Network Working Group J. Klensin
Internet-Draft October 19, 2003
Expires: April 18, 2004
A Name Munging Protocol
draft-klensin-name-munging-00.txt
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Copyright (C) The Internet Society (2003). All Rights Reserved.
Abstract
As one works on internationalization issues for DNS, email, and other
protocols, it becomes clear that the various encodings and
transformations required, while not intrinsically difficult, can be
an impediment to rapid conversion of applications to international
form and to rapid prototyping of new applications. This document
proposes a new, lightweight, protocol that can be used to make such
conversions, rather than incorporating the needed tables and
algorithms into each application.
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3
2. The Protocol . . . . . . . . . . . . . . . . . . . . . . . . . 3
2.1 Inputs . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3
2.2 Initial List of Encodings . . . . . . . . . . . . . . . . . . 4
2.3 Outputs . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
2.4 Reply codes . . . . . . . . . . . . . . . . . . . . . . . . . 4
3. Examples . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
4. Signed Messages and Business Arrangements . . . . . . . . . . 5
5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 5
6. Security Considerations . . . . . . . . . . . . . . . . . . . 6
7. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 6
Normative References . . . . . . . . . . . . . . . . . . . . . 6
Informative References . . . . . . . . . . . . . . . . . . . . 6
Author's Address . . . . . . . . . . . . . . . . . . . . . . . 7
Intellectual Property and Copyright Statements . . . . . . . . 8
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1. Introduction
A variety of new and upcoming protocols, most, but not all, of them
associated with internationalization, require that data be presented
in, or mapped into, encoding forms that are specialized and largely
unique to the Internet or those protocols. The trend arguably
started with the introduction of quoted-printable into MIME [RFC1341]
and has continued to more recent DNS internationalization work
[RFC3490] and developing errors in internationalization of electronic
mail [I-D.hoffman-imaa]. These encodings are at least complex enough
that testing for interoperability and accuracy is perceived to be
needed. Even though they are not, intrinsically, very hard, the
process of getting the needed code incorporated and tested may be
sufficient to discourage or delay internationalization of some
applications, including those that are built around short scripts.
This document describes a protocol -- designed for use over either
TCP or UDP -- that can be passed short strings for conversion from
one encoding to another. There are various samples, testbeds, and
web pages today that can do some of these conversions, but they are
not general (few of them handle more than one or two conversions),
and they are really not compatible with use in applications
implementation (regardless of whether they can be used in testing or
not). The core code in those samples and tests could presumably be
adapted to support this protocol.
2. The Protocol
The protocol is designed to be as simple as possible, following the
general "send packet containing one line, get another line back"
model used in finger [RFC1288] and whois [RFC0954]. For performance,
it is designed to be used over either UDP or TCP, as meets the needs
of the application. The TCP variation on the above is, obviously,
"open a connection, send a line, remote system sends a line back and
closes the connection". The lines are defined as follows:
2.1 Inputs
The input line consists of
o A source-indication string
o an ASCII space (i.e., an octet containing hex 20)
o A target-indication string
o an ASCII space
o A bit count, expressed as an ASCII numeral
o An ASCII space
o The source
The indication strings are positive integers, registered with IANA
and described in Section 2.2, below. These integers, and the single
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ASCII space character that follows each one and the bit count, are
protocol elements and are not intended to be internationalized.
The source string will be a simple string of bits, of length
specified by the bit count (with the first bit counted as one). While
it will normally be an integral number of octets, some special
encodings may not permit this, so any extra bits are ignored. For
convenience, the bit count may be specified as an ASCII asterisk
("*", an octet containing hex 2A), in which case the server will
examine the string for the first pair of octets containing,
respectively, hex 0D and 0A (the usual CRLF convention) and consider
it to terminate immediately before those characters.
2.2 Initial List of Encodings
As discussed below, IANA is expected to set up a registry of encoding
codes for use in this protocol. That list is initially:
0 Information and debugging option. If 0 appears as the input
indicator, the rest of the input line is ignored and the server
returns a reply code of "000 " followed by a blank-separated list
of the indicator codes it recognizes. If 0 appears as the output
indication, the input is copied to the output, also with a reply
code of 000, and returned.
