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Message-ID: <99069e11-dc84-8198-5d1c-f39b18ac9971@nmatt.com>
Date: Tue, 30 May 2017 19:00:09 -0400
From: Matt Brown <matt@...tt.com>
To: Daniel Micay <danielmicay@...il.com>, Nick Kralevich <nnk@...gle.com>,
Stephen Smalley <sds@...ho.nsa.gov>, Alan Cox <gnomes@...rguk.ukuu.org.uk>,
Kees Cook <keescook@...omium.org>
Cc: Casey Schaufler <casey@...aufler-ca.com>,
Boris Lukashev <blukashev@...pervictus.com>,
Greg KH <gregkh@...uxfoundation.org>, "Serge E. Hallyn" <serge@...lyn.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 v7 2/2] security: tty: make TIOCSTI
ioctl require CAP_SYS_ADMIN
On 5/30/17 4:22 PM, Daniel Micay wrote:
>> Thanks, I didn't know that android was doing this. I still think this
>> feature
>> is worthwhile for people to be able to harden their systems against
>> this attack
>> vector without having to implement a MAC.
>
> Since there's a capable LSM hook for ioctl already, it means it could go
> in Yama with ptrace_scope but core kernel code would still need to be
> changed to track the owning tty. I think Yama vs. core kernel shouldn't
> matter much anymore due to stackable LSMs.
>
What does everyone think about a v8 that moves this feature under Yama and uses
the file_ioctl LSM hook?
> Not the case for perf_event_paranoid=3 where a) there's already a sysctl
> exposed which would be unfortunate to duplicate, b) there isn't an LSM
> hook yet (AFAIK).
>
> The toggles for ptrace and perf events are more useful though since
> they're very commonly used debugging features vs. this obscure, rarely
> used ioctl that in practice no one will notice is missing. It's still
> friendlier to have a toggle than a seccomp policy requiring a reboot to
> get rid of it, or worse compiling it out of the kernel.
>
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