INTERNET-DRAFT A. Melnikov Document: draft-ietf-calsify-rfc2447bis-05.txt Editor Intended status: Standard Track June 9, 2008 Expires: December 2008 iCalendar Message-Based Interoperability Protocol (iMIP) Status of this Memo By submitting this Internet-Draft, each author represents that any applicable patent or other IPR claims of which he or she is aware have been or will be disclosed, and any of which he or she becomes aware will be disclosed, in accordance with Section 6 of BCP 79. Internet-Drafts are working documents of the Internet Engineering Task Force (IETF), its areas, and its working groups. Note that other groups may also distribute working documents as Internet-Drafts. Internet-Drafts are draft documents valid for a maximum of six months and may be updated, replaced, or obsoleted by other documents at any time. It is inappropriate to use Internet-Drafts as reference material or to cite them other than as "work in progress." The list of current Internet-Drafts can be accessed at http://www.ietf.org/1id-abstracts.html The list of Internet-Draft Shadow Directories can be accessed at http://www.ietf.org/shadow.html A revised version of this draft document will be submitted to the RFC editor as a Draft Standard for the Internet Community. Discussion and suggestions for improvement are requested, and should be sent to the CALSIFY Mailing list <ietf-calsify@osafoundation.org>. Distribution of this document is unlimited. Copyright Notice Copyright (C) The IETF Trust (2008). Abstract This document, iCalendar Message-Based Interoperability Protocol (iMIP), specifies a binding from the iCalendar Transport-independent Interoperability Protocol (iTIP) to Internet email-based transports. Melnikov (Ed.) Standards Track FORMFEED[Page 1]
RFC 2447bis iMIP June 2008 Calendaring entries defined by the iCalendar Object Model (iCAL) are composed using constructs from RFC 2822, RFC 2045, RFC 2046, RFC 2047 and RFC 2049. This document is a product of Calendaring and Scheduling Standards Simplification (calsify) working group. More information about the IETF CALSIFY working group activities can be found on the IETF web site at <http://www.ietf.org/html.charters/calsify-charter.html>. The issue tracker for the Calsify WG is located at: <http://www.ofcourseimright.com/cgi-bin/roundup/calsify> Melnikov (Ed.) Standards Track FORMFEED[Page 2]
RFC 2447bis iMIP June 2008 Table of Contents 1 INTRODUCTION........................................................2 1.1 RELATED MEMOS ...................................................2 1.2 FORMATTING CONVENTIONS ..........................................3 1.3 TERMINOLOGY .....................................................4 2 MIME MESSAGE FORMAT BINDING.........................................4 2.1 MIME MEDIA TYPE .................................................4 2.2 SECURITY ........................................................4 2.2.1 Authorization ...............................................4 2.2.2 Authentication ..............................................5 2.2.3 Confidentiality .............................................5 2.3 [RFC-2822] ADDRESSES ............................................5 2.4 CONTENT TYPE ....................................................5 2.5 CONTENT-TRANSFER-ENCODING .......................................6 2.6 CONTENT-DISPOSITION .............................................6 3 SECURITY CONSIDERATIONS.............................................7 4 EXAMPLES............................................................8 4.1 SINGLE COMPONENT WITH AN ATTACH PROPERTY ........................8 4.2 USING MULTIPART ALTERNATIVE FOR LOW FIDELITY CLIENTS ............8 4.3 SINGLE COMPONENT WITH AN ATTACH PROPERTY AND INLINE ATTACHMENT ..9 4.4 MULTIPLE SIMILAR COMPONENTS ....................................10 4.5 MULTIPLE MIXED COMPONENTS ......................................11 4.6 DETAILED COMPONENTS WITH AN ATTACH PROPERTY ....................13 5 RECOMMENDED PRACTICES..............................................14 5.1 USE OF CONTENT AND MESSAGE IDS .................................14 6 REFERENCES.........................................................15 7 EDITOR'S ADDRESSES.................................................16 8 FULL COPYRIGHT STATEMENT...........................................XX 9 INTELLECTUAL PROPERTY..............................................XX 1 Introduction This binding document provides the transport specific information necessary to convey iCalendar Transport-independent Interoperability Protocol (iTIP) [iTIP] over MIME as defined in [RFC-2822] and [RFC-2045]. 