Re:35-year-old vulnerability discovered in scp
by fwip on Tuesday January 15, 2019 @09:34PM
(#18917822)
Okay, swap Bob and Eve then.
Re:35-year-old vulnerability discovered in scp
by Dylan16807 on Tuesday January 15, 2019 @11:16PM
(#18918190)
Okay. "The attack is on Alice, who thinks she's connecting to Eve, but is actually connecting to Bob. Assuming Alice doesn't check the host fingerprint (which nobody does), the attack succeeds."
You're fundamentally misunderstanding the argument about which key is being copied. It's Alice's public key that's copied. The fake server generates its own public and private keys and nobody notices that it doesn't match the real server. The user won't be "prompted to cancel" when this is their first time connecting.
authorized_hosts, as typically used, prevents an imposter from showing up later. It does absolutely nothing to prevent an imposter that's there from the start.
The attack is on Alice, who thinks she's connecting to Bob, but is actually connecting to Eve. This is on initial connect, and assuming Alice doesn't check the host fingerprint (which nobody does; that's the crux of my point).
This nomenclature is the convention when discussing cryptographic attacks: https://en.wikipedia.org/wiki/Alice_and_Bob
I'm going to stop discussing this in this thread, but feel free to contact me (info in profile). I promise to engage, in good faith, and if you do end up convincing me, I'll post an update here.
Best wishes.