1 UCS-4
2 Unicode (UCS-2)
3 IDNA Punycode
4 The IMAA encoding scheme described in [I-D.hoffman-imaa]
5 UTF-8
6 ISO 8859-1
7 Unicode written as a blank-separated list of four or more digit
codes, with the codes in ASCII digits
2.3 Outputs
The output consists of
a three-digit (ASCII) reply code (codes listed below)
an ASCII space
a bit count
a string
The bit count and string are as described above, but the "*"
convention will not be used.
2.4 Reply codes
The following reply codes are specified for use in this protocol. If,
for some reason (presumably due to a new version of the protocol on
the server), the three-digit code returned is not listed below, only
the first digit should be examined. A first digit of zero indicates
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that the string returned contains either the original string or a
recoding of it; a first digit of 5 indicates that the recoding failed
and the string is either zero-length or contains an explanation in
ASCII characters.
000 String translated
001 String not translated
500 service not available to you
501 Input encoding type not recognized
502 Output encoding type not recognized
503 Bit count exceeds length of line
504 No translation available, i.e., the server recognizes the input
encoding and the output encoding, but has no mapping between them.
505 Translation failed or input string invalid, e.g., the input
string was not a possible example of the input encoding specified.
3. Examples
... to be supplied...
4. Signed Messages and Business Arrangements
In today's sometimes-hostile Internet environment, two questions
immediately arise about a protocol that is designed to be this
simple. One is how one tells that the returned string is the intended
one, i.e., that it came from the designated server and that some is
taking responsibility for that server's results. The other is how to
get someone to provide this service, especially if it is to be called
from production-scale applications protocols. Either or both
requirements might be satisfied by sending digitally-signed strings.
In the input (business model) case, we might imagine a subscription
service with registered users, with the digital signature used to
authenticate the query as coming from a subscriber and/or authorize
billing. In the output case, we might imagine a family of certified
servers (using a certification process that lies outside this
specification) able to sign the responses with a key the user or
application would trust. Both of these issues, and the protocol
changes that would be required, should be examined in depth before
this protocol is published.
This specification does not cover identification and location of
appropriate servers.
5. IANA Considerations
IANA is requested to assign a port number to this protocol. A
registry of encoding type indicator strings is also required, with a
sequential integer to be assigned to each type of encoding registered
and the list in Section 2.2 used to initialize that registry. IANA
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is requested to accept registrations only with contact information
and a reference that defines the encoding involved, but, since there
is no shortage of integers, checking and evaluation of such requests
is not required except to the degree required to prevent denial of
service attacks on IANA itself.
6. Security Considerations
As mentioned in Section 4, there is an attack on this protocol,
especially in which it is used over UDP, in which a response is sent
to the client application that contains an encoding of a different
string than the one that was submitted. If that string is used
without inspection or review by the client, various bad things might
happen. Signed strings, as discussed above, might protect against
that problem, but only if keys are properly protected and verified.
7. Acknowledgements
The author would like to express appreciation to Patrik Faltstrom and
Leslie Dangle, who made some suggestions at a early formative stage
of this proposal and, in particular, pointed out the desirability of
digitally signing the strings.
Normative References
Informative References
[I-D.hoffman-imaa]
Hoffman, P. and A. Costello, "Internationalizing Mail
Addresses in Applications (IMAA)", draft-hoffman-imaa-02
(work in progress), August 2003.
[RFC0954] Harrenstien, K., Stahl, M. and E. Feinler, "NICNAME/
WHOIS", RFC 954, October 1985.
[RFC1288] Zimmerman, D., "The Finger User Information Protocol", RFC
1288, December 1991.
[RFC1341] Borenstein, N. and N. Freed, "MIME (Multipurpose Internet
Mail Extensions): Mechanisms for Specifying and Describing
the Format of Internet Message Bodies", RFC 1341, June
1992.
[RFC3490] Faltstrom, P., Hoffman, P. and A. Costello,
"Internationalizing Domain Names in Applications (IDNA)",
RFC 3490, March 2003.
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Author's Address
John C Klensin
1770 Massachusetts Ave, #322
Cambridge, MA 02140
USA
Phone: +1 617 491 5735
EMail: john-ietf@jck.com
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