[Qemu-devel] [PATCH] vnc: Clarify documentation of QMP command change

[Qemu-devel] [PATCH] vnc: Clarify documentation of QMP command change

[Markus Armbruster]

QMP command

    { "execute": "change",
      "arguments": { "device": "vnc", "target": "password", "arg": PWD } }

behaves just like

    { "execute": "change-vnc-password",
      "arguments": { "password", "arg": PWD } }

Their documentation differs, however.  According to
change-vnc-password's documentation, "an empty password [...] will set
the password to the empty string", while change's documentation claims
"no future logins will be allowed".  The former is actually correct.
Replace the incorrect claim by a reference to change-vnc-password.

Signed-off-by: Markus Armbruster <armbru@redhat.com>
---
 qapi-schema.json | 3 +--
 1 file changed, 1 insertion(+), 2 deletions(-)

diff --git a/qapi-schema.json b/qapi-schema.json
index 8b015be..58d3a02 100644
--- a/qapi-schema.json
+++ b/qapi-schema.json
@@ -3011,8 +3011,7 @@
 # @arg:    If @device is a block device, then this is an optional format to open
 #          the device with.
 #          If @device is 'vnc' and @target is 'password', this is the new VNC
-#          password to set.  If this argument is an empty string, then no future
-#          logins will be allowed.
+#          password to set.  See change-vnc-password for additional notes.
 #
 # Returns: Nothing on success.
 #          If @device is not a valid block device, DeviceNotFound
-- 
2.7.5

Re: [Qemu-devel] [PATCH] vnc: Clarify documentation of QMP command change

[Marc-André Lureau]

Hi

On Wed, Jul 19, 2017 at 9:09 AM, Markus Armbruster <armbru@redhat.com> wrote:
> QMP command
>
>     { "execute": "change",
>       "arguments": { "device": "vnc", "target": "password", "arg": PWD } }
>
> behaves just like
>
>     { "execute": "change-vnc-password",
>       "arguments": { "password", "arg": PWD } }
>
> Their documentation differs, however.  According to
> change-vnc-password's documentation, "an empty password [...] will set
> the password to the empty string", while change's documentation claims
> "no future logins will be allowed".  The former is actually correct.
> Replace the incorrect claim by a reference to change-vnc-password.
>
> Signed-off-by: Markus Armbruster <armbru@redhat.com>

Reviewed-by: Marc-André Lureau <marcandre.lureau@redhat.com>


The password would have to be NULL to disallow further login, is that
what your other series will allow to do?

> ---
>  qapi-schema.json | 3 +--
>  1 file changed, 1 insertion(+), 2 deletions(-)
>
> diff --git a/qapi-schema.json b/qapi-schema.json
> index 8b015be..58d3a02 100644
> --- a/qapi-schema.json
> +++ b/qapi-schema.json
> @@ -3011,8 +3011,7 @@
>  # @arg:    If @device is a block device, then this is an optional format to open
>  #          the device with.
>  #          If @device is 'vnc' and @target is 'password', this is the new VNC
> -#          password to set.  If this argument is an empty string, then no future
> -#          logins will be allowed.
> +#          password to set.  See change-vnc-password for additional notes.
>  #
>  # Returns: Nothing on success.
>  #          If @device is not a valid block device, DeviceNotFound
> --
> 2.7.5
>
>



-- 
Marc-André Lureau

Re: [Qemu-devel] [PATCH] vnc: Clarify documentation of QMP command change

[Markus Armbruster]

Marc-André Lureau <marcandre.lureau@gmail.com> writes:

> Hi
>
> On Wed, Jul 19, 2017 at 9:09 AM, Markus Armbruster <armbru@redhat.com> wrote:
>> QMP command
>>
>>     { "execute": "change",
>>       "arguments": { "device": "vnc", "target": "password", "arg": PWD } }
>>
>> behaves just like
>>
>>     { "execute": "change-vnc-password",
>>       "arguments": { "password", "arg": PWD } }
>>
>> Their documentation differs, however.  According to
>> change-vnc-password's documentation, "an empty password [...] will set
>> the password to the empty string", while change's documentation claims
>> "no future logins will be allowed".  The former is actually correct.
>> Replace the incorrect claim by a reference to change-vnc-password.
>>
>> Signed-off-by: Markus Armbruster <armbru@redhat.com>
>
> Reviewed-by: Marc-André Lureau <marcandre.lureau@redhat.com>
>
>
> The password would have to be NULL to disallow further login, is that
> what your other series will allow to do?

