draft-ietf-imapext-i18n-02.txt   draft-ietf-imapext-i18n-03.txt 
Network Working Group Chris Newman Network Working Group Chris Newman
Request for Comments: DRAFT Sun Microsystems Request for Comments: DRAFT Sun Microsystems
draft-ietf-imapext-i18n-02.txt Arnt Gulbrandsen draft-ietf-imapext-i18n-03.txt Arnt Gulbrandsen
Oryx Mail Systems Oryx Mail Systems
May 2004 June 2004
Internet Message Access Protocol Internationalization Internet Message Access Protocol Internationalization
Status of this Memo Status of this Memo
This document is an Internet-Draft and is in full conformance with This document is an Internet-Draft and is in full conformance with
all provisions of Section 10 of RFC2026. Internet-Drafts are all provisions of Section 10 of RFC2026. Internet-Drafts are
working documents of the Internet Engineering Task Force (IETF), its working documents of the Internet Engineering Task Force (IETF), its
areas, and its working groups. Note that other groups may also areas, and its working groups. Note that other groups may also
distribute working documents as Internet-Drafts. distribute working documents as Internet-Drafts.
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Internet Message Access Protocol (IMAP) version 4rev1 has basic Internet Message Access Protocol (IMAP) version 4rev1 has basic
support for non-ASCII characters in mailbox names and search support for non-ASCII characters in mailbox names and search
substrings. It also supports non-ASCII message headers and content substrings. It also supports non-ASCII message headers and content
encoded as specified by Multipurpose Internet Mail Extensions encoded as specified by Multipurpose Internet Mail Extensions
(MIME). This specification defines a collection of IMAP extensions (MIME). This specification defines a collection of IMAP extensions
which improve international support including comparator negotiation which improve international support including comparator negotiation
for search, sort and thread, language negotiation for international for search, sort and thread, language negotiation for international
error text, and translations for namespace prefixes. error text, and translations for namespace prefixes.
Internet-draft May 2004 Internet-draft June 2004
Table of Contents Table of Contents
1. Conventions Used in this Document . . . . . . . . . . . . . . 3 1. Conventions Used in this Document . . . . . . . . . . . . . . 3
2. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3 2. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3
3. LANGUAGE Extension . . . . . . . . . . . . . . . . . . . . . 3 3. LANGUAGE Extension . . . . . . . . . . . . . . . . . . . . . 3
3.1 LANGUAGE Extension Requirements . . . . . . . . . . . . . . . 3 3.1 LANGUAGE Extension Requirements . . . . . . . . . . . . . . . 3
3.2 LANGUAGE Command . . . . . . . . . . . . . . . . . . . . . . 4 3.2 LANGUAGE Command . . . . . . . . . . . . . . . . . . . . . . 4
3.3 LANGUAGE Response . . . . . . . . . . . . . . . . . . . . . . 5 3.3 LANGUAGE Response . . . . . . . . . . . . . . . . . . . . . . 5
3.4 TRANSLATION Extension to the NAMESPACE Response . . . . . . . 6 3.4 TRANSLATION Extension to the NAMESPACE Response . . . . . . . 6
3.5 Formal Syntax . . . . . . . . . . . . . . . . . . . . . . . . 6 3.5 Formal Syntax . . . . . . . . . . . . . . . . . . . . . . . . 6
4. COMPARATOR Extension . . . . . . . . . . . . . . . . . . . . 7 4. COMPARATOR Extension . . . . . . . . . . . . . . . . . . . . 7
4.1 COMPARATOR Extension Requirements . . . . . . . . . . . . . . 8 4.1 COMPARATOR Extension Requirements . . . . . . . . . . . . . . 8
4.2 Comparators and Charsets . . . . . . . . . . . . . . . . . . 9 4.2 Comparators and Charsets . . . . . . . . . . . . . . . . . . 9
4.3 COMPARATOR Command . . . . . . . . . . . . . . . . . . . . . 9 4.3 COMPARATOR Command . . . . . . . . . . . . . . . . . . . . . 9
4.4 COMPARATOR Response . . . . . . . . . . . . . . . . . . . . . 10 4.4 COMPARATOR Response . . . . . . . . . . . . . . . . . . . . . 10
4.5 COMPARATOR SEARCH and SORT Key . . . . . . . . . . . . . . . 10 4.5 Formal Syntax . . . . . . . . . . . . . . . . . . . . . . . . 10
4.6 Formal Syntax . . . . . . . . . . . . . . . . . . . . . . . . 10
5. Other IMAP Internationalization Issues . . . . . . . . . . . 11 5. Other IMAP Internationalization Issues . . . . . . . . . . . 11
5.1 UTF-8 Userids and Passwords . . . . . . . . . . . . . . . . . 11 5.1 UTF-8 Userids and Passwords . . . . . . . . . . . . . . . . . 11
5.2 UTF-8 Mailbox Names . . . . . . . . . . . . . . . . . . . . . 12 5.2 UTF-8 Mailbox Names . . . . . . . . . . . . . . . . . . . . . 11
5.3 UTF-8 Domains, Addresses and Mail Headers . . . . . . . . . . 12 5.3 UTF-8 Domains, Addresses and Mail Headers . . . . . . . . . . 12
