Re: draft-ietf-sasl-rfc2222bis-02 comments

["Kurt D. Zeilenga" <Kurt@xxxxxxxxxxxx>]

At 04:52 AM 10/8/2003, Alexey Melnikov wrote:
>>>  In
>>>  order to avoid noninteroperability due to differing normalizations,
>>>  when a mechanism specifies that a string authentication identity or
>>>  password used as input to a cryptographic function (or used for
>>>  comparison) it SHOULD specify that the string first be prepared using
>>>  the "SASLPrep" profile [SASLPrep], of the "stringprep" algorithm
>>>  [StringPrep].  This should be done by both the client (upon getting
>>>  user input or retrieving a value from configuration) and by the
>>>  server (upon receiving the value from the client).
>>>   
>>
>>What's the point of this duplicate preparation?  Why not do it only
>>at the server side?
>> 
>Because if the client doesn't do that, the hash calculated on the server will not match the one calculated on the client. 

Alexey, the current text suggests that client (1) prep the
value before sending, the server then preps it (2) again
(before comparing it to the store value, which also should
be prep'ed (3) either before storing it or before each compare).

We need to REQUIRE that mechanisms specify how character strings
are to be prepared for comparison and RECOMMEND that they use
SASLprep for simple user names and passwords.

We should not suggest that mechanisms should do both (1) and
(2).  (1) and (3) OR (2) or (3) are sufficient to ensure
proper matching.

Kurt