<?xml version='1.0'encoding='utf-8'?>encoding='UTF-8'?> <!DOCTYPE rfc [ <!ENTITY nbsp " "> <!ENTITY zwsp "​"> <!ENTITY nbhy "‑"> <!ENTITY wj "⁠"> ]><?xml-stylesheet type="text/xsl" href="rfc2629.xslt" ?> <!-- generated by https://github.com/cabo/kramdown-rfc version 1.7.2 (Ruby 2.6.10) --><rfc xmlns:xi="http://www.w3.org/2001/XInclude" ipr="pre5378Trust200902" docName="draft-ietf-lamps-rfc8399bis-05" number="9549" category="std" consensus="true" submissionType="IETF" obsoletes="8399" updates="5280" tocInclude="true" sortRefs="true" symRefs="true"version="3"> <!-- xml2rfc v2v3 conversion 3.19.1 -->version="3" xml:lang="en"> <front> <title abbrev="I18n Updates to RFC 5280">Internationalization Updates to RFC 5280</title> <seriesInfoname="Internet-Draft" value="draft-ietf-lamps-rfc8399bis-05"/>name="RFC" value="9549"/> <author initials="R." surname="Housley" fullname="Russ Housley"> <organization abbrev="Vigil Security">Vigil Security, LLC</organization> <address> <postal><city>Herndon, VA</city> <country>US</country><city>Herndon</city> <region>VA</region> <country>United States of America</country> </postal> <email>housley@vigilsec.com</email> </address> </author> <date year="2024"month="January" day="18"/> <area>Security</area> <keyword>Internet-Draft</keyword>month="March"/> <area>SEC</area> <workgroup>lamps</workgroup> <keyword>Internationalized Email Address</keyword> <abstract><?line 81?><t>The updates to RFC 5280 described in this document provide alignment with the 2008 specification for Internationalized Domain Names (IDNs) and includes support for internationalized email addresses in X.509 certificates. Theupdate ensuresupdates ensure that name constraints fortraditionalemail addresses that contain only ASCII characters and internationalized email addresses are handled in the same manner. This document(once approved)obsoletes RFC 8399.</t> </abstract> </front> <middle><?line 90?><section anchor="intro"> <name>Introduction</name> <t>This document updates the Introduction in Section1,<xref target="RFC5280" section="1" sectionFormat="bare"/>, the Name Constraints certificate extension discussion in Section4.2.1.10,<xref target="RFC5280" section="4.2.1.10" sectionFormat="bare"/>, and the Processing Rules for Internationalized Names in Section7<xref target="RFC5280" section="7" sectionFormat="bare"/> of RFC 5280 <xref target="RFC5280"/> to provide alignment with the 2008 specification for Internationalized Domain Names (IDNs) and includes support for internationalized email addresses in X.509 certificates.</t> <t>An IDN in Unicode (native character) form contains at least one U-label <xref target="RFC5890"/>. IDNs are carried in certificates in ACE-encoded form. That is, all U-labels within an IDN are converted to A-labels. Conversion of a U-label to an A-label is described in <xref target="RFC5891"/>.</t> <t>The GeneralName structure supports many different name forms, including otherName for extensibility. RFC 8398 <xref target="RFC8398"/> specifies the SmtpUTF8Mailbox for internationalized email addresses.</t> <t>Note that Internationalized Domain Names in Applications specifications published in 2003 (IDNA2003) <xref target="RFC3490"/> and 2008 (IDNA2008) <xref target="RFC5890"/> both refer to the Punycode algorithm for conversion <xref target="RFC3492"/>.</t> <t>Note that characters in the Unicode Category“Symbol, Other”"Symbol, Other" (So) are specifically not included in IDNA2003 <xref target="RFC3490"/> or IDNA2008 <xref target="RFC5890"/>; the derived property values forcharactercharacters in this category are calculated as DISALLOWED. Thus, some characters that are allowed under the Unicode IDNA Compatibility Processing <xref target="UTS46"/> are not allowed under this specification. For instance,☕.example♚.example, which contains the Unicode character U+1F0A1 (BLACK CHESS KING), results inina failure under this specification, but it becomesxn--53h.examplexn&nbhy;&nbhy;45h.example under <xref target="UTS46"/>.</t> <section anchor="terms"> <name>Terminology</name><t>The<t> The key words "<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 "<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> <?line -18?>here. </t> </section> <section anchor="changes-since-rfc-8399"> <name>Changes since RFC 8399</name> <t>In some cases, <xref target="RFC8399"/> required conversion of A-labels to U-labels in order to process name constraints for internationalized email addresses. Thisleadled to implementation complexity and at least two security vulnerabilities. One summary of the vulnerabilitiesancan be found in <xref target="DDHQ"/>. Now, allInternationalized Domain Names (IDNs)IDNs are carried and processed as A-labels.