6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 12 6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 12
7. Security Considerations . . . . . . . . . . . . . . . . . . . 12 7. Security Considerations . . . . . . . . . . . . . . . . . . . 12
8. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 13 8. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 13
9. Relevant Standards for i18n IMAP Implementations . . . . . . 13 9. Relevant Standards for i18n IMAP Implementations . . . . . . 13
Normative References . . . . . . . . . . . . . . . . . . . . 14 Normative References . . . . . . . . . . . . . . . . . . . . 14
Informative References . . . . . . . . . . . . . . . . . . . 14 Informative References . . . . . . . . . . . . . . . . . . . 14
Author's Address . . . . . . . . . . . . . . . . . . . . . . 15 Author's Address . . . . . . . . . . . . . . . . . . . . . . 15
Intellectual Property and Copyright Statements . . . . . . . 16 Intellectual Property and Copyright Statements . . . . . . . 16
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The formal syntax use the Augmented Backus-Naur Form (ABNF) [2] The formal syntax use the Augmented Backus-Naur Form (ABNF) [2]
notation including the core rules defined in Appendix A of RFC 2234. notation including the core rules defined in Appendix A of RFC 2234.
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.
Internet-draft May 2004 Internet-draft June 2004
2. Introduction 2. Introduction
This specification defines two IMAP4rev1 [6] extensions to enhance This specification defines two IMAP4rev1 [6] extensions to enhance
international support. These extensions can be advertised and international support. These extensions can be advertised and
implemented separately. implemented separately.
The LANGUAGE extension allows the client to request a suitable The LANGUAGE extension allows the client to request a suitable
language for protocol error messages and in combination with the language for protocol error messages and in combination with the
NAMESPACE extension [4] enables namespace translations. NAMESPACE extension [4] enables namespace translations.
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default" as described in [3] as its default language until another default" as described in [3] as its default language until another
supported language is negotiated by the client. A server MUST supported language is negotiated by the client. A server MUST
include "i-default" as one of its supported languages. include "i-default" as one of its supported languages.
A client that supports this extension MUST be prepared for a A client that supports this extension MUST be prepared for a
possible NAMESPACE response [4] from the server. possible NAMESPACE response [4] from the server.
The LANGUAGE command is valid in not-authenticated, authenticated The LANGUAGE command is valid in not-authenticated, authenticated
and selected states. and selected states.
Internet-draft May 2004 Internet-draft June 2004
3.2 LANGUAGE Command 3.2 LANGUAGE Command
Arguments: Optional language range argument. Arguments: Optional language range argument.
Response: A possible LANGUAGE response (see Section 3.3). Response: A possible LANGUAGE response (see Section 3.3).
A possible NAMESPACE response as defined by [4]. A possible NAMESPACE response as defined by [4].
Result: OK - Command completed Result: OK - Command completed
NO - Could not complete command NO - Could not complete command
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it MAY return a tagged NO response to the enumeration request. it MAY return a tagged NO response to the enumeration request.
< The server defaults to using English i-default responses until < The server defaults to using English i-default responses until
the user explicitly changes the language. > the user explicitly changes the language. >
C: A001 LOGIN KAREN PASSWORD C: A001 LOGIN KAREN PASSWORD
S: A001 OK LOGIN completed S: A001 OK LOGIN completed
< Client requested MUL language. Server MUST reply with BAD. > < Client requested MUL language. Server MUST reply with BAD. >
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C: A002 LANGUAGE MUL C: A002 LANGUAGE MUL
S: A002 BAD Invalid language MUL S: A002 BAD Invalid language MUL
< A LANGUAGE command with no arguments is a request to enumerate < A LANGUAGE command with no arguments is a request to enumerate
the list of languages the server supports. > the list of languages the server supports. >
C: A003 LANGUAGE C: A003 LANGUAGE
S: * LANGUAGE (EN DE IT i-default) S: * LANGUAGE (EN DE IT i-default)
S: A003 OK Supported languages have been enumerated S: A003 OK Supported languages have been enumerated
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Contents: A list of one or more language tags. Contents: A list of one or more language tags.
