wdiff rfc7617.original rfc7617.txt

HTTPAuth Working Group
Internet Engineering Task Force (IETF) J. Reschke
Internet-Draft
Request for Comments: 7617 greenbytes
Obsoletes: 2617 (if approved) February 28, September 2015
Intended status:
Category: Standards Track
Expires: September 1, 2015
ISSN: 2070-1721

The 'Basic' HTTP Authentication Scheme
draft-ietf-httpauth-basicauth-update-07

Abstract

This document defines the "Basic" Hypertext Transfer Protocol (HTTP)
Authentication Scheme,
authentication scheme, which transmits credentials as user-id/
password pairs, encoded using Base64.

Editorial Note (To be removed by RFC Editor before publication)

Discussion of this draft takes place on the HTTPAuth working group
mailing list (http-auth@ietf.org), which is 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-ietf-httpauth-basicauth-update>.

The changes in this draft are summarized in Appendix C.8.

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 an Internet Standards Track document.

This document is a product of the Internet Engineering Task Force
(IETF). Note that other groups may also distribute
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Internet-Drafts are draft documents valid the IETF community. It has
received public review and has been approved for a maximum publication by the
Internet Engineering Steering Group (IESG). Further information on
Internet Standards is available in Section 2 of RFC 5741.

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This Internet-Draft will expire on September 1, 2015.
http://www.rfc-editor.org/info/rfc7617.

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Table of Contents

1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 4 3
1.1. Terminology and Notation . . . . . . . . . . . . . . . . . 4 3
2. The 'Basic' Authentication Scheme . . . . . . . . . . . . . . 4 3
2.1. The 'charset' auth-param . . . . . . . . . . . . . . . . . 6 5
2.2. Re-using Reusing Credentials . . . . . . . . . . . . . . . . . . . 8 7
3. Internationalization Considerations . . . . . . . . . . . . . 8
4. Security Considerations . . . . . . . . . . . . . . . . . . . 9 8
5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 10 9
6. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 10
7. References . . . . . . . . . . . . . . . . . . . . . . . . . . 11
7.1. 10
6.1. Normative References . . . . . . . . . . . . . . . . . . . 11
7.2. 10
6.2. Informative References . . . . . . . . . . . . . . . . . . 12 11
Appendix A. Changes from RFC 2617 . . . . . . . . . . . . . . . . 13
Appendix B. Deployment Considerations for the 'charset'
Parameter . . . . . . . . . . . . . . . . . . . . . . 13
B.1. User Agents . . . . . . . . . . . . . . . . . . . . . . . 13
B.2. Servers . . . . . . . . . . . . . . . . . . . . . . . . . 13
B.3. Why not simply switch the default encoding to UTF-8? . . . 14
Appendix C. Change Log (to be removed by RFC Editor before
publication) . . . . . . . . . . . . . . . . . . . . 14
C.1. Since RFC 2617 . . . .
Acknowledgements . . . . . . . . . . . . . . . . . . 14
C.2. Since draft-ietf-httpauth-basicauth-update-00 . . . . . . 14
C.3. Since draft-ietf-httpauth-basicauth-update-01 . . . . . . 15
C.4. Since draft-ietf-httpauth-basicauth-update-02 . . . . . . 15
C.5. Since draft-ietf-httpauth-basicauth-update-03
Author's Address . . . . . . 15
C.6. Since draft-ietf-httpauth-basicauth-update-04 . . . . . . 15
C.7. Since draft-ietf-httpauth-basicauth-update-05 . . . . . . 15
C.8. Since draft-ietf-httpauth-basicauth-update-06 . . . . . . 15

1. Introduction

This document defines the "Basic" Hypertext Transfer Protocol (HTTP)
Authentication Scheme,
authentication scheme, which transmits credentials as user-id/
password pairs, encoded using Base64 (HTTP authentication schemes are
defined in [RFC7235]).

This scheme is not considered to be a secure method of user
authentication unless used in conjunction with some external secure
system such as TLS (Transport Layer Security, [RFC5246]), as the
user-id and password are passed over the network as cleartext.

The "Basic" scheme previously was defined in Section 2 of [RFC2617].
This document updates the definition, and also addresses
internationalization issues by introducing the "charset" 'charset'
authentication parameter (Section 2.1).

