RFC 8976
Message Digest for DNS Zones
Message Digest for DNS Zones 🎀
Okay bestie, let's get the paperwork out of the way first 💅 This is RFC 8976, published by the IETF (Internet Engineering Task Force) in February 2021. It's a Standards Track document, and its ISSN is 2070-1721 🧾 The authors are D. Wessels and P. Barber from Verisign, M. Weinberg from Amazon, W. Kumari from Google, and W. Hardaker from USC/ISI. Nothing in the title block says it obsoletes or updates another RFC, so it's standing on its own 🌈
Abstract ✨
This doc describes a protocol and a brand-new DNS Resource Record that gives you a cryptographic message digest over DNS zone data at rest 🔐 The ZONEMD Resource Record carries the digest inside the zone itself. When you pair it with DNSSEC, ZONEMD lets recipients verify the zone contents for data integrity and origin authenticity, which means the received zone data matches the published data no matter how it got transmitted and received 💖 Without DNSSEC, ZONEMD just acts like a checksum, guarding only against unintentional changes 🧚
ZONEMD does not replace DNSSEC, and it isn't trying to 🙅♀️ DNSSEC protects individual RRsets (DNS data with fine granularity), while ZONEMD protects a zone's data as a whole. That holds whether the data is consumed by authoritative name servers, recursive name servers, or any other application 💜
Real talk though: as specified here, ZONEMD is impractical for large, dynamic zones because of the time and resources the digest calculation takes 😭 The good news is that the ZONEMD record is extensible, so new digest schemes can be added later to support large, dynamic zones 🦋
Status of This Memo 🌸
This is an Internet Standards Track document.
This document is a product of the Internet Engineering Task Force (IETF). It represents the consensus of the IETF community. It has received public review and has been approved for publication by the Internet Engineering Steering Group (IESG). Further information on Internet Standards is available in Section 2 of RFC 7841.
Info about the current status of this document, any errata, and how to give feedback on it can be found at https://www.rfc-editor.org/info/rfc8976 🔗
Copyright Notice 📜
Copyright (c) 2021 IETF Trust and the persons identified as the document authors. All rights reserved.
This document is subject to BCP 78 and the IETF Trust's Legal Provisions Relating to IETF Documents (https://trustee.ietf.org/license-info) in effect on the date of publication of this document. Please review these documents carefully, as they describe your rights and restrictions with respect to this document. Code Components extracted from this document must include Simplified BSD License text as described in Section 4.e of the Trust Legal Provisions and are provided without warranty as described in the Simplified BSD License. 🫶
Table of Contents 🗂️
1. Introduction
1.1. Motivation
1.2. Alternative Approaches
1.3. Design Overview
1.4. Use Cases
1.4.1. Root Zone
1.4.2. Providers, Secondaries, and Anycast
1.4.3. Response Policy Zones
1.4.4. Centralized Zone Data Service
1.4.5. General Purpose Comparison Check
1.5. Terminology
2. The ZONEMD Resource Record
2.1. Non-apex ZONEMD Records
2.2. ZONEMD RDATA Wire Format
2.2.1. The Serial Field
2.2.2. The Scheme Field
2.2.3. The Hash Algorithm Field
2.2.4. The Digest Field
2.3. ZONEMD Presentation Format
2.4. ZONEMD Example
2.5. Including ZONEMD RRs in a Zone
3. Calculating the Digest
3.1. Add ZONEMD Placeholder
3.2. Optionally, Sign the Zone
3.3. Scheme-Specific Processing
3.3.1. The SIMPLE Scheme
3.3.1.1. SIMPLE Scheme Inclusion/Exclusion Rules
3.3.1.2. SIMPLE Scheme Digest Calculation
3.4. Update ZONEMD RR
4. Verifying Zone Digest
5. IANA Considerations
5.1. ZONEMD RRtype
5.2. ZONEMD Scheme
5.3. ZONEMD Hash Algorithms
6. Security Considerations
6.1. Using Zone Digest without DNSSEC
6.2. Attacks against the Zone Digest
6.3. Use of Multiple ZONEMD Hash Algorithms
6.4. DNSSEC Timing Considerations
6.5. Attacks Utilizing ZONEMD Queries
6.6. Resilience and Fragility
7. Performance Considerations
7.1. SIMPLE SHA384
8. Privacy Considerations
9. References
9.1. Normative References
9.2. Informative References
Appendix A. Example Zones with Digests
A.1. Simple EXAMPLE Zone
A.2. Complex EXAMPLE Zone
A.3. EXAMPLE Zone with Multiple Digests
A.4. The URI.ARPA Zone
A.5. The ROOT-SERVERS.NET Zone
Appendix B. Implementation Status
B.1. Authors' Implementation
B.2. Shane Kerr's Implementation
B.3. NIC Chile Lab's Implementation
Acknowledgments
Authors' Addresses1. Introduction ✨
Okay so, in the DNS, a zone is the collection of authoritative resource records (RRs) that share a common origin ([RFC8499]) 🌷 Zones are often stored as files in the so-called "master file format" ([RFC1034]). They usually get spread around name servers with the zone transfer (AXFR) ([RFC5936]) and incremental zone transfer (IXFR) ([RFC1995]) protocols. They can also travel outside the DNS with any file transfer protocol, like FTP, HTTP, or rsync, or even as email attachments 📨 The wild part is that there's currently no standard way to compute a hash or message digest for a stand-alone zone 😳
This document specifies an RR type that gives a cryptographic message digest of the data in a zone 💅 It lets a receiver check the zone's integrity and authenticity when it's used together with DNSSEC. The digest RR lives inside the zone itself, so you can verify the zone no matter how it was transmitted 🧚 The digest is computed over the wire format of the zone data in a canonical ordering, which means it doesn't care about presentation-format stuff like whitespace, capitalization, and comments ✨
This specification is OPTIONAL to implement by both publishers and consumers of zone data. 🫶
1.1. Motivation
The main reason for this protocol enhancement is wanting to verify the data integrity and origin authenticity of a stand-alone zone, no matter how it's transmitted 🔍 A consumer of zone data should be able to verify that it's the same as what the zone operator published.
BUT (and this is a big but) integrity and authenticity can only be assured when the zone is signed 🔏 DNSSEC gives three strong security guarantees that matter for this protocol:
- whether or not to expect DNSSEC records in the zone,
- whether or not to expect a ZONEMD record in a signed zone, and
- whether or not the ZONEMD record has been altered since it was signed.
A secondary motivation is to provide the equivalent of a checksum, so a zone recipient can catch unintended changes and operational errors like accidental truncation 🍓
1.2. Alternative Approaches
One approach to stopping data tampering and corruption is to secure the distribution channel 🛡️ The DNS already has a bunch of features used for channel security. Probably the most widely used is DNS transaction signatures (TSIGs) ([RFC8945]). A TSIG uses shared secret keys and a message digest to protect individual query and response messages. It's generally used to authenticate and validate UPDATE ([RFC2136]), AXFR ([RFC5936]), and IXFR ([RFC1995]) messages.
DNS Request and Transaction Signatures (SIG(0)) ([RFC2931]) is another protocol extension that authenticates individual DNS transactions. SIG records normally cover specific RR types, but SIG(0) is used to sign an entire DNS message. Unlike TSIG, SIG(0) uses public key cryptography instead of shared secrets 🔑
The Transport Layer Security protocol suite also provides channel security. The DPRIVE Working Group is in the process of specifying DNS Zone Transfer-over-TLS ([DPRIVE-XFR-OVER-TLS]). You can also easily picture zones being distributed over HTTPS-enabled web servers, as well as DNS-over-HTTPS ([RFC8484]) 🌐
Unfortunately, the protections these channel security techniques provide are (in practice) ephemeral and aren't kept after the data transfer is done 😤 They make sure the client gets the data from the expected server and that the data isn't modified in transit. But they don't guarantee the server sends the data as originally published, and they don't offer any way to verify data that's read after the transmission is complete. For example, a name server loading saved zone data on restart can't guarantee the on-disk data hasn't been modified. That could happen from accidental file corruption or an incomplete save of the file ([DISK-FULL-FAILURE]). For these reasons, it's preferable to protect the integrity of the data itself 💖
Why not just rely on DNSSEC, which gives certain data security guarantees? For signed zones, a recipient could validate all of the signed RRsets. Denial-of-existence records also prove that RRsets haven't been added or removed. However, delegations (non-apex NS records) aren't signed by DNSSEC, and neither are any glue records. ZONEMD protects the integrity of delegation, glue, and other records that DNSSEC doesn't otherwise cover 🎯 Also, zones that use NSEC3 with Opt-Out ([RFC5155]) are open to names being removed or added between the signed nodes. DNSSEC mainly protects consumers of DNS response messages, while this protocol protects consumers of zones 🧁
There are existing tools and protocols for data security, like OpenPGP ([RFC4880]) and S/MIME ([RFC8551]). In fact, the internic.net site publishes Pretty Good Privacy (PGP) signatures alongside the root zone and other files available there. But that's a detached signature with no strong association to the zone file other than its timestamp 🤷♀️ Attached signatures are possible, of course, but they necessarily change the format of the file being distributed. A zone signed with OpenPGP or S/MIME no longer looks like a DNS zone and couldn't be loaded directly into a name server. And once it's loaded, the signature data is lost, so it can't be propagated further 💀
Desire for data security in DNS zones was envisioned as far back as 1997, honestly iconic 👑 [RFC2065] is an obsoleted specification of the first generation DNSSEC Security Extensions. It describes a zone transfer signature, identified as the AXFR SIG, which is similar to the technique proposed by this document. That is, it proposes ordering all (signed) RRsets in a zone, hashing their contents, and then signing the zone hash. The AXFR SIG is only described for use during zone transfers, and it didn't account for validating zone data distributed outside of the DNS. Its successor, [RFC2535], also drops the AXFR SIG while introducing an IXFR SIG at the same time. (Note: RFC 2535 was obsoleted by [RFC4033], [RFC4034], and [RFC4035].) 🦋
1.3. Design Overview
okay so this doc is literally defining a brand new Resource Record type, ZONEMD (type 63) 💅, that carries a message digest of a zone's content 🎀. The digest gets calculated at zone publication time. If the zone is signed with DNSSEC, any modifications of the digest can be detected 👀. The digest calculation and DNSSEC signing are kinda twins: both need data processed in a well-defined order and format. It may be possible to run DNSSEC signing and digest calculation in parallel ✨.
