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Re: [Qemu-devel] [PATCH v3 13/18] qcow2: add support for LUKS encryption
From: |
Max Reitz |
Subject: |
Re: [Qemu-devel] [PATCH v3 13/18] qcow2: add support for LUKS encryption format |
Date: |
Thu, 9 Feb 2017 01:28:22 +0100 |
User-agent: |
Mozilla/5.0 (X11; Linux x86_64; rv:45.0) Gecko/20100101 Thunderbird/45.7.0 |
On 26.01.2017 11:18, Daniel P. Berrange wrote:
> This adds support for using LUKS as an encryption format
> with the qcow2 file. The use of the existing 'encryption=on'
> parameter is replaced by a new parameter 'encryption-format'
> which takes the values 'aes' or 'luks'. e.g.
>
> # qemu-img create --object secret,data=123456,id=sec0 \
> -f qcow2 -o encryption-format=luks,luks-key-secret=sec0 \
> test.qcow2 10G
>
> results in the creation of an image using the LUKS format.
> Use of the legacy 'encryption=on' parameter still results
> in creation of the old qcow2 AES format, and is equivalent
> to the new 'encryption-format=aes'. e.g. the following are
> equivalent:
>
> # qemu-img create --object secret,data=123456,id=sec0 \
> -f qcow2 -o encryption=on,aes-key-secret=sec0 \
> test.qcow2 10G
>
> # qemu-img create --object secret,data=123456,id=sec0 \
> -f qcow2 -o encryption-format=aes,aes-key-secret=sec0 \
> test.qcow2 10G
>
> With the LUKS format it is necessary to store the LUKS
> partition header and key material in the QCow2 file. This
> data can be many MB in size, so cannot go into the QCow2
> header region directly. Thus the spec defines a FDE
> (Full Disk Encryption) header extension that specifies
> the offset of a set of clusters to hold the FDE headers,
> as well as the length of that region. The LUKS header is
> thus stored in these extra allocated clusters before the
> main image payload.
>
> Aside from all the cryptographic differences implied by
> use of the LUKS format, there is one further key difference
> between the use of legacy AES and LUKS encryption in qcow2.
> For LUKS, the initialiazation vectors are generated using
> the host physical sector as the input, rather than the
> guest virtual sector. This guarantees unique initialization
> vectors for all sectors when qcow2 internal snapshots are
> used, thus giving stronger protection against watermarking
> attacks.
>
> Signed-off-by: Daniel P. Berrange <address@hidden>
> ---
> block/qcow2-cluster.c | 4 +-
> block/qcow2-refcount.c | 10 ++
> block/qcow2.c | 284
> +++++++++++++++++++++++++++++++++++++++------
> block/qcow2.h | 9 ++
> include/block/block_int.h | 1 +
> qapi/block-core.json | 11 +-
> qemu-img.c | 4 +-
> tests/qemu-iotests/082.out | 270 +++++++++++++++++++++++++++++++++++++-----
> 8 files changed, 527 insertions(+), 66 deletions(-)
>
[...]
> diff --git a/qapi/block-core.json b/qapi/block-core.json
> index 4943942..d15c6a9 100644
> --- a/qapi/block-core.json
> +++ b/qapi/block-core.json
> @@ -2327,9 +2327,15 @@
> # caches. The interval is in seconds. The default
> value
> # is 0 and it disables this feature (since 2.5)
> # @aes-key-secret: #optional the ID of a QCryptoSecret object
> providing
> -# the AES decryption key (since 2.9). Mandatory for
> +# the AES decryption key (since 2.9). Mandatory for
> AES
> # encrypted images, except when doing a metadata-only
> # probe of the image.
> +# the AES decryption key (since 2.9) Mandatory except
> +# when doing a metadata-only probe of the image.
I think these two lines should be omitted (rebase artifact?).
With that fixed:
Reviewed-by: Max Reitz <address@hidden>
> +# @luks-key-secret: #optional the ID of a QCryptoSecret object
> providing
> +# the LUKS keyslot passphrase (since 2.9). Mandatory
> for
> +# LUKS encrypted images, except when doing a
> metadata-
> +# only probe of the image.
> #
> # Since: 1.7
> ##
[...]
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