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Reorganize DNS recommendations #2330

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Mar 30, 2024
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Reorganize DNS recommendations #2330

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43 changes: 42 additions & 1 deletion docs/advanced/dns-overview.md
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Original file line number Diff line number Diff line change
Expand Up @@ -82,6 +82,24 @@ Encrypted DNS can refer to one of a number of protocols, the most common ones be

Native implementation of DoH showed up in iOS 14, macOS 11, Microsoft Windows, and Android 13 (however, it won't be enabled [by default](https://android-review.googlesource.com/c/platform/packages/modules/DnsResolver/+/1833144)). General Linux desktop support is waiting on the systemd [implementation](https://github.com/systemd/systemd/issues/8639) so [installing third-party software is still required](../dns.md#encrypted-dns-proxies).

### Native Operating System Support

#### Android

Android 9 and above support DNS over TLS. The settings can be found in: **Settings** → **Network & Internet** → **Private DNS**.

#### Apple Devices

The latest versions of iOS, iPadOS, tvOS, and macOS, support both DoT and DoH. Both protocols are supported natively via [configuration profiles](https://support.apple.com/guide/security/configuration-profile-enforcement-secf6fb9f053/web) or through the [DNS Settings API](https://developer.apple.com/documentation/networkextension/dns_settings).

After installation of either a configuration profile or an app that uses the DNS Settings API, the DNS configuration can be selected. If a VPN is active, resolution within the VPN tunnel will use the VPN's DNS settings and not your system-wide settings.

Apple does not provide a native interface for creating encrypted DNS profiles. [Secure DNS profile creator](https://dns.notjakob.com/tool.html) is an unofficial tool for creating your own encrypted DNS profiles, however they will not be signed. Signed profiles are preferred; signing validates a profile's origin and helps to ensure the integrity of the profiles. A green "Verified" label is given to signed configuration profiles. For more information on code signing, see [About Code Signing](https://developer.apple.com/library/archive/documentation/Security/Conceptual/CodeSigningGuide/Introduction/Introduction.html).

#### Linux

`systemd-resolved`, which many Linux distributions use to do their DNS lookups, doesn't yet [support DoH](https://github.com/systemd/systemd/issues/8639). If you want to use DoH, you'll need to install a proxy like [dnscrypt-proxy](https://github.com/DNSCrypt/dnscrypt-proxy) and [configure it](https://wiki.archlinux.org/title/Dnscrypt-proxy) to take all the DNS queries from your system resolver and forward them over HTTPS.

## What can an outside party see?

In this example we will record what happens when we make a DoH request:
Expand Down Expand Up @@ -319,4 +337,27 @@ The [EDNS Client Subnet](https://en.wikipedia.org/wiki/EDNS_Client_Subnet) is a

It's intended to "speed up" delivery of data by giving the client an answer that belongs to a server that is close to them such as a [content delivery network](https://en.wikipedia.org/wiki/Content_delivery_network), which are often used in video streaming and serving JavaScript web apps.

This feature does come at a privacy cost, as it tells the DNS server some information about the client's location.
This feature does come at a privacy cost, as it tells the DNS server some information about the client's location, generally your IP network. For example, if your IP address is `198.51.100.32` the DNS provider might share `198.51.100.0/24` with the authoritative server. Some DNS providers anonymize this data by providing another IP address which is approximately near your location.

If you have `dig` installed you can test whether your DNS provider gives EDNS information out to DNS nameservers with the following command:

```bash
dig +nocmd -t txt o-o.myaddr.l.google.com +nocomments +noall +answer +stats
```

Note that this command will contact Google for the test, and return your IP as well as EDNS client subnet information. If you want to test another DNS resolver you can specify their IP, to test `9.9.9.11` for example:

```bash
dig +nocmd @9.9.9.11 -t txt o-o.myaddr.l.google.com +nocomments +noall +answer +stats
```

If the results include a second edns0-client-subnet TXT record (like shown below), then your DNS server is passing along EDNS information. The IP or network shown after is the precise information which was shared with Google by your DNS provider.

```text
o-o.myaddr.l.google.com. 60 IN TXT "198.51.100.32"
o-o.myaddr.l.google.com. 60 IN TXT "edns0-client-subnet 198.51.100.0/24"
;; Query time: 64 msec
;; SERVER: 9.9.9.11#53(9.9.9.11)
;; WHEN: Wed Mar 13 10:23:08 CDT 2024
;; MSG SIZE rcvd: 130
```
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