Other documents updating RFC 2617 are "Hypertext Transfer Protocol
(HTTP/1.1): Authentication" ([RFC7235], defining the authentication
framework), "HTTP Digest Access Authentication" ([DIGEST], ([RFC7616], updating
the definition of the "Digest" authentication scheme), and "The
Hypertext Transfer Protocol (HTTP) "HTTP
Authentication-Info and Proxy-
Authentication-Info Proxy-Authentication-Info Response Header
Fields" ([AUTHINFO]). ([RFC7615]). Taken together, these four documents obsolete
RFC 2617.

1.1. Terminology and Notation

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].

The terms protection space "protection space" and realm "realm" are defined in Section 2.2
of [RFC7235].

The terms (character) repertoire "(character) repertoire" and character "character encoding scheme scheme"
are defined in Section 2 of [RFC6365].

2. The 'Basic' Authentication Scheme

The "Basic" Basic authentication scheme is based on the model that the client
needs to authenticate itself with a user-id and a password for each
protection space ("realm"). The realm value is a free-form string which
that can only be compared for equality with other realms on that
server. The server will service the request only if it can validate
the user-id and password for the protection space applying to the
requested resource.

The "Basic" Basic authentication scheme utilizes the Authentication Framework
as follows: follows.

In challenges:

o the The scheme name is "Basic" "Basic".

o the The authentication parameter "realm" 'realm' is REQUIRED ([RFC7235],
Section 2.2) 2.2).

o the The authentication parameter "charset" 'charset' is OPTIONAL (see
Section 2.1) 2.1).

o no No other authentication parameters are defined -- unknown
parameters MUST be ignored by recipients, and new parameters can
only be defined by revising this specification specification.

See also Section 4.1 of [RFC7235] [RFC7235], which discusses the complexity of
parsing challenges properly.

Note that both scheme and parameter names are matched case-
insensitively.

For credentials, the "token68" syntax defined in Section 2.1 of
[RFC7235] is used. The value is computed based on user-id and
password as defined below.

Upon receipt of a request for a URI within the protection space that
lacks credentials, the server can reply with a challenge using the
401 (Unauthorized) status code ([RFC7235], Section 3.1) and the WWW-
Authenticate
WWW-Authenticate header field ([RFC7235], Section 4.1).

For instance:

HTTP/1.1 401 Unauthorized
Date: Mon, 04 Feb 2014 16:50:53 GMT
WWW-Authenticate: Basic realm="WallyWorld"

...where

where "WallyWorld" is the string assigned by the server to identify
the protection space.

A proxy can respond with a similar challenge using the 407 (Proxy
Authentication Required) status code ([RFC7235], Section 3.2) and the
Proxy-Authenticate header field ([RFC7235], Section 4.3).

To receive authorization, the client

1. obtains the user-id and password from the user,

2. constructs the user-pass by concatenating the user-id, a single
colon (":") character, and the password,

3. encodes the user-pass into an octet sequence (see below for a
discussion of character encoding schemes),

4. and obtains the basic-credentials by encoding this octet sequence
using base64 Base64 ([RFC4648], Section 4) into a sequence of US-ASCII
characters ([RFC0020]).

The original definition of this authentication scheme failed to
specify the character encoding scheme used to convert the user-pass
into an octet sequence. In practice, most implementations chose
either a locale-specific encoding such as ISO-8859-1 ([ISO-8859-1]),
or UTF-8 ([RFC3629]). For backwards compatibility reasons, this
specification continues to leave the default encoding undefined, as
long as it is compatible with US-ASCII (mapping any US-ASCII
character to a single octet matching the US-ASCII character code).

The user-id and password MUST NOT contain any control characters (see
"CTL" in Appendix B.1 of [RFC5234]).

Furthermore, a user-id containing a colon character is invalid, as
the first colon in a user-pass string separates user-id and password
from one another; text after the first colon is part of the password.
User-ids containing colons cannot be encoded in user-pass strings.

Note that many user agents produce user-pass strings without checking
that user-ids supplied by users do not contain colons; recipients
will then treat part of the username input as part of the password.