</t> <t>The Introduction provides a warning to implementers about the handling of characters in the Unicode Category“Symbol, Other”"Symbol, Other" (So), which includes emoji characters.</t> </section> </section> <section anchor="updates-to-rfc-5280"> <name>Updates to RFC 5280</name> <t>This section provides updates to several paragraphs of <xref target="RFC5280"/>. For clarity, if the entire section is not replaced, then the original text and the replacement text are shown.</t> <section anchor="update-in-the-introduction-section-1"> <name>Update in the Introduction (Section 1)</name> <t>This update provides references for IDNA2008.</t> <t>OLD</t><artwork><![CDATA[ *<blockquote> <ul><li> Enhanced support for internationalized names is specified in Section 7, with rules for encoding and comparing Internationalized Domain Names, Internationalized Resource Identifiers (IRIs), and distinguished names. These rules are aligned with comparison rules established in current RFCs, including[RFC3490], [RFC3987],<xref target="RFC3490"/>, <xref target="RFC3987"/>, and[RFC4518]. ]]></artwork><xref target="RFC4518"/>. </li></ul> </blockquote> <t>NEW</t><artwork><![CDATA[ *<blockquote> <ul><li> Enhanced support for internationalized names is specified in Section 7, with rules for encoding and comparing Internationalized Domain Names, Internationalized Resource Identifiers (IRIs), and distinguished names. These rules are aligned with comparison rules established in current RFCs, including[RFC3987], [RFC4518], [RFC5890],<xref target="RFC3987"/>, <xref target="RFC4518"/>, <xref target="RFC5890"/>, and[RFC5891]. ]]></artwork><xref target="RFC5891"/>. </li> </ul> </blockquote> </section> <section anchor="update-in-name-constraints-section-42110"> <name>Update in Name Constraints (Section 4.2.1.10)</name> <t>This update removes the ability to include constraints for a particular mailbox. This capability was not used, and removing it allows name constraints to apply to email addresses in rfc822Name and SmtpUTF8Mailbox <xref target="RFC8398"/> within otherName.</t> <t>OLD</t><artwork><![CDATA[<blockquote> A name constraint for Internet mail addressesMAY<bcp14>MAY</bcp14> specify a particular mailbox, all addresses at a particular host, or all mailboxes in a domain. To indicate a particular mailbox, the constraint is the complete mail address. For example, "root@example.com" indicates the root mailbox on the host "example.com". To indicate all Internet mail addresses on a particular host, the constraint is specified as the host name. For example, the constraint "example.com" is satisfied by any mail address at the host "example.com". To specify any address within a domain, the constraint is specified with a leading period (as with URIs). For example, ".example.com" indicates all the Internet mail addresses in the domain "example.com", but not Internet mail addresses on the host "example.com".]]></artwork></blockquote> <t>NEW</t><artwork><![CDATA[<blockquote> A name constraint for Internet mail addressesMAY<bcp14>MAY</bcp14> specify all addresses at a particular host or all mailboxes in a domain. To indicate all Internet mail addresses on a particular host, the constraint is specified as the host name. For example, the constraint "example.com" is satisfied by any mail address at the host "example.com". To specify any address within a domain, the constraint is specified with a leading period (as with URIs). For example, ".example.com" indicates all the Internet mail addresses in the domain "example.com" but not Internet mail addresses on the host "example.com".]]></artwork></blockquote> </section> <section anchor="update-in-idns-in-generalname-section-72"> <name>Update in IDNs in GeneralName (Section 7.2)</name> <t>This update aligns with IDNA2008. Since all ofSection 7.2<xref target="RFC5280" section="7.2" sectionFormat="of"/> is replaced, the OLD text is not provided.</t> <t>NEW</t><artwork><![CDATA[<blockquote> <t> Internationalized Domain Names (IDNs) may be included in certificates and CRLs in the subjectAltName and issuerAltName extensions, name constraints extension, authority information access extension, subject information access extension, CRL distribution points extension, and issuing distribution point extension. Each of these extensions uses the GeneralName type; one choice in GeneralName is the dNSName field, which is defined as typeIA5String.IA5String.