The LANGUAGE response occurs as a result of a LANGUAGE command. A The LANGUAGE response occurs as a result of a LANGUAGE command. A
LANGUAGE response with a list containing a single language tag LANGUAGE response with a list containing a single language tag
indicates that the server is now using that language. A LANGUAGE indicates that the server is now using that language. A LANGUAGE
response with a list containing multiple language tags indicates the response with a list containing multiple language tags indicates the
server is communicating a list of available languages to the client, server is communicating a list of available languages to the client,
and no change in the active language has been made. and no change in the active language has been made.
Internet-draft May 2004 Internet-draft June 2004
3.4 TRANSLATION Extension to the NAMESPACE Response 3.4 TRANSLATION Extension to the NAMESPACE Response
If the server supports the IMAP4 NAMESPACE command [4], the server If the server supports the IMAP4 NAMESPACE command [4], the server
MUST return an untagged NAMESPACE response when a language is MUST return an untagged NAMESPACE response when a language is
negotiated. However the server MUST NOT return a NAMESPACE response negotiated. However the server MUST NOT return a NAMESPACE response
if it is in not-authenticated state. if it is in not-authenticated state.
If as a result of the newly negotiated language, localized If as a result of the newly negotiated language, localized
representations of the namespace prefixes are available, the server representations of the namespace prefixes are available, the server
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Languages [5], and UTF-8 [7]. Languages [5], and UTF-8 [7].
command-any =/ language-cmd command-any =/ language-cmd
; LANGUAGE command is valid in all states ; LANGUAGE command is valid in all states
language-cmd = "LANGUAGE" [SP lang-range-quoted] language-cmd = "LANGUAGE" [SP lang-range-quoted]
language-data = "LANGUAGE" SP "(" lang-tag-quoted *(SP lang- language-data = "LANGUAGE" SP "(" lang-tag-quoted *(SP lang-
tag-quoted) ")" tag-quoted) ")"
Internet-draft June 2004
namespace-trans = SP DQUOTE "TRANSLATION" DQUOTE SP "(" string namespace-trans = SP DQUOTE "TRANSLATION" DQUOTE SP "(" string
")" ")"
Internet-draft May 2004
; the string is encoded in Modified UTF-7. ; the string is encoded in Modified UTF-7.
; this is a subset of the syntax permitted by ; this is a subset of the syntax permitted by
; the Namespace_Response_Extension rule in RFC 2342 ; the Namespace_Response_Extension rule in RFC 2342
lang-range-quoted = astring lang-range-quoted = astring
; Once any literal wrapper or quoting is removed, this ; Once any literal wrapper or quoting is removed, this
; follows the language-range rule in section 2.5 of RFC 3066 ; follows the language-range rule in section 2.5 of RFC 3066
lang-tag-quoted = astring lang-tag-quoted = astring
; Once any literal wrapper or quoting is removed, this ; Once any literal wrapper or quoting is removed, this
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IMAP4rev1 [6] includes the SEARCH command which can be used to IMAP4rev1 [6] includes the SEARCH command which can be used to
locate messages matching criteria including human-readable text. locate messages matching criteria including human-readable text.
The SORT extension [15] to IMAP allows the client to ask the server The SORT extension [15] to IMAP allows the client to ask the server
to determine the order of messages based on criteria including to determine the order of messages based on criteria including
human-readable text. These mechanisms require the ability to human-readable text. These mechanisms require the ability to
support non-English search and sort functions. support non-English search and sort functions.
This section defines an IMAP extension to negotiate use of This section defines an IMAP extension to negotiate use of
comparators [8] to internationalize IMAP SEARCH, SORT and THREAD. comparators [8] to internationalize IMAP SEARCH, SORT and THREAD.
The IMAP extension consists of a new command to determine or change The IMAP extension consists of a new command to determine or change
the active comparator, a new response to indicate the active the active comparator and a new response to indicate the active
comparator and possibly other available comparators, SEARCH and SORT comparator and possibly other available comparators.
keys which can be used to change comparators on-the-fly, and an
additional response code to indicate that the failure of a SEARCH or
SORT command was due to an invalid comparator.
The term "default comparator" refers to the comparator which is used The term "default comparator" refers to the comparator which is used
by SEARCH and SORT absent any negotiation using the COMPARATOR by SEARCH and SORT absent any negotiation using the COMPARATOR
command or SEARCH/SORT key. The term "active comparator" refers to command. The term "active comparator" refers to the comparator
the comparator which will be used within a session by SEARCH and which will be used within a session e.g. by SEARCH and SORT. The
SORT absent use of the COMPARATOR SEARCH/SORT key. The COMPARATOR COMPARATOR command is used to change the active comparator.
