<?xmlversion='1.0' encoding='utf-8'?>version="1.0" encoding="utf-8"?> <!DOCTYPE rfc [ <!ENTITY nbsp " "> <!ENTITY zwsp "​"> <!ENTITY nbhy "‑"> <!ENTITY wj "⁠"> ]><?xml-stylesheet type='text/xsl' href='rfc2629.xslt' ?> <?rfc toc="yes"?> <?rfc symrefs="yes"?> <?rfc sortrefs="yes"?> <?rfc compact="yes"?> <?rfc strict="yes"?><rfc xmlns:xi="http://www.w3.org/2001/XInclude" category="std"consensus="yes"consensus="true" ipr="trust200902" docName="draft-ietf-extra-processimip-09" number="9671" obsoletes="" updates="" submissionType="IETF" xml:lang="en" tocInclude="true" symRefs="true" sortRefs="true" version="3"><!-- xml2rfc v2v3 conversion 3.12.2 --><front> <title abbrev="SieveProcess iMIP">SieveExtension for Processing Calendar Attachments">Sieve Email Filtering: Extension for Processing Calendar Attachments</title> <seriesInfoname="Internet-Draft" value="draft-ietf-extra-processimip-09"/>name="RFC" value="9671"/> <author initials="K." surname="Murchison" fullname="Kenneth Murchison"> <organization abbrev="Fastmail">Fastmail US LLC</organization> <address> <postal> <street>1429 WalnutStreet -Street, Suite 1201</street> <city>Philadelphia</city> <region>PA</region> <code>19102</code><country>USA</country><country>United States of America</country> </postal> <email>murch@fastmailteam.com</email> </address> </author> <author initials="R." surname="Signes" fullname="Ricardo Signes"> <organization abbrev="Fastmail">Fastmail US LLC</organization> <address> <postal> <street>1429 WalnutStreet -Street, Suite 1201</street> <city>Philadelphia</city> <region>PA</region> <code>19102</code><country>USA</country><country>United States of America</country> </postal> <email>rjbs@fastmailteam.com</email> </address> </author> <author initials="M." surname="Horsfall" fullname="Matthew Horsfall"> <organization abbrev="Fastmail">Fastmail US LLC</organization> <address> <postal> <street>1429 WalnutStreet -Street, Suite 1201</street> <city>Philadelphia</city> <region>PA</region> <code>19102</code><country>USA</country><country>United States of America</country> </postal> <email>alh@fastmailteam.com</email> </address> </author><date/><date month="October" year="2024"/> <area>ART</area><!-- <workgroup>EXTRA</workgroup>--><workgroup>extra</workgroup> <keyword>Sieve</keyword> <abstract> <t>This document describes the "processcalendar" extension to the Sieve email filtering language. The "processcalendar" extension gives Sieve the ability to process machine-readable calendar data that is encapsulated in an email message using Multipurpose Internet Mail Extensions (MIME).</t> </abstract><!-- <note title="Open Issues"> <ul> </ul> </note> --></front> <middle> <section numbered="true" toc="default"> <name>Introduction</name> <t>Users frequently receive invites, replies, and cancellations for events, tasks, etc. via Internet mail messages. It is sometimes desirable to have such messages automatically parsed and the enclosed calendar data added to, updated on, or deleted from the user's calendars.</t><t>Typically<t>Typically, such messages are based on the<xref target="RFC6047" format="default">iCalendariCalendar Message-Based Interoperability Protocol(iMIP)</xref>.(iMIP) <xref target="RFC6047" format="default"></xref>. However, sometimes the enclosed iCalendar <xreftarget="RFC5545">iCalendar</xref>target="RFC5545"></xref> data does not include aniTIPiCalendar Transport-Independent Interoperability Protocol (iTIP) method property (see <xref target="RFC5546" section="1.4" sectionFormat="comma"/>), or the enclosed data may be in some other machine-readable format<!-- (E.g. <xref target="I-D.ietf-calext-jscalendarbis">--> (E.g.