[jdev] Re: [xmppwg] Incorrect SASL Digest MD5 example in XMPP Core

Peter Saint-Andre stpeter at jabber.org
Mon Oct 24 17:38:34 CDT 2005


Thanks for the error report, we will definitely fix this in rfc3920bis 
and I will look into having the IETF also publish an erratum as well.

Peter

Ralph Meijer wrote:
> Hi all,
> 
> While attempting to implement SASL authentication in Twisted, I
> discovered a discrepancy between RFC 2831 (Using Digest Authentication
> as a SASL Mechanism) and the examples 6.5 and 6.6 in RFC 3920 (XMPP
> Core) that do DIGEST-MD5 SASL authentication.
> 
> The discrepancy is about Step 3 (section 2.1.3) of RFC 2831. After
> the server having sent a challenge in Step 1 and the client sending a response
> in Step 2, Step 3 is the server checking this response and sending an
> 'rspauth'. This is not a challenge, but extra information for subsequent
> authorization, sent along with the affirmation of a succesful authentication.
> 
> The ACAP example in section 4 of RFC 2831 shows this. However, the IMAP
> example needs an extra roundtrip because there is no way in IMAP to do
> both an 'OK' and send along this rspauth information. Probably the IMAP
> example was taken to erroneously craft the example in XMPP Core.
> 
> Peter Saint-Andre made mention of this error in the notes for
> RFC3920bis. You can find that here:
> http://www.xmpp.org/xmppbis.html#sasl.  For the correct authentication
> sequence of example 6.5, step 7 is changed and steps 8 and 9 removed:
> 
>   Step 7: Server informs client of successful authentication and sends
>   the [BASE64] encoded value for subsequent authentication to client:
> 
>   <success xmlns='urn:ietf:params:xml:ns:xmpp-sasl'>
>   cnNwYXV0aD1lYTQwZjYwMzM1YzQyN2I1NTI3Yjg0ZGJhYmNkZmZmZAo=
>   </success>
> 
>   The decoded value for subsequent authentication is:
> 
>   rspauth=ea40f60335c427b5527b84dbabcdfffd
> 



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