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> I use an authorized_keys entry on the host that restricts the guest to running a specific command, which limits what a compromised guest can do to the host. T

> I use an authorized_keys entry on the host that restricts the guest to running a specific command, which limits what a compromised guest can do to the host. The command is set to a script that has a list of specific permitted actions. That’s a neat trick, thanks for mentioning this. command="command" ssh-ed25519 ... would be the authorized_keys entry and I’m guessing the script would read the SSH_ORIGINAL_COMMAND environment variable to determine which action was intended.

nneonneo 2y ago
Yes, that's exactly it. My authorized_keys line looks like this: command="${HOME}/bin/fromvm vmname",no-port-forwarding,no-x11-forwarding,no-agent-forwarding ssh-ed25519 ... I give each of my VMs a different name and key, which lets me identify them for the purpose of e.g. constructing ssh:// links for remote editing. The actual script uses $SSH_ORIGINAL_COMMAND, exactly as you've described, which means that while the guest thinks its executing e.g. "pbcopy", the host "fromvm" script is actually receiving "pbcopy" in the $SSH_ORIGINAL_COMMAND and can apply the appropriate access control or restrictions.