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DNS over HTTPS

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DNS over HTTPS
Communication protocol
Purposeencapsulate DNS in HTTPS for privacy and security
IntroductionOctober 2018; 6 years ago (2018-10)
OSI layerApplication Layer
RFC(s)RFC 8484
Internet security
protocols
Key management
Application layer
Domain Name System
Internet Layer

DNS over HTTPS (DoH) is a protocol for performing remote Domain Name System (DNS) resolution via the HTTPS protocol. A goal of the method is to increase user privacy and security by preventing eavesdropping and manipulation of DNS data by man-in-the-middle attacks[1] by using the HTTPS protocol to encrypt the data between the DoH client and the DoH-based DNS resolver. By March 2018, Google and the Mozilla Foundation had started testing versions of DNS over HTTPS.[2][3] In February 2020, Firefox switched to DNS over HTTPS by default for users in the United States.[4]

An alternative to DoH is the DNS over TLS (DoT) protocol, a similar standard for encrypting DNS queries, differing only in the methods used for encryption and delivery. On the basis of privacy and security, whether or not a superior protocol exists among the two is a matter of controversial debate, while others argue the merits of either depend on the specific use case.[5]

Technical details

DoH is a proposed standard, published as RFC 8484 (October 2018) by the IETF. It uses HTTP/2 and HTTPS, and supports the wire format DNS response data, as returned in existing UDP responses, in an HTTPS payload with the MIME type application/dns-message.[1][6] If HTTP/2 is used, the server may also use HTTP/2 server push to send values that it anticipates the client may find useful in advance.[7]

DoH is a work in progress. Even though the IETF has published RFC 8484 as a proposed standard and companies are experimenting with it,[8][9] the IETF has yet to determine how it should best be implemented. The IETF is evaluating a number of approaches for how best to deploy DoH and is looking to set up a working group, Adaptive DNS Discovery (ADD), to do this work and develop a consensus. In addition, other industry working groups such as the Encrypted DNS Deployment Initiative, have been formed to "define and adopt DNS encryption technologies in a manner that ensures the continued high performance, resiliency, stability and security of the Internet's critical namespace and name resolution services, as well as ensuring the continued unimpaired functionality of security protections, parental controls, and other services that depend upon the DNS".[10]

Since DoH cannot be used under some circumstances, like captive portals, web browsers like Firefox can be configured to fallback to insecure DNS.[11]

Oblivious DNS-over-HTTPS

Oblivious DoH is an Internet Draft proposing a protocol extension to ensure no single DoH server is aware of both the client's IP address and their message contents. All requests are passed via a proxy, hiding clients' addresses from the resolver itself, and are encrypted to hide their contents from the proxy.[12][13][14][15]

Deployment scenarios

DoH is used for recursive DNS resolution by DNS resolvers. Resolvers (DoH clients) must have access to a DoH server hosting a query endpoint.[7]

Three usage scenarios are common:

  • Using a DoH implementation within an application: Some browsers have a built-in DoH implementation and can thus perform queries by bypassing the operating system's DNS functionality. A drawback is that an application may not inform the user if it skips DoH querying, either by misconfiguration or lack of support for DoH.
  • Installing a DoH proxy on the name server in the local network: In this scenario client systems continue to use traditional (port 53 or 853) DNS to query the name server in the local network, which will then gather the necessary replies via DoH by reaching DoH-servers in the Internet. This method is transparent to the end user.
  • Installing a DoH proxy on a local system: In this scenario, operating systems are configured to query a locally running DoH proxy. In contrast to the previously mentioned method, the proxy needs to be installed on each system wishing to use DoH, which might require a lot of effort in larger environments.

Software support

Operating systems

Apple

Apple's iOS 14 and macOS 11 released in late 2020 support both DoH and DoT protocols.[16][17]

Windows

In November 2019, Microsoft announced plans to implement support for encrypted DNS protocols in Microsoft Windows, beginning with DoH.[18] In May 2020, Microsoft released Windows 10 Insider Preview Build 19628 that included initial support for DoH[19] along with instructions on how to enable it via registry and command line interface.[20] Windows 10 Insider Preview Build 20185 added graphical user interface for specifying a DoH resolver.[21] DoH support is not planned for Windows 10 21H2.[22]

Windows 11 has DoH support.[23]

Recursive DNS resolvers

See also: Comparison_of_DNS_server_software § Feature_matrix

BIND

BIND 9, an open source DNS resolver from Internet Systems Consortium added native support for DoH in version 9.17.10.[24]

PowerDNS

DNSdist, an open source DNS proxy/load balancer from PowerDNS, added native support for DoH in version 1.4.0 in April 2019.[25]

Unbound

Unbound, an open source DNS resolver created by NLnet Labs, has supported DoH since version 1.12.0, released in October 2020.[26][27] It first implemented support for DNS encryption using the alternative DoT protocol much earlier, starting with version 1.4.14, released in December 2011.[28][29] Unbound runs on most operating systems, including distributions of Linux, MacOS, and Windows.