(e.g., JSCalendar <xreftarget="RFC8984"> JSCalendar</xref>).target="RFC8984"></xref>). </t> <t>This document defines an extension to the Sieve language <xref target="RFC5228"format="default">Sieve language</xref>format="default"></xref> that enables scripts to process machine-readable calendar data that is encapsulated in an email message using MIME <xreftarget="RFC2045">MIME</xref>.target="RFC2045"></xref>. Specifically, this extension provides the ability to alter items on a user's calendars that are referenced in the encapsulated calendar data.</t> </section> <section numbered="true" toc="default"> <name>Conventions Used in This Document</name> <t>Conventions for notations are as in <xref target="RFC5228" section="1.1" format="default"/>, including use of the "Usage:" label for the definition of action and tagged arguments syntax.</t> <t>This document uses terminology and concepts from iCalendar <xreftarget="RFC5545">iCalendar</xref>target="RFC5545"></xref> and iTIP <xreftarget="RFC5546">iTIP</xref>target="RFC5546"></xref> to describe the processing of calendar data, but this extension can be used with any machine-readable calendar data format that can express similar concepts.</t><t>The<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 <xreftarget="RFC2119" format="default"/>target="RFC2119"/> <xreftarget="RFC8174" format="default"/>target="RFC8174"/> when, and only when, they appear in all capitals, as shownhere.</t>here. </t> </section> <section anchor="capability" numbered="true" toc="default"> <name>Capability Identifier</name> <t>Sieve interpreters that implement this extensionMUST<bcp14>MUST</bcp14> have an identifier of "processcalendar" for use with the capability mechanism.</t> </section> <section anchor="processcalendar" numbered="true" toc="default"> <name>Process Calendar Action</name><artwork<sourcecode name=""type="" align="left" alt=""><![CDATA[type="sieve"><![CDATA[ Usage: processcalendar [ :allowpublic ] [ :addresses <string-list> ] [ :updatesonly / :calendarid <string> ] [ :deletecancelled ] [ :organizers <ext-list-name: string> ] [ :outcome <variablename: string> ] [ :reason <variablename: string> ]]]></artwork>]]></sourcecode> <t>The "processcalendar" action is used to parse encapsulated calendar data and perform the appropriate action based on the content. If the calendar data is malformed in any way, itMUST<bcp14>MUST</bcp14> be ignored and no action is taken. Otherwise,based on the iTIP method (see <xref target="RFC5546" section="1.4" />) of the message,calendar objectsaremay be created, updated, or deleted from a givencalendar.</t>calendar. </t> <t>This action can be used with or without the "extlists" extension <xreftarget="RFC6134">"extlists"</xref> extension.target="RFC6134"></xref>. When the "extlists" extension is enabled in a script using <require "extlists">, the script can use the<xref target="organizers">:organizers</xref>:organizers argumentto(<xref target="organizers"></xref>) in the "processcalendar" action as described below. When the "extlists" extension is not enabled, the :organizers argumentMUST NOT<bcp14>MUST NOT</bcp14> be used andMUST<bcp14>MUST</bcp14> cause an error according to <xref target="RFC5228" />.</t> <t>This action can be used with or without the "variables" extension <xreftarget="RFC5229">"variables"</xref> extension.target="RFC5229"></xref>. When the "variables" extension is enabled in a script using <require "variables">, the script can use the<xref target="outcome">:outcome</xref>:outcome (<xref target="outcome"></xref>) and<xref target="reason">:reason</xref>:reason (<xref target="reason"></xref>) argumentstoin the "processcalendar" action as described below. When the "variables" extension is not enabled, the :outcome and :reason argumentsMUST NOT<bcp14>MUST NOT</bcp14> be used andMUST<bcp14>MUST</bcp14> cause an error according to <xref target="RFC5228" />.</t> <t>If a mailmessagesmessage contains calendar data in multiple MIME <xreftarget="RFC2045">MIME</xref>target="RFC2045"></xref> parts, this actionMUST<bcp14>MUST</bcp14> verify that the calendar data in each part are semantically equivalent to one another. If the data is found to be semantically different, the actionMUST NOT<bcp14>MUST NOT</bcp14> process the message. Otherwise, the actionMUST<bcp14>MUST</bcp14> only process one representation of the data.