draft-ietf-httpauth-extension-06.txt   draft-ietf-httpauth-extension-07.txt 
HTTPAUTH Working Group Y. Oiwa HTTPAUTH Working Group Y. Oiwa
Internet-Draft H. Watanabe Internet-Draft H. Watanabe
Intended status: Experimental H. Takagi Intended status: Experimental H. Takagi
Expires: November 23, 2016 ITRI, AIST Expires: January 8, 2017 ITRI, AIST
T. Hayashi T. Hayashi
Lepidum Lepidum
Y. Ioku Y. Ioku
Individual Individual
May 22, 2016 July 7, 2016
HTTP Authentication Extensions for Interactive Clients HTTP Authentication Extensions for Interactive Clients
draft-ietf-httpauth-extension-06 draft-ietf-httpauth-extension-07
Abstract Abstract
This document specifies extensions of HTTP authentication framework This document specifies extensions for the HTTP authentication
for interactive clients. Recently, fundamental features of HTTP- framework for interactive clients. Currently, fundamental features
level authentication are insufficient for complex requirements of of HTTP-level authentication are insufficient for complex
various Web-based applications. This forces these applications to requirements of various Web-based applications. This forces these
implement their own authentication frameworks using HTML Forms and applications to implement their own authentication frameworks by
other means, which becomes one of the hurdles against introducing means like HTML forms, which becomes one of the hurdles against
secure authentication mechanisms handled jointly by servers and user- introducing secure authentication mechanisms handled jointly by
agent. The extended framework fills gaps between Web application servers and user-agent. The extended framework fills gaps between
requirements and HTTP authentication provisions to solve the above Web application requirements and HTTP authentication provisions to
problems, while maintaining compatibility against existing Web and solve the above problems, while maintaining compatibility with
non-Web uses of HTTP authentications. existing Web and non-Web uses of HTTP authentications.
Status of this Memo Status of this Memo
This Internet-Draft is submitted in full conformance with the This Internet-Draft is submitted in full conformance with the
provisions of BCP 78 and BCP 79. provisions of BCP 78 and BCP 79.
Internet-Drafts are working documents of the Internet Engineering Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF). Note that other groups may also distribute Task Force (IETF). Note that other groups may also distribute
working documents as Internet-Drafts. The list of current Internet- working documents as Internet-Drafts. The list of current Internet-
Drafts is at http://datatracker.ietf.org/drafts/current/. Drafts is at http://datatracker.ietf.org/drafts/current/.
Internet-Drafts are draft documents valid for a maximum of six months Internet-Drafts are draft documents valid for a maximum of six months
and may be updated, replaced, or obsoleted by other documents at any and may be updated, replaced, or obsoleted by other documents at any
time. It is inappropriate to use Internet-Drafts as reference time. It is inappropriate to use Internet-Drafts as reference
material or to cite them other than as "work in progress." material or to cite them other than as "work in progress."
This Internet-Draft will expire on November 23, 2016. This Internet-Draft will expire on January 8, 2017.
Copyright Notice Copyright Notice
Copyright (c) 2016 IETF Trust and the persons identified as the Copyright (c) 2016 IETF Trust and the persons identified as the
document authors. All rights reserved. document authors. All rights reserved.
This document is subject to BCP 78 and the IETF Trust's Legal This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents Provisions Relating to IETF Documents
(http://trustee.ietf.org/license-info) in effect on the date of (http://trustee.ietf.org/license-info) in effect on the date of
publication of this document. Please review these documents publication of this document. Please review these documents
skipping to change at page 3, line 13 skipping to change at page 3, line 13
described in the Simplified BSD License. described in the Simplified BSD License.
