On 13/01/2025 12.50, Daniel Gultsch wrote:
This message constitutes notice of a Last Call for comments on XEP-0484.Title: Fast Authentication Streamlining Tokens Abstract: This specification defines a token-based method to streamline authentication in XMPP, allowing fully authenticated stream establishment within a single round-trip. URL: https://xmpp.org/extensions/xep-0484.html This Last Call begins today and shall end at the close of business on 2025-01-27. Please consider the following questions during this Last Call and send your feedback to the [email protected] discussion list: 1. Is this specification needed to fill gaps in the XMPP protocol stack or to clarify an existing protocol?
Yep.
2. Does the specification solve the problem stated in the introduction and requirements?
Si!
3. Do you plan to implement this specification in your code? If not, why not?
Unfortunately, the time I can dedicate to voluntary XMPP development has become scarce. I hope the situation will change again.
> 4. Do you have any security concerns related to this specification?The XEP states that the 'count' attribute protects against replay attacks if TLS' 0-RTT data is used. I am not sure if this is true. An attacker could take the original 0-RTT package from the wire and replay it against the server. How does 'count' help here?
What is essential is that 0-RTT data only contains the authentication data, but nothing more [1]. If it would contain, for example, also a correctly pipelined <message/>, then an attacker could potentially replay the 0-RTT data and cause the server to send the message.
Further remarks:Shouldn't token invalidation be possible without having to go through a SASL authentication? I am at a kiosk browser and hit the 'logout' button. Now the browser first has to disconnect and reconnect to invalidate the token?
Same for token rotation: what if a client has a long-lasting connection. Wouldn't it be good to be able to rotate the token without having to re-connect? Why not have the server simply push a new token to the client if the current one approaches its expiry date?
- Flow1: See also the relevant paragraph about 0-RTT in https://datatracker.ietf.org/doc/html/draft-schmaus-kitten-sasl-ht-10#name-initiator-first-message
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