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Internet Draft A. Melnikov
Document: draft-melnikov-imap-ext-abnf Isode Ltd.
Expires: April 2006 Cyrus Daboo
ISAMET, Inc.
October 2005
Collected extensions to IMAP4 ABNF
draft-melnikov-imap-ext-abnf-05
Status of this Memo
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Abstract
Over years many documents from IMAPEXT and LEMONADE working groups,
as well as many individual documents have added syntactic
extensions to many base IMAP commands described in RFC 3501. For
ease of reference this document collects most of such ABNF changes
in one place.
This document updates ABNF in RFC 3501, RFC 2342 and RFC 2088.
Table of Contents
1. Conventions Used in this Document 2
2. IMAP ABNF extensions 3
2.1 Optional parameters with the SELECT/EXAMINE commands 3
2.2 Extended CREATE command 4
2.3 Extended RENAME command 5
2.4 Extensions to FETCH and UID FETCH Commands 5
2.5 Extensions to STORE and UID STORE Commands 6
2.6 Extensions to SEARCH Command 6
2.7 Extensions to APPEND Command 7
3. Formal Syntax 7
4. Security Considerations 11
5. IANA Considerations 12
6. References 12
6.1 Normative References 12
7. Acknowledgments 12
8. Author's Addresses 12
9. Full Copyright Statement 13
10. Intellectual Property 13
11. Appendix A. Editorial. 14
11.1 Change Log 14
11.2 Open issues 14
1. Conventions Used in this Document
In examples, "C:" and "S:" indicate lines sent by the client and
server respectively.
The key words "MUST", "MUST NOT", "SHOULD", "SHOULD NOT", and "MAY"
in this document are to be interpreted as defined in "Key words for
use in RFCs to Indicate Requirement Levels" [KEYWORDS].
<<Editorial comments and questions are enclosed like this>>
2. IMAP ABNF extensions
This section is not normative. It provides with some background on
intended use of different extensions and it tries to give some
guidance about how future extensions should extend the described
commands.
2.1 Optional parameters with the SELECT/EXAMINE commands
This documents adds the ability to include one or more parameters
with the IMAP SELECT or EXAMINE commands, to turn on or off certain
standard behaviour, or to add new optional behaviours required for
a particular extension.
There are two possible modes of operation:
o A global state change where a single use of the optional
parameter will effect the session state from that time on,
irrespective of subsequent SELECT/EXAMINE commands.
o A per-mailbox state change that will effect the session only for
the duration of the new selected state. A subsequent SELECT/
EXAMINE without the optional parameter will cancel its effect
For the newly selected mailbox.
Optional parameters to the SELECT or EXAMINE commands are added as
a parenthesised list of atoms or strings, and appear after the
mailbox name in the standard SELECT or EXAMINE command. The order
of individual parameters is arbitrary. Individual parameters may
consist of one or more atoms or strings in a specific order. If a
parameter consists of more than one atom or string, it SHOULD
appear in its own parenthesised list. Any parameter not defined by
extensions that the server supports must be rejected with a BAD
response.
Example:
C: a SELECT INBOX (ANNOTATE)
S: ...
S: a OK SELECT complete
In the above example, a single parameter is used with the SELECT
command.
Example:
C: a EXAMINE INBOX (ANNOTATE RESPONSES "UID Responses"
CONDSTORE)
S: ...
S: a OK EXAMINE complete
In the above example, three parameters are used with the EXAMINE
command. The second parameter consists of two items: an atom
followed by a quoted string.
Example:
C: a SELECT INBOX (BLURDYBLOOP)
S: a BAD Unknown parameter in SELECT command
In the above example, a parameter not supported by the server is
used. This results in the BAD response from the
server.
2.2 Extended CREATE command
Arguments: mailbox name
OPTIONAL list of CREATE parameters
Responses: no specific responses for this command
Result: OK - create completed
NO - create failure: can't create mailbox with
that name
BAD - argument(s) invalid
This documents adds the ability to include one or more parameters
with the IMAP CREATE command (see section 6.3.3 of [IMAP4]), to
turn on or off certain standard behaviour, or to add new optional
behaviours required for a particular extension. No CREATE
parameters are defined in this document.
