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Re: [Qemu-block] [PATCH v4 12/18] qcow2: extend specification to cover L

From: Alberto Garcia
Subject: Re: [Qemu-block] [PATCH v4 12/18] qcow2: extend specification to cover LUKS encryption
Date: Wed, 15 Feb 2017 16:18:37 +0100
User-agent: Notmuch/0.18.2 (http://notmuchmail.org) Emacs/24.4.1 (i586-pc-linux-gnu)

On Fri 10 Feb 2017 06:09:04 PM CET, Daniel P. Berrange wrote:
> Update the qcow2 specification to describe how the LUKS header is
> placed inside a qcow2 file, when using LUKS encryption for the
> qcow2 payload instead of the legacy AES-CBC encryption
> Reviewed-by: Max Reitz <address@hidden>
> Signed-off-by: Daniel P. Berrange <address@hidden>

> +    Byte  0 -  7:   Offset into the image file at which the encryption
> +                    header starts in bytes. Must be aligned to a cluster
> +                 boundary.
> +    Byte  8 - 15:   Length of the written encryption header in bytes.
> +                    Note actual space allocated in the qcow2 file may
> +                 be larger than this value, since it will be rounded
> +                 to the nearest multiple of the cluster size. Any
> +                 unused bytes in the allocated space will be initialized
> +                 to 0.

You are using tabs instead of spaces in these paragraphs. Those are the
only tabs in the whole file so you probably want to change them.

> +In the LUKS partition header, the "payload-offset" field will be
> +calculated as normal for the LUKS spec. ie the size of the LUKS
> +header, plus key material regions, plus padding. Its value is not
> +used, however, since the qcow2 file format itself defines where
> +the real payload offset is.

If I understand this, the value of payload-offset is not used but it
must be correct.

Is payload-offset also relative to the start of the LUKS header? I
assume that it is, but maybe it can be clarified like you did with

> +In the LUKS key slots header, the "key-material-offset" is relative
> +to the start of the LUKS header clusters in the qcow2 container,
> +not the start of the qcow2 file.


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