[Unit]
Description=mox mail server
After=network-online.target
Wants=network-online.target

[Service]
UMask=007
LimitNOFILE=65535
Type=simple
# Mox starts as root, but drops privileges after binding network addresses.
WorkingDirectory=/home/mox
ExecStart=/home/mox/mox serve
RestartSec=5s
Restart=always
ExecStop=/home/mox/mox stop
SyslogFacility=mail

# Isolate process, reducing attack surface.
PrivateDevices=yes
PrivateTmp=yes
ProtectSystem=strict
ReadWritePaths=/home/mox/config /home/mox/data
ProtectKernelTunables=yes
ProtectControlGroups=yes
AmbientCapabilities=
CapabilityBoundingSet=CAP_SETUID CAP_SETGID CAP_NET_BIND_SERVICE CAP_CHOWN CAP_FSETID CAP_DAC_OVERRIDE CAP_DAC_READ_SEARCH CAP_FOWNER
NoNewPrivileges=yes
RestrictAddressFamilies=AF_INET AF_INET6 AF_UNIX AF_NETLINK
ProtectProc=invisible
RestrictNamespaces=yes
RestrictRealtime=yes
RemoveIPC=yes
ProtectHostname=yes
ProtectClock=yes
ProtectKernelLogs=yes
ProtectKernelModules=yes
MemoryDenyWriteExecute=yes
LockPersonality=yes
DevicePolicy=closed
SystemCallArchitectures=native
SystemCallFilter=@system-service

# Cannot have RestrictSUIDSGID with setgid directories.
#RestrictSUIDSGID=yes

# prevents CAP_NET_BIND_SERVICE from working?
#PrivateUsers=yes

# To check security-related settings:
# sudo systemd-analyze security mox.service

[Install]
WantedBy=multi-user.target