</t> <t> IA5String is limited to the set of ASCII characters. To accommodate IDNs, U-labels are converted to A-labels. The A-label is the encoding of the U-label according to the Punycode algorithm[RFC3492]<xref target="RFC3492"/> with the ACE prefix "xn--" added at the beginning of thestring.string.</t> <t> When comparing DNS names for equality, conforming implementationsMUST<bcp14>MUST</bcp14> perform a case-insensitive exact match on the entire DNS name. When evaluating name constraints, conforming implementationsMUST<bcp14>MUST</bcp14> perform a case-insensitive exact match on a label-by-label basis. As noted in Section4.2.1.10,<xref target="RFC5280" section="4.2.1.10" sectionFormat="bare"/>, any DNS name that may be constructed by adding labels to the left-hand side of the domain name given as the constraint is considered to fall within the indicatedsubtree.subtree.</t> <t> Implementations that have a user interfaceSHOULD<bcp14>SHOULD</bcp14> convert IDNs to Unicode for display. Specifically, conforming implementations convert A-labels to U-labels for displaypurposes.purposes.</t> <t> Implementation consideration: There are increased memory requirements for IDNs. An IDN ACE label will begin with the four additional characters "xn--", and an IDN can require as many as five ASCII characters to specify a single internationalcharacter. ]]></artwork>character.</t> </blockquote> </section> <section anchor="update-in-idns-in-distinguished-names-section-73"> <name>Update in IDNs in Distinguished Names (Section 7.3)</name> <t>This update aligns with IDNA2008.</t> <t>OLD</t><artwork><![CDATA[<blockquote> Domain Names may also be represented as distinguished names using domain components in the subject field, the issuer field, the subjectAltName extension, or the issuerAltName extension. As with the dNSName in the GeneralName type, the value of this attribute is defined as an IA5String. Each domainComponent attribute represents a single label. To represent a label from an IDN in the distinguished name, the implementationMUST<bcp14>MUST</bcp14> perform the "ToASCII" label conversion specified in Section 4.1 of RFC 3490. The labelSHALL<bcp14>SHALL</bcp14> be considered a "stored string". That is, the AllowUnassigned flagSHALL NOT<bcp14>SHALL NOT</bcp14> be set.]]></artwork></blockquote> <t>NEW</t><artwork><![CDATA[<blockquote> Domain names may also be represented as distinguished names using domain components in the subject field, the issuer field, the subjectAltName extension, or the issuerAltName extension. As with the dNSName in the GeneralName type, the value of this attribute is defined as an IA5String. Each domainComponent attribute represents a single label. To represent a label from an IDN in the distinguished name, the implementationMUST<bcp14>MUST</bcp14> convert all U-labels to A-labels.]]></artwork></blockquote> </section> <section anchor="update-in-internationalized-electronic-mail-addresses-section-75"> <name>Update in Internationalized Electronic Mail Addresses (Section 7.5)</name> <t>This update aligns with IDNA2008 and <xref target="RFC8398"/>. Since all ofSection 7.5<xref target="RFC5280" section="7.5" sectionFormat="of"/> is replaced, the OLD text is not provided.</t> <t>NEW</t><artwork><![CDATA[<blockquote> <t> Electronic Mail addresses may be included in certificates and CRLs in the subjectAltName and issuerAltName extensions, name constraints extension, authority information access extension, subject information access extension, issuing distribution point extension, or CRL distribution points extension. Each of these extensions uses the GeneralName construct. If the email address includes an IDN but the local-part of the email address can be represented in ASCII, then the email address is placed in the rfc822Name choice of GeneralName, which is defined as type IA5String. If the local-part of the internationalized email address cannot be represented in ASCII, then the internationalized email address is placed in the otherName choice of GeneralName using the conventions in RFC 8398[RFC8398].<xref target="RFC8398"/>. </t> <t> When the host-part contains an IDN, conforming implementationsMUST<bcp14>MUST</bcp14> convert all U-labels to A-labels.7.5.1.