On Mon, Apr 27, 2020 at 7:14 AM Michael Thomas <mike@mtcc.com> wrote:

On 4/26/20 8:39 PM, Matt Palmer wrote:

On Sun, Apr 26, 2020 at 05:10:56PM -0700, Michael Thomas wrote:

Which exactly zero deployment. And you need to store the plain-text password
on the server side. What could possibly go wrong?

But you said that *passwords on the wire* were the biggest problem.  Digest
auth solves that.  Also, you don't have to store the plain-text password.

Correct. You need only store the realm/user/password digest. The chief
problem with digest authentication is that the web site has no control
over the UI. Among the many issues, this makes it tricky to reliably
capture a digest in the first place without the server at least
briefly knowing the password. I don't know if webauthn corrects this
or makes similar blunders.

Webauthn corrects this by not using passwords at all. It uses public key crypto which has the nice property that the thing that the server remembers is, um, public. A compromise of public keys -- unlike unsalted password hashes in the LinkedIn case -- does no harm. That was the insight that Paul, Steven and I had with RFC 7486 back in 2012, as we mashed together two different ways going about that in our experimental rfc. 

I'll stand by my initial stance: passwords over the wire remain the largest security hole on the net because their reuse means you only have to target the weakest sites to harvest them. Worse, you can create an active attack to get people to just give you their passwords by setting up some interesting site that requires an account whose actual purpose is to harvest passwords. Digest does exactly nothing to deal with that problem.

Also, says wikipedia about digest:

Disadvantages[edit]

There are several drawbacks with digest access authentication:

• The website has no control over the user interface presented to the end user.
• Many of the security options in RFC 2617 are optional. If quality-of-protection (qop) is not specified by the server, the client will operate in a security-reduced legacy RFC 2069 mode
• Digest access authentication is vulnerable to a man-in-the-middle (MITM) attack. For example, a MITM attacker could tell clients to use basic access authentication or legacy RFC2069 digest access authentication mode. To extend this further, digest access authentication provides no mechanism for clients to verify the server's identity
• Some servers require passwords to be stored using reversible encryption. However, it is possible to instead store the digested value of the username, realm, and password^[5]
• It prevents the use of a strong password hash (such as bcrypt) when storing passwords (since either the password, or the digested username, realm and password must be recoverable)

So my memory doesn't seem to be completely wrong here. It's been ages since I've thought about digest.

I can't speak to Steven, Paul, the w3c or any other non-posters to
this thread that you wish to employ in an appeal to authority fallacy
but with due respect, I think you hold a myopic view of network
security. For better or worse, security is a zero-sum game. The budget
stays proportional to the value of the asset being protected. When you
spend it on low-impact improvements you don't have it for the many
improvements with a higher impact than whether a web site knows the
password you chose for that web site.

With webcrypto, you can do whatever you want these days, and use whatever UI you want. Webauthn is primarily about replacing user-facing passwords from what I can tell, but it seems like it was completely informed by crypto dongles and the business of selling them. While that might be fine for high value network equipment, etc, it adds a huge amount of complexity in what otherwise is a pretty straightforward use of public key cryptography: user enrolls their public key into the server auth backend (bound to some identity), you log in by the server sending you a nonce, etc which the browser signs with the corresponding public key which the server verifies. Done. Maybe I should do this again now that webcrypto is here instead of my janky javascript implementation. Trying to get webauthn to work with just local credentials was like pulling teeth and frighteningly complex for something that should be pretty straightforward. It would extremely disheartening if the best was the enemy of the good.

Mike