Apply systemd restrictions to echobot

These options are suggested by
`systemd-analyze security echobot.service`

CHANGELOG.md

@@ -2,6 +2,9 @@
 
 ## untagged 
 
+- Apply systemd restrictions to echobot
+  ([#259](https://github.com/deltachat/chatmail/pull/259))
+
 - re-enable running the CI in pull requests, but not concurrently 
   ([#258](https://github.com/deltachat/chatmail/pull/258))
 

cmdeploy/src/cmdeploy/service/echobot.service.f

@@ -7,5 +7,44 @@ Environment="PATH={remote_venv_dir}:$PATH"
 Restart=always
 RestartSec=30
 
+# Apply security restrictions suggested by
+#   systemd-analyze security echobot.service
+CapabilityBoundingSet=
+LockPersonality=true
+MemoryDenyWriteExecute=true
+NoNewPrivileges=true
+PrivateDevices=true
+PrivateMounts=true
+PrivateTmp=true
+PrivateUsers=true
+ProtectClock=true
+ProtectControlGroups=true
+ProtectHostname=true
+ProtectKernelLogs=true
+ProtectKernelModules=true
+ProtectKernelTunables=true
+ProtectProc=noaccess
+
+# Should be "strict", but we currently write /accounts folder in a protected path
+ProtectSystem=full
+
+RemoveIPC=true
+RestrictAddressFamilies=AF_INET AF_INET6
+RestrictNamespaces=true
+RestrictRealtime=true
+RestrictSUIDSGID=true
+SystemCallArchitectures=native
+SystemCallFilter=~@clock
+SystemCallFilter=~@cpu-emulation
+SystemCallFilter=~@debug
+SystemCallFilter=~@module
+SystemCallFilter=~@mount
+SystemCallFilter=~@obsolete
+SystemCallFilter=~@raw-io
+SystemCallFilter=~@reboot
+SystemCallFilter=~@resources
+SystemCallFilter=~@swap
+UMask=0077
+
 [Install]
 WantedBy=multi-user.target