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Use abbreviations across site (#1060)

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Signed-off-by: Daniel Gray <dng@disroot.org>
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Jonah Aragon
2022-04-22 17:03:54 +00:00
parent a4298c0992
commit 97640d4f70
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docs/technology/dns.en.md
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@@ -3,15 +3,15 @@ title: "Introduction to DNS"
icon: material/dns
---
The [Domain Name System (DNS)](https://en.wikipedia.org/wiki/Domain_Name_System) is the 'phonebook of the Internet'. DNS translates domain names to [IP](https://en.wikipedia.org/wiki/Internet_Protocol) addresses so browsers and other services can load Internet resources, through a decentralized network of servers.
The [Domain Name System](https://en.wikipedia.org/wiki/Domain_Name_System) is the 'phonebook of the Internet'. DNS translates domain names to IP addresses so browsers and other services can load Internet resources, through a decentralized network of servers.
## What is DNS?
When you visit a website, a numerical address is returned. For example, when you visit `privacyguides.org`, the address `192.98.54.105` is returned.
DNS has existed since the [early days](https://en.wikipedia.org/wiki/Domain_Name_System#History) of the Internet. DNS requests made to and from DNS servers are **not** generally encrypted. In a residential setting, a customer is given servers by the [ISP](https://en.wikipedia.org/wiki/Internet_service_provider) via [Dynamic Host Configuration Protocol (DHCP)](https://en.wikipedia.org/wiki/Dynamic_Host_Configuration_Protocol).
DNS has existed since the [early days](https://en.wikipedia.org/wiki/Domain_Name_System#History) of the Internet. DNS requests made to and from DNS servers are **not** generally encrypted. In a residential setting, a customer is given servers by the ISP via [DHCP](https://en.wikipedia.org/wiki/Dynamic_Host_Configuration_Protocol).
Unencrypted DNS requests are able to be easily **surveilled** and **modified** in transit. In some parts of the world, ISPs are ordered to do primitive [DNS filtering](https://en.wikipedia.org/wiki/DNS_blocking). When a user requests the IP of a domain that is blocked, the server may not respond or may respond with a different IP address. As the DNS protocol is not encrypted, the ISP (or any network operator) can use [deep packet inspection (DPI)](https://en.wikipedia.org/wiki/Deep_packet_inspection) to monitor requests. ISPs can also block requests based on common characteristics, regardless of which DNS server is used. Unencrypted DNS always uses [port](https://en.wikipedia.org/wiki/Port_(computer_networking)) 53 and always uses the [User Datagram Protocol (UDP)](https://en.wikipedia.org/wiki/User_Datagram_Protocol).
Unencrypted DNS requests are able to be easily **surveilled** and **modified** in transit. In some parts of the world, ISPs are ordered to do primitive [DNS filtering](https://en.wikipedia.org/wiki/DNS_blocking). When a user requests the IP address of a domain that is blocked, the server may not respond or may respond with a different IP address. As the DNS protocol is not encrypted, the ISP (or any network operator) can use [DPI](https://en.wikipedia.org/wiki/Deep_packet_inspection) to monitor requests. ISPs can also block requests based on common characteristics, regardless of which DNS server is used. Unencrypted DNS always uses [port](https://en.wikipedia.org/wiki/Port_(computer_networking)) 53 and always uses UDP.
Below, we discuss and provide a tutorial to prove what an outside observer may see using regular unencrypted DNS and [encrypted DNS](#what-is-encrypted-dns).
@@ -23,7 +23,7 @@ Below, we discuss and provide a tutorial to prove what an outside observer may s
tshark -w /tmp/dns.pcap udp port 53 and host 1.1.1.1 or host 8.8.8.8
```
2. We can then use [`dig`](https://en.wikipedia.org/wiki/Dig_(command)) (Linux, MacOS etc) or [`nslookup`](https://en.wikipedia.org/wiki/Nslookup) (Windows) to send the DNS lookup to both servers. Software such as web browsers do these lookups automatically, unless they are configured to use [encrypted DNS](#what-is-encrypted-dns).
2. We can then use [`dig`](https://en.wikipedia.org/wiki/Dig_(command)) (Linux, MacOS etc) or [`nslookup`](https://en.wikipedia.org/wiki/Nslookup) (Windows) to send the DNS lookup to both servers. Software such as web browsers do these lookups automatically, unless they are configured to use encrypted DNS.