</t> <t>7.5.1. Local-Part Contains Only ASCIICharactersCharacters</t> <t> Two email addresses are considered to matchif: 1) Theif:</t> <ol type="%d)"><li>The local-part of each name is an exact match,AND 2) TheAND</li> <li>The host-part of each name matches using a case-insensitive ASCIIcomparison.comparison.</li> </ol> <t> Implementations that have a user interfaceSHOULD<bcp14>SHOULD</bcp14> convert the host-part of internationalized email addresses specified in these extensions to Unicode before display. Specifically, conforming implementations convert A-labels to U-labels for displaypurposes.purposes.</t> <t> 7.5.2. Local-Part Contains Non-ASCIICharactersCharacters</t> <t> When the local-part contains non-ASCII characters, conforming implementationsMUST<bcp14>MUST</bcp14> place the internationalized email address in the SmtpUTF8Mailbox within the otherName choice of GeneralName as specified in Section3<xref target="RFC8398" section="3" sectionFormat="bare"/> of RFC 8398[RFC8398].<xref target="RFC8398"/>. Note that the UTF8 encoding of the internationalized email addressMUST NOT<bcp14>MUST NOT</bcp14> contain a Byte-Order-Mark (BOM)[RFC3629]<xref target="RFC3629"/> to aid comparison. The email address local-part within the SmtpUTF8MailboxMUST<bcp14>MUST</bcp14> conform to the requirements of[RFC6530]<xref target="RFC6530"/> and[RFC6531].<xref target="RFC6531"/>.</t> <t> Two email addresses are considered to matchif: 1) Theif:</t> <ol type="%d)"><li>The local-part of each name is an exact match,AND 2) TheAND</li> <li>The host-part of each name matches using a case-insensitive ASCIIcomparison.comparison.</li> </ol> <t> Implementations that have a user interfaceSHOULD<bcp14>SHOULD</bcp14> convert the host-part of internationalized email addresses specified in these extensions to Unicode before display. Specifically, conforming implementations convert A-labels to U-labels for display purposes.]]></artwork></t> </blockquote> </section> </section> <section anchor="sec-cons"> <name>Security Considerations</name> <t>The SecurityConsiderationConsiderations related toIDNA2008internationalized names in <xref section="4" sectionFormat="of" target="RFC5890"/> are relevant to thisspecification.</t>specification. </t> <t>ConformingCAsCertification Authorities (CAs) <bcp14>SHOULD</bcp14> ensure that IDNs are valid according to IDNA2008, which is defined in <xref target="RFC5890"/>, <xref target="RFC5891"/>, <xref target="RFC5892"/>, <xref target="RFC5893"/>, <xref target="RFC5894"/>, and the updates to these documents. Failure to use valid A-labels may yield a domain name that cannot be correctly represented in the Domain Name System (DNS). In addition, the CA/Browser Forum offers some guidance regarding internal server names in certificates <xref target="CABF"/>.</t> <t>An earlier version of this specification <xref target="RFC8399"/> required conversion of A-labels to U-labels in order to process name constraints for internationalized email addresses in SmtpUTF8Mailbox other names. This lead to implementation complexity and at least two security vulnerabilities. Now, allInternationalized Domain Names (IDNs)IDNs are carried and processed as A-labels.</t> </section> <section anchor="iana"> <name>IANA Considerations</name> <t>This document has no IANA actions.</t> </section><section numbered="false" anchor="acknowledgements"> <name>Acknowledgements</name> <t>Thanks to David Benjamin and Wei Chuang for identifying the issue and a solution.</t> <t>Thanks to Takahiro Nemoto, John Klensin, Mike Ounsworth, and Orie Steele for their careful review and thoughtful comments.</t> </section></middle> <back> <references> <name>References</name> <references anchor="sec-normative-references"> <name>Normative References</name><reference anchor="RFC2119"> <front> <title>Key words for use in RFCs to Indicate Requirement Levels</title> <author fullname="S. Bradner" initials="S." surname="Bradner"/> <date month="March" year="1997"/> <abstract> <t>In many standards track documents several words are used to signify the requirements in the specification. These words are often capitalized. This document defines these words as they should be interpreted in IETF documents. This document specifies an Internet Best Current Practices for the Internet Community, and requests discussion and suggestions for improvements.