mirror of
http://git.nowherejezfoltodf4jiyl6r56jnzintap5vyjlia7fkirfsnfizflqd.onion/nihilist/opsec-blogposts.git
synced 2025-06-08 09:39:36 +00:00
192 lines
12 KiB
Markdown
192 lines
12 KiB
Markdown
---
|
||
author: cynthia
|
||
date: 2025-06-01
|
||
gitea_url: "http://git.nowherejezfoltodf4jiyl6r56jnzintap5vyjlia7fkirfsnfizflqd.onion/nihilist/blog-contributions/issues/311"
|
||
xmr: 84ybq68PNqKL2ziGKfkmHqAxu1WpdSFwV3DreM88DfjHVbnCgEhoztM7T9cv5gUUEL7jRaA6LDuLDXuDw24MigbnGqyRfgp
|
||
---
|
||
# DoT, DoH, DNSCrypt, DNS over Tor and Local DNS: What actually protects you? (and tutorials on how to set each of them up)
|
||
|
||
DNS is the most common way to resolve domain names into IP addresses. It's a pretty old protocol that still works, albeit with some shortcomings that have plagued the protocol over the years. The protocol lacks any encryption which allows any 3rd party with access to your connection (such as your ISP, etc.) to easily spy on DNS queries or even intercept and replace DNS responses to sabotage access to certain websites.
|
||
Several solutions have popped up over the years to fix these issues, These mostly just act as wrappers around the DNS protocol in a way. This blogpost will measure the advantages and disadvantages of these solutions, and also offer a guide on how to set up each of them.
|
||
This blogpost includes: DNS over TLS (DoT), DNS over HTTPS (DoH), DNSCrypt, DNS over Tor/DNS over VPN and Local DNS
|
||
|
||
## Introductions to all the DNS protocols
|
||
|
||
**NOTE**: The interceptor in the graphs may not be reflective of a interceptor in a real situation. While we've tried to make the interceptor reflective of most DPIs and situations involving them, there are several factors (such as TLS fingerprint, etc.) that may allow for protocol identification.
|
||
|
||
### DNS over TLS (DoT)
|
||
|
||
|
||
DNS over TLS is (one of) the first RFC-standard DNS encryption wrappers, wrapping the protocol around the Transport Layer Security, other than that, it's fairly simple. The problems that it has is that it has its own standard port number, which makes it easy to tell to a 3rd party that you are using DNS over TLS, and that it's slower, since it has to run over TCP rather than UDP.
|
||
|
||
### DNS over HTTPS (DoH)
|
||
|
||
|
||
DNS over HTTPS is the more newer RFC-standard DNS encryption wrapper, which wraps the protocol around HTTPS and uses 443 on TCP. The benefits are about the same as DNS over TLS, except that the fact that DNS is transmitted over HTTPS makes the protocol much harder to block than DNS over TLS (DoT) due it blending in with regular HTTPS traffic. ISPs and DPIs have to resort to blocking IPs associated with common DoH servers (which does not block DoH as a whole).
|
||
|
||
### DNSCrypt
|
||
|
||
|
||
DNSCrypt is the oldest DNS encryption wrapper protocol, It is more optimized for speed than DoT and DoH and uses 443 on TCP/UDP (same port as HTTPS). The port number helps obfuscate the protocol at a basic level from ISPs and other MiTMs from detecting the usage of the protocol (although it won't help against DPIs). DNSCrypt also has a feature called Anonymized DNS which we will be talking in the next sub-section.
|
||
|
||
#### Anonymized DNS
|
||
|
||
|
||
Anonymized DNS is a relay system in DNSCrypt where your DNS queries and responses are relayed through a DNSCrypt server, so that the final DNSCrypt server is not able to tell where the queries came from (granted if the relay and final DNSCrypt server are both not owned or associated with each other). This allows for anonymous, yet still fast DNS queries.
|
||
|
||
### DNS over Tor
|
||
|
||
|
||
DNS over Tor is simply the act of routing your DNS queries over Tor. Since Tor does not support UDP (which DNS uses), it's done using a special feature in the Tor daemon which hosts a DNS port locally that resolves domain names over at the exit node's resolver. Although the DNS data is encrypted during transit through the Tor relays, it will most likely end up unencrypted during the transmission between the exit node and the exit node's DNS server, which will allow for any 3rd parties spying on the exit node's traffic to be able to look at (or even tamper with) your DNS query and responses. But, due to the nature of Tor, it may still be anonymous.
|
||
|
||
### DNS over VPN
|
||
|
||
|
||
DNS over VPN is the act of routing your DNS queries over a VPN, This has about the same advantages and disadvantages as DNS over Tor (provided that the benefit of anonymity is dependent on the VPN you're using). For the sake of the ratings table below, we'll be referring to both DNS over Tor and DNS over VPN as DNS over Tor/VPN.