Internet-draft May 2004
command is used to change the active comparator. The term "selected Internet-draft June 2004
comparator" refers to the comparator selected by the most recent
COMPARATOR SEARCH/SORT key within the context of the current SEARCH/
SORT program or the active comparator if there is no COMPARATOR
SEARCH/SORT key yet seen in context.
The selected comparator applies to the following SEARCH keys: "BCC", The active comparator applies to the following SEARCH keys: "BCC",
"BODY", "CC", "FROM", "SUBJECT", "TEXT", "TO" and "HEADER". If the "BODY", "CC", "FROM", "SUBJECT", "TEXT", "TO" and "HEADER". If the
server also advertises the "SORT" extension, then the selected server also advertises the "SORT" extension, then the active
comparator applies to the following SORT keys: "CC", "FROM", comparator applies to the following SORT keys: "CC", "FROM",
"SUBJECT" and "TO". If the server advertises the "SUBJECT" and "TO". If the server advertises the
THREAD=ORDEREDSUBJECT, then the active comparator applies to the THREAD=ORDEREDSUBJECT, then the active comparator applies to the
ORDEREDSUBJECT threading algorithm. ORDEREDSUBJECT threading algorithm.
For SORT and THREAD, the pre-processing necessary to extract the For SORT and THREAD, the pre-processing necessary to extract the
base subject text from a Subject header occurs prior to the base subject text from a Subject header occurs prior to the
application of a comparator. application of a comparator.
4.1 COMPARATOR Extension Requirements 4.1 COMPARATOR Extension Requirements
IMAP servers that support this extension MUST list the keyword IMAP servers that support this extension MUST list the keyword
COMPARATOR in their CAPABILITY data once IMAP enters authenticated COMPARATOR in their CAPABILITY data once IMAP enters authenticated
state. state, and MAY list that keyword in other states.
A server that advertises this extension MUST implement the en;ascii- A server that advertises this extension MUST implement the en;ascii-
casemap and i;octet comparators, as defined in [8]. A server casemap and i;octet comparators, as defined in [8]. A server
intended to be deployed globally MUST implement the intended to be deployed globally MUST implement the
i;basic;uca=3.1.1;uv=3.2 comparator. i;basic;uca=3.1.1;uv=3.2 comparator.
A server that advertises this extension MUST use a registered case- A server that advertises this extension MUST use a registered case-
insensitive comparator which supports the substring matching insensitive comparator which supports the substring matching
function as the default comparator. If the server also advertises function as the default comparator. If the server also advertises
the SORT or THREAD=ORDEREDSUBJECT extensions, then the default the SORT or THREAD=ORDEREDSUBJECT extensions, then the default
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administrator, and MAY be sensitive to the current user. Once the administrator, and MAY be sensitive to the current user. Once the
IMAP connection enters authenticated state, the default comparator IMAP connection enters authenticated state, the default comparator
MUST remain static for the remainder of that connection. MUST remain static for the remainder of that connection.
A server that advertises this extension MUST support UTF-8 as a A server that advertises this extension MUST support UTF-8 as a
SEARCH charset. SEARCH charset.
The COMPARATOR command is valid in authenticated and selected The COMPARATOR command is valid in authenticated and selected
states. states.
Internet-draft May 2004 Internet-draft June 2004
4.2 Comparators and Charsets 4.2 Comparators and Charsets
For SEARCH, SORT and THREAD operations that apply to message For SEARCH, SORT and THREAD operations that apply to message
headers, the server is responsible for removing the MIME header headers, the server is responsible for removing the MIME header
encoding [10] and converting the text of any known charsets to UTF-8 encoding [10] and converting the text of any known charsets to UTF-8
prior to applying the comparator algorithm. Unknown charsets should prior to applying the comparator algorithm. Unknown charsets should
never match when using the SEARCH command, and will sort together never match when using the SEARCH command, and should sort together
with invalid comparator input for the SORT and THREAD commands. with invalid comparator input for the SORT and THREAD commands.
When message text is in a known charset other than UTF-8, the server When message text is in a known charset other than UTF-8, the server
is responsible for converting that text to UTF-8 prior to applying is responsible for converting that text to UTF-8 prior to applying
the comparator. When message text is in an unknown charset, then the comparator. When message text is in an unknown charset, then
the text should be skipped by the SEARCH command unless the the text should be skipped by the SEARCH command unless the
comparator is i;octet. comparator is i;octet.