The zone digest is built for zones that update infrequently 🦋. As written here, the digest gets recalculated over the entire zone content every time the zone is updated. This spec does not give you an efficient way to update the digest for incremental changes, bestie 🙈. It is, however, extensible, so future schemes can be defined to support efficient incremental digest updates 💜.
Verification of a zone digest is expected to be implemented in name server software 🧚. So a name server can check the zone data it was given and refuse to serve a zone that fails verification 🛡️. For signed zones, the name server needs a trust anchor to do DNSSEC validation. For signed non-root zones, the name server may need to send queries to validate a chain of trust. Digest verification could also be performed externally 🌈.
1.4. Use Cases
1.4.1. Root Zone
the root zone ([InterNIC]) is one of the most widely distributed DNS zones on the Internet 🌍. It's served by more than 1000 separate instances ([ROOT-SERVERS]) at the time of this writing. Plus, lots of organizations configure their own name servers to serve the root zone locally 🏠. The reasons for doing that include privacy and reduced access time 🔒. [RFC8806] describes one way to do this. As the root zone spreads beyond its traditional deployment boundaries, verifying that the zone contents are complete becomes way more important 💀.
1.4.2. Providers, Secondaries, and Anycast
Since its very early days, the DNS developers recognized how important secondary name servers and service diversity are 🍓. But modern DNS service has complex provisioning, with multiple third-party providers ([RFC8901]) and hundreds of anycast instances ([RFC3258]) 🌸. Instead of a simple primary-to-secondary zone distribution system, today you can have multiple levels, multiple parties, and multiple protocols all involved in distributing zone data. That complexity creates new places for problems to pop up 😭. The zone digest protects the integrity of data flowing through all of those systems 🫶.
1.4.3. Response Policy Zones
A Response Policy Zone (RPZ) is "a mechanism to introduce a customized policy in Domain Name System servers, so that recursive resolvers return possibly modified results" ([RPZ]) 🔥. The policy info is carried inside specially constructed DNS zones. A number of companies provide RPZ feeds, which get consumed by name server and firewall products. RPZs can be signed with DNSSEC, but the data isn't queried directly, so it would not be subject to DNSSEC validation 🙃.
1.4.4. Centralized Zone Data Service
ICANN operates the Centralized Zone Data Service ([CZDS]), which is a repository of top-level domain zone files 📂. Users who've been granted access can then download zone data. Adding a zone digest to these files would give CZDS users assurance that the data wasn't modified between origination and retrieval ✨. Note that ZONEMD could be added to zone data supplied to CZDS without it having to be present in the zone data served by production name servers 💅. That works because the digest is inherently attached to the specific copy of the zone 🎀.
1.4.5. General Purpose Comparison Check
Since the zone digest calculation doesn't depend on presentation format, it could be used to compare multiple copies of a zone received from different sources, or copies generated by different processes 🦋. In this case, it works as a checksum, and it can be useful even for unsigned zones 🌈.
1.5. Terminology
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and "OPTIONAL" in this document are to be interpreted as described in BCP 14 [RFC2119] [RFC8174] when, and only when, they appear in all capitals, as shown here 📣.
The terms Private Use, Reserved, Unassigned, and Specification Required are to be interpreted as defined in [RFC8126] 📚.
2. The ZONEMD Resource Record
This section walks through the ZONEMD Resource Record: its fields, wire format, and presentation format 💖. The Type value for the ZONEMD RR is 63 🔢. The ZONEMD RR is class independent. Its RDATA consists of four fields: Serial, Scheme, Hash Algorithm, and Digest 🫧.
2.1. Non-apex ZONEMD Records
This document specifies ZONEMD RRs located at the zone apex. Non-apex ZONEMD RRs aren't forbidden, but they have no meaning in this specification 🤷♀️. Non-apex ZONEMD RRs MUST NOT be used for verification 🚫.
During digest calculation, non-apex ZONEMD RRs are treated as ordinary RRs. They get digested as is, and the RR is not replaced by a placeholder RR 🌸.
Unless explicitly stated otherwise, "ZONEMD" always refers to apex records throughout this document 💅.
2.2. ZONEMD RDATA Wire Format
The ZONEMD RDATA wire format is encoded like this, and yes, the diagram is giving everything 🎀:
1 1 1 1 1 1 1 1 1 1 2 2 2 2 2 2 2 2 2 2 3 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Serial |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Scheme |Hash Algorithm | |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ |
| Digest |
/ /
/ /
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+2.2.1. The Serial Field
The Serial field is a 32-bit unsigned integer in network byte order 🔢. It's the serial number from the zone's SOA record ([RFC1035], Section 3.3.13) that the zone digest was generated for 📜.
It's included here to clearly bind the ZONEMD RR to a particular version of the zone's content 🔗. Without the serial number, a stand-alone ZONEMD digest has no obvious association to any particular instance of a zone 🤔.
2.2.2. The Scheme Field
The Scheme field is an 8-bit unsigned integer that identifies the methods by which data is collated and presented as input to the hashing function 🧩.
Herein, SIMPLE, with Scheme value 1, is the only standardized Scheme defined for ZONEMD records, and it MUST be supported by implementations 👑. The "ZONEMD Schemes" registry is further described in Section 5.
Scheme values 240-254 are allocated for Private Use 🔐.
2.2.3. The Hash Algorithm Field
The Hash Algorithm field is an 8-bit unsigned integer that identifies the cryptographic hash algorithm used to construct the digest 🔐.
Herein, SHA384 ([RFC6234]), with Hash Algorithm value 1, is the only standardized Hash Algorithm defined for ZONEMD records that MUST be supported by implementations 💜. When SHA384 is used, the size of the Digest field is 48 octets. The result of the SHA384 digest algorithm MUST NOT be truncated, so the entire 48-octet digest is published in the ZONEMD record 🫶.
SHA512 ([RFC6234]), with Hash Algorithm value 2, is also defined for ZONEMD records and SHOULD be supported by implementations ✨. When SHA512 is used, the size of the Digest field is 64 octets. The result of the SHA512 digest algorithm MUST NOT be truncated, so the entire 64-octet digest is published in the ZONEMD record 🌈.
Hash Algorithm values 240-254 are allocated for Private Use 🔐.
The "ZONEMD Hash Algorithms" registry is further described in Section 5 📚.
2.2.4. The Digest Field
The Digest field is a variable-length sequence of octets containing the output of the hash algorithm 🧁. Its length is determined by subtracting the fixed size of the Serial, Scheme, and Hash Algorithm fields from the RDATA size in the ZONEMD RR header 🧮.
The Digest field MUST NOT be shorter than 12 octets. Digests for the SHA384 and SHA512 hash algorithms specified here are never truncated. Digests for future hash algorithms MAY be truncated, but MUST NOT be truncated to a length that results in less than 96 bits (12 octets) of equivalent strength ⚠️. Main character energy, the digest has standards 💅.
Section 3 describes how to calculate the digest for a zone. Section 4 describes how to use the digest to verify the contents of a zone 🗺️.
