Network Working Group J. Reschke
Internet-Draft greenbytes
Updates: 2617 (if approved) August 11, 2010
Intended status: Standards Track
Expires: February 12, 2011
An Encoding Parameter for HTTP Basic Authentication
draft-reschke-basicauth-enc-00
Abstract
The "Basic" authentication scheme defined in RFC 2617 does not
properly define how to treat non-ASCII characters. This has lead to
a situation where user agent implementations disagree, and servers
make different assumptions based on the locales they are running in.
There is little interoperability for characters in the ISO-8859-1
character set, and even less interoperability for any characters
beyond that.
This document defines a backwards-compatible extension to "Basic",
specifying the server's character encoding expectation, using a new
authentication scheme parameter.
Editorial Note (To be removed by RFC Editor before publication)
Distribution of this document is unlimited. Although this is not a
work item of the HTTPbis Working Group, comments should be sent to
the Hypertext Transfer Protocol (HTTP) mailing list at
ietf-http-wg@w3.org [1], which may be joined by sending a message
with subject "subscribe" to ietf-http-wg-request@w3.org [2].
Discussions of the HTTPbis Working Group are archived at
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XML versions, latest edits and the issues list for this document are
available from
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3
2. Notational Conventions . . . . . . . . . . . . . . . . . . . . 3
3. The 'encoding' auth-param . . . . . . . . . . . . . . . . . . . 3
4. Examples . . . . . . . . . . . . . . . . . . . . . . . . . . . 3
5. Security Considerations . . . . . . . . . . . . . . . . . . . . 4
6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . . 4
7. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 4
8. References . . . . . . . . . . . . . . . . . . . . . . . . . . 4
8.1. Normative References . . . . . . . . . . . . . . . . . . . 4
8.2. Informative References . . . . . . . . . . . . . . . . . . 5
Appendix A. Deployment Considerations . . . . . . . . . . . . . . 5
A.1. User Agents . . . . . . . . . . . . . . . . . . . . . . . . 5
A.2. Origin Servers . . . . . . . . . . . . . . . . . . . . . . 6
Appendix B. FAQ (to be removed by RFC Editor before
publication) . . . . . . . . . . . . . . . . . . . . . 6
B.1. Why not simply switch the default encoding to UTF-8? . . . 6
B.2. What about Digest? . . . . . . . . . . . . . . . . . . . . 6
B.3. What about a parameter for the credentials? . . . . . . . . 6
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1. Introduction
The "Basic" authentication scheme defined in Section 2 of [RFC2617]
does not properly define how to treat non-ASCII characters
([USASCII]): it uses the Base64 [RFC4648] encoding of the
concatenation of username, separator character, and password without
stating which character encoding to use.
This has lead to a situation where user agent implementations
disagree, and servers make different assumptions based on the locales
they are running in. There is little interoperability for characters
in the ISO-8859-1 character set ([ISO-8859-1]), and even less
interoperability for any characters beyond that.
This document defines a backwards-compatible extension to "Basic",
specifying the server's character encoding expection, using a new
auth-param as defined in Section 1.2 of [RFC2617].
2. Notational Conventions
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
document are to be interpreted as described in [RFC2119].
3. The 'encoding' auth-param
Servers MAY use the "encoding" authentication parameter to express
the character encoding they expect the user agent to use. [[case-
sens: Are parameter names case-sensitive?]] [[also-cred: Should this
also work as a parameter on the credentials? See Appendix B.3.]]
The only allowed value is "UTF-8", to be matched case-insensitively
(see [RFC2978], Section 2.3), indicating that the server expects the
UTF-8 character encoding to be used ([RFC3629]).
Other values are reserved for future use.
4. Examples
In the example below, the server prompts for authentication in the
"foo" realm, using Basic authentication, with a preference for the
UTF-8 character encoding:
WWW-Authenticate: Basic realm="foo", encoding="UTF-8"
Note that the parameter value can be either a token or a quoted
string; in this case the server chose to use the quoted-string
notation.
