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Wed, 5 Feb 2020 08:24:21 +0000 (UTC) Received: by blackfin.pond.sub.org (Postfix, from userid 1000) id 7109A11386A7; Wed, 5 Feb 2020 09:24:20 +0100 (CET) From: Markus Armbruster To: Daniel P. =?utf-8?Q?Berrang=C3=A9?= , Kevin Wolf Subject: Re: [PATCH 02/13] qcrypto-luks: implement encryption key management References: <20200114193350.10830-1-mlevitsk@redhat.com> <20200114193350.10830-3-mlevitsk@redhat.com> <87r1zti6r8.fsf@dusky.pond.sub.org> <20200128171116.GU1446339@redhat.com> <20200128173251.GZ1446339@redhat.com> <20200130123847.GE6438@linux.fritz.box> <20200130125319.GD1891831@redhat.com> <87zhe5ovbv.fsf@dusky.pond.sub.org> <20200130150108.GM1891831@redhat.com> <877e18oq76.fsf@dusky.pond.sub.org> Date: Wed, 05 Feb 2020 09:24:20 +0100 In-Reply-To: <877e18oq76.fsf@dusky.pond.sub.org> (Markus Armbruster's message of "Thu, 30 Jan 2020 17:37:49 +0100") Message-ID: <87mu9xxwzv.fsf@dusky.pond.sub.org> User-Agent: Gnus/5.13 (Gnus v5.13) Emacs/26.3 (gnu/linux) MIME-Version: 1.0 X-Scanned-By: MIMEDefang 2.79 on 10.5.11.15 X-MC-Unique: yUsUEbs9N3avGlQVVM8frA-1 X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Type: text/plain 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: Maxim Levitsky , John Snow , qemu-devel@nongnu.org, qemu-block@nongnu.org, Max Reitz Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" Daniel, Kevin, any comments or objections to the QAPI schema design sketch developed below? For your convenience, here's the result again: { 'enum': 'LUKSKeyslotState', 'data': [ 'active', 'inactive' ] } { 'struct': 'LUKSKeyslotActive', 'data': { 'secret': 'str', '*iter-time': 'int } } { 'union': 'LUKSKeyslotAmend', 'base': { '*keyslot': 'int', 'state': 'LUKSKeyslotState' } 'discriminator': 'state', 'data': { 'active': 'LUKSKeyslotActive' } } Markus Armbruster writes: [...] > A keyslot can be either inactive or active. > > Let's start low-level, i.e. we specify the slot by slot#: > > state new state action > inactive inactive nop > inactive active put secret, iter-time, mark active > active inactive mark inactive (effectively deletes secret) > active active in general, error (unsafe update in place) > we can make it a nop when secret, iter-time > remain unchanged > we can allow unsafe update with force: true > > As struct: > > { 'struct': 'LUKSKeyslotUpdate', > 'data': { 'active': 'bool', # could do enum instead > 'keyslot': 'int', > '*secret': 'str', # present if @active is true > '*iter-time': 'int' } } # absent if @active is false > > As union: > > { 'enum': 'LUKSKeyslotState', > 'data': [ 'active', 'inactive' ] } > { 'struct': 'LUKSKeyslotActive', > 'data': { 'secret': 'str', > '*iter-time': 'int } } > { 'union': 'LUKSKeyslotAmend', > 'base': { 'state': 'LUKSKeyslotState' } # must do enum > 'discriminator': 'state', > 'data': { 'active': 'LUKSKeyslotActive' } } > > When we don't specify the slot#, then "new state active" selects an > inactive slot (chosen by the system, and "new state inactive selects > slots by secret (commonly just one slot). > > New state active: > > state new state action > inactive active put secret, iter-time, mark active > active active N/A (system choses inactive slot) > > New state inactive, for each slot holding the specified secret: > > state new state action > inactive inactive N/A (inactive slot holds no secret) > active inactive mark inactive (effectively deletes secret) > > As struct: > > { 'struct': 'LUKSKeyslotUpdate', > 'data': { 'active': 'bool', # could do enum instead > '*keyslot': 'int', > '*secret': 'str', # present if @active is true > '*iter-time': 'int' } } # absent if @active is false > > As union: > > { 'enum': 'LUKSKeyslotState', > 'data': [ 'active', 'inactive' ] } > { 'struct': 'LUKSKeyslotActive', > 'data': { 'secret': 'str', > '*iter-time': 'int } } > { 'union': 'LUKSKeyslotAmend', > 'base': { '*keyslot': 'int', > 'state': 'LUKSKeyslotState' } > 'discriminator': 'state', > 'data': { 'active': 'LUKSKeyslotActive' } } > > Union looks more complicated because our union notation sucks[*]. I > like it anyway, because you don't have to explain when which optional > members aren't actually optional. > > Regardless of struct vs. union, this supports an active -> active > transition only with an explicit keyslot. Feels fine to me. If we want > to support it without keyslot as well, we need a way to specify both old > and new secret. Do we? > > > [*] I hope to fix that one day. It's not even hard.