draft-ietf-eai-rfc5721bis-00.txt   draft-ietf-eai-rfc5721bis-01.txt 
Network Working Group R. Gellens Network Working Group R. Gellens
Internet-Draft QUALCOMM Incorporated Internet-Draft QUALCOMM Incorporated
Obsoletes: RFC5721 C. Newman Obsoletes: RFC5721 (if approved) C. Newman
(if approved) Oracle Updates: RFC1939 (if approved) Oracle
Updates: RFC1939 Jiankang. Yao Intended status: Standards Track J. Yao
(if approved) CNNIC Expires: October 1, 2011 CNNIC
Intended status: Standards Track Kazunori. Fujiwara K. Fujiwara
Expires: March 14, 2011 JPRS JPRS
September 28, 2010 March 30, 2011
POP3 Support for UTF-8 POP3 Support for UTF-8
draft-ietf-eai-rfc5721bis-00.txt draft-ietf-eai-rfc5721bis-01.txt
Abstract Abstract
This specification extends the Post Office Protocol version 3 (POP3) This specification extends the Post Office Protocol version 3 (POP3)
to support un-encoded international characters in user names, to support un-encoded international characters in user names,
passwords, mail addresses, message headers, and protocol-level passwords, mail addresses, message headers, and protocol-level
textual error strings. textual error strings.
Status of This Memo Status of This Memo
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Internet-Drafts are working documents of the Internet Engineering Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF). Note that other groups may also distribute Task Force (IETF). Note that other groups may also distribute
working documents as Internet-Drafts. The list of current Internet- working documents as Internet-Drafts. The list of current Internet-
Drafts is at http://datatracker.ietf.org/drafts/current/. Drafts is at http://datatracker.ietf.org/drafts/current/.
Internet-Drafts are draft documents valid for a maximum of six months Internet-Drafts are draft documents valid for a maximum of six months
and may be updated, replaced, or obsoleted by other documents at any and may be updated, replaced, or obsoleted by other documents at any
time. It is inappropriate to use Internet-Drafts as reference time. It is inappropriate to use Internet-Drafts as reference
material or to cite them other than as "work in progress." material or to cite them other than as "work in progress."
This Internet-Draft will expire on March 14, 2011. This Internet-Draft will expire on October 1, 2011.
Copyright Notice Copyright Notice
Copyright (c) 2010 IETF Trust and the persons identified as the Copyright (c) 2011 IETF Trust and the persons identified as the
document authors. All rights reserved. document authors. All rights reserved.
This document is subject to BCP 78 and the IETF Trust's Legal This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents Provisions Relating to IETF Documents
(http://trustee.ietf.org/license-info) in effect on the date of (http://trustee.ietf.org/license-info) in effect on the date of
publication of this document. Please review these documents publication of this document. Please review these documents
carefully, as they describe your rights and restrictions with respect carefully, as they describe your rights and restrictions with respect
to this document. Code Components extracted from this document must to this document. Code Components extracted from this document must
include Simplified BSD License text as described in Section 4.e of include Simplified BSD License text as described in Section 4.e of
the Trust Legal Provisions and are provided without warranty as the Trust Legal Provisions and are provided without warranty as
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1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3
1.1. Conventions Used in This Document . . . . . . . . . . . . 3 1.1. Conventions Used in This Document . . . . . . . . . . . . 3
2. LANG Capability . . . . . . . . . . . . . . . . . . . . . . . 4 2. LANG Capability . . . . . . . . . . . . . . . . . . . . . . . 4
3. UTF8 Capability . . . . . . . . . . . . . . . . . . . . . . . 6 3. UTF8 Capability . . . . . . . . . . . . . . . . . . . . . . . 6