</t> </abstract> </front> <seriesInfo name="BCP" value="14"/> <seriesInfo name="RFC" value="2119"/> <seriesInfo name="DOI" value="10.17487/RFC2119"/> </reference> <reference anchor="RFC3492"> <front> <title>Punycode: A Bootstring encoding of Unicode for Internationalized Domain Names in Applications (IDNA)</title> <author fullname="A. Costello" initials="A." surname="Costello"/> <date month="March" year="2003"/> <abstract> <t>Punycode is a simple and efficient transfer encoding syntax designed for use with Internationalized Domain Names in Applications (IDNA). It uniquely and reversibly transforms a Unicode string into an ASCII string. ASCII characters in the Unicode string are represented literally, and non-ASCII characters are represented by ASCII characters that are allowed in host name labels (letters, digits, and hyphens). This document defines a general algorithm called Bootstring that allows a string of basic code points to uniquely represent any string of code points drawn from a larger set. Punycode is an instance of Bootstring that uses particular parameter values specified by this document, appropriate for IDNA. [STANDARDS-TRACK]</t> </abstract> </front> <seriesInfo name="RFC" value="3492"/> <seriesInfo name="DOI" value="10.17487/RFC3492"/> </reference> <reference anchor="RFC3629"> <front> <title>UTF-8, a transformation format of ISO 10646</title> <author fullname="F. Yergeau" initials="F." surname="Yergeau"/> <date month="November" year="2003"/> <abstract> <t>ISO/IEC 10646-1 defines a large character set called the Universal Character Set (UCS) which encompasses most of the world's writing systems. The originally proposed encodings of the UCS, however, were not compatible with many current applications and protocols, and this has led to the development of UTF-8, the object of this memo. UTF-8 has the characteristic of preserving the full US-ASCII range, providing compatibility with file systems, parsers and other software that rely on US-ASCII values but are transparent to other values. This memo obsoletes and replaces RFC 2279.</t> </abstract> </front> <seriesInfo name="STD" value="63"/> <seriesInfo name="RFC" value="3629"/> <seriesInfo name="DOI" value="10.17487/RFC3629"/> </reference> <reference anchor="RFC3987"> <front> <title>Internationalized Resource Identifiers (IRIs)</title> <author fullname="M. Duerst" initials="M." surname="Duerst"/> <author fullname="M. Suignard" initials="M." surname="Suignard"/> <date month="January" year="2005"/> <abstract> <t>This document defines a new protocol element, the Internationalized Resource Identifier (IRI), as a complement of the Uniform Resource Identifier (URI). An IRI is a sequence of characters from the Universal Character Set (Unicode/ISO 10646). A mapping from IRIs to URIs is defined, which means that IRIs can be used instead of URIs, where appropriate, to identify resources.</t> <t>The approach of defining a new protocol element was chosen instead of extending or changing the definition of URIs. This was done in order to allow a clear distinction and to avoid incompatibilities with existing software. Guidelines are provided for the use and deployment of IRIs in various protocols, formats, and software components that currently deal with URIs.</t> </abstract> </front> <seriesInfo name="RFC" value="3987"/> <seriesInfo name="DOI" value="10.17487/RFC3987"/> </reference> <reference anchor="RFC4518"> <front> <title>Lightweight Directory Access Protocol (LDAP): Internationalized String Preparation</title> <author fullname="K. Zeilenga" initials="K." surname="Zeilenga"/> <date month="June" year="2006"/> <abstract> <t>The previous Lightweight Directory Access Protocol (LDAP) technical specifications did not precisely define how character string matching is to be performed. This led to a number of usability and interoperability problems. This document defines string preparation algorithms for character-based matching rules defined for use in LDAP. [STANDARDS-TRACK]</t> </abstract> </front> <seriesInfo name="RFC" value="4518"/> <seriesInfo name="DOI" value="10.17487/RFC4518"/> </reference> <reference anchor="RFC5280"> <front> <title>Internet X.509 Public Key Infrastructure Certificate and Certificate Revocation List (CRL) Profile</title> <author fullname="D. Cooper" initials="D." surname="Cooper"/> <author fullname="S. Santesson" initials="S." surname="Santesson"/> <author fullname="S. Farrell" initials="S." surname="Farrell"/> <author fullname="S. Boeyen" initials="S." surname="Boeyen"/> <author fullname="R. Housley" initials="R." surname="Housley"/> <author fullname="W. Polk" initials="W." surname="Polk"/> <date month="May" year="2008"/> <abstract> <t>This