You can configure Orbot so that all network traffic on your device or only traffic of specific apps like DAVdroid is routed over it. If you prefer the classic proxy method:
- Install Orbot. It provides a local HTTP(S) proxy (and a SOCKS proxy, but we won't use that one).
- Open DAVdroid, choose Settings from the app drawer and enable "Override proxy settings". Set the proxy to
localhost:8118(Proxy hostname: localhost, Proxy port: 8118), which is the default port of Orbot.
- Make sure Orbot is active and running.
- When DAVdroid connects to a CalDAV/CardDAV server, it will use the Orbot HTTP proxy and thus connect over Tor.
Tor domain names (.onion, .tor, .exit) will also work because when using a HTTP proxy, there's no need for client-side DNS resolution. One exception: at account setup, DAVdroid will try to fetch SRV records directly, so "Login with email" and host name detection by SRV records either won't work or may be routed without using Tor.
Be aware that using Tor is known to provoke sophisticated attacks. Make sure that you know what you're doing. We also recommend to distrust system certificates in DAVdroid settings when using DAVdroid over Tor.