Optional parameters to the CREATE command are added as a
parenthesised list of attribute/value pairs after the mailbox name.
Each value can be either an atom, a string or a list. The order of
individual parameters is arbitrary. Individual parameters may
consist of one or more atoms or strings in a specific order. If a
parameter consists of more than one atom or string, it SHOULD
appear in its own parenthesised list. Any parameter not defined by
extensions that the server supports must be rejected with a BAD
response.
2.3 Extended RENAME command
Arguments: existing mailbox name
new mailbox name
OPTIONAL list of RENAME parameters
Responses: no specific responses for this command
Result: OK - rename completed
NO - rename failure: can't rename mailbox with
that name, can't rename to mailbox with
that name, etc.
BAD - argument(s) invalid
This documents adds the ability to include one or more parameters
with the IMAP RENAME command (see section 6.3.5 of [IMAP4]), to
turn on or off certain standard behaviour, or to add new optional
behaviours required for a particular extension. No RENAME
parameters are defined in this document.
Optional parameters to the RENAME command are added as a
parenthesised list of attribute/value pairs after the new mailbox
name. Each value can be either an atom, a string or a list. The
order of individual parameters is arbitrary. Individual parameters
may consist of one or more atoms or strings in a specific order. If
a parameter consists of more than one atom or string, it SHOULD
appear in its own parenthesised list. Any parameter not defined by
extensions that the server supports must be rejected with a BAD
response.
2.4 Extensions to FETCH and UID FETCH Commands
Arguments: sequence set
message data item names or macro
OPTIONAL fetch modifiers
Responses: untagged responses: FETCH
Result: OK - fetch completed
NO - fetch error: can't fetch that data
BAD - command unknown or arguments invalid
This document extends the syntax of the FETCH and UID FETCH
commands (see section 6.4.5 of [IMAP4]) to include optional FETCH
modifiers. No fetch modifiers are defined in this document.
The order of individual modifiers is arbitrary. An individual
modifier may consist of one or more atoms or strings in a specific
order. If a modifier consists of more than one atom or string, it
SHOULD appear in its own parenthesised list. Any modifiers not
defined by extensions that the server supports must be rejected
with a BAD response.
2.5 Extensions to STORE and UID STORE Commands
Arguments: message set
OPTIONAL store modifiers
message data item name
value for message data item
Responses: untagged responses: FETCH
Result: OK - store completed
NO - store error: can't store that data
BAD - command unknown or arguments invalid
This document extends the syntax of the STORE and UID STORE
commands (see section 6.4.6 of [IMAP4]) to include optional STORE
modifiers. No store modifiers are defined in this document.
The order of individual modifiers is arbitrary. Individual
modifier may consist of one or more atoms or strings in a specific
order. If a modifier consists of more than one atom or string, it
SHOULD appear in its own parenthesised list. Any modifiers not
defined by extensions that the server supports must be rejected
with a BAD response.
2.6 Extensions to SEARCH Command
2.6.1 Extended SEARCH command
Arguments: OPTIONAL result specifier
OPTIONAL [CHARSET] specification
searching criteria (one or more)
Responses: REQUIRED untagged response: SEARCH (*)
Result: OK - search completed
NO - search error: can't search that [CHARSET] or
criteria
BAD - command unknown or arguments invalid
This section updates definition of the SEARCH command described in
section 6.4.4 of [IMAP4].
The SEARCH command is extended to allow for result options. This
document doesn't define any result option.
The order of individual options is arbitrary. Individual options
may optionally contain parameters enclosed in parenthesises. If an
option has parameters, they consist of one or more atoms or strings
in a specific order. Any options not defined by extensions that the
server supports must be rejected with a BAD response.
(*) - An extension to SEARCH command may require another untagged
response, or no untagged response to be returned.
