<?xml version="1.0"encoding="US-ASCII"?>encoding="UTF-8"?> <!DOCTYPE rfc SYSTEM"rfc2629.dtd" [ <!ENTITY rfc2119 PUBLIC "" ".//reference.RFC.2119.xml"> ]> <!-- WK: Set category, IPR, docName -->"rfc2629-xhtml.ent"> <rfccategory="std"xmlns:xi="http://www.w3.org/2001/XInclude" docName="draft-ietf-dnsop-extended-error-16"ipr="trust200902"> <?xml-stylesheet type='text/xsl' href='rfc2629.xslt' ?> <?rfc toc="yes" ?> <?rfc symrefs="yes" ?> <?rfc sortrefs="yes"?> <?rfc iprnotified="no" ?> <?rfc strict="yes"?> <?rfc compact="yes" ?> <?rfc subcompact="yes" ?> <front>number="8914" ipr="trust200902" obsoletes="" updates="" submissionType="IETF" category="std" consensus="true" xml:lang="en" tocInclude="true" symRefs="true" sortRefs="true" version="3"> <!--WK: Set long title.xml2rfc v2v3 conversion 2.44.0 --> <front> <titleabbrev="draft-ietf-dnsop-extended-error">Extendedabbrev="Extended DNS Errors">Extended DNS Errors</title> <seriesInfo name="RFC" value="8914"/> <author fullname="Warren Kumari" initials="W." surname="Kumari"> <organization>Google</organization> <address> <postal> <street>1600 Amphitheatre Parkway</street> <city>MountainView, CA</city>View</city><region>CA</region> <code>94043</code><country>US</country><country>United States of America</country> </postal> <email>warren@kumari.net</email> </address> </author> <author fullname="Evan Hunt" initials="E." surname="Hunt"> <organization>ISC</organization> <address> <postal> <street>950 Charter St</street> <city>RedwoodCity, CA</city>City</city><region>CA</region> <code>94063</code><country>US</country><country>United States of America</country> </postal> <email>each@isc.org</email> </address> </author> <author fullname="Roy Arends" initials="R." surname="Arends"> <organization>ICANN</organization> <address> <postal> <street/> </postal> <email>roy.arends@icann.org</email> </address> </author> <author fullname="Wes Hardaker" initials="W." surname="Hardaker"> <organization>USC/ISI</organization> <address> <postal> <street>P.O. Box 382</street><city>Davis, CA</city><city>Davis</city><region>CA</region> <code>95617</code><country>US</country><country>United States of America</country> </postal> <email>ietf@hardakers.net</email> </address> </author> <author fullname="David C Lawrence" initials="D." surname="Lawrence"><organization>Oracle + Dyn</organization><organization>Salesforce</organization> <address> <postal><street>150 Dow<street>415 Mission St</street><city>Manchester, NH</city> <code>03101</code> <country>US</country><city>San Francisco</city><region>CA</region> <code>94105</code> <country>United States of America</country> </postal> <email>tale@dd.org</email> </address> </author> <dateday="05" month="May"month="October" year="2020"/> <keyword>DNS</keyword> <keyword>Error</keyword> <keyword>Domain</keyword> <keyword>Name</keyword> <keyword>System</keyword> <abstract> <t>This document defines an extensible method to return additional information about the cause of DNS errors. Though created primarily to extend SERVFAIL to provide additional information about the cause of DNS and DNSSEC failures, the Extended DNS Errors option defined in this document allows all response types to contain extended error information. Extended DNS Error information does not change the processing of RCODEs.</t> </abstract> </front> <middle> <sectiontitle="Introductionanchor="intro" numbered="true" toc="default"> <name>Introduction andbackground" anchor="intro">Background</name> <t>There are many reasons that a DNS query mayfail,fail -- some of them transient, some permanent; some can be resolved by querying another server, some are likely best handled by stopping resolution. Unfortunately, the error signals that a DNS server can return are verylimited,limited and are not very expressive. This means that applications and resolvers often have to "guess" at what the issueis - e.g.is, e.g., was the answer marked REFUSED because of a lamedelegation,delegation or because the nameserver is still starting up and loading zones? Is a SERVFAIL a DNSSEC validation issue, or is the nameserver experiencing some other failure? What error messages should be presented to the user or logged under these conditions?