Email Address Internationalization K. Fujiwara (EAI) JPRS Internet-Draft Oct 17, 2008 Intended status: Experimental Expires: April 20, 2009 Displaying Downgraded Messages for Email Address Internationalization draft-ietf-eai-downgraded-display-00.txt 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/ietf/1id-abstracts.txt. The list of Internet-Draft Shadow Directories can be accessed at http://www.ietf.org/shadow.html. This Internet-Draft will expire on April 20, 2009. Abstract This document describes how to display downgraded messages which originally contain internationalized E-mail addresses or internationalized header fields. Fujiwara Expires April 20, 2009 [Page 1] Internet-Draft Displaying Downgraded Messages Oct 2008 Table of Contents 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3 2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 3 3. Displaying downgraded message . . . . . . . . . . . . . . . . 4 3.1. Displaying technique 1 . . . . . . . . . . . . . . . . . . 4 3.2. Displaying technique 2 . . . . . . . . . . . . . . . . . . 4 4. Security considerations . . . . . . . . . . . . . . . . . . . 5 5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 6 6. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 6 7. Change History . . . . . . . . . . . . . . . . . . . . . . . . 6 7.1. draft-fujiwara-eai-downgraded-display: Version 00 . . . . 6 7.2. draft-ietf-eai-downgraded-display: Version 00 . . . . . . 6 8. Normative References . . . . . . . . . . . . . . . . . . . . . 6 Appendix A. Examples . . . . . . . . . . . . . . . . . . . . . . 7 A.1. Displaying technique 1 example . . . . . . . . . . . . . . 10 A.2. Displaying technique 2 example . . . . . . . . . . . . . . 10 Author's Address . . . . . . . . . . . . . . . . . . . . . . . . . 13 Intellectual Property and Copyright Statements . . . . . . . . . . 14 Fujiwara Expires April 20, 2009 [Page 2] Internet-Draft Displaying Downgraded Messages Oct 2008 1. Introduction The Email Address Internationalization (UTF8SMTP) extension document set [RFC4952] [RFC5336] [RFC5335] [RFC5337] expands Email address structure, syntax and Email header format. To avoid bouncing internationalized Email messages, the downgrading mechanism [I-D.ietf-eai-downgrade] converts an internationalized message to a traditional Email message when a server in the delivery path does not support the UTF8SMTP extension. The downgraded message is a traditional Email message, except the message has "Downgraded-" header fields. A perfect reverse-function of the downgrading does not exist because the encoding defined in [RFC2047] is not exactly reversible and Received header field downgrading may remove FOR clause information. The restoration of the downgrading should be done once at the final destination of the downgraded message such as MUAs or IMAP servers. This document describes the restoration methods as displaying techniques in MUAs. This is an informational document and it does not supersede the referenced documents. 2. Terminology 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 [RFC2119]. Specialized terms used in this specification are defined in the EAI overview [RFC4952] or in [RFC5321][RFC5322], MIME documents [RFC2045] [RFC2047] [RFC2183] [RFC2231]. This document depends on [RFC5335] and [I-D.ietf-eai-downgrade]. Key words used in these document are used in this document, too. The term "non-ASCII" is an UTF-8 string which contains at least one non-ASCII character. The term "address header field" is used for a header field which contains elements which is defined in [RFC5322]. "Address header fields" contain "From", "Sender", "Reply-To", "To", "Cc", "Bcc", "Resent-From", "Resent-Sender", "Resent-To", "Resent-Cc", "Return-Path" header fields. An "UTF8SMTP message" is