Neat idea, but I think there's a confused deputy(?) attack possible here. Specifically, I think there's a missing binding between the SSH session used for auth

Neat idea, but I think there's a confused deputy(?) attack possible here. Specifically, I think there's a missing binding between the SSH session used for authentication and a user's web session. Let's say that Alice has an account on bob.com. Mallory sets up mallory.net and sets up demo-ssh.mallory.net as a DNS alias (or TCP proxy) pointing to demo-ssh.bob.com. 1. Alice visits mallory.net, which Mallory controls 2. Mallory visits bob.com and starts an authentication session. 3. bob.com presents an SSH challenge to Mallory ssh demo-ssh.bob.com -l 7d7662f63f70de7714 -p 2222 4. Mallory forwards the challenge from bob.com to Alice, optionally substituting their own hostname: ssh demo-ssh.mallory.net -l 7d7662f63f70de7714 -p 2222 5. Alice runs the command to authenticate to "demo-ssh.mallory.net". But this actually authenticates Mallory as Alice to bob.com! 6. Upon detecting a successful login, mallory.net accepts Alice's login to avoid raising suspicion. The only sure sign that this has happened would be that demo-ssh.bob.com and demo-ssh.mallory.net would have the same host keys, but OpenSSH isn't designed to prohibit duplicate host keys.