1.1 Related Memos Implementers will need to be familiar with several other memos that, along with this memo, form a framework for Internet calendaring and scheduling standards. This document, [iMIP], specifies an Internet email binding for iTIP. [iCAL] - specifies a core specification of objects, data types, properties and property parameters; Melnikov (Ed.) Standards Track FORMFEED[Page 3]
RFC 2447bis iMIP June 2008 [iTIP] - specifies an interoperability protocol for scheduling between different implementations; This memo does not attempt to repeat the specification of concepts or definitions from these other memos. Where possible, references are made to the memo that provides for the specification of these concepts or definitions. 1.2 Formatting Conventions The mechanisms defined in this memo are defined in prose. In order to refer to elements of the calendaring and scheduling model, core object or interoperability protocol defined in [iCAL] and [iTIP] some formatting conventions have been used. The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this document are to be interpreted as described in RFC 2119 [RFC-2119]. Calendaring and scheduling roles are referred to in quoted-strings of text with the first character of each word in upper case. For example, "Organizer" refers to a role of a "Calendar User" within the scheduling protocol defined by [iTIP]. Calendar components defined by [iCAL] are referred to with capitalized, quoted-strings of text. All calendar components start with the letter "V". For example, "VEVENT" refers to the event calendar component, "VTODO" refers to the to-do calendar component and "VJOURNAL" refers to the daily journal calendar component. Scheduling methods defined by [iTIP] are referred to with capitalized, quoted-strings of text. For example, "REQUEST" refers to the method for requesting a scheduling calendar component be created or modified, "REPLY" refers to the method a recipient of a request uses to update their status with the "Organizer" of the calendar component. Properties defined by [iCAL] are referred to with capitalized, quoted-strings of text, followed by the word "property". For example, "ATTENDEE" property refers to the iCalendar property used to convey the calendar address of a calendar user. Property parameters defined by [iCAL] are referred to with lower case, quoted-strings of text, followed by the word "parameter". For example, "value" parameter refers to the iCalendar property parameter used to override the default data type for a property value. Melnikov (Ed.) Standards Track FORMFEED[Page 4]
RFC 2447bis iMIP June 2008 1.3 Terminology The email terms used in this memo are defined in [RFC-2822] and [RFC-2045]. The calendaring and scheduling terms used in this memo are defined in [iCAL] and [iTIP]. 2 MIME Message Format Binding This section defines the message binding to the MIME electronic mail transport. The sections below refer to the "originator" and the "respondent" of an iMIP message. Typically, the originator is the "Organizer" of an event. The respondent is an "Attendee" of the event. The [RFC-2822] "Reply-To" header typically contains the email address of the originator or respondent of an event. However, this cannot be guaranteed as Mail User Agents (MUA) are not required to enforce iMIP semantics. 2.1 MIME Media Type A MIME entity containing content information formatted according to this document will be referenced as a "text/calendar" content type. It is assumed that this content type will be transported through a MIME electronic mail transport. 2.2 Security This section addresses several aspects of security including Authentication, Authorization and Confidentiality. Authentication and confidentiality can be achieved using [RFC-1847] that specifies the Security Multiparts for MIME. This framework defines new content types and subtypes of multipart: signed and encrypted. Each contains two body parts: one for the protected data and another for the control information necessary to remove the protection. 2.2.1 Authorization In [iTIP] messages, only the "Organizer" is authorized to modify or cancel calendar entries they organize. That is, spoof@xyz.example.net is not allowed to modify or cancel a meeting that was organized by a@example.com. Furthermore, only the respondent has the authorization to indicate their status to the "Organizer". That is, the "Organizer" must ignore an [iTIP] message from spoof@xyz.example.net that declines a meeting invitation for b@example.com. Melnikov (Ed.) Standards Track FORMFEED[Page 5]