3.1. The UTF8 Command . . . . . . . . . . . . . . . . . . . . . 7 3.1. The UTF8 Command . . . . . . . . . . . . . . . . . . . . . 7
3.2. USER Argument to UTF8 Capability . . . . . . . . . . . . . 8 3.2. USER Argument to UTF8 Capability . . . . . . . . . . . . . 8
4. Native UTF-8 Maildrops . . . . . . . . . . . . . . . . . . . . 9 4. Native UTF-8 Maildrops . . . . . . . . . . . . . . . . . . . . 9
5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 9 5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 9
6. Security Considerations . . . . . . . . . . . . . . . . . . . 9 6. Security Considerations . . . . . . . . . . . . . . . . . . . 9
7. References . . . . . . . . . . . . . . . . . . . . . . . . . . 10 7. Change History . . . . . . . . . . . . . . . . . . . . . . . . 10
7.1. Normative References . . . . . . . . . . . . . . . . . . . 10 7.1. draft-ietf-eai-rfc5721bis: Version 00 . . . . . . . . . . 10
7.2. Informative References . . . . . . . . . . . . . . . . . . 11 7.2. draft-ietf-eai-rfc5721bis: Version 01 . . . . . . . . . . 10
8. References . . . . . . . . . . . . . . . . . . . . . . . . . . 10
8.1. Normative References . . . . . . . . . . . . . . . . . . . 10
8.2. Informative References . . . . . . . . . . . . . . . . . . 11
Appendix A. Design Rationale . . . . . . . . . . . . . . . . . . 12 Appendix A. Design Rationale . . . . . . . . . . . . . . . . . . 12
Appendix B. Acknowledgments . . . . . . . . . . . . . . . . . . . 12 Appendix B. Acknowledgments . . . . . . . . . . . . . . . . . . . 12
1. Introduction 1. Introduction
This document forms part of the Email Address Internationalization This document forms part of the Email Address Internationalization
(EAI) protocols described in the EAI Framework document (EAI) protocols described in the EAI Framework document
[I-D.ietf-eai-frmwrk-4952bis]. As part of the overall EAI work, [I-D.ietf-eai-frmwrk-4952bis]. As part of the overall EAI work,
email messages may be transmitted and delivered containing un-encoded email messages may be transmitted and delivered containing un-encoded
UTF-8 characters, and mail drops that are accessed using POP3 UTF-8 characters, and mail drops that are accessed using POP3
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names and passwords outside the ASCII character set, and a mechanism names and passwords outside the ASCII character set, and a mechanism
to support UTF-8 protocol-level error strings in a language to support UTF-8 protocol-level error strings in a language
appropriate for the user. appropriate for the user.
Within this specification, the term "down-conversion" refers to the Within this specification, the term "down-conversion" refers to the
process of modifying a message containing UTF-8 headers process of modifying a message containing UTF-8 headers
[I-D.ietf-eai-rfc5335bis] or body parts with 8bit content-transfer- [I-D.ietf-eai-rfc5335bis] or body parts with 8bit content-transfer-
encoding, as defined in MIME Section 2.8 [RFC2045], into conforming encoding, as defined in MIME Section 2.8 [RFC2045], into conforming
7-bit Internet Message Format [RFC5322] with message header 7-bit Internet Message Format [RFC5322] with message header
extensions for non-ASCII text [RFC2047] and other 7-bit encodings. extensions for non-ASCII text [RFC2047] and other 7-bit encodings.
Down-conversion is specified by "Message-Downgrading for Email Down-conversion is specified by "Post-delivery Message Downgrading
Address Internationalization" [message-downgrade]. for Internationalized Email Messages" [popimap-downgrade].
1.1. Conventions Used in This Document 1.1. Conventions Used in This Document
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
document are to be interpreted as described in "Key words for use in document are to be interpreted as described in "Key words for use in
RFCs to Indicate Requirement Levels" [RFC2119]. RFCs to Indicate Requirement Levels" [RFC2119].
The formal syntax uses the Augmented Backus-Naur Form (ABNF)
[RFC5234] notation, including the core rules defined in Appendix B of
RFC 5234.