</t> <t>A good example of issues that would benefit from additional error information are errors caused by DNSSEC validation issues. When a stub resolver queries a namewhichthat is DNSSEC bogus <xref target="RFC8499"/>format="default"/> (using a validating resolver), the stub resolver receives only a SERVFAIL in response. Unfortunately, the SERVFAIL Response Code (RCODE) is used to signal many sorts of DNS errors, and so the stub resolver's only option is to ask the next configured DNS resolver. The result of trying the next resolver is one of two outcomes: either the next resolver alsovalidates,validates and a SERVFAIL is returnedagain,again or the next resolver is not a validatingresolver,resolver and the user is returned a potentially harmful result. With an Extended DNS Error (EDE) option enclosed in the response message, the resolver is able to return a more descriptive reason as to why any failureshappened,happened or add additional context to a message containing a NOERROR RCODE.</t> <t>This document specifies a mechanism to extend DNS errors to provide additional information about the cause of an error.These extendedThe Extended DNSerrorError codesaredescribed in this document can be used by any system that sends DNS queries and receives a response containing an EDE option. Different codes are useful in different circumstances, and thus different systems (stub resolvers, recursive resolvers, and authoritative resolvers) might receive and use them.</t> <sectiontitle="Requirements notation"> <t>Thenumbered="true" toc="default"> <name>Requirements Notation</name> <t> The key words"MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY","<bcp14>MUST</bcp14>", "<bcp14>MUST NOT</bcp14>", "<bcp14>REQUIRED</bcp14>", "<bcp14>SHALL</bcp14>", "<bcp14>SHALL NOT</bcp14>", "<bcp14>SHOULD</bcp14>", "<bcp14>SHOULD NOT</bcp14>", "<bcp14>RECOMMENDED</bcp14>", "<bcp14>NOT RECOMMENDED</bcp14>", "<bcp14>MAY</bcp14>", and"OPTIONAL""<bcp14>OPTIONAL</bcp14>" in this document are to be interpreted as described inBCP 14BCP 14 <xref target="RFC2119"/> <xref target="RFC8174"/> when, and only when, they appear in all capitals, as shownhere.</t>here. </t> </section> </section> <sectiontitle="Extendednumbered="true" toc="default"> <name>Extended DNS Error EDNS0option format">Option Format</name> <t>Thisdraftdocument uses anEDNS0 (<xrefExtended Mechanism for DNS (EDNS0) <xref target="RFC6891"/>)format="default"/> option to include Extended DNS Error (EDE) information in DNS messages. The option is structured as follows:</t><figure><artworkalign="left"><![CDATA[align="left" name="" type="" alt=""><![CDATA[ 1 1 1 1 1 1 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 +---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+ 0: | OPTION-CODE | +---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+ 2: | OPTION-LENGTH | +---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+ 4: | INFO-CODE | +---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+ 6: / EXTRA-TEXT ... / +---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+ ]]></artwork></figure><t/> <t>Field definition details:</t><t><list style="symbols"> <t>OPTION-CODE, 2-octets/16-bits<dl newline="true"> <dt>OPTION-CODE: </dt> <dd>2 octets / 16 bits (defined in <xref target="RFC6891"/>]), for EDE is TBD. [RFC Editor: change TBD toformat="default"/>) contains theproper code once assigned by IANA.]</t> <t>OPTION-LENGTH, 2-octets/16-bits ((definedvalue 15 for EDE.</dd> <dt>OPTION-LENGTH: </dt> <dd>2 octets / 16 bits (defined in <xref target="RFC6891"/>])format="default"/>) contains the length of the payload (everything after OPTION-LENGTH) in octets and should be 2 plus the length of the EXTRA-TEXT field (which may be a zero-lengthstring).</t> <t>INFO-CODE, 16-bits,string).</dd> <dt>INFO-CODE:</dt> <dd>16 bits, which is the principal contribution of this document. This 16-bit value, encoded in network most significant bit (MSB) byte order, provides the additional context for the RESPONSE-CODE of the DNS message. The INFO-CODE serves as an index into the "Extended DNS Errors"registryregistry, defined and created in <xref target="IANA"/>.</t> <t>EXTRA-TEXT, a variable length, UTF-8 encodedformat="default"/>.</dd> <dt>EXTRA-TEXT: </dt> <dd>a variable-length, UTF-8-encoded <xref target="RFC5198"/>,format="default"/> text field that may hold additional textual information. This information is intended for human consumption (not automated parsing). EDE text may be null terminated butMUST NOT<bcp14>MUST NOT</bcp14> be assumed to be; the lengthMUST<bcp14>MUST</bcp14> be derived from the OPTION-LENGTH field. The EXTRA-TEXT field may be zero octets in length, indicating that there is no EXTRA-TEXT included. Care should be taken not to include private information in the EXTRA-TEXT field that an observer would not otherwise have access to, such as accountnumbers.</t> </list></t>numbers.