EDNS Client Subnet

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EDNS Client Subnet (ECS) is an option in the Extension Mechanisms for DNS that allows a recursive DNS resolver to specify the subnetwork for the host or client on whose behalf it is making a DNS query. This is generally intended to help speed up the delivery of data from content delivery networks (CDN), by allowing better use of DNS-based load balancing to select a service address near the client when the client computer is not necessarily near the recursive resolver. [1] [2]

Contents

When an authoritative name server receives a DNS query, it takes advantage of ECS DNS extension to resolve the hostname to a CDN which is geolocationally near to the client IP's subnet, hence the client makes further requests to a nearby CDN, thereby reducing latency. The EDNS client subnet mechanism is specified in RFC   7871.

Privacy and security implications

Because ECS provides client network information to upstream resolver, the extension reveals some information about the client's location that the resolver would not otherwise be able to deduce. [3] Security researchers have suggested that ECS could be used to conduct internet surveillance. [3] ECS may also be exploited to perform selective DNS cache poisoning attacks intended to only re-route specific clients to a poisoned DNS record. [3]

Controversy over lack of support

The owner of self-serve web archiving tool Archive.today has expressed concern over Cloudflare 1.1.1.1 not passing the contents of this field on to the authoritative DNS server for Archive.today, and has in response configured the site's resolver to consider Cloudflare DNS requests invalid—effectively blocking 1.1.1.1 from resolving the website DNS records. [4]

The owner of the site believes 1.1.1.1 too often routes recursive DNS requests in a non-geographically-optimal way, causing poorer connectivity than if the feature was available at all times. [4]

Cloudflare CEO Matthew Prince cited privacy concerns as reason for 1.1.1.1 to not support ECS. [5]

Related Research Articles

The Domain Name System (DNS) is a hierarchical and distributed naming system for computers, services, and other resources in the Internet or other Internet Protocol (IP) networks. It associates various information with domain names assigned to each of the associated entities. Most prominently, it translates readily memorized domain names to the numerical IP addresses needed for locating and identifying computer services and devices with the underlying network protocols. The Domain Name System has been an essential component of the functionality of the Internet since 1985.

A name server is a computer application that implements a network service for providing responses to queries against a directory service. It translates an often humanly meaningful, text-based identifier to a system-internal, often numeric identification or addressing component. This service is performed by the server in response to a service protocol request.

<span class="mw-page-title-main">Proxy server</span> Computer server that makes and receives requests on behalf of a user

In computer networking, a proxy server is a server application that acts as an intermediary between a client requesting a resource and the server providing that resource. It improves privacy, security, and performance in the process.

The Domain Name System Security Extensions (DNSSEC) are a suite of extension specifications by the Internet Engineering Task Force (IETF) for securing data exchanged in the Domain Name System (DNS) in Internet Protocol (IP) networks. The protocol provides cryptographic authentication of data, authenticated denial of existence, and data integrity, but not availability or confidentiality.

<span class="mw-page-title-main">Content delivery network</span> Layer in the internet ecosystem addressing bottlenecks

A content delivery network, or content distribution network (CDN), is a geographically distributed network of proxy servers and their data centers. The goal is to provide high availability and performance by distributing the service spatially relative to end users. CDNs came into existence in the late 1990s as a means for alleviating the performance bottlenecks of the Internet as the Internet was starting to become a mission-critical medium for people and enterprises. Since then, CDNs have grown to serve a large portion of the Internet content today, including web objects, downloadable objects, applications, live streaming media, on-demand streaming media, and social media sites.

DNS spoofing, also referred to as DNS cache poisoning, is a form of computer security hacking in which corrupt Domain Name System data is introduced into the DNS resolver's cache, causing the name server to return an incorrect result record, e.g. an IP address. This results in traffic being diverted to any computer that the attacker chooses.

Round-robin DNS is a technique of load distribution, load balancing, or fault-tolerance provisioning multiple, redundant Internet Protocol service hosts, e.g., Web server, FTP servers, by managing the Domain Name System's (DNS) responses to address requests from client computers according to an appropriate statistical model.

This article presents a comparison of the features, platform support, and packaging of many independent implementations of Domain Name System (DNS) name server software.

Extension Mechanisms for DNS (EDNS) is a specification for expanding the size of several parameters of the Domain Name System (DNS) protocol which had size restrictions that the Internet engineering community deemed too limited for increasing functionality of the protocol. The first set of extensions was published in 1999 by the Internet Engineering Task Force as RFC 2671, also known as EDNS0 which was updated by RFC 6891 in 2013 changing abbreviation slightly to EDNS(0).

<span class="mw-page-title-main">OpenDNS</span> Domain name system provided by Cisco using closed-source software

OpenDNS is an American company providing Domain Name System (DNS) resolution services—with features such as phishing protection, optional content filtering, and DNS lookup in its DNS servers—and a cloud computing security product suite, Umbrella, designed to protect enterprise customers from malware, botnets, phishing, and targeted online attacks. The OpenDNS Global Network processes an estimated 100 billion DNS queries daily from 85 million users through 25 data centers worldwide.

<span class="mw-page-title-main">Fast flux</span> DNS evasion technique against origin server fingerprinting.

Fast flux is a domain name system (DNS) based evasion technique used by cyber criminals to hide phishing and malware delivery websites behind an ever-changing network of compromised hosts acting as reverse proxies to the backend botnet master—a bulletproof autonomous system. It can also refer to the combination of peer-to-peer networking, distributed command and control, web-based load balancing and proxy redirection used to make malware networks more resistant to discovery and counter-measures.

DNSCurve is a proposed secure protocol for the Domain Name System (DNS), designed by Daniel J. Bernstein. It encrypts and authenticates DNS packets between resolvers and authoritative servers.

