Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 23.128.96.18 as permitted sender) client-ip=23.128.96.18;
Organization: Red Hat UK Ltd. Registered Address: Red Hat UK Ltd, Amberley
        Place, 107-111 Peascod Street, Windsor, Berkshire, SI4 1TE, United
        Kingdom.
        Registered in England and Wales under Company Registration No. 3798903
From:   David Howells <dhowells@redhat.com>
In-Reply-To: <6b362abd95b116e26c65809a3a1525c7951ed0bd.camel@pengutronix.de>
References: <6b362abd95b116e26c65809a3a1525c7951ed0bd.camel@pengutronix.de> <8b9477e150d7c939dc0def3ebb4443efcc83cd85.camel@pengutronix.de> <74830d4f-5a76-8ba8-aad0-0d79f7c01af9@pengutronix.de> <6dc99fd9ffbc5f405c5f64d0802d1399fc6428e4.camel@kernel.org> <d1bed49f89495ceb529355cb41655a208fdb2197.camel@linux.ibm.com> <4153718.1612179361@warthog.procyon.org.uk>
To:     Jan =?us-ascii?Q?=3D=3FISO-8859-1=3FQ=3FL=3DFCbbe=3F=3D?= 
        <jlu@pengutronix.de>
Cc:     dhowells@redhat.com, Mimi Zohar <zohar@linux.ibm.com>,
        Jarkko Sakkinen <jarkko@kernel.org>,
        Ahmad Fatoum <a.fatoum@pengutronix.de>,
        James Bottomley <jejb@linux.ibm.com>, keyrings@vger.kernel.org,
        Sumit Garg <sumit.garg@linaro.org>,
        linux-integrity@vger.kernel.org, linux-kernel@vger.kernel.org,
        linux-security-module@vger.kernel.org, kernel@pengutronix.de
Subject: Re: Migration to trusted keys: sealing user-provided key?
MIME-Version: 1.0
Content-Type: text/plain; charset=utf-8
Content-Transfer-Encoding: quoted-printable
Date:   Mon, 01 Feb 2021 17:04:22 +0000
Message-ID: <35960.1612199062@warthog.procyon.org.uk>
Precedence: bulk

Jan L=C3=BCbbe <jlu@pengutronix.de> wrote:

> > > ... But at this point, you can still do 'keyctl read' on that key, ex=
posing
> > > the key material to user space.
> >=20
> > I wonder if it would help to provide a keyctl function to mark a key as=
 being
> > permanently unreadable - so that it overrides the READ permission bit.
> >=20
> > Alternatively, you can disable READ and SETATTR permission - but that t=
hen
> > prevents you from removing other perms if you want to :-/
>=20
> That would mean using user type keys, right? Then we'd still have the core
> problem how a master key can be protected against simply reading it from
> flash/disk, as it would be unencrypted in this scenario.

It would apply to any type of key or keyring on which it was set.  It would
cause keyctl_read() on a flagged key to return EPERM.

David