Re: [Qemu-devel] [PATCH v2 2/2] block: export LUKS specific data to qemu-img info

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

On Tue, Jun 14, 2016 at 05:38:36PM +0200, Max Reitz wrote:
> On 14.06.2016 12:56, Daniel P. Berrange wrote:
> > 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       | 59 ++++++++++++++++++++++++++++++++++++++++++++++++++++
> >  qapi/block-core.json |  7 ++++++-
> >  2 files changed, 65 insertions(+), 1 deletion(-)
> > 
> > diff --git a/block/crypto.c b/block/crypto.c
> > index 758e14e..823572f 100644
> > --- a/block/crypto.c
> > +++ b/block/crypto.c
> > @@ -565,6 +565,63 @@ 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;
> 
> One space too many.
> 
> > +    spec_info->u.luks.data = g_new(QCryptoBlockInfoLUKS, 1);
> > +    spec_info->u.luks.data->cipher_alg = info->u.luks.cipher_alg;
> > +    spec_info->u.luks.data->cipher_mode = info->u.luks.cipher_mode;
> > +    spec_info->u.luks.data->ivgen_alg = info->u.luks.ivgen_alg;
> > +    spec_info->u.luks.data->has_ivgen_hash_alg =
> > +        info->u.luks.has_ivgen_hash_alg;
> > +    spec_info->u.luks.data->ivgen_hash_alg = info->u.luks.ivgen_hash_alg;
> > +    spec_info->u.luks.data->hash_alg = info->u.luks.hash_alg;
> > +    spec_info->u.luks.data->payload_offset = info->u.luks.payload_offset;
> > +    spec_info->u.luks.data->master_key_iters = info->u.luks.master_key_iters;
> > +    spec_info->u.luks.data->uuid = g_strdup(info->u.luks.uuid);
> > +
> > +    /* Steal the pointer instead of bothering to copy */
> > +    spec_info->u.luks.data->slots = info->u.luks.slots;
> > +    info->u.luks.slots = NULL;
> 
> Why not just steal everything by *spec_info->u.luks.data = info->u.luks
> and then making sure the qapi_free() call below won't free anything in
> there with a memset(&info->u.luks, 0, sizeof(info->u.luks))?

I wish we could, but info->u.luks is an embedded QCryptoBlockInfoLUKS,
not merely a pointer to an independently allocated QCryptoBlockInfoLUKS :-(


Regards,
Daniel
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