</t> <t>This actionMUST NOT<bcp14>MUST NOT</bcp14> make any changes to the participant status of the recipient when processing the calendar data. The mechanism for a recipient to change their participant status to an event is out of scope for this document.</t> <t>This actionSHOULD<bcp14>SHOULD</bcp14> remove alarms from calendar data before applying it to a calendar. Failure to do so could result in unwelcome notifications being triggered for the recipient.</t> <section anchor="allowpublic" numbered="true" toc="default"> <name>Allow Public Argument</name><!-- <t>The optional :allowpublic argument is used to tell the implementation that it can process calendar data that is not an iTIP message (it does not contain METHOD and/or ORGANIZER properties) or the METHOD is PUBLISH.</t> --><t>The optional :allowpublic argument is used to tell the implementation that it can process calendar data that does not contain any ATTENDEE properties, such as iTIP messages where the METHOD isPUBLISH,PUBLISH or non-iTIP messages where the calendar data does not contain METHOD and/or ORGANIZER properties.</t> <t>If used in conjunction with the<xref target="organizers"> :organizers</xref> argument, the implementation MUST NOT process non-iTIP messages.</t> <!-- <t>The optional :allowpublic:organizers argumentis used to tell the implementation that it can process calendar data that does not contain any ATTENDEE properties. If used in conjunction with the <xref target="organizers"> :organizers</xref> argument,(<xref target="organizers"></xref>), the implementationMUST NOT<bcp14>MUST NOT</bcp14> processcalendar data unless is it is a well-formed iTIP message, including those in which the METHOD is PUBLISH. Otherwise,non-iTIPcalendar data may be processed.</t> -->messages.</t> <t>If :allowpublic is omitted, the implementationMUST NOT<bcp14>MUST NOT</bcp14> process calendar data unless is it is a well-formed iTIP message and one of the recipient user's email addresses matches the Calendar User Address (see <xref target="RFC5545" section="3.3.3" format="default" />) of the intended target of the message, as determined by the iTIP method (see <xref target="RFC5546" section="1.4" />) of the message:</t><ul empty="true" spacing="normal"><ul> <li>"REPLY": Value of the"Organizer"ORGANIZER property (see <xref target="RFC5545"section="3.8.4.1" />)</li>section="3.8.4.3"/>)</li> <li>"REQUEST", "CANCEL", "ADD": Value of one of the"Attendee"ATTENDEE properties (see <xref target="RFC5545"section="3.8.4.3" />)</li>section="3.8.4.1"/>)</li> </ul> <t>The recipient user's email address matches the Calendar User Address of the target if the Calendar User Address is in the form of a mailto URI and the email address matches the "addr-spec" of the URI.</t> <t>An email address is considered to belong to the recipient if it is oneof:</t> <ol>of the following:</t> <ul> <li>an email address known by the implementation to be associated with the recipient,</li> <li>the final envelope recipient address if it's available to the implementation, or</li> <li>an address specified by the script writer via the<xref target="addresses">:addresses</xref> argument.</li> </ol>:addresses argument (<xref target="addresses"></xref>).</li> </ul> </section> <section anchor="addresses" numbered="true" toc="default"> <name>Addresses Argument</name> <t>The optional :addresses argument is used to specify email addresses that belong to the recipient in addition to the addresses known to the implementation.