Table of Contents Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 4 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 4
1.1. Terminology . . . . . . . . . . . . . . . . . . . . . . . 4 1.1. Terminology . . . . . . . . . . . . . . . . . . . . . . . 4
2. Definitions . . . . . . . . . . . . . . . . . . . . . . . . . 5 2. Definitions . . . . . . . . . . . . . . . . . . . . . . . . . 5
2.1. Terms for describing authentication protocol flow . . . . 5 2.1. Terms for describing authentication protocol flow . . . . 5
2.2. Syntax Notation . . . . . . . . . . . . . . . . . . . . . 7 2.2. Syntax Notation . . . . . . . . . . . . . . . . . . . . . 7
3. Optional Authentication . . . . . . . . . . . . . . . . . . . 8 3. Optional Authentication . . . . . . . . . . . . . . . . . . . 8
4. Authentication-Control header . . . . . . . . . . . . . . . . 9 3.1. Note on Optional-WWW-Authenticate and use of
4.1. Non-ASCII extended header parameters . . . . . . . . . . . 11 WWW-Authenticate header with non-401 status . . . . . . . 9
4.2. Auth-style parameter . . . . . . . . . . . . . . . . . . . 12 4. Authentication-Control header . . . . . . . . . . . . . . . . 11
4.3. Location-when-unauthenticated parameter . . . . . . . . . 13 4.1. Non-ASCII extended header parameters . . . . . . . . . . . 12
4.4. No-auth parameter . . . . . . . . . . . . . . . . . . . . 13 4.2. Auth-style parameter . . . . . . . . . . . . . . . . . . . 13
4.5. Location-when-logout parameter . . . . . . . . . . . . . . 14 4.3. Location-when-unauthenticated parameter . . . . . . . . . 14
4.6. Logout-timeout parameter . . . . . . . . . . . . . . . . . 15 4.4. No-auth parameter . . . . . . . . . . . . . . . . . . . . 15
4.7. Username parameter . . . . . . . . . . . . . . . . . . . . 15 4.5. Location-when-logout parameter . . . . . . . . . . . . . . 15
5. Usage examples (informative) . . . . . . . . . . . . . . . . . 16 4.6. Logout-timeout parameter . . . . . . . . . . . . . . . . . 16
5.1. Example 1: a portal site . . . . . . . . . . . . . . . . . 16 4.7. Username parameter . . . . . . . . . . . . . . . . . . . . 17
5.1.1. Case 1: a simple application . . . . . . . . . . . . . 17 5. Usage examples . . . . . . . . . . . . . . . . . . . . . . . . 17
5.1.2. Case 2: specific action required on log-out . . . . . 17 5.1. Example 1: a portal site . . . . . . . . . . . . . . . . . 18
5.1.3. Case 3: specific page displayed before log-in . . . . 18 5.1.1. Case 1: a simple application . . . . . . . . . . . . . 18
5.2. Example 2: authenticated user-only sites . . . . . . . . . 18 5.1.2. Case 2: specific action required on log-out . . . . . 19
5.3. When to use Cookies . . . . . . . . . . . . . . . . . . . 18 5.1.3. Case 3: specific page displayed before log-in . . . . 19
5.4. Parallel deployment with Form/Cookie authentications . . . 19 5.2. Example 2: authenticated user-only sites . . . . . . . . . 19
6. Methods to extend this protocol . . . . . . . . . . . . . . . 20 5.3. When to use Cookies . . . . . . . . . . . . . . . . . . . 20
7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 20 5.4. Parallel deployment with Form/Cookie authentications . . . 20
8. Security Considerations . . . . . . . . . . . . . . . . . . . 21 6. Methods to extend this protocol . . . . . . . . . . . . . . . 21
9. References . . . . . . . . . . . . . . . . . . . . . . . . . . 22 7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 22
9.1. Normative References . . . . . . . . . . . . . . . . . . . 22 8. Security Considerations . . . . . . . . . . . . . . . . . . . 23
9.2. Informative References . . . . . . . . . . . . . . . . . . 23 9. References . . . . . . . . . . . . . . . . . . . . . . . . . . 24
9.1. Normative References . . . . . . . . . . . . . . . . . . . 24
9.2. Informative References . . . . . . . . . . . . . . . . . . 24
Appendix A. (Informative) Applicability of features for each Appendix A. (Informative) Applicability of features for each
messages . . . . . . . . . . . . . . . . . . . . . . 23 messages . . . . . . . . . . . . . . . . . . . . . . 25
Appendix B. (Informative) Draft Change Log . . . . . . . . . . . 24 Appendix B. (Informative) Draft Change Log . . . . . . . . . . . 25
B.1. Changes in Httpauth WG Revision 06 . . . . . . . . . . . . 24 B.1. Changes in Httpauth WG Revision 07 . . . . . . . . . . . . 25
B.2. Changes in Httpauth WG Revision 05 . . . . . . . . . . . . 24 B.2. Changes in Httpauth WG Revision 06 . . . . . . . . . . . . 25
B.3. Changes in Httpauth WG revision 04 . . . . . . . . . . . . 24 B.3. Changes in Httpauth WG Revision 05 . . . . . . . . . . . . 26
B.4. Changes in Httpauth WG revision 03 . . . . . . . . . . . . 24 B.4. Changes in Httpauth WG revision 04 . . . . . . . . . . . . 26
B.5. Changes in Httpauth WG revision 02 . . . . . . . . . . . . 24 B.5. Changes in Httpauth WG revision 03 . . . . . . . . . . . . 26
B.6. Changes in Httpauth WG revision 01 . . . . . . . . . . . . 24 B.6. Changes in Httpauth WG revision 02 . . . . . . . . . . . . 26
B.7. Changes in Httpauth revision 00 and HttpBis revision 00 . 24 B.7. Changes in Httpauth WG revision 01 . . . . . . . . . . . . 26
B.8. Changes in revision 02 . . . . . . . . . . . . . . . . . . 24 B.8. Changes in Httpauth revision 00 and HttpBis revision 00 . 26
B.9. Changes in revision 01 . . . . . . . . . . . . . . . . . . 25 B.9. Changes in revision 02 . . . . . . . . . . . . . . . . . . 26
B.10. Changes in revision 00 . . . . . . . . . . . . . . . . . . 25 B.10. Changes in revision 01 . . . . . . . . . . . . . . . . . . 26
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 25 B.11. Changes in revision 00 . . . . . . . . . . . . . . . . . . 26
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 27
1. Introduction 1. Introduction
