draft-freed-sieve-ihave-01.txt   draft-freed-sieve-ihave-02.txt 
Network Working Group N. Freed Network Working Group N. Freed
Internet-Draft Sun Microsystems Internet-Draft Sun Microsystems
Expires: August 26, 2008 February 23, 2008 Intended status: Standards Track May 25, 2008
Expires: November 26, 2008
Sieve Email Filtering: Ihave Extension Sieve Email Filtering: Ihave Extension
draft-freed-sieve-ihave-01 draft-freed-sieve-ihave-02
Status of this Memo Status of this Memo
By submitting this Internet-Draft, each author represents that any By submitting this Internet-Draft, each author represents that any
applicable patent or other IPR claims of which he or she is aware 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 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. aware will be disclosed, in accordance with Section 6 of BCP 79.
Internet-Drafts are working documents of the Internet Engineering Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF), its areas, and its working groups. Note that Task Force (IETF), its areas, and its working groups. Note that
skipping to change at page 1, line 33 skipping to change at page 1, line 34
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."
The list of current Internet-Drafts can be accessed at The list of current Internet-Drafts can be accessed at
http://www.ietf.org/ietf/1id-abstracts.txt. http://www.ietf.org/ietf/1id-abstracts.txt.
The list of Internet-Draft Shadow Directories can be accessed at The list of Internet-Draft Shadow Directories can be accessed at
http://www.ietf.org/shadow.html. http://www.ietf.org/shadow.html.
This Internet-Draft will expire on August 26, 2008. This Internet-Draft will expire on November 26, 2008.
Abstract Abstract
This document describes the "ihave" extension to the Sieve email This document describes the "ihave" extension to the Sieve email
filtering language. The "ihave" extension provides a means to write filtering language. The "ihave" extension provides a means to write
scripts that can take advantage of optional Sieve features but can scripts that can take advantage of optional Sieve features but can
still run when those optional features are not available. The still run when those optional features are not available. The
extension also defines a new error control command intended to be extension also defines a new error control command intended to be
used to report situations where no combination of available used to report situations where no combination of available
extensions satifies the needs of the script. extensions satisfies the needs of the script.
Change History (to be removed prior to publication as an RFC Change History (to be removed prior to publication as an RFC)
Changed the comparator used in the ihave test from "i;ascii-casemap" Changed the comparator used in the ihave test from "i;ascii-casemap"
to "i;octet". to "i;octet".
Updated the IANA registration template. Updated the IANA registration template.
Simplified the semantics of ihave to be independent of block Simplified the semantics of ihave to be independent of block
structure. structure.
Moved the environment extension to a separate document so the Moved the environment extension to a separate document so the
standards status of the two extensions can be different. standards status of the two extensions can be different.
Added error action. Added error action.
Added some text to make the portability advantages of ihave clearer.
Added a note about the possibility that the argument to error uses
UTF-8 characters.
1. Introduction 1. Introduction
Sieve [RFC5228] is a language for filtering email messages at or Sieve [RFC5228] is a language for filtering email messages at or
around the time of final delivery. It is designed to be around the time of final delivery. It is designed to be
implementable on either a mail client or mail server. It is suitable implementable on either a mail client or mail server. It is suitable
for running on a mail server where users may not be allowed to for running on a mail server where users may not be allowed to
execute arbitrary programs, such as on black box Internet Message execute arbitrary programs, such as on black box Internet Message
Access Protocol [RFC3501] servers, as it has no user-controlled loops Access Protocol [RFC3501] servers, as it has no user-controlled loops
or the ability to run external programs. or the ability to run external programs.
Various sieve extensions have already been defined, e.g., [RFC5229] Various sieve extensions have already been defined, e.g., [RFC5229]
[RFC5230] [RFC5231] [RFC5232] [RFC5233] [RFC5235], and many more are [RFC5230] [RFC5231] [RFC5232] [RFC5233] [RFC5235], and many more are
sure to be created over time. Sieve's require clause is used to sure to be created over time. Sieve's require clause is used to
specify the extensions a particular sieve needs; an error results if specify the extensions a particular sieve needs; an error results if
the script's require clause calls for an extension that isn't the script's require clause calls for an extension that isn't
available. This mechanism is sufficient in most situations. available. This mechanism is sufficient in most situations.
However, there can be cases where a script may be able to take However, there can be cases where a script may be able to take
advantage of an extension if it is available but can still function advantage of an extension if it is available but can still operate if
if it is not, possibly with some degradation of capabilities. Cases it is not, possibly with some degradation of functionality. Cases
can also arise where a script would prefer one extension but can can also arise where a script would prefer one extension but can
employ a different one if the first one is not available. employ a different one if the first one is not available.
The "ihave" extension provides a means to write scripts that make use The "ihave" extension provides a means to write scripts that make use
of extensions only when they are actually available. Ihave defines a of extensions only when they are actually available. Ihave defines a
new ihave test that takes a list of capability names as an argument new ihave test that takes a list of capability names as an argument
and succeeds if and only if all of the those capabilities are and succeeds if and only if all of the those capabilities are
present. Additionally, specification of the "ihave" extension in the present. Additionally, specification of the "ihave" extension in the
require clause disables parse time checking of extension use in require clause disables parse time checking of extension use in
scripts; run-time checking must be used instead. scripts; run-time checking must be used instead. This makes it
possible to write portable scripts that can operate in multiple
environments making effective use of whatever extensions are
available even though differing sets of extensions are provided in
different places.
The "ihave" extension also defines a new error control command. The "ihave" extension also defines a new error control command.
Error causes script execution to terminate with the error message Error causes script execution to terminate with the error message
given as the argument to the error control. given as the argument to the error control.
