From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from lists.gnu.org (lists.gnu.org [209.51.188.17]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id 8D8BDC4345F for ; Mon, 6 May 2024 06:27:39 +0000 (UTC) Received: from localhost ([::1] helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1s3roL-0004e0-25; Mon, 06 May 2024 02:26:53 -0400 Received: from eggs.gnu.org ([2001:470:142:3::10]) by lists.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1s3ro1-0004cM-FE for qemu-devel@nongnu.org; Mon, 06 May 2024 02:26:35 -0400 Received: from us-smtp-delivery-124.mimecast.com ([170.10.129.124]) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1s3rnl-0000LY-Pm for qemu-devel@nongnu.org; Mon, 06 May 2024 02:26:33 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1714976776; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=oPGNUcDT1ywZ5yrydxemGJ4yo0FAE4ciOBPuv/1/CKA=; b=Kba9D1hGo2JmysobWFGm/jg6ZBHe859rZ+IM2qa3MXuu65yWsGLAT680UG87MqoDyXUnkB PZnBXY/+o8UFPE5BciWqF7v7UAEV8U/hLLITPZf1B/RTGWQ//Jhs3Hx+zzSvKV0zHWr8ws vCCvjC9wK0x4OS58Jz4JtthxI7AUFc0= Received: from mimecast-mx02.redhat.com (mimecast-mx02.redhat.com [66.187.233.88]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.3, cipher=TLS_AES_256_GCM_SHA384) id us-mta-505-i3MrfH4ZM6aDLEKkn6qXzg-1; Mon, 06 May 2024 02:26:12 -0400 X-MC-Unique: i3MrfH4ZM6aDLEKkn6qXzg-1 Received: from smtp.corp.redhat.com (int-mx01.intmail.prod.int.rdu2.redhat.com [10.11.54.1]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (2048 bits) server-digest SHA256) (No client certificate requested) by mimecast-mx02.redhat.com (Postfix) with ESMTPS id 0387A101150D; Mon, 6 May 2024 06:26:12 +0000 (UTC) Received: from blackfin.pond.sub.org (unknown [10.39.192.247]) by smtp.corp.redhat.com (Postfix) with ESMTPS id 7FCD3AC6B; Mon, 6 May 2024 06:26:11 +0000 (UTC) Received: by blackfin.pond.sub.org (Postfix, from userid 1000) id 70AEB21E6680; Mon, 6 May 2024 08:26:10 +0200 (CEST) From: Markus Armbruster To: Hyman Huang Cc: qemu-devel@nongnu.org, Daniel P . =?utf-8?Q?Berrang=C3=A9?= , Kevin Wolf , Hanna Reitz , Eric Blake Subject: Re: [PATCH] docs/devel: Add introduction to LUKS volume with detached header In-Reply-To: (Hyman Huang's message of "Tue, 20 Feb 2024 00:04:42 +0800") References: Date: Mon, 06 May 2024 08:26:10 +0200 Message-ID: <87cypzsbgd.fsf@pond.sub.org> User-Agent: Gnus/5.13 (Gnus v5.13) MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: quoted-printable X-Scanned-By: MIMEDefang 3.4.1 on 10.11.54.1 Received-SPF: pass client-ip=170.10.129.124; envelope-from=armbru@redhat.com; helo=us-smtp-delivery-124.mimecast.com X-Spam_score_int: -24 X-Spam_score: -2.5 X-Spam_bar: -- X-Spam_report: (-2.5 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-0.431, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, SPF_HELO_NONE=0.001, T_SPF_TEMPERROR=0.01 autolearn=ham autolearn_force=no X-Spam_action: no action X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Looks like this fell through the cracks. Is anyone familiar with LUKS willing to review it? Hyman Huang writes: > Signed-off-by: Hyman Huang > --- > MAINTAINERS | 1 + > docs/devel/luks-detached-header.rst | 182 ++++++++++++++++++++++++++++ > 2 files changed, 183 insertions(+) > create mode 100644 docs/devel/luks-detached-header.rst > > diff --git a/MAINTAINERS b/MAINTAINERS > index a24c2b51b6..e8b03032ab 100644 > --- a/MAINTAINERS > +++ b/MAINTAINERS > @@ -3422,6 +3422,7 @@ Detached LUKS header > M: Hyman Huang > S: Maintained > F: tests/qemu-iotests/tests/luks-detached-header > +F: docs/devel/luks-detached-header.rst >=20=20 > D-Bus > M: Marc-Andr=C3=A9 Lureau > diff --git a/docs/devel/luks-detached-header.rst b/docs/devel/luks-detach= ed-header.rst > new file mode 100644 > index 0000000000..15e9ccde1d > --- /dev/null > +++ b/docs/devel/luks-detached-header.rst > @@ -0,0 +1,182 @@ > +=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D= =3D=3D=3D=3D=3D=3D=3D=3D > +LUKS volume with detached header > +=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D= =3D=3D=3D=3D=3D=3D=3D=3D > + > +Introduction > +=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D > + > +This document gives an overview of the design of LUKS volume with detach= ed > +header and how to use it. > + > +Background > +=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D > + > +The LUKS format has ability to store the header in a separate volume from > +the payload. We could extend the LUKS driver in QEMU to support this use > +case. > + > +Normally a LUKS volume has a layout: > + > +:: > + > + +-----------------------------------------------+ > + | | | | > + disk | header | key material | disk payload data | > + | | | | > + +-----------------------------------------------+ > + > +With a detached LUKS header, you need 2 disks so getting: > + > +:: > + > + +--------------------------+ > + disk1 | header | key material | > + +--------------------------+ > + +---------------------+ > + disk2 | disk payload data | > + +---------------------+ > + > +There are a variety of benefits to doing this: > + > + * Secrecy - the disk2 cannot be identified as containing LUKS > + volume since there's no header > + * Control - if access to the disk1 is restricted, then even > + if someone has access to disk2 they can't unlock > + it. Might be useful if you have disks on NFS but > + want to restrict which host can launch a VM > + instance from it, by dynamically providing access > + to the header to a designated host > + * Flexibility - your application data volume may be a given > + size and it is inconvenient to resize it to > + add encryption.You can store the LUKS header > + separately and use the existing storage > + volume for payload > + * Recovery - corruption of a bit in the header may make the > + entire payload inaccessible. It might be > + convenient to take backups of the header. If > + your primary disk header becomes corrupt, you > + can unlock the data still by pointing to the > + backup detached header > + > +Architecture > +=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D > + > +Take the qcow2 encryption, for example. The architecture of the > +LUKS volume with detached header is shown in the diagram below. > + > +There are two children of the root node: a file and a header. > +Data from the disk payload is stored in the file node. The > +LUKS header and key material are located in the header node, > +as previously mentioned. > + > +:: > + > + +-----------------------------+ > + Root node | foo[luks] | > + +-----------------------------+ > + | | > + file | header | > + | | > + +---------------------+ +------------------+ > + Child node |payload-format[qcow2]| |header-format[raw]| > + +---------------------+ +------------------+ > + | | > + file | file | > + | | > + +----------------------+ +---------------------+ > + Child node |payload-protocol[file]| |header-protocol[file]| > + +----------------------+ +---------------------+ > + | | > + | | > + | | > + Host storage Host storage > + > +Usage > +=3D=3D=3D=3D=3D > + > +Create a LUKS disk with a detached header