</dd> </dl> <t>The Extended DNS Error (EDE) option can be included in any response (SERVFAIL, NXDOMAIN, REFUSED,andeven NOERROR,etc)etc.) to a query that includes an OPTPseudo-RRpseudo-RR <xref target="RFC6891"/>.format="default"/>. This document includes a set of initialcodepoints,codepoints but is extensible via the IANA registry defined and created in <xref target="IANA"/>.</t>format="default"/>.</t> </section> <sectiontitle="Extendednumbered="true" toc="default"> <name>Extended DNS ErrorProcessing">Processing</name> <t>When the response grows beyond the requestor's UDP payload size <xref target="RFC6891"/>,format="default"/>, serversSHOULD<bcp14>SHOULD</bcp14> truncate messages by dropping EDE options before dropping other data from packets. ImplementationsSHOULD<bcp14>SHOULD</bcp14> set the truncation bit when dropping EDE options. Because long EXTRA-TEXT fields may trigger truncation (which is undesirable given the supplemental nature ofEDE)EDE), implementers and operators creating EDE optionsSHOULD<bcp14>SHOULD</bcp14> avoid lengthy EXTRA-TEXT contents.</t> <t>When a resolver or forwarder receives an EDE option, whether or not (and how) to pass along EDE information on to their original client is implementation dependent. ImplementationsMAY<bcp14>MAY</bcp14> choose to not forward information, or theyMAY<bcp14>MAY</bcp14> choose to create a new EDE option(s) that conveys the information encoded in the received EDE. When doing so, the source of the errorSHOULD<bcp14>SHOULD</bcp14> be attributed in the EXTRA-TEXT field, since an EDNS0 option received by the original client will appear to have come from the resolver or forwarder sending it.</t> <t>This document does not allow or prohibit any particular extended error codes and information to be matched with any particular RCODEs. Some combinations of extended error codes and RCODEs may seem nonsensical (such as resolver-specific extended error codes received in responses from authoritative servers), so systems interpreting the extended error codesMUST NOT<bcp14>MUST NOT</bcp14> assume that a combination will make sense. ReceiversMUST<bcp14>MUST</bcp14> be able to accept EDE codes and EXTRA-TEXT in all messages, including those with a NOERRORRCODE,RCODE but need not act on them. ApplicationsMUST<bcp14>MUST</bcp14> continue to follow requirements from applicable specifications on how to process RCODEs no matter what EDE values are also received. SendersMAY<bcp14>MAY</bcp14> include more than one EDE option and receiversMUST<bcp14>MUST</bcp14> be able to accept (but not necessarily process or act on) multiple EDE options in a DNS message.</t> </section> <sectiontitle="Definednumbered="true" toc="default"> <name>Defined Extended DNSErrors">Errors</name> <t>This document defines some initial EDE codes. The mechanism is intended to be extensible, and additionalcode-pointscodepoints can be registered in the "Extended DNS Errors" registry<xref(<xref target="IANA"/>.format="default"/>). The INFO-CODE from the EDE EDNS option is used to serve as an index into the "Extended DNS Error" IANA registry, the initial values for which are defined in the followingsub-sections.</t>subsections.</t> <section anchor="errother"title="Extendednumbered="true" toc="default"> <name>Extended DNS Error Code 0 -Other">Other</name> <t>The error in question falls into a category that does not match known extended error codes. ImplementationsSHOULD<bcp14>SHOULD</bcp14> include an EXTRA-TEXT value to augment this error code with additional information.</t> </section> <section anchor="errbaddnskeyalg"title="Extendednumbered="true" toc="default"> <name>Extended DNS Error Code 1 - Unsupported DNSKEYAlgorithm">Algorithm</name> <t>The resolver attempted to perform DNSSEC validation, but a DNSKEYRRSETRRset contained only unsupported DNSSEC algorithms.</t> </section> <section anchor="errbaddsdigest"title="Extendednumbered="true" toc="default"> <name>Extended DNS Error Code 2 - Unsupported DS DigestType">Type</name> <t>The resolver attempted to perform DNSSEC validation, but a DSRRSETRRset contained only unsupported Digest Types.</t> </section> <section anchor="stalenoerror"title="Extendednumbered="true" toc="default"> <name>Extended DNS Error Code 3 - StaleAnswer">Answer</name> <t>The resolver was unable to resolve the answer within its time limits and decided to answer with previously cached data instead of answering with an error. This is typically caused by problems communicating with an authoritative server, possibly as result of a denial of service (DoS) attack against another network. (See also Code 19.)