RFC 2447bis iMIP June 2008 Implementations of iMIP SHOULD verify the authenticity of the creator of an iCalendar object before taking any action. The methods for doing this are presented later in this document. [RFC-1847] Message flow in iTIP supports someone working on behalf of a "Calendar User" through use of the "sent-by" parameter that is associated with the "ATTENDEE" and "ORGANIZER" properties. However, there is no mechanism to verify whether or not a "Calendar User" has authorized someone to work on their behalf. It is left to implementations to provide mechanisms for the "Calendar Users" to make that decision. 2.2.2 Authentication Authentication can be performed using an implementation of [RFC-1847] "multipart/signed" that supports public/private key certificates. Authentication is possible only on messages that have been signed. Authenticating an unsigned message may not be reliable. 2.2.3 Confidentiality To ensure confidentiality using iMIP implementations should utilize encryption compliant with [RFC-1847]. The protocol does not restrict a "Calendar User Agent" (CUA) from forwarding iCalendar objects to other users or agents. 2.3 [RFC-2822] Addresses The calendar address specified within the "ATTENDEE" property in an iCalendar object MUST be a fully qualified, [RFC-2822] address specification for the corresponding "Organizer" or "Attendee" of the "VEVENT" or "VTODO". Because [iTIP] does not preclude "Attendees" from forwarding "VEVENTS" or "VTODOS" to others, the [RFC-2822] "Sender" value may not equal that of the "Organizer". Additionally, the "Organizer" or "Attendee" cannot be reliably inferred by the [RFC-2822] "Sender" or "Reply-to" values of an iMIP message. The relevant address MUST be ascertained by opening the "text/calendar" MIME body part and examining the "ATTENDEE" and "ORGANIZER" properties. 2.4 Content Type A MIME body part containing content information that conforms to this document MUST have an [RFC-2045] "Content-Type" value of "text/calendar". The [RFC-2045] "Content-Type" header field MUST also include the type parameter "method". The value MUST be the same as the value of the "METHOD" calendar property within the iCalendar Melnikov (Ed.) Standards Track FORMFEED[Page 6]
RFC 2447bis iMIP June 2008 object. Note 1: A MIME message containing multiple iCalendar objects with different method values must be further encapsulated with a "multipart/mixed" MIME entity. This will allow each of the iCalendar objects to be encapsulated within their own "text/calendar" MIME entity. Note 2: A MIME body part of "text/calendar" "Content-Type" that lacks the "method" parameter is not considered to be an iMIP body part and thus is not subject to the requirements specified in this document. Note that according to [iCAL] the default character set for iCalendar objects is UTF-8 [UTF-8]. However the default character set for a "text/*" MIME entity according to [RFC-2046] is US-ASCII. Thus a "charset" parameter MUST be present if the iCalendar object contains characters that can't be represented in US-ASCII character set. [RFC-2046] discusses the selection of an appropriate "charset" value. The optional "component" parameter defines the iCalendar component type contained within the iCalendar object. The following is an example of this header field with a value that indicates an event message. Content-Type: text/calendar; method=request; charset=UTF-8; component=vevent The "text/calendar" content type allows for the scheduling message type to be included in a MIME message with other content information (i.e., "multipart/mixed") or included in a MIME message with a