make fifo: mkfifo -m 600 /path/to/fifo
/etc/nginx/sites-enabled/site
[CUT]
ssl_certificate /path/to/cert;
ssl_password_file /path/to/fifo;
ssl_certificate_key /path/to/key;
[CUT]
/lib/systemd/system/sslpass.service
[Unit]
Description=SSL Passphrase Shim
[Service]
Type=simple
ExecStart=/bin/bash -c 'echo -n `systemd-ask-password "Enter SSL Passphrase: "` > /etc/nginx/sslpass'
#Restart=always
[Install]
WantedBy=nginx.service
Then systemctl daemon-reload && systemctl enable sslpass.service