Thread (29 messages) 29 messages, 7 authors, 2017-05-31

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

From: Alan Cox <hidden>
Date: 2017-05-30 21:54:37
Also in: lkml

quoted
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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