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{{
{{Security protocol}}
The '''Domain Name System Security Extensions''' ('''DNSSEC''')
==Overview==
The original design of the Domain Name System did not include any security features. It was conceived only as a scalable distributed system. The Domain Name System Security Extensions (DNSSEC) attempt to add security, while maintaining [[backward compatibility]]. {{IETF RFC|3833}} of 2004 documents some of the known threats to the DNS, and their solutions in DNSSEC.
DNSSEC was designed to protect applications using DNS from accepting forged or manipulated DNS data, such as that created by [[DNS cache poisoning]]. All answers from DNSSEC protected zones are [[digital signature|digitally signed]].<ref>{{Cite IETF |last1=Herzberg |first1=Amir |last2=Shulman |first2=Haya |year=2014 |title=Retrofitting Security into Network Protocols: The Case of DNSSEC |url=https://ieeexplore.ieee.org/document/6756846 |journal=IEEE Internet Computing |volume=18 |issue=1 |pages=66–71 |doi=10.1109/MIC.2014.14 |s2cid=12230888 |issn=1089-7801}}</ref> By checking the digital signature, a DNS resolver is able to check if the information is identical (i.e. unmodified and complete) to the information published by the zone owner and served on an authoritative DNS server. While protecting IP addresses is the immediate concern for many users, DNSSEC can protect any data published in the DNS, including text records (TXT) and mail exchange records (MX), and can be used to bootstrap other security systems that publish references to cryptographic certificates stored in the DNS such as Certificate Records ([[CERT record]]s, {{IETF RFC|4398}}), [[Secure Shell|SSH]] fingerprints ([[SSHFP record|SSHFP]], {{IETF RFC|4255}}), [[IPSec]] public keys (IPSECKEY, {{IETF RFC| 4025}}), [[Transport Layer Security|TLS]] Trust Anchors ([[TLSA]], {{IETF RFC | 6698 }}), or Encrypted Client Hello (SVCB/HTTPS records for ECH <ref>{{cite IETF | url=https://datatracker.ietf.org/doc/
DNSSEC ''does not'' provide confidentiality of data; in particular, all DNSSEC responses are authenticated but not encrypted. DNSSEC ''does not'' protect against [[denial of service|DoS]] attacks directly, though it indirectly provides some benefit (because signature checking allows the use of potentially untrustworthy parties).{{citation needed|date=February 2013}}
Other standards (not DNSSEC) are used to secure bulk data (such as a [[DNS zone transfer]]) sent between DNS servers. As documented in {{IETF RFC | 4367 }}, some users and developers make false assumptions about DNS names, such as assuming that a company's common name plus ".com" is always its ___domain name. DNSSEC cannot protect against false assumptions; it can only authenticate that the data is truly from or not available from the ___domain owner.{{citation needed|date=February 2013}}
The DNSSEC specifications (called ''DNSSEC-bis'') describe the current DNSSEC protocol in great detail. See {{IETF RFC | 4033 }}, {{ IETF RFC | 4034}}, and {{ IETF RFC | 4035}}. With the publication of these new RFCs (March 2005), an earlier RFC, {{ IETF RFC | 2535 }} has become obsolete. The full set of RFCs that specify DNSSEC are collected in {{IETF RFC|9364}}, which is also [[Request_for_Comments#Best_Current_Practice|BCP]] 237.
It is widely believed<ref>Interview with Dan Kaminsky on DNSSEC (25 Jun 2009) [https://web.archive.org/web/20090628074022/http://searchsecurity.techtarget.com/news/interview/0,289202,sid14_gci1360143,00.html# Kaminsky interview: DNSSEC addresses cross-organizational trust and security]</ref> that securing the DNS is critically important for securing the Internet as a whole, but deployment of DNSSEC specifically has been hampered ({{As of|2010|January|22}}) by several difficulties:
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| 1 || [[RSA (algorithm)|RSA]]/[[MD5]] || || {{no|Must Not Implement}} || {{no|Must Not Implement}}
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| 3 || [[Digital Signature Algorithm|DSA]]/[[SHA-1]] || {{IETF RFC |
|-
| 5 || RSA/SHA-1 || {{IETF RFC | 3110}}|| {{no2|Not Recommended}} || {{yes|Required}}
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| 12 || [[GOST]] [[GOST (hash function)|R 34.10-2001]] || {{IETF RFC |5933}}|| {{no|Must Not Implement}} || {{Okay|Optional}}
|-
| 13 || [[Elliptic Curve DSA|ECDSA]] P-256/[[SHA-2|SHA-256]] || rowspan="2" | {{ IETF RFC | 6605}}|| {{yes|Required}} || {{yes|Required}}
|-
| 14 || ECDSA P-384/[[SHA-2|SHA-384]] || {{Okay|Optional}} || {{partial|Recommended}}
|-
| 15 || [[Ed25519]] || rowspan="2" | {{IETF RFC |8080 }}|| {{partial|Recommended}} || {{partial|Recommended}}
|-
| 16 || [[Curve448|Ed448]] || {{Okay|Optional}} || {{partial|Recommended}}
|-
|17
| [[SM3 (hash function)|SM2SM3]]
| {{IETF RFC | 9563}}
| {{okay|Optional}}
| {{okay|Optional}}
|-
|23
|[[GOST]] R 34.10-2012
| {{IETF RFC | 9558}}
| {{okay|Optional}}
| {{okay|Optional}}
|}
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| 2 || [[SHA-256]] || {{ IETF RFC |4509 }}|| {{yes|Required}} || {{yes|Required}}
|-
| 3 || [[GOST]] [[GOST (hash function)|R 34.