clear- text, human-readable form of the scheduling message (i.e., "multipart/alternative"). In order to permit the information in the scheduling message to be understood by MIME user agents (UA) that do not support the "text/calendar" content type, scheduling messages SHOULD be sent with an alternative, human-readable form of the information. Note that "multiple/alternative" MUST NOT be used to represent two slightly different iCalendar objects, for example two VEVENT with alternative starting times. CUA can use language and other parameters to pick a "text/calendar" part if a "multipart/alternative" MIME message contains more than one "text/calendar" part. Any receiving UA compliant with this specification MUST be able to Melnikov (Ed.) Standards Track FORMFEED[Page 7]
RFC 2447bis iMIP June 2008 process "text/calendar" body parts enclosed within "multipart/*". Note that a "multipart/mixed" MIME message can include multiple "text/calendar" components. The receiving UA MUST be able to process all of them. 2.5 Content-Transfer-Encoding Unless iMIP message is transported over 8-bit clean transport (such as SMTP [8BITMIME]), a transfer encoding such as quoted-printable or base64 [RFC-2045] MUST be used for iCalendar objects containing any characters that can't be represented in the US-ASCII character set. For example: From: user1@example.com To: user2@example.com Subject: Phone Conference Mime-Version: 1.0 Date: Wed, 07 May 2008 21:30:25 +0400 Message-ID: <4821E731.5040506@laptop1.example.com> Content-Type: text/calendar; method=REQUEST; charset=UTF-8 Content-Transfer- Encoding: quoted-printable BEGIN:VCALENDAR PRODID:-//ACME/DesktopCalendar//EN METHOD:REQUEST VERSION:2.0 BEGIN:VEVENT ORGANIZER:mailto:user1@example.com ATTENDEE;ROLE=CHAIR;ATTSTAT=ACCEPTED:mailto:user1@example.com ATTENDEE;RSVP=YES;CUTYPE=INDIVIDUAL:mailto:user2@example.com DTSTAMP:20080507T170000Z DTSTART:20080701T160000Z DTEND:20080701T163000Z SUMMARY:Phone call to discuss your last visit DESCRIPTION:=D1=82=D1=8B =D0=BA=D0=B0=D0=BA - =D0=B4=D0=BE=D0= =B2=D0=BE=D0=BB=D0=B5=D0=BD =D0=BF=D0=BE=D0=B5=D0=B7=D0=B4=D0=BA=D0=BE=D0= =B9? UID:calsvr.example.com-8739701987387998 SEQUENCE:0 STATUS:TENTATIVE END:VEVENT END:VCALENDAR 2.6 Content-Disposition Implementations MAY include a "Content-Disposition" header field to define a file name for an iCalendar object. However, the handling of a MIME part MUST be based on its [RFC-2045] "Content-Type" and not on the extension specified in the "Content-Disposition", as different email malware is known to trick User Agents into misinterpreting content of messages by specifying a file extension in the Content- Disposition header field that doesn't correspond to the value of Content-Type header field. Melnikov (Ed.) Standards Track FORMFEED[Page 8]
RFC 2447bis iMIP June 2008 3 Security Considerations The security threats that applications must address when implementing iTIP are detailed in [iTIP]. In particular two spoofing threats are identified in [iTIP]: Spoofing the "Organizer", and Spoofing an "Attendee". To address these threats, the originator of an iCalendar object must be authenticated by a recipient. Once authenticated, a determination can be made as to whether or not the originator is authorized to perform the requested operation. Compliant applications MUST support signing and encrypting text/calendar body parts using a mechanism based on Security Multiparts for MIME [RFC-1847] to facilitate the authentication of the originator of the iCalendar object. The steps for processing a signed iMIP message are described below: 1. The iCalendar object MUST be signed by the "Organizer" sending an update/initial request or the "Attendee" sending a reply. <<Or the person sending on their behalf? Clearly if somebody else is sending the invitation, she can't sign using the key belonging to the organizer>> 2. Using the security mechanism compliant with [RFC-1847], determine who signed the iCalendar object. This is the "signer". Note that the signer is not necessarily the person sending an e-mail message since an e-mail message can be forwarded. 