Internet DRAFT - draft-reschke-basicauth-enc
draft-reschke-basicauth-enc
Network Working Group J. Reschke
Internet-Draft greenbytes
Updates: 2617 (if approved) May 8, 2013
Intended status: Experimental
Expires: November 9, 2013
An Encoding Parameter for HTTP Basic Authentication
draft-reschke-basicauth-enc-08
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 the non-ASCII 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 HTTPAUTH Working Group, comments should be sent to
the HTTPAUTH WG's mailing list at http-auth@ietf.org [1], which may
be joined using the form at
<https://www.ietf.org/mailman/listinfo/http-auth>.
Discussions of the HTTPAUTH Working Group are archived at <http://
www.ietf.org/mail-archive/web/http-auth/current/maillist.html>.
XML versions, latest edits and the issues list for this document are
available from
<http://greenbytes.de/tech/webdav/#draft-reschke-basicauth-enc>.
Status of This Memo
This Internet-Draft is submitted in full conformance with the
provisions of BCP 78 and BCP 79.
Internet-Drafts are working documents of the Internet Engineering
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This Internet-Draft will expire on November 9, 2013.
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 4
2. Notational Conventions . . . . . . . . . . . . . . . . . . . . 4
3. The 'accept-charset' auth-param . . . . . . . . . . . . . . . 4
4. Examples . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
5. Security Considerations . . . . . . . . . . . . . . . . . . . 5
6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 5
7. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 5
8. References . . . . . . . . . . . . . . . . . . . . . . . . . . 6
8.1. Normative References . . . . . . . . . . . . . . . . . . . 6
8.2. Informative References . . . . . . . . . . . . . . . . . . 7
Appendix A. Deployment Considerations . . . . . . . . . . . . . . 7
A.1. User Agents . . . . . . . . . . . . . . . . . . . . . . . 7
A.1.1. Alternative approach . . . . . . . . . . . . . . . . . 7
A.2. Origin Servers . . . . . . . . . . . . . . . . . . . . . . 8
Appendix B. FAQ (to be removed by RFC Editor before
publication) . . . . . . . . . . . . . . . . . . . . 8
B.1. Why not simply switch the default encoding to UTF-8? . . . 8
B.2. What about Digest? . . . . . . . . . . . . . . . . . . . . 8
B.3. Will existing UAs ignore the parameter? . . . . . . . . . 8
Appendix C. Change Log (to be removed by RFC Editor before
publication) . . . . . . . . . . . . . . . . . . . . 8
C.1. Since draft-reschke-basicauth-enc-00 . . . . . . . . . . . 8
C.2. Since draft-reschke-basicauth-enc-01 . . . . . . . . . . . 9
C.3. Since draft-reschke-basicauth-enc-02 . . . . . . . . . . . 9
C.4. Since draft-reschke-basicauth-enc-03 . . . . . . . . . . . 9
C.5. Since draft-reschke-basicauth-enc-04 . . . . . . . . . . . 9
C.6. Since draft-reschke-basicauth-enc-05 . . . . . . . . . . . 9
C.7. Since draft-reschke-basicauth-enc-06 . . . . . . . . . . . 9
C.8. Since draft-reschke-basicauth-enc-07 . . . . . . . . . . . 9
Appendix D. Open issues (to be removed by RFC Editor prior to
publication) . . . . . . . . . . . . . . . . . . . . 9
D.1. edit . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
D.2. unorm . . . . . . . . . . . . . . . . . . . . . . . . . . 9
D.3. terminology . . . . . . . . . . . . . . . . . . . . . . . 10
D.4. parmname2831 . . . . . . . . . . . . . . . . . . . . . . . 10
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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], Section 4) 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 the non-
ASCII characters in the ISO-8859-1 character set ([USASCII],
[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 expectation, using a new
auth-param for use in the Proxy-Authenticate and WWW-Authenticate
header fields, as defined in [draft-ietf-httpbis-p7-auth].
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 'accept-charset' auth-param
In challenges, servers MAY use the "accept-charset" authentication
parameter (case-insensitive) to express the character encoding they
expect the user agent to use.
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.
Note: The 'accept-charset' parameter cannot be included when
sending credentials (e.g. in the Authorization or Proxy-
Authorization header fields), as the "Basic" scheme uses a single
token for credentials ('token68' syntax), not a parameter list
('#auth-param' syntax); see Section 2.1 of
[draft-ietf-httpbis-p7-auth].
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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", accept-charset="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.
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], Section 4) yields:
dGVzdDoxMjPCow==
Thus the Authorization header field would be:
Authorization: Basic dGVzdDoxMjPCow==
Or, for proxy authentication:
Proxy-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
<https://bugzilla.mozilla.org/show_bug.cgi?id=41489> and also the
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more recent <https://bugzilla.mozilla.org/show_bug.cgi?id=656213>).