</t> </section> <section anchor="updatesonly" numbered="true" toc="default"> <name>Updates Only Argument</name> <t>The optional :updatesonly argument is used to limit the messages processed to those targeting existing calendar objects only. If the message contains a new calendar object (its unique identifier does not exist on any of the user's calendars), the implementationMUST NOT<bcp14>MUST NOT</bcp14> add the object to a calendar.</t> <t>If :updatesonly is omitted, new calendar objects may be added to one of the user's calendars.</t> <t>The :updatesonly and<xref target="calendarid">:calendarid</xref>:calendarid (<xref target="calendarid"></xref>) arguments are incompatible with each other. It is an error if both arguments are used in the same "processcalendar" action.</t> </section> <section anchor="calendarid" numbered="true" toc="default"> <name>Calendar ID Argument</name> <t>The optional :calendarid argument specifies the identifier of the calendar onto which new calendar objects should be placed.</t> <t>If :calendarid is omitted, new calendar objects will be placed on the user's "default" calendar as determined by the implementation.</t> <t>The<xref target="updatesonly">:updatesonly</xref>:updatesonly (<xref target="updatesonly"></xref>) and :calendarid arguments are incompatible with each other. It is an error if both arguments are used in the same "processcalendar" action.</t> </section> <section anchor="deletecancelled" numbered="true" toc="default"> <name>Delete Cancelled Argument</name> <t>The optional :deletecancelled argument is used to tell the implementation that if it receives a cancellation message, itSHOULD<bcp14>SHOULD</bcp14> remove the associated calendar object from the calendar.</t> <t>If :deletecancelled is omitted, the status of the associated calendar object will be set to cancelled and will remain on the calendar.</t> </section> <section anchor="organizers" numbered="true" toc="default"> <name>Organizers Argument</name> <t>The optional :organizers argument is used to specify an external list of email addresses from which the recipient is willing to accept public events, invites, updates, and cancellations. ImplementationsMUST NOT<bcp14>MUST NOT</bcp14> process calendar data unless is it is a well-formed iTIP message and one of the addresses in the external list matches the Calendar User Address of the"Organizer"ORGANIZER property. An email address in the external list matches the Calendar User Address of the"Organizer"ORGANIZER property if it is in the form of a mailto URI and the email address matches the "addr-spec" of the URI.</t> <t>If :organizers is omitted, no validation of the"Organizer"ORGANIZER property is performed.</t> </section> <section anchor="outcome" numbered="true" toc="default"> <name>Outcome Argument</name> <t>The optional :outcome argument specifies the name of a variable into which one of the following strings specifying the outcome of the action will be stored:</t><ul> <li>"no_action": No<dl newline="false" spacing="normal"> <dt>"no_action":</dt><dd>No action was performed(E.g.,(e.g., the message didn't contain calendar data, or the set of provided options prevented the message from beingprocessed).</li> <li>"added": Aprocessed).</dd> <dt>"added":</dt><dd>A new calendar object was added to acalendar</li> <li>"updated": Acalendar.</dd> <dt>"updated":</dt><dd>A calendarresourceobject was updated, cancelled, or removed from thecalendar.</li> <li>"error": Thecalendar.</dd> <dt>"error":</dt><dd>The message would have been processed but encountered an error in doingso.</li> </ul>so.</dd> </dl> </section> <section anchor="reason" numbered="true" toc="default"> <name>Reason Argument</name> <t>The optional :reason argument specifies the name of a variable into which a string describing the reason for the outcome will be stored. If no reason for the outcome is available, implementationsMUST<bcp14>MUST</bcp14> set the variable to the empty string.</t> <t>For example, an outcome of "no_action" may have a reason of "only processingupdates"updates", or an outcome of "error" may have a reason of "missing unique identifier".