3. Correlate the signer to either an "ATTENDEE" property or to the "ORGANIZER" property in the iCalendar object, based on the method and the calendar component specified in the iCalendar object, as defined in Section 3 of [iTIP]. If the signer cannot be correlated to an "ATTENDEE"/"ORGANIZER" property (or is not authorized to act on her behalf), ignore the message. 4. Determine whether or not the "ATTENDEE"/"ORGANIZER" is authorized to perform the operation as defined by [iTIP]. If the conditions are not met, ignore the message. 5. If all the above conditions are met, the message can be processed. [RFC-1847] signing also protects against malicious changes in transit. If calendar confidentiality is required by the sender, signed iMIP messages SHOULD be encrypted by a mechanism based on Security Multiparts for MIME [RFC-1847]. Once a signed and/or encrypted iMIP message is received and successfully verified (as detailed above) by a CUA, the CUA SHOULD Melnikov (Ed.) Standards Track FORMFEED[Page 9]
RFC 2447bis iMIP June 2008 remember whether the sender of the message is using signing and/or encrypting. If an unsigned iMIP message is received from the same sender later on, the receiving CUA SHOULD warn the user about a possible man-in-the-middle attack and SHOULD ignore the message, unless explicitly overriden by the user. <<Should it also try to notify the other end?>> Implementations MAY provide means for users to disable signing and encrypting. It is possible to receive iMIP messages sent by someone working on behalf of another "Calendar User". This is determined by examining the "sent-by" parameter in the relevant "ORGANIZER" or "ATTENDEE" property. [iCAL] and [iTIP] provide no mechanism to verify that a "Calendar User" has authorized someone else to work on their behalf. To address this security issue, implementations MUST provide mechanisms for the "Calendar Users" to make that decision before applying changes from someone working on behalf of a "Calendar User". One way to achieve this is to reject iMIP messages sent by users other than the "ORGANIZER" or the "ATTENDEE"s. A security consideration associated with use of Content-Disposition header field is described in section 2.6. Melnikov (Ed.) Standards Track FORMFEED[Page 10]
RFC 2447bis iMIP June 2008 4 Examples 4.1 Single Component With An ATTACH Property This minimal message shows how an iCalendar object references an attachment. The attachment is accessible via its URL. From: sman@netscape.example.com To: stevesil@microsoft.example.com Subject: Phone Conference Mime-Version: 1.0 Content-Type: text/calendar; method=REQUEST; charset=US-ASCII Content-Transfer-Encoding: 7bit BEGIN:VCALENDAR PRODID:-//ACME/DesktopCalendar//EN METHOD:REQUEST VERSION:2.0 BEGIN:VEVENT ORGANIZER:mailto:sman@netscape.example.com ATTENDEE;ROLE=CHAIR;ATTSTAT=ACCEPTED:mailto:sman@netscape.example.com ATTENDEE;RSVP=YES:mailto:stevesil@microsoft.example.com DTSTAMP:19970611T190000Z DTSTART:19970701T210000Z DTEND:19970701T230000Z SUMMARY:Phone Conference DESCRIPTION:Please review the attached document. UID:calsvr.example.com-873970198738777 ATTACH:ftp://ftp.bar.example.com/pub/docs/foo.doc STATUS:CONFIRMED END:VEVENT END:VCALENDAR 4.2 Using Multipart Alternative for Low Fidelity Clients This example shows how a client can emit a multipart message that includes both a plain text version as well as the full iCalendar object. Clients that do not support text/calendar will still be capable of rendering the plain text representation. From: foo1@example.com To: foo2@example.com Subject: Phone Conference Mime-Version: 1.0 Content-Type: multipart/alternative;boundary="01BD3665.3AF0D360" --01BD3665.3AF0D360 Content-Type: text/plain;charset=us-ascii Melnikov (Ed.) Standards Track FORMFEED[Page 11]
RFC 2447bis iMIP June 2008 Content-Transfer-Encoding: 7bit This is an alternative representation of a TEXT/CALENDAR MIME Object When: 7/1/1997 10:00AM PDT - 7/1/97 10:30AM PDT Where: Organizer: foo1@example.com Summary: Phone Conference --01BD3665.3AF0D360 Content-Type: text/calendar; method=REQUEST; charset=US-ASCII Content-Transfer-Encoding: 7bit BEGIN:VCALENDAR PRODID:-//ACME/DesktopCalendar//EN METHOD:REQUEST VERSION:2.0 BEGIN:VEVENT ORGANIZER:mailto:foo1@example.com ATTENDEE;ROLE=CHAIR;ATTSTAT=ACCEPTED:mailto:foo1@example.com ATTENDEE;RSVP=YES;CUTYPE=INDIVIDUAL:mailto:foo2@example.com DTSTAMP:19970611T190000Z DTSTART:19970701T170000Z DTEND:19970701T173000Z