If the user agent wishes to send the user-id "Aladdin" and password
"open sesame", it would use the following header field:

Authorization: Basic QWxhZGRpbjpvcGVuIHNlc2FtZQ==

2.1. The 'charset' auth-param

In challenges, servers can use the "charset" 'charset' authentication parameter
to indicate the character encoding scheme they expect the user agent
to use when generating "user-pass" (a sequence of octets). This
information is purely advisory.

The only allowed value is "UTF-8", "UTF-8"; it is to be matched case-insensitively case-
insensitively (see [RFC2978], Section 2.3). It indicates that the
server expects character data to be converted to Unicode
Normalization Form C
("NFC", ("NFC"; see Section 3 of [RFC5198]) and to be
encoded into octets using the UTF-8 character encoding scheme
([RFC3629]).

For the user-id, recipients MUST support all characters defined in
the "UsernameCasePreserved" profile defined in in Section 3.3 of
[PRECIS],
[RFC7613], with the exception of the colon (":") character.

For the password, recipients MUST support all characters defined in
the "OpaqueString" profile defined in in Section 4.2 of [PRECIS]. [RFC7613].

Other values are reserved for future use.

Note: The 'charset' is only defined on challenges, as "Basic" Basic
authentication uses a single token for credentials ('token68'
syntax); thus thus, the credentials syntax isn't extensible.

Note: The name 'charset' has been chosen for consistency with
Section 2.1.1 of [RFC2831]. A better name would have been
'accept-charset', as it is not about the message it appears in,
but the server's expectation.

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 scheme:

WWW-Authenticate: Basic realm="foo", charset="UTF-8"

Note that the parameter value can be either a token or a quoted
string; in this case case, the server chose to use the quoted-string
notation.

The user's name is "test", and the password is the string "123"
followed by the Unicode character U+00A3 (POUND SIGN). Using the
character encoding scheme UTF-8, the user-pass becomes:

'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
Thus, the Authorization header field would be:

Authorization: Basic dGVzdDoxMjPCow==

Or, for proxy authentication:

Proxy-Authorization: Basic dGVzdDoxMjPCow==

2.2. Re-using Reusing Credentials

Given the absolute URI ([RFC3986], Section 4.3) of an authenticated
request, the authentication scope of that request is obtained by
removing all characters after the last slash ("/") character of the
path component ("hier_part", ("hier_part"; see [RFC3986], Section 3). A client
SHOULD assume that resources identified by URIs with a prefix-match
of the authentication scope are also within the protection space
specified by the realm value of that authenticated request.

A client MAY preemptively send the corresponding Authorization header
field with requests for resources in that space without receipt of
another challenge from the server. Similarly, when a client sends a
request to a proxy, it MAY reuse a user-id and password in the Proxy-
Authorization header field without receiving another challenge from
the proxy server.

For example, given an authenticated request to:

http://example.com/docs/index.html

...requests

requests to the URIs below could use the known credentials:

http://example.com/docs/
http://example.com/docs/test.doc
http://example.com/docs/?page=1

...while

while the URIs

http://example.com/other/
https://example.com/docs/

would be considered to be outside the authentication scope.

Note that a URI can be part of multiple authentication scopes (such
as "http://example.com/" and "http://example.com/docs/"). This
specification does not define which of these should be treated with
higher priority.

3. Internationalization Considerations

User-ids or passwords containing characters outside the US-ASCII
character repertoire will cause interoperability issues, unless both
communication partners agree on what character encoding scheme is to
be used. Servers can use the new 'charset' parameter (Section 2.1)
to indicate a preference of "UTF-8", increasing the probability that
clients will switch to that encoding.

The "realm" 'realm' parameter carries data that can be considered textual,
however textual;
however, [RFC7235] does not define a way to reliably transport non-US-
ASCII non-
US-ASCII characters. This is a known issue that would need to be
addressed in a revision to that specification.

4. Security Considerations

The Basic authentication scheme is not a secure method of user
authentication, nor does it in any way protect the entity, which is
transmitted in cleartext across the physical network used as the
carrier. HTTP does not prevent the addition of enhancements (such as
schemes to use one-time passwords) to Basic authentication.

The most serious flaw in of Basic authentication is that it results in
the cleartext transmission of the user's password over the physical
network. Many other authentication schemes address this problem.