2.6.2 ESEARCH untagged response
Contents: one or more search-return-data pairs
The ESEARCH response SHOULD be sent as a result of an extended
SEARCH or UID SEARCH command specified in section 2.6.1.
The ESEARCH response is immediately followed by an optional search
correlator. If it is missing than the response was not caused by a
particular IMAP command, if it is present than it contains the tag
of the command that caused the response to be returned.
The search correlator is followed by an optional UID indicator. If
this indicator is present, all data in the ESEARCH response is
referring to UIDs, otherwise all returned data is referring to
message numbers.
The rest of the ESEARCH response contains one or more search data
pairs. Each pair starts with unique return item name, followed by a
space and the corresponding data. Search data pairs may be returned
in any order. Unless specified otherwise by an extension, any
return item name SHOULD appear only once in an ESEARCH response.
Example: S: * ESEARCH UID COUNT 5 ALL 4:19,21,28
Example: S: * ESEARCH (TAG "a567") UID COUNT 5 ALL 4:19,21,28
Example: S: * ESEARCH COUNT 5 ALL 1:17,21
2.7 Extensions to APPEND Command
The APPEND command is extended to allow the client to append data
containing NULs by using the <literal8> syntax. The ABNF was
rewritten to allow for easier extensibility by IMAP extensions.
3. Formal Syntax
The following syntax specification uses the Augmented Backus-Naur
Form (ABNF) notation as specified in [ABNF].
Non-terminals referenced but not defined below are as defined by
[IMAP4].
Except as noted otherwise, all alphabetic characters are case-
insensitive. The use of upper or lower case characters to define
token strings is for editorial clarity only. Implementations MUST
accept these strings in a case-insensitive fashion.
append = "APPEND" SP mailbox 1*append-message
;; only a single append-message may appear
;; if MULTIAPPEND [MULTIAPPEND] capability
;; is not present
append-message = append-opts SP append-data
append-ext = <for extension only>
;; This rule exists solely to be augmented by
;; extensions via incremental alternative
;; ("=/") rules. It is strongly recommended
;; that such extensions match a subset of the
;; tagged-ext rule syntax
append-data = literal / literal8
;; IMAP extensions extending append-data
;; should use the tagged-ext syntax,
;; i.e. a mandatory label followed
;; by parameters.
append-opts = [SP flag-list] [SP date-time] *(SP append-ext)
create = "CREATE" SP mailbox
[create-params]
;; Use of INBOX gives a NO error
create-params = SP "(" create-param *( SP create-param) ")"
create-param-name = tagged-ext-label
create-param = create-param-name SP create-param-value
create-param-value= <for extension only>
;; This rule exists solely to be augmented by
;; extensions via incremental alternative
;; ("=/") rules. It is strongly recommended
;; that such extensions match a subset of the
;; tagged-ext-val rule syntax
esearch-response = "ESEARCH" [search-correlator] [SP "UID"]
*(SP search-return-data)
;; Note that SEARCH and ESEARCH responses
;; SHOULD be mutually exclusive,
;; i.e. only one of them should be
;; returned as a result of a command.
examine = "EXAMINE" SP mailbox [select-params]
;; modifies the original IMAP EXAMINE command
;; to accept optional parameters
fetch = "FETCH" SP sequence-set SP ("ALL" / "FULL" /
"FAST" / fetch-att /
"(" fetch-att *(SP fetch-att) ")")
[SP fetch-modifiers]
;; modifies the original IMAP4 FETCH command to
;; accept optional modifiers
fetch-modifiers = "(" fetch-modifier *(SP fetch-modifier) ")"
fetch-modifier = fetch-modifier-name [ SP fetch-modif-params ]
;; Note that the original syntax defined
;; in CONDSTORE was extended to allow
;; for "()"
fetch-modif-params = <for extension only>
;; This rule exists solely to be augmented by
;; extensions via incremental alternative
;; ("=/") rules. It is strongly recommended
;; that such extensions match a subset of the
;; tagged-ext-val rule syntax
fetch-modifier-name = tagged-ext-label
literal8 = "~{" number ["+"] "}" CRLF *OCTET
;; A string that might contain NULs.