Web browsers

See also: Comparison_of_web_browsers § Protocol_support

Google Chrome

DNS over HTTPS is available in Google Chrome 83 for Windows and macOS, configurable via the settings page. When enabled, and the operating system is configured with a supported DNS server, Chrome will upgrade DNS queries to be encrypted.[30] It is also possible to manually specify a preset or custom DoH server to use within the user interface.[31]

In September 2020, Google Chrome for Android began staged rollout of DNS over HTTPS. Users can configure a custom resolver or disable DNS over HTTPS in settings.[32]

Microsoft Edge

Microsoft Edge supports DNS over HTTPS, configurable via the settings page. When enabled, and the operating system is configured with a supported DNS server, Edge will upgrade DNS queries to be encrypted. It is also possible to manually specify a preset or custom DoH server to use within the user interface.[33]

Mozilla Firefox

An example of DNS over HTTPS usage on Firefox 89

In 2018, Mozilla partnered with Cloudflare to deliver DoH for Firefox users that enable it (known as Trusted Recursive Resolver).[34] On February 25, 2020, Firefox started enabling DNS over HTTPS for all US-based users, relying on Cloudflare's resolver by default.[35]

Opera

Opera supports DoH, configurable via the browser settings page.[36] By default, DNS queries are sent to Cloudflare servers.[37]

Public DNS servers

Main article: Public recursive name server

DNS over HTTPS server implementations are already available free of charge by some public DNS providers.[38]

Implementation considerations

Many issues with how to properly deploy DoH are still being resolved by the internet community including, but not limited to:

  • Stopping third-parties from analyzing DNS traffic for security purposes
  • Disruption of DNS-level parental controls and content filters
  • Split DNS in enterprise networks[citation needed]
  • CDN localization[citation needed]

Analysis of DNS traffic for security purposes

DoH can impede analysis and monitoring of DNS traffic for cybersecurity purposes; the 2019 DDoS worm Godlua used DoH to mask connections to its command-and-control server.[39][40]

In January 2021, NSA warned enterprises against using external DoH resolvers because they prevent DNS query filtering, inspection, and audit. Instead, NSA recommends configuring enterprise-owned DoH resolvers and blocking all known external DoH resolvers.[41]

Disruption of content filters

DoH has been used to bypass parental controls which operate at the (unencrypted) standard DNS level; Circle, a parental control router which relies on DNS queries to check domains against a blocklist, blocks DoH by default due to this.[42] However, there are DNS providers that offer filtering and parental controls along with support for DoH by operating DoH servers.[43][44][45][46][47]

The Internet Service Providers Association (ISPA)—a trade association representing British ISPs—and the also British body Internet Watch Foundation have criticized Mozilla, developer of the Firefox web browser, for supporting DoH, as they believe that it will undermine web blocking programs in the country, including ISP default filtering of adult content, and mandatory court-ordered filtering of copyright violations. The ISPA nominated Mozilla for its "Internet Villain" award for 2019 (alongside the EU Directive on Copyright in the Digital Single Market, and Donald Trump), "for their proposed approach to introduce DNS-over-HTTPS in such a way as to bypass UK filtering obligations and parental controls, undermining internet safety standards in the UK." Mozilla responded to the allegations by the ISPA, arguing that it would not prevent filtering, and that they were "surprised and disappointed that an industry association for ISPs decided to misrepresent an improvement to decades-old internet infrastructure".[48][49] In response to the criticism, the ISPA apologized and withdrew the nomination.[50][51] Mozilla subsequently stated that DoH will not be used by default in the British market until further discussion with relevant stakeholders, but stated that it "would offer real security benefits to UK citizens".[52]

Inconsistent DoH deployment

Some DoH deployments are not an end-to-end encrypted, but rather only hop-to-hop encrypted because DoH is deployed only on a subset of connections. There are following types of connections:

  • from client device (computer or a tablet) to local DNS forwarder (home or office router)
  • from DNS forwarder to recursive DNS resolver (typically at the ISP)
  • from recursive DNS resolver to authoritative DNS resolver (usually located in a data center)

Every connection in the chain needs to support DoH for maximum security.