=== "Linux, MacOS"
@@ -69,17 +69,17 @@ Encrypted DNS can refer to one of a number of protocols, the most common ones be
### DNSCrypt
[**DNSCrypt**](https://en.wikipedia.org/wiki/DNSCrypt) was one of the first methods of encrypting DNS queries. The [protocol](https://en.wikipedia.org/wiki/DNSCrypt#Protocol) operates on [port 443](https://en.wikipedia.org/wiki/Well-known_ports) and works with both the [TCP](https://en.wikipedia.org/wiki/Transmission_Control_Protocol) or [UDP](https://en.wikipedia.org/wiki/User_Datagram_Protocol) transport protocols. DNSCrypt has never been submitted to the [Internet Engineering Task Force (IETF)](https://en.wikipedia.org/wiki/Internet_Engineering_Task_Force) nor has it gone through the [Request for Comments (RFC)](https://en.wikipedia.org/wiki/Request_for_Comments) process, so it has not been used widely outside of a few [implementations](https://dnscrypt.info/implementations). As a result, it has been largely replaced by the more popular [DNS over HTTPS (DoH)](#dns-over-https-doh).
[**DNSCrypt**](https://en.wikipedia.org/wiki/DNSCrypt) was one of the first methods of encrypting DNS queries. DNSCrypt operates on port 443 and works with both the TCP or UDP transport protocols. DNSCrypt has never been submitted to the [Internet Engineering Task Force (IETF)](https://en.wikipedia.org/wiki/Internet_Engineering_Task_Force) nor has it gone through the [Request for Comments (RFC)](https://en.wikipedia.org/wiki/Request_for_Comments) process, so it has not been used widely outside of a few [implementations](https://dnscrypt.info/implementations). As a result, it has been largely replaced by the more popular [DNS over HTTPS](#dns-over-https-doh).
### DNS over TLS (DoT)
[**DNS over TLS (DoT)**](https://en.wikipedia.org/wiki/DNS_over_TLS) is another method for encrypting DNS communication that is defined in [RFC 7858](https://datatracker.ietf.org/doc/html/rfc7858). Support was first implemented in [Android 9](https://en.wikipedia.org/wiki/Android_Pie), [iOS 14](https://en.wikipedia.org/wiki/IOS_14), and on Linux in [systemd-resolved](https://www.freedesktop.org/software/systemd/man/resolved.conf.html#DNSOverTLS=) in version 237. Preference in the industry has been moving away from DoT to [DNS over HTTPS](#dns-over-https-doh) in recent years, as DoT is a [complex protocol](https://dnscrypt.info/faq/) and has varying compliance to the RFC across the implementations that exist. DoT also operates on a dedicated port 853 and that can be blocked easily by restrictive firewalls.
[**DNS over TLS**](https://en.wikipedia.org/wiki/DNS_over_TLS) is another method for encrypting DNS communication that is defined in [RFC 7858](https://datatracker.ietf.org/doc/html/rfc7858). Support was first implemented in Android 9, iOS 14, and on Linux in [systemd-resolved](https://www.freedesktop.org/software/systemd/man/resolved.conf.html#DNSOverTLS=) in version 237. Preference in the industry has been moving away from DoT to DoH in recent years, as DoT is a [complex protocol](https://dnscrypt.info/faq/) and has varying compliance to the RFC across the implementations that exist. DoT also operates on a dedicated port 853 which can be blocked easily by restrictive firewalls.
### DNS over HTTPS (DoH)
[**DNS over HTTPS**](https://en.wikipedia.org/wiki/DNS_over_HTTPS) as defined in [RFC 8484](https://datatracker.ietf.org/doc/html/rfc8484) packages queries in the [HTTP/2](https://en.wikipedia.org/wiki/HTTP/2) protocol and provides security with [HTTPS](https://en.wikipedia.org/wiki/HTTPS). Support was first added in web browsers such as [Firefox 60](https://support.mozilla.org/en-US/kb/firefox-dns-over-https) and [Chrome 83](https://blog.chromium.org/2020/05/a-safer-and-more-private-browsing-DoH.html).
[**DNS over HTTPS**](https://en.wikipedia.org/wiki/DNS_over_HTTPS) as defined in [RFC 8484](https://datatracker.ietf.org/doc/html/rfc8484) packages queries in the [HTTP/2](https://en.wikipedia.org/wiki/HTTP/2) protocol and provides security with HTTPS. Support was first added in web browsers such as Firefox 60 and Chrome 83.