</t> </section> <section anchor="forgedanswer"title="Extendednumbered="true" toc="default"> <name>Extended DNS Error Code 4 - ForgedAnswer">Answer</name> <t>For policy reasons (legalobligation,obligation or malware filtering, for instance), an answer was forged. Note that this should be used when an answer is still provided, not when failure codes are returned instead. SeeBlocked(15),Blocked (15), Censored (16), and Filtered (17) for use when returning other response codes.</t> </section> <section anchor="errindeterminate"title="Extendednumbered="true" toc="default"> <name>Extended DNS Error Code 5 - DNSSECIndeterminate">Indeterminate</name> <t>The resolver attempted to perform DNSSEC validation, but validation ended in the Indeterminate state <xref target="RFC4035"/>.</t>format="default"/>.</t> </section> <section anchor="errbogus"title="Extendednumbered="true" toc="default"> <name>Extended DNS Error Code 6 - DNSSECBogus">Bogus</name> <t>The resolver attempted to perform DNSSEC validation, but validation ended in the Bogus state.</t> </section> <section anchor="errexpired"title="Extendednumbered="true" toc="default"> <name>Extended DNS Error Code 7 - SignatureExpired">Expired</name> <t>The resolver attempted to perform DNSSEC validation, but no signatures are presently valid and some (often all) are expired.</t> </section> <section anchor="errprior"title="Extendednumbered="true" toc="default"> <name>Extended DNS Error Code 8 - Signature Not YetValid">Valid</name> <t>The resolver attempted to perform DNSSEC validation, butbutno signatures are presently valid and at least some are not yet valid.</t> </section> <section anchor="errnodnskey"title="Extendednumbered="true" toc="default"> <name>Extended DNS Error Code 9 - DNSKEYMissing">Missing</name> <t>A DS record existed at a parent, but no supported matching DNSKEY record could be found for the child.</t> </section> <section anchor="errnorrsig"title="Extendednumbered="true" toc="default"> <name>Extended DNS Error Code 10 - RRSIGsMissing">Missing</name> <t>The resolver attempted to perform DNSSEC validation, but no RRSIGs could be found for at least one RRset where RRSIGs were expected.</t> </section> <section anchor="errnozonekey"title="Extendednumbered="true" toc="default"> <name>Extended DNS Error Code 11 - No Zone Key BitSet">Set</name> <t>The resolver attempted to perform DNSSEC validation, but no Zone Key Bit was set in a DNSKEY.</t> </section> <section anchor="nonsec"title="Extendednumbered="true" toc="default"> <name>Extended DNS Error Code 12 - NSECMissing">Missing</name> <t>The resolver attempted to perform DNSSEC validation, but the requested data was missing and a covering NSEC or NSEC3 was not provided.</t> </section> <section anchor="cachederror"title="Extendednumbered="true" toc="default"> <name>Extended DNS Error Code 13 - CachedError">Error</name> <t>The resolver is returning the SERVFAIL RCODE from its cache.</t> </section> <section anchor="notready"title="Extendednumbered="true" toc="default"> <name>Extended DNS Error Code 14 - NotReady">Ready</name> <t>The server is unable to answer thequeryquery, as it was not fully functional when the query was received.</t> </section> <section anchor="errblocked"title="Extendednumbered="true" toc="default"> <name>Extended DNS Error Code 15 -Blocked">Blocked</name> <t>The server is unable to respond to the request because the domain isblacklistedon a blocklist due to an internal security policy imposed by the operator of the server resolving or forwarding the query.</t> </section> <section anchor="errcensored"title="Extendednumbered="true" toc="default"> <name>Extended DNS Error Code 16 -Censored">Censored</name> <t>The server is unable to respond to the request because the domain isblacklistedon a blocklist due to an external requirement imposed by an entity other than the operator of the server resolving or forwarding the query. Note that how the imposed policy is applied is irrelevant (in-band DNS filtering, court order,etc).</t>etc.).</t> </section> <section anchor="errfiltered"title="Extendednumbered="true" toc="default"> <name>Extended DNS Error Code 17 -Filtered">Filtered</name> <t>The server is unable to respond to the request because the domain isblacklistedon a blocklist as requested by the client. Functionally, this amounts to "you requested that we filter domains like this one."