sudo environment purging and OpenSSH

I recommend using sudo for privileged access to systems. I also recommend requiring keys for SSH authentication, with agent forwarding to trusted systems. The default settings in these two programs collide head-on when you become superuser via sudo and want to copy files from one server to another with scp or sftp.

If you're using an SSH agent, your environment contains the location of your authentication socket.

# env | grep SSH
SSH_CLIENT=192.0.2.2 51502 22
SSH_CONNECTION=192.0.2.2 51502...