2.3. ZONEMD Presentation Format
The presentation format of the RDATA portion goes like this 📝:
- The Serial field is represented as an unsigned decimal integer.
- The Scheme field is represented as an unsigned decimal integer.
- The Hash Algorithm field is represented as an unsigned decimal integer.
- The Digest is represented as a sequence of case-insensitive hexadecimal digits. Whitespace is allowed within the hexadecimal text 🫧.
2.4. ZONEMD Example
Here's a ZONEMD RR in presentation format, iykyk 🦋:
example.com. 86400 IN ZONEMD 2018031500 1 1 (
FEBE3D4CE2EC2FFA4BA99D46CD69D6D29711E55217057BEE
7EB1A7B641A47BA7FED2DD5B97AE499FAFA4F22C6BD647DE )2.5. Including ZONEMD RRs in a Zone
The zone operator picks an appropriate hash algorithm and scheme, then includes the calculated zone digest in the apex ZONEMD RRset 🎀. The zone operator MAY choose any of the defined hash algorithms and schemes, including the Private Use code points 🌸.
The ZONEMD RRset MAY contain multiple records to support algorithm agility ([BCP201]) 🔄. When multiple ZONEMD RRs are present, each MUST specify a unique Scheme and Hash Algorithm tuple 🙅♀️. It is RECOMMENDED that a zone include only one ZONEMD RR, unless the zone operator is in the process of transitioning to a new scheme or hash algorithm 💅.
3. Calculating the Digest
The algorithm described in this section is designed for the common case of offline DNSSEC signing 🌙. Slight deviations may be permitted or necessary in other situations, such as with unsigned zones or online DNSSEC signing 🌤️. Implementations that deviate from the described algorithm are advised to make sure it produces ZONEMD RRs, signatures, and denial-of-existence records that are identical to the ones generated by this procedure 🫶.
3.1. Add ZONEMD Placeholder 🧁
okay so before we do any digest math, we gotta clean up the apex first 🧹 any existing ZONEMD records (and their covering RRSIGs) sitting at the zone apex get deleted first. fresh start, no leftovers 💅
then, before we calculate the digest and before we sign with DNSSEC, we pop in one or more placeholder ZONEMD records at the zone apex 🎀 the reason is so the denial-of-existence records (NSEC, NSEC3) get created correctly if the zone is signed. ngl, if we skipped the placeholders, adding ZONEMD later would mean updating the Type Bit Maps field of any apex NSEC/NSEC3 RRs, and that would totally invalidate the digest value we just worked out 😭 not it!
when there are multiple ZONEMD RRs published in the zone, like during an algorithm rollover, each MUST specify a unique Scheme and Hash Algorithm tuple 👑 that's the rule, no exceptions, bestie.
it is RECOMMENDED that the TTL of the ZONEMD record match the TTL of the Start of Authority (SOA) 🌸 however, the TTL of the ZONEMD record may be safely ignored during verification in all cases, so don't stress about it 🫶
for the placeholder itself: the Serial field gets set to the current SOA Serial. the Scheme field gets the value for the collation scheme you picked, and the Hash Algorithm field gets the value for the hash algorithm you picked. and since apex ZONEMD records are excluded from the digest calculation, the value of the Digest field literally doesn't matter at this point 🙈
3.2. Optionally, Sign the Zone ✍️
once the placeholders are in, the zone may be signed with DNSSEC 💖 when the digest calculation is finished and the ZONEMD record gets updated, the signature(s) for the ZONEMD RRset MUST be recalculated and updated too 🔥 so the signer doesn't have to sign the placeholder record at this step. it's not required, but it's harmless to do it anyway, so you do you 💅
3.3. Scheme-Specific Processing 🦋
here's the tea: only the SIMPLE collation scheme is defined in this document 🍓 additional schemes may be defined in future updates to this document, so keep your eyes open 👀
3.3.1. The SIMPLE Scheme 💜
for SIMPLE, the digest is calculated over the zone as a whole 🌍 which means that changing even a single RR in the zone means you have to iterate over all the RRs in the zone to recalculate the digest. SIMPLE is a good choice for zones that are small and/or stable, but it's probably not the move for zones that are large and/or dynamic 😬
calculating a zone digest needs the RRs processed in a consistent format and ordering, so everyone's on the same page 📚 this spec uses DNSSEC's canonical on-the-wire RR format (without name compression) and ordering, as specified in Sections 6.1, 6.2, and 6.3 of [RFC4034]. the extra twist is that RRsets with the same owner name MUST be numerically ordered, in ascending order, by their numeric RR TYPE ✨ very particular, very iconic.
3.3.1.1. SIMPLE Scheme Inclusion/Exclusion Rules 🧐
when you're iterating over the records in the zone, these inclusion/exclusion rules apply:
- all records in the zone, including glue records, MUST be included, unless a later rule excludes them 🫧
- occluded data ([RFC5936], Section 3.5) MUST be included 🙌
- if there are duplicate RRs with the same owner, class, type, and RDATA, only one instance gets included ([RFC4034], Section 6.3), and the duplicates MUST be omitted 🗑️
- the placeholder apex ZONEMD RR(s) MUST NOT be included 🙅♀️
- if the zone is signed, DNSSEC RRs MUST be included, except:
- the RRSIG covering the apex ZONEMD RRset MUST NOT be included, because that RRSIG gets updated after all the digests have been calculated 🥹
3.3.1.2. SIMPLE Scheme Digest Calculation 🧮
a zone digest using the SIMPLE scheme is calculated by concatenating all the RRs in the zone, in the format and order from Section 3.3.1, subject to the inclusion/exclusion rules from Section 3.3.1.1, and then applying the chosen hash algorithm 💅 the math looks like this:
digest = hash( RR(1) | RR(2) | RR(3) | ... )where | denotes concatenation. easy peasy 🍰
3.4. Update ZONEMD RR 📝
the calculated zone digest gets inserted into the placeholder ZONEMD RR 🎀 if you're publishing multiple digests, repeat this for each one.
if the zone is signed with DNSSEC, the RRSIG record(s) covering the ZONEMD RRset MUST then be added or updated 🔏 and since the ZONEMD placeholder went in before signing, the zone already has the right denial-of-existence (NSEC, NSEC3) records. no extra drama 💖
Heads up, bestie: some DNSSEC implementations (especially "online signing") might update the SOA serial number whenever a new signature is made 😱 to keep the calculated digest safe, generating a ZONEMD signature MUST NOT also change the SOA serial number. the ZONEMD RR and the matching SOA MUST be published at the same time, period 🔥
4. Verifying Zone Digest 🔍
the recipient of a zone that has a ZONEMD RR checks the zone by calculating the digest, following these steps 💜
Note: If multiple ZONEMD RRs are present in the zone, e.g., during an algorithm rollover, a match using any one of the recipient's supported Schemes and Hash Algorithms is sufficient to verify the zone. The verifier MAY ignore a ZONEMD RR if its Scheme and Hash Algorithm violates local policy. 🫶
- The verifier MUST first figure out whether or not to expect DNSSEC records in the zone 🕵️♀️ by checking locally configured trust anchors and, if needed, querying for and validating Delegation Signer (DS) RRs in the parent zone, the verifier knows whether the zone should include DNSSEC keys and signatures. for zones where signatures aren't expected, or if DNSSEC validation isn't performed, digest verification continues at step 4 below.
- for zones where signatures are expected, the existence of the apex ZONEMD record MUST be validated 🧾 if the DNSSEC data proves the ZONEMD RRset does not exist, digest verification cannot happen. if the DNSSEC data proves the ZONEMD does exist but it's not found in the zone, digest verification MUST NOT be considered successful 💀
- for zones where signatures are expected, the SOA and ZONEMD RRsets MUST have valid signatures, chaining up to a trust anchor 🔗 if DNSSEC validation of the SOA or ZONEMD RRsets fails, digest verification MUST NOT be considered successful.
- when multiple ZONEMD RRs are present, each MUST specify a unique Scheme and Hash Algorithm tuple 👯♀️ if the ZONEMD RRset has more than one RR with the same Scheme and Hash Algorithm, digest verification for those ZONEMD RRs MUST NOT be considered successful.
- loop over all the apex ZONEMD RRs and do the following steps for each one 🔁
- a. the SOA Serial field MUST exactly match the ZONEMD Serial field 🎯 if they don't match, digest verification MUST NOT be considered successful with this ZONEMD RR.
- b. the Scheme field MUST be checked 🧩 if the verifier doesn't support the given scheme, verification MUST NOT be considered successful with this ZONEMD RR.
- c. the Hash Algorithm field MUST be checked 🔐 if the verifier doesn't support the given hash algorithm, verification MUST NOT be considered successful with this ZONEMD RR.