In examples, "C:" and "S:" indicate lines sent by the client and In examples, "C:" and "S:" indicate lines sent by the client and
server, respectively. If a single "C:" or "S:" label applies to server, respectively. If a single "C:" or "S:" label applies to
multiple lines, then the line breaks between those lines are for multiple lines, then the line breaks between those lines are for
editorial clarity only and are not part of the actual protocol editorial clarity only and are not part of the actual protocol
exchange. exchange.
Note that examples always use 7-bit ASCII characters due to Note that examples always use 7-bit ASCII characters due to
limitations of this document format; in particular, some examples for limitations of this document format; in particular, some examples for
the "LANG" command may appear silly as a result. the "LANG" command may appear silly as a result.
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The UTF8 command enables UTF-8 mode. The UTF8 command has no The UTF8 command enables UTF-8 mode. The UTF8 command has no
parameters. parameters.
Maildrops can natively store UTF-8 or be limited to ASCII. UTF-8 Maildrops can natively store UTF-8 or be limited to ASCII. UTF-8
mode has no effect on messages in an ASCII-only maildrop. Messages mode has no effect on messages in an ASCII-only maildrop. Messages
in native UTF-8 maildrops can be ASCII or UTF-8 using in native UTF-8 maildrops can be ASCII or UTF-8 using
internationalized headers [I-D.ietf-eai-rfc5335bis] and/or 8bit internationalized headers [I-D.ietf-eai-rfc5335bis] and/or 8bit
content-transfer-encoding, as defined in MIME Section 2.8 [RFC2045]. content-transfer-encoding, as defined in MIME Section 2.8 [RFC2045].
In UTF-8 mode, both UTF-8 and ASCII messages are sent to the client In UTF-8 mode, both UTF-8 and ASCII messages are sent to the client
as-is (without conversion). When not in UTF-8 mode, UTF-8 messages as-is (without conversion). When not in UTF-8 mode, UTF-8 messages
in a native UTF-8 maildrop MUST NOT be sent to the client as-is. in a native UTF-8 maildrop MUST NOT be sent to the client as-is. The
UTF-8 messages in a native UTF-8 maildrop MUST be down-converted UTF8 Commands MAY fail. UTF-8 messages in a native UTF-8 maildrop
(downgraded) to comply with unextended POP and Internet Mail Format MAY be down-converted (downgraded) to comply with unextended POP and
without UTF-8 mode support. Internet Mail Format without UTF-8 mode support.
Note that even in UTF-8 mode, MIME binary content-transfer-encoding Note that even in UTF-8 mode, MIME binary content-transfer-encoding
is still not permitted. is still not permitted.
The octet count (size) of a message reported in a response to the The octet count (size) of a message reported in a response to the
LIST command SHOULD match the actual number of octets sent in a RETR LIST command SHOULD match the actual number of octets sent in a RETR
response (not counting byte-stuffing). Sizes reported elsewhere, response (not counting byte-stuffing). Sizes reported elsewhere,
such as in STAT responses and non-standardized, free-form text in such as in STAT responses and non-standardized, free-form text in
positive status indicators (following "+OK") need not be accurate, positive status indicators (following "+OK") need not be accurate,
but it is preferable if they are. but it is preferable if they are.
Mail stores are either ASCII or native UTF-8, and clients either Mail stores are either ASCII or native UTF-8, and clients either
issue the UTF8 command or not. The message needs converting only issue the UTF8 command or not. The message needs converting only
when it is native UTF-8 and the client has not issued the UTF8 when it is native UTF-8 and the client has not issued the UTF8
command, in which case the server must down-convert it. The down- command, in which case the server MAY choose to down-convert it. The
converted message may be larger. The server may choose various down-converted message may be larger. The server may choose various
strategies regarding down-conversion, which include when to down- strategies regarding down-conversion, which include when to down-
convert, whether to cache or store the down-converted form of a convert, whether to cache or store the down-converted form of a
message (and if so, for how long), and whether to calculate or retain message (and if so, for how long), and whether to calculate or retain
the size of a down-converted message independently of the down- the size of a down-converted message independently of the down-
converted content. If the server does not have immediate access to converted content. If the server does not have immediate access to
the accurate down-converted size, it may be faster to estimate rather the accurate down-converted size, it may be faster to estimate rather
than calculate it. Servers are expected to normally follow the RFC than calculate it. Servers are expected to normally follow the RFC
1939 [RFC1939] text on using the "exact size" in a scan listing, but 1939 [RFC1939] text on using the "exact size" in a scan listing, but
there may be situations with maildrops containing very large numbers there may be situations with maildrops containing very large numbers
of messages in which this might be a problem. If the server does of messages in which this might be a problem. If the server does
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Use of UTF-8 characters in the AUTH command is governed by the POP3 Use of UTF-8 characters in the AUTH command is governed by the POP3
SASL [RFC5034] mechanism. SASL [RFC5034] mechanism.
