gcp compute exec uses user from ssh config file

[ekinanp]

My SSH config file has a Host * line that sets the default user to root. GCP compute exec uses the user parsed from the GCE SSH files (see https://github.com/puppetlabs/wash/blob/master/plugin/gcp/computeInst.go#L113) and sets that user as the FallbackUser. Thus, the SSH transport will use the root user when SSH'ing into the instance (b/c it reads from ~/.ssh/config via https://github.com/puppetlabs/wash/blob/master/transport/ssh.go#L66-L69) instead of the user parsed from my GCE SSH files. Thus, Exec fails because I'm ssh'ing as the wrong user.

I'm filing this issue because exec works fine when I do gcloud ssh, meaning GCP probably doesn't read the ~/.ssh/config file for extra info. That means we probably shouldn't either.

WORKAROUND: Just make sure you don't have any Host matchers that can conflict with a GCP compute instance's host name. So for me that means removing the Host * matcher or changing it to something else like foo.

[ekinanp]

I wonder why we're setting the parsed user as FallbackUser instead of User? See https://github.com/puppetlabs/wash/blob/master/plugin/gcp/computeInst.go#L137

[MikaelSmith]

That does seem like a mistake, I don't have a reason for FallbackUser over User there.

[MikaelSmith]

I think my original thinking was that you could use ~/.ssh/config to change the user, because we don't provide a CLI option for that with wexec. But we should also behave consistently with gcloud ssh, so I'm fine changing it to fix this.