this message]
2017-05-31 11:27                                 ` Peter Dolding
2017-05-31 14:36                                   ` Alan Cox
2017-05-31 15:32                                     ` Serge E. Hallyn

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