Hello Dave,

I am happy to read you here :)

Recall, several months ago, I have asked you if your Openfire SASL2 PR will fix 
missing Channel Binding support in Openfire:
- https://github.com/igniterealtime/Openfire/pull/2795

The Openfire JIRA tickets are:
- https://igniterealtime.atlassian.net/browse/OF-2879
- https://igniterealtime.atlassian.net/browse/OF-2878
- https://igniterealtime.atlassian.net/browse/OF-2762
- https://igniterealtime.atlassian.net/browse/OF-2694

The Channel Binding support is requested by a lot of people since several years 
for security.

A lot of companies or projects use it, for example : Microsoft, PostgreSQL, ...

For the XMPP World, it is in RFC 6120 since March 2011 (15 years in few months):
- https://datatracker.ietf.org/doc/html/rfc6120

It is supported by other XMPP Servers: DJabberd, ejabberd (ProcessOne), Jackal 
IM, M-Link (Isode), Metronome IM, MongooseIM (Erlang Solutions), Prosody IM, 
Snikket, Tigase XMPP Server.
I do not specify the number of XMPP Clients and XMPP Libraries which support it 
too.

Regards,

BOCQUET Ludovic
________________________________________
From: Dave Cridland <[email protected]>
Sent: Wednesday, November 5, 2025 10:57 AM
To: XMPP Standards
Subject: [Standards] XEP-0440 No supported channel bindings

Thilo, sorry!

I had somehow missed that SASL2 mandates XEP-0440. It makes a lot of sense.

But...

Openfire currently doesn't support any channel bindings.

It is sometimes used in cases where there is no TLS at all. This is quite 
deliberate and sensible in this case, please don't argue with this! This means 
there will always be cases where there are no channel bindings available 
(because there's no channel to bind to!).

The schema doesn't include a minOccurs, and that means minOccurs='1' by 
default. This means at least one channel binding MUST be included. Is this 
intentional?

I appreciate this is an oddball case (and I can support tls-server-endpoint for 
most normal cases), but is this the intent here or was the expectation that the 
minOccurs should be '0'?

(I know tls-server-endpoint MUST be implemented, but MTI is not MTD etc).

Dave.
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