- From: Dylan Barrell <dbarrell@opentext.com>
- Date: Tue, 16 Oct 2001 17:44:00 -0400
- To: "Lisa Dusseault" <lisa@xythos.com>
- Cc: "WebDAV" <w3c-dist-auth@w3.org>
Lisa, But the passwd is a portion of A1. So how is storing this different from storing the password? I am saying that neither basic nor digest is good enough - and so there is no added benefit of implementing digest when the real solution is transport layer security or some other authentication mechanism like kerberos. --Dylan > -----Original Message----- > From: Lisa Dusseault [mailto:lisa@xythos.com] > Sent: Tuesday, October 16, 2001 4:38 PM > To: Dylan Barrell > Cc: WebDAV > Subject: RE: Digest Authentication > > > Dylan, > > I'm not sure I understand your nonce issue. You do not need to store > the password on disk in the clear. In order to compute (or verify) the > the client's authenticator you need to have the value H(A1). For the > MD5 authentication scheme A1 is: > > A1 = unq(username-value) ":" unq(realm-value) ":" passwd > > (see RFC 2617 S 3.2.2.2). > > This is a fixed value for any user so it can be stored on disk > directly. > > There's no need to use a fixed nonce in order to use a fixed H(A1) > since the nonce is not an input to A1. > > Perhaps what you're referring to here is that compromise of H(A1) > on a given server allows the attacker to impersonate the user to > that server. However, this is not the same as compromise of the > password since it does not permit the attacker to impersonate the > user to any other server, even if the user has used the same password > on that user. > > Admittedly, this problem does not exist with basic auth. However, > most people consider sniffing a more serious threat than password > file theft, which is why DAV so strongly "encourages" digest. > > What threat model are you concerned with here? Would you be > implementing BASIC if you don't implement DIGEST, or is neither > good enough? What would be good enough? > > Lisa > > > -----Original Message----- > > From: w3c-dist-auth-request@w3.org > > [mailto:w3c-dist-auth-request@w3.org]On Behalf Of Dylan Barrell > > Sent: Tuesday, October 16, 2001 11:37 AM > > To: Dirk-Willem van Gulik > > Cc: WebDAV > > Subject: RE: Digest Authentication > > > > > > We did think of this solution, but that means that we always have > > to use the > > same nonce value and we end up getting no security improvement > over basic > > authentication - so the argument that it is more secure than > > basic is bogus > > if you do this. > > > > --Dylan > > > > > -----Original Message----- > > > From: Dirk-Willem van Gulik [mailto:dirkx@webweaving.org] > > > Sent: Tuesday, October 16, 2001 2:02 PM > > > To: Dylan Barrell > > > Cc: WebDAV > > > Subject: Re: Digest Authentication > > > > > > > > > > > > > > > On Tue, 16 Oct 2001, Dylan Barrell wrote: > > > > > > > Digest Authentication requires that a server store its > > > passwords in such a > > > > way that they be available in clear text format. > > > > > > Actually though your implementation -could- store the password > > on disk as > > > plain text - most do not; and it is technically not required. Some bad > > > implementations do store it plain - but (for example) the apache web > > > server stores the password as a hash (md5 or crypt) on the > server side. > > > > > > See http://cvs.apache.org -> apache-1.3 -> src/support/htpasswd.c and > > > src/support/htdigest.c to get an idea of the code). > > > > > > So it is not a requirement - just an implementation choise. > > > > > > It is true that with normal basic auth the password goes over > > the wire in > > > the clear; but with digest auth this is not the case. > > > > > > Dw
Received on Tuesday, 16 October 2001 17:45:51 UTC