an Email messages expanded by [RFC5335]. Fujiwara Expires April 20, 2009 [Page 3] Internet-Draft Displaying Downgraded Messages Oct 2008 3. Displaying downgraded message Displaying downgraded message is mostly performed by MIME decoding according to [RFC2047] and [RFC2231]. Result of MIME decoding, the header of the message still contains Downgraded-*: header fields, but the header field bodies are MIME decoded. These decoded "Downgraded-" header fields contain the original header field name and the original header field values. The recipient can read them. But the recipient's MUA cannot use the original header fields automatically. Additionally, MUAs can process "Downgraded-" header fields. It is described in Section 3.1 and Section 3.2. 3.1. Displaying technique 1 MUAs may remove "Downgraded-" from decoded "Downgraded-" header fields' name. First, decode MIME encoded header fields and MIME body part header fields according to [RFC2047] and [RFC2231]. Then, for each "Downgraded-" header field, generate new header field which field name is the original header field name and the field value is the decoded header field value, and replace the "Downgraded-" header field by the generated header field. Don't change "Downgraded-Mail-From" and "Downgraded-Rcpt-To" header fields because they do not have their original header fields. With this technique, the "address header fields" may be displayed twice, one is from downgraded header field and the other is from decoded "Downgraded-" header. 3.2. Displaying technique 2 MUAs may decode and re-generate the original header of the message. This technique may reconstruct the original message from the downgraded message. But it is not guaranteed. This technique is implemented by the following steps. Step 1: Select "Downgraded-" header fields whose original header field is an "address header field". Target header fields are "Downgraded-From", "Downgraded-Sender", "Downgraded-Reply-To", "Downgraded-To", "Downgraded-Cc", "Downgraded-Bcc", "Downgraded- Resent-From", "Downgraded-Resent-Sender", "Downgraded-Resent-To", "Downgraded-Resent-Cc", and "Downgraded-Return-Path" header Fujiwara Expires April 20, 2009 [Page 4] Internet-Draft Displaying Downgraded Messages Oct 2008 fields. Step 2: Generate new header field which field name is the original header field name and the field value is the decoded header field value from the output of Step 1. Step 3: Apply Email header fields downgrading defined in section 5 of [I-D.ietf-eai-downgrade] to the output of Step 2 without re- generating "Downgraded-" header fields. Step 4: Compare the output of Step 3 and the original header fields. If the same header fields exist for both the output and the original header fields, remove the same header fields from the original header fields. This step outputs the original header fields which is modified by this step. Before this comparison, a canonicalization described below is useful. 1. Unfold all header field continuation lines as described in [RFC5322]. 2. Insert a space character before and after separator "," if there is no space character. 3. Insert a space character before and after if there is no space character. 4. Decode whose charset is 'UTF-8'. 5. Convert all sequences of one or more WSP characters to a single space character. WSP characters here include those before and after a line folding boundary. 6. Delete all WSP characters at the end of each unfolded header field value. 7. Delete any WSP characters remaining before and after the colon separating the header field name from the header field value. The colon separator MUST be retained. Step 5: Finally, do 'Displaying technique 1' described in Section 3.1 to the output of Step 4. 