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Interpreting “a previously-unrecognized weakness in X was just found” as “X just got weaker” is dangerously bad tech writing.
ChaCha20-Poly1305 and CBC with Encrypt-then-MAC ciphers are vulnerable to a MITM attack.
Saved you a click.
I thought most SSH servers default to some AES-based cypher like most other programs. Is that not the case?
Even the researcher who reported this doesn’t go as far as this headline.
“I am an admin, should I drop everything and fix this?”
Probably not.
The attack requires an active Man-in-the-Middle attacker that can intercept and modify the connection’s traffic at the TCP/IP layer. Additionally, we require the negotiation of either ChaCha20-Poly1305, or any CBC cipher in combination with Encrypt-then-MAC as the connection’s encryption mode.
[…]
“So how practical is the attack?”
The Terrapin attack requires an active Man-in-the-Middle attacker, that means some way for an attacker to intercept and modify the data sent from the client or server to the remote peer. This is difficult on the Internet, but can be a plausible attacker model on the local network.
If someone can gain physical access to your network, you’re already fucked.
Yeah, if the attacker is in a position to do a MitM attack you have much larger problems than a ssh vulnerability that so far can at most downgrade the encryption of your connection in nearly all cases
So you need an MitM situation to even be able to perfom the attack, and the the attack on works on two ciphers? The article says those ciphers are commonly enabled, but are they default or used in relatively modern distributed versions of openssh?
A scan performed by the researchers found that 77 percent of SSH servers exposed to the Internet support at least one of the vulnerable encryption modes, while 57 percent of them list a vulnerable encryption mode as the preferred choice.
That means a client could negotiate one or the other on more than half of all internets exposed openssh daemons.
I haven’t got too whizzed up over this, yet, because I have no ssh daemons exposed without a VPN outer wrapper. However it does look nasty.
If you need a man in the middle to exploit this, it’s not that nasty.
Great photo illustration
