/etc/sshd_config 修改为

PermitRootLogin no
PasswordAuthentication no
PermitEmptyPasswords no
ChallengeResponseAuthentication no

sudo launchctl unload /System/Library/LaunchDaemons/ssh.plist
sudo launchctl load -w /System/Library/LaunchDaemons/ssh.plist

/etc/sshd_config 和 /private/etc/sshd_config 是同一个文件