Because Basic authentication involves the cleartext transmission of
passwords
passwords, it SHOULD NOT be used (without enhancements such as HTTPS
[RFC2818]) to protect sensitive or valuable information.

A common use of Basic authentication is for identification purposes
-- requiring the user to provide a user-id and password as a means of
identification, for example, for purposes of gathering accurate usage
statistics on a server. When used in this way it is tempting to
think that there is no danger in its use if illicit access to the
protected documents is not a major concern. This is only correct if
the server issues both user-id and password to the users and and, in
particular
particular, does not allow the user to choose his or her own
password. The danger arises because naive users frequently reuse a
single password to avoid the task of maintaining multiple passwords.

If a server permits users to select their own passwords, then the
threat is not only unauthorized access to documents on the server but
also unauthorized access to any other resources on other systems that
the user protects with the same password. Furthermore, in the
server's password database, many of the passwords may also be users'
passwords for other sites. The owner or administrator of such a
system could therefore expose all users of the system to the risk of
unauthorized access to all those other sites if this information is
not maintained in a secure fashion. This raises both security and
privacy concerns ([RFC6973]). If the same user-id and password
combination is in use to access other accounts, such as an email or
health portal account, personal information could be exposed.

Basic authentication is also vulnerable to spoofing by counterfeit
servers. If a user can be led to believe that she is connecting to a
host containing information protected by Basic authentication when,
in fact, she is connecting to a hostile server or gateway, then the
attacker can request a password, store it for later use, and feign an
error. Server implementers ought to guard against this sort of
counterfeiting; in particular, software components which that can take over
control over the message framing on an existing connection (for
instance, "NPH" ("non parsing of headers") scripts) need to be
used carefully or not at all. all (for instance: NPH ("Non-Parsed Header")
scripts as described in Section 5 of [RFC3875]).

Servers and proxies implementing Basic Authentication authentication need to store
user passwords in some form in order to authenticate a request.
These passwords ought to be be stored in such a way that a leak of the
password data doesn't make them trivially recoverable. This is
especially important when users are allowed to set their own
passwords, since users are known to choose weak passwords and to
reuse them across authentication realms. While a full discussion of
good password hashing techniques is beyond the scope of this
document, server operators ought to make an effort to minimize risks
to their users in the event of a password data leak. For example,
servers ought to avoid storing user passwords in plaintext or as
unsalted digests. For more discussion about modern password hashing
techniques, see the "Password Hashing Competition"
(<https://password-hashing.net>).

The use of the UTF-8 character encoding scheme and of normalization
introduces additional security considerations; see Section 10 of
[RFC3629] and Section 6 of [RFC5198] for more information.

5. IANA Considerations

IANA maintains the registry of HTTP "Hypertext Transfer Protocol (HTTP) Authentication Schemes
Scheme Registry" ([RFC7235]) at <http://www.iana.org/assignments/http-authschemes>. <http://www.iana.org/assignments/
http-authschemes>.

The entry for the "Basic" Authentication Scheme shall be authentication scheme has been updated by
replacing the reference with a pointer to
reference this specification.

6. Acknowledgements

This specification takes over the definition of the "Basic" HTTP
Authentication Scheme, previously defined References

6.1. Normative References

[RFC0020] Cerf, V., "ASCII format for network interchange", STD 80,
RFC 20, DOI 10.17487/RFC0020, October 1969,
<http://www.rfc-editor.org/info/rfc20>.

[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2617. We thank John
Franks, Phillip M. Hallam-Baker, Jeffery 2119,
DOI 10.17487/RFC2119, March 1997,
<http://www.rfc-editor.org/info/rfc2119>.

[RFC2978] Freed, N. and J. Postel, "IANA Charset Registration
Procedures", BCP 19, RFC 2978, DOI 10.17487/RFC2978,
October 2000, <http://www.rfc-editor.org/info/rfc2978>.

[RFC3629] Yergeau, F., "UTF-8, a transformation format of ISO
10646", STD 63, RFC 3629, DOI 10.17487/RFC3629, November
2003, <http://www.rfc-editor.org/info/rfc3629>.

[RFC3986] Berners-Lee, T., Fielding, R., and L. Hostetler, Scott D.
Lawrence, Paul Masinter, "Uniform
Resource Identifier (URI): Generic Syntax", STD 66,
RFC 3986, DOI 10.17487/RFC3986, January 2005,
<http://www.rfc-editor.org/info/rfc3986>.

