[Unit]
Description=Caddy HTTP/2 web server
Documentation=https://caddyserver.com/docs
After=network-online.target
Wants=network-online.target systemd-networkd-wait-online.service

[Service]
; Restart on crash (bad signal), but not on 'clean' failure (error exit code)
Restart=on-abnormal
; Allow up to 3 restarts within 10 seconds
; (it's unlikely that a user or properly-running script will do this)
StartLimitInterval=10
StartLimitBurst=3

; User and group the process will run as
; (www-data is the de facto standard on most systems)
User=www-data
Group=www-data

; Letsencrypt-issued certificates will be written to this directory.
Environment=CADDYPATH=/etc/ssl/caddy

; Always set "-root" to something safe in case it gets forgotten in the Caddyfile.
WorkingDirectory=/etc/ssl/caddy
ExecStart=/usr/local/bin/caddy -log stdout -agree=true -conf=/etc/caddy/Caddyfile -root=/var/tmp
ExecReload=/bin/kill -USR1 $MAINPID

; Limit the number of file descriptors; see `man systemd.exec` for more limit settings.
LimitNOFILE=1048576
; Unmodified caddy is not expected to use more than that.
LimitNPROC=64

; Use private /tmp and /var/tmp, which are discarded after caddy stops.
PrivateTmp=true
; Use a minimal /dev
PrivateDevices=true
; Hide /home, /root, and /run/user. Nobody will steal your SSH-keys.
ProtectHome=true
; Make /usr, /boot, /etc and possibly some more folders read-only.
ProtectSystem=full
; … except /etc/ssl/caddy, because we want Letsencrypt-certificates there
;   and /var/log/caddy, because we want a place where logs can go.
;   This merely retains r/w access rights, it does not add any new. Must still be writable on the host!
ReadWritePaths=/etc/ssl/caddy /var/log/caddy

; The following additional security directives only work with systemd v229 or later.
; They further retrict privileges that can be gained by caddy. Uncomment if you like.
; Note that you may have to add capabilities required by any plugins in use.
CapabilityBoundingSet=CAP_NET_BIND_SERVICE
AmbientCapabilities=CAP_NET_BIND_SERVICE
NoNewPrivileges=true

; Caveat: Some plugins need additional capabilities. Add them to both lines above.
; - plugin "upload" needs: CAP_LEASE

[Install]
WantedBy=multi-user.target

; Learn more:
;
;   * systemd: https://www.freedesktop.org/software/systemd/man/systemd.exec.html
;   * why caddy's systemd file is what it is https://github.com/mholt/caddy/pull/1566/files