The document proposes several extensions to the current HTTP This document defines several extensions to the current HTTP
authentication framework, to provide functionality comparable with authentication framework, to provide functionality comparable with
current widely-used form-based Web authentication. A majority of the current widely-used form-based Web authentication. A majority of the
recent websites on the Internet use custom application-layer recent websites on the Internet use custom application-layer
authentication implementations using Web forms. The reasons for authentication implementations using Web forms. The reasons for
these may vary, but many people believe that the current HTTP Basic these may vary, but many people believe that the current HTTP Basic
and Digest authentication methods do not have enough functionality and Digest authentication methods do not have enough functionality
(including good user interfaces) to support most realistic Web-based (including good user interfaces) to support most realistic Web-based
applications. However, this method is very weak against phishing and applications. However, such use of form-based Web authentication has
other attacks, because all behavior of the authentication is several weakness against attacks like phishing, because all behavior
controlled from the server-side application. This makes it really of the authentication is controlled from the server-side application.
hard to implement any cryptographically strong authentication This makes it really hard to implement any cryptographically strong
mechanisms into Web systems. To overcome this problem, we need to authentication mechanisms into Web systems. To overcome this
"modernize" the HTTP authentication framework so that better client- problem, we need to "modernize" the HTTP authentication framework so
controlled secure methods can be used with Web applications. The that better client-controlled secure methods can be used with Web
extensions proposed in this document include: applications. The extensions proposed in this document include:
o optional authentication on HTTP (Section 3), o optional authentication on HTTP (Section 3),
o log out from both server and client side (Section 4), and o log out from both server and client side (Section 4), and
o finer control for redirection depending on authentication status o finer control for redirection depending on authentication status
(Section 4). (Section 4).
1.1. Terminology 1.1. Terminology
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and
"OPTIONAL" in this document are to be interpreted as described in "OPTIONAL" in this document are to be interpreted as described in
[RFC2119]. [RFC2119].
The terms "encouraged" and "advised" are used for suggestions that do The terms "encouraged" and "advised" are used for suggestions that do
not constitute "SHOULD"-level requirements. People MAY freely choose not constitute "SHOULD"-level requirements. People MAY freely choose
not to include the suggested items regarding [RFC2119], but complying not to include the suggested items. However, complying with those
with those suggestions would be a best practice; it will improve the suggestions would be a best practice; it will improve the security,
security, interoperability, and/or operational performance. interoperability, and/or operational performance.
This document distinguishes the terms "client" and "user" in the This document distinguishes the terms "client" and "user" in the
following way: A "client" is an entity understanding and talking HTTP following way: A "client" is an entity understanding and talking HTTP
and the specified authentication protocol, usually computer software; and the specified authentication protocol, usually computer software;
a "user" is a (usually natural) person who wants to access data a "user" is a (usually natural) person who wants to access data
resources using "a client". resources using "a client".
2. Definitions 2. Definitions
2.1. Terms for describing authentication protocol flow 2.1. Terms for describing authentication protocol flow
HTTP Authentication defined in [RFC7235] may involve several pairs of HTTP Authentication defined in [RFC7235] can involve several pairs of
HTTP requests/responses. Throughout this document, the following HTTP requests/responses. Throughout this document, the following
terms are used to categorize those messages: for requests, terms are used to categorize those messages: for requests,
1) A non-authenticating request is a request not attempting any 1) A non-authenticating request is a request not attempting any
authentication: a request without any Authorization header. authentication: a request without any Authorization header field.
2) An authenticating request is the opposite: a request with an 2) An authenticating request is the opposite: a request with an
Authorization header. Authorization header field.
For responses, For responses,
1) A non-authenticated response is a response which does not involve 1) A non-authenticated response is a response which does not involve
any HTTP authentication. It does not contain any WWW-Authenticate any HTTP authentication. It does not contain any WWW-Authenticate
or Authentication-Info header. or Authentication-Info header field.
Servers send this response when the requested resource is not Servers send this response when the requested resource is not
protected by an HTTP authentication mechanism. In context of this protected by an HTTP authentication mechanism. In context of this
specification, non-authentication-related negative responses (e.g. specification, non-authentication-related negative responses (e.g.
403 and 404) are also considered non-authenticated responses. 403 and 404) are also considered non-authenticated responses.