See also

References

  1. ^ a b Chirgwin, Richard (14 Dec 2017). "IETF protects privacy and helps net neutrality with DNS over HTTPS". The Register. Archived from the original on 14 December 2017. Retrieved 2018-03-21.
  2. ^ "DNS-over-HTTPS | Public DNS | Google Developers". Google Developers. Archived from the original on 2018-03-20. Retrieved 2018-03-21.
  3. ^ Cimpanu, Catalin (2018-03-20). "Mozilla Is Testing "DNS over HTTPS" Support in Firefox". BleepingComputer. Archived from the original on 2018-03-20. Retrieved 2018-03-21.
  4. ^ ""A long-overdue technological shift toward online privacy": Firefox encrypts domain names. Google to follow". What’s New in Publishing | Digital Publishing News. 2020-02-26. Archived from the original on 2020-02-26. Retrieved 2020-02-26.
  5. ^ Claburn, Thomas (2020-05-20). "Google rolls out pro-privacy DNS-over-HTTPS support in Chrome 83... with a handy kill switch for corporate IT". The Register. Retrieved 2021-02-03.
  6. ^ Hoffman, P; McManus, P. "RFC 8484 - DNS Queries over HTTPS". datatracker.ietf.org. Archived from the original on 2018-12-12. Retrieved 2018-05-20.
  7. ^ a b Hoffman, P; McManus, P. "draft-ietf-doh-dns-over-https-08 - DNS Queries over HTTPS". datatracker.ietf.org. Archived from the original on 2018-04-25. Retrieved 2018-05-20.
  8. ^ "Experimenting with same-provider DNS-over-HTTPS upgrade". Chromium Blog. Archived from the original on 2019-09-12. Retrieved 2019-09-13.
  9. ^ Deckelmann, Selena. "What's next in making Encrypted DNS-over-HTTPS the Default". Future Releases. Archived from the original on 2019-09-14. Retrieved 2019-09-13.
  10. ^ "About". Encrypted DNS Deployment Initiative. Archived from the original on 2019-12-04. Retrieved 2019-09-13.
  11. ^ Improving DNS Privacy in Firefox
  12. ^ McManus, Patrick; Wood, Christopher; Kinnear, Eric; Pauly, Tommy. "Oblivious DNS Over HTTPS". tools.ietf.org. Retrieved 2021-03-17.
  13. ^ Singanamalla, Sudheesh; Chunhapanya, Suphanat; Vavruša, Marek; Verma, Tanya; Wu, Peter; Fayed, Marwan; Heimerl, Kurtis; Sullivan, Nick; Wood, Christopher (2020). "Oblivious DNS over HTTPS (ODoH): A Practical Privacy Enhancement to DNS". arXiv:2011.10121 [cs.CR].
  14. ^ Goodin, Dan (2020-12-08). "Cloudflare, Apple, and others back a new way to make the Internet more private". Ars Technica. Retrieved 2021-03-14.
  15. ^ "Cloudflare and Apple design a new privacy-friendly internet protocol". TechCrunch. Retrieved 2021-03-17.
  16. ^ June 2020, Anthony Spadafora 29 (29 June 2020). "Apple devices will get encrypted DNS in iOS 14 and macOS 11". TechRadar. Archived from the original on 2020-07-01. Retrieved 2020-07-01.{{cite web}}: CS1 maint: numeric names: authors list (link)
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  18. ^ Gallagher, Sean (2019-11-19). "Microsoft says yes to future encrypted DNS requests in Windows". Ars Technica. Archived from the original on 2019-11-19. Retrieved 2019-11-20.
  19. ^ "Announcing Windows 10 Insider Preview Build 19628". 13 May 2020. Archived from the original on 18 May 2020. Retrieved 13 May 2020.
  20. ^ "Windows Insiders can now test DNS over HTTPS". Archived from the original on 15 May 2020. Retrieved 7 July 2020.
  21. ^ Brinkmann, Martin (6 August 2020). "Windows 10 build 20185 comes with encrypted DNS settings - gHacks Tech News". gHacks Tech News. Retrieved 2020-08-06.{{cite web}}: CS1 maint: url-status (link)
  22. ^ Blog, Windows Experience (2021-07-15). "Introducing the next feature update to Windows 10: 21H2". Windows Experience Blog. Retrieved 2021-09-02.
  23. ^ "How to Configure and Use DNS-Over-HTTPS (DoH) in Windows 11". Appuals.com. 2021-07-28. Retrieved 2021-10-20.
  24. ^ Boldariev, Artem (17 February 2021). "BIND Implements DoH". ISC web site. Internet Systems Consortium. Retrieved 17 February 2021.
