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Tue, 12 Nov 2019 12:07:16 +0000 (UTC) Message-ID: <5a9f329058f6633878eb7d1c7170ae2cfab7e235.camel@redhat.com> Subject: Re: [PATCH v2 00/11] RFC crypto/luks: encryption key managment using amend interface From: Maxim Levitsky To: Max Reitz , qemu-devel@nongnu.org Date: Tue, 12 Nov 2019 14:07:15 +0200 In-Reply-To: <86918b16-a3c1-4b1e-7e21-1b8e84411065@redhat.com> References: <20190912223028.18496-1-mlevitsk@redhat.com> <86918b16-a3c1-4b1e-7e21-1b8e84411065@redhat.com> Mime-Version: 1.0 X-Scanned-By: MIMEDefang 2.79 on 10.5.11.12 X-MC-Unique: ynGjU3m1N4yveMLye8fntQ-1 X-Mimecast-Spam-Score: 0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: quoted-printable X-detected-operating-system: by eggs.gnu.org: GNU/Linux 2.2.x-3.x [generic] [fuzzy] X-Received-From: 207.211.31.81 X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.23 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Kevin Wolf , "Daniel P. =?ISO-8859-1?Q?Berrang=E9?=" , qemu-block@nongnu.org, Markus Armbruster , John Snow Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" On Tue, 2019-11-12 at 12:58 +0100, Max Reitz wrote: > On 08.11.19 16:07, Maxim Levitsky wrote: > > On Fri, 2019-10-04 at 21:10 +0200, Max Reitz wrote: > > > On 13.09.19 00:30, Maxim Levitsky wrote: > > > > This patch series is continuation of my work to add encryption > > > > key managment to luks/qcow2 with luks. > > > >=20 > > > > This is second version of this patch set. > > > > The changes are mostly addressing the review feedback, > > > > plus I tested (and fixed sadly) the somewhat ugly code > > > > that allows to still write share a raw luks device, > > > > while preveting the key managment from happening in this case, > > > > as it is unsafe. > > > > I added a new iotest dedicated to that as well. > > > >=20 > > > > Best regards, > > > > =09Maxim Levitsky > > >=20 > > > At least for an RFC looks good from my perspective. I didn=E2=80=99t= look at > > > the crypto things very closely (assuming Dan would do so), and I didn= =E2=80=99t > > > check the iotests in detail. (But it definitely doesn=E2=80=99t look= like they > > > lack in breadth. Maybe I=E2=80=99d like to see a test that you canno= t have > > > other useful nodes attached to the LUKS or qcow2 node while the > > > amendment process is ongoing (because CONSISTENT_READ is unshared). = But > > > that=E2=80=99s the only thing I can think of.) > >=20 > > Could you elaborate on this?=20 > >=20 > > Inside the same process several users can access that luks node at the = same > > time while one of them changes encryption keys, since this doesn't affe= ct IO of the data. > >=20 > > Two users in same process I was *I think* told that can't do the amend = in the same time > > since qmp is protected with a lock. However since I use a block job (to= be consistent with blockdev-create) > > I wonder if several qmp amend commands couldn't race one with another. = These jobs is running > > on the block device AIO context (I changed this recently after a review= ), but stil I am not sure > > there can't be a race. > >=20 > > And when there is access to the same image from multiple processes, I d= o have a test that > > checks that as long as more that one process has the image open, noone = can change the encryption keys > > (this is only relevant for raw luks format, since for qcow2 this is for= bidden anyway). >=20 > Yes, sorry, I don=E2=80=99t remember/know where I got the qcow2 part from= . (I > probably just forgot during after reviewing that only LUKS=E2=80=99s perm= issions > are changed by this series.) >=20 > But for LUKS, those changed permissions do apply. If you can=E2=80=99t d= o > something between two different qemu instances, you can=E2=80=99t do it i= n a > single one: The file locks are equivalent to the internal permission mask= . >=20 > So if you can=E2=80=99t change the encryption keys while another process = has the > image open, you can=E2=80=99t change the encryption keys while another no= de uses > the file node in the same process. For example, you can=E2=80=99t attach= two > LUKS nodes to a single file node and then change the keys on one of the > nodes. >=20 > Max >=20 Ah, I understand now. I'll add a test for that! Best regards, =09Maxim Levitsky