4.3 COMPARATOR Command 4.3 COMPARATOR Command
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BAD - arguments invalid BAD - arguments invalid
The COMPARATOR command is used to determine or change the active The COMPARATOR command is used to determine or change the active
comparator. When issued with no arguments, it will result in a comparator. When issued with no arguments, it will result in a
COMPARATOR response indicating the currently active comparator. COMPARATOR response indicating the currently active comparator.
When issued with one or more comparator order argument, it will When issued with one or more comparator order argument, it will
change the active comparator if any comparator matches any argument. change the active comparator if any comparator matches any argument.
The COMPARATOR response will list other matching comparators if more The COMPARATOR response will list other matching comparators if more
than one matches the specified patterns. than one matches the specified patterns.
When the single argument "*" is used with the COMPARATOR command, it The argument "*" refers to the server's default comparator.
will activate the server's default comparator. Otherwise each argument is an comparator specification as defined in
the Internet Application Protocol Comparator Registry [8].
< The client requests activating a Czech comparator if possible, < The client requests activating a Czech comparator if possible,
or else a generic international comparator which it considers or else a generic international comparator which it considers
suitable for Czech. The server picks the first supported suitable for Czech. The server picks the first supported
comparator. > comparator. >
C: A001 COMPARATOR cz;* i;basic* C: A001 COMPARATOR cz;* i;basic*
S: * COMPARATOR i;basic;uca=3.1.1;uv=3.2 S: * COMPARATOR i;basic;uca=3.1.1;uv=3.2
S: A001 OK Will use i;basic;uca=3.1.1;uv=3.2 for collation S: A001 OK Will use i;basic;uca=3.1.1;uv=3.2 for collation
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< The client requests pure octet matching, then does a search
for potential GIF files, then switches back to its usual
comparator. >
C: B123 COMPARATOR i;octet
S: * COMPARATOR i;octet
S: B123 OK
C: B124 SEARCH OR BODY GIF87A BODY GIF89A
S: * SEARCH 42 69
S: B124 OK
C: B125 COMPARATOR cz;* i;basic*
S: * COMPARATOR i;basic;uca=3.1.1;uv=3.2
S: B125 OK
4.4 COMPARATOR Response 4.4 COMPARATOR Response
Contents: The active comparator. Contents: The active comparator.
An optional list of available matching comparators An optional list of available matching comparators
The COMPARATOR response occurs as a result of a COMPARATOR command. The COMPARATOR response occurs as a result of a COMPARATOR command.
The first argument in the comparator response is the name of the The first argument in the comparator response is the name of the
active comparator. The second argument is a list of comparators active comparator. The second argument is a list of comparators
which matched any of the arguments to the COMPARATOR command and is which matched any of the arguments to the COMPARATOR command and is
present only if more than one match is found. present only if more than one match is found.
4.5 COMPARATOR SEARCH and SORT Key 4.5 Formal Syntax
[NOTE: Unless someone objects strongly and wishes to implement
it, I will drop section 4.5. I have not been able to find a
good, reasonable example for it, and I don't like its
preprocessor-like approach, making "SEARCH <a> <b>" differ from
"SEARCH <b> <a>" if one of <a> or <b> uses COMPARATOR. --Arnt]
The COMPARATOR SEARCH key takes a comparator order argument. That
argument will select the comparator to use for subsequent SEARCH
keys in the search specification. The COMPARATOR SORT key works in
a similar fashion except that it applies to subsequent SORT keys in
the SORT criterion.
If no comparator matches the pattern specified by the COMPARATOR
SEARCH or SORT key, then the SEARCH or SORT command will fail with a
[BADCOMPARATOR] response code. This error code is also returned if
a comparator is found, but it does not support the necessary
function (substring matching for SEARCH, or ordering for SORT).
If an input string provided as part of a SEARCH program causes an
error when used with the selected comparator, the SEARCH command
will fail with a [BADMATCH] response code.
4.6 Formal Syntax
The following syntax specification inherits ABNF [2] rules from The following syntax specification inherits ABNF [2] rules from
IMAP4rev1 [6], and Internet Application Protocol Comparator Registry IMAP4rev1 [6], and Internet Application Protocol Comparator Registry
[8]. [8].
command-auth =/ comparator-cmd command-auth =/ comparator-cmd
search-key =/ comparator-key
Internet-draft May 2004
sort-criterion =/ comparator-key
; this only applies to servers which advertise both
; the COMPARATOR and SORT extensions.
