On Tue, Feb 20, 2024 at 12:04:42AM +0800, Hyman Huang wrote: > Signed-off-by: Hyman Huang <yong.hu...@smartx.com> > --- > 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 <yong.hu...@smartx.com> > S: Maintained > F: tests/qemu-iotests/tests/luks-detached-header > +F: docs/devel/luks-detached-header.rst > > D-Bus > M: Marc-André Lureau <marcandre.lur...@redhat.com> > diff --git a/docs/devel/luks-detached-header.rst > b/docs/devel/luks-detached-header.rst > new file mode 100644 > index 0000000000..15e9ccde1d > --- /dev/null > +++ b/docs/devel/luks-detached-header.rst
The new file neeeds adding to an index. We don't have anywhere for crypto yet, so I'm starting a crypto section thus: diff --git a/docs/devel/crypto.rst b/docs/devel/crypto.rst new file mode 100644 index 0000000000..39b1c910e7 --- /dev/null +++ b/docs/devel/crypto.rst @@ -0,0 +1,10 @@ +.. _crypto-ref: + +==================== +Cryptography in QEMU +==================== + +.. toctree:: + :maxdepth: 2 + + luks-detached-header diff --git a/docs/devel/index-internals.rst b/docs/devel/index-internals.rst index 5636e9cf1d..4ac7725d72 100644 --- a/docs/devel/index-internals.rst +++ b/docs/devel/index-internals.rst @@ -20,3 +20,4 @@ Details about QEMU's various subsystems including how to add features to them. vfio-iommufd writing-monitor-commands virtio-backends + crypto > @@ -0,0 +1,182 @@ > +================================ > +LUKS volume with detached header > +================================ > + > +Introduction > +============ > + > +This document gives an overview of the design of LUKS volume with detached > +header and how to use it. > + > +Background > +========== > + > +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 > +============ > + > +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 > +===== > + > +Create a LUKS disk with a detached header using qemu-img > +-------------------------------------------------------- > + > +Shell commandline:: > + > +# qemu-img create --object secret,id=sec0,data=abc123 -f luks \ > +> -o cipher-alg=aes-256,cipher-mode=xts -o key-secret=sec0 \ > +> -o detached-header=true 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"}}' This needs indentation by 2 spaces, and the ">" can be dropped. The same for all examples that follow. I'm going to make those changes and queue this patch, since they're trivial. With regards, Daniel -- |: https://berrange.com -o- https://www.flickr.com/photos/dberrange :| |: https://libvirt.org -o- https://fstop138.berrange.com :| |: https://entangle-photo.org -o- https://www.instagram.com/dberrange :|