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The user's name is "test", and his password is the string "123"
followed by the Unicode character U+00A3 (POUND SIGN). Following
Section 1.2 of [RFC2617], but using the character encoding UTF-8, the
user-pass, converted to a sequence of octets, is:
't' 'e' 's' 't' ':' '1' '2' '3' pound
74 65 73 74 3A 31 32 33 C2 A3
Encoding this octet sequence in Base64 ([RFC4648]) yields:
dGVzdDoxMjPCow==
Thus the Authorization header field would be:
Authorization: Basic dGVzdDoxMjPCow==
5. Security Considerations
This document does not introduce any new security considerations
beyond those defined for the "Basic" authentication scheme
([RFC2617], Section 4), and those applicable to the handling of UTF-8
([RFC3629], Section 10).
6. IANA Considerations
There are no IANA Considerations related to this specification.
7. Acknowledgements
The internationalisation problem has been reported as a Mozilla bug
back in the year 2000 (see
). It was Andrew
Clover's idea to address it using a new auth-param.
Thanks to Martin Thomson for providing feedback on this document.
8. References
8.1. Normative References
[ISO-8859-1] International Organization for Standardization,
"Information technology -- 8-bit single-byte coded
graphic character sets -- Part 1: Latin alphabet No.
1", ISO/IEC 8859-1:1998, 1998.
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.
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[RFC2617] Franks, J., Hallam-Baker, P., Hostetler, J., Lawrence,
S., Leach, P., Luotonen, A., and L. Stewart, "HTTP
Authentication: Basic and Digest Access
Authentication", RFC 2617, June 1999.
[RFC2978] Freed, N. and J. Postel, "IANA Charset Registration
Procedures", BCP 19, RFC 2978, October 2000.
[RFC3629] Yergeau, F., "UTF-8, a transformation format of ISO
10646", RFC 3629, STD 63, November 2003.
[USASCII] American National Standards Institute, "Coded Character
Set -- 7-bit American Standard Code for Information
Interchange", ANSI X3.4, 1986.
8.2. Informative References
[RFC4648] Josefsson, S., "The Base16, Base32, and Base64 Data
Encodings", RFC 4648, October 2006.
URIs
[1]
[2]
Appendix A. Deployment Considerations
A.1. User Agents
User agents which already default to UTF-8 do not need to be changed
at all. Other user agents can keep their default behavior, and
switch to UTF-8 when seeing the new parameter.
On the other hand, the strategy below may already improve the user-
visible behavior today:
o In the first authentication request, choose the character encoding
based on the user's credentials: if they do not need any
characters outside the ISO-8859-1 character set, default to ISO-
8859-1, otherwise use UTF-8.
o If the first attempt failed and the encoding used was ISO-8859-1,
retry once with UTF-8 encoding instead.
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A.2. Origin Servers
Origin servers that expect ISO-8859-1 encoding do not require any
changes. Other servers that already expect UTF-8 can add the new
parameter without any risk of breaking existing user agents.
[[testme: We may want to confirm this with test cases.]]
Appendix B. FAQ (to be removed by RFC Editor before publication)
B.1. Why not simply switch the default encoding to UTF-8?
There are sites in use today that default to a locale encoding, such
as ISO-8859-1, and expect user agents to use that encoding. These
sites will break if the user agent uses a different encoding, such as
UTF-8.
B.2. What about Digest?
Although the solution proposed in this document may be applicable to
"Digest" is well, any attempt to update this scheme may be an uphill
battle hard to win.
B.3. What about a parameter for the credentials?
Defining a parameter on the credentials would make it easier for the
server to find out what the client is sending. As far as clients
only send the credentials parameter when the server opted-in through
the challenge, there should be no interop issue.
This sounds like a nice-to-have, but doesn't seem to be really
needed. Feedback appreciated.
Author's Address
Julian F. Reschke
greenbytes GmbH
Hafenweg 16
Muenster, NW 48155
Germany
EMail: julian.reschke@greenbytes.de
URI: http://greenbytes.de/tech/webdav/
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