- d. the Digest field size MUST be checked 📏 if the size of the given Digest field is smaller than 12 octets, or if the size isn't equal to the size expected for the corresponding Hash Algorithm, verification MUST NOT be considered successful with this ZONEMD RR.
- e. the zone digest is computed over the zone data as described in Section 3.3, using the Scheme and Hash Algorithm for the current ZONEMD RR 🧠
- f. the computed digest is compared to the received digest ⚖️ if the two match, verification is considered successful. otherwise, verification MUST NOT be considered successful for this ZONEMD RR.
every time zone verification runs, the verifier SHOULD report the status as either successful or unsuccessful 📣 and when it's unsuccessful, the verifier SHOULD report the reason(s) that verification didn't succeed 🫠
5. IANA Considerations 🏛️
5.1. ZONEMD RRtype 🎀
this document defines a new DNS RR type, ZONEMD 🥳 its value, 63, was allocated by IANA from the "Resource Record (RR) TYPEs" subregistry of the "Domain Name System (DNS) Parameters" registry:
Type: ZONEMD
Value: 63
Meaning: Message Digest Over Zone Data
Reference: [RFC8976]5.2. ZONEMD Scheme 🌈
IANA made a brand new subregistry in the "Domain Name System (DNS) Parameters" registry, and here are the details 📋
Registry Name: ZONEMD Schemes
Registration Procedure: Specification Required
Reference: [RFC8976] +=========+=========================+==========+===========+
| Value | Description | Mnemonic | Reference |
+=========+=========================+==========+===========+
| 0 | Reserved | | [RFC8976] |
+---------+-------------------------+----------+-----------+
| 1 | Simple ZONEMD collation | SIMPLE | [RFC8976] |
+---------+-------------------------+----------+-----------+
| 2-239 | Unassigned | | |
+---------+-------------------------+----------+-----------+
| 240-254 | Private Use | N/A | [RFC8976] |
+---------+-------------------------+----------+-----------+
| 255 | Reserved | | [RFC8976] |
+---------+-------------------------+----------+-----------+Table 1: ZONEMD Scheme Registry 💚
5.3. ZONEMD Hash Algorithms 🧁
IANA also made a new subregistry in the "Domain Name System (DNS) Parameters" registry for hash algorithms 🔐
Registry Name: ZONEMD Hash Algorithms
Registration Procedure: Specification Required
Reference: [RFC8976] +=========+=============+==========+===========+
| Value | Description | Mnemonic | Reference |
+=========+=============+==========+===========+
| 0 | Reserved | | [RFC8976] |
+---------+-------------+----------+-----------+
| 1 | SHA-384 | SHA384 | [RFC8976] |
+---------+-------------+----------+-----------+
| 2 | SHA-512 | SHA512 | [RFC8976] |
+---------+-------------+----------+-----------+
| 3-239 | Unassigned | | |
+---------+-------------+----------+-----------+
| 240-254 | Private Use | N/A | [RFC8976] |
+---------+-------------+----------+-----------+
| 255 | Reserved | | [RFC8976] |
+---------+-------------+----------+-----------+Table 2: ZONEMD Hash Algorithms Registry 💚
6. Security Considerations 🛡️
6.1. Using Zone Digest without DNSSEC 🚨
Serious moment, bestie: users of ZONEMD with unsigned zones are advised that it provides no real protection against attacks 😭 zone digests can be used without DNSSEC, but that only protects against accidental zone corruption, like transmission errors and truncation. used this way, ZONEMD effectively just acts as a checksum. for zones not signed with DNSSEC, an attacker can make any zone modifications look valid by recomputing the Digest field of a ZONEMD RR 💀
6.2. Attacks against the Zone Digest 🕵️♀️
Okay so picture an attacker 😈 who wants to mess with zone content before the victim ever uses it. They have a few sneaky moves they could try, bestie.
First, they might pull a downgrade attack and try to push the zone toward being unsigned. That's why Section 4 has you figure out whether or not to expect DNSSEC signatures for the zone in step 1. 💅
Second, they could do a downgrade attack by yanking out one or more ZONEMD records. Here's the tea: that removal is only catchable with DNSSEC validation 🫠. This is exactly why Section 4 has you checking denial-of-existence proofs in step 2 and signature validation in step 3.
Third, they might mess with the Scheme, Hash Algorithm, or Digest fields of the ZONEMD record. Those edits are also only detectable with DNSSEC validation 😭.
As stated in [BCP201], cryptographic algorithms age and get weaker as cryptanalysis and computing power improve over time 🧮. So implementors and publishers of zone digests should plan ahead for algorithm agility on long timescales. Think of it as future-proofing your whole vibe 🔐✨.
6.3. Use of Multiple ZONEMD Hash Algorithms ✌️
When a zone publishes multiple ZONEMD RRs, the overall security is only as strong as the weakest hash algorithm in use. ngl, that's a big deal 💀. For this reason, Section 2 recommends publishing multiple ZONEMD RRs only when transitioning to a new scheme or hash algorithm. Once the transition is complete, the old scheme or hash algorithm should be removed from the ZONEMD RRset 🧹. No lingering old stuff allowed!
6.4. DNSSEC Timing Considerations ⏰
As with all DNSSEC signatures, the ability to validate a ZONEMD record's signature has a time limit ⌛. If the DS record(s) or trust anchors for the zone you're verifying are no longer available, the recipient cannot validate the ZONEMD RRset 😵. This could happen even if the ZONEMD signature is still current (not expired), because the zone's DS record(s) may have been withdrawn after a Key Signing Key (KSK) rollover 🔑.
Zones where it matters to validate a ZONEMD RRset through its entire signature validity period: the zone operator should make sure that KSK rollover timing takes this into consideration 📅. Plan your rollovers like a pro, bestie.
6.5. Attacks Utilizing ZONEMD Queries 📡
Nothing in this specification stops clients from making ZONEMD queries, or servers from answering them 🙌. That said, servers SHOULD NOT calculate zone digests dynamically (for each query), because doing that can be abused as a CPU resource exhaustion attack 🔥. Nobody wants a server that's totally cooked from doing math on every request.
ZONEMD responses could also be used in a distributed denial-of-service amplification attack 🌪️. The ZONEMD RR is moderately sized, kinda like the DS RR 🎀. A single ZONEMD RR adds approximately 65 to 95 octets to a DNS response for the digest types defined here. Other RR types, like DNS Public Key (DNSKEY), can cause even bigger amplification effects 👀.
6.6. Resilience and Fragility 🧱
Okay, this one's a little bit of a plot twist. ZONEMD is used to detect incomplete or corrupted zone data before anyone uses it, which makes things more resilient because corrupt data never gets used 🛡️. But it also brings in some denial-of-service fragility, because good data in a zone can become unavailable if some other data is missing or corrupt 😬. Publishers and consumers of zones with ZONEMD records should be aware of these trade-offs 🧐.
Here's the thing: while the goal is to secure the zone data, misconfigurations or implementation bugs are generally indistinguishable from intentional tampering. They could lead to service failures when verification runs automatically 🙈.
Zone publishers may want to deploy ZONEMD gradually, perhaps by using one of the Private Use hash algorithm code points listed in Section 5.3 🦋. Similarly, recipients may want to initially configure verification failures only as a warning, and later as an error once they've gained experience and confidence with the feature 🌸. Start soft, then level up!
7. Performance Considerations ⚡
This section is here to make zone publishers aware of the performance requirements and implications of including ZONEMD RRs in a zone 🧮💜.
7.1. SIMPLE SHA384 🏎️
As mentioned previously, the SIMPLE scheme may be impractical for zones that are either large or highly dynamic 🐢. Zone publishers should carefully consider using ZONEMD in such zones, since it might make consumers of zone data (e.g., secondary name servers) spend resources on digest calculation 😩. For those use cases, it is recommended that ZONEMD only be used when digest calculation time is significantly less than propagation times and update intervals ⏱️.
The authors' implementation (Appendix B.1) includes an option to record and report CPU usage of its operation 📊. The software was used to generate digests for more than 800 Top-Level Domain (TLD) zones available from [CZDS] 🌍. The table below sums up the results for the SIMPLE scheme and SHA384 hash algorithm, grouped by zone size. The Rate column is the mean amount of time per RR to calculate the digest, running on commodity hardware in early 2020 💻.
+=====================+================+
| Zone Size (RRs) | Rate (msec/RR) |
+=====================+================+
| 10 - 99 | 0.00683 |
+---------------------+----------------+
| 100 - 999 | 0.00551 |
+---------------------+----------------+
| 1000 - 9999 | 0.00505 |
+---------------------+----------------+
| 10000 - 99999 | 0.00602 |
+---------------------+----------------+
| 100000 - 999999 | 0.00845 |
+---------------------+----------------+
| 1000000 - 9999999 | 0.0108 |
+---------------------+----------------+
| 10000000 - 99999999 | 0.0148 |
+---------------------+----------------+
Table 3For example, based on the table above, it takes approximately 0.13 seconds to calculate a SIMPLE SHA384 digest for a zone with 22,000 RRs, and about 2.5 seconds for a zone with 300,000 RRs 🚀.