;; <number> represents the number of OCTETs
;; in the response string.
;; The "+" is only allowed when both LITERAL+
;; and BINARY are present.
mailbox-data =/ Namespace-Response /
esearch-response
Namespace = nil / "(" 1*Namespace-Descr ")"
Namespace-Command = "NAMESPACE"
Namespace-Descr = "(" string SP
(DQUOTE QUOTED-CHAR DQUOTE / nil)
*(Namespace-Response-Extension) ")"
Namespace-Response-Extension = SP string SP
"(" string *(SP string) ")"
Namespace-Response = "NAMESPACE" SP Namespace
SP Namespace SP Namespace
;; The first Namespace is the Personal Namespace(s)
;; The second Namespace is the Other Users' Namespace(s)
;; The third Namespace is the Shared Namespace(s)
rename = "RENAME" SP mailbox SP mailbox
[rename-params]
;; Use of INBOX as a destination gives
;; a NO error
rename-params = SP "(" rename-param *( SP rename-param) ")"
rename-param = rename-param-name SP rename-param-value
rename-param-name = tagged-ext-label
rename-param-value= <for extension only>
;; This rule exists solely to be augmented by
;; extensions via incremental alternative
;; ("=/") rules. It is strongly recommended
;; that such extensions match a subset of the
;; tagged-ext-val rule syntax
response-data = "*" SP response-payload CRLF
response-payload= resp-cond-state / resp-cond-bye /
mailbox-data / message-data / capability-data
search = "SEARCH" [search-return-opts]
search-program
search-correlator = SP "(" "TAG" SP tag-string ")"
search-program = [SP "CHARSET" SP astring] 1*(SP search-key)
;; CHARSET argument to SEARCH MUST be
;; registered with IANA
search-return-data = search-modifier-name SP search-return-value
;; Note that not every SEARCH return option
;; is required to have the corresponding
;; ESEARCH return data
search-return-opts = "RETURN" SP "(" [search-return-opt
*(SP search-return-opt)] ")"
search-return-opt = search-modifier-name [SP search-mod-params]
search-return-value= tagged-ext-val
;; data for the returned search option.
;; A single "nz-number"/"number" value
;; can be returned as an atom (i.e. without
;; quoting). A sequence-set can be returned
;; as an atom as well.
search-modifier-name = tagged-ext-label
search-mod-params = <for extension only>
;; This rule exists solely to be augmented by
;; extensions via incremental alternative
;; ("=/") rules. It is strongly recommended
;; that such extensions match a subset of the
;; tagged-ext-val rule syntax
select = "SELECT" SP mailbox [select-params]
;; modifies the original IMAP SELECT command to
;; accept optional parameters
select-params = SP "(" select-param *(SP select-param) ")"
select-param = select-param-name SP select-param-value
;; parameters to SELECT may contain one or
;; more atoms or strings - multiple items
;; are always parenthesised
select-param-name= tagged-ext-label
select-param-value= <for extension only>
;; This rule exists solely to be augmented by
;; extensions via incremental alternative
;; ("=/") rules. It is strongly recommended
;; that such extensions match a subset of the
;; tagged-ext-val rule syntax
status-att-list = status-att-val *(SP status-att-val)
;; Redefines status-att-list from RFC 3501.
;; status-att-val is defined in RFC 3501 errata
status-att-val = ("MESSAGES" SP number) /
("RECENT" SP number) /
("UIDNEXT" SP nz-number) /
("UIDVALIDITY" SP nz-number) /
("UNSEEN" SP number)
;; Extensions to the STATUS responses
;; should extend this production.
