Comment by jamespwilliams | Hacker News Reader

Comment by jamespwilliams | Hacker News Reader

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Digest auth itself isn't very good though really, even ignoring the obvious problems of not using HTTPS.

In the most secure configuration of digest auth, the server stores MD5(username:realm:password), and to authenticate, the server sends server_nonce, and the client sends back client_nonce and MD5(MD5(username:realm:password):server_nonce:client_nonce). The nonces are used to avoid a replay attack. The server MD5s its stored hash with server_nonce:client_nonce and checks if it matches against what the client sent.

But if those stored hashes get leaked, an attacker can use them to authenticate. You're in a better position than storing plaintext passwords, because the underlying cleartext probably won't be leaked (they're hashed with MD5, so it's not certain), so your users' credentials can't be used in future credential stuffing attacks, etc. But the attacker still has their credentials on your site.

In the other configurations of digest auth, the server ends up storing plaintext passwords (or reversably-encrypted passwords, which is just as bad).

See also https://en.wikipedia.org/wiki/Digest_access_authentication#D...

Using HTTPS + Basic Auth is far more secure, and (arguably) easier at this point.

> Using HTTPS + Basic Auth is far more secure, and (arguably) easier at this point.

Totally makes sense...

I don't understand your point, if the database is leaked the security is compromised... well yes red is red, and green is green and HTTPS improves NOTHING of that.

HTTPS is a huge waste of electricity.

A more frugal way of securing logins is to use this RFC: https://datatracker.ietf.org/doc/html/rfc2289

Registrations would need additional security but HTTPS with centralized root certificates is NOT one of them.

Do you agree that storing passwords in plain text is a problem?

My point is that storing passwords in a way compatible with using Digest authentication is essentially equivalent to storing your passwords in plain text, at least with respect to your own site’s authentication.

You don't store them as plain text, you store them as hashes.

And then you send a server salt/nonce and the browser hashes the plain text password with the salted hash in your database and then with the server salt/nonce.

Still HTTPS solves nothing of that.

I don't even know what Digest is... I'm talking this RFC:

https://datatracker.ietf.org/doc/html/rfc2289

You shouldn't store a password in plaintext in your database. So if your database is leaked, they don't have the user's actual passwords. But with the digest scheme, you can't store a hash of the digest, because if all you have is Hash2(Hash1(username:realm:password)) and the nonces, then you can't compute Hash1(Hash1(username:realm:password):server_nonce:client_nonce), assuming that Hash2 is irreversible, which you want it to be.

> Hash1(Hash1(username:realm:password):server_nonce:client_nonce)

client_nonce?

This is how the RFC works: Hash(Hash(username:password):server_nonce)

What is the difference between Hash1 and Hash2?

Hash(username:password) is what you store in the database != plain text.

Also what is realm?

> client_nonce?

Yes, the client also generates a nonce that is included in the digest. The full digest (according to RFC 2617) is (assuming qop is used):

request-digest = <"> < KD ( H(A1), unq(nonce-value) ":" nc-value ":" unq(cnonce-value) ":" unq(qop-value) ":" H(A2) ) <">

> What is the difference between Hash1 and Hash2?

Hash1 is the hash algorithm for the authorization digest, so MD5 or maybe SHA256 (although only firefox currently supports that). Hash2 is the hash algorithm (including salting) used on the server to hash the hash of the username password before storing in the database.

> Hash(username:password) is what you store in the database != plain text.

The password isn't plaintext, but if the Hash(username:password) is compromised that gives an attacker enough information to impersonate that user. The attacker can just use that `Hash(username:password)` to compute the digest, they don't need to know the original password.

Yes, again if the database is compromised, it's compromised... I don't understand why so many people keep mentioning that when HTTPS does not solve that either?!

If a database of passwords is compromised, but the passwords are properly hashed and salted (server-side, not client-side), then you would need a rainbow table for each salt in order to actually get something usable from the compromised data.

Ok, how does HTTPS help with that?

And who cares if you need a rainbow table?