These benchmarks try to emulate a worst-case scenario, and they take into account the time required to canonicalize the zone for processing 🧼. Each of the 800+ zones was measured three times and then averaged, with a different random sorting of the input data prior to each measurement 🎲. Very scientific, very iconic.
8. Privacy Considerations 🔒
Good news, bestie: this specification has no impact on user privacy 🫶✨.
9. References 📚
9.1. Normative References 💜
[RFC1034] Mockapetris, P., "Domain names - concepts and facilities",
STD 13, RFC 1034, DOI 10.17487/RFC1034, November 1987,
<https://www.rfc-editor.org/info/rfc1034>.
[RFC1035] Mockapetris, P., "Domain names - implementation and
specification", STD 13, RFC 1035, DOI 10.17487/RFC1035,
November 1987, <https://www.rfc-editor.org/info/rfc1035>.
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119,
DOI 10.17487/RFC2119, March 1997,
<https://www.rfc-editor.org/info/rfc2119>.
[RFC4034] Arends, R., Austein, R., Larson, M., Massey, D., and S.
Rose, "Resource Records for the DNS Security Extensions",
RFC 4034, DOI 10.17487/RFC4034, March 2005,
<https://www.rfc-editor.org/info/rfc4034>.
[RFC6234] Eastlake 3rd, D. and T. Hansen, "US Secure Hash Algorithms
(SHA and SHA-based HMAC and HKDF)", RFC 6234,
DOI 10.17487/RFC6234, May 2011,
<https://www.rfc-editor.org/info/rfc6234>.
[RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC
2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174,
May 2017, <https://www.rfc-editor.org/info/rfc8174>.9.2. Informative References 📚
Okay bestie, these are the extra reads 🤓 You don't need them to implement anything, but they're where the backstory lives: the older DNS security specs, the zone transfer protocols, and the tools people actually built and tested with. Here's the full list, copied exactly so you can go down any rabbit hole you want 🐇🕳️
[BCP201] Housley, R., "Guidelines for Cryptographic Algorithm
Agility and Selecting Mandatory-to-Implement Algorithms",
BCP 201, RFC 7696, November 2015.
<https://www.rfc-editor.org/info/bcp201>
[CZDS] Internet Corporation for Assigned Names and Numbers
(ICANN), "Centralized Zone Data Service", October 2018,
<https://czds.icann.org/>.
[DISK-FULL-FAILURE]
DENIC, "Background of the Partial Failure of the Name
Service for .de Domains", May 2010,
<https://web.archive.org/web/20100618032705/
https://www.denic.de/en/denic-in-dialogue/news/2733.html>.
[DNS-TOOLS]
"DNS tools for zone signature (file, pkcs11-hsm) and
validation, and zone digest (ZONEMD)", commit 489de21,
December 2020, <https://github.com/niclabs/dns-tools>.
[DPRIVE-XFR-OVER-TLS]
Toorop, W., Dickinson, S., Sahib, S., Aras, P., and A.
Mankin, "DNS Zone Transfer-over-TLS", Work in Progress,
Internet-Draft, draft-ietf-dprive-xfr-over-tls-05, 20
January 2021, <https://tools.ietf.org/html/draft-ietf-
dprive-xfr-over-tls-05>.
[InterNIC] InterNIC, "Index of ftp://rs.internic.net/", May 2018,
<ftp://ftp.internic.net/domain/>.
[LDNS-ZONE-DIGEST]
"Implementation of Message Digests for DNS Zones using the
ldns library", commit 71c0cd1, January 2021,
<https://github.com/verisign/ldns-zone-digest>.
[RFC1995] Ohta, M., "Incremental Zone Transfer in DNS", RFC 1995,
DOI 10.17487/RFC1995, August 1996,
<https://www.rfc-editor.org/info/rfc1995>.
[RFC2065] Eastlake 3rd, D. and C. Kaufman, "Domain Name System
Security Extensions", RFC 2065, DOI 10.17487/RFC2065,
January 1997, <https://www.rfc-editor.org/info/rfc2065>.
[RFC2136] Vixie, P., Ed., Thomson, S., Rekhter, Y., and J. Bound,
"Dynamic Updates in the Domain Name System (DNS UPDATE)",
RFC 2136, DOI 10.17487/RFC2136, April 1997,
<https://www.rfc-editor.org/info/rfc2136>.
[RFC2535] Eastlake 3rd, D., "Domain Name System Security
Extensions", RFC 2535, DOI 10.17487/RFC2535, March 1999,
<https://www.rfc-editor.org/info/rfc2535>.
[RFC2931] Eastlake 3rd, D., "DNS Request and Transaction Signatures
( SIG(0)s )", RFC 2931, DOI 10.17487/RFC2931, September
2000, <https://www.rfc-editor.org/info/rfc2931>.
[RFC3258] Hardie, T., "Distributing Authoritative Name Servers via
Shared Unicast Addresses", RFC 3258, DOI 10.17487/RFC3258,
April 2002, <https://www.rfc-editor.org/info/rfc3258>.
[RFC4033] Arends, R., Austein, R., Larson, M., Massey, D., and S.
Rose, "DNS Security Introduction and Requirements",
RFC 4033, DOI 10.17487/RFC4033, March 2005,
<https://www.rfc-editor.org/info/rfc4033>.
[RFC4035] Arends, R., Austein, R., Larson, M., Massey, D., and S.
Rose, "Protocol Modifications for the DNS Security
Extensions", RFC 4035, DOI 10.17487/RFC4035, March 2005,
<https://www.rfc-editor.org/info/rfc4035>.
[RFC4880] Callas, J., Donnerhacke, L., Finney, H., Shaw, D., and R.
Thayer, "OpenPGP Message Format", RFC 4880,
DOI 10.17487/RFC4880, November 2007,
<https://www.rfc-editor.org/info/rfc4880>.
[RFC5155] Laurie, B., Sisson, G., Arends, R., and D. Blacka, "DNS
Security (DNSSEC) Hashed Authenticated Denial of
Existence", RFC 5155, DOI 10.17487/RFC5155, March 2008,
<https://www.rfc-editor.org/info/rfc5155>.
[RFC5936] Lewis, E. and A. Hoenes, Ed., "DNS Zone Transfer Protocol
(AXFR)", RFC 5936, DOI 10.17487/RFC5936, June 2010,
<https://www.rfc-editor.org/info/rfc5936>.
[RFC8126] Cotton, M., Leiba, B., and T. Narten, "Guidelines for
Writing an IANA Considerations Section in RFCs", BCP 26,
RFC 8126, DOI 10.17487/RFC8126, June 2017,
<https://www.rfc-editor.org/info/rfc8126>.
[RFC8484] Hoffman, P. and P. McManus, "DNS Queries over HTTPS
(DoH)", RFC 8484, DOI 10.17487/RFC8484, October 2018,
<https://www.rfc-editor.org/info/rfc8484>.
[RFC8499] Hoffman, P., Sullivan, A., and K. Fujiwara, "DNS
Terminology", BCP 219, RFC 8499, DOI 10.17487/RFC8499,
January 2019, <https://www.rfc-editor.org/info/rfc8499>.
[RFC8551] Schaad, J., Ramsdell, B., and S. Turner, "Secure/
Multipurpose Internet Mail Extensions (S/MIME) Version 4.0
Message Specification", RFC 8551, DOI 10.17487/RFC8551,
April 2019, <https://www.rfc-editor.org/info/rfc8551>.
[RFC8806] Kumari, W. and P. Hoffman, "Running a Root Server Local to
a Resolver", RFC 8806, DOI 10.17487/RFC8806, June 2020,
<https://www.rfc-editor.org/info/rfc8806>.
[RFC8901] Huque, S., Aras, P., Dickinson, J., Vcelak, J., and D.
Blacka, "Multi-Signer DNSSEC Models", RFC 8901,
DOI 10.17487/RFC8901, September 2020,
<https://www.rfc-editor.org/info/rfc8901>.
[RFC8945] Dupont, F., Morris, S., Vixie, P., Eastlake 3rd, D.,
Gudmundsson, O., and B. Wellington, "Secret Key
Transaction Authentication for DNS (TSIG)", STD 93,
RFC 8945, DOI 10.17487/RFC8945, November 2020,
<https://www.rfc-editor.org/info/rfc8945>.
[ROOT-SERVERS]
Root Server Operators, "root-servers.org", July 2018,
<https://www.root-servers.org/>.