memo profiles the X.509 v3 certificate and X.509 v2 certificate revocation list (CRL) for use in the Internet. An overview of this approach and model is provided as an introduction. The X.509 v3 certificate format is described in detail, with additional information regarding the format and semantics of Internet name forms. Standard certificate extensions are described and two Internet-specific extensions are defined. A set of required certificate extensions is specified. The X.509 v2 CRL format is described in detail along with standard and Internet-specific extensions. An algorithm for X.509 certification path validation is described. An ASN.1 module and examples are provided in the appendices. [STANDARDS-TRACK]</t> </abstract> </front> <seriesInfo name="RFC" value="5280"/> <seriesInfo name="DOI" value="10.17487/RFC5280"/> </reference> <reference anchor="RFC5890"> <front> <title>Internationalized Domain Names for Applications (IDNA): Definitions and Document Framework</title> <author fullname="J. Klensin" initials="J." surname="Klensin"/> <date month="August" year="2010"/> <abstract> <t>This document is one of a collection that, together, describe the protocol and usage context for a revision of Internationalized Domain Names for Applications (IDNA), superseding the earlier version. It describes the document collection and provides definitions and other material that are common to the set. [STANDARDS-TRACK]</t> </abstract> </front> <seriesInfo name="RFC" value="5890"/> <seriesInfo name="DOI" value="10.17487/RFC5890"/> </reference> <reference anchor="RFC5891"> <front> <title>Internationalized Domain Names in Applications (IDNA): Protocol</title> <author fullname="J. Klensin" initials="J." surname="Klensin"/> <date month="August" year="2010"/> <abstract> <t>This document is the revised protocol definition for Internationalized Domain Names (IDNs). The rationale for changes, the relationship to the older specification, and important terminology are provided in other documents. This document specifies the protocol mechanism, called Internationalized Domain Names in Applications (IDNA), for registering and looking up IDNs in a way that does not require changes to the DNS itself. IDNA is only meant for processing domain names, not free text. [STANDARDS-TRACK]</t> </abstract> </front> <seriesInfo name="RFC" value="5891"/> <seriesInfo name="DOI" value="10.17487/RFC5891"/> </reference> <reference anchor="RFC5892"> <front> <title>The Unicode Code Points and Internationalized Domain Names for Applications (IDNA)</title> <author fullname="P. Faltstrom" initials="P." role="editor" surname="Faltstrom"/> <date month="August" year="2010"/> <abstract> <t>This document specifies rules for deciding whether a code point, considered in isolation or in context, is a candidate for inclusion in an Internationalized Domain Name (IDN).</t> <t>It is part of the specification of Internationalizing Domain Names in Applications 2008 (IDNA2008). [STANDARDS-TRACK]</t> </abstract> </front> <seriesInfo name="RFC" value="5892"/> <seriesInfo name="DOI" value="10.17487/RFC5892"/> </reference> <reference anchor="RFC5893"> <front> <title>Right-to-Left Scripts for Internationalized Domain Names for Applications (IDNA)</title> <author fullname="H. Alvestrand" initials="H." role="editor" surname="Alvestrand"/> <author fullname="C. Karp" initials="C." surname="Karp"/> <date month="August" year="2010"/> <abstract> <t>The use of right-to-left scripts in Internationalized Domain Names (IDNs) has presented several challenges. This memo provides a new Bidi rule for Internationalized Domain Names for Applications (IDNA) labels, based on the encountered problems with some scripts and some shortcomings in the 2003 IDNA Bidi criterion. [STANDARDS-TRACK]</t> </abstract> </front> <seriesInfo name="RFC" value="5893"/> <seriesInfo name="DOI" value="10.17487/RFC5893"/> </reference> <reference anchor="RFC6530"> <front> <title>Overview and Framework for Internationalized Email</title> <author fullname="J. Klensin" initials="J." surname="Klensin"/> <author fullname="Y. Ko" initials="Y." surname="Ko"/> <date month="February" year="2012"/> <abstract> <t>Full use of electronic mail throughout the world requires that (subject to other constraints) people be able to use close variations on their own names (written correctly in their own languages and scripts) as mailbox names in email addresses. This document introduces a series of specifications that define