SUMMARY:Phone Conference UID:calsvr.example.com-8739701987387771 SEQUENCE:0 STATUS:CONFIRMED END:VEVENT END:VCALENDAR --01BD3665.3AF0D360 4.3 Single Component With An ATTACH Property and Inline Attachment This example shows how a message containing an iCalendar object references an attached document. The reference is made using a Content-id (CID). Thus, the iCalendar object and the document are packaged in a multipart/related encapsulation. From: foo1@example.com To: foo2@example.com Subject: Phone Conference Mime-Version: 1.0 Content-Type: multipart/related; boundary="boundary-example-1" --boundary-example-1 Content-Type: text/calendar; method=REQUEST; charset=US-ASCII Melnikov (Ed.) Standards Track FORMFEED[Page 12]
RFC 2447bis iMIP June 2008 Content-Transfer-Encoding: 7bit Content-Disposition: attachment; filename="event.vcs" BEGIN:VCALENDAR PRODID:-//ACME/DesktopCalendar//EN METHOD:REQUEST VERSION:2.0 BEGIN:VEVENT ORGANIZER:mailto:foo1@example.com ATTENDEE;ROLE=CHAIR;ATTSTAT=ACCEPTED:mailto:foo1@example.com ATTENDEE;RSVP=YES;CUTYPE=INDIVIDUAL:mailto:foo2@example.com DTSTAMP:19970611T190000Z DTSTART:19970701T180000Z DTEND:19970701T183000Z SUMMARY:Phone Conference UID:calsvr.example.com-8739701987387771 ATTACH:cid:123456789@example.com SEQUENCE:0 STATUS:CONFIRMED END:VEVENT END:VCALENDAR --boundary-example-1 Content-Type: application/msword; name="FieldReport.doc" Content-Transfer-Encoding: base64 Content-Disposition: inline; filename="FieldReport.doc" Content-ID: <123456789@example.com> 0M8R4KGxGuEAAAAAAAAAAAAAAAAAAAAAPgADAP7/CQAGAAAAAAAAAAABAAAARAAAAAAA AAAAEAAAQAAAAAEAAAD+////AAAAAEUAAAD///////////////////////////////// ... --boundary-example-1-- 4.4 Multiple Similar Components Multiple iCalendar components of the same type can be included in the iCalendar object when the METHOD is the same for each component. From: foo1@example.com To: foo2@example.com Subject: Summer Company Holidays Mime-Version: 1.0 Content-Type: text/calendar; method=PUBLISH; charset=US-ASCII Content-Transfer-Encoding: 7bit Content-Disposition: attachment; filename="event.vcs" Melnikov (Ed.) Standards Track FORMFEED[Page 13]
RFC 2447bis iMIP June 2008 BEGIN:VCALENDAR PRODID:-//ACME/DESKTOPCALENDAR//EN METHOD:PUBLISH VERSION:2.0 BEGIN:VEVENT ORGANIZER:MAILTO:FOO1@EXAMPLE.COM DTSTAMP:19970611T150000Z DTSTART:19970701T150000Z DTEND:19970701T230000Z SUMMARY:Company Picnic DESCRIPTION:Food and drink will be provided UID:CALSVR.EXAMPLE.COM-873970198738777-1 SEQUENCE:0 STATUS:CONFIRMED END:VEVENT BEGIN:VEVENT ORGANIZER:MAILTO:FOO1@EXAMPLE.COM DTSTAMP:19970611T190000Z DTSTART:19970715T150000Z DTEND:19970715T230000Z SUMMARY:Company Bowling Tournament DESCRIPTION:We have 10 lanes reserved UID:CALSVR.EXAMPLE.COM-873970198738777-2 SEQUENCE:0 STATUS:CONFIRMED END:VEVENT END:VCALENDAR 4.5 Multiple Mixed Components Different component types must be encapsulated in separate iCalendar objects. From: foo1@example.com To: foo2@example.com Subject: Phone Conference Mime-Version: 1.0 Content-Type: multipart/mixed;boundary="--FEE3790DC7E35189CA67CE2C" This is a multi-part message in MIME format. ----FEE3790DC7E35189CA67CE2C Content-Type: text/calendar; method=REQUEST; charset=US-ASCII Content-Transfer-Encoding: 7bit Content-Disposition: attachment; filename="event1.vcs" Melnikov (Ed.) Standards Track FORMFEED[Page 14]
RFC 2447bis iMIP June 2008 BEGIN:VCALENDAR PRODID:-//ACME/DesktopCalendar//EN METHOD:REQUEST VERSION:2.0 BEGIN:VEVENT ORGANIZER:mailto:foo1@example.com ATTENDEE;ROLE=CHAIR;ATTSTAT=ACCEPTED:mailto:foo1@example.com ATTENDEE;RSVP=YES;CUTYPE=INDIVIDUAL:mailto:foo2@example.com DTSTAMP:19970611T190000Z DTSTART:19970701T210000Z DTEND:19970701T230000Z SUMMARY:Phone Conference DESCRIPTION:Discuss what happened at the last meeting UID:calsvr.example.com-8739701987387772 SEQUENCE:0 STATUS:CONFIRMED END:VEVENT END:VCALENDAR ----FEE3790DC7E35189CA67CE2C Content-Type: text/calendar; method=REQUEST; charset=US-ASCII Content-Transfer-Encoding: 7bit Content-Disposition: attachment; filename="todo1.vcs" BEGIN:VCALENDAR PRODID:-//ACME/DesktopCalendar//EN METHOD:REQUEST VERSION:2.0 BEGIN:VTODO DUE:19970701T090000-0700 ORGANIZER:mailto:foo1@example.com ATTENDEE;ROLE=CHAIR;ATTSTAT=ACCEPTED:mailto:foo1@example.com ATTENDEE;RSVP=YES:mailto:foo2@example.com SUMMARY:Phone Conference DESCRIPTION:Discuss a new location for the company picnic UID:calsvr.example.com-td-8739701987387773 SEQUENCE:0 STATUS:NEEDS ACTION END:VEVENT END:VCALENDAR ----FEE3790DC7E35189CA67CE2C Melnikov (Ed.) Standards Track FORMFEED[Page 15]