  25. ^ "dnsdist 1.4.0-alpha2 with DNS over HTTPS support". PowerDNS Blog. 2019-04-26. Retrieved 2021-05-10.
  26. ^ Wijngaards, Wouter (8 October 2020). "Unbound 1.12.0 released". NLnet Labs. Retrieved 24 October 2020. {{cite web}}: |archive-date= requires |archive-url= (help)
  27. ^ Dolmans, Ralph (9 October 2020). "DNS-over-HTTPS in Unbound". The NLnet Labs Blog. Retrieved 24 October 2020. {{cite web}}: |archive-date= requires |archive-url= (help)
  28. ^ Wijngaards, Wouter. "Unbound 1.4.14 release". Unbound-users mailing list. Retrieved 24 October 2020. {{cite web}}: |archive-date= requires |archive-url= (help)
  29. ^ Wijngaards, Wouter. "dns over ssl support". GitHub. Retrieved 24 October 2020. {{cite web}}: |archive-date= requires |archive-url= (help)
  30. ^ "DNS over HTTPS (aka DoH)". Archived from the original on 27 May 2020. Retrieved 23 May 2020.
  31. ^ "Chrome 83: rollout of DNS over HTTPS (Secure DNS) begins". 20 May 2020. Archived from the original on 1 June 2020. Retrieved 20 July 2020.
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  33. ^ "How to enable DNS-over-HTTPS (DoH) in Windows 10". BleepingComputer. Retrieved 2021-01-23.
  34. ^ Trusted Recursive Resolver
  35. ^ Deckelmann, Selena. "Firefox continues push to bring DNS over HTTPS by default for US users". The Mozilla Blog. Archived from the original on 2020-05-27. Retrieved 2020-05-28.
  36. ^ "Changelog for 67". Retrieved 23 August 2020.
  37. ^ "Here's how to enable DoH in each browser, ISPs be damned". ZDNet. Archived from the original on 9 June 2020. Retrieved 28 May 2020.
  38. ^ "DNS over HTTPS Implementations". GitHub. 2018-04-27. Archived from the original on 2018-04-02. Retrieved 2018-04-27.
  39. ^ Cimpanu, Catalin. "DNS-over-HTTPS causes more problems than it solves, experts say". ZDNet. Archived from the original on 2019-11-08. Retrieved 2019-11-19.
  40. ^ Cimpanu, Catalin. "First-ever malware strain spotted abusing new DoH (DNS over HTTPS) protocol". ZDNet. Archived from the original on 2019-10-27. Retrieved 2019-11-19.
  41. ^ Goodin, Dan (2021-01-15). "The NSA warns enterprises to beware of third-party DNS resolvers". Ars Technica. Retrieved 2021-03-17.
  42. ^ "Managing encrypted DNS connections (DNS over TLS, DNS over HTTPS) with Circle". Circle Support Center. Retrieved 2020-07-07.
  43. ^ Gallagher, Sean (16 November 2017). "New Quad9 DNS service blocks malicious domains for everyone". Ars Technica. Retrieved 14 November 2021. The system blocks domains associated with botnets, phishing attacks, and other malicious Internet hosts.
  44. ^ Inc, CleanBrowsing. "Parental Control with DNS over TLS Support". CleanBrowsing. Retrieved 2020-08-20. {{cite web}}: |last= has generic name (help)
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  46. ^ blockerDNS. "blockerDNS - Products". blockerdns.com. Retrieved 2020-08-20.
  47. ^ "Protect your privacy with DNS-over-TLS on SafeDNS". SafeDNS. Retrieved 2020-08-20.
  48. ^ Cimpanu, Catalin. "UK ISP group names Mozilla 'Internet Villain' for supporting 'DNS-over-HTTPS'". ZDNet. Archived from the original on 2019-07-05. Retrieved 2019-07-05.
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  50. ^ "British ISPs fight to make the web LESS secure". IT PRO. Retrieved 2019-09-14.
  51. ^ Patrawala, Fatema (2019-07-11). "ISPA nominated Mozilla in the "Internet Villain" category for DNS over HTTPs push, withdrew nominations and category after community backlash". Packt Hub. Archived from the original on 2019-12-04. Retrieved 2019-09-14.
  52. ^ Hern, Alex (2019-09-24). "Firefox: 'no UK plans' to make encrypted browser tool its default". The Guardian. ISSN 0261-3077. Archived from the original on 2019-09-28. Retrieved 2019-09-29.
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