mechanisms and protocol extensions needed to fully support internationalized email addresses. These changes include an SMTP extension and extension of email header syntax to accommodate UTF-8 data. The document set also includes discussion of key assumptions and issues in deploying fully internationalized email. This document is a replacement for RFC 4952; it reflects additional issues identified since that document was published. [STANDARDS-TRACK]</t> </abstract> </front> <seriesInfo name="RFC" value="6530"/> <seriesInfo name="DOI" value="10.17487/RFC6530"/> </reference> <reference anchor="RFC6531"> <front> <title>SMTP Extension for Internationalized Email</title> <author fullname="J. Yao" initials="J." surname="Yao"/> <author fullname="W. Mao" initials="W." surname="Mao"/> <date month="February" year="2012"/> <abstract> <t>This document specifies an SMTP extension for transport and delivery of email messages with internationalized email addresses or header information. [STANDARDS-TRACK]</t> </abstract> </front> <seriesInfo name="RFC" value="6531"/> <seriesInfo name="DOI" value="10.17487/RFC6531"/> </reference> <reference anchor="RFC8174"> <front> <title>Ambiguity of Uppercase vs Lowercase in RFC 2119 Key Words</title> <author fullname="B. Leiba" initials="B." surname="Leiba"/> <date month="May" year="2017"/> <abstract> <t>RFC 2119 specifies common key words that may be used in protocol specifications. This document aims to reduce the ambiguity by clarifying that only UPPERCASE usage of the key words have the defined special meanings.</t> </abstract> </front> <seriesInfo name="BCP" value="14"/> <seriesInfo name="RFC" value="8174"/> <seriesInfo name="DOI" value="10.17487/RFC8174"/> </reference> <reference anchor="RFC8398"> <front> <title>Internationalized Email Addresses in X.509 Certificates</title> <author fullname="A. Melnikov" initials="A." role="editor" surname="Melnikov"/> <author fullname="W. Chuang" initials="W." role="editor" surname="Chuang"/> <date month="May" year="2018"/> <abstract> <t>This document defines a new name form for inclusion in the otherName field of an X.509 Subject Alternative Name and Issuer Alternative Name extension that allows a certificate subject to be associated with an internationalized email address.</t> <t>This document updates RFC 5280.</t> </abstract> </front> <seriesInfo name="RFC" value="8398"/> <seriesInfo name="DOI" value="10.17487/RFC8398"/> </reference><xi:include href="https://bib.ietf.org/public/rfc/bibxml/reference.RFC.2119.xml"/> <xi:include href="https://bib.ietf.org/public/rfc/bibxml/reference.RFC.3492.xml"/> <xi:include href="https://bib.ietf.org/public/rfc/bibxml/reference.RFC.3629.xml"/> <xi:include href="https://bib.ietf.org/public/rfc/bibxml/reference.RFC.3987.xml"/> <xi:include href="https://bib.ietf.org/public/rfc/bibxml/reference.RFC.4518.xml"/> <xi:include href="https://bib.ietf.org/public/rfc/bibxml/reference.RFC.5280.xml"/> <xi:include href="https://bib.ietf.org/public/rfc/bibxml/reference.RFC.5890.xml"/> <xi:include href="https://bib.ietf.org/public/rfc/bibxml/reference.RFC.5891.xml"/> <xi:include href="https://bib.ietf.org/public/rfc/bibxml/reference.RFC.5892.xml"/> <xi:include href="https://bib.ietf.org/public/rfc/bibxml/reference.RFC.5893.xml"/> <xi:include href="https://bib.ietf.org/public/rfc/bibxml/reference.RFC.6530.xml"/> <xi:include href="https://bib.ietf.org/public/rfc/bibxml/reference.RFC.6531.xml"/> <xi:include href="https://bib.ietf.org/public/rfc/bibxml/reference.RFC.8174.xml"/> <xi:include href="https://bib.ietf.org/public/rfc/bibxml/reference.RFC.8398.xml"/> </references> <references anchor="sec-informative-references"> <name>Informative References</name><reference anchor="RFC3490"> <front> <title>Internationalizing Domain Names in Applications (IDNA)</title> <author fullname="P. Faltstrom" initials="P." surname="Faltstrom"/> <author fullname="P. Hoffman" initials="P." surname="Hoffman"/> <author fullname="A. Costello" initials="A." surname="Costello"/> <date month="March" year="2003"/> <abstract> <t>Until now, there has been no standard method for domain names to use characters outside the ASCII repertoire. This document defines internationalized domain names (IDNs) and a mechanism called Internationalizing Domain Names in Applications (IDNA) for handling them in a standard fashion. IDNs use characters drawn from a large repertoire (Unicode), but IDNA allows the non-ASCII characters to be represented using only the ASCII