[RFC4648] Josefsson, S., "The Base16, Base32, and Base64 Data
Encodings", RFC 4648, DOI 10.17487/RFC4648, October 2006,
<http://www.rfc-editor.org/info/rfc4648>.

[RFC5198] Klensin, J. Leach, Ari Luotonen, and Lawrence C. Stewart M. Padlipsky, "Unicode Format for
their work on that specification, from which significant amounts of
text were borrowed. See Section 6 of [RFC2617] for further
acknowledgements.

The internationalization problem with respect to the character
encoding scheme used for user-pass was reported as a Mozilla bug back
in the year 2000 (see
<https://bugzilla.mozilla.org/show_bug.cgi?id=41489> and also the
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.

We also thank the members of the HTTPAuth Working Group and other
reviewers, namely Stephen Farrell, Roy Fielding, Bjoern Hoehrmann,
Daniel Kahn Gillmor, Tony Hansen, Kari Hurtta, Amos Jeffries,
Benjamin Kaduk, Michael Koeller, Eric Lawrence, Barry Leiba, James
Manger, Alexey Melnikov, Kathleen Moriarty, Juergen Schoenwaelder,
Yaron Sheffer, Meral Shirazipour, Michael Sweet, and Martin Thomson
for feedback on this revision.

7. References

7.1. Normative References

[PRECIS] Saint-Andre, P. and A. Melnikov, "Preparation,
Enforcement, and Comparison of Internationalized
Strings Representing Usernames and Passwords",
draft-ietf-precis-saslprepbis-13 (work in progress),
December 2014.

[RFC0020] Cerf, V., "ASCII format for network interchange",
RFC 20, October 1969.

[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.

[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.

[RFC3986] Berners-Lee, T., Fielding, R., and L. Masinter,
"Uniform Resource Identifier (URI): Generic Syntax",
STD 66, RFC 3986, January 2005.

[RFC4648] Josefsson, S., "The Base16, Base32, and Base64 Data
Encodings", RFC 4648, October 2006.

[RFC5198] Klensin, J. and M. Padlipsky, "Unicode Format for
Network Interchange", RFC 5198, March 2008.

[RFC5234] Crocker, D., Ed. and P. Overell, "Augmented BNF Network
Interchange", RFC 5198, DOI 10.17487/RFC5198, March 2008,
<http://www.rfc-editor.org/info/rfc5198>.

[RFC5234] Crocker, D., Ed. and P. Overell, "Augmented BNF for Syntax
Specifications: ABNF", STD 68, RFC 5234,
DOI 10.17487/RFC5234, January 2008. 2008,
<http://www.rfc-editor.org/info/rfc5234>.

[RFC6365] Hoffman, P. and J. Klensin, "Terminology Used in
Internationalization in the IETF", BCP 166, RFC 6365,
DOI 10.17487/RFC6365, September 2011. 2011,
<http://www.rfc-editor.org/info/rfc6365>.

[RFC7235] Fielding, R., Ed. and J. Reschke, Ed., "Hypertext Transfer
Protocol (HTTP/1.1): Authentication", RFC 7235,
DOI 10.17487/RFC7235, June 2014.

7.2. Informative References

[AUTHINFO] Reschke, J., "The Hypertext Transfer Protocol (HTTP)
Authentication-Info 2014,
<http://www.rfc-editor.org/info/rfc7235>.

[RFC7613] Saint-Andre, P. and Proxy-Authentication-Info
Response Header Fields",
draft-ietf-httpbis-auth-info-02 (work in progress),
February 2015.

[DIGEST] Shekh-Yusef, R., Ed., Ahrens, D., A. Melnikov, "Preparation,
Enforcement, and S. Bremer, "HTTP
Digest Access Authentication",
draft-ietf-httpauth-digest-14 (work in progress),
February 2015. Comparison of Internationalized Strings
Representing Usernames and Passwords", RFC 7613,
DOI 10.17487/RFC7613, August 2015,
<http://www.rfc-editor.org/info/rfc7613>.

6.2. Informative 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.

[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, DOI 10.17487/RFC2617, June 1999. 1999,
<http://www.rfc-editor.org/info/rfc2617>.