</t> </section> <section anchor="errprohibted"title="Extendednumbered="true" toc="default"> <name>Extended DNS Error Code 18 -Prohibited">Prohibited</name> <t>An authoritative server or recursive resolver that receives a query from an "unauthorized" client can annotate its REFUSED message with this code. Examples of "unauthorized" clients are recursive queries from IP addresses outside the network,blacklistedblocklisted IP addresses, local policy, etc.</t> </section> <section anchor="stalenx"title="Extendednumbered="true" toc="default"> <name>Extended DNS Error Code 19 - Stale NXDOMAINAnswer">Answer</name> <t>The resolver was unable to resolve an answer within its configured time limits and decided to answer with a previously cached NXDOMAIN answer instead of answering with an error. This may be caused, for example, by problems communicating with an authoritative server, possibly as result of a denial of service (DoS) attack against another network. (See also Code 3.) </t> </section> <section anchor="errlame"title="Extendednumbered="true" toc="default"> <name>Extended DNS Error Code 20 - NotAuthoritative">Authoritative</name> <t>An authoritative server that receives a query with theRDRecursion Desired (RD) bit clear, or when it is not configured for recursion for a domain for which it is notauthoritative SHOULDauthoritative, <bcp14>SHOULD</bcp14> include this EDE code in the REFUSED response. A resolver that receives a query with the RD bit clearSHOULD<bcp14>SHOULD</bcp14> include this EDE code in the REFUSED response.</t> </section> <section anchor="deprecated"title="Extendednumbered="true" toc="default"> <name>Extended DNS Error Code 21 - NotSupported">Supported</name> <t>The requested operation or query is not supported.</t> </section> <section anchor="noreachable"title="Extendednumbered="true" toc="default"> <name>Extended DNS Error Code 22 - No ReachableAuthority">Authority</name> <t>The resolver could not reach any of the authoritative name servers (or they potentially refused to reply).</t> </section> <section anchor="networkerror"title="Extendednumbered="true" toc="default"> <name>Extended DNS Error Code 23 - NetworkError">Error</name> <t>An unrecoverable error occurred while communicating with another server.</t> </section> <section anchor="invaliddata"title="Extendednumbered="true" toc="default"> <name>Extended DNS Error Code 24 - InvalidData">Data</name> <t>The authoritative server cannot answer with data for a zone it is otherwise configured to support. Examples of this include its most recent zone being tooold,old or having expired.</t> </section> </section> <sectiontitle="IANA Considerations"> <section title="Anumbered="true" toc="default"> <name>IANA Considerations</name> <section numbered="true" toc="default"> <name>A New Extended DNS Error Code EDNSOption">Option</name> <t>This document defines a new EDNS(0) option, entitled "Extended DNS Error", with the assignedavalue ofTBD15 from the "DNS EDNS0 Option Codes (OPT)"registry [to be removed upon publication: [http://www.iana.org/assignments/dns-parameters/dns-parameters.xhtml#dns-parameters-11]</t> <t><figure> <artwork><![CDATA[Valueregistry: </t> <table anchor="ext-DNS"> <thead> <tr> <th> Value </th> <th> Name </th> <th> Status </th> <th> Reference----- ---------------- ------ ------------------ TBD Extended DNS Error Standard [ This document ]]]></artwork> </figure></t> </section> <section title="New</th> </tr> </thead> <tbody> <tr> <td>15</td> <td>Extended DNS Error</td> <td>Standard</td> <td>RFC 8914</td> </tr> </tbody> </table> </section> <section anchor="IANA" numbered="true" toc="default"> <name>New Registry for Extended DNS ErrorCodes" anchor="IANA">Codes</name> <t>IANAis requested to createhas created and will maintain a new registrytablecalled "Extended DNS Error Codes" on the "Domain Name System (DNS) Parameters" web page as follows:</t><t>Registry Name: Extended DNS Error Codes</t> <t>Registration Procedures:</t> <t><list style="symbols"> <t>0<table anchor="reg_proc"> <thead> <tr> <th>Range</th> <th>Registration Procedures</th> </tr> </thead> <tbody> <tr> <td>0 -49151:49151</td><td>First Come Firstcome, first served.</t> <t>49152 - 65535: Private use.</t> </list></t> <t>Reference: [this document]</t>Served</td> </tr> <tr> <td>49152 - 65535</td><td>Private Use</td> </tr> </tbody> </table> <t>TheExtended"Extended DNS ErrorCodesCodes" registry is a table with three columns: INFO-CODE, Purpose, and Reference. The initialcontentscontent is asbelow with [this document] added to each reference given.</t> <t><list style="hanging" hangIndent="10"> <t hangText="INFO-CODE:">0</t> <t hangText="Purpose:">Other Error</t> <t hangText="Reference:"><xrefbelow.