4. Native UTF-8 Maildrops 4. Native UTF-8 Maildrops
When a POP3 server uses a native UTF-8 maildrop, it is the When a POP3 server uses a native UTF-8 maildrop, it is the
responsibility of the server to comply with the POP3 base responsibility of the server to comply with the POP3 base
specification [RFC1939] and Internet Message Format [RFC5322] when specification [RFC1939] and Internet Message Format [RFC5322] when
not in UTF-8 mode. Mechanisms for 7-bit downgrading to help comply not in UTF-8 mode. Mechanisms for 7-bit downgrading to help comply
with the standards are described in [message-downgrade]. with the standards are described in [popimap-downgrade].
5. IANA Considerations 5. IANA Considerations
This specification adds two new capabilities ("UTF8" and "LANG") to This specification updates two capabilities ("UTF8" and "LANG") to
the POP3 capability registry [RFC2449]. the POP3 capability registry [RFC2449].
6. Security Considerations 6. Security Considerations
The security considerations of UTF-8 [RFC3629] and SASLprep [RFC4013] The security considerations of UTF-8 [RFC3629] and SASLprep [RFC4013]
apply to this specification, particularly with respect to use of apply to this specification, particularly with respect to use of
UTF-8 in user names and passwords. UTF-8 in user names and passwords.
The "LANG *" command might reveal the existence and preferred The "LANG *" command might reveal the existence and preferred
language of a user to an active attacker probing the system if the language of a user to an active attacker probing the system if the
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Modifying server authentication code (in this case, to support UTF8 Modifying server authentication code (in this case, to support UTF8
command) needs to be done with care to avoid introducing command) needs to be done with care to avoid introducing
vulnerabilities (for example, in string parsing). vulnerabilities (for example, in string parsing).
The UTF8 command description (Section 3.1) contains a discussion on The UTF8 command description (Section 3.1) contains a discussion on
reporting inaccurate sizes. An additional risk to doing so is that, reporting inaccurate sizes. An additional risk to doing so is that,
if a client allocates buffers based on the reported size, it may if a client allocates buffers based on the reported size, it may
overrun the buffer, crash, or have other problems if the message data overrun the buffer, crash, or have other problems if the message data
is larger than reported. is larger than reported.
7. References 7. Change History
7.1. Normative References 7.1. draft-ietf-eai-rfc5721bis: Version 00
following the new charter
7.2. draft-ietf-eai-rfc5721bis: Version 01
refine the texts
8. References
8.1. Normative References
[I-D.ietf-eai-frmwrk-4952bis] Klensin, J. and Y. Ko, "Overview and [I-D.ietf-eai-frmwrk-4952bis] Klensin, J. and Y. Ko, "Overview and
Framework for Internationalized Framework for Internationalized
Email", Email",
draft-ietf-eai-frmwrk-4952bis-07 (work draft-ietf-eai-frmwrk-4952bis-10 (work
in progress), August 2010. in progress), September 2010.
[I-D.ietf-eai-rfc5335bis] Yang, A. and S. Steele, [I-D.ietf-eai-rfc5335bis] Yang, A. and S. Steele,
"Internationalized Email Headers", "Internationalized Email Headers",
draft-ietf-eai-rfc5335bis-02 (work in draft-ietf-eai-rfc5335bis-10 (work in
progress), August 2010. progress), March 2011.
