Re: comments to draft-ietf-ldapbis-authmeth-04.txt

[Hallvard B Furuseth <h.b.furuseth@usit.uio.no>]

I'm still wondering about SASL/DIGEST-MD5...

In an old private mail to Roger Harrison, I wrote:

> [Under Security Considerations in Authmeth,]
> 
> Please mention (...) which mechanisms that are standardized by the
> LDAP standard do/do not disclose the user's password to the server?

Another thing which would be interesting to list is which methods
need/don't need the server to know the user's plaintext password.
(I say 'know' instead of 'store' because it could still store the
password encrypted, but in a way which it knows how to decrypt.)

The best, of course, should be a method which does not require the
server to know the password and does not disclose the password to the
user.  According to rfc2831 SASL/DIGEST-MD5 is such a mechanism, yet
Section 3.9 "Storing passwords" says:

   if this password file is compromised, then an attacker gains
   immediate access to documents on the server using this realm.

I don't see what 'files' means in LDAP context.  Does this mean that
if our system encrypts passwords and throws away the unencrypted ones,
we can't use SASL/DIGEST-MD5 since we must to know the plaintext
passwords and re-encrypt them if the password file is stolen?

If not - Section 3.9 says the stored passwords will be a hash of
username-value, realm-value, and passwd, and that the realm should
include the name of the host doing the authentication.  Will
'ldap.uio.no' do for host here, where that will be the DNS name of
_several_ hosts?

-- 
Hallvard