resp-text-code =/ "BADCOMPARATOR" / "BADMATCH" resp-text-code =/ "BADCOMPARATOR" / "BADMATCH"
comparator-cmd = "COMPARATOR" *(SP comp-order-quoted) comparator-cmd = "COMPARATOR" *(SP comp-order-quoted)
comparator-data = "COMPARATOR" SP comp-sel-quoted [SP "(" comparator-data = "COMPARATOR" SP comp-sel-quoted [SP "("
comp-name-quoted *(SP comp-name-quoted) ")"] comp-name-quoted *(SP comp-name-quoted) ")"]
comparator-key = "COMPARATOR" SP comp-order-quoted
comp-name-quoted = astring comp-name-quoted = astring
; Once any literal wrapper or quoting is removed, ; Once any literal wrapper or quoting is removed,
; this follows the comparator-name rule ; this follows the comparator-name rule
Internet-draft June 2004
comp-order-quoted = astring comp-order-quoted = astring
; Once any literal wrapper or quoting is removed, ; Once any literal wrapper or quoting is removed,
; this follows the comparator-order rule ; this follows the comparator-order rule
comp-sel-quoted = astring comp-sel-quoted = astring
; Once any literal wrapper or quoting is removed, ; Once any literal wrapper or quoting is removed,
; this follows the comparator-sel rule ; this follows the comparator-sel rule
5. Other IMAP Internationalization Issues 5. Other IMAP Internationalization Issues
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mechanisms, the potential lack of input methods for non-ASCII text mechanisms, the potential lack of input methods for non-ASCII text
is a serious interoperability concern. However, because of the is a serious interoperability concern. However, because of the
visibility of these fields to end-users, it is expected that visibility of these fields to end-users, it is expected that
pressure to support UTF-8 login names and passwords will eventually pressure to support UTF-8 login names and passwords will eventually
become irresistable. This specification defers such work until the become irresistable. This specification defers such work until the
SASL-related profile of stringprep [12] is published as an RFC, and SASL-related profile of stringprep [12] is published as an RFC, and
the impact on ACLs and email addresses has been assessed. the impact on ACLs and email addresses has been assessed.
The "userid" and "password" fields of the IMAP LOGIN command are The "userid" and "password" fields of the IMAP LOGIN command are
restricted to US-ASCII only until a future standards track RFC restricted to US-ASCII only until a future standards track RFC
Internet-draft May 2004
states otherwise. Servers are encouraged to validate both fields to states otherwise. Servers are encouraged to validate both fields to
make sure they conform to the formal syntax of UTF-8 and to reject make sure they conform to the formal syntax of UTF-8 and to reject
the LOGIN command if that syntax is violated. Servers MAY reject the LOGIN command if that syntax is violated. Servers MAY reject
the use of any 8-bit in the "userid" or "password" field. the use of any 8-bit in the "userid" or "password" field.
5.2 UTF-8 Mailbox Names 5.2 UTF-8 Mailbox Names
The modified UTF-7 mailbox naming convention described in section The modified UTF-7 mailbox naming convention described in section
5.1.3 of RFC 3501 is best viewed as an transition from the status 5.1.3 of RFC 3501 is best viewed as an transition from the status
quo in 1996 when modified UTF-7 was first specified. At that time, quo in 1996 when modified UTF-7 was first specified. At that time,
there was widespread unofficial use of local character sets such as there was widespread unofficial use of local character sets such as
ISO-8859-1 and Shift-JIS for non-ASCII mailbox names, with resultant ISO-8859-1 and Shift-JIS for non-ASCII mailbox names, with resultant
non-interoperability. non-interoperability.
Internet-draft June 2004
The requirements in section 5.1 of RFC 3501 are very important if The requirements in section 5.1 of RFC 3501 are very important if
we're ever going to be able to deploy UTF-8 mailbox names. Servers we're ever going to be able to deploy UTF-8 mailbox names. Servers
are encourated to enforce them. are encourated to enforce them.
5.3 UTF-8 Domains, Addresses and Mail Headers 5.3 UTF-8 Domains, Addresses and Mail Headers
There is now an IETF standard for Internationalizing Domain Names in There is now an IETF standard for Internationalizing Domain Names in
Applications [13]. While IMAP clients are free to support this Applications [13]. While IMAP clients are free to support this
standard and convert punycode [14] to UTF-8 at display time, an standard and convert punycode [14] to UTF-8 at display time, an
argument can be made that it would be helpful to simple clients if argument can be made that it would be helpful to simple clients if
skipping to change at page 13, line 5 skipping to change at page 12, line 37
7. Security Considerations 7. Security Considerations
The LANGUAGE extension makes a new command available in "Not The LANGUAGE extension makes a new command available in "Not
Authenticated" state in IMAP. Some IMAP implementations run with Authenticated" state in IMAP. Some IMAP implementations run with
root privilege when the server is in "Not Authenticated" state and root privilege when the server is in "Not Authenticated" state and
do not revoke that privilege until after authentication is complete. do not revoke that privilege until after authentication is complete.