[RFC1939] Myers, J. and M. Rose, "Post Office [RFC1939] Myers, J. and M. Rose, "Post Office
Protocol - Version 3", STD 53, Protocol - Version 3", STD 53,
RFC 1939, May 1996. RFC 1939, May 1996.
[RFC2045] Freed, N. and N. Borenstein, [RFC2045] Freed, N. and N. Borenstein,
"Multipurpose Internet Mail Extensions "Multipurpose Internet Mail Extensions
(MIME) Part One: Format of Internet (MIME) Part One: Format of Internet
Message Bodies", RFC 2045, Message Bodies", RFC 2045,
November 1996. November 1996.
skipping to change at page 11, line 21 skipping to change at page 11, line 30
RFC 3629, November 2003. RFC 3629, November 2003.
[RFC4013] Zeilenga, K., "SASLprep: Stringprep [RFC4013] Zeilenga, K., "SASLprep: Stringprep
Profile for User Names and Passwords", Profile for User Names and Passwords",
RFC 4013, February 2005. RFC 4013, February 2005.
[RFC4647] Phillips, A. and M. Davis, "Matching [RFC4647] Phillips, A. and M. Davis, "Matching
of Language Tags", BCP 47, RFC 4647, of Language Tags", BCP 47, RFC 4647,
September 2006. September 2006.
[RFC5234] Crocker, D. and P. Overell, "Augmented
BNF for Syntax Specifications: ABNF",
STD 68, RFC 5234, January 2008.
[RFC5322] Resnick, P., Ed., "Internet Message [RFC5322] Resnick, P., Ed., "Internet Message
Format", RFC 5322, October 2008. Format", RFC 5322, October 2008.
[RFC5646] Phillips, A. and M. Davis, "Tags for [RFC5646] Phillips, A. and M. Davis, "Tags for
Identifying Languages", BCP 47, Identifying Languages", BCP 47,
RFC 5646, September 2009. RFC 5646, September 2009.
7.2. Informative References 8.2. Informative References
[RFC2595] Newman, C., "Using TLS with IMAP, POP3 [RFC2595] Newman, C., "Using TLS with IMAP, POP3
and ACAP", RFC 2595, June 1999. and ACAP", RFC 2595, June 1999.
[RFC4952] Klensin, J. and Y. Ko, "Overview and
Framework for Internationalized
Email", RFC 4952, July 2007.
[RFC5034] Siemborski, R. and A. Menon-Sen, "The [RFC5034] Siemborski, R. and A. Menon-Sen, "The
Post Office Protocol (POP3) Simple Post Office Protocol (POP3) Simple
Authentication and Security Layer Authentication and Security Layer
(SASL) Authentication Mechanism", (SASL) Authentication Mechanism",
RFC 5034, July 2007. RFC 5034, July 2007.
[message-downgrade] Fujiwara, K. and Y. Yoneya, "Message [popimap-downgrade] Fujiwara, K., "Post-delivery Message
Downgrading for Email Address Downgrading for Internationalized
Internationalization (EAI) Maildrops", Email Messages",
draft-ietf-eai-rfc5504bis-00 (work in draft-ietf-eai-popimap-downgrade-00
progress), Sep 2010. (work in progress), October 2010.
Appendix A. Design Rationale Appendix A. Design Rationale
This non-normative section discusses the reasons behind some of the This non-normative section discusses the reasons behind some of the
design choices in the above specification. design choices in the above specification.
Due to interoperability problems with RFC 2047 and limited deployment Due to interoperability problems with RFC 2047 and limited deployment
of RFC 2231, it is hoped these 7-bit encoding mechanisms can be of RFC 2231, it is hoped these 7-bit encoding mechanisms can be
deprecated in the future when UTF-8 header support becomes prevalent. deprecated in the future when UTF-8 header support becomes prevalent.
 End of changes. 19 change blocks. 
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