[RPZ] Wikipedia, "Response policy zone", May 2020,
<https://en.wikipedia.org/w/
index.php?title=Response_policy_zone&oldid=960043728>.
[ZONE-DIGEST-HACKATHON]
"Prototype implementation of ZONEMD for the IETF 102
hackathon", commit 76ad7a7, August 2019,
<https://github.com/shane-kerr/ZoneDigestHackathon>.
[ZONE-DIGEST-TESTS]
IETF, "RFC 8976 ZONEMD Test Cases", January 2021,
<https://trac.ietf.org/trac/dnsop/wiki/
RFC8976ZONEMDTestCases>.Appendix A. Example Zones with Digests 🧁
This appendix is basically a goodie bag 🎁 It has example zones with accurate ZONEMD records, so you can check whether your implementation gets the same answers. If you want even more test cases, the ZONEMD Tests Wiki ([ZONE-DIGEST-TESTS]), maintained by the IETF DNSOP Working Group, has you covered 💜
A.1. Simple EXAMPLE Zone 🌸
Here, the EXAMPLE zone is the chill starter pack: an SOA record, NS and glue records, and a ZONEMD record ✨
example. 86400 IN SOA ns1 admin 2018031900 (
1800 900 604800 86400 )
86400 IN NS ns1
86400 IN NS ns2
86400 IN ZONEMD 2018031900 1 1 (
c68090d90a7aed71
6bc459f9340e3d7c
1370d4d24b7e2fc3
a1ddc0b9a87153b9
a9713b3c9ae5cc27
777f98b8e730044c )
ns1 3600 IN A 203.0.113.63
ns2 3600 IN AAAA 2001:db8::63A.2. Complex EXAMPLE Zone 🦋
Okay, this one is giving chaos 😭 It's the EXAMPLE zone with duplicate RRs, an occluded RR, uppercase names, a wildcard, a multi-record RRset, a non-apex ZONEMD RR, and one out-of-zone RR. If your implementation survives this, it's that girl 👑
example. 86400 IN SOA ns1 admin 2018031900 (
1800 900 604800 86400 )
86400 IN NS ns1
86400 IN NS ns2
86400 IN ZONEMD 2018031900 1 1 (
a3b69bad980a3504
e1cffcb0fd6397f9
3848071c93151f55
2ae2f6b1711d4bd2
d8b39808226d7b9d
b71e34b72077f8fe )
ns1 3600 IN A 203.0.113.63
NS2 3600 IN AAAA 2001:db8::63
occluded.sub 7200 IN TXT "I'm occluded but must be digested"
sub 7200 IN NS ns1
duplicate 300 IN TXT "I must be digested just once"
duplicate 300 IN TXT "I must be digested just once"
foo.test. 555 IN TXT "out-of-zone data must be excluded"
UPPERCASE 3600 IN TXT "canonicalize uppercase owner names"
* 777 IN PTR dont-forget-about-wildcards
mail 3600 IN MX 20 MAIL1
mail 3600 IN MX 10 Mail2.Example.
sortme 3600 IN AAAA 2001:db8::5:61
sortme 3600 IN AAAA 2001:db8::3:62
sortme 3600 IN AAAA 2001:db8::4:63
sortme 3600 IN AAAA 2001:db8::1:65
sortme 3600 IN AAAA 2001:db8::2:64
non-apex 900 IN ZONEMD 2018031900 1 1 (
616c6c6f77656420
6275742069676e6f
7265642e20616c6c
6f77656420627574
2069676e6f726564
2e20616c6c6f7765 )A.3. EXAMPLE Zone with Multiple Digests 💅
Last but not least, the EXAMPLE zone with multiple ZONEMD records 🌈 It has both SHA384 and SHA512 digests using the SIMPLE scheme. It also includes ZONEMD records with Scheme and Hash Algorithm values in the private range (240-254). Heads up: those extra private-range digests are not verifiable, so don't panic when they don't check out 🙈
example. 86400 IN SOA ns1 admin 2018031900 (
1800 900 604800 86400 )
example. 86400 IN NS ns1.example.
example. 86400 IN NS ns2.example.
example. 86400 IN ZONEMD 2018031900 1 1 (
62e6cf51b02e54b9
b5f967d547ce4313
6792901f9f88e637
493daaf401c92c27
9dd10f0edb1c56f8
080211f8480ee306 )
example. 86400 IN ZONEMD 2018031900 1 2 (
08cfa1115c7b948c
4163a901270395ea
226a930cd2cbcf2f
a9a5e6eb85f37c8a
4e114d884e66f176
eab121cb02db7d65
2e0cc4827e7a3204
f166b47e5613fd27 )
example. 86400 IN ZONEMD 2018031900 1 240 (
e2d523f654b9422a
96c5a8f44607bbee )
example. 86400 IN ZONEMD 2018031900 241 1 (
e1846540e33a9e41
89792d18d5d131f6
05fc283e )
ns1.example. 3600 IN A 203.0.113.63
ns2.example. 86400 IN TXT "This example has multiple digests"
NS2.EXAMPLE. 3600 IN AAAA 2001:db8::63A.4. The URI.ARPA Zone
Okay, this one is the real deal 🌈 Here's the URI.ARPA zone as it was retrieved on 2021-01-21. Heads up: this sample was re-signed with unpublished keys, so the ZONEMD RR that got added also has a signature 🔐
uri.arpa. 3600 IN SOA sns.dns.icann.org. (
noc.dns.icann.org. 2018100702 10800 3600 1209600 3600 )
uri.arpa. 3600 IN RRSIG SOA 8 2 3600 (
20210217232440 20210120232440 37444 uri.arpa.
GzQw+QzwLDJr13REPGVmpEChjD1D2XlX0ie1DnWHpgaEw1E/dhs3lCN3+B
mHd4Kx3tffTRgiyq65HxR6feQ5v7VmAifjyXUYB1DZur1eP5q0Ms2ygCB3
byoeMgCNsFS1oKZ2LdzNBRpy3oace8xQn1SpmHGfyrsgg+WbHKCT1dY= )
uri.arpa. 86400 IN NS a.iana-servers.net.
uri.arpa. 86400 IN NS b.iana-servers.net.
uri.arpa. 86400 IN NS c.iana-servers.net.
uri.arpa. 86400 IN NS ns2.lacnic.net.
uri.arpa. 86400 IN NS sec3.apnic.net.
uri.arpa. 86400 IN RRSIG NS 8 2 86400 (
20210217232440 20210120232440 37444 uri.arpa.
M+Iei2lcewWGaMtkPlrhM9FpUAHXFkCHTVpeyrjxjEONeNgKtHZor5e4V4
qJBOzNqo8go/qJpWlFBm+T5Hn3asaBZVstFIYky38/C8UeRLPKq1hTTHAR
YUlFrexr5fMtSUAVOgOQPSBfH3xBq/BgSccTdRb9clD+HE7djpqrLS4= )
uri.arpa. 600 IN MX 10 pechora.icann.org.
uri.arpa. 600 IN RRSIG MX 8 2 600 (
20210217232440 20210120232440 37444 uri.arpa.
kQAJQivmv6A5hqYBK8h6Z13ESY69gmosXwKI6WE09I8RFetfrxr24ecdnY
d0lpnDtgNNSoHkYRSOoB+C4+zuJsoyAAzGo9uoWMWj97/2xeGhf3PTC9me
Q9Ohi6hul9By7OR76XYmGhdWX8PBi60RUmZ1guslFBfQ8izwPqzuphs= )
uri.arpa. 3600 IN DNSKEY 256 3 8 (
AwEAAbMxuFuLeVDuOwIMzYOTD/bTREjLflo7wOi6ieIJhqltEzgjNzmWJf
9kGwwDmzxU7kbthMEhBNBZNn84zmcyRSCMzuStWveL7xmqqUlE3swL8kLO
vdZvc75XnmpHrk3ndTyEb6eZM7slh2C63Oh6K8VR5VkiZAkEGg0uZIT3Nj
sF )
uri.arpa. 3600 IN DNSKEY 257 3 8 (
AwEAAdkTaWkZtZuRh7/OobBUFxM+ytTst+bCu0r9w+rEwXD7GbDs0pIMhM
enrZzoAvmv1fQxw2MGs6Ri6yPKfNULcFOSt9l8i6BVBLI+SKTY6XXeDUQp
SEmSaxohHeRPMQFzpysfjxINp/L2rGtZ7yPmxY/XRiFPSO0myqwGJa9r06
Zw9CHM5UDHKWV/E+zxPFq/I7CfPbrrzbUotBX7Z6Vh3Sarllbe8cGUB2UF
NaTRgwB0TwDBPRD5ER3w2Dzbry9NhbElTr7vVfhaGWeOGuqAUXwlXEg6Cr
NkmJXJ2F1Rzr9WHUzhp7uWxhAbmJREGfi2dEyPAbUAyCjBqhFaqglknvc= )
uri.arpa. 3600 IN DNSKEY 257 3 8 (
AwEAAenQaBoFmDmvRT+/H5oNbm0Tr5FmNRNDEun0Jpj/ELkzeUrTWhNpQm
ZeIMC8I0kZ185tEvOnRvn8OvV39B17QIdrvvKGIh2HlgeDRCLolhaojfn2
QM0DStjF/WWHpxJOmE6CIuvhqYEU37yoJscGAPpPVPzNvnL1HhYTaao1VR
YWQ/maMrJ+bfHg+YX1N6M/8MnRjIKBif1FWjbCKvsn6dnuGGL9oCWYUFJ3
DwofXuhgPyZMkzPc88YkJj5EMvbMH4wtelbCwC+ivx732l0w/rXJn0ciQS
OgoeVvDio8dIJmWQITWQAuP+q/ZHFEFHPlrP3gvQh5mcVS48eLX71Bq7c= )
uri.arpa. 3600 IN RRSIG DNSKEY 8 2 3600 (
20210217232440 20210120232440 12670 uri.arpa.