I guess it could be applied to change-vnc-password that way.

Re: [Qemu-devel] [PATCH] vnc: Clarify documentation of QMP command change

[Markus Armbruster]

Markus Armbruster <armbru@redhat.com> writes:

> Marc-André Lureau <marcandre.lureau@gmail.com> writes:
>
>> Hi
>>
>> On Wed, Jul 19, 2017 at 9:09 AM, Markus Armbruster <armbru@redhat.com> wrote:
>>> QMP command
>>>
>>>     { "execute": "change",
>>>       "arguments": { "device": "vnc", "target": "password", "arg": PWD } }
>>>
>>> behaves just like
>>>
>>>     { "execute": "change-vnc-password",
>>>       "arguments": { "password", "arg": PWD } }

This should be

          "arguments": { "password": PWD } }

>>> Their documentation differs, however.  According to
>>> change-vnc-password's documentation, "an empty password [...] will set
>>> the password to the empty string", while change's documentation claims
>>> "no future logins will be allowed".  The former is actually correct.
>>> Replace the incorrect claim by a reference to change-vnc-password.
>>>
>>> Signed-off-by: Markus Armbruster <armbru@redhat.com>
>>
>> Reviewed-by: Marc-André Lureau <marcandre.lureau@redhat.com>
>>
>>
>> The password would have to be NULL to disallow further login, is that
>> what your other series will allow to do?
>
> I guess it could be applied to change-vnc-password that way.

However, making @password optional would be even simpler.  Absent
@password = no password feels natural to me.

Re: [Qemu-devel] [PATCH] vnc: Clarify documentation of QMP command change

[Eric Blake]

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On 07/19/2017 07:10 AM, Markus Armbruster wrote:
> Marc-André Lureau <marcandre.lureau@gmail.com> writes:
> 
>> Hi
>>
>> On Wed, Jul 19, 2017 at 9:09 AM, Markus Armbruster <armbru@redhat.com> wrote:
>>> QMP command
>>>
>>>     { "execute": "change",
>>>       "arguments": { "device": "vnc", "target": "password", "arg": PWD } }
>>>
>>> behaves just like
>>>
>>>     { "execute": "change-vnc-password",
>>>       "arguments": { "password", "arg": PWD } }
>>>
>>> Their documentation differs, however.  According to
>>> change-vnc-password's documentation, "an empty password [...] will set
>>> the password to the empty string", while change's documentation claims
>>> "no future logins will be allowed".  The former is actually correct.
>>> Replace the incorrect claim by a reference to change-vnc-password.
>>>
>>> Signed-off-by: Markus Armbruster <armbru@redhat.com>
>>
>> Reviewed-by: Marc-André Lureau <marcandre.lureau@redhat.com>
>>
>>
>> The password would have to be NULL to disallow further login, is that
>> what your other series will allow to do?
> 
> I guess it could be applied to change-vnc-password that way.

Ideally, 'change' will be deprecated (and certainly we shouldn't add
anything further to it), but yes, 'change-vnc-password' could be
enhanced in 2.11 to use the StrOrNull alternate to use null as the
request for no password (since the empty string "" _is_ hashable as a
password, whether or not we currently allow it to be one).

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


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Re: [Qemu-devel] [PATCH] vnc: Clarify documentation of QMP command change

[Gerd Hoffmann]

  Hi,

> The password would have to be NULL to disallow further login, is that
> what your other series will allow to do?

Disallow logins can be done using "expire-password vnc now".

I think having multiple ways to archive the same thing is a bad idea
from a security point of view, so I'd suggest to not touch the behavior
of the various set-password command variants.

cheers,
  Gerd

Re: [Qemu-devel] [PATCH] vnc: Clarify documentation of QMP command change

[Markus Armbruster]

Gerd Hoffmann <kraxel@redhat.com> writes:

>   Hi,
>
>> The password would have to be NULL to disallow further login, is that
>> what your other series will allow to do?
>
> Disallow logins can be done using "expire-password vnc now".
>
> I think having multiple ways to archive the same thing is a bad idea
> from a security point of view, so I'd suggest to not touch the behavior
> of the various set-password command variants.

Makes sense.