It is not a patch. It doesn't require any code changes to OpenSSH.
opkssh uses AuthorizedKeysCommand field in sshd_config. OpenBSD added this config field to OpenSSH to enable people to do stuff like opkssh or instance-connect without needing to do code patches. OpenSSH is really smart about enabling functionality like this via the config.
opkssh uses AuthorizedKeysCommand field in sshd_config. OpenBSD added this config field to OpenSSH to enable people to do stuff like opkssh or instance-connect without needing to do code patches. OpenSSH is really smart about enabling functionality like this via the config.