[RFC2818] Rescorla, E., "HTTP Over TLS", RFC 2818,
DOI 10.17487/RFC2818, May 2000. 2000,
<http://www.rfc-editor.org/info/rfc2818>.

[RFC2831] Leach, P. and C. Newman, "Using Digest Authentication as a
SASL Mechanism", RFC 2831, DOI 10.17487/RFC2831, May 2000. 2000,
<http://www.rfc-editor.org/info/rfc2831>.

[RFC3875] Robinson, D. and K. Coar, "The Common Gateway Interface
(CGI) Version 1.1", RFC 3875, DOI 10.17487/RFC3875,
October 2004, <http://www.rfc-editor.org/info/rfc3875>.

[RFC5246] Dierks, T. and E. Rescorla, "The Transport Layer Security
(TLS) Protocol Version 1.2", RFC 5246,
DOI 10.17487/RFC5246, August 2008. 2008,
<http://www.rfc-editor.org/info/rfc5246>.

[RFC6973] Cooper, A., Tschofenig, H., Aboba, B., Peterson, J.,
Morris, J., Hansen, M., and R. Smith, "Privacy
Considerations for Internet Protocols", RFC 6973,
DOI 10.17487/RFC6973, July 2013. 2013,
<http://www.rfc-editor.org/info/rfc6973>.

[RFC7231] Fielding, R., Ed. and J. Reschke, Ed., "Hypertext Transfer
Protocol (HTTP/1.1): Semantics and Content", RFC 7231,
DOI 10.17487/RFC7231, June 2014. 2014,
<http://www.rfc-editor.org/info/rfc7231>.

[RFC7615] Reschke, J., "HTTP Authentication-Info and Proxy-
Authentication-Info Response Header Fields", RFC 7615,
DOI 10.17487/RFC7615, September 2015,
<http://www.rfc-editor.org/info/rfc7615>.

[RFC7616] Shekh-Yusef, R., Ed., Ahrens, D., and S. Bremer, "HTTP
Digest Access Authentication", RFC 7616,
DOI 10.17487/RFC7616, September 2015,
<http://www.rfc-editor.org/info/rfc7616>.

Appendix A. Changes from RFC 2617

The scheme definition has been rewritten to be consistent with newer
specifications such as [RFC7235].

The new authentication parameter "charset" 'charset' has been added. It is
purely advisory, so existing implementations do not need to change,
unless they want to take advantage of the additional information
which that
previously wasn't available.

Appendix B. Deployment Considerations for the 'charset' Parameter

B.1. User Agents

User agents not implementing 'charset' will continue to work as
before, ignoring the new parameter.

User agents which that already default to the UTF-8 encoding implement
'charset' by definition.

Other user agents can keep their default behavior, behavior and switch to UTF-8
when seeing the new parameter.

B.2. Servers

Servers that do not support non-US-ASCII characters in credentials do
not require any changes to support 'charset'.

Servers that need to support non-US-ASCII characters, but cannot use
the UTF-8 character encoding scheme will not be affected; they will
continue to function as well or as badly as before.

Finally, servers that need to support non-US-ASCII characters and can
use the UTF-8 character encoding scheme can opt in by specifying the
charset
'charset' parameter in the authentication challenge. Clients that do
understand the charset 'charset' parameter will then start to use UTF-8,
while other clients will continue to send credentials in their
default encoding, broken credentials, or no credentials at all.
Until all clients are upgraded to support UTF-8, servers are likely
to see both UTF-8 and "legacy" encodings in requests. When
processing as UTF-8 fails (due to a failure to decode as UTF-8 or a
mismatch of user-id/
password), user-id/password), a server might try a fallback to the
previously supported legacy encoding in order to accomodate accommodate these
legacy clients. Note that implicit retries need to be done
carefully; for instance, some subsystems might detect repeated login
failures and treat them as a potential credentials guessing credentials-guessing attack.

B.3. Why not simply switch the default encoding to UTF-8?

There are sites in use today that default to a local character
encoding scheme, such as ISO-8859-1 ([ISO-8859-1]), and expect user
agents to use that encoding. Authentication on these sites will stop
working if the user agent switches to a different encoding, such as
UTF-8.

