XMPP: Admin-in-the-middle

Re:XMPP: Admin-in-the-middle by rhn_mk1 on Thursday November 04, 2021 @05:52AM (#29105163)

> XMPP uses passwords for authentication, rather than phone numbers. Since the server needs to use the password to verify you are you, there should be no surprise that it is sent to the server when you create your account or change your password. Just like any website or service that utilizes passwords for authentication.

There are plenty of authentication protocols that don't send passwords in cleartext. WPA would be rather useless if that happened, for example. Granted, the server operator can impersonate anyone they want already, but password leaks are a thing.

Server-side contact handling is independent of end-to-end ecryption, and doesn't need to be plaintext either.

Pretty much the only excusable things here are what's related to IP.

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Re:XMPP: Admin-in-the-middle by MattJ100 on Thursday November 04, 2021 @06:29AM (#29105366)

I believe you're slightly misunderstanding the details here (no surprise, as the article is not clear). All modern XMPP servers store the password securely hashed, and during authentication only hashes are exchanged.

Your comparison to WPA isn't quite an analogy - in the case of WPA the access point has already selected the password for the network, only authentication is needed. For XMPP and other services, the user selects their own password. This step is where the password is sent (once) to the server, upon which it is hashed and stored. That step doesn't happen in WPA, however the owner of the access point does have to securely transmit the password to the clients somehow.

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Re:XMPP: Admin-in-the-middle by yosamino on Thursday November 04, 2021 @06:50AM (#29105488)

> All modern XMPP servers store the password securely hashed, and during authentication only hashes are exchanged.

Huh, I didn't realize that SCRAM is this widely supported https://xmpp.net/reports.php

Thanks for the hint!

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Re:XMPP: Admin-in-the-middle by rhn_mk1 on Thursday November 04, 2021 @08:21AM (#29106212)

I see the distinction, but when I use public key cryptography, the keys are not symmetrical, and the server never sees my secret.

Indeed it was my mistake when I searched for authentication mechanisms, which aren't concerned with the initial exchange.

Still, as a non-cryptographer, I have to wonder if it's possible to make a password work while using public key crptography. Perhaps the way SSH does it: use password to unlock the private key, but only send the public key?

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Re:XMPP: Admin-in-the-middle by megous on Thursday November 04, 2021 @08:27AM (#29106273)

Yes. You'd probably want to derive your private key from the password, so that you don't have to store anything and use this method portably on multiple computers. But there's no need to ever send a password to the server, even when setting/changing it.

In theory... I don't know if there's any established auth method like this, that would eg. generate ed25519 secret key from a password, and used pubkey from it to send to the server when creating account or changing passwords and server using some challenge response, to authenticate users.

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Re:XMPP: Admin-in-the-middle by infosechandbook on Thursday November 04, 2021 @08:45AM (#29106443)

> I believe you're slightly misunderstanding the details here (no surprise, as the article is not clear).

The article clearly mentions that passwords are sent in cleartext to the server when the user sets/changes their password. It even clarifies that SCAM-SHA-1 won't help as hashing happens after cleartext password can be logged.

> loglevel: 5 (or “debug”) logs every single message and all activities mentioned above plus passwords in cleartext. Some XMPP proponents insisted that this isn’t true as XMPP servers use SCRAM-SHA-1 for password hashing. However, it doesn’t matter whether you enable or disable server-side password hashing as clients send new/changed passwords to XMPP servers in cleartext. The server logs the cleartext password before hashing it.

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