Re: [PATCH 02/13] qcrypto-luks: implement encryption key management

[Daniel P . Berrangé]

On Tue, Jan 21, 2020 at 03:13:01PM +0200, Maxim Levitsky wrote:
> On Tue, 2020-01-21 at 08:54 +0100, Markus Armbruster wrote:
> 
> <trimmed>
> 
> > > +##
> > > +# @LUKSKeyslotUpdate:
> > > +#
> > > +# @keyslot:         If specified, will update only keyslot with this 
> > > index
> > > +#
> > > +# @old-secret:      If specified, will only update keyslots that
> > > +#                   can be opened with password which is contained in
> > > +#                   QCryptoSecret with @old-secret ID
> > > +#
> > > +#                   If neither @keyslot nor @old-secret is specified,
> > > +#                   first empty keyslot is selected for the update
> > > +#
> > > +# @new-secret:      The ID of a QCryptoSecret object providing a new 
> > > decryption
> > > +#                   key to place in all matching keyslots.
> > > +#                   null/empty string erases all matching keyslots
> > 
> > I hate making the empty string do something completely different than a
> > non-empty string.
> > 
> > What about making @new-secret optional, and have absent @new-secret
> > erase?
> 
> I don't remember already why I and Keven Wolf decided to do this this way, 
> but I think that you are right here.
> I don't mind personally to do this this way.
> empty string though is my addition, since its not possible to pass null on 
> command line.

IIUC this a result of using  "StrOrNull" for this one field...


> > > +# Since: 5.0
> > > +##
> > > +{ 'struct': 'LUKSKeyslotUpdate',
> > > +  'data': {
> > > +           '*keyslot': 'int',
> > > +           '*old-secret': 'str',
> > > +           'new-secret' : 'StrOrNull',
> > > +           '*iter-time' : 'int' } }

It looks wierd here to be special casing "new-secret" to "StrOrNull"
instead of just marking it as an optional string field

   "*new-secret": "str"

which would be possible to use from the command line, as you simply
omit the field.

I guess the main danger here is that we're using this as a trigger
to erase keyslots. So simply omitting "new-secret" can result
in damage to the volume by accident which is not an attractive
mode. 


> > > +
> > > +##
> > > +# @QCryptoBlockAmendOptionsLUKS:
> > > +#
> > > +# The options that can be changed on existing luks encrypted device
> > > +# @keys:           list of keyslot updates to perform
> > > +#                  (updates are performed in order)
> > > +# @unlock-secret:  use this secret to retrieve the current master key
> > > +#                  if not given will use the same secret as one
> > 
> > "as the one"?
> Yea, this is wrong wording, I'll drop those words. Thanks.
> 
> > 
> > > +#                  that was used to open the image
> > > +#
> > > +# Since: 5.0
> > > +##
> > > +{ 'struct': 'QCryptoBlockAmendOptionsLUKS',
> > > +  'data' : {
> > > +            'keys': ['LUKSKeyslotUpdate'],
> > > +             '*unlock-secret' : 'str' } }
> > > +
> > >   
> > >   
> > >   ##
> > > @@ -324,4 +372,4 @@
> > >     'base': 'QCryptoBlockOptionsBase',
> > >     'discriminator': 'format',
> > >     'data': {
> > > -            } }
> > > +          'luks': 'QCryptoBlockAmendOptionsLUKS' } }
> 
> 
> Thanks for review,
>       Best regards,
>               Maxim Levitsky
> 

Regards,
Daniel
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