Network Working Group Ken Murchison
Document: draft-murchison-sieve-regex-01.txt Oceana Matrix Ltd.
Expires September 15, 2000 10 March 2000
Sieve -- Regular Expression Extension
Status of this Memo
This document is an Internet-Draft and is in full conformance with
all provisions of Section 10 of RFC2026. Internet-Drafts are working
documents of the Internet Engineering Task Force (IETF), its areas,
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To view the list Internet-Draft Shadow Directories, see
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Distribution of this memo is unlimited.
Copyright Notice
Copyright (C) The Internet Society 2000. All Rights Reserved.
Abstract
In some cases, it is desirable to have a string matching mechanism
which is more powerful than a simple exact match, a substring match
or a glob-style wildcard match. The regular expression matching
mechanism defined in this draft should allow users to isolate just
about any string or address in a message header or envelope.
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Table of Contents
Status of this Memo . . . . . . . . . . . . . . . . . . . . . . . . 1
Copyright Notice . . . . . . . . . . . . . . . . . . . . . . . . . . 1
Abstract . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1
0. Meta-information on this draft . . . . . . . . . . . . . . . 3
0.1. Discussion . . . . . . . . . . . . . . . . . . . . . . . . . 3
0.2. Changes since revision 00 . . . . . . . . . . . . . . . . . . 3
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3
2. Capability Identifier . . . . . . . . . . . . . . . . . . . . 3
3. Regex Match Type . . . . . . . . . . . . . . . . . . . . . . 4
4. Security Considerations . . . . . . . . . . . . . . . . . . . 6
5. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 6
6. Author's Address . . . . . . . . . . . . . . . . . . . . . . 6
Appendix A. References . . . . . . . . . . . . . . . . . . . . . . 6
Appendix B. Full Copyright Statement . . . . . . . . . . . . . . . 6
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0. Meta-information on this draft
This information is intended to facilitate discussion. It will be
removed when this document leaves the Internet-Draft stage.
0.1. Discussion
This draft is intended to be an extension to the Sieve mail filtering
language, available from the Internet-Drafts repository as
<ftp://ftp.ietf.org/internet-drafts/draft-showalter-sieve-09.txt>
(where 09 is the version number, which is actually currently 09).
This draft and the Sieve language itself are being discussed on the
MTA Filters mailing list at <ietf-mta-filters@imc.org>. Subscription
requests can be sent to <ietf-mta-filters-request@imc.org> (send an
email message with the word "subscribe" in the body). More
information on the mailing list along with a WWW archive of back
messages is available at <http://www.imc.org/ietf-mta-filters/>.
0.2. Changes since revision 00
Added POSIX.2 ERE summary.
Added examples.
Editorial changes.
1. Introduction
This is an extension to the Sieve language defined by [SIEVE] for
comparing strings to regular expressions.
Conventions for notations are as in [SIEVE] section 1.1, including
use of [KEYWORDS].
2. Capability Identifier
The capability string associated with the extension defined in this
document is "regex".
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3. Regex Match Type
Commands that support matching may take the optional tagged argument
":regex" to specify that a regular expression match should be
performed. The ":regex" match type is subject to the same rules and
restrictions as the standard match types defined in [SIEVE].
The ":regex" match type is compatible with both the "i;octet" and
"i;ascii-casemap" comparators and may be used with them.
Implementations MUST support extended regular expressions (EREs) as
defined by [POSIX.2]. Any regular expression not defined by
[POSIX.2], including [POSIX.2] basic regular expressions, word
boundaries and backreferences are not supported by this extension.
The following table provides a brief summary of the regular
expressions that MUST be supported. This table is presented here
only as a guideline. [POSIX.2] should be used as the definitive
reference.
NOTE: A double-backslash is needed to escape a special character, as
per section 2.4.2 of [SIEVE].