(See note on successfully-authenticated responses below for some (See note on successfully-authenticated responses below for some
ambiguous cases.) ambiguous cases.)
2) An authentication-initializing response is a response which 2) An authentication-initializing response is a response which
skipping to change at page 6, line 17 skipping to change at page 6, line 17
* On the other hand, if client already has enough authentication * On the other hand, if client already has enough authentication
credentials to the requested protection space, the client will credentials to the requested protection space, the client will
automatically send an authenticating request. Such cases often automatically send an authenticating request. Such cases often
occur when the client did not know beforehand that the current occur when the client did not know beforehand that the current
request-URL requires authentication. request-URL requires authentication.
3) A successfully-authenticated response is a response for an 3) A successfully-authenticated response is a response for an
authenticating request meaning that the authentication attempt was authenticating request meaning that the authentication attempt was
granted. (Note: if the authentication scheme used does not use an granted. (Note: if the authentication scheme used does not use an
Authentication-Info header, it may be indistinguishable from a Authentication-Info header field, it can't be distinguishable from
non-authenticated response.) a non-authenticated response.)
4) An intermediate authenticating response is a response for an 4) An intermediate authenticating response is a response for an
authenticating request which requires more reaction by the client authenticating request which requires more reaction by the client
software without involving users. Such a response is required software without involving users. Such a response is required
when an authentication scheme requires two or more round-trip when an authentication scheme requires two or more round-trip
messages to perform authentication, or when an authentication messages to perform authentication, or when an authentication
scheme uses some speculative short-cut method (such as uses of scheme uses some speculative short-cut method (such as uses of
cached shared secrets) and it failed. cached shared secrets) and it failed.
5) A negatively-authenticated response is a response for an 5) A negatively-authenticated response is a response for an
authenticating request which means that the authentication attempt authenticating request which means that the authentication attempt
was declined and can not continue without a different set of was declined and can not continue without a different set of
authentication credentials. Clients typically erase memory of the authentication credentials. Clients typically erase memory of the
active credentials and ask the user for other ones. active credentials and ask the user for other ones.
Usually the format of these responses are as same as the one for Usually the format of these responses are as same as the one for
authentication-initializing responses. Client can distinguish authentication-initializing responses. Clients can distinguish
negatively-authenticated responses from authentication- negatively-authenticated responses from authentication-
initializing responses by comparing the protection spaces initializing responses by comparing the protection spaces
contained in the request and in the response. contained in the request and in the response.
Figure 1 shows a state diagram of generic HTTP authentication with Figure 1 shows a state diagram of generic HTTP authentication with
the above message categorization. Note that many authentication the above message categorization. Note that many authentication
schemes use only a subset of the transitions described on the schemes use only a subset of the transitions described on the
diagram. Labels in the figure show the abbreviated names of response diagram. Labels in the figure show the abbreviated names of response
types. types.
skipping to change at page 7, line 50 skipping to change at page 7, line 50
Figure 1: Generic state diagram for HTTP authentication Figure 1: Generic state diagram for HTTP authentication
Note: (*1) For example, "Digest" scheme requires server-provided Note: (*1) For example, "Digest" scheme requires server-provided
nonce to construct client-side challenges. nonce to construct client-side challenges.
(*2) In "Basic" and some others, this cannot be distinguished from a (*2) In "Basic" and some others, this cannot be distinguished from a
successfully-authenticated response. successfully-authenticated response.
2.2. Syntax Notation 2.2. Syntax Notation
This specification uses an extended BNF syntax defined in [RFC7230]. This specification uses an extended ABNF syntax defined in [RFC7230]
The following syntax definitions are quoted from [RFC7230] and and [RFC5234]. The following syntax definitions are quoted from
[RFC7235]: auth-scheme, quoted-string, auth-param, SP, BWS, header- [RFC7230] and [RFC7235]: auth-scheme, quoted-string, auth-param, SP,
field, and challenge. It also uses the convention of using header BWS, header-field, and challenge. It also uses the convention of
names for specifying the syntax of header values. using header field names for specifying the syntax of values for the
header field.
Additionally, this specification uses the following syntax Additionally, this specification uses the following syntax
definitions as a refinement for token and the right-hand-side of definitions as a refinement for token and the right-hand-side of
auth-param in [RFC7235]. (Note: these definitions are consistent auth-param in [RFC7235]. (Note: these definitions are consistent
with those in [I-D.ietf-httpauth-mutual].) with those in [I-D.ietf-httpauth-mutual].)