</t> <table> <thead> <tr> <th>INFO-CODE </th> <th>Purpose </th> <th>Reference </th> </tr> </thead> <tbody> <tr> <td> 0 </td> <td> Other Error</td> <td> <xref target="errother"/></t> </list></t> <t><list style="hanging" hangIndent="10"> <t hangText="INFO-CODE:">1</t> <t hangText="Purpose:">Unsupportedformat="default"/> </td> </tr> <tr> <td> 1 </td> <td align="center"> Unsupported DNSKEYAlgorithm</t> <t hangText="Reference:"><xrefAlgorithm </td> <td> <xref target="errbaddnskeyalg"/></t> </list></t> <t><list style="hanging" hangIndent="10"> <t hangText="INFO-CODE:">2</t> <t hangText="Purpose:">Unsupportedformat="default"/> </td> </tr> <tr> <td> 2 </td> <td>Unsupported DS DigestType</t> <t hangText="Reference:"><xrefType </td> <td> <xref target="errbaddsdigest"/></t> </list></t> <t><list style="hanging" hangIndent="10"> <t hangText="INFO-CODE:">3</t> <t hangText="Purpose:">Stale Answer</t> <t hangText="Reference:"><xrefformat="default"/> </td> </tr> <tr> <td> 3 </td> <td> Stale Answer </td> <td> <xref target="stalenoerror"/>,format="default"/> and <xref target="RFC8767"/></t> </list></t> <t><list style="hanging" hangIndent="10"> <t hangText="INFO-CODE:">4</t> <t hangText="Purpose:">Forged Answer</t> <t hangText="Reference:"><xrefformat="default"/> </td> </tr> <tr> <td> 4 </td> <td> Forged Answer </td> <td> <xref target="forgedanswer"/></t> </list></t> <t><list style="hanging" hangIndent="10"> <t hangText="INFO-CODE:">5</t> <t hangText="Purpose:">DNSSEC Indeterminate</t> <t hangText="Reference:"><xrefformat="default"/> </td> </tr> <tr> <td> 5 </td> <td> DNSSEC Indeterminate </td> <td> <xref target="errindeterminate"/></t> </list></t> <t><list style="hanging" hangIndent="10"> <t hangText="INFO-CODE:">6</t> <t hangText="Purpose:">DNSSEC Bogus</t> <t hangText="Reference:"><xrefformat="default"/> </td> </tr> <tr> <td> 6 </td> <td>DNSSEC Bogus </td> <td> <xref target="errbogus"/></t> </list></t> <t><list style="hanging" hangIndent="10"> <t hangText="INFO-CODE:">7</t> <t hangText="Purpose:">Signature Expired</t> <t hangText="Reference:"><xrefformat="default"/> </td> </tr> <tr> <td> 7 </td> <td> Signature Expired </td> <td> <xref target="errexpired"/></t> </list></t> <t><list style="hanging" hangIndent="10"> <t hangText="INFO-CODE:">8</t> <t hangText="Purpose:">Signatureformat="default"/> </td> </tr> <tr> <td>8 </td> <td>Signature Not YetValid</t> <t hangText="Reference:"><xrefValid </td> <td> <xref target="errprior"/></t> </list></t> <t><list style="hanging" hangIndent="10"> <t hangText="INFO-CODE:">9</t> <t hangText="Purpose:">DNSKEY Missing</t> <t hangText="Reference:">format="default"/> </td> </tr> <tr> <td>9 </td> <td>DNSKEY Missing </td> <td> <xref target="errnodnskey"/></t> </list></t> <t><list style="hanging" hangIndent="10"> <t hangText="INFO-CODE:">10</t> <t hangText="Purpose:">RRSIGs Missing</t> <t hangText="Reference:"><xrefformat="default"/> </td> </tr> <tr> <td>10 </td> <td>RRSIGs Missing </td> <td> <xref target="errnorrsig"/></t> </list></t> <t><list style="hanging" hangIndent="10"> <t hangText="INFO-CODE:">11</t> <t hangText="Purpose:">Noformat="default"/> </td> </tr> <tr> <td>11 </td> <td>No Zone Key BitSet</t> <t hangText="Reference:"><xrefSet </td> <td> <xref target="errnozonekey"/></t> </list></t> <t><list style="hanging" hangIndent="10"> <t hangText="INFO-CODE:">12</t> <t hangText="Purpose:">NSEC Missing</t> <t hangText="Reference:"><xrefformat="default"/> </td> </tr> <tr> <td>12 </td> <td>NSEC Missing </td> <td> <xref target="nonsec"/></t> </list></t> <t><list style="hanging" hangIndent="10"> <t hangText="INFO-CODE:">13</t> <t hangText="Purpose:">Cached Error</t> <t hangText="Reference:"><xrefformat="default"/> </td> </tr> <tr> <td>13 </td> <td>Cached Error </td> <td> <xref target="cachederror"/></t> </list></t> <t><list style="hanging" hangIndent="10"> <t hangText="INFO-CODE:">14</t> <t hangText="Purpose:">Not Ready.