On Wed, Jan 25, 2017 at 05:41:59PM +0100, Max Reitz wrote: > On 25.01.2017 17:29, Daniel P. Berrange wrote: > > On Wed, Jan 25, 2017 at 04:58:32PM +0100, Max Reitz wrote: > >> On 03.01.2017 19:27, Daniel P. Berrange wrote: > >>> This series is a continuation of previous work to support LUKS in > >>> QEMU. The existing merged code supports LUKS as a standalone > >>> driver which can be layered over/under any other QEMU block device > >>> driver. This works well when using LUKS over protocol drivers (file, > >>> rbd, iscsi, etc, etc), but has some downsides when combined with > >>> format drivers like qcow2. > >> > >> When trying out whether compressed images are actually encrypted (which > >> they are not, as I wrote in my last reply to patch 12), I noticed that > >> the user interface still has some flaws: > > > > The original code explicitly forbids this combination > > > > "qemu-img: Compression and encryption not supported at the same time" > > > > but I guess we lost the error check due to changing to use > > encryption-format as the option name > > Yes, not supporting it is completely fine, but qemu-img should refuse > that combination then (or at least warn about it).
Yep, I'll make sure the existing error message covers this scenario. > > >> One is that you actually can't convert to encrypted images any more, or > >> if you can, it doesn't seem obvious to me: > >> > >> $ ./qemu-img convert -O qcow2 --object secret,id=sec0,data=12345 \ > >> -o encryption-format=luks,luks-key-secret=sec0 \ > >> foo.qcow2 bar.qcow2 > >> qemu-img: Could not open 'bar.qcow2': Parameter 'key-secret' is required > >> for cipher > >> > >> The issue is that you have to specify the key secret as a runtime > >> parameter in addition to the creation option. Not only is that a bit > >> cumbersome, but it's also impossible because --image-opts doesn't work > >> for the output image. > > > > Yeah, this is a problem I've not figured out a solutiuon for yet - it > > also affects the previously merged bare luks format code. > > > > Somehow qemu-img needs to know which create options are also required > > to be passed when opening the newly created image. > > > > Perhaps the BlockDriver struct needs a new callback like > > > > bdrv_create_opts_to_runtime_opts(QemuOpts *copts, QemuOpts *ropts); > > Yeah, it's tough. For the moment, I'd be fine with qemu-img convert > working at all, though, even if that means having to specify the secret > twice. But I don't know if fixing the --image-opts issue is any easier > -- maybe we can allow image-opts syntax for the targets when -n is > given? Then you'd have to call qemu-img create and qemu-img convert > separately (or call qemu-img convert twice, once without -n (which > successfully creates the image but then fails when trying to open it) > and once without...), but at least there'd be a way to make it work. > > I have to admit that I personally wouldn't mind a hack in qemu-img > convert like "copy every option ending in 'key-secret' to the runtime > opts" too much. But I don't know how much that might infuriate some > other people. > > It's ugly, yes, but it would work perfectly well for now. I don't think > it would hurt us in the future. If other parameters appear that we have > to copy over, we can still implement the well-engineered solution. This turns out to be pretty trivial to implement. So although it is a bit ugly, it feels like reasonable approach to take in the short term. Regards, Daniel -- |: http://berrange.com -o- http://www.flickr.com/photos/dberrange/ :| |: http://libvirt.org -o- http://virt-manager.org :| |: http://entangle-photo.org -o- http://search.cpan.org/~danberr/ :|