I receive a
Could not open a connection to your authentication agent error message when I attempt to connect from an intermediate server to a third server using the agent forwarding option (
-A) of an OpenSSH client. The first connection to the intermediate server goes smoothly using a key loaded into
ssh-agent. The error message is displayed when attempting a connection to the final server.
My OpenSSH client is set to allow forwarding with
ForwardAgent yes in
~/.ssh/config, and the intermediate server has
AllowAgentForwarding yes in the daemon's configuration file. The client config is not overridden by a system level file.
I'm not using a terminal multiplexer in order to avoid an error stemming from environment variables not being set. To run the agent, I use
exec ssh-agent zsh and verify that both
SSH_AGENT_PID are present in the local environment. I use
ssh-add to add the private keys for the intermediate and final server, respectively; I verify they are added with
All servers are of a recent version (OpenSSH 5.3) and the client is OpenSSH 6.2.