DBE2gkKAoxJCfz47KKxzoImN/0AKArhIVHE7TyTwy0DdRPo44V5R+vL6th
UxlQ1CJi2Rw0jwAXymx5Y3Q873pOEllH+4bJoIT4dmoBmPXfYWW7Clvw9U
PKHRP0igKHmCVwIeBYDTU3gfLcMTbR4nEWPDN0GxlL1Mf7ITaC2Ioabo79
Ip3M/MR8I3Vx/xZ4ZKKPHtLn3xUuJluPNanqJrED2gTslL2xWZ1tqjsAjJ
v7JnJo2HJ8XVRB5zBto0IaJ2oBlqcjdcQ/0VlyoM8uOy1pDwHQ2BJl7322
gNMHBP9HSiUPIOaIDNUCwW8eUcW6DIUk+s9u3GN1uTqwWzsYB/rA== )
uri.arpa. 3600 IN RRSIG DNSKEY 8 2 3600 (
20210217232440 20210120232440 30577 uri.arpa.
Kx6HwP4UlkGc1UZ7SERXtQjPajOF4iUvkwDj7MEG1xbQFB1KoJiEb/eiW0
qmSWdIhMDv8myhgauejRLyJxwxz8HDRV4xOeHWnRGfWBk4XGYwkejVzOHz
oIArVdUVRbr2JKigcTOoyFN+uu52cNB7hRYu7dH5y1hlc6UbOnzRpMtGxc
gVyKQ+/ARbIqGG3pegdEOvV49wTPWEiyY65P2urqhvnRg5ok/jzwAdMx4X
Gshiib7Ojq0sRVl2ZIzj4rFgY/qsSO8SEXEhMo2VuSkoJNiofVzYoqpxEe
GnANkIT7Tx2xJL1BWyJxyc7E8Wr2QSgCcc+rYL6IkHDtJGHy7TaQ== )
uri.arpa. 3600 IN ZONEMD 2018100702 1 1 (
0dbc3c4dbfd75777c12ca19c337854b1577799901307c482e9d91d5d15
cd934d16319d98e30c4201cf25a1d5a0254960 )
uri.arpa. 3600 IN RRSIG ZONEMD 8 2 3600 (
20210217232440 20210120232440 37444 uri.arpa.
QDo4XZcL3HMyn8aAHyCUsu/Tqj4Gkth8xY1EqByOb8XOTwVtA4ZNQORE1s
iqNqjtJUbeJPtJSbLNqCL7rCq0CzNNnBscv6IIf4gnqJZjlGtHO30ohXtK
vEc4z7SU3IASsi6bB3nLmEAyERdYSeU6UBfx8vatQDIRhkgEnnWUTh4= )
uri.arpa. 3600 IN NSEC ftp.uri.arpa. (
NS SOA MX RRSIG NSEC DNSKEY ZONEMD )
uri.arpa. 3600 IN RRSIG NSEC 8 2 3600 (
20210217232440 20210120232440 37444 uri.arpa.
dU/rXLM/naWd1+1PiWiYVaNJyCkiuyZJSccr91pJI673T8r3685B4ODMYF
afZRboVgwnl3ZrXddY6xOhZL3n9V9nxXZwjLJ2HJUojFoKcXTlpnUyYUYv
VQ2kj4GHAo6fcGCEp5QFJ2KbCpeJoS+PhKGRRx28icCiNT4/uXQvO2E= )
ftp.uri.arpa. 604800 IN NAPTR 0 0 "" "" (
"!^ftp://([^:/?#]*).*$!\\1!i" . )
ftp.uri.arpa. 604800 IN RRSIG NAPTR 8 3 604800 (
20210217232440 20210120232440 37444 uri.arpa.
EygekDgl+Lyyq4NMSEpPyOrOywYf9Y3FAB4v1DT44J3R5QGidaH8l7ZFjH
oYFI8sY64iYOCV4sBnX/dh6C1L5NgpY+8l5065Xu3vvjyzbtuJ2k6YYwJr
rCbvl5DDn53zAhhO2hL9uLgyLraZGi9i7TFGd0sm3zNyUF/EVL0CcxU= )
ftp.uri.arpa. 3600 IN NSEC http.uri.arpa. (
NAPTR RRSIG NSEC )
ftp.uri.arpa. 3600 IN RRSIG NSEC 8 3 3600 (
20210217232440 20210120232440 37444 uri.arpa.
pbP4KxevPXCu/bDqcvXiuBppXyFEmtHyiy0eAN5gS7mi6mp9Z9bWFjx/Ld
H9+6oFGYa5vGmJ5itu/4EDMe8iQeZbI8yrpM4TquB7RR/MGfBnTd8S+sjy
QtlRYG7yqEu77Vd78Fme22BKPJ+MVqjS0JHMUE/YUGomPkAjLJJwwGw= )
http.uri.arpa. 604800 IN NAPTR 0 0 "" "" (
"!^http://([^:/?#]*).*$!\\1!i" . )
http.uri.arpa. 604800 IN RRSIG NAPTR 8 3 604800 (
20210217232440 20210120232440 37444 uri.arpa.
eTqbWvt1GvTeXozuvm4ebaAfkXFQKrtdu0cEiExto80sHIiCbO0WL8UDa/
J3cDivtQca7LgUbOb6c17NESsrsVkc6zNPx5RK2tG7ZQYmhYmtqtfg1oU5
BRdHZ5TyqIXcHlw9Blo2pir1Y9IQgshhD7UOGkbkEmvB1Lrd0aHhAAg= )
http.uri.arpa. 3600 IN NSEC mailto.uri.arpa. (
NAPTR RRSIG NSEC )
http.uri.arpa. 3600 IN RRSIG NSEC 8 3 3600 (
20210217232440 20210120232440 37444 uri.arpa.
R9rlNzw1CVz2N08q6DhULzcsuUm0UKcPaGAWEU40tr81jEDHsFHNM+khCd
OI8nDstzA42aee4rwCEgijxJpRCcY9hrO1Ysrrr2fdqNz60JikMdarvU5O
0p0VXeaaJDfJQT44+o+YXaBwI7Qod3FTMx7aRib8i7istvPm1Rr7ixA= )
mailto.uri.arpa. 604800 IN NAPTR 0 0 "" "" (
"!^mailto:(.*)@(.*)$!\\2!i" . )
mailto.uri.arpa. 604800 IN RRSIG NAPTR 8 3 604800 (
20210217232440 20210120232440 37444 uri.arpa.
Ch2zTG2F1plEvQPyIH4Yd80XXLjXOPvMbiqDjpJBcnCJsV8QF7kr0wTLnU
T3dB+asQudOjPyzaHGwFlMzmrrAsszN4XAMJ6htDtFJdsgTMP/NkHhYRSm
Vv6rLeAhd+mVfObY12M//b/GGVTjeUI/gJaLW0fLVZxr1Fp5U5CRjyw= )
mailto.uri.arpa. 3600 IN NSEC urn.uri.arpa. (
NAPTR RRSIG NSEC )
mailto.uri.arpa. 3600 IN RRSIG NSEC 8 3 3600 (
20210217232440 20210120232440 37444 uri.arpa.
fQUbSIE6E7JDi2rosah4SpCOTrKufeszFyj5YEavbQuYlQ5cNFvtm8KuE2
xXMRgRI4RGvM2leVqcoDw5hS3m2pOJLxH8l2WE72YjYvWhvnwc5Rofe/8y
B/vaSK9WCnqN8y2q6Vmy73AGP0fuiwmuBra7LlkOiqmyx3amSFizwms= )
urn.uri.arpa. 604800 IN NAPTR 0 0 "" "" (
"/urn:([^:]+)/\\1/i" . )
urn.uri.arpa. 604800 IN RRSIG NAPTR 8 3 604800 (
20210217232440 20210120232440 37444 uri.arpa.
