tunneling ssh authorization

Question

Do I need to have a private key on the interim server pc2?

I want to connect to pc3 through pc2 without any possibility for pc2 to intercept or forge traffic from pc1 to pc3. I am on pc1.

There is following configuation on pc1.

Host pc2
     HostName pc2
     User user2
     ProxyCommand ssh -W %h:%p user@pc3

How can I setup what public/private key pair will be used for pc3 when connecting to it through pc2?

Answer 1

Just set this in your ~/.ssh/config

Host *
  ForwardAgent yes

Most servers have AllowAgentForwarding on by default so it will automatically forward keys when possible.

Answer 2

The ssh -i option specifies the location of the identity file you want to use. The -A option forwards credentials, so loading the key you want into ssh-agent via ssh-add may also do what you want without having to explicity list a key in the config file.