4. Security considerations Displaying downgraded message may break the header of the message. MUAs should have a function to read the original received message. See "Security considerations" section in [RFC4952] for more discussion. Fujiwara Expires April 20, 2009 [Page 5] Internet-Draft Displaying Downgraded Messages Oct 2008 5. IANA Considerations 6. Acknowledgements 7. Change History This section is used for tracking the update of this document. Will be removed after finalize. 7.1. draft-fujiwara-eai-downgraded-display: Version 00 o Initial version o It is separated from Appendix A of draft-ietf-eai-downgrade-05.txt 7.2. draft-ietf-eai-downgraded-display: Version 00 o Submitted as a working group draft 8. Normative References [I-D.ietf-eai-downgrade] Fujiwara, K. and Y. Yoneya, "Downgrading mechanism for Email Address Internationalization", draft-ietf-eai-downgrade-09 (work in progress), September 2008. [RFC2045] Freed, N. and N. Borenstein, "Multipurpose Internet Mail Extensions (MIME) Part One: Format of Internet Message Bodies", RFC 2045, November 1996. [RFC2047] Moore, K., "MIME (Multipurpose Internet Mail Extensions) Part Three: Message Header Extensions for Non-ASCII Text", RFC 2047, November 1996. [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, March 1997. [RFC2183] Troost, R., Dorner, S., and K. Moore, "Communicating Presentation Information in Internet Messages: The Content-Disposition Header Field", RFC 2183, August 1997. [RFC2231] Freed, N. and K. Moore, "MIME Parameter Value and Encoded Word Extensions: Character Sets, Languages, and Continuations", RFC 2231, November 1997. Fujiwara Expires April 20, 2009 [Page 6] Internet-Draft Displaying Downgraded Messages Oct 2008 [RFC4952] Klensin, J. and Y. Ko, "Overview and Framework for Internationalized Email", RFC 4952, July 2007. [RFC5321] Klensin, J., "Simple Mail Transfer Protocol", RFC 5321, October 2008. [RFC5322] Resnick, P., Ed., "Internet Message Format", RFC 5322, October 2008. [RFC5335] Abel, Y., "Internationalized Email Headers", RFC 5335, September 2008. [RFC5336] Yao, J. and W. Mao, "SMTP Extension for Internationalized Email Addresses", RFC 5336, September 2008. [RFC5337] Newman, C. and A. Melnikov, "Internationalized Delivery Status and Disposition Notifications", RFC 5337, September 2008. Appendix A. Examples This section shows a example of displaying downgraded message. First, an example of the original UTF8SMTP message and its downgraded message are shown. They are the same as "Example 1" of [I-D.ietf-eai-downgrade]. The example UTF8SMTP message is shown in Figure 1. Message-Id: MESSAGE_ID Mime-Version: 1.0 Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: 8bit Subject: NON-ASCII-SUBJECT From: DISPLAY-local > To: DISPLAY-remote1 > Cc: DISPLAY-remote2 Date: DATE MAIL_BODY Figure 1: Original message Delivered downgraded message is shown in Figure 2. Return-Path Fujiwara Expires April 20, 2009 [Page 7] Internet-Draft Displaying Downgraded Messages Oct 2008 header will be added by the final destination MTA. Return-Path: Downgraded-Mail-From: =?UTF-8?Q?_?= =?UTF-8?Q??= Downgraded-Rcpt-To: =?UTF-8?Q?_?= =?UTF-8?Q??= Message-Id: MESSAGE_ID Mime-Version: 1.0 Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: 8bit Subject: =?UTF-8?Q?NON-ASCII-SUBJECT?= From: =?UTF-8?Q?DISPLAY-local?= Downgraded-From: =?UTF-8?Q?DISPLAY-local_>?= To: =?UTF-8?Q?DISPLAY-remote1?= Downgraded-To: =?UTF-8?Q?DISPLAY-remote1_?= =?UTF-8?Q?>?= Cc: =?UTF-8?Q?DISPLAY-remote2?= Internationalized address =?UTF-8?Q?NON-ASCII-remote2@example.org?= removed:; Downgraded-Cc: =?UTF-8?Q?DISPLAY-remote2_?= =?UTF-8?Q??