Systemd hardening (#33)

* Update systemd.service

conf/systemd.service

@@ -12,14 +12,36 @@ Environment="PATH=__ENV_PATH__"
 Environment="NODE_ENV=production"
 ExecStart=__YNH_NPM__ start --production
 Restart=always
-PrivateTmp=true
-PrivateDevices=true
 
-ProtectControlGroups=true
+# Sandboxing options to harden security
-ProtectHome=true
+# Depending on specificities of your service/app, you may need to tweak these 
-ProtectKernelTunables=true
+# .. 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
-RestrictSUIDSGID=true
+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 
 
 [Install]
 WantedBy=multi-user.target