</t> </section> <section anchor="interaction" numbered="true" toc="default"> <name>Interaction with Other Sieve Actions</name> <t>The "processcalendar" action does not cancel Sieve's implicit keep action.</t> <t>The "processcalendar" action can only be executed once per script. A scriptMUST<bcp14>MUST</bcp14> fail with an appropriate error if it attempts to execute two or more "processcalendar" actions.</t> <t>The "processcalendar" action is incompatible with the Sieve "reject" and "ereject" actions <xref target="RFC5429"format="default"> reject and ereject</xref> actions.</t>format="default"></xref>. </t> </section> <section anchor="examples" numbered="true" toc="default"> <name>Examples</name> <t>The following example specifies email addresses belonging to the user and the identifier of the calendar onto which to place new calendar objects:</t><artwork<sourcecode name=""type="" align="left" alt=""><![CDATA[type="sieve"><![CDATA[ require [ "processcalendar" ]; processcalendar :addresses [ "me@example.com", "alsome@example.com" ] :calendarid "1ea6d86b-6c7f-48a2-bed3-2a4c40ec281a";]]></artwork>]]></sourcecode> <t>The following example tells the interpreter to process flight itineraries from a particular airline:</t><artwork<sourcecode name=""type="" align="left" alt=""><![CDATA[type="sieve"><![CDATA[ require [ "processcalendar" ]; if allof (address ["from", "sender"] "airline@example.com", header :contains "subject" "itinerary") { processcalendar :allowpublic; }]]></artwork>]]></sourcecode> <t>The following example adds headers to the message if calendar data isn't processed :</t><artwork<sourcecode name=""type="" align="left" alt=""><![CDATA[type="sieve"><![CDATA[ require [ "processcalendar", "variables", "editheader" ]; set "processcal_outcome" "no_action"; set "processcal_reason" ""; processcalendar :outcome "processcal_outcome" :reason "processcal_reason"; if not string :is "${processcal_outcome}" ["added", "updated"] { addheader "X-ProcessCal-Outcome" "${processcal_outcome}"; addheader "X-ProcessCal-Reason" "${processcal_reason}"; }]]></artwork>]]></sourcecode> </section> </section><!-- processcalendar --><section anchor="security" numbered="true" toc="default"> <name>Security Considerations</name> <t>This document describes a method for altering an electronic calendar without user interaction. As such, unless proper precautions are undertaken, it can be used as a vector for calendar abuse.</t> <t>It is critical that implementations correctly implement the behavior and restrictions described throughout this document. Security issues associated with processing unsolicited calendardata,data and methods for mitigating them are discussed in <xref target="CALSPAM" format="default"/>. Specifically:</t> <ul><li>Processcalendar MUST NOT<li>The "processcalendar" extension <bcp14>MUST NOT</bcp14> process any calendar data enclosed in a message flagged as spam and/or malicious. The<xref target="RFC5235">spamtest"spamtest" andvirustest</xref>"virustest" extensions <xref target="RFC5235"></xref> (or the<xref target="RFC5228">header</xref>header test <xref target="RFC5228"></xref> if messages are scanned outside of the Sieve interpreter) can be used to makeprocesscalendar"processcalendar" conditional on "safe" content.</li><li>Processcalendar SHOULD NOT<li>The "processcalendar" extension <bcp14>SHOULD NOT</bcp14> process calendar data received from a potentially malicious sender. The<xref target="RFC5228">addressaddress andenvelope</xref>envelope tests <xref target="RFC5228"></xref> (optionally along with the "extlists" extension <xreftarget="RFC6134">extlists</xref> extension)target="RFC6134"></xref>) can be used to create a "deny list" and makeprocesscalendar"processcalendar" conditional on the sender not being a member of that list.