Re: [squid-users] Questions on research into using digest auth against MS AD2003

On lör, 2008-11-01 at 19:49 -0700, Chuck Kollars wrote:

> "One-time" generally refers to the 'nonce' (and 'cnonce') used by
> challenge-response authentication protocols. But verifying the
> nonce-hashed-by-password would require using the actual original
> cleartext password, something proxies don't have (and can't obtain
> reliably yet securely).

Digest authentication is one-time as it is dependent on the unique to
server nounce which never repeats.

Verifying the Digest response requires access to H(A1), not neccesarily
the plain-text password. The H(A1) hash is static until the user changes
his password, and is the secret keying material used by Digest
authentication.

> So proxies like Squid instead use the H{username:realm:password} field
> (which was originally intended for use mainly for identification).
> Most importantly this H(A1) field that Squid uses is the same every
> time (since Squid is always in the same 'realm'); it's *not*
> "one-time" in the sense of never ever repeating.

Yes, but it's only exchanged between Squid and the user directory, not
between client and Squid. Between client and Squid there is one-time
hashes influenced by both server (squid) and client (browser) nounces
and the specific request (method and URI).

Regards
Henrik