Re: [Qemu-devel] [PATCH 1/3] qapi-schema: Make @password in set_password optional

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

On Tue, Feb 17, 2015 at 05:40:45PM +0100, Michal Privoznik wrote:
> So, imagine you've started a guest with ticketing enabled. You've set
> some password to access your SPICE/VNC session. However, later you
> want to give the access to somebody else's and therefore disable the
> ticketing. Come on, be imaginative! Currently, there's no way how to
> achieve this. And while there are two possible ways to fulfill the
> goal: 1) invent new monitor command to disable ticketing, or 2) let
> @password argument to 'set_password' monitor command be optional, I'm
> choosing the latter. It's easier to implement, after all.
> 
> The idea behind, how this will work, is: if user issues the command
> without the password field, it means they want to disable the
> ticketing. Any subsequent call to the call with password field filled
> in, will enable the ticketing again.

When password auth is enabled with VNC, the use of a NULL / empty string
password is explicitly intended to block access to the VNC server, by
causing the password auth to always return failure. Overloading the
'set_password' command such that a missing password changes the auth
scheme in use is a really surprising and bad side effect.

If we want to have the ability to change the authentication protocol
used for VNC/SPICE, then lets add a proper command for this. ie
create a 'set_graphics_auth' command to change auth protocol. This
is really better for VNC anyway, as there are far more possible auth
schemes than just password or no-password, and overloading the
'set_password' command can't handle that.

Regards,
Daniel
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