characters already allowed in so-called host names today. This backward-compatible representation is required in existing protocols like DNS, so that IDNs can be introduced with no changes to the existing infrastructure. IDNA is only meant for processing domain names, not free text. [STANDARDS-TRACK]</t> </abstract> </front> <seriesInfo name="RFC" value="3490"/> <seriesInfo name="DOI" value="10.17487/RFC3490"/> </reference> <reference anchor="RFC5894"> <front> <title>Internationalized Domain Names for Applications (IDNA): Background, Explanation, and Rationale</title> <author fullname="J. Klensin" initials="J." surname="Klensin"/> <date month="August" year="2010"/> <abstract> <t>Several years have passed since the original protocol for Internationalized Domain Names (IDNs) was completed and deployed. During that time, a number of issues have arisen, including the need to update the system to deal with newer versions of Unicode. Some of these issues require tuning of the existing protocols and the tables on which they depend. This document provides an overview of a revised system and provides explanatory material for its components. This document is not an Internet Standards Track specification; it is published for informational purposes.</t> </abstract> </front> <seriesInfo name="RFC" value="5894"/> <seriesInfo name="DOI" value="10.17487/RFC5894"/> </reference> <reference anchor="RFC8399"> <front> <title>Internationalization Updates to RFC 5280</title> <author fullname="R. Housley" initials="R." surname="Housley"/> <date month="May" year="2018"/> <abstract> <t>The updates to RFC 5280 described in this document provide alignment with the 2008 specification for Internationalized Domain Names (IDNs) and add support for internationalized email addresses in X.509 certificates.</t> </abstract> </front> <seriesInfo name="RFC" value="8399"/> <seriesInfo name="DOI" value="10.17487/RFC8399"/> </reference><xi:include href="https://bib.ietf.org/public/rfc/bibxml/reference.RFC.3490.xml"/> <xi:include href="https://bib.ietf.org/public/rfc/bibxml/reference.RFC.5894.xml"/> <xi:include href="https://bib.ietf.org/public/rfc/bibxml/reference.RFC.8399.xml"/> <reference anchor="CABF" target="https://cabforum.org/internal-names/"> <front> <title>Internal Server Names and IP Address Requirements for SSL: Guidance on the Deprecation of Internal Server Names and Reserved IP Addresses provided by the CA/Browser Forum</title> <author> <organization>CA/Browser Forum</organization> </author> <date year="2012" month="June"/> </front><seriesInfo name="Version" value="1.0"/><refcontent>Version 1.0</refcontent> </reference> <reference anchor="DDHQ" target="https://securitylabs.datadoghq.com/articles/openssl-november-1-vulnerabilities/"> <front> <title>The OpenSSL punycode vulnerability (CVE-2022-3602): Overview, detection, exploitation, and remediation</title> <author> <organization>Datadog Security Labs</organization> </author> <date year="2022" month="November" day="01"/> </front> </reference> <reference anchor="UTS46" target="https://www.unicode.org/reports/tr46"> <front> <title>Unicode Technical Standard #46: Unicode IDNA Compatibility Processing</title> <author initials="M." surname="Davis" fullname="Mark Davis"> <organization/> </author> <author initials="M." surname="Suignard" fullname="Michel Suignard"> <organization/> </author> <date year="2023" month="September"/> </front> <refcontent>Revision 31, The Unicode Consortium, Mountain View</refcontent> </reference> </references> </references> <section numbered="false" anchor="acknowledgements"> <name>Acknowledgements</name> <t>Thanks to <contact fullname="David Benjamin"/> and <contact fullname="Wei Chuang"/> for identifying the issue and a solution.</t> <t>Thanks to <contact fullname="Takahiro Nemoto"/>, <contact fullname="John Klensin"/>, <contact fullname="Mike Ounsworth"/>, and <contact fullname="Orie Steele"/> for their careful review and thoughtful comments.</t> </section> </back><!-- ##markdown-source: H4sIAOp4qWUAA+1b23IbuZm+x1Ng6QtLKZIWKcmWmOwkNCXH2tXBEaWZTblc KbAbJDFuNjiNbtFcl6fyEluVi6Qqz7KPMk+y//8D6EY3qYMzudjdmiv2AYf/ 8P3HBjudDjO5SOM/iUSncsDzrJBMLbMBX2bycP/V0U1WmLy/t3e812exjlKx gFFxJqZ5R8l82knEYmk62TQ62j8+nijT2TtkemJ0InNpBhyfsmIZC7o77B/t sUjkA27ymEU6NTI1Bbx4jvs+Z0s1YJznOoIna2mew43RWZ7JqQmerBfhg1zl CZD0/CzNZZaKXOlUJOo/6YLf2p1hSX79ZkT7P2diMsnkHU7pHd0zxBSThTIG lrhZL2H1s9ObN0xkUgz4WEZFpvI1+7iC57SpzDsnKBGGKw14f69/0NnrdXpH 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