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| 4 || [[SHA-384]] || {{ IETF RFC |6605}}|| {{okay|Optional}} || {{partial|Recommended}}
|-
|5
|[[GOST]] [[Streebog|R 34.11-2012]]
| {{IETF RFC | 9563}}
| {{okay|Optional}}
| {{okay|Optional}}
|-
|6
| SM3
| {{IETF RFC | 9558}}
| {{okay|Optional}}
| {{okay|Optional}}
|}
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The new protocols will enable additional assurances and constraints for the traditional model based on [[public key infrastructure]]. They will also enable ___domain holders to assert certificates for themselves, without reference to third-party [[certificate authority|certificate authorities]].
Support for DNSSEC stapled certificates was enabled in [[Google Chrome]] 14,<ref>{{cite web|url=http://www.imperialviolet.org/2011/06/16/dnssecchrome.html|title=ImperialViolet|access-date=2011-11-26}}</ref> but was later removed.<ref>{{cite web|url=https://git.chromium.org/gitweb/?p=chromium/chromium.git;a=commit;h=6a7172345e72d755d99c095eb3d4768f0f585344|title=chromium git|access-date=2013-03-09}}</ref> For [[Mozilla Firefox]], support was provided by an add-on<ref>{{cite web|url=https://www.dnssec-validator.cz/|title=DNSSEC/TLSA Validator}}</ref>
==History==
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Unfortunately, the IETF RFC 2535 specification had very significant problems scaling up to the full Internet; by 2001 it became clear that this specification was unusable for large networks. In normal operation DNS servers often get out of sync with their parents. This isn't usually a problem, but when DNSSEC is enabled, this out-of-sync data could have the effect of a serious self-created denial of service. The original DNSSEC required a complex six-message protocol and a lot of data transfers to perform key changes for a child (DNS child zones had to send all of their data up to the parent, have the parent sign each record, and then send those signatures back to the child for the child to store in a SIG record). Also, public key changes could have absurd effects; for example, if the ".com" zone changed its public key, it would have to send 22 million records (because it would need to update all of the signatures in all of its children). Thus, DNSSEC as defined in RFC 2535 could not scale up to the Internet.
The IETF fundamentally modified DNSSEC, which is called ''DNSSEC-bis'' when necessary to distinguish it from the original DNSSEC approach of RFC 2535. This new version uses "delegation signer (DS) resource records" to provide an additional level of indirection at delegation points between a parent and child zone. In the new approach, when a child's master public key changes, instead of having six messages for every record in the child, there is one simple message: the child sends the new public key to its parent (signed, of course). Parents simply store one master public key for each child; this is much more practical. This means that a little data is pushed to the parent, instead of massive amounts of data being exchanged between the parent and children. This does mean that clients have to do a little more work when verifying keys. More specifically, verifying a DNS zone's KEY RRset requires two signature verification operations instead of the one required by RFC 2535 (there is no impact on the number of signatures verified for other types of RRsets). Most view this as a small price to pay, since it makes DNSSEC deployment more practical. The new version is published in RFC4033-4035.
