@Monal Do i understand it correctly that current design goal is to make it mandatory to support for server but optional for client? Eg server will always send it but if client is not supporting that it will just transparently pass it over (eg. without actually verifying the signature hash against sdp section)?
@Monal I think you don't understand what I'm saying. SASL SCRAM is not xmpp feature. It is industry standard protocol. It is used with variety of protocols like SMTP, IMAP, LDAP to name a few. And you now want to mandate all libs to support xmpp XEP? like really?
@Monal it's not about being "allowed" it's about having possibility. As mentioned early I'm working with dovecot backend. I have no means to inject custom attribute into its server-first. Similar is with other sasl libs i worked with.
@Monal this attribute must be sent by server, you cannot force arbitrary sasl backend to send custom attribute. You can send it from the client though as optional extension and any compliant backend should ignore it but include into authmessage (hence signature).
@sam legacy coding. like it was with infra, when cloud and software-defined-crap came, first it was deragatory "legacy", then after certain time became hybrid (in relation to cloud) and/or clasic (in relation to sd).
@Monal yup that is exactly what I meant, thanks for improving. I'm still working with my test cases to check ssdp by using sasl optional extensions. first indication is positive though, so once finished with draft implementation will send proposal to the list.
@GossiTheDog where I can find your CV?
@Monal yes, I was part of similar discussion some time ago on xmpp maillist but while i supported the idea it's better to send n when you don't have mechanism to agree on binding type and you suspect that type you support is unlikely to be supported by tge server it's better to send n, but if server is not sending any -PLUS - y for me is a must have. Perhaps I need to undust my xmpp maillist and start it over there.
@Monal ok so the idea behind such scrutinity for SCRAM is to avoid user having false perception of being secure by using more secure mech? But if client choses plain - he's on his own and accepts all the risks.
@Monal server can then extract this attribute and compare it with own signature. heck it can even strip it and replace with own signature - either way being part of ClientSignature and hence ClientProof its tampering will break the auth.
@Monal Second problem is 474 is intervening into SCRAM mech by forcing undeclared server message. THere is compliant way to do that - optional extensions. I.e. we can include client hash as optional SASL extension attribute:
y,,n=me,r=E3F76B57-CBDE-46A3-979A-F9B1660B0685,g=1B86B264-2A11-4DEF-92C7-6ED78DAFBC95,h=0a1b2c3d4e5f
and that would include it into client-first-bare and hence part of AuthMessage and thus ClientSignature. SASL backend will just ignore it's meaning but keep in AuthMessage
@Monal First problem i see is that monal is sending n,, - it does support PLUS, but server advertised it's not, so it should send y,, instead indicating it didn't see PLUS in adv. That would already allow raising a flag to the server which actually advertised PLUS. That wouldn't allow catching downgrade to SHA-1-PLUS but would prevent downgrade to non-cb SCRAM mech.
@Monal but the whole point was to allow monal to use server with dovecot sasl provider. apparently I cannot force Dovecot to add some extra field to the SASL challenge this effort is futile then ;(
@Monal Ok so only way to use SCRAM is to implement 388 and 474, while PLAIN could be used without all the hassles? like really? :)
@Monal Ok, added 0388 implementation, not advertising -PLUS, and getting now this:
_incomplete XEP-0388 support, XEP-0440 MUST be implemented and this mandates that servers MUST at least implement tls-server-end-point__
Ok, fair enough, if server sent PLUS, but it didn't
@mcSlibinas @GossiTheDog we will see in two weeks, maybe someone fells out maybe not. Of course FAKE NEWS are telling we are not doing anything about it.
@Monal yup got it so i need to use /authentication:urn:xmpp:sasl:2 in features instead of /mechanisms:urn:ietf:params:xml:ns:xmpp-sasl for it to accept scram.
@Monal I have a question, cannot find it in FAQ/mans. Is monal *only* supporting SASL SCRAM-SHA-*-PLUS now? I'm offering SCRAM-SHA-256 but it closes the stream and shows "weak auth" error. a bit odd and there's no setting to turn it off
@briankrebs narcissist of nth degree most likely is sociopath, but sociopath does not necessary is narcissist
Joined Nov 2019
