2022-03-28 19:43:03 +02:00
|
|
|
# systemd-resolved additional config files
|
2020-07-04 18:06:18 +02:00
|
|
|
|
2022-03-28 19:43:03 +02:00
|
|
|
## Quickstart
|
|
|
|
|
|
|
|
|
|
```bash
|
|
|
|
|
sudo systemctl enable --now systemd-resolved.service
|
|
|
|
|
sudo ln -rsf /run/systemd/resolve/stub-resolv.conf /etc/resolv.conf
|
|
|
|
|
# After changing configuration
|
|
|
|
|
sudo systemctl restart systemd-resolved
|
|
|
|
|
```
|
|
|
|
|
|
|
|
|
|
## Files explained
|
2020-07-04 18:06:18 +02:00
|
|
|
|
2023-02-21 16:54:39 +01:00
|
|
|
- `00-defaults.conf` - configuration not touching resolvers. Disables DNSSEC (as
|
2023-02-21 18:33:31 +01:00
|
|
|
systemd-resolved doesn't handle it properly), enables opportunistic DoT and
|
|
|
|
|
caching.
|
2023-02-21 16:54:39 +01:00
|
|
|
- `dot-*.conf` - configuration to use the DNS provider with DNS-over-TLS. If
|
2023-02-21 18:33:31 +01:00
|
|
|
captive portals are a concern, `DNSOverTLS=no`.
|
2023-02-21 16:54:39 +01:00
|
|
|
- `README.md` - you are reading it right now.
|
2020-07-04 18:06:18 +02:00
|
|
|
|
2022-03-28 19:43:03 +02:00
|
|
|
## General commentary
|
2020-07-04 18:06:18 +02:00
|
|
|
|
2023-02-21 16:54:39 +01:00
|
|
|
- Based on my test DNSOverTLS is not supported in Ubuntu 18.04.x LTS (however
|
2023-02-21 18:33:31 +01:00
|
|
|
at the time of writing this README.md, the current version is Ubuntu 20.04.0)
|
|
|
|
|
(systemd v237). DNSOverTLS became supported in v239, strict mode (yes) in
|
|
|
|
|
v243 (big improvements in v244).
|
|
|
|
|
- TODO: find out when SNI became supported, I have just spotted it in the
|
|
|
|
|
fine manual in 2020-06-??.
|
2023-02-21 16:54:39 +01:00
|
|
|
- Domains has to be `.~` for them to override DHCP. See https://www.internetsociety.org/blog/2018/12/dns-privacy-in-linux-systemd
|
2023-02-21 18:33:31 +01:00
|
|
|
without which I wouldn't have got this right.
|
2023-02-21 16:54:39 +01:00
|
|
|
- DNSSEC may not work if the system is down for a long time and not updated.
|
2023-02-21 18:33:31 +01:00
|
|
|
Thus `allow-downgrade` may be better for non-tech people, even with the
|
|
|
|
|
potential downgrade attack. There are also captive portals, affecting
|
|
|
|
|
`DNSOverTLS`. Both take `yes` or `no` or their own special option,
|
|
|
|
|
for DNNSEC the `allow-downgrade`, for DNSOverTLS `opportunistic`.
|
2020-07-04 18:06:18 +02:00
|
|
|
|
|
|
|
|
Other links I have found important and my files are based on:
|
|
|
|
|
|
2023-02-21 16:54:39 +01:00
|
|
|
- https://wiki.archlinux.org/index.php/Systemd-resolved
|
2023-02-21 18:33:31 +01:00
|
|
|
- Also provides the serious issues systemd-resolved+DNSSEC issues, https://github.com/systemd/systemd/issues/10579 & https://github.com/systemd/systemd/issues/9867
|
2023-02-21 16:54:39 +01:00
|
|
|
- request for strict DOT: https://github.com/systemd/systemd/issues/10755
|
|
|
|
|
- vulnerable to MITM: https://github.com/systemd/systemd/issues/9397
|
