When you execute:
ssh -A -t firstname.lastname@example.org
you are establishing a session between
bar.com. From now on, everything you type within this session is interpreted by and executed on
Then you establish a session from
sls is not a standard command, but I assume it is a wrapper for another SSH connection).
You have a second session encrypted between
server. This session is authenticated with your private key which is stored on the
In the first command you have
-A argument which enables agent forwarding. This mechanism allows encrypting the session between
bar.com and the server, using the
desktop machine (and the private key stored there) for authentication.
It does not mean the second connection is encrypted end-to-end between
server, it just means
desktop authorised a session between
The situation cannot be likened to an attack, because you deliberately choose to use the feature for your own convenience and security (your private key does not leave your machine, you don't store another key with access to
bar.com, you don't have to type the password).
The functionality you were seemingly expecting is called tunneling or port forwarding (although must be configured separately). With this you establish two SSH sessions from
desktop first to
bar.com then another one to a different port of
bar.com which would be "bound" to port 22 of
server. In this scenario
bar.com would not have the ability to see "inside" the SSH session between