Native implementations showed up in [iOS 14](https://en.wikipedia.org/wiki/IOS_14), [macOS 11](https://en.wikipedia.org/wiki/MacOS_11), [Microsoft Windows](https://docs.microsoft.com/en-us/windows-server/networking/dns/doh-client-support), 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#linux).
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#linux).
## What can an outside party see?
@@ -139,7 +139,7 @@ Server Name Indication is typically used when a IP address hosts many websites.
wireshark -r /tmp/pg.pcap
```
We will see the [connection establishment](https://en.wikipedia.org/wiki/Transmission_Control_Protocol#Connection_establishment), followed by the [TLS handshake](https://www.cloudflare.com/learning/ssl/what-happens-in-a-tls-handshake/) for the Privacy Guides website. Around frame 5. you'll see a "Client Hello".
We will see the connection establishment, followed by the TLS handshake for the Privacy Guides website. Around frame 5. you'll see a "Client Hello".
5. Expand the triangle &#9656; next to each field:
@@ -151,7 +151,7 @@ Server Name Indication is typically used when a IP address hosts many websites.
▸ Server Name Indication extension
```
6. We can see the [Server Name Indication (SNI)](https://en.wikipedia.org/wiki/Server_Name_Indication) value which discloses the website we are visiting. The `tshark` command can give you the value directly for all packets containing a SNI value:
6. We can see the SNI value which discloses the website we are visiting. The `tshark` command can give you the value directly for all packets containing a SNI value:
```bash
tshark -r /tmp/pg.pcap -Tfields -Y tls.handshake.extensions_server_name -e tls.handshake.extensions_server_name
@@ -163,7 +163,7 @@ Governments, in particular [China](https://www.zdnet.com/article/china-is-now-bl
### Online Certificate Status Protocol (OCSP)
Another way your browser can disclose your browsing activities is with the [Online Certificate Status Protocol](https://en.wikipedia.org/wiki/Online_Certificate_Status_Protocol). When visiting a [HTTPS](https://en.wikipedia.org/wiki/HTTPS) website, the browser might check to see if the [X.509](https://en.wikipedia.org/wiki/X.509) [certificate](https://en.wikipedia.org/wiki/Public_key_certificate) has been [revoked](https://en.wikipedia.org/wiki/Certificate_revocation_list). This is generally done through the [HTTP](https://en.wikipedia.org/wiki/Hypertext_Transfer_Protocol) protocol, meaning it is **not** encrypted.
Another way your browser can disclose your browsing activities is with the [Online Certificate Status Protocol](https://en.wikipedia.org/wiki/Online_Certificate_Status_Protocol). When visiting a [HTTPS](https://en.wikipedia.org/wiki/HTTPS) website, the browser might check to see if the website's [certificate](https://en.wikipedia.org/wiki/Public_key_certificate) has been revoked. This is generally done through the HTTP protocol, meaning it is **not** encrypted.
The OCSP request contains the certificate "[serial number](https://en.wikipedia.org/wiki/Public_key_certificate#Common_fields)", which is unique. It is sent to the "OCSP responder" in order to check its status.
@@ -281,7 +281,7 @@ Encrypted DNS with a 3rd party should only be used to get around redirects and b
## What is DNSSEC and when is it used?
[Domain Name System Security Extensions (DNSSEC)](https://en.wikipedia.org/wiki/Domain_Name_System_Security_Extensions) is used to provide authenticity to the records being fetched from upstream DNS servers. It doesn't provide confidentiality, for that we use one of the [encrypted DNS](#what-is-encrypted-dns) protocols discussed above.
[Domain Name System Security Extensions](https://en.wikipedia.org/wiki/Domain_Name_System_Security_Extensions) (DNSSEC) is used to provide authenticity to the records being fetched from upstream DNS servers. It doesn't provide confidentiality, for that we use one of the [encrypted DNS](#what-is-encrypted-dns) protocols discussed above.
## What is QNAME minimization?
@@ -293,6 +293,8 @@ Instead of sending the whole domain `privacyguides.org`, QNAME minimization mean
The [EDNS Client Subnet](https://en.wikipedia.org/wiki/EDNS_Client_Subnet) is a method for a recursive DNS resolver to specify a [subnetwork](https://en.wikipedia.org/wiki/Subnetwork) for the [host or client](https://en.wikipedia.org/wiki/Client_(computing)) which is making the DNS query.
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 (CDN)](https://en.wikipedia.org/wiki/Content_delivery_network), which are often used in video streaming and serving JavaScript web apps.
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.
--8<-- "includes/abbreviations.en.md"