CVt2Tgz0e5ZmaSXqRfNys/8OtVCk9nfP0zhezhN8Bo6MDt6yyKZ2kEEWJP
jkN7PCYHjO8fGjnUn0AHZI2qBNv7PKHcpR42VY03q927q85a65weOO1YE0
vPYMzACpua9TOtfNnynM2Ws0uN9URxUyvYkXBdqOC81N3sx1dVELcwc= )
urn.uri.arpa. 3600 IN NSEC uri.arpa. NAPTR RRSIG NSEC
urn.uri.arpa. 3600 IN RRSIG NSEC 8 3 3600 (
20210217232440 20210120232440 37444 uri.arpa.
JuKkMiC3/j9iM3V8/izcouXWAVGnSZjkOgEgFPhutMqoylQNRcSkbEZQzF
K8B/PIVdzZF0Y5xkO6zaKQjOzz6OkSaNPIo1a7Vyyl3wDY/uLCRRAHRJfp
knuY7O+AUNXvVVIEYJqZggd4kl/Rjh1GTzPYZTRrVi5eQidI1LqCOeg= )A.5. The ROOT-SERVERS.NET Zone
Next up is the ROOT-SERVERS.NET zone, retrieved 2018-10-21 💖
root-servers.net. 3600000 IN SOA a.root-servers.net. (
nstld.verisign-grs.com. 2018091100 14400 7200 1209600 3600000 )
root-servers.net. 3600000 IN NS a.root-servers.net.
root-servers.net. 3600000 IN NS b.root-servers.net.
root-servers.net. 3600000 IN NS c.root-servers.net.
root-servers.net. 3600000 IN NS d.root-servers.net.
root-servers.net. 3600000 IN NS e.root-servers.net.
root-servers.net. 3600000 IN NS f.root-servers.net.
root-servers.net. 3600000 IN NS g.root-servers.net.
root-servers.net. 3600000 IN NS h.root-servers.net.
root-servers.net. 3600000 IN NS i.root-servers.net.
root-servers.net. 3600000 IN NS j.root-servers.net.
root-servers.net. 3600000 IN NS k.root-servers.net.
root-servers.net. 3600000 IN NS l.root-servers.net.
root-servers.net. 3600000 IN NS m.root-servers.net.
a.root-servers.net. 3600000 IN AAAA 2001:503:ba3e::2:30
a.root-servers.net. 3600000 IN A 198.41.0.4
b.root-servers.net. 3600000 IN MX 20 mail.isi.edu.
b.root-servers.net. 3600000 IN AAAA 2001:500:200::b
b.root-servers.net. 3600000 IN A 199.9.14.201
c.root-servers.net. 3600000 IN AAAA 2001:500:2::c
c.root-servers.net. 3600000 IN A 192.33.4.12
d.root-servers.net. 3600000 IN AAAA 2001:500:2d::d
d.root-servers.net. 3600000 IN A 199.7.91.13
e.root-servers.net. 3600000 IN AAAA 2001:500:a8::e
e.root-servers.net. 3600000 IN A 192.203.230.10
f.root-servers.net. 3600000 IN AAAA 2001:500:2f::f
f.root-servers.net. 3600000 IN A 192.5.5.241
g.root-servers.net. 3600000 IN AAAA 2001:500:12::d0d
g.root-servers.net. 3600000 IN A 192.112.36.4
h.root-servers.net. 3600000 IN AAAA 2001:500:1::53
h.root-servers.net. 3600000 IN A 198.97.190.53
i.root-servers.net. 3600000 IN MX 10 mx.i.root-servers.org.
i.root-servers.net. 3600000 IN AAAA 2001:7fe::53
i.root-servers.net. 3600000 IN A 192.36.148.17
j.root-servers.net. 3600000 IN AAAA 2001:503:c27::2:30
j.root-servers.net. 3600000 IN A 192.58.128.30
k.root-servers.net. 3600000 IN AAAA 2001:7fd::1
k.root-servers.net. 3600000 IN A 193.0.14.129
l.root-servers.net. 3600000 IN AAAA 2001:500:9f::42
l.root-servers.net. 3600000 IN A 199.7.83.42
m.root-servers.net. 3600000 IN AAAA 2001:dc3::35
m.root-servers.net. 3600000 IN A 202.12.27.33
root-servers.net. 3600000 IN SOA a.root-servers.net. (
nstld.verisign-grs.com. 2018091100 14400 7200 1209600 3600000 )
root-servers.net. 3600000 IN ZONEMD 2018091100 1 1 (
f1ca0ccd91bd5573d9f431c00ee0101b2545c97602be0a97
8a3b11dbfc1c776d5b3e86ae3d973d6b5349ba7f04340f79 )Appendix B. Implementation Status ✨
Appendix B is where we spill the tea on implementation status 🍵 This section records the status of known implementations of the protocol this spec defines, as of the time of publication, and it's inspired by the concepts described in RFC 7942.
Bestie, listing any individual implementation here does not imply endorsement by the IETF 🙅♀️ And no effort has been spent verifying the info that IETF contributors supplied either. This is not intended as, and must not be construed to be, a catalog of available implementations or their features. Readers are advised to note that other implementations may exist too 🦋
B.1. Authors' Implementation
okay so the authors built their own open-source implementation in C 💖 It uses the ldns library ([LDNS-ZONE-DIGEST]), and it can do these things:
- Read an input zone and output a zone with the ZONEMD placeholder.
- Compute the zone digest over the signed zone and update the ZONEMD record.
- Recompute DNSSEC signatures over the ZONEMD record.
- Verify the zone digest from an input zone.
But it does NOT: 🙈
- Perform DNSSEC validation of the ZONEMD record during verification.
B.2. Shane Kerr's Implementation
Shane Kerr wrote his own version of this spec during the IETF 102 hackathon ([ZONE-DIGEST-HACKATHON]) 🧚 It's written in Python, and it can:
- Read an input zone and output a zone with ZONEMD record.
- Verify the zone digest from an input zone.
- Output the ZONEMD record in its defined presentation format.
It does NOT:
- Recompute DNSSEC signatures over the ZONEMD record.
- Perform DNSSEC validation of the ZONEMD record.
B.3. NIC Chile Lab's Implementation
The NIC Chile Labs team built theirs as part of the "dns-tools" suite ([DNS-TOOLS]) ✨ On top of digesting, it can also sign and verify zones, which is so iconic. It's written in Go, and it can:
- Compute zone digest over signed zone and update the ZONEMD record.
- Verify the zone digest from an input zone.
- Perform DNSSEC validation of the ZONEMD record during verification.
- Recompute DNSSEC signatures over the ZONEMD record.
Acknowledgments 🫶
The authors wanted to thank David Blacka, Scott Hollenbeck, and Rick Wilhelm for giving feedback on early drafts of this document 💜 They also thank Joe Abley, Mark Andrews, Ralph Dolmans, Donald Eastlake 3rd, Richard Gibson, Olafur Gudmundsson, Bob Harold, Paul Hoffman, Evan Hunt, Shumon Huque, Tatuya Jinmei, Mike St. Johns, Burt Kaliski, Shane Kerr, Matt Larson, Barry Leiba, John Levine, Ed Lewis, Matt Pounsett, Mukund Sivaraman, Petr Spacek, Ondrej Sury, Willem Toorop, Florian Weimer, Tim Wicinski, Wouter Wijngaards, Paul Wouters, and the other members of the DNSOP Working Group for their input 🌸
The authors would like to thank Tim Wicinski again, who served as the Document Shepherd for this document 👑
Authors' Addresses 🎀
Here are the authors, with their contact details, exactly as they're listed.
Duane Wessels
Verisign
12061 Bluemont Way
Reston, VA 20190
United States of America
Phone: +1 703 948-3200
Email: dwessels@verisign.com
URI: https://verisign.comPiet Barber
Verisign
12061 Bluemont Way
Reston, VA 20190
United States of America
Phone: +1 703 948-3200
Email: pbarber@verisign.com
URI: https://verisign.comMatt Weinberg
Amazon
Email: matweinb@amazon.com
URI: https://amazon.comWarren Kumari
Google
1600 Amphitheatre Parkway
Mountain View, CA 94043
United States of America
Email: warren@kumari.netWes Hardaker
USC/ISI
P.O. Box 382
Davis, CA 95617
United States of America
Email: ietf@hardakers.net📦 where this page comes from
- ietf: rfc8976 2021-02
- 💖 girlified by claude-haiku-5-5 on : a language model's rewrite of the original, under its terms