So you inject a host ssh key pair at VM creation using cloud-init, then connect one time trusting that key and immediately replace the host keys in the VM. So there is still a brief race condition where the attacker could impersonate the VM if he had intercepted your cloud-init file, correct?
Also I don't see anywhere that the script reloads the sshd daemon, which AFAIK is necessary to get it to start using the new host keys and stop using the deleted initial host key.
Comments
So you inject a host ssh key pair at VM creation using cloud-init, then connect one time trusting that key and immediately replace the host keys in the VM. So there is still a brief race condition where the attacker could impersonate the VM if he had intercepted your cloud-init file, correct?
Also I don't see anywhere that the script reloads the sshd daemon, which AFAIK is necessary to get it to start using the new host keys and stop using the deleted initial host key.