</li> <li>Similarly,processcalendar SHOULDthe "processcalendar" extension <bcp14>SHOULD</bcp14> only process calendar data received from a known sender. The<xref target="RFC5228">addressaddress andenvelope</xref>envelope tests <xref target="RFC5228"></xref> (optionally along with the "extlists" extension <xreftarget="RFC6134">extlists</xref> extension)target="RFC6134"></xref>) can be used to create an "allow list" and makeprocesscalendar"processcalendar" conditional on the sender being a member of that list.</li><li>Processcalendar SHOULD NOT<li>The "processcalendar" extension <bcp14>SHOULD NOT</bcp14> process calendar data received from an untrustworthy sender. Trustworthiness may depend on whether the message has a valid signature (see <xref target="RFC8551"/>) and/or on whether one or more of<xref target="RFC7208">Senderthe following passes or fails on the message: Sender Policy Framework(SPF)</xref>,(SPF) <xreftarget="RFC6376">DomainKeystarget="RFC7208"></xref>, DomainKeys Identified Mail (DKIM)Signatures</xref>,Signatures <xreftarget="RFC7489">Domain-basedtarget="RFC6376"></xref>, and Domain-based Message Authentication, Reporting, and Conformance(DMARC)</xref> passes or fails on the message.(DMARC) <xref target="RFC7489"></xref>. The mechanism by which a Sieve interpreter accesses the results of such checks is outside the scope of this document, but if the results are available in the message's header fields, the<xref target="RFC5228">header</xref>header test <xref target="RFC5228"></xref> can be used to makeprocesscalendar"processcalendar" conditional on the sender being trustworthy.</li> </ul> <t>Additionally, if the calendar data has embedded (a.k.a. inline) attachments, implementationsSHOULD:</t><bcp14>SHOULD</bcp14>:</t> <ul> <li>Decode the embedded attachment, if necessary.</li> <li>Scan the (decoded) attachment for malicious content.</li> </ul> <t>If an attachment is found to be malicious,processcalendar MUST NOT"processcalendar" <bcp14>MUST NOT</bcp14> process the calendar data.</t> </section> <section anchor="privacy" numbered="true" toc="default"> <name>Privacy Considerations</name> <t>It is believed that this extension doesn't introduce any privacy considerations beyond those in <xref target="RFC5228" format="default"/>.</t> </section> <section numbered="true" toc="default"> <name>IANA Considerations</name> <section numbered="true" toc="default"> <name>Registration of Sieve Extension</name> <t>This document defines the following new Sieveextension to beextension, which IANA has added to the <eref target="https://www.iana.org/assignments/sieve-extensions">"Sieve Extensions" registry</eref>. The registry is defined inSection 6.2 of<xref target="RFC5228"format="default"/> and located here: <eref target="https://www.iana.org/assignments/sieve-extensions/sieve-extensions.xhtml#sieve-extensions"/> </t> <t>IANA are requested to add a capability to the Sieve Extensions registry:format="default" sectionFormat="of" section="6.2"/>. </t><ul empty="true"<dl newline="false" spacing="normal"><li>To: iana@iana.org</li> <li>Subject: Registration of new Sieve extension</li> <li>Capability name: processcalendar</li> <li>Description: Adds<dt>Capability name:</dt><dd>processcalendar</dd> <dt>Description:</dt><dd>Adds the "processcalendar" action command to add and update items on a user'scalendars.</li> <li>RFC number: RFC XXXX</li> <li>Contact address: The Sievecalendars.