In January 2024, a "KeyTrap" denial-of-service attack was announced for all specification-respecting DNSSEC resolvers. The DNSSEC specification (RFC4033-4035) specifies that a resolver, when receiving a signed packet from the upstream, should try ''all'' keys with the correct "tag" on ''all'' signatures until one of the combinations successfully verifies. By putting many keys with the same "tag" and many signatures corresponding to that "tag" in a packet, the researchers can slow down a resolver by a factor of 2 million. In response, resolvers began to place limits on the amount of verification errors, key tag collisions, and hash calculations.<ref>{{cite web |title=The KeyTrap Denial-of-Service Algorithmic Complexity Attacks on DNS Version: January 2024 |author1=Elias Heftrig|author2= Haya Schulmann |author3= Niklas Vogel |author4= Michael Waidne |url=https://www.athene-center.de/fileadmin/content/PDF/Keytrap_2401.pdf |website=ATHENE}} ([https://www.athene-center.de/en/keytrap press release])</ref>
==Authenticating NXDOMAIN responses and NSEC==
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===Early deployments===
Early adopters include [[Brazil]] ([[.br]]), [[Bulgaria]] ([[.bg]]), [[Czech Republic]] ([[.cz]]), [[Namibia]] ([[.na]])<ref>{{cite web |first=Patrick |last=Myles | title=GNSO Activity Update for ccNSO Council meeting |date=25 September 2014 | url=https://ccnso.icann.org/
IANA publicly tested a sample signed root since June 2007. During this period prior to the production signing of the root, there were also several alternative trust anchors. The IKS Jena introduced one on January 19, 2006,<ref>[http://www.ripe.net/ripe/maillists/archives/dns-wg/2006/msg00053.html dns-wg archive: Signed zones list] {{webarchive |url=https://web.archive.org/web/20070305102531/http://www.ripe.net/ripe/maillists/archives/dns-wg/2006/msg00053.html |date=March 5, 2007 }}</ref> the [[Internet Systems Consortium]] introduced another on March 27 of the same year,<ref>[https://www.isc.org/node/62 ISC Launches DLV registry to kick off worldwide DNSSEC deployment] {{webarchive |url=https://web.archive.org/web/20081118020616/https://www.isc.org/node/62 |date=November 18, 2008 }}</ref> while [[ICANN]] themselves announced a third on February 17, 2009.<ref>[https://itar.iana.org/ Interim Trust Anchor Repository]</ref>
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|author=Sean Michael Kerner
|access-date=2008-09-27
}}</ref> On June 23, 2010, 13 registrars were listed as offering DNSSEC records for .ORG domains.<ref>{{cite web
|url=http://www.pir.org/get/registrars?order=field_dnssec_value&sort=desc
|title=.ORG Registrar List — with DNSSEC enabled at the top
|access-date=2010-06-23
|archive-date=2010-06-12
|archive-url=https://web.archive.org/web/20100612212156/http://pir.org/get/registrars?order=field_dnssec_value&sort=desc
|url-status=dead
}}</ref>
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====DNSSEC support====
{{See also|Public_recursive_name_server#Notable_public_DNS_service_operators}}
Google's [[Google Public DNS|public recursive DNS]] server enabled DNSSEC validation on May 6, 2013.<ref>[https://security.googleblog.com/2013/03/google-public-dns-now-supports-dnssec.html Google Public DNS Now Supports DNSSEC Validation] Google Code Blog, 1 June 2013</ref>
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The [[Quad9|Quad9 public recursive DNS]] has performed DNSSEC validation on its main 9.9.9.9 address since it was established on May 11, 2016. Quad9 also provides an alternate service which does not perform DNSSEC validation, principally for debugging.<ref>{{Cite web|url=https://www.quad9.net/faq/|title=Quad9 FAQ|website=Quad9|access-date=July 7, 2018}}</ref>
===Deployment in infrastructure===
In September 2023, Microsoft announced it would utilize DNSSEC (via [[DNS-based Authentication of Named Entities|DANE]]) to verify the authenticity of certificates during SMTP communications.<ref>{{Cite web |title=Implementing Inbound SMTP DANE with DNSSEC for Exchange Online Mail Flow |url=https://techcommunity.microsoft.com/t5/exchange-team-blog/implementing-inbound-smtp-dane-with-dnssec-for-exchange-online/ba-p/3939694 |access-date=2024-05-28 |website=TECHCOMMUNITY.MICROSOFT.COM |language=en}}</ref>
== Reception ==
[[Geoff Huston (scientist)|Geoff Hutson]] has argued that DNSSEC deployment should be given up.<ref>{{Cite web |last=Huston |first=Geoff |date=2024-05-28 |title=Calling time on DNSSEC? |url=https://blog.apnic.net/2024/05/28/calling-time-on-dnssec/ |access-date=2024-05-28 |website=APNIC Blog |language=en-US}}</ref>
==IETF publications==
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==Tools==
[[File:Unbound 1.22.0 screenshot.webp|thumb|upright=1.2|Usage of DNSSEC in [[Unbound (DNS server)|Unbound]] (checking validation with <code>unbound-host</code>)]]
DNSSEC deployment requires software on the server and client side. Some of the tools that support DNSSEC include:
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==External links==
* [https://www.dnssec.net/ DNSSEC]
* [https://web.archive.org/web/20031008105543/http://www.ietf.org/html.charters/dnsext-charter.html DNSEXT] DNS Extensions [[IETF Working Group]]
* [https://web.archive.org/web/20190429202558/http://dnssec-tools.org/ DNSSEC-Tools Project]
{{Authority control}}
[[Category:Internet Standards]]
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