Re: [Qemu-devel] [PATCH v2 04/10] qapi: Formalize qcow2 encryption probing

[Eric Blake]

On 06/11/2018 03:51 PM, Max Reitz wrote:
> Currently, you can give no encryption format for a qcow2 file while
> still passing a key-secret.  That does not conform to the schema, so
> this patch changes the schema to allow it.
>
> Signed-off-by: Max Reitz <address@hidden>
> ---
>   qapi/block-core.json | 44 ++++++++++++++++++++++++++++++++++++++++----
>   block/qcow2.c        |  3 +++
>   2 files changed, 43 insertions(+), 4 deletions(-)

> +##
> +# @ImageInfoSpecificQCow2EncryptionNoInfo:
> +#
> +# Only used for the qcow2 encryption format "auto" in which the actual
> +# encryption format is determined from the image header.  Therefore,
> +# this encryption format will never be reported in
> +# ImageInfoSpecificQCow2Encryption.
> +#
> +# Since: 3.0
> +##
> +{ 'struct': 'ImageInfoSpecificQCow2EncryptionNoInfo',
> +  'data': { } }

Do we actually need this type, given Anton's work on making omitted 
branches automatically use an empty struct?

https://lists.gnu.org/archive/html/qemu-devel/2018-05/msg06836.html

> +
>   ##
>   # @ImageInfoSpecificQCow2Encryption:
>   #
> @@ -53,7 +66,8 @@
>     'base': 'ImageInfoSpecificQCow2EncryptionBase',
>     'discriminator': 'format',
>     'data': { 'aes': 'QCryptoBlockInfoQCow',
> -            'luks': 'QCryptoBlockInfoLUKS' } }
> +            'luks': 'QCryptoBlockInfoLUKS',
> +            'auto': 'ImageInfoSpecificQCow2EncryptionNoInfo' } }

If Anton's patches go in first, you don't even have to change this type;

>   
>   ##
>   # @ImageInfoSpecificQCow2:
> @@ -2658,10 +2672,30 @@
>   # @BlockdevQcow2EncryptionFormat:
>   # @aes: AES-CBC with plain64 initialization venctors
>   #
> +# @auto:            Determine the encryption format from the image
> +#                   header.  This only allows the use of the
> +#                   key-secret option.  (Since: 3.0)
> +#
>   # Since: 2.10
>   ##
>   { 'enum': 'BlockdevQcow2EncryptionFormat',
> -  'data': [ 'aes', 'luks' ] }
> +  'data': [ 'aes', 'luks', 'auto' ] }

the changed enum would be sufficient.

> +
> +##
> +# @BlockdevQcow2EncryptionSecret:
> +#
> +# Allows specifying a key-secret without specifying the exact
> +# encryption format, which is determined automatically from the image
> +# header.
> +#
> +# @key-secret:      The ID of a QCryptoSecret object providing the
> +#                   decryption key.  Mandatory except when probing
> +#                   image for metadata only.
> +#
> +# Since: 3.0
> +##
> +{ 'struct': 'BlockdevQcow2EncryptionSecret',
> +  'data': { '*key-secret': 'str' } }
>   
>   ##
>   # @BlockdevQcow2Encryption:
> @@ -2669,10 +2703,12 @@
>   # Since: 2.10
>   ##
>   { 'union': 'BlockdevQcow2Encryption',
> -  'base': { 'format': 'BlockdevQcow2EncryptionFormat' },
> +  'base': { '*format': 'BlockdevQcow2EncryptionFormat' },
>     'discriminator': 'format',
> +  'default-variant': 'auto',
>     'data': { 'aes': 'QCryptoBlockOptionsQCow',
> -            'luks': 'QCryptoBlockOptionsLUKS'} }
> +            'luks': 'QCryptoBlockOptionsLUKS',
> +            'auto': 'BlockdevQcow2EncryptionSecret' } }

This part is necessary, though, and looks correct.

--
Eric Blake, Principal Software Engineer
Red Hat, Inc.           +1-919-301-3266
Virtualization:  qemu.org | libvirt.org