Note that sites might even inspect the User-Agent header field
([RFC7231], Section 5.5.3) to decide which character encoding scheme
to expect from the client. Therefore Therefore, they might support UTF-8 for
some user agents, but default to something else for others. User
agents in the latter group will have to continue to do what they do
today until the majority of these servers have been upgraded to
always use UTF-8.

Appendix C. Change Log (to be removed by RFC Editor before publication)

C.1. Since RFC 2617

Acknowledgements

This draft acts as a baseline for tracking subsequent changes to the
specification. As such, it extracts specification takes over the definition of "Basic", plus
the related Security Considerations, and also adds the IANA
registration of the scheme. Changes to the actual definition will be
made "Basic" HTTP
Authentication Scheme, previously defined in subsequent drafts.

C.2. Since draft-ietf-httpauth-basicauth-update-00

Fixed Base64 reference to point to an actual definition of Base64.

Update HTTPbis and Digest references.

Note that this spec, together with HTTPbis P7 and the Digest update,
obsoletes RFC 2617.

Rewrote text about authentication parameters We thank John
Franks, Phillip M. Hallam-Baker, Jeffery L. Hostetler, Scott
D. Lawrence, Paul J. Leach, Ari Luotonen, and Lawrence C. Stewart for
their extensibility.

Pulled in the definition work on that specification, from which significant amounts of the "charset" parameter.

Removed a misleading statement about user-ids potentially being case-
sensitive, as the same is true
text were borrowed. See Section 6 of [RFC2617] for passwords.

Added TODOs further
acknowledgements.

The internationalization problem with respect to path matching, and colons in user-ids.

C.3. Since draft-ietf-httpauth-basicauth-update-01

Minor improvements on Security Considerations.

Update Digest reference.

Rewrite the character
encoding scheme definition used for user-pass was reported as algorithm rather than pseudo-ABNF.

Add a note about colons Mozilla bug back
in user-id.

Attempt to explain authentication scopes.

C.4. Since draft-ietf-httpauth-basicauth-update-02

Reference draft-ietf-precis-saslprepbis for the set of characters
that need to be supported in user-ids year 2000 (see
<https://bugzilla.mozilla.org/show_bug.cgi?id=41489> and passwords.

C.5. Since draft-ietf-httpauth-basicauth-update-03

Update reference for draft-ietf-precis-saslprepbis (which renames
"Password" to "OpaqueString").

Mention HTTPS as enhancement for securing also the transmission of
credentials.

Update DIGEST reference and change it
more recent <https://bugzilla.mozilla.org/show_bug.cgi?id=656213>).
It was Andrew Clover's idea to informative.

Use RFC 20 as reference for ASCII.

C.6. Since draft-ietf-httpauth-basicauth-update-04

Fixed definition of authentication scope. Updated DIGEST reference.

C.7. Since draft-ietf-httpauth-basicauth-update-05

Updated DIGEST and PRECIS references.

Avoid the term "obfuscated". Say "free-form string" instead of
"opaque string" in realm description.

Mention AUTHINFO as yet another draft that helps obsoleting RFC 2617.

Add address it using a note about new auth-param.

We also thank the complexity of parsing challenges correctly.

C.8. Since draft-ietf-httpauth-basicauth-update-06

Clarify IANA action.

Remove leftover statement about use members of ABNF (which was changed in
-02).

Security considerations: mention normalization the HTTPAUTH Working Group and password storage.
Rewrite advice other
reviewers, namely, Stephen Farrell, Roy Fielding, Daniel Kahn
Gillmor, Tony Hansen, Bjoern Hoehrmann, Kari Hurtta, Amos Jeffries,
Benjamin Kaduk, Michael Koeller, Eric Lawrence, Barry Leiba, James
Manger, Alexey Melnikov, Kathleen Moriarty, Juergen Schoenwaelder,
Yaron Sheffer, Meral Shirazipour, Michael Sweet, and Martin Thomson
for feedback on counterfeiting attacks.

Update DIGEST reference.

Rewrite text about colons in user-id.

Expand deployment guidance. this revision.

Author's Address

Julian F. Reschke
greenbytes GmbH
Hafenweg 16
Muenster, NW 48155
Germany

EMail:

Email: julian.reschke@greenbytes.de
URI: http://greenbytes.de/tech/webdav/