先获取服务器的证书，保存为 lvv.me.pem：
$ openssl s_client -servername lvv.me -connect lvv.me:443 < /dev/null 2>/dev/null | openssl x509 -outform pem > lvv.me.pem
获取这个证书的指纹信息：
$ openssl x509 -noout -fingerprint -sha256 -inform pem -in lvv.me.pem
8D:62:36:52:AD:5A:53:D1:FC:EA:5D:0A:35:CF:2F:60:5C:8C:74:42:2A:C6:AB:11:05:70:FD:A9:85:8A:0B:E0