Such implementations are particularly vulnerable to buffer overflow Such implementations are particularly vulnerable to buffer overflow
security errors at this stage and need to implement parsing of this security errors at this stage and need to implement parsing of this
command with extra care. command with extra care.
Internet-draft May 2004
A LANGUAGE command issued prior to activation of a security layer is A LANGUAGE command issued prior to activation of a security layer is
subject to an active attack which suppresses or modifies the subject to an active attack which suppresses or modifies the
negotiation and thus makes STARTTLS or authentication error messages negotiation and thus makes STARTTLS or authentication error messages
more difficult to interpret. This is not a new attack as the error more difficult to interpret. This is not a new attack as the error
messages themselves are subject to active attack. Clients MUST re- messages themselves are subject to active attack. Clients MUST re-
issue the LANGUAGE command once a security layer is active, so this issue the LANGUAGE command once a security layer is active, so this
does not impact subsequent protocol operations. does not impact subsequent protocol operations.
Both the LANGUAGE and COMPARATOR extensions use the UTF-8 charset, Both the LANGUAGE and COMPARATOR extensions use the UTF-8 charset,
thus the security considerations for UTF-8 [7] are relevent. thus the security considerations for UTF-8 [7] are relevent.
However, neither uses UTF-8 for identifiers so the most serious However, neither uses UTF-8 for identifiers so the most serious
concerns do not apply. concerns do not apply.
Internet-draft June 2004
8. Acknowledgements 8. Acknowledgements
The LANGUAGE extension is based on a previous Internet draft by Mike The LANGUAGE extension is based on a previous Internet draft by Mike
Gahrns and Alexey Melnikov, a substantial portion of the text in Gahrns and Alexey Melnikov, a substantial portion of the text in
that section was written by them. Many people have participated in that section was written by them. Many people have participated in
discussions about an IMAP Language extension in the various fora of discussions about an IMAP Language extension in the various fora of
the IETF and Internet working groups, so any list of contributors is the IETF and Internet working groups, so any list of contributors is
bound to be incomplete. However, the authors would like to thank bound to be incomplete. However, the authors would like to thank
Andrew McCown for early work on the original proposal, John Myers Andrew McCown for early work on the original proposal, John Myers
for suggestions regarding the namespace issue, along with Jutta for suggestions regarding the namespace issue, along with Jutta
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o The 8-bit rules for mailbox naming in section 5.1 of RFC 3501. o The 8-bit rules for mailbox naming in section 5.1 of RFC 3501.
o The Mailbox International Naming Convention in section 5.1.3 of o The Mailbox International Naming Convention in section 5.1.3 of
RFC 3501. RFC 3501.
o MIME [9] for message bodies. o MIME [9] for message bodies.
o MIME header encoding [10] for message headers. o MIME header encoding [10] for message headers.
o MIME Parameter Value and Encoded Word Extensions [11] for o MIME Parameter Value and Encoded Word Extensions [11] for
filenames. Quality IMAP server implementations will filenames. Quality IMAP server implementations will
automatically combine multipart parameters when generating the automatically combine multipart parameters when generating the
BODYSTRUCTURE. There is also some deployed non-standard use of BODYSTRUCTURE. There is also some deployed non-standard use of
MIME header encoding inside double-quotes for filenames. MIME header encoding inside double-quotes for filenames.
Internet-draft May 2004
o IDNA [13] and punycode [14] for domain names (presently only o IDNA [13] and punycode [14] for domain names (presently only
relevant to IMAP clients). relevant to IMAP clients).
o The UTF-8 charset [7]. o The UTF-8 charset [7].
o The IETF policy on Character Sets and Languages [3]. o The IETF policy on Character Sets and Languages [3].
Internet-draft June 2004
Normative References Normative References
[1] Bradner, S., "Key words for use in RFCs to Indicate Requirement [1] Bradner, S., "Key words for use in RFCs to Indicate Requirement
Levels", BCP 14, RFC 2119, March 1997. Levels", BCP 14, RFC 2119, March 1997.
[2] Crocker, D. and P. Overell, "Augmented BNF for Syntax [2] Crocker, D. and P. Overell, "Augmented BNF for Syntax
Specifications: ABNF", RFC 2234, November 1997. Specifications: ABNF", RFC 2234, November 1997.
[3] Alvestrand, H., "IETF Policy on Character Sets and Languages", [3] Alvestrand, H., "IETF Policy on Character Sets and Languages",
BCP 18, RFC 2277, January 1998. BCP 18, RFC 2277, January 1998.
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RFC 2045, November 1996. RFC 2045, November 1996.
