[libvirt] [PATCH 2/2] storage: remove "luks" storage volume type
Daniel P. Berrange
berrange at redhat.com
Wed Jul 27 08:29:29 UTC 2016
On Wed, Jul 27, 2016 at 08:44:53AM +0200, Martin Kletzander wrote:
> On Tue, Jul 26, 2016 at 07:12:30PM +0100, Daniel P. Berrange wrote:
> > The current LUKS support has a "luks" volume type which has
> > a "luks" encryption format.
> >
> > This partially makes sense if you consider the QEMU shorthand
> > syntax only requires you to specify a format=luks, and it'll
> > automagically uses "raw" as the next level driver. QEMU will
> > however let you override the "raw" with any other driver it
> > supports (vmdk, qcow, rbd, iscsi, etc, etc)
> >
> > IOW the intention though is that the "luks" encryption format
> > is applied to all disk formats (whether raw, qcow2, rbd, gluster
> > or whatever). As such it doesn't make much sense for libvirt
> > to say the volume type is "luks" - we should be saying that it
> > is a "raw" file, but with "luks" encryption applied.
> >
> > IOW, when creating a storage volume we should use this XML
> >
> > <volume>
> > <name>demo.raw</name>
> > <capacity>5368709120</capacity>
> > <target>
> > <format type='raw'/>
> > <encryption format='luks'>
> > <secret type='passphrase' uuid='0a81f5b2-8403-7b23-c8d6-21ccd2f80d6f'/>
> > </encryption>
> > </target>
> > </volume>
> >
> > and when configuring a guest disk we should use
> >
> > <disk type='file' device='disk'>
> > <driver name='qemu' type='raw'/>
> > <source file='/home/berrange/VirtualMachines/demo.raw'/>
> > <target dev='sda' bus='scsi'/>
> > <encryption format='luks'>
> > <secret type='passphrase' uuid='0a81f5b2-8403-7b23-c8d6-21ccd2f80d6f'/>
> > </encryption>
> > </disk>
> >
> > This commit thus removes the "luks" storage volume type added
> > in
> >
> > commit 318ebb36f1027b3357a32d6f781bd77d7a9043fd
> > Author: John Ferlan <jferlan at redhat.com>
> > Date: Tue Jun 21 12:59:54 2016 -0400
> >
> > util: Add 'luks' to the FileTypeInfo
> >
> > The storage file probing code is modified so that it can probe
> > the actual encryption formats explicitly, rather than merely
> > probing existance of encryption and letting the storage driver
> > guess the format.
> >
> > The rest of the code is then adapted to deal with
> > VIR_STORAGE_FILE_RAW w/ VIR_STORAGE_ENCRYPTION_FORMAT_LUKS
> > instead of just VIR_STORAGE_FILE_LUKS.
> >
> > The commit mentioned above was included in libvirt v2.0.0.
> > So when querying volume XML this will be a change in behaviour
> > vs the 2.0.0 release - it'll report 'raw' instead of 'luks'
> > for the volume format, but still report 'luks' for encryption
> > format. I think this change is OK because the storage driver
> > did not include any support for creating volumes, nor starting
> > guets with luks volumes in v2.0.0 - that only since then.
> > Clearly if we change this we must do it before v2.1.0 though.
> >
> > Signed-off-by: Daniel P. Berrange <berrange at redhat.com>
> > ---
> > src/qemu/qemu_command.c | 10 +-
> > src/qemu/qemu_domain.c | 2 +-
> > src/qemu/qemu_hotplug.c | 2 +-
> > src/storage/storage_backend.c | 41 +++--
> > src/storage/storage_backend_fs.c | 17 +-
> > src/storage/storage_backend_gluster.c | 5 -
> > src/util/virstoragefile.c | 202 ++++++++++++++++-----
> > src/util/virstoragefile.h | 1 -
> > tests/qemuxml2argvdata/qemuxml2argv-luks-disks.xml | 4 +-
> > tests/storagevolxml2xmlin/vol-luks-cipher.xml | 2 +-
> > tests/storagevolxml2xmlin/vol-luks.xml | 2 +-
> > tests/storagevolxml2xmlout/vol-luks-cipher.xml | 2 +-
> > tests/storagevolxml2xmlout/vol-luks.xml | 2 +-
> > 13 files changed, 198 insertions(+), 94 deletions(-)
> >
> > diff --git a/src/storage/storage_backend.c b/src/storage/storage_backend.c
> > index 862fb29..5ef536a 100644
> > --- a/src/storage/storage_backend.c
> > +++ b/src/storage/storage_backend.c
> > @@ -1116,9 +1111,9 @@ virStorageBackendCreateQemuImgSetBacking(virStoragePoolObjPtr pool,
> > int accessRetCode = -1;
> > char *absolutePath = NULL;
> >
> > - if (info->format == VIR_STORAGE_FILE_LUKS) {
> > + if (info->format == VIR_STORAGE_FILE_RAW) {
> > virReportError(VIR_ERR_CONFIG_UNSUPPORTED, "%s",
> > - _("cannot set backing store for luks volume"));
> > + _("cannot set backing store for raw volume"));
> > return -1;
> > }
> >
>
> I think this whole condition can be removed as it wasn't there before
> luks volumes.
