Add hardened options to the systemd service

conf/systemd.service

@@ -3,18 +3,47 @@ Description=I hate money
 Requires=network.target mysql.service
 After=network.target mysql.service
 
+[Install]
+WantedBy=multi-user.target
+
 [Service]
 Type=simple
+Restart=always
+RestartSec=2
 User=__APP__
 Group=__APP__
 WorkingDirectory=__INSTALL_DIR__/
 Environment=IHATEMONEY_SETTINGS_FILE_PATH=__INSTALL_DIR__/ihatemoney.cfg
 ExecStart=__INSTALL_DIR__/venv/bin/gunicorn -c __INSTALL_DIR__/gunicorn.conf.py ihatemoney.wsgi:application
-Restart=always
-RestartSec=2
-
 StandardOutput=append:/var/log/__APP__/__APP__.log
 StandardError=inherit
 
-[Install]
-WantedBy=multi-user.target
+# Sandboxing options to harden security
+# Depending on specificities of your service/app, you may need to tweak these
+# .. but this should be a good baseline
+# Details for these options: https://www.freedesktop.org/software/systemd/man/systemd.exec.html
+NoNewPrivileges=yes
+#PrivateTmp=yes
+PrivateDevices=yes
+RestrictAddressFamilies=AF_UNIX AF_INET AF_INET6
+RestrictNamespaces=yes
+RestrictRealtime=yes
+DevicePolicy=closed
+ProtectSystem=full
+ProtectControlGroups=yes
+ProtectKernelModules=yes
+ProtectKernelTunables=yes
+LockPersonality=yes
+SystemCallFilter=~@clock @debug @module @mount @obsolete @reboot @setuid @swap
+
+# Denying access to capabilities that should not be relevant for webapps
+# Doc: https://man7.org/linux/man-pages/man7/capabilities.7.html
+CapabilityBoundingSet=~CAP_RAWIO CAP_MKNOD
+CapabilityBoundingSet=~CAP_AUDIT_CONTROL CAP_AUDIT_READ CAP_AUDIT_WRITE
+CapabilityBoundingSet=~CAP_SYS_BOOT CAP_SYS_TIME CAP_SYS_MODULE CAP_SYS_PACCT
+CapabilityBoundingSet=~CAP_LEASE CAP_LINUX_IMMUTABLE CAP_IPC_LOCK
+CapabilityBoundingSet=~CAP_BLOCK_SUSPEND CAP_WAKE_ALARM
+CapabilityBoundingSet=~CAP_SYS_TTY_CONFIG
+CapabilityBoundingSet=~CAP_MAC_ADMIN CAP_MAC_OVERRIDE
+CapabilityBoundingSet=~CAP_NET_ADMIN CAP_NET_BROADCAST CAP_NET_RAW
+CapabilityBoundingSet=~CAP_SYS_ADMIN CAP_SYS_PTRACE CAP_SYSLOG