RFC 2447bis iMIP June 2008 4.6 Detailed Components With An ATTACH Property This example shows the format of a message containing a group meeting between three individuals. The multipart/related encapsulation is used because the iCalendar object contains an ATTACH property that uses a CID to reference the attachment. From: foo1@example.com MIME-Version: 1.0 To: foo2@example.com,foo3@example.com Subject: REQUEST - Phone Conference Content-Type: multipart/related;boundary="--FEE3790DC7E35189CA67CE2C" ----FEE3790DC7E35189CA67CE2C Content-Type: multipart/alternative; boundary="--00FEE3790DC7E35189CA67CE2C00" ----00FEE3790DC7E35189CA67CE2C00 Content-Type: text/plain; charset=us-ascii Content-Transfer-Encoding: 7bit When: 7/1/1997 10:00PM PDT- 7/1/97 10:30 PM PDT Where: Organizer: foo1@example.com Summary: Let's discuss the attached document ----00FEE3790DC7E35189CA67CE2C00 Content-Type: text/calendar; method=REQUEST; charset=US-ASCII; Component=vevent Content-Transfer-Encoding: 7bit Content-Disposition: attachment; filename="event.vcs" BEGIN:VCALENDAR PRODID:-//ACME/DesktopCalendar//EN PROFILE:REQUEST PROFILE-VERSION:1.0 VERSION:2.0 BEGIN:VEVENT ORGANIZER:foo1@example.com ATTENDEE;ROLE=CHAIR;ATTSTAT=ACCEPTED:foo1@example.com ATTENDEE;RSVP=YES;CUTYPE=INDIVIDUAL:mailto:foo2@example.com ATTENDEE;RSVP=YES;CUTYPE=INDIVIDUAL:mailto:foo3@example.com DTSTAMP:19970611T190000Z DTSTART:19970621T170000Z DTEND:199706211T173000Z SUMMARY:Let's discuss the attached document UID:calsvr.example.com-873970198738777-8aa Melnikov (Ed.) Standards Track FORMFEED[Page 16]
RFC 2447bis iMIP June 2008 ATTACH:cid:calsvr.example.com-12345aaa SEQUENCE:0 STATUS:CONFIRMED END:VEVENT END:VCALENDAR ----00FEE3790DC7E35189CA67CE2C00 ----FEE3790DC7E35189CA67CE2C Content-Type: application/msword; name="FieldReport.doc" Content-Transfer-Encoding: base64 Content-Disposition: inline; filename="FieldReport.doc" Content-ID: <calsvr.example.com-12345aaa> R0lGODdhTAQZAJEAAFVVVd3d3e4AAP///ywAAAAATAQZAAAC/5yPOSLhD6OctNqLs94Xq AG4kiW5omm6sq27gvH8kzX9o1y+s73/g8MCofEovGITCoxKMbyCR16cNSq9YrNarfcrvd riIH5LL5jE6rxc3G+v2cguf0uv2Oz+v38L7/DxgoOKjURnjIIbe3yNjo+AgZWYVIWWl5i ZnJY6J ... ----FEE3790DC7E35189CA67CE2C 5 Recommended Practices This section outlines a series of recommended practices when using a messaging transport to exchange iCalendar objects. 5.1 Use of Content and Message IDs The [iCAL] specification makes frequent use of the URI for data types in properties such as "DESCRIPTION", "ATTACH", "CONTACT" and others. Two forms of URIs are Message ID (MID) and Content ID (CID). These are defined in [RFC-2392]. Although [RFC-2392] allows referencing messages or MIME body parts in other MIME entities or stores, it is strongly recommended that iMIP implementations include all referenced messages and body parts in a single MIME entity. Simply put, if an iCalendar object contains CID or MID references to other messages or body parts, implementations should ensure that these messages and/or body parts are transmitted with the iCalendar object. If they are not there is no guarantee that the receiving CUA will have the access or the authorization to view those objects. Melnikov (Ed.) Standards Track FORMFEED[Page 17]
RFC 2447bis iMIP June 2008 6 IANA Considerations Registration of text/calendar MIME Media Type is done in [iCal]. This document doesn't require any additional actions from IANA. 7 References 7.1 Normative References [iCAL] Desruisseaux, B., (Ed.), "Internet Calendaring and Scheduling Core Object Specification (iCalendar)", work in progress, draft-ietf-calsify-rfc2445bis-XX.txt (Updated RFC 2445) [iTIP] Daboo, C., "iCalendar Transport-Independent Interoperability Protocol (iTIP)", work in progress, draft-ietf- calsify-2446bis-XX.txt (Updates RFC 2446) [RFC-2822] Resnick, P., "Internet Message Format", RFC 2822, April 2001. [RFC-1847] Galvin, J., Murphy, S., Crocker, S. and N. Freed, "Security Multiparts for MIME: Multipart/Signed and Multipart/Encrypted", RFC 1847, October 1995. [RFC-2045] Freed, N. and N. Borenstein, "Multipurpose Internet Mail Extensions (MIME) - Part One: Format of Internet Message Bodies", RFC 2045, November 1996. [RFC-2046] Freed, N. and N. Borenstein, "Multipurpose Internet Mail Extensions (MIME) - Part Two: Media Types", RFC 2046, November 1996. [RFC-2392] Levinson, E., "Content-ID and Message-ID Uniform Resource Locators", RFC 2392, August 1998. [RFC-2119] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, March 1997. [UTF-8] Yergeau, F., "UTF-8, a transformation format of ISO 10646", STD 63, RFC 3629, November 2003. 