+------------+-----------------------------------------------------+
| Expression | Pattern |
+------------+-----------------------------------------------------+
| Items to match a single character |
+------------+-----------------------------------------------------+
| . | Match any single character except newline. |
| [ ] | Bracket expression. Match any one of the enclosed |
| | characters. A hypen (-) indicates a range of |
| | consecutive characters. |
| [^ ] | Negated bracket expression. Match any one |
| | character NOT in the enclosed list. A hypen (-) |
| | indicates a range of consecutive characters. |
| \\ | Escape the following special character (match |
| | the literal character). |
+------------+-----------------------------------------------------+
| Items to be used within a bracket expression (localization) |
+------------+-----------------------------------------------------+
| [: :] | Character class (alnum, alpha, blank, cntrl, |
| | digit, graph, lower, print, punct, space, |
| | upper, xdigit). |
| [= =] | Character equivalents. |
| [. .] | Collating sequence. |
+------------+-----------------------------------------------------+
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+------------+-----------------------------------------------------+
| Expression | Pattern |
+------------+-----------------------------------------------------+
| Quantifiers - Items to count the preceding regular expression |
+------------+-----------------------------------------------------+
| ? | Match zero or one instances. |
| * | Match zero or more instances. |
| + | Match one or more instances. |
| {n,m} | Match any number of instances between |
| | n and m (inclusive). {n} matches exactly n |
| | instances. {n,} matches n or more instances. |
+------------+-----------------------------------------------------+
| Anchoring - Items to match positions |
+------------+-----------------------------------------------------+
| ^ | Match the beginning of the line or string. |
| $ | Match the end of the line or string. |
+------------+-----------------------------------------------------+
| Other constructs |
+------------+-----------------------------------------------------+
| | | Alternation. Match either of the separated |
| | regular expressions. |
| ( ) | Group the enclosed regular expression(s). |
+------------+-----------------------------------------------------+
Example:
require "regex";
# Try to catch unsolicited email.
if anyof (
# if a message is not to me (with optional +detail),
not address :regex ["to", "cc", "bcc"]
"me(\\+.*)?@company.com",
# or the subject contains 2 or more dollar signs,
header :regex "subject" "\\$\\$+",
# or the subject is all uppercase (no lowercase)
header :regex :comparator "i;octet" "subject"
"^[^:lower:]*$" ) {
discard; # junk it
}
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4. Security Considerations
Security considerations are discussed in [SIEVE]. It is believed
that this extension doesn't introduce any additional security
concerns.
5. Acknowledgments
Thanks to Tim Showalter and Alexey Melnikov for help with this
document.
6. Author's Address
Ken Murchison
Oceana Matrix Ltd.
21 Princeton Place
Orchard Park, NY 14127
Phone: (716) 662-8973
EMail: ken@oceana.com
Appendix A. References
[KEYWORDS] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", Harvard University, RFC 2119, March, 1997.
[SIEVE] Showalter, T., "Sieve: A Mail Filtering Language", Mira-
point, Inc., Work In Progress.
[POSIX.2], "Portable Operating System Interface (POSIX). Part 2,
Shell and utilities", National Institute of Standards and Tech-
nology (U.S.).
Appendix B. Full Copyright Statement
Copyright (C) The Internet Society 2000. All Rights Reserved.
This document and translations of it may be copied and furnished to
others, and derivative works that comment on or otherwise explain it
or assist in its implementation may be prepared, copied, published
and distributed, in whole or in part, without restriction of any
kind, provided that the above copyright notice and this paragraph
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are included on all such copies and derivative works. However, this
document itself may not be modified in any way, such as by removing
the copyright notice or references to the Internet Society or other
Internet organizations, except as needed for the purpose of develop-
ing Internet standards in which case the procedures for copyrights
defined in the Internet Standards process must be followed, or as
required to translate it into languages other than English.
The limited permissions granted above are perpetual and will not be
revoked by the Internet Society or its successors or assigns.
This document and the information contained herein is provided on an
"AS IS" basis and THE INTERNET SOCIETY AND THE INTERNET ENGINEERING
TASK FORCE DISCLAIMS 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.
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