Re: [kernel-hardening] Re: [PATCH v6 0/2] security: tty: make TIOCSTI ioctl require CAP_SYS_ADMIN

From	Alan Cox <gnomes@lxorguk.ukuu.org.uk>
Newsgroups	linux.kernel
Subject	Re: [kernel-hardening] Re: [PATCH v6 0/2] security: tty: make TIOCSTI ioctl require CAP_SYS_ADMIN
Date	2017-05-31 00:00 +0200
Message-ID	<tMXli-4i6-61@gated-at.bofh.it> (permalink)
References	(6 earlier) <tIk8O-3UF-5@gated-at.bofh.it> <tIG9k-3ZH-9@gated-at.bofh.it> <tIRep-3xO-1@gated-at.bofh.it> <tMqpk-72M-7@gated-at.bofh.it> <tMRIS-Op-23@gated-at.bofh.it>
Organization	Intel Corporation

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> > 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

Thread

Re: [kernel-hardening] Re: [PATCH v6 0/2] security: tty: make TIOCSTI  ioctl require CAP_SYS_ADMIN Peter Dolding <oiaohm@gmail.com> - 2017-05-29 12:50 +0200
  Re: [kernel-hardening] Re: [PATCH v6 0/2] security: tty: make  TIOCSTI ioctl require CAP_SYS_ADMIN "Serge E. Hallyn" <serge@hallyn.com> - 2017-05-30 18:00 +0200
    Re: [kernel-hardening] Re: [PATCH v6 0/2] security: tty: make  TIOCSTI ioctl require CAP_SYS_ADMIN Alan Cox <gnomes@lxorguk.ukuu.org.uk> - 2017-05-31 00:00 +0200
      Re: [kernel-hardening] Re: [PATCH v6 0/2] security: tty: make TIOCSTI  ioctl require CAP_SYS_ADMIN Peter Dolding <oiaohm@gmail.com> - 2017-05-31 13:30 +0200
        Re: [kernel-hardening] Re: [PATCH v6 0/2] security: tty: make  TIOCSTI ioctl require CAP_SYS_ADMIN Alan Cox <gnomes@lxorguk.ukuu.org.uk> - 2017-05-31 16:40 +0200
          Re: [kernel-hardening] Re: [PATCH v6 0/2] security: tty: make  TIOCSTI ioctl require CAP_SYS_ADMIN "Serge E. Hallyn" <serge@hallyn.com> - 2017-05-31 17:40 +0200

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