</t> <t hangText="Reference:"><xrefformat="default"/> </td> </tr> <tr> <td>14 </td> <td>Not Ready</td> <td> <xref target="notready"/></t> </list></t> <t><list style="hanging" hangIndent="10"> <t hangText="INFO-CODE:">15</t> <t hangText="Purpose:">Blocked</t> <t hangText="Reference:"><xrefformat="default"/> </td> </tr> <tr> <td>15 </td> <td>Blocked </td> <td> <xref target="errblocked"/></t> </list></t> <t><list style="hanging" hangIndent="10"> <t hangText="INFO-CODE:">16</t> <t hangText="Purpose:">Censored</t> <t hangText="Reference:"><xrefformat="default"/> </td> </tr> <tr> <td>16 </td> <td>Censored </td> <td> <xref target="errcensored"/></t> </list></t> <t><list style="hanging" hangIndent="10"> <t hangText="INFO-CODE:">17</t> <t hangText="Purpose:">Filtered</t> <t hangText="Reference:"><xrefformat="default"/> </td> </tr> <tr> <td>17 </td> <td>Filtered </td> <td> <xref target="errfiltered"/></t> </list></t> <t><list style="hanging" hangIndent="10"> <t hangText="INFO-CODE:">18</t> <t hangText="Purpose:">Prohibited</t> <t hangText="Reference:"><xrefformat="default"/> </td> </tr> <tr> <td>18 </td> <td>Prohibited </td> <td> <xref target="errprohibted"/></t> </list></t> <t><list style="hanging" hangIndent="10"> <t hangText="INFO-CODE:">19</t> <t hangText="Purpose:">Staleformat="default"/> </td> </tr> <tr> <td>19 </td> <td>Stale NXDomainAnswer</t> <t hangText="Reference:"><xrefAnswer </td> <td> <xref target="stalenx"/></t> </list></t> <t><list style="hanging" hangIndent="10"> <t hangText="INFO-CODE:">20</t> <t hangText="Purpose:">Not Authoritative</t> <t hangText="Reference:"><xrefformat="default"/> </td> </tr> <tr> <td>20 </td> <td>Not Authoritative </td> <td> <xref target="errlame"/></t> </list></t> <t><list style="hanging" hangIndent="10"> <t hangText="INFO-CODE:">21</t> <t hangText="Purpose:">Not Supported</t> <t hangText="Reference:"><xrefformat="default"/> </td> </tr> <tr> <td>21 </td> <td>Not Supported </td> <td><xref target="deprecated"/></t> </list></t> <t><list style="hanging" hangIndent="10"> <t hangText="INFO-CODE:">22</t> <t hangText="Purpose:">Noformat="default"/> </td> </tr> <tr> <td>22 </td> <td>No ReachableAuthority</t> <t hangText="Reference:"><xrefAuthority </td> <td> <xref target="noreachable"/></t> </list></t> <t><list style="hanging" hangIndent="10"> <t hangText="INFO-CODE:">23</t> <t hangText="Purpose:">Network Error</t> <t hangText="Reference:"><xrefformat="default"/> </td> </tr> <tr> <td>23 </td> <td>Network Error </td> <td> <xref target="networkerror"/></t> </list></t> <t><list style="hanging" hangIndent="10"> <t hangText="INFO-CODE:">24</t> <t hangText="Purpose:">Invalid Data</t> <t hangText="Reference:"><xrefformat="default"/> </td> </tr> <tr> <td>24 </td> <td>Invalid Data </td> <td> <xref target="invaliddata"/></t> </list></t> <t><list style="hanging" hangIndent="10"> <t hangText="INFO-CODE:">25-65535</t> <t hangText="Purpose:">Unassigned</t> <t hangText="Reference:"><xref target="IANA" /></t> </list></t>format="default"/> </td> </tr> <tr> <td>25-49151</td> <td>Unassigned</td> <td></td> </tr> <tr> <td>49152-65535</td> <td>Reserved for Private Use</td> <td><xref target="IANA"/></td> </tr> </tbody> </table> </section> </section> <section anchor="security"title="Security Considerations">numbered="true" toc="default"> <name>Security Considerations</name> <t>Though DNSSEC continues to be deployed, unfortunately a significant number of clients (~11% according to <xreftarget="GeoffValidation"/>)target="GeoffValidation" format="default"/>) that receive a SERVFAIL from a validating resolver because of a DNSSEC validation issue will simply ask the next (potentially non-validating) resolver in theirlist,list and thus don't get the protectionswhichthat DNSSEC should provide.</t> <t>EDE information is unauthenticated information, unless secured by a form of secured DNStransactiontransaction, such as <xreftarget="RFC2845"/>,target="RFC2845" format="default"/>, <xreftarget="RFC2931"/>,target="RFC2931" format="default"/>, <xreftarget="RFC8094"/>target="RFC8094" format="default"/>, or <xref target="RFC8484"/>.format="default"/>. An attacker(e.g(e.g., aMITMman in the middle (MITM) or malicious recursive server) could insert an extended error response into untrusted data— although ideally-- although, ideally, clients and resolvers would not trust any unauthenticated information. As such, EDE content should be treated only as diagnostic information andMUST NOT<bcp14>MUST NOT</bcp14> alter DNS protocol processing. Until all DNS answers are authenticated via DNSSEC or the other mechanisms mentioned above, there are sometradeoffs.trade-offs. As an example, an attacker who is able to insert the DNSSEC Bogus Extended Error into a DNS message could instead simply reply with a fictitious address (A or AAAA) record. Note that DNSResponse Codes (RCODEs)RCODEs also contain no authentication and can be just as easily manipulated. </t> <t>By design, EDE potentially exposes additional information via DNS resolution processes that may leak information. An example of this is the Prohibited EDE code (18), which may leak the fact that the name is on ablacklist.</t>blocklist.