[Standards] LAST CALL: XEP-0280 (Message Carbons)

Vladimir me at boku.ru
Sun Feb 11 14:27:38 UTC 2018

Not 100% sure if relevant, but I'll remind of my request for
clarification I've posted here just in case:

As far as I can see, nothing in the XEP prohibits carbons from being
generated by outside sources (granted that other conditions are
satisifed). Carbons can only be sent from the user's bare JID, but the
transport can use XEP-0356 <privilege> to impersonate the user and
satisfy this condition.

    <message from=transport to=server type=chat
...><privilege><forwarded><message from=user at server
to=user at server/resource ...><sent><forwarded> ...

I had assumed servers would just ignore these already-carbons send
through them, but some actually produce carbons of these carbons. And it
is their opinion that XEP-0280 in its present form instructs them to
handle it like this.

The XEP never says anything about this particular case, but it says
servers "SHOULD follow the general intent". So apparently people can
have a different understanding of the general intent, in this case.

So shouldn't it be clarified? Either

* the server must not produce carbons of already-carbons, no matter the

* the server should produce carbons of already-carbons, if those are not
generated by the server itself

* the server should not accept carbons other than those generated by the
server itself (not that this is different from simply requiring sender
JID to be correct, as you can impersonate server users legally)

Or is the official stance on this is that

* the server may or may not produce carbons-of-carbons, both options are
valid per this XEP intent?

Note that for my particular use case (which I've posted to this list
earlier) people here have suggested creating a XEP to negotiate sending
external carbons with the server. This is a good idea, but even without
that, my point is that in its present form doing what I'm doing seems to
be valid per these XEPs, so shouldn't there be some official guideline
for this case?


On 08.02.2018 19:21, Jonas Wielicki (XSF Editor) wrote:
> This message constitutes notice of a Last Call for comments on
> XEP-0280.
> Title: Message Carbons
> Abstract:
> In order to keep all IM clients for a user engaged in a conversation,
> outbound messages are carbon-copied to all interested resources.
> URL: https://xmpp.org/extensions/xep-0280.html
> This Last Call begins today and shall end at the close of business on
> 2018-02-22.
> Please consider the following questions during this Last Call and send
> your feedback to the standards at xmpp.org discussion list:
> 1. Is this specification needed to fill gaps in the XMPP protocol
> stack or to clarify an existing protocol?
> 2. Does the specification solve the problem stated in the introduction
> and requirements?
> 3. Do you plan to implement this specification in your code? If not,
> why not?
> 4. Do you have any security concerns related to this specification?
> 5. Is the specification accurate and clearly written?
> Your feedback is appreciated!
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