[Qemu-devel] [PATCH v4 2/2] block: export LUKS specific data to qemu-img info

["Daniel P. Berrange" <berrange@redhat.com>]

The qemu-img info command has the ability to expose format
specific metadata about volumes. Wire up this facility for
the LUKS driver to report on cipher configuration and key
slot usage.

    $ qemu-img info ~/VirtualMachines/demo.luks
    image: /home/berrange/VirtualMachines/demo.luks
    file format: luks
    virtual size: 98M (102760448 bytes)
    disk size: 100M
    encrypted: yes
    Format specific information:
        ivgen alg: plain64
        hash alg: sha1
        cipher alg: aes-128
        uuid: 6ddee74b-3a22-408c-8909-6789d4fa2594
        cipher mode: xts
        slots:
            [0]:
                active: true
                iters: 572706
                key offset: 4096
                stripes: 4000
            [1]:
                active: false
                key offset: 135168
            [2]:
                active: false
                key offset: 266240
            [3]:
                active: false
                key offset: 397312
            [4]:
                active: false
                key offset: 528384
            [5]:
                active: false
                key offset: 659456
            [6]:
                active: false
                key offset: 790528
            [7]:
                active: false
                key offset: 921600
        payload offset: 2097152
        master key iters: 142375

One somewhat undesirable artifact is that the data fields are
printed out in (apparently) random order. This will be addressed
later by changing the way the block layer pretty-prints the
image specific data.

Signed-off-by: Daniel P. Berrange <berrange@redhat.com>
---
 block/crypto.c       | 49 +++++++++++++++++++++++++++++++++++++++++++++++++
 qapi/block-core.json |  6 +++++-
 2 files changed, 54 insertions(+), 1 deletion(-)

diff --git a/block/crypto.c b/block/crypto.c
index 7eaa057..7f61e12 100644
--- a/block/crypto.c
+++ b/block/crypto.c
@@ -563,6 +563,53 @@ static int block_crypto_create_luks(const char *filename,
                                        filename, opts, errp);
 }
 
+static int block_crypto_get_info_luks(BlockDriverState *bs,
+                                      BlockDriverInfo *bdi)
+{
+    BlockDriverInfo subbdi;
+    int ret;
+
+    ret = bdrv_get_info(bs->file->bs, &subbdi);
+    if (ret != 0) {
+        return ret;
+    }
+
+    bdi->unallocated_blocks_are_zero = false;
+    bdi->can_write_zeroes_with_unmap = false;
+    bdi->cluster_size = subbdi.cluster_size;
+
+    return 0;
+}
+
+static ImageInfoSpecific *
+block_crypto_get_specific_info_luks(BlockDriverState *bs)
+{
+    BlockCrypto *crypto = bs->opaque;
+    ImageInfoSpecific *spec_info;
+    QCryptoBlockInfo *info;
+
+    info = qcrypto_block_get_info(crypto->block, NULL);
+    if (!info) {
+        return NULL;
+    }
+    if (info->format != Q_CRYPTO_BLOCK_FORMAT_LUKS) {
+        qapi_free_QCryptoBlockInfo(info);
+        return NULL;
+    }
+
+    spec_info = g_new(ImageInfoSpecific, 1);
+    spec_info->type = IMAGE_INFO_SPECIFIC_KIND_LUKS;
+    spec_info->u.luks.data = g_new(QCryptoBlockInfoLUKS, 1);
+    *spec_info->u.luks.data = info->u.luks;
+
+    /* Blank out pointers we've just stolen to avoid double free */
+    memset(&info->u.luks, 0, sizeof(info->u.luks));
+
+    qapi_free_QCryptoBlockInfo(info);
+
+    return spec_info;
+}
+
 BlockDriver bdrv_crypto_luks = {
     .format_name        = "luks",
     .instance_size      = sizeof(BlockCrypto),
@@ -576,6 +623,8 @@ BlockDriver bdrv_crypto_luks = {
     .bdrv_co_readv      = block_crypto_co_readv,
     .bdrv_co_writev     = block_crypto_co_writev,
     .bdrv_getlength     = block_crypto_getlength,
+    .bdrv_get_info      = block_crypto_get_info_luks,
+    .bdrv_get_specific_info = block_crypto_get_specific_info_luks,
 };
 
 static void block_crypto_init(void)
diff --git a/qapi/block-core.json b/qapi/block-core.json
index f462345..d4bab5d 100644
--- a/qapi/block-core.json
+++ b/qapi/block-core.json
@@ -85,7 +85,11 @@
 { 'union': 'ImageInfoSpecific',
   'data': {
       'qcow2': 'ImageInfoSpecificQCow2',
-      'vmdk': 'ImageInfoSpecificVmdk'
+      'vmdk': 'ImageInfoSpecificVmdk',
+      # If we need to add block driver specific parameters for
+      # LUKS in future, then we'll subclass QCryptoBlockInfoLUKS
+      # to define a ImageInfoSpecificLUKS
+      'luks': 'QCryptoBlockInfoLUKS'
   } }
 
 ##
-- 
2.7.4