>
> > @@ -1283,7 +1278,8 @@ virStorageBackendCreateQemuImgCmdFromVol(virConnectPtr conn,
> > _("format features only available with qcow2"));
> > return NULL;
> > }
> > - if (info.format == VIR_STORAGE_FILE_LUKS) {
> > + if (info.format == VIR_STORAGE_FILE_RAW &&
> > + vol->target.encryption != NULL) {
> > if (inputvol) {
> > virReportError(VIR_ERR_CONFIG_UNSUPPORTED, "%s",
> > _("cannot use inputvol with luks volume"));
>
> You're still reporting the error for "luks volume" here.
>
> > @@ -1484,13 +1490,16 @@ virStorageBackendGetBuildVolFromFunction(virStorageVolDefPtr vol,
> > if (!inputvol)
> > return NULL;
> >
> > - /* If either volume is a non-raw file vol, we need to use an external
> > - * tool for converting
> > + VIR_WARN("BUild vol from func");
>
> Leftover from debugging?
>
> > diff --git a/src/util/virstoragefile.c b/src/util/virstoragefile.c
> > index 2834baa..c264041 100644
> > --- a/src/util/virstoragefile.c
> > +++ b/src/util/virstoragefile.c
> > @@ -808,6 +882,45 @@ qcow2GetFeatures(virBitmapPtr *features,
> > }
> >
> >
> > +static bool
> > +virStorageFileHasEncryptionFormat(const struct FileEncryptionInfo *info,
> > + char *buf,
> > + size_t len)
> > +{
> > + if (!info->magic && info->modeOffset == -1)
> > + return 0; /* Shouldn't happen - expect at least one */
> > +
> > + if (info->magic) {
> > + if (!virStorageFileMatchesMagic(info->magicOffset,
> > + info->magic,
> > + buf, len))
> > + return false;
> > +
> > + if (info->versionOffset != -1 &&
> > + !virStorageFileMatchesVersion(info->versionOffset,
> > + info->versionSize,
> > + info->versionNumbers,
> > + info->endian,
> > + buf, len))
> > + return false;
> > +
> > + return true;
> > + } else if (info->modeOffset != -1) {
> > + if (info->modeOffset >= len)
> > + return false;
> > +
> > + if (buf[info->modeOffset] != info->modeValue)
> > + return false;
> > +
> > + return true;
> > + } else {
> > + return false;
> > + }
> > +}
> > +
> > +
> > +
> > +
>
> Getting used to 2 empty lines took me some time, but we're going four
> now? Should I look for campaigns proclaiming "Four is the new Two!"? =)
>
> > @@ -820,6 +933,7 @@ virStorageFileGetMetadataInternal(virStorageSourcePtr meta,
> > int *backingFormat)
> > {
> > int ret = -1;
> > + size_t j;
> >
>
> Why 'j'?
>
> Apart from those first three nits pointed out the patch is fine. I also
> like the fact that it automatically get's rid of a problem with
> format='luks' and no encryption specified (where we just waited for QEMU
> to fail at startup). The problem is that, as you said, it was released
> in v2.0.0 and you can have a domain with such disk. I think we need to
> make a workaround where "luks" is some kind of alias to "raw" (but also
> make sure it will require encryption because you could have luks without
> encryption secret). At least we don't have that in the documentation
> (even though it should've been).
No, you can't have a domain with type="luks" AFAICT. QEMU LUKS support
was added in:
commit da86c6c22674ccc147224afa2740e33d8cbdbf22
Author: John Ferlan <jferlan at redhat.com>
Date: Thu Jun 2 16:28:28 2016 -0400
qemu: Add luks support for domain disk
Which is not yet released as its post-2.0.0:
$ git describe da86c6c22674ccc147224afa2740e33d8cbdbf22
v2.0.0-204-gda86c6c
AFAIK, all that v2.0.0 did was allow 'vol-dumpxml' to show "luks" for
pre-existing files formatted with luks outside of libvirt. I think
the number of people using that will be approximately zero, and even
then I think its reasonable to argue that behaviour was a regression
from pre-2.0.0, since people's 'raw' disks suddenly changed to 'luks'
Regards,
Daniel
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