openssh unix dev - Sep 2024 - ssh while ssh-agent is running

Hi,
I run into a certain problem from time to time.

1. Configure and launch ssh-agent.
2. That's usually perfect.
3. Occasionally, connect to a different and less common remote server.
 Use ssh -i keyfile
4. ssh -i keyfile fails.  Because ssh-agent doesn't know about that key.

If you are specifying a key "-i key", then you are specifying a key,
and
clearly don't need to use the keys from ssh-agent. Could ssh prefer the key
from the command line? Give that precedence, over using the ssh-agent keys?
Many executables make choices based on multiple input parameters, with
information from the command-line having the top priority.
What is your opinion?

Thanks,
Sam

Hi Sam,

On Mon, Sep 30, 2024 at 11:37:18 -0600, Sam Darwin
wrote:
> If you are specifying a key "-i key", then you are specifying a
key, and
> clearly don't need to use the keys from ssh-agent.
The -i option is dual-use. From the man page:
> Selects a file from which the identity (private key) for public key
authentication is read.
> You can also specify a public key file to use the corresponding
> private key that is loaded in ssh-agent(1) when the private key file
> is not present locally.
I think you can also load certificates using the -i option and use the
agent to generate the signature.
> Could ssh prefer the key from the command line? Give that precedence,
> over using the ssh-agent keys?
The IdentitiesOnly option takes care of that. Or you could set up
your ~/.ssh/config file with IdentitiesOnly + IdentityFile to specify
the correct key for each server.


J?rn

On Mon, 30 Sep 2024, Sam Darwin wrote:
> Hi,
> I run into a certain problem from time to time.
> 
> 1. Configure and launch ssh-agent.
> 2. That's usually perfect.
> 3. Occasionally, connect to a different and less common remote server.
>  Use ssh -i keyfile
> 4. ssh -i keyfile fails.  Because ssh-agent doesn't know about that
key.
> 
> If you are specifying a key "-i key", then you are specifying a
key, and
> clearly don't need to use the keys from ssh-agent. Could ssh prefer the
key
> from the command line? Give that precedence, over using the ssh-agent keys?
ssh should do this already. Please post a debug trace "ssh -vvv ..."
and we'll be able to see what broke.