= Date: DATE MAIL_BODY Figure 2: Downgraded message Figure 3 shows MIME decoded message of Figure 2. The recipient can read the original From, To, Cc header fields as Downgraded-From, Downgraded-To, Downgraded-Cc header fields. Fujiwara Expires April 20, 2009 [Page 8] Internet-Draft Displaying Downgraded Messages Oct 2008 Return-Path: Downgraded-Mail-From: Downgraded-Rcpt-To: Message-Id: MESSAGE_ID Mime-Version: 1.0 Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: 8bit Subject: NON-ASCII-SUBJECT From: DISPLAY-local Downgraded-From: DISPLAY-local > To: DISPLAY-remote1 Downgraded-To: DISPLAY-remote1 > Cc: DISPLAY-remote2 Internationalized address NON-ASCII-remote2@example.org removed:; Downgraded-Cc: DISPLAY-remote2 Date: DATE MAIL_BODY Figure 3: MIME decoded message Fujiwara Expires April 20, 2009 [Page 9] Internet-Draft Displaying Downgraded Messages Oct 2008 A.1. Displaying technique 1 example After removing "Downgraded-" from decoded "Downgraded-" header fields from Figure 3, 'Displaying technique 1' example is shown in Figure 4. Return-Path: Mail-From: Rcpt-To: Message-Id: MESSAGE_ID Mime-Version: 1.0 Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: 8bit Subject: NON-ASCII-SUBJECT From: DISPLAY-local From: DISPLAY-local > To: DISPLAY-remote1 To: DISPLAY-remote1 > Cc: DISPLAY-remote2 Internationalized address NON-ASCII-remote2@example.org removed:; Cc: DISPLAY-remote2 Date: DATE MAIL_BODY Figure 4: Displaying technique 1 A.2. Displaying technique 2 example This example shows displaying process of 'Displaying technique 2' for Figure 2. First, perform Step 1. Downgraded-From: =?UTF-8?Q?DISPLAY-local_>?= Downgraded-To: =?UTF-8?Q?DISPLAY-remote1_?= =?UTF-8?Q?>?= Downgraded-Cc: =?UTF-8?Q?DISPLAY-remote2_?= =?UTF-8?Q??= Fujiwara Expires April 20, 2009 [Page 10] Internet-Draft Displaying Downgraded Messages Oct 2008 Figure 5: Displaying technique 2: Output of Step 1 Then, perform Step 2. From: DISPLAY-local > To: DISPLAY-remote1 > Cc: DISPLAY-remote2 Figure 6: Displaying technique 2: Output of Step 2 Perform Step 3. From: =?UTF-8?Q?DISPLAY-local?= To: =?UTF-8?Q?DISPLAY-remote1?= Cc: =?UTF-8?Q?DISPLAY-remote2?= Internationalized address =?UTF-8?Q?NON-ASCII-remote2@example.org?= removed:; Figure 7: Displaying technique 2: Output of Step 3 Perform Step 4. "From", "To", "Cc" header fields are removed in Figure 8. Fujiwara Expires April 20, 2009 [Page 11] Internet-Draft Displaying Downgraded Messages Oct 2008 Return-Path: Downgraded-Mail-From: =?UTF-8?Q??= =?UTF-8?Q??= Downgraded-Rcpt-To: =?UTF-8?Q?_?= =?UTF-8?Q??= Message-Id: MESSAGE_ID Mime-Version: 1.0 Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: 8bit Subject: =?UTF-8?Q?NON-ASCII-SUBJECT?= Downgraded-From: =?UTF-8?Q?DISPLAY-local_>?= Downgraded-To: =?UTF-8?Q?DISPLAY-remote1?_?= =?UTF-8?Q?>?= Downgraded-Cc: =?UTF-8?Q?DISPLAY-remote2_?= =?UTF-8?Q??= Date: DATE MAIL_BODY Figure 8: Displaying technique 2: Output of Step 4 Perform Step 5. (Apply 'Displaying technique 1'.) Return-Path: Downgraded-Mail-From: Downgraded-Rcpt-To: Message-Id: MESSAGE_ID Mime-Version: 1.0 Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: 8bit Subject: NON-ASCII-SUBJECT From: DISPLAY-local > To: DISPLAY-remote1 > Cc: DISPLAY-remote2 Date: DATE MAIL_BODY Figure 9: Display technique 2: Decoded message Fujiwara Expires April 20, 2009 [Page 12] Internet-Draft Displaying Downgraded Messages Oct 2008 As a result, in this simple example, all original header fields are displayed in the original form. Differences between Figure 1 and Figure 9 are Return-Path, Downgraded-Mail-From, Downgraded-Rcpt-To header fields only. Author's Address Kazunori Fujiwara JPRS Chiyoda First Bldg. East 13F, 3-8-1 Nishi-Kanda Chiyoda-ku, Tokyo 101-0065 Japan Phone: +81 3 5215 8451 Email: fujiwara@jprs.co.jp Fujiwara Expires April 20, 2009 [Page 13] Internet-Draft Displaying Downgraded Messages Oct 2008 Full Copyright Statement Copyright (C) The IETF Trust (2008). 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