</dd> <dt>RFC number:</dt><dd>RFC 9671</dd> <dt>Contact address:</dt><dd>Sieve discussion list<sieve@ietf.org></li> </ul><sieve@ietf.org></dd> </dl> </section> <section numbered="true" toc="default"> <name>Registration of Sieve Action</name> <t>This document defines the following new Sieveaction to beaction, which IANA has added to the <eref target="https://www.iana.org/assignments/sieve-extensions">"Sieve Actions" registry </eref>. The registry is defined inSection 2.1 of<xref target="RFC9122"format="default"/> and located here: <eref target="https://www.iana.org/assignments/sieve-extensions/sieve-extensions.xhtml#sieve-actions"/> </t> <t>IANA are requested to add a capability to the Sieve Actions registry:format="default" sectionFormat="of" section="2.1"/>. </t><ul empty="true"<dl newline="false" spacing="normal"><li>To: iana@iana.org</li> <li>Subject: Registration of new Sieve action</li> <li>Name: processcalendar</li> <li>Description: Add<dt>Name:</dt><dd>processcalendar</dd> <dt>Description:</dt><dd>Add and update items on a user'scalendars</li> <li>References: RFC XXXXcalendars</dd> <dt>References:</dt><dd>RFC 9671 <xref target="RFC5229"/> <xreftarget="RFC6134"/></li> <li>Capabilities: "processcalendar",target="RFC6134"/></dd> <dt>Capabilities:</dt><dd>"processcalendar", "variables","extlists"</li> <li>Action Interactions: This"extlists"</dd> <dt>Action Interactions:</dt><dd>This action is incompatible with the "reject" and "ereject"actions</li> <li>Cancelsactions.</dd> <dt>Cancels ImplicitKeep? No</li> <li>CanKeep?</dt><dd>No</dd> <dt>Can Use with IMAPEvents? No</li> </ul>Events?</dt><dd>No</dd> </dl> </section> </section><!-- IANA --> <section numbered="true" toc="default"> <name>Acknowledgments</name> <t>The authors would like to thank the following individuals for contributing their ideas and support for writing this specification: Ned Freed and Alexey Melnikov.</t> </section></middle> <back> <references> <name>References</name> <references> <name>Normative References</name> <xi:includehref="https://xml2rfc.ietf.org/public/rfc/bibxml/reference.RFC.2119.xml"/>href="https://bib.ietf.org/public/rfc/bibxml/reference.RFC.2119.xml"/> <xi:includehref="https://xml2rfc.ietf.org/public/rfc/bibxml/reference.RFC.5228.xml"/>href="https://bib.ietf.org/public/rfc/bibxml/reference.RFC.5228.xml"/> <xi:includehref="https://xml2rfc.ietf.org/public/rfc/bibxml/reference.RFC.5229.xml"/>href="https://bib.ietf.org/public/rfc/bibxml/reference.RFC.5229.xml"/> <xi:includehref="https://xml2rfc.ietf.org/public/rfc/bibxml/reference.RFC.8174.xml"/>href="https://bib.ietf.org/public/rfc/bibxml/reference.RFC.8174.xml"/> <xi:includehref="https://xml2rfc.ietf.org/public/rfc/bibxml/reference.RFC.6047.xml"/>href="https://bib.ietf.org/public/rfc/bibxml/reference.RFC.6047.xml"/> <xi:includehref="https://xml2rfc.ietf.org/public/rfc/bibxml/reference.RFC.6134.xml"/>href="https://bib.ietf.org/public/rfc/bibxml/reference.RFC.6134.xml"/> <xi:includehref="https://xml2rfc.ietf.org/public/rfc/bibxml/reference.RFC.9122.xml"/>href="https://bib.ietf.org/public/rfc/bibxml/reference.RFC.9122.xml"/> <reference anchor="CALSPAM" target="https://standards.calconnect.org/csd/cc-18003.html"> <front> <title>Calendar operator practices - Guidelines to protect against calendar abuse</title> <author> <organization>The Calendaring and Scheduling Consortium</organization> </author> <date year="2019"/> </front> <seriesInfo name="CC/R"value="18003"/>value="18003:2019"/> </reference> </references> <references> <name>Informative References</name> <xi:includehref="https://xml2rfc.ietf.org/public/rfc/bibxml/reference.RFC.2045.xml"/>href="https://bib.ietf.org/public/rfc/bibxml/reference.RFC.2045.xml"/> <xi:includehref="https://xml2rfc.ietf.org/public/rfc/bibxml/reference.RFC.5545.xml"/>href="https://bib.ietf.org/public/rfc/bibxml/reference.RFC.5545.xml"/> <xi:includehref="https://xml2rfc.ietf.org/public/rfc/bibxml/reference.RFC.5235.xml"/>href="https://bib.ietf.org/public/rfc/bibxml/reference.RFC.5235.xml"/> <xi:includehref="https://xml2rfc.ietf.org/public/rfc/bibxml/reference.RFC.5546.xml"/>href="https://bib.ietf.org/public/rfc/bibxml/reference.RFC.5546.xml"/> <xi:includehref="https://xml2rfc.ietf.org/public/rfc/bibxml/reference.RFC.5429.xml"/>href="https://bib.ietf.org/public/rfc/bibxml/reference.RFC.5429.xml"/> <xi:includehref="https://xml2rfc.ietf.org/public/rfc/bibxml/reference.RFC.8984.xml"/>href="https://bib.ietf.org/public/rfc/bibxml/reference.RFC.8984.xml"/> <xi:includehref="https://xml2rfc.ietf.org/public/rfc/bibxml/reference.RFC.8551.xml"/>href="https://bib.ietf.org/public/rfc/bibxml/reference.RFC.8551.xml"/> <xi:includehref="https://xml2rfc.ietf.org/public/rfc/bibxml/reference.RFC.6376.xml"/>href="https://bib.ietf.org/public/rfc/bibxml/reference.RFC.6376.xml"/> <xi:includehref="https://xml2rfc.ietf.org/public/rfc/bibxml/reference.RFC.7489.xml"/>href="https://bib.ietf.org/public/rfc/bibxml/reference.RFC.7489.xml"/> <xi:includehref="https://xml2rfc.ietf.org/public/rfc/bibxml/reference.RFC.7208.xml"/> <!