> how does HTTPS help with that

Ignoring all the other benefits of HTTPS, it means you can securely transfer the password itself to the server, or a deterministic hash of the password which the server hashes again. Not to mention that you can use a stronger hashing algorithm, like bcrypt. There might be other ways to do this, but https is definitely the most practical.

> who cares if you need a rainbow table?

If the passwords are moderately strong and you are using a good hashing algorithm (that is salted), then creating a big enough rainbow table (or brute forcing) is intractable.

This is vulnerable to 2nd preimage attacks. As a rule of thumb, you should use HMAC whenever you are concatenating values.

Can you exaplin what a "2nd preimage attack" is and how HMAC solves it?

If it's an attack you can do after the database is compromised it's not very interesting, and if it's an attack you can do over the wire then you can just limit the number of login attempts per some duration no?

I can try to explain, but this answer on the theoretical computer science stackexchange does it much better: https://cstheory.stackexchange.com/a/591

There are numerous ways to accidentally introduce a weakness to 2nd preimage resistance. Using an HMAC is a way to “reset” the entropy of a hash key and eliminate any unwanted source of information leakage.

which is itself a problem with using the Digest method from RFC 2617

If the site isn't served over https why would you trust anything on it with sensetive info like passwords, personal info or payment details? if "HTTPS is a huge waste of electricity" can you please explain to me how to currently secure (in transit) user information entered on my site without it?

1st you shouldn't trust any site with anything.

BUT if you trust it with anything it's a password so that only you can prove that you are you. And then you use server side nonce hashing to ONLY compute that part securely wasting only the required cycles one each end to proove you are you period!

Then, if for some reason you need additional security on some ulterior action, say a payment, you just do the same trick again. That way you save your servers and the electricity grid from encrypting every meaningless cat picture in the world just because you are paranoid.

Electricity is not an energy source, we are going to pay a very high price for it soon. It's the most liquid energy form we have and therefor when oil becomes illiquid (both litteraly and economically because the quality of oil is degrading at a rapid pace) prices in electrons (which have no quality properties that differ) will explode!

Again read the RFC https://datatracker.ietf.org/doc/html/rfc2289, and think about where you want to spend you energy, more customers or less energy for your own kids.

> 1st you shouldn't trust any site with anything.

Okay, so your proposal is to never use any private info, anywhere, ever on the internet?

> Again read the RFC

Page 2 of that RFC says

> It does not prevent a network eavesdropper from gaining access to private information and does not provide protection against either "social engineering" or active attacks

How do you propose to prevent MITM attacks? How do you propose to be able to send private data to a server in a way that is readable by the server?

Nothing is private if you send it somewhere.

Embrace the chaos, hide in the noise and save energy!

> Nothing is private if you send it somewhere.

You've reduced your own argument to a non-answer.

Surely you understand that there are different types of "privacy":

  - things that only you know (that aren't sent anywhere and maybe even are encrypted at rest)
  - things that only a set of trusted parties are supposed to know

The latter is what HTTPS allows you to achieve, alongside making it so that there's no possibility of a "man in the middle", which could not only read the contents of your request, but also alter it (or do the same for the server side response). OTP, TOTP and JWT are lovely for authentication, but they do not address the above concerns, as pointed out by the poster that you're replying to, before discarding your own argument.

Suppose that you have no encryption but have the best authentication system in the world. What's to prevent some hacker from setting themselves up in the middle between you and the e-commerce site that you're on and messing with requests however they please, showing both you and the site what they want you to see? You tried to buy an HDD for 50$? They just bought themselves a laptop for 500$.

The fact that there's a very secure bit of information somewhere in the request does not protect you from the rest of JSON being changed to say whatever they want it to (unless you are signing the contents of every request, but at that point you're reinventing HTTPS in some capacity). Or even the fact that they could set themselves up in the middle, presenting themselves as you to the site and presenting themselves as the site to you, albeit with more effort.

Of course, an e-commerce site is a silly example, but what about you receiving a bill that tells you to send money to a different account than you should? What would your banking site look like without encryption? Is your suggestiong for no one to do online banking because "nothing is private", even though we already have HTTPS which addresses this very issue ALONGSIDE various authentication methods?

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