|
||
|
||
### Local DNS
|
||
|
||
|
||
Local DNS is the act of hosting a DNS server locally rather than using a public one on the Internet, This doesn't provide any privacy or anonymity benefits whatsoever other than the fact that the initial query (and the device who made it) is private inside your LAN.
|
||
|
||
Since DNS is unencrypted, The recursive queries that the DNS server makes to authoritative DNS servers is visible to any 3rd parties spying over your traffic, which exposes what domain you are looking for.
|
||
|
||
The only reason you should be doing this is to host a PiHole or a DNS server that blocks away analytics domains, but for the sake of this blogpost, we'll be referring to a regular local DNS (with no blocking capabilities).
|
||
|
||
## DNS protocol ratings
|
||
First of all, if we were to figure out which of these protocols protects us, we'll need some way to measure how well they perform. We will be measuring each of the following abilities:
|
||
* Encryption: Whether the DNS queries and responses are fully end-to-end encrypted (from user to the DNS server, including the Tor nodes/VPN node in-between)
|
||
* Detectability: Whether a 3rd party adversary (such as the user's ISP) can detect and distinguish usage of the protocol from the rest of the user's traffic.
|
||
* Anonymity: Whether the protocol offers anonymity protection for the user.
|
||
|
||
| Abilities | DNS over TLS | DNS over HTTPS | DNSCrypt | DNS over Tor/VPN | Local DNS |
|
||
|---------------|---------------------------------|-----------------------------------|---------------------------------|------------------|-----------|
|
||
| Encryption | ✅ The protocol uses TLS between the user and the DNS server. | ✅ The protocol uses TLS or SSL between the user and the DNS server. | ✅ The protocol uses a custom encryption protocol between the user and the DNS server. | ✳️ Although the connection between the user and the Tor node/VPN is encrypted, DNS is unencrypted so the exit node or VPN server can see queries and responses | ❎️ Although a 3rd party adversary cannot intercept a local DNS server, they can look at the authoritative DNS queries that the server makes |
|
||
| Detectability | ❎️The protocol has its own standard port (853/TCP) which makes it super easy to detect for a 3rd party | ✅ The protocol blends in with HTTPS traffic, which makes it much harder to detect | ✳️ Although DNSCrypt listens on port 443 (UDP/TCP, the same port as HTTPS) which makes surface-level detection much harder, the use of a custom protocol may allow for detection on DPIs that are written to distinguish DNSCrypt's protocol from TLS/SSL protocol | ✅ A 3rd party adversary would not be able to detect DNS usage from the Tor/VPN traffic | ✅ The traffic from the local DNS server appears just like any other DNS query |
|
||
| Anonymity | ✳️ The protocol does not offer built-in anonymity protection, but it can be used over Tor. | ✳️ The protocol does not offer built-in anonymity protection, but it can be used over Tor. | ✅ DNSCrypt has a feature called Anonymized DNS, where instead of connecting to a DNSCrypt server directly, a user can connect through a relay DNSCrypt server to relay data over to that server. | ✅ Tor offers anonymity protection (maybe same thing for VPN but a little different) | ❎️ Unencrypted authoritative DNS queries (done by the local DNS server) can allow the user to be deanonymized by a 3rd party adversary |
|
||
|
||
## How to set up
|
||
|
||
### DNS over TLS
|
||
|
||
For most Debian-like distributions, systemd-resolved may already be used and pre-installed.
|
||
|
||
1. Enable `systemd-resolved`, if not enabled already.
|
||
|
||
```bash
|
||
root@localhost:~# systemctl enable --now systemd-resolved
|
||
```
|
||
|
||
2. Edit `systemd-resolved`'s configuration file to use DNS-over-TLS and a DoT server of your choice.
|
||
|
||
```bash
|
||
root@localhost:~# vim /etc/systemd/resolved.conf
|
||
```
|
||
|
||
This example configuration will use Quad9's DoT server.
|
||
|
||
```ini
|
||
[Resolve]
|
||
DNS=9.9.9.9#dns.quad9.net 149.112.112.112#dns.quad9.net 2620:fe::fe#dns.quad9.net 2620:fe::9#dns.quad9.net
|
||
DNSSEC=yes
|
||
DNSOverTLS=yes
|
||
Domains=~.
|
||
```
|
||
|
||
3. Restart `systemd-resolved` to use the new configuration.
|
||
|
||
```bash
|
||
root@localhost:~# systemctl restart systemd-resolved
|
||
```
|
||
|
||
### DNS over HTTPS and DNSCrypt
|
||
|
||
We'll be using `dnscrypt-proxy` for this section of the tutorial, which offers support for both DNS over HTTPS and DNSCrypt.