-- <xi:include href="https://datatracker.ietf.org/doc/bibxml3/draft-ietf-calext-jscalendarbis.xml"/>-->href="https://bib.ietf.org/public/rfc/bibxml/reference.RFC.7208.xml"/> </references> </references> <sectiontitle="Change History (To be removed by RFC Editor before publication)"> <t>Changes since draft-ietf-sieve-processimip-08:</t> <ol> <li>Added a consequence of not removing alarms before applying datanumbered="false" toc="default"> <name>Acknowledgments</name> <t>The authors would like toa calendar.</li> <li>Changed iCalendar-specific "UID" to generic "unique identifier".</li> <li>Use a normative SHOULDthank the following individuals for:deletecancelled argument.</li> <li>Removed Implementation Status section.</li> </ol> <t>Changes since draft-ietf-sieve-processimip-07:</t> <ol> <li>Fixed Sieve Action registration to include all associated capabilites andcontributing theirreferences.</li> </ol> <t>Changes since draft-ietf-sieve-processimip-06:</t> <ol> <li>Fixed example that was still using :errstr rather than :reason.</li> <li>Explicitly stated that the :updateonly and :calendarid options are incompatible with each each.</li> <li>Explicitly stated that if :allowpublic is used with :organizers that non-iTIP messages MUST NOT be processed.</li> <li>Updated security considerations to use "deny list" and "allow list", and to add a bullet discussing use of S/MIME, SPF, DKIM, and DMARC.</li> <li>Updated the status of the Cyrus implementation.</li> <li>Miscellaneous editorial changes.</li> </ol> <t>Changes since draft-ietf-sieve-processimip-05:</t> <ol> <li>Renamed :errstr to :reason and added examples.</li> <li>Miscellaneous editorial changes.</li> </ol> <t>Changes since draft-ietf-sieve-processimip-04:</t> <ol> <li>Miscellaneous editorial changes.</li> </ol> <t>Changes since draft-ietf-sieve-processimip-03:</t> <ol> <li>Added text about multiple MIME parts containing calendar data.</li> <li>Added text about embedded attachments to Security Considerations.</li> <li>Added :organizers option if "extlists" is supported.</li> <li>Miscellaneous editorial changes.</li> </ol> <t>Changes since draft-ietf-sieve-processimip-02:</t> <ol> <li>Renamed :nonitip to :allowpublic to cover both non-iTIPideas andMETHOD:PUBLIC messages.</li> <li>Renamed :deletecanceled to :deletecancelled to match RFC5545 language.</li> <li>Specified that this action MUST NOT alter a recipient's participation status.</li> <li>:errstr MUST be set to the empty string if no reason for the outcome is available.</li> <li>Added the "Interaction with Other Sieve Actions" subsection.</li> <li>Add Security Considerations.</li> <li>Added action registration.</li> <li>Added three issuessupport fordiscussion.</li> <li>Miscellaneous editorial changes.</li> </ol> <t>Changes since draft-ietf-sieve-processimip-01:</t> <ol> <li>Changed the name of the action from processimip to processcalendar.</li> <li>The action is now independent of iMIP and is calendar data format agnostic.</li> <li>Added examples.</li> </ol> <t>Changes since draft-ietf-sieve-processimip-00:</t> <ol> <li>No changes.</li> </ol> <t>Changes since draft-murchison-sieve-processimip-00:</t> <ol> <li>Document name change only.</li> </ol>writing this specification: <contact fullname="Ned Freed"/> and <contact fullname="Alexey Melnikov"/>.</t> </section> </back> </rfc>