From: "Serge E. Hallyn" <serge@hallyn.com>
To: Alan Cox <gnomes@lxorguk.ukuu.org.uk>
Cc: Kees Cook <keescook@chromium.org>, Matt Brown <matt@nmatt.com>,
Casey Schaufler <casey@schaufler-ca.com>,
Boris Lukashev <blukashev@sempervictus.com>,
Greg KH <gregkh@linuxfoundation.org>,
"Serge E. Hallyn" <serge@hallyn.com>,
"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 v7 2/2] security: tty: make TIOCSTI ioctl require CAP_SYS_ADMIN
Date: Thu, 1 Jun 2017 12:18:58 -0500 [thread overview]
Message-ID: <20170601171858.GA19604@mail.hallyn.com> (raw)
In-Reply-To: <20170601140812.583cf0a5@alans-desktop>
Quoting Alan Cox (gnomes@lxorguk.ukuu.org.uk):
> > I still cannot wrap my head around why providing users with a
> > protection is a bad thing. Yes, the other tty games are bad, but this
> > fixes a specific and especially bad case that is easy to kill. It's
> > got a Kconfig and a sysctl. It's not on by default. This protects the
> > common case of privileged ttys that aren't attached to consoles, etc,
>
> Which just leads to stuff not getting fixed. Like all the code out there
> today which is still vulnerable to selection based attacks because people
> didn't do the job right when "fixing" stuff because they are not
> thinking about security at a systems level but just tickboxing CVEs.
>
> I'm not against doing something to protect the container folks, but that
> something as with Android is a whitelist of ioctls. And if we need to do
Whitelist of ioctls (at least using seccomp) is not sufficient because
then we have to turn the ioctl always-off. But like you say we may want
to enable it for ptys which are created inside the container's user ns.
> this with a kernel hook lets do it properly.
>
> Remember the namespace of the tty on creation
Matt's patch does this,
> If the magic security flag is set then
> Apply a whitelist to *any* tty ioctl call where the ns doesn't
> match
Seems sensible.
> and we might as well just take the Android whitelist since they've kindly
> built it for us all!
>
> In the tty layer it ends up being something around 10 lines of code and
> some other file somewhere in security/ that's just a switch or similar
> with the whitelisted ioctl codes in it.
>
> That (or a similar SELinux ruleset) would actually fix the problem.
> SELinux would be better because it can also apply the rules when doing
> things like su/sudo/...
>
> Alan
next prev parent reply other threads:[~2017-06-01 17:18 UTC|newest]
Thread overview: 49+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-05-29 21:37 [PATCH v7 0/2] security: tty: make TIOCSTI ioctl require CAP_SYS_ADMIN Matt Brown
2017-05-29 21:37 ` [PATCH v7 1/2] security: tty: Add owner user namespace to tty_struct Matt Brown
2017-05-29 21:38 ` [PATCH v7 2/2] security: tty: make TIOCSTI ioctl require CAP_SYS_ADMIN Matt Brown
2017-05-29 22:26 ` Alan Cox
2017-05-29 23:51 ` [kernel-hardening] " Boris Lukashev
2017-05-30 0:27 ` Casey Schaufler
2017-05-30 2:00 ` Matt Brown
2017-05-30 2:46 ` Casey Schaufler
2017-05-30 3:18 ` Matt Brown
2017-05-30 12:24 ` Alan Cox
2017-05-30 16:28 ` Matt Brown
2017-05-30 16:44 ` Daniel Micay
2017-05-30 18:32 ` Stephen Smalley
2017-05-30 18:44 ` Nick Kralevich
2017-05-30 18:57 ` Matt Brown
2017-05-30 20:22 ` Daniel Micay
2017-05-30 23:00 ` Matt Brown
2017-05-30 23:40 ` Daniel Micay
2017-05-30 23:59 ` Matt Brown
2017-05-30 22:51 ` Alan Cox
2017-05-30 23:19 ` Matt Brown
2017-05-30 23:56 ` Alan Cox
2017-06-01 2:35 ` Kees Cook
2017-06-01 13:08 ` Alan Cox
2017-06-01 17:18 ` Serge E. Hallyn [this message]
2017-06-01 21:26 ` Alan Cox
2017-06-01 18:58 ` Kees Cook
2017-06-01 21:24 ` Alan Cox
2017-06-02 14:46 ` Matt Brown
2017-06-02 15:36 ` Serge E. Hallyn
2017-06-02 16:02 ` Matt Brown
2017-06-02 16:57 ` Serge E. Hallyn
2017-06-02 17:32 ` Matt Brown
2017-06-02 18:18 ` Serge E. Hallyn
2017-06-02 19:22 ` Matt Brown
2017-06-02 19:25 ` Kees Cook
2017-06-02 19:26 ` Matt Brown
2017-06-02 20:05 ` Alan Cox
2017-06-02 20:11 ` Nick Kralevich
2017-06-02 20:46 ` Matt Brown
2017-06-03 22:00 ` Alan Cox
2017-06-03 22:22 ` Matt Brown
2017-06-04 3:37 ` Peter Dolding
2017-05-30 15:20 ` Casey Schaufler
2017-05-30 16:09 ` Matt Brown
2017-06-04 6:29 ` Boris Lukashev
2017-05-31 2:48 ` James Morris
2017-05-31 4:10 ` Matt Brown
2017-05-30 0:15 ` Matt Brown
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