|
||
|
||
1. Create a directory for `dnscrypt-proxy`, This can be anywhere from your home directory to a directory in /opt.
|
||
We'll be creating `/opt/dnscrypt-proxy` in this tutorial.
|
||
|
||
```bash
|
||
root@localhost:~# mkdir -p /opt/dnscrypt-proxy
|
||
root@localhost:~# cd /opt/dnscrypt-proxy/
|
||
```
|
||
|
||
2. Download a prebuilt version of `dnscrypt-proxy`, You can pick which CPU architecture is in your system from [the list of dnscrypt-proxy binaries](https://github.com/jedisct1/dnscrypt-proxy/releases/latest)
|
||
We'll be downloading 2.1.12 for x86_64 in this tutorial.
|
||
|
||
Example:
|
||
|
||
```bash
|
||
root@localhost:/opt/dnscrypt-proxy# curl -L -O https://github.com/DNSCrypt/dnscrypt-proxy/releases/download/2.1.12/dnscrypt-proxy-linux_x86_64-2.1.12.tar.gz
|
||
```
|
||
3. (Optional) Download and verify the minisign signature of the tar file
|
||
|
||
Install minisign and download the minisig file for the binary you downloaded
|
||
|
||
Example:
|
||
|
||
```bash
|
||
root@localhost:/opt/dnscrypt-proxy# apt install minisign
|
||
root@localhost:/opt/dnscrypt-proxy# curl -L -O https://github.com/DNSCrypt/dnscrypt-proxy/releases/download/2.1.12/dnscrypt-proxy-linux_x86_64-2.1.12.tar.gz.minisig
|
||
```
|
||
|
||
Verify the minisig file with the official `dnscrypt-proxy` public key
|
||
|
||
```bash
|
||
root@localhost:/opt/dnscrypt-proxy# minisign -Vm dnscrypt-proxy-*.tar.gz -P RWTk1xXqcTODeYttYMCMLo0YJHaFEHn7a3akqHlb/7QvIQXHVPxKbjB5
|
||
```
|
||
|
||
If everything is fine, it should say: `Signature and comment signature verified`
|
||
|
||
4. Extract the tar file. All the files should be in a sub-directory in the tar file, so files have to be moved back to the current directory.
|
||
|
||
Example:
|
||
```bash
|
||
root@localhost:/opt/dnscrypt-proxy# tar -xvf dnscrypt-proxy-linux_x86_64-2.1.12.tar.gz
|
||
root@localhost:/opt/dnscrypt-proxy# mv linux-x86_64/* .
|
||
root@localhost:/opt/dnscrypt-proxy# rmdir linux-x86_64
|
||
```
|
||
5. Disable any other DNS resolvers running. You can check with `ss -lp 'sport = :domain'`.
|
||
Our example machine is currently running `systemd-resolved`, so we will disable and stop that.
|
||
|
||
```bash
|
||
root@localhost:/opt/dnscrypt-proxy# systemctl stop systemd-resolved
|
||
root@localhost:/opt/dnscrypt-proxy# systemctl disable systemd-resolved
|
||
```
|
||
|
||
6. Copy the example configuration file, and start `dnscrypt-proxy` to see if it works.
|
||
|
||
```bash
|
||
root@localhost:/opt/dnscrypt-proxy# cp example-dnscrypt-proxy.toml dnscrypt-proxy.toml
|
||
root@localhost:/opt/dnscrypt-proxy# ./dnscrypt-proxy
|
||
```
|
||
|
||
7. While `dnscrypt-proxy` is running, back up `/etc/resolv.conf` and create a new one using `dnscrypt-proxy`'s DNS port
|
||
|
||
```bash
|
||
root@localhost:/opt/dnscrypt-proxy# mv /etc/resolv.conf /etc/resolv.conf.bak
|
||
root@localhost:/opt/dnscrypt-proxy# vim /etc/resolv.conf
|
||
```
|
||
|
||
The contents of `/etc/resolv.conf` should be written like this:
|
||
|
||
```
|
||
nameserver 127.0.0.1
|
||
options edns0
|
||
```
|
||
Afterwards, test if `dnscrypt-proxy` is working by resolving `example.com` with it.
|
||
|
||
```bash
|
||
root@localhost:/opt/dnscrypt-proxy# ./dnscrypt-proxy -resolve example.com
|
||
```
|
||
|
||
If it was able to resolve `example.com`, congratulations, `dnscrypt-proxy` is now working.
|
||
|
||
8. Close the running `dnscrypt-proxy`, install it as a service and start it up!
|
||
|
||
```bash
|
||
root@localhost:/opt/dnscrypt-proxy# ./dnscrypt-proxy -service install
|
||
root@localhost:/opt/dnscrypt-proxy# ./dnscrypt-proxy -service start
|
||
```
|
||
|
||
Now we are onto configuring `dnscrypt-proxy` to use DoH and/or DNSCrypt.
|