[10] Moore, K., "MIME (Multipurpose Internet Mail Extensions) Part [10] Moore, K., "MIME (Multipurpose Internet Mail Extensions) Part
Three: Message Header Extensions for Non-ASCII Text", RFC 2047, Three: Message Header Extensions for Non-ASCII Text", RFC 2047,
November 1996. November 1996.
[11] Freed, N. and K. Moore, "MIME Parameter Value and Encoded Word [11] Freed, N. and K. Moore, "MIME Parameter Value and Encoded Word
Extensions: Character Sets, Languages, and Continuations", RFC Extensions: Character Sets, Languages, and Continuations", RFC
2231, November 1997. 2231, November 1997.
Internet-draft May 2004
[12] Hoffman, P. and M. Blanchet, "Preparation of Internationalized [12] Hoffman, P. and M. Blanchet, "Preparation of Internationalized
Strings ("stringprep")", RFC 3454, December 2002. Strings ("stringprep")", RFC 3454, December 2002.
[13] Faltstrom, P., Hoffman, P. and A. Costello, "Internationalizing [13] Faltstrom, P., Hoffman, P. and A. Costello, "Internationalizing
Domain Names in Applications (IDNA)", RFC 3490, March 2003. Domain Names in Applications (IDNA)", RFC 3490, March 2003.
Internet-draft June 2004
[14] Costello, A., "Punycode: A Bootstring encoding of Unicode for [14] Costello, A., "Punycode: A Bootstring encoding of Unicode for
Internationalized Domain Names in Applications (IDNA)", RFC Internationalized Domain Names in Applications (IDNA)", RFC
3492, March 2003. 3492, March 2003.
[15] Crispin, M. and K. Murchison, "INTERNET MESSAGE ACCESS PROTOCOL [15] Crispin, M. and K. Murchison, "INTERNET MESSAGE ACCESS PROTOCOL
- SORT AND THREAD EXTENSION", draft-ietf-imapext-sort-12 (work - SORT AND THREAD EXTENSION", draft-ietf-imapext-sort-12 (work
in progress), March 2003. in progress), March 2003.
[16] Daboo, C., "IMAP ANNOTATEMORE Extension", draft-daboo-imap- [16] Daboo, C., "IMAP ANNOTATEMORE Extension", draft-daboo-imap-
annotatemore-05 (work in progress), April 2004. annotatemore-05 (work in progress), April 2004.
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Oryx Mail Systems GmbH Oryx Mail Systems GmbH
Joseph-Dollinger-Bogen 14 Joseph-Dollinger-Bogen 14
D-80807 Muenchen D-80807 Muenchen
Germany Germany
Email: arnt@oryx.com Email: arnt@oryx.com
Phone: +49 89 32356-401 Phone: +49 89 32356-401
Fax: +49 89 32356-409 Fax: +49 89 32356-409
Internet-draft May 2004 Internet-draft June 2004
Intellectual Property Statement Intellectual Property Statement
The IETF takes no position regarding the validity or scope of any The IETF takes no position regarding the validity or scope of any
intellectual property or other rights that might be claimed to intellectual property or other rights that might be claimed to
pertain to the implementation or use of the technology described in pertain to the implementation or use of the technology described in
this document or the extent to which any license under such rights this document or the extent to which any license under such rights
might or might not be available; neither does it represent that it might or might not be available; neither does it represent that it
has made any effort to identify any such rights. Information on the has made any effort to identify any such rights. Information on the
IETF's procedures with respect to rights in standards-track and IETF's procedures with respect to rights in standards-track and
skipping to change at page 17, line 5 skipping to change at page 17, line 5
English. English.
The limited permissions granted above are perpetual and will not be The limited permissions granted above are perpetual and will not be
revoked by the Internet Society or its successors or assignees. revoked by the Internet Society or its successors or assignees.
This document and the information contained herein is provided on an This document and the information contained herein is provided on an
"AS IS" basis and THE INTERNET SOCIETY AND THE INTERNET ENGINEERING "AS IS" basis and THE INTERNET SOCIETY AND THE INTERNET ENGINEERING
TASK FORCE DISCLAIMS ALL WARRANTIES, EXPRESS OR IMPLIED, INCLUDING TASK FORCE DISCLAIMS ALL WARRANTIES, EXPRESS OR IMPLIED, INCLUDING
BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE INFORMATION BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE INFORMATION
Internet-draft May 2004 Internet-draft June 2004
HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED WARRANTIES OF HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED WARRANTIES OF
MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE. MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE.
Acknowledgment Acknowledgment
Funding for the RFC Editor function is currently provided by the Funding for the RFC Editor function is currently provided by the
Internet Society. Internet Society.
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