bare-token = 1*(%x30-39 / %x41-5A / %x61-7A / "-" / "_") bare-token = 1*(%x30-39 / %x41-5A / %x61-7A / "-" / "_")
extension-token = "-" bare-token 1*("." bare-token) extension-token = "-" bare-token 1*("." bare-token)
extensive-token = bare-token / extension-token extensive-token = bare-token / extension-token
integer = "0" / (%x31-39 *%x30-39) ; no leading zeros integer = "0" / (%x31-39 *%x30-39) ; no leading zeros
Figure 2: the BNF syntax for common notations Figure 2: the BNF syntax for common notations
Extensive-tokens are used in this protocol where the set of Extensive-tokens are used in this protocol where the set of
acceptable tokens may include private extensions. Any private acceptable tokens includes private extensions. Any extensions of
extensions of this protocol MUST use extension-tokens with the format this protocol MAY use either bare-tokens allocated by IANA (under the
"-<token>.<domain-name>", where <domain-name> is a valid (sub-)domain procedure described in Section 7), or extension-tokens with the
name on the Internet owned by the party who defines the extension. format "-<token>.<domain-name>", where <domain-name> is a valid
(sub-)domain name on the Internet owned by the party who defines the
extension.
3. Optional Authentication 3. Optional Authentication
The Optional-WWW-Authenticate header enables a non-mandatory The Optional-WWW-Authenticate header enables a non-mandatory
authentication, which is not possible under the current HTTP authentication, which is not possible under the current HTTP
authentication mechanism. In several Web applications, users can authentication mechanism.
access the same contents as both a guest user and an authenticated
user. In most Web applications, This functionality is implemented In several Web applications, users can access the same contents as
using HTTP cookies [RFC6265] and custom form-based authentication. both a guest user and an authenticated user. In most Web
The new authentication method using this message will provide a applications, this functionality is implemented using HTTP cookies
replacement for these authentication systems. [RFC6265] and custom form-based authentication. The new
authentication method using this message will provide a replacement
for these authentication systems.
Servers MAY send HTTP non-interim responses containing the Servers MAY send HTTP non-interim responses containing the
Optional-WWW-Authenticate header as a replacement of a 401 response Optional-WWW-Authenticate header as a replacement of a 401 response
when it the response is authentication-initializing. The when it the response is authentication-initializing. The
Optional-WWW-Authenticate header MUST NOT sent on 401 responses (i.e. Optional-WWW-Authenticate header MUST NOT sent on 401 responses (i.e.
a usual WWW-Authenticate header MUST be used on 401 responses.) a usual WWW-Authenticate header MUST be used on 401 responses.)
HTTP/1.1 200 OK HTTP/1.1 200 OK
Optional-WWW-Authenticate: Basic realm="xxxx" Optional-WWW-Authenticate: Basic realm="xxxx"
Optional-WWW-Authenticate = 1#challenge Optional-WWW-Authenticate = 1#challenge
Figure 3: BNF syntax for Optional-WWW-Authenticate header Figure 3: BNF syntax for Optional-WWW-Authenticate header
The challenges contained in the Optional-WWW-Authenticate header are The challenges contained in the Optional-WWW-Authenticate header are
the same as those for a 401 responses corresponding to the same the same as those for a 401 responses corresponding to the same
request. For authentication-related matters, an optional request. For authentication-related matters, an optional
authentication request will have the same meaning as a 401 message authentication request will have the same meaning as a 401 message
with a corresponding WWW-Authenticate header (as an authentication- with a corresponding WWW-Authenticate header (as an authentication-
initializing response). (The behavior for other matters, such as initializing response). (The behavior for other matters MAY be
caching, MAY be different between the optional authentication and 401 different between the optional authentication and 401 messages. For
messages.) example, clients MAY choose to cache the 200 messages with
Optional-WWW-Authenticate header field but not the 401 messages by
default.)
A response with an Optional-WWW-Authenticate header SHOULD be A response with an Optional-WWW-Authenticate header SHOULD be
returned from the server only when the request is either non- returned from the server only when the request is either non-
authenticated or authenticating to a wrong (not the server's authenticated or authenticating to a wrong (not the server's
expected) protection space. If a response is either an intermediate expected) protection space. If a response is either an intermediate
or a negative response to a client's authentication attempt, the or a negative response to a client's authentication attempt, the
server MUST respond with a 401 status response with a server MUST respond with a 401 status response with a
WWW-Authenticate header instead. Failure to comply with this rule WWW-Authenticate header instead. Failure to comply with this rule
will render clients unable to distinguish authentication successes will render clients unable to distinguish authentication successes
and failures. and failures.
skipping to change at page 9, line 37 skipping to change at page 9, line 43
Whenever an authentication scheme supports servers sending some Whenever an authentication scheme supports servers sending some
parameter which gives a hint of the URL space for the corresponding parameter which gives a hint of the URL space for the corresponding
protection space for the same realm (e.g. "path" or "domain"), protection space for the same realm (e.g. "path" or "domain"),
servers requesting non-mandatory authentication SHOULD send such servers requesting non-mandatory authentication SHOULD send such
parameter with the response. Clients supporting non-mandatory parameter with the response. Clients supporting non-mandatory
authentication MUST recognize the parameter, and MUST send a request authentication MUST recognize the parameter, and MUST send a request
with an appropriate authentication credential in an Authorization with an appropriate authentication credential in an Authorization
header for any URI inside the specified paths. header for any URI inside the specified paths.
