By enhancing the LUKS driver, it is possible to enable
the detachable LUKS header and, as a result, achieve
general encryption for any disk format that QEMU has
supported.
Take the qcow2 as an example, the usage of the generic
LUKS encryption as follows:
1. add a protocol blockdev node of data disk
$ virsh qemu-monitor-command vm '{"execute":"blockdev-add",
> "arguments":{"node-name":"libvirt-1-storage", "driver":"file",
> "filename":"/path/to/test_disk.qcow2"}}'
2. add a protocol blockdev node of LUKS header as above.
$ virsh qemu-monitor-command vm '{"execute":"blockdev-add",
> "arguments":{"node-name":"libvirt-2-storage", "driver":"file",
> "filename": "/path/to/cipher.gluks" }}'
3. add the secret for decrypting the cipher stored in LUKS
header above
$ virsh qemu-monitor-command vm '{"execute":"object-add",
> "arguments":{"qom-type":"secret", "id":
> "libvirt-2-storage-secret0", "data":"abc123"}}'
4. add the qcow2-drived blockdev format node
$ virsh qemu-monitor-command vm '{"execute":"blockdev-add",
> "arguments":{"node-name":"libvirt-1-format", "driver":"qcow2",
> "file":"libvirt-1-storage"}}'
5. add the luks-drived blockdev to link the qcow2 disk with
LUKS header by specifying the field "header"
$ virsh qemu-monitor-command vm '{"execute":"blockdev-add",
> "arguments":{"node-name":"libvirt-2-format", "driver":"luks",
> "file":"libvirt-1-format", "header":"libvirt-2-storage",
> "key-secret":"libvirt-2-format-secret0"}}'
6. add the virtio-blk device finally
$ virsh qemu-monitor-command vm '{"execute":"device_add",
> "arguments": {"num-queues":"1", "driver":"virtio-blk-pci",
> "drive": "libvirt-2-format", "id":"virtio-disk2"}}'
The generic LUKS encryption method of starting a virtual
machine (VM) is somewhat similar to hot-plug in that both
maintaining the same json command while the starting VM
changes the "blockdev-add/device_add" parameters to
"blockdev/device".
Signed-off-by: Hyman Huang <yong.hu...@smartx.com>
---
block/crypto.c | 38 +++++++++++++++++++++++++++++++++++++-
1 file changed, 37 insertions(+), 1 deletion(-)
diff --git a/block/crypto.c b/block/crypto.c
index f82b13d32b..7d70349463 100644
--- a/block/crypto.c
+++ b/block/crypto.c
@@ -40,6 +40,7 @@ struct BlockCrypto {
QCryptoBlock *block;
bool updating_keys;
BdrvChild *header; /* Reference to the detached LUKS header */
+ bool detached_mode; /* If true, LUKS plays a detached header role */
};
@@ -64,12 +65,16 @@ static int block_crypto_read_func(QCryptoBlock *block,
Error **errp)
{
BlockDriverState *bs = opaque;
+ BlockCrypto *crypto = bs->opaque;
ssize_t ret;
GLOBAL_STATE_CODE();
GRAPH_RDLOCK_GUARD_MAINLOOP();
- ret = bdrv_pread(bs->file, offset, buflen, buf, 0);
+ if (crypto->detached_mode)
+ ret = bdrv_pread(crypto->header, offset, buflen, buf, 0);
+ else
+ ret = bdrv_pread(bs->file, offset, buflen, buf, 0);
if (ret < 0) {
error_setg_errno(errp, -ret, "Could not read encryption header");
return ret;
@@ -269,6 +274,8 @@ static int block_crypto_open_generic(QCryptoBlockFormat
format,
QCryptoBlockOpenOptions *open_opts = NULL;
unsigned int cflags = 0;
QDict *cryptoopts = NULL;
+ const char *header_bdref =
+ qdict_get_try_str(options, "header");
GLOBAL_STATE_CODE();
@@ -277,6 +284,16 @@ static int block_crypto_open_generic(QCryptoBlockFormat
format,
return ret;
}
+ if (header_bdref) {
+ crypto->detached_mode = true;
+ crypto->header = bdrv_open_child(NULL, options, "header", bs,
+ &child_of_bds, BDRV_CHILD_METADATA,
+ false, errp);
+ if (!crypto->header) {
+ return -EINVAL;
+ }
+ }
+
GRAPH_RDLOCK_GUARD_MAINLOOP();
bs->supported_write_flags = BDRV_REQ_FUA &
@@ -312,6 +329,14 @@ static int block_crypto_open_generic(QCryptoBlockFormat
format,
goto cleanup;
}
+ if (crypto->detached_mode) {
+ /*
+ * Set payload offset to zero as the file bdref has no LUKS
+ * header under detached mode.
+ */
+ qcrypto_block_set_payload_offset(crypto->block, 0);
+ }
+
bs->encrypted = true;
ret = 0;
@@ -903,6 +928,17 @@ block_crypto_child_perms(BlockDriverState *bs, BdrvChild
*c,
BlockCrypto *crypto = bs->opaque;
+ if (role == (role & BDRV_CHILD_METADATA)) {
+ /* Assign read permission only */
+ perm |= BLK_PERM_CONSISTENT_READ;
+ /* Share all permissions */
+ shared |= BLK_PERM_ALL;
+
+ *nperm = perm;
+ *nshared = shared;
+ return;
+ }
+
bdrv_default_perms(bs, c, role, reopen_queue, perm, shared, nperm,
nshared);
/*
--
2.39.1