Google Public DNS is a Domain Name System (DNS) service offered to Internet users worldwide by Google. It functions as a recursive name server. Google Public DNS was announced on December 3, 2009, in an effort described as "making the web faster and more secure." As of 2018, it is the largest public DNS service in the world, handling over a trillion queries per day. Google Public DNS is not related to Google Cloud DNS, which is a DNS hosting service.

DNSCrypt is a network protocol that authenticates and encrypts Domain Name System (DNS) traffic between the user's computer and recursive name servers. DNSCrypt wraps unmodified DNS traffic between a client and a DNS resolver in a cryptographic construction, preventing eavesdropping and forgery by a man-in-the-middle.

Content delivery network interconnection (CDNI) is a set of interfaces and mechanisms required for interconnecting two independent content delivery networks (CDNs) that enables one to deliver content on behalf of the other. Interconnected CDNs offer many benefits, such as footprint extension, reduced infrastructure costs, higher availability, etc., for content service providers (CSPs), CDNs, and end users. Among its many use cases, it allows small CDNs to interconnect and provides services for CSPs that allows them to compete against the CDNs of global CSPs.

A public recursive name server is a name server service that networked computers may use to query the Domain Name System (DNS), the decentralized Internet naming system, in place of name servers operated by the local Internet service provider (ISP) to which the devices are connected. Reasons for using these services include:

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 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. In February 2020, Firefox switched to DNS over HTTPS by default for users in the United States.

DNS over TLS (DoT) is a network security protocol for encrypting and wrapping Domain Name System (DNS) queries and answers via the Transport Layer Security (TLS) protocol. The goal of the method is to increase user privacy and security by preventing eavesdropping and manipulation of DNS data via man-in-the-middle attacks. The well-known port number for DoT is 853.

<span class="mw-page-title-main">Quad9</span> Global public recursive DNS resolver based in Switzerland

Quad9 is a global public recursive DNS resolver that aims to protect users from malware and phishing. Quad9 is operated by the Quad9 Foundation, a Swiss public-benefit, not-for-profit foundation with the purpose of improving the privacy and cybersecurity of Internet users, headquartered in Zürich. Quad9 is entirely subject to Swiss privacy law, and the Swiss government extends that protection of the law to Quad9's users throughout the world, regardless of citizenship or country of residence.

1.1.1.1 is a free Domain Name System (DNS) service by the American company Cloudflare in partnership with APNIC. The service functions as a recursive name server, providing domain name resolution for any host on the Internet. The service was announced on April 1, 2018. On November 11, 2018, Cloudflare announced a mobile application of their 1.1.1.1 service for Android and iOS. On September 25, 2019, Cloudflare released WARP, an upgraded version of their original 1.1.1.1 mobile application.

References

  1. ↑ "How it works". A Faster Internet. Archived from the original on 2018-03-28. Retrieved 2018-03-27.{{cite web}}: CS1 maint: unfit URL (link)
  2. ↑ "EDNS Client Subnet (ECS) Guidelines | Public DNS | Google Developers". Google Developers. Retrieved 2018-04-02.
  3. 1 2 3 Kintis P, Nadji Y, Dagon D, Farrell M, Antonakakis M (June 2016). "Understanding the Privacy Implications of ECS" (PDF). Detection of Intrusions and Malware, and Vulnerability Assessment. Lecture Notes in Computer Science. Vol. 9721. Springer. pp. 343–353. doi:10.1007/978-3-319-40667-1_17. ISBN   978-3-319-40667-1.
  4. 1 2 @archiveis (July 16, 2018). ""Having to do" is not so direct here" (Tweet) – via Twitter. Absence of EDNS and massive mismatch (not only on AS/Country, but even on the continent level) of where DNS and related HTTP requests come from causes so many troubles so I consider EDNS-less requests from Cloudflare as invalid.
  5. ↑ Matthew Prince (4 May 2019). "Comment by Matthew Prince on Hacker News". Hacker News. Retrieved 4 October 2021. We don't block archive.is or any other domain via 1.1.1.1. Doing so, we believe, would violate the integrity of DNS and the privacy and security promises we made to our users when we launched the service. Archive.is's authoritative DNS servers return bad results to 1.1.1.1 when we query them. I've proposed we just fix it on our end but our team, quite rightly, said that too would violate the integrity of DNS and the privacy and security promises we made to our users when we launched the service. The archive.is owner has explained that he returns bad results to us because we don't pass along the EDNS subnet information. This information leaks information about a requester's IP and, in turn, sacrifices the privacy of users. This is especially problematic as we work to encrypt more DNS traffic since the request from Resolver to Authoritative DNS is typically unencrypted. We're aware of real world examples where nationstate actors have monitored EDNS subnet information to track individuals, which was part of the motivation for the privacy and security policies of 1.1.1.1. EDNS IP subsets can be used to better geolocate responses for services that use DNS-based load balancing. However, 1.1.1.1 is delivered across Cloudflare's entire network that today spans 180 cities. We publish the geolocation information of the IPs that we query from. That allows any network with less density than we have to properly return DNS-targeted results. For a relatively small operator like archive.is, there would be no loss in geo load balancing fidelity relying on the location of the Cloudflare PoP in lieu of EDNS IP subnets. We are working with the small number of networks with a higher network/ISP density than Cloudflare (e.g., Netflix, Facebook, Google/YouTube) to come up with an EDNS IP Subnet alternative that gets them the information they need for geolocation targeting without risking user privacy and security. Those conversations have been productive and are ongoing. If archive.is has suggestions along these lines, we'd be happy to consider them.


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