Support of this header is OPTIONAL; Clients MAY also choose any set Support of this header is OPTIONAL; clients MAY also implement this
of authentication schemes for which optional authentication is extension only for some selected authentication schemes. New
supported (in other words, its support MAY be scheme-dependent). authentication schemes can make support of the optional
However, some authentication schemes MAY require mandatory/ authentication mandatory by its specification, though.
recommended support for this header, so that server-side applications
MAY assume that clients supporting such schemes are likely to support 3.1. Note on Optional-WWW-Authenticate and use of WWW-Authenticate
the extension as well. header with non-401 status
In the current specification of HTTP/1.1, it is clarified that the
WWW-Authenticate header can be used with messages with status codes
other than 401 (Authentication Required). Especially, the use of
WWW-Authenticate header with the 200 status messages implies a very
similar meaning to the above-defined Optional-WWW-Authenticate
header.
The design of Optional-WWW-Authenticate header expects that the use
of a new header guarantees that clients which is unaware of this
extension will ignore the header, and that Web developers can rely on
that behavior to implement a secondary fallback method of
authentications. Several behavioral requirements written in the
above section also assumes this property, and defines a necessary
functionality to implement an HTTP optional authentication reliably
and consistently.
On the other hand, some experiments and discussions on the IETF
mailing list revealed that most of (but not necessarily all of) the
existing HTTP clients, at the time of writing, just ignores the WWW-
Authenticate headers in non-401 messages, giving the similar behavior
with the Optional-WWW-Authenticate. However, every corner case of
behavior was not fully tested, nor well-defined in the existing
specifications.
Considering these situations, the author of this document chose to
use a new header for a new feature "experiment". This is to avoid
defining every corner-case behavior for the existing standard WWW-
Authentication header in this experimental document, which could be
considered by some implementer as an "incompatible changes to
existing specification".
Experimentally, the authors propose implementer of the standard
HTTP/1.1 specification (especially implementer of this extension) to
implement undefined (implementation-dependant) detailed handling of
WWW-Authenticate header with non-401 status messages as similar as
those defined above for the Optional-WWW-Authenticate header. For
example, we propose for servers to return 401 status for failed
authentication attempts, even when the unauthenticated request to the
same resource will result in the 200 status. This can realize how
(whether) we can implement non-mandatory authentication using the
standard header fields and status codes. If this experiment is
successful, the future revision of this experimental document may
"bless" and recommend the use of standard WWW-Authenticate header,
with some "standard-level" requirements on some corner case behavior.
4. Authentication-Control header 4. Authentication-Control header
Authentication-Control = 1#Auth-Control-Entry
Auth-Control-Entry = auth-scheme 1*SP 1#auth-control-param Authentication-Control = 1#auth-control-entry
auth-control-entry = auth-scheme 1*SP 1#auth-control-param
auth-control-param = extensive-token BWS "=" BWS token auth-control-param = extensive-token BWS "=" BWS token
/ extensive-token "*" BWS "=" BWS ext-value / extensive-token "*" BWS "=" BWS ext-value
ext-value = <see RFC 5987, Section 3.2> ext-value = <see RFC 5987, Section 3.2>
Figure 4: the BNF syntax for the Authentication-Control header Figure 4: the BNF syntax for the Authentication-Control header
The Authentication-Control header provides a more precise control of The Authentication-Control header provides a more precise control of
the client behavior for Web applications using an HTTP authentication the client behavior for Web applications using an HTTP authentication
protocol. This header is supposed to be generated in the application protocol. This header is supposed to be generated in the application
layer, as opposed to WWW-Authenticate headers which will usually be layer, as opposed to WWW-Authenticate headers which will usually be
generated by the Web servers. generated by the Web servers.
Support of this header is OPTIONAL, and clients MAY choose any subset Support of this header is OPTIONAL, and clients MAY choose any subset
of these parameters to be supported. The set of supported parameters of these parameters to be supported. The set of supported parameters
MAY also be authentication scheme-dependent. However, some MAY also be authentication scheme-dependent. However, some
authentication schemes MAY require mandatory/recommended support for authentication schemes can require mandatory/recommended support for
some or all of the features provided in this header. some or all of the features provided in this header.
The Authentication-Control header contains one or more The Authentication-Control header contains one or more
"authentication control entries" each of which corresponds to a "authentication control entries" each of which corresponds to a
single realm for a specific authentication scheme. If the single realm for a specific authentication scheme. If the
auth-scheme specified for an entry supports the HTTP "realm" feature, auth-scheme specified for an entry supports the HTTP "realm" feature,
that entry MUST contain the "realm" parameter. If not, the entry that entry MUST contain the "realm" parameter. If not, the entry
MUST NOT contain the "realm" parameter. MUST NOT contain the "realm" parameter.