7.2 Informative References [8BITMIME] Klensin, J., Freed, N., Rose, M., Stefferud, E., and D. Crocker, "SMTP Service Extension for 8bit-MIMEtransport", RFC 1652, July 1994. [RFC-2047] Moore, K., "Multipurpose Internet Mail Extensions (MIME) - Melnikov (Ed.) Standards Track FORMFEED[Page 18]
RFC 2447bis iMIP June 2008 Part Three: Message Header Extensions for Non-ASCII Text", RFC 2047, November 1996. [RFC-2049] Freed, N. and N. Borenstein, "Multipurpose Internet Mail Extensions (MIME) Part Five: Conformance Criteria and Examples", RFC 2049, November 1996. Melnikov (Ed.) Standards Track FORMFEED[Page 19]
RFC 2447bis iMIP June 2008 8 Authors' Addresses Alexey Melnikov (editor) Isode Ltd 5 Castle Business Village 36 Station Road Hampton, Middlesex TW12 2BX UK Email: Alexey.Melnikov@isode.com Melnikov (Ed.) Standards Track FORMFEED[Page 20]
RFC 2447bis iMIP June 2008 9. Full Copyright Statement Copyright (C) The IETF Trust (2008). This document is subject to the rights, licenses and restrictions contained in BCP 78, and except as set forth therein, the authors retain all their rights. This document and the information contained herein are provided on an "AS IS" basis and THE CONTRIBUTOR, THE ORGANIZATION HE/SHE REPRESENTS OR IS SPONSORED BY (IF ANY), THE INTERNET SOCIETY, THE IETF TRUST AND THE INTERNET ENGINEERING TASK FORCE DISCLAIM ALL WARRANTIES, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE INFORMATION HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE. Acknowledgement Funding for the RFC Editor function is provided by the IETF Administrative Support Activity (IASA). 10. Intellectual Property The IETF takes no position regarding the validity or scope of any Intellectual Property Rights or other rights that might be claimed to pertain to the implementation or use of the technology described in this document or the extent to which any license under such rights might or might not be available; nor does it represent that it has made any independent effort to identify any such rights. Information on the procedures with respect to rights in RFC documents can be found in BCP 78 and BCP 79. Copies of IPR disclosures made to the IETF Secretariat and any assurances of licenses to be made available, or the result of an attempt made to obtain a general license or permission for the use of such proprietary rights by implementers or users of this specification can be obtained from the IETF on-line IPR repository at http://www.ietf.org/ipr. The IETF invites any interested party to bring to its attention any copyrights, patents or patent applications, or other proprietary rights that may cover technology that may be required to implement this standard. Please address the information to the IETF at ietf-ipr@ietf.org. Appendix A. Changes since RFC 2447. Melnikov (Ed.) Standards Track FORMFEED[Page 21]
RFC 2447bis iMIP June 2008 Updated references. Split them into Normative and Informative. Updated examples to use example.com/example.net domains. Corrected usage of RFC 2119 language. Clarified that charset=UTF-8 is required, unless the calendar can be entirely represented in US-ASCII. Clarified that 7-bit content transfer encodings should be used unless the calendar object is known to be transferred over 8-bit clean transport. Clarified that file extension specified in the Content-Disposition header field is not to be used to override the Content-Type MIME type. Disallow use of "multiple/alternative" for slightly different representations of the same calendar. Fixed examples with ATTENDEE property to use "CUTYPE=" instead of "TYPE=". Various editorial changes to the Security Considerations section. <<TBD>> Melnikov (Ed.) Standards Track FORMFEED[Page 22]