2. Conventions used in this document 2. 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 RFC 2119 [RFC2119]. document are to be interpreted as described in [RFC2119].
The terms used to describe the various components of the Sieve The terms used to describe the various components of the Sieve
language are taken from [RFC5228] section 1.1. language are taken from Section 1.1 of [RFC5228].
3. Capability Identifiers 3. Capability Identifiers
The capability string associated with the extension defined in this The capability string associated with the extension defined in this
document is "ihave". document is "ihave".
4. Ihave Test 4. Ihave Test
Usage: ihave <capabilities: string-list> Usage: ihave <capabilities: string-list>
skipping to change at page 3, line 48 skipping to change at page 4, line 8
The Sieve base specification demands that that all Sieve extensions The Sieve base specification demands that that all Sieve extensions
used in a given script be specified in the initial require control used in a given script be specified in the initial require control
statement. It is an error for a script to call for extensions the statement. It is an error for a script to call for extensions the
interpreter doesn't support or to attempt to use extensions that have interpreter doesn't support or to attempt to use extensions that have
not been listed in the script's require clause. Using ihave changes not been listed in the script's require clause. Using ihave changes
Sieve interpreter behavior and the underlying requirements in the Sieve interpreter behavior and the underlying requirements in the
following ways: following ways:
1. Use of a given extension is allowed subsequent to the successful 1. Use of a given extension is allowed subsequent to the successful
evaluation of an ihave test on that extension. The extension evaluation of an ihave test on that extension all the way to the
then operates just as if it had been specified in the script's end of the script, even outside the block enclosed by the ihave
require clause. The extension cannot be used prior to the test. In other words, subsequent to a successful ihave things
evaluation of such a test and a runtime error MUST be generated operate just as if the extension had been specified in the
if such usage is attempted. script's require clause. The extension cannot be used prior to
the evaluation of such a test and a runtime error MUST be
generated if such usage is attempted. However, subsequent use of
that extension may still need to be conditionally handled via an
ihave test to deal with the case where it is not supported. The
extension cannot be used prior to the evaluation of such a test
and a runtime error MUST be generated if such usage is attempted.
2. Sieve interpreters normally have the option of checking extension 2. Sieve interpreters normally have the option of checking extension
use at either parse time or execution time. The specification of use at either parse time or execution time. The specification of
"ihave" in a script's require clause changes this behavior: "ihave" in a script's require clause changes this behavior:
Scripts MUST either defer extension checking to run time or else Scripts MUST either defer extension checking to run time or else
take the presence of ihave tests into account at parse time. take the presence of ihave tests into account at parse time.
Note that since ihave can be used inside of anyof, allof, and not Note that since ihave can be used inside of anyof, allof, and not
tests full parse time checking of ihave may be very difficult to tests full parse time checking of ihave may be very difficult to
implement. implement.
skipping to change at page 4, line 41 skipping to change at page 5, line 7
5. Error Control 5. Error Control
Usage: error <message: string> Usage: error <message: string>
The error control causes script execution to terminate with a run- The error control causes script execution to terminate with a run-
time error. The message argument provides a text description of the time error. The message argument provides a text description of the
error condition that SHOULD be included in any generated report error condition that SHOULD be included in any generated report
regarding the error. Section 2.10.6 of [RFC5228] describes how run- regarding the error. Section 2.10.6 of [RFC5228] describes how run-
time errors are handled in Sieve. time errors are handled in Sieve.
Note that the message argument, like all Sieve string, employs the
UTF-8 charset and can contain non-US-ASCII characters. This must be
taken into consideration when reporting script errors.
The error control is included as part of the ihave extension so that The error control is included as part of the ihave extension so that
it is unconditionally available to scripts using ihave. it is unconditionally available to scripts using ihave.
6. Security Considerations 6. Security Considerations
A potential security issue with Sieve scripts is that when a script A potential security issue with Sieve scripts is that when a script
fails to run due to the lack of some extension it may fail to block fails to run due to the lack of some extension it may fail to block
dangerous email. The ihave extension makes it possible to improve dangerous email. The ihave extension makes it possible to improve
script portability and generality, which may improve the overall script portability and generality, which may improve the overall
security provided by Sieve. security provided by Sieve.
skipping to change at page 6, line 16 skipping to change at page 6, line 36
[RFC5232] Melnikov, A., "Sieve Email Filtering: Imap4flags [RFC5232] Melnikov, A., "Sieve Email Filtering: Imap4flags
Extension", RFC 5232, January 2008. Extension", RFC 5232, January 2008.
[RFC5233] Murchison, K., "Sieve Email Filtering: Subaddress [RFC5233] Murchison, K., "Sieve Email Filtering: Subaddress
Extension", RFC 5233, January 2008. Extension", RFC 5233, January 2008.
[RFC5235] Daboo, C., "Sieve Email Filtering: Spamtest and Virustest [RFC5235] Daboo, C., "Sieve Email Filtering: Spamtest and Virustest
Extensions", RFC 5235, January 2008. Extensions", RFC 5235, January 2008.
Appendix A. Acknowledgements
Cyrus Daboo and Alexey Melnikov provided helpful suggestions and
corrections.
Author's Address Author's Address
Ned Freed Ned Freed
Sun Microsystems Sun Microsystems
3401 Centrelake Drive, Suite 410 3401 Centrelake Drive, Suite 410
Ontario, CA 92761-1205 Ontario, CA 92761-1205
USA USA
Phone: +1 909 457 4293 Phone: +1 909 457 4293
Email: ned.freed@mrochek.com Email: ned.freed@mrochek.com
 End of changes. 15 change blocks. 
17 lines changed or deleted 42 lines changed or added

This html diff was produced by rfcdiff 1.35. The latest version is available from http://tools.ietf.org/tools/rfcdiff/