It was Andrew Clover's idea to address it using a new auth-param.
Thanks to Bjoern Hoehrmann, Amos Jeffries, James Manger, and 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.
[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", STD 63, RFC 3629,
November 2003.
[USASCII] American National Standards Institute,
"Coded Character Set -- 7-bit American
Standard Code for Information
Interchange", ANSI X3.4, 1986.
[draft-ietf-httpbis-p7-auth] Fielding, R., Ed. and J. Reschke, Ed.,
"Hypertext Transfer Protocol
(HTTP/1.1): Authentication",
draft-ietf-httpbis-p7-auth-22 (work in
progress), February 2013.
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8.2. Informative References
[RFC4648] Josefsson, S., "The Base16, Base32, and
Base64 Data Encodings", RFC 4648,
October 2006.
[XHR] Aubourg, J., Song, J., and H. Steen,
"XMLHttpRequest", W3C Working Draft WD-
XMLHttpRequest-20121206, December 2012,
<http://www.w3.org/TR/2012/
WD-XMLHttpRequest-20121206/>.
Latest version available at
<http://www.w3.org/TR/XMLHttpRequest/>.
URIs
[1] <mailto:http-auth@ietf.org>
Appendix A. Deployment Considerations
A.1. User Agents
User agents not implementing this specifications should continue to
work as before, ignoring the new parameter.
User agents which already default to the UTF-8 encoding implement
this specification by definition. Note that some user agents also
have different defaults depending on whether the request originates
from page navigation as opposed to a script-driven request using
XMLHttpRequest [XHR].
Other user agents can keep their default behavior, and switch to
UTF-8 when seeing the new parameter.
A.1.1. Alternative approach
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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Note that there's a risk if the site blocks an account after multiple
login failures (for instance, when it doesn't reset the counter after
a successful login).
A.2. Origin Servers
Origin servers that do not support non-ASCII characters in
credentials do not require any changes.
Origin servers that need to support non-ASCII characters, but can't
use the UTF-8 encoding will not be affected; they will continue to
function as well as before.
Finally, origin servers that need to support non-ASCII characters and
can use the UTF-8 encoding can opt in as described above. In the
worst case, they'll continue to see either broken credentials or no
credentials at all (depending on how legacy clients handle characters
they can not encode).
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" as well, any attempt to update this scheme may be an uphill
battle hard to win.
B.3. Will existing UAs ignore the parameter?
It appears they will. See
<http://greenbytes.de/tech/tc/httpauth/#simplebasicnewparam1> and
<http://greenbytes.de/tech/tc/httpauth/#simplebasicnewparam2>.
Appendix C. Change Log (to be removed by RFC Editor before publication)
C.1. Since draft-reschke-basicauth-enc-00
Add and close issues "credparam" and "paramcase". Rewrite the
deployment considerations.
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C.2. Since draft-reschke-basicauth-enc-01
Note more recent Mozilla bugzilla entry; add behavior of existing UAs
to FAQ (with pointer to test cases).
C.3. Since draft-reschke-basicauth-enc-02
Add and resolve issue "xhrutf8".
C.4. Since draft-reschke-basicauth-enc-03
Add and resolve issue "proxy".
C.5. Since draft-reschke-basicauth-enc-04
Add and resolve issues "paramname" and "sentparam". Add issues
"terminology" and "unorm". Update HTTPbis reference.
C.6. Since draft-reschke-basicauth-enc-05
Update HTTPbis reference.
C.7. Since draft-reschke-basicauth-enc-06
Update HTTPbis and XHR references.
C.8. Since draft-reschke-basicauth-enc-07
"b64token" -> "token68" (ABNF term changed in HTTPbis P7). Change
contact information from HTTPbis WG to HTTPAUTH WG. Add issue
parmname2831. Changed intended status to "experimental".
Appendix D. Open issues (to be removed by RFC Editor prior to
publication)
D.1. edit
Type: edit
julian.reschke@greenbytes.de (2010-08-11): Umbrella issue for
editorial fixes/enhancements.
D.2. unorm
Type: edit
julian.reschke@greenbytes.de (2012-02-02): We need a statement about
unicode normalization forms.
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D.3. terminology
Type: edit
julian.reschke@greenbytes.de (2012-02-02): Try to be consistent with
the terminology defined in RFC 6365.
D.4. parmname2831
In Section 3:
Type: change
julian.reschke@greenbytes.de (2012-05-08): RFC 2831 (Digest SASL
Mechanism) defines a *very* similar parameter but calls it "charset".
We may want to be consistent with that.
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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