Among the multiple entries in the header, the meaningful entries in Among the multiple entries in the header, the relevant entries in the
the header are those corresponding to an auth-scheme and a realm (if header are those corresponding to an auth-scheme and a realm (if
any), for which "the authentication process is being performed, or any), for which "the authentication process is being performed, or
going to be performed". In more detail, going to be performed". In more detail,
(1) If the response is either an authentication-initializing (1) If the response is either an authentication-initializing
response or a negatively-authenticated response, there may be response or a negatively-authenticated response, there can be
multiple challenges in the WWW-Authenticate header (or the multiple challenges in the WWW-Authenticate header (or the
Optional-WWW-Authenticate header defined in this extension), Optional-WWW-Authenticate header defined in this extension),
each of which corresponds to a different scheme and realm. In each of which corresponds to a different scheme and realm. In
this case, the client has a choice on the scheme and realm they this case, the client has a choice on the scheme and realm they
will use to authenticate. Only the entry in the will use to authenticate. Only the entry in the
&Authentication-Control; header corresponding to that scheme and Authentication-Control header corresponding to that scheme and
realm are meaningful. realm are relevant.
(2) If the response is either an intermediate authenticating (2) If the response is either an intermediate authenticating
response or a successfully-authenticated response, the scheme response or a successfully-authenticated response, the scheme
and realm given in the Authorization header of the HTTP request and realm given in the Authorization header of the HTTP request
will determine the currently-ongoing authentication process. will determine the currently-ongoing authentication process.
Only the entry corresponding to that scheme and realm are Only the entry corresponding to that scheme and realm are
meaningful. relevant.
The server MAY send an Authentication-Control header containing non- The server MAY send an Authentication-Control header containing non-
meaningful entries. The client MUST ignore all non-meaningful relevant entries. The client MUST ignore all non-relevant entries it
entries it received. received.
Each entry contains one or more parameters, each of which is a name- Each entry contains one or more parameters, each of which is a name-
value pair. The name of each parameter MUST be an extensive-token. value pair. The name of each parameter MUST be an extensive-token.
Clients MUST ignore any unknown parameters contained in this header. Clients MUST ignore any unknown parameters contained in this header.
The entries for the same auth-scheme and the realm MUST NOT contain The entries for the same auth-scheme and the realm MUST NOT contain
duplicated parameters for the same name. duplicated parameters for the same name. Clients MAY either take any
one of those duplicated entries or ignore all of them.
The type of parameter value depends on the parameter name as defined The type of parameter value depends on the parameter name as defined
in the following subsections. Regardless of the type, however, the in the following subsections. Regardless of the type, however, the
recipients SHOULD accept both quoted and unquoted representations of recipients MUST accept both quoted and unquoted representations of
values as defined in HTTP. If the parameter is defined to have a values as defined in HTTP. If the parameter is defined to have a
string value, implementations SHOULD send the parameter in a quoted string value, implementations MUST send any value outside of the
form or an ext-value form (see Section 4.1). If the parameter is "token" ABNF syntax in either a quoted form or an an ext-value form
defined as a token (or similar) or an integer, the value SHOULD (see Section 4.1). If the parameter is defined as a token (or
follow the corresponding ABNF syntax after possible unquoting of the similar) or an integer, the value SHOULD follow the corresponding
quoted-string value (as defined in HTTP), and SHOULD be sent in a ABNF syntax after possible unquoting of the quoted-string value (as
unquoted form. defined in HTTP), and MUST be sent in an plain (not an ext-value)
form. (Note: the rest of this document will show all string-value
parameters in quoted forms, and others in unquoted forms.)
Server-side applications SHOULD be aware that any parameters Any parameters contained in this header MAY be ignored by clients.
contained in this header MAY be ignored by clients. Also, even when Also, even when a client accepts this header, users are able to
a client accepts this header, users may always be able to circumvent circumvent the semantics of this header. Therefore, if this header
the semantics of this header. Therefore, if this header is used for is used for security purposes, its use MUST be limited to providing
security purposes, its use MUST be limited to providing some non- some non-fundamental additional security measures valuable for end-
fundamental additional security measures valuable for end-users (such users (such as client-side log-out for protecting against console
as client-side log-out for protecting against console takeover). takeover). Server-side applications MUST NOT rely on the use of this
Server-side applications MUST NOT rely on the use of this header for header for protecting server-side resources.
protecting server-side resources.
