On 04/18/2018 08:17 AM, Daniel P. Berrangé wrote:
On Wed, Apr 18, 2018 at 08:08:41AM -0400, John Ferlan wrote:
On 04/18/2018 04:29 AM, Daniel P. Berrangé wrote:
On Tue, Apr 17, 2018 at 03:23:33PM -0400, John Ferlan wrote:
https://bugzilla.redhat.com/show_bug.cgi?id=1526382
As of QEMU 2.9, qemu-img has enforced using the "key-secret" for creation of encrypted volumes. That is, LUKS encryption is now required and the old (awful) qcow[2] encryption methodolgy is no longer supported.
Not quite right actually. The 'key-secret' approach can be used to create both LUKS and the old qcow[2] encryption.
We only forbid qcow[2] encryption with the system emulators, still have full support in qemu-img for sake of interoperability. The only break there was the command line syntax
Oh, OK - well I didn't find that to be obvious... So there is a way using secret objects to create a qcow[2] encrypted volume?
Sure, the exact same syntax as with luks volumes - you just specify "qcow" instead of "luks" as the type.
Still Jano has NACK'd using help scraping (and posted a separate series removing it completely).
So then the question becomes does this change "convert" into a disallow this type of creation going forward? Do we just cause failure in storageBackendCreateQemuImgCheckEncryption when not using LUKS or do we let the qemu-img just be the bad guy and do nothing in our code?
QEMU is likely to support the qcow2 enc format indefinitely, but only in the qemu-img tool for the sake of data liberation. I don't think libvirt should arbitrarily decide to drop it from our qemu-img usage.
So that means Jano's series to remove help scraping completely cannot be applied since this code would need to check that the option exists before using it; otherwise, anything inclusive of QEMU 1.5 and 2.9 would fail (the option was introduced in 2.10 - I mistyped above). What could be applied would be the removal of OPTIONS and OPTIONS_COMPAT, but this new one would need to exist since AFAIK there is no other way currently to query qemu-img for what it supports. Going to make for some ugly code... John
+ if (imgformat >= QEMU_IMG_BACKING_FORMAT_OPTIONS_KEY_SECRET) { + virReportError(VIR_ERR_CONFIG_UNSUPPORTED, "%s", + _("qemu-img no longer supports qcow encryption, " + "use LUKS encryption instead")); + return -1; + }
Why is imgformat being compared against QEMU_IMG_BACKING_FORMAT_OPTIONS_KEY_SECRET ?
Aren't those two sides of the expression from completely different enum types.
Although perhaps not well named, @imgformat is fetched via virStorageBackendQEMUImgBackingFormat which returns QEMU_IMG_BACKING_FORMAT_OPTIONS* type enum's.
Regards, Daniel