;; Extensions should use the generic
;; syntax defined by tagged-ext.
store = "STORE" SP sequence-set store-modifiers
SP store-att-flags
;; extend [IMAP4] STORE command syntax
;; to allow for optional store-modifiers
store-modifiers = [ SP "(" store-modifier *(SP store-modifier)
")" ]
store-modifier = store-modifier-name [SP store-modif-params]
store-modif-params = <for extension only>
;; This rule exists solely to be augmented by
;; extensions via incremental alternative
;; ("=/") rules. It is strongly recommended
;; that such extensions match a subset of the
;; tagged-ext-val rule syntax
store-modifier-name = tagged-ext-label
tag-string = string
;; tag of the command that caused
;; the ESEARCH response, sent as
;; a string.
tagged-ext = tagged-ext-label SP tagged-ext-val
;; recommended overarching syntax for
;; extensions
tagged-ext-label = atom
;; <<or should this be astring?>>
tagged-ext-comp = astring /
tagged-ext-comp *(SP tagged-ext-comp) /
"(" tagged-ext-comp ")"
;; extensions that follow this general
;; syntax should use nstring instead of
;; astring when appropriate in the context
;; of the extension
tagged-ext-val = astring / "(" [tagged-ext-comp] ")"
4. Security Considerations
It is believed that this document doesn't add any new security
concerns that were not already identified in RFC 3501.
5. IANA Considerations
This document doesn't define any new IMAP extension, so no action
from IANA is required.
6. References
6.1 Normative References
[KEYWORDS] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", RFC 2119, March 1997.
[IMAP4] Crispin, M., "Internet Message Access Protocol - Version
4rev1", RFC 3501, University of Washington, March 2003.
[ABNF] Crocker, D. (Ed.) and P. Overell , "Augmented BNF for Syntax
Specifications: ABNF", RFC 2234, November 1997.<<Needs updating to
draft-crocker-abnf-rfc2234bis-00>>
[CHARSET] Freed, N. and J. Postel, "IANA Character Set Registration
Procedures", RFC 2978, October 2000.
[MULTIAPPEND] Crispin, M., "Internet Message Access Protocol
(IMAP) - MULTIAPPEND Extension", RFC 3502, March 2003.
[NAMESPACE] Gahrns, M. and C. Newman, "IMAP4 Namespace", RFC 2342,
May 1998.
[LITERAL+] Myers, J., "IMAP4 non-synchronizing literals", RFC 2088,
January 1997.
7. Acknowledgments
This documents is based on ideas proposed by Pete Resnick, Mark
Crispin, Ken Murchison, Philip Guenther, Randall Gellens and Lyndon
Nerenberg.
However all errors and omissions must be attributed to the authors
of the document.
literal8 syntax was taken from RFC 3516.
8. Author's Addresses
Alexey Melnikov
Isode Limited
5 Castle Business Village
36 Station Road
Hampton, Middlesex, TW12 2BX
UK
Email: Alexey.Melnikov@isode.com
Cyrus Daboo
ISAMET, Inc.
5001 Baum Blvd.
Suite 650
Pittsburgh, PA 15213
US
EMail: cyrus@daboo.name
9. Full Copyright Statement
Copyright (C) The Internet Society (2005).
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 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.
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.
Acknowledgement
Funding for the RFC Editor function is currently provided by the
Internet Society.
11. Appendix A. Editorial.
<<Note that this section will be deleted before publication>>
11.1 Change Log
00 Initial Revision.
01 Added Cyrus as co-author. Added BINARY literals. Added section
about APPEND. Clarified that the order of all parameters/modifiers is
arbitrary. Unrecognized SELECT/EXAMINE parameter should cause the BAD,
not the NO response.
02 Updated boilerplate. Extended SEARCH modifiers to be consistent
with STORE modifiers. Rewrote FETCH modifier syntax for consistency.
03 Updated as per comments from Philip (ABNF suggestions, in
particular addition of response-data; normative language).
Incorporated RFC 3501 ABNF errata from Mark. Added extensions to
CREATE and RENAME commands. Updated ABNF to use consistent grammer for
all extension elements (this changed ABNF for SELECT/EXAMINE and
FETCH).
04 Added ESEARCH response. Added search-program from IMAP URL.
Removed the partition parameter from CREATE/RENAME. Added NAMESPACE
command/response.
05 Added non-synchronizing literals (RFC 2088). Clarified generic
syntax for STATUS responses.
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