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 318ebb36
  Author: John Ferlan <jferlan@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: NDaniel P. Berrange <berrange@redhat.com>

Commit id's '9bbf0d7e' and '2552fec2' added some XML parsing tests
for a LUKS volume to use a 'passphrase' secret format. After commit,
this was deemed to be incorrect, so covert the various tests to use
the volume usage format where the 'usage' is the path to the volume
rather than a user defined name string.

Also, removed the qemuxml2argv-luks-disk-cipher.xml since it was
just a duplicate of qemuxml2argv-luks-disks.xml.
Signed-off-by: NJohn Ferlan <jferlan@redhat.com>

For a luks device, allow the configuration of a specific cipher to be
used for encrypting the volume.
Signed-off-by: NJohn Ferlan <jferlan@redhat.com>

Add parse and format of the luks/passphrase secret including tests for
volume XML parsing.
Signed-off-by: NJohn Ferlan <jferlan@redhat.com>

I got annoyed at having to use both 'virsh vol-list $pool --details'
AND 'virsh vol-dumpxml $vol $pool' to learn if I had populated
the volume correctly.  Since two-thirds of the data present in
virStorageVolGetInfo() already appears in virStorageVolGetXMLDesc(),
this just adds the remaining piece of information, as:

<volume type='...'>
  ...
</volume>

* docs/formatstorage.html.in: Document new <volume type=...>.
* docs/schemas/storagevol.rng (vol): Add it to RelaxNG.
* src/conf/storage_conf.h (virStorageVolTypeToString): Declare.
* src/conf/storage_conf.c (virStorageVolTargetDefFormat): Output
the metatype.
(virStorageVolDefParseXML): Parse it, for unit tests.
* tests/storagevolxml2xmlout/vol-*.xml: Update tests to match.
Signed-off-by: NEric Blake <eblake@redhat.com>

$ touch /var/lib/libvirt/images/'a<b>c'
$ virsh pool-refresh default
$ virsh vol-dumpxml 'a<b>c' default | head -n2
<volume>
  <name>a<b>c</name>

Oops.  That's not valid XML.  And when we fix the XML
generation, it fails RelaxNG validation.

I'm also tired of seeing <key>(null)</key> in the example
output for volume xml; while we used NULLSTR() to avoid
a NULL deref rather than relying on glibc's printf
extension behavior, it's even better if we avoid the issue
in the first place.  But this requires being careful that
we don't invalidate any storage backends that were relying
on key being unassigned during virStoragVolCreateXML[From].

I would have split this into two patches (one for escaping,
one for avoiding <key>(null)</key>), but since they both
end up touching a lot of the same test files, I ended up
merging it into one.

Note that this patch allows pretty much any volume name
that can appear in a directory (excluding . and .. because
those are special), but does nothing to change the current
(unenforced) RelaxNG claim that pool names will consist
only of letters, numbers, _, -, and +.  Tightening the C
code to match RelaxNG patterns and/or relaxing the grammar
to match the C code for pool names is a task for another
day (but remember, we DID recently tighten C code for
domain names to exclude a leading '.').

* src/conf/storage_conf.c (virStoragePoolSourceFormat)
(virStoragePoolDefFormat, virStorageVolTargetDefFormat)
(virStorageVolDefFormat): Escape user-controlled strings.
(virStorageVolDefParseXML): Parse key, for use in unit tests.
* src/storage/storage_driver.c (storageVolCreateXML)
(storageVolCreateXMLFrom): Ensure parsed key doesn't confuse
volume creation.
* docs/schemas/basictypes.rng (volName): Relax definition.
* tests/storagepoolxml2xmltest.c (mymain): Test it.
* tests/storagevolxml2xmltest.c (mymain): Likewise.
* tests/storagepoolxml2xmlin/pool-dir-naming.xml: New file.
* tests/storagepoolxml2xmlout/pool-dir-naming.xml: Likewise.
* tests/storagevolxml2xmlin/vol-file-naming.xml: Likewise.
* tests/storagevolxml2xmlout/vol-file-naming.xml: Likewise.
* tests/storagevolxml2xmlout/vol-*.xml: Fix fallout.
Signed-off-by: NEric Blake <eblake@redhat.com>

Reuse the XML files in storagevolxml2xmlin.

(This requires changing a few backing files to /dev/null,
since virStorageBackendCreateQemuImgCmd checks for its
presence)

The XML allows <encryption format='unencrypted'/>, this implementation
canonicalizes the internal representation so that "vol->encryption" is
non-NULL iff the volume is encrypted.

Note that partial encryption information (e.g. specifying an encryption
format, but not the key/passphrase) is valid, libvirt will automatically
choose value for the missing information during volume creation.  The
user can read the volume XML, and use the unmodified <encryption> tag in
future operations (without having to be able to understand) its contents.

* docs/formatstorage.html, docs/formatstorage.html.in: Document
  storage volume encryption options
* src/storage_conf.c, src/storage_conf.h: Hook up storage
  encryption XML handling
* tests/storagevolschemadata/vol-qcow2.xml: Test case for encryption
  schema changes

* docs/schemas/storagevol.rng docs/formatstorage.html[.in]
  tests/storagevolschemadata/vol-qcow2.xml: fix storage volume
  inconsistencies in schema and document, patch by Ryota Ozaki
daniel