Note: The header syntax allows servers to specify Authentication- Note: The header syntax allows servers to specify Authentication-
Control for multiple authentication schemes, either as multiple Control for multiple authentication schemes, either as multiple
occurrences of this header or as a combined single header (see occurrences of this header or as a combined single header (see
Section 3.2.2 of [RFC7230] for rationale). The same care as for Section 3.2.2 of [RFC7230] for rationale). The same care as for
parsing multiple authentication challenges SHALL be taken. parsing multiple authentication challenges needs to be taken.
4.1. Non-ASCII extended header parameters 4.1. Non-ASCII extended header parameters
Parameters contained in the Authentication-Control header MAY be Parameters contained in the Authentication-Control header MAY be
extended to ISO 10646-1 values using the framework described in extended to non-ASCII values using the framework described in
[RFC5987]. All servers and clients MUST be capable of receiving and [RFC5987]. All servers and clients MUST be capable of receiving and
sending values encoded in [RFC5987] syntax. sending values encoded in [RFC5987] syntax.
If a value to be sent contains only ASCII characters, the field MUST If a value to be sent contains only ASCII characters, the field MUST
be sent using plain RFC 7235 syntax. The syntax as extended by RFC be sent using plain RFC 7235 syntax. The syntax as extended by ext-
5987 MUST NOT be used in this case. value MUST NOT be used in this case.
If a value (except the "realm" header) contains one or more non-ASCII If a value (except the "realm" header) contains one or more non-ASCII
characters, the parameter SHOULD be sent using the ext-value syntax characters, the parameter SHOULD be sent using the ext-value syntax
defined in Section 3.2 of [RFC5987]. Such a parameter MUST have a defined in Section 3.2 of [RFC5987]. Such a parameter MUST have a
charset value of "UTF-8", and the language value MUST always be charset value of "UTF-8", and the language value MUST always be
omitted (have an empty value). The same parameter MUST NOT be sent omitted (have an empty value). The same parameter MUST NOT be sent
more than once, regardless of the used syntax. more than once, regardless of the used syntax.
For example, a parameter "username" with value "Renee of France" For example, a parameter "username" with value "Renee of France"
SHOULD be sent as < username="Renee of France" >. If the value is SHOULD be sent as < username="Renee of France" >. If the value is
"Ren<e acute>e of France", it SHOULD be sent as < username*=UTF- "Ren<e acute>e of France", it SHOULD be sent as
8''Ren%C3%89e%20of%20France > instead. < username*=UTF-8''Ren%C3%89e%20of%20France > instead.
Interoperability note: [RFC7235], Section 2.2, defines the "realm"
authentication parameter which cannot be replaced by the "realm*"
extend parameter. It means that the use of non-ASCII values for an
authentication realm is not the defined behavior in the HTTP.
Unfortunately, some people currently use non-ASCII realm parameter in
reality, but even its encoding scheme is not well-defined.
Given this background, this document does not specify how to handle
non-ASCII "realm" parameter in the extended header fields. If
needed, the authors propose to use a non-extended "realm" parameter
form, with a wish for maximum interoperability.
4.2. Auth-style parameter 4.2. Auth-style parameter
Example:
Authentication-Control: Digest realm="protected space", Authentication-Control: Digest realm="protected space",
auth-style=modal auth-style=modal
The parameter "auth-style" specifies the server's preferences for The parameter "auth-style" specifies the server's preferences for
user interface behavior for user authentication. This parameter can user interface behavior for user authentication. This parameter can
be included in any kind of response, however, it is only meaningful be included in any kind of response, however, it is only meaningful
for either authentication-initializing or negatively-authenticated for either authentication-initializing or negatively-authenticated
responses. The value of this parameter MUST be one of the bare- responses. The value of this parameter MUST be one of the bare-
tokens "modal" or "non-modal". When the Optional-WWW-Authenticate tokens "modal" or "non-modal". When the Optional-WWW-Authenticate
header is used, the value of this parameter MUST be disregarded and header is used, the value of this parameter MUST be disregarded and
skipping to change at page 12, line 44 skipping to change at page 14, line 11
expected to ask the user for a password before processing the expected to ask the user for a password before processing the
content. This behavior is common for most of the current content. This behavior is common for most of the current
implementations of Basic and Digest authentication schemes. implementations of Basic and Digest authentication schemes.
The value "non-modal" means that the server thinks the content of the The value "non-modal" means that the server thinks the content of the
response (body and other content-related headers) is valuable for response (body and other content-related headers) is valuable for
users before processing an authentication request. The clients are users before processing an authentication request. The clients are
expected to first process the content and then provide users the expected to first process the content and then provide users the
opportunity to perform authentication. opportunity to perform authentication.
The default behavior for clients is implementation-dependent, and The default behavior for clients is implementation-dependent, and it
clients MAY choose different defaults for different authentication may also depending on authentication schemes. The proposed default
schemes. The proposed default behavior is "modal" for all behavior is "modal" for all authentication schemes unless otherwise
authentication schemes, but specifications for authentication schemes specified