Subject: A different thought on saslprep

From: Paul Hoffman / IMC <[email-masked]>
Date: Mon, 12 Jan 2004 15:17:45 -0800

Greetings again. Sorry for coming in so late on this, but three 
issues were just pointed out to me about this document and I thought 
they might be worthy of discussion.

The first is an implementation issue. In order to use saslprep on the 
shared secret, the application needs to know the text encoding used 
to enter the shared secret. Until now, that has always been ASCII, so 
no big problem there. However, once we open up to the Unicode 
character set, we also open up to a zillion odd text encodings 
(UTF-8, BIG5, ISO 8859-7, ...). Is anyone worried that that programs 
will get the conversion from what the user entered for the shared 
secret into Unicode code points wrong?

The second is shared secrets that aren't text. Is the shared secret 
always text, or is there a pure binary form? If so, you can't 
saslprep the pure binary form. I'm assuming this is a non-issue, but 
I might have not found the right place in the SASL draft.

The second is a security consideration. Running saslprep over a 
shared secret reduces the entropy of the shared secret by eliminating 
some characters and mapping others. Not a big deal, but it does make 
an attacker's job easier.

--Paul Hoffman, Director
--Internet Mail Consortium