</t> </section> </middle> <back> <references> <name>References</name> <references> <name>Normative References</name> <xi:include href="https://xml2rfc.tools.ietf.org/public/rfc/bibxml/reference.RFC.2119.xml"/> <xi:include href="https://xml2rfc.tools.ietf.org/public/rfc/bibxml/reference.RFC.4035.xml"/> <xi:include href="https://xml2rfc.tools.ietf.org/public/rfc/bibxml/reference.RFC.5198.xml"/> <xi:include href="https://xml2rfc.tools.ietf.org/public/rfc/bibxml/reference.RFC.6891.xml"/> <xi:include href="https://xml2rfc.tools.ietf.org/public/rfc/bibxml/reference.RFC.8174.xml"/> <xi:include href="https://xml2rfc.tools.ietf.org/public/rfc/bibxml/reference.RFC.8499.xml"/> <xi:include href="https://xml2rfc.tools.ietf.org/public/rfc/bibxml/reference.RFC.8767.xml"/> </references> <references> <name>Informative References</name> <xi:include href="https://xml2rfc.tools.ietf.org/public/rfc/bibxml/reference.RFC.2845.xml"/> <xi:include href="https://xml2rfc.tools.ietf.org/public/rfc/bibxml/reference.RFC.2931.xml"/> <xi:include href="https://xml2rfc.tools.ietf.org/public/rfc/bibxml/reference.RFC.8094.xml"/> <xi:include href="https://xml2rfc.tools.ietf.org/public/rfc/bibxml/reference.RFC.8484.xml"/> <reference anchor="GeoffValidation" target="http://www.potaroo.net/presentations/2016-06-27-dnssec.pdf"> <front> <title abbrev="Validation today">A quick review of DNSSEC Validation in today's Internet</title> <author initials="G" surname="Huston" fullname="Geoff Huston"> <organization>APNIC</organization> </author> <date month="June" year="2016"/> </front> </reference> </references> </references> <sectiontitle="Acknowledgements">numbered="false" toc="default"> <name>Acknowledgements</name> <t>The authors wish to thank <contact fullname=" JoeAbley, Mark Andrews, Tim April, Vittorio Bertola, Stephane Bortzmeyer, Vladimir Cunat, Ralph Dolmans, Peter DeVries, PeterAbley"/>, <contact fullname="Mark Andrews"/>, <contact fullname="Tim April"/>, <contact fullname="Vittorio Bertola"/>, <contact fullname="Stephane Bortzmeyer"/>, <contact fullname="Vladimir Cunat"/>, <contact fullname="Ralph Dolmans"/>, <contact fullname="Peter DeVries"/>, <contact fullname="Peter vanDijk, Mats Dufberg,Dijk"/>, <contact fullname="Mats Dufberg"/>, <contact fullname=" DonaldEastlake, Bob Harold, Paul Hoffman, Geoff Huston,Eastlake"/>, <contact fullname="Bob Harold"/>, <contact fullname="Paul Hoffman"/>, <contact fullname="Geoff Huston"/>, <contact fullname=" ShaneKerr, Edward Lewis, CarlosKerr"/>, <contact fullname="Edward Lewis"/>, <contact fullname="Carlos M.Martinez, George Michelson, Eric Orth, Michael Sheldon, Puneet Sood, Petr Spacek,Martinez"/>, <contact fullname="George Michelson"/>, <contact fullname="Eric Orth"/>, <contact fullname="Michael Sheldon"/>, <contact fullname="Puneet Sood"/>, <contact fullname="Petr Spacek"/>, <contact fullname=" OndrejSury, John Todd, Loganaden Velvindron, and Paul Vixie.Sury"/>, <contact fullname="John Todd"/>, <contact fullname="Loganaden Velvindron"/>, and <contact fullname="Paul Vixie"/>. They also vaguely remember discussing this with a number of people over theyears,years but have forgotten who allthey were -- if you were oneofthem, and are not listed, please let us know and we'llthem were. Apologies if we forgot to acknowledgeyou.</t>your contributions.</t> <t>One author also wants to thank the band"Infected Mushroom"Infected Mushroom for providing a good background soundtrack (and to see if he can get away with this in an RFC!). Another author would like to thank the band"Mushroom Infectors".Mushroom Infectors. This was funny at the time we wrote it, but we cannot remember why...</t> </section></middle> <back> <references title="Normative References"> <?rfc include='reference.RFC.2119' ?> <?rfc include='reference.RFC.4035' ?> <?rfc include='reference.RFC.5198' ?> <?rfc include='reference.RFC.6891' ?> <?rfc include='reference.RFC.8174' ?> <?rfc include='reference.RFC.8499' ?> <?rfc include='reference.RFC.8767' ?> </references> <references title="Informative References"> <?rfc include='reference.RFC.2845' ?> <?rfc include='reference.RFC.2931' ?> <?rfc include='reference.RFC.8094' ?> <?rfc include='reference.RFC.8484' ?> <reference anchor="GeoffValidation" target="http://www.potaroo.net/presentations/2016-06-27-dnssec.pdf"> <front> <title abbrev="Validation today">A quick review of DNSSEC Validation in today’s Internet</title> <author fullname="Geoff Huston, APNIC"> <organization>IANA</organization> </author> <date month="June" year="2016"/> </front> </reference> </references></back> </rfc>