using qemu-img > +-------------------------------------------------------- > + > +Shell commandline:: > + > +# qemu-img create --object secret,id=3Dsec0,data=3Dabc123 -f luks \ > +> -o cipher-alg=3Daes-256,cipher-mode=3Dxts -o key-secret=3Dsec0 \ > +> -o detached-header=3Dtrue test-header.img > +# qemu-img create -f qcow2 test-payload.qcow2 200G > +# qemu-img info 'json:{"driver":"luks","file":{"filename": \ > +> "test-payload.img"},"header":{"filename":"test-header.img"}}' > + > +Set up a VM's LUKS volume with a detached header > +------------------------------------------------ > + > +Qemu commandline:: > + > +# qemu-system-x86_64 ... \ > +> -object '{"qom-type":"secret","id":"libvirt-3-format-secret", \ > +> "data":"abc123"}' \ > +> -blockdev '{"driver":"file","filename":"/path/to/test-header.img", \ > +> "node-name":"libvirt-1-storage"}' \ > +> -blockdev '{"node-name":"libvirt-1-format","read-only":false, \ > +> "driver":"raw","file":"libvirt-1-storage"}' \ > +> -blockdev '{"driver":"file","filename":"/path/to/test-payload.qcow2", \ > +> "node-name":"libvirt-2-storage"}' \ > +> -blockdev '{"node-name":"libvirt-2-format","read-only":false, \ > +> "driver":"qcow2","file":"libvirt-2-storage"}' \ > +> -blockdev '{"node-name":"libvirt-3-format","driver":"luks", \ > +> "file":"libvirt-2-format","header":"libvirt-1-format","key-secret": \ > +> "libvirt-3-format-secret"}' \ > +> -device '{"driver":"virtio-blk-pci","bus":XXX,"addr":YYY,"drive": \ > +> "libvirt-3-format","id":"virtio-disk1"}' > + > +Add LUKS volume to a VM with a detached header > +---------------------------------------------- > + > +1. object-add the secret for decrypting the cipher stored in > + LUKS header above:: > + > +# virsh qemu-monitor-command vm '{"execute":"object-add", \ > +> "arguments":{"qom-type":"secret", "id": \ > +> "libvirt-4-format-secret", "data":"abc123"}}' > + > +2. block-add the protocol node for LUKS header:: > + > +# virsh qemu-monitor-command vm '{"execute":"blockdev-add", \ > +> "arguments":{"node-name":"libvirt-1-storage", "driver":"file", \ > +> "filename": "/path/to/test-header.img" }}' > + > +3. block-add the raw-drived node for LUKS header:: > + > +# virsh qemu-monitor-command vm '{"execute":"blockdev-add", \ > +> "arguments":{"node-name":"libvirt-1-format", "driver":"raw", \ > +> "file":"libvirt-1-storage"}}' > + > +4. block-add the protocol node for disk payload image:: > + > +# virsh qemu-monitor-command vm '{"execute":"blockdev-add", \ > +> "arguments":{"node-name":"libvirt-2-storage", "driver":"file", \ > +> "filename":"/path/to/test-payload.qcow2"}}' > + > +5. block-add the qcow2-drived format node for disk payload data:: > + > +# virsh qemu-monitor-command vm '{"execute":"blockdev-add", \ > +> "arguments":{"node-name":"libvirt-2-format", "driver":"qcow2", \ > +> "file":"libvirt-2-storage"}}' > + > +6. block-add the luks-drived format node to link the qcow2 disk > + with the LUKS header by specifying the field "header":: > + > +# virsh qemu-monitor-command vm '{"execute":"blockdev-add", \ > +> "arguments":{"node-name":"libvirt-3-format", "driver":"luks", \ > +> "file":"libvirt-2-format", "header":"libvirt-1-format", \ > +> "key-secret":"libvirt-2-format-secret"}}' > + > +7. hot-plug the virtio-blk device finally:: > + > +# virsh qemu-monitor-command vm '{"execute":"device_add", \ > +> "arguments": {"driver":"virtio-blk-pci", \ > +> "drive": "libvirt-3-format", "id":"virtio-disk2"}} > + > +TODO > +=3D=3D=3D=3D > + > +1. Support the shared detached LUKS header within the VM.