ssh key persists even after I delete the private key from ~/.ssh -- why?

I generated ssh keys (public and private) and stored them in ~/.ssh/myServer/.

I added the public key to the server's ~/.ssh/authorized_keys file and everything works great!

In my effort to try and understand how the keys work I deleted them and was surprised to find that I was still able to connect to the server.

Why is it that I am still able to connect without a password?

Solution 1:

Welcome to the wonderful world of OS X Keychain and ssh-agent! From the man page:

ssh-agent is a program to hold private keys used for public key authentication (RSA, DSA, ECDSA). The idea is that ssh-agent is started in the beginning of an X-session or a login session, and all other windows or programs are started as clients to the ssh-agent program. Through use of environment vari-ables variables ables the agent can be located and automatically used for authentication when logging in to other machines using ssh(1).

Your private key was cached in the agent and is being fetched from there to authenticate your session. OS X, via Keychain, does automatic ssh-agent caching for you because it's "user friendly". It can be a little alarming, but it's mostly a handy thing that this happens.

The default time-to-live for cached keys is forever. That's probably not a great default. It'll flush the cached keys on a logout/login-cycle or a reboot. Or you can force a flush by killing the current agent using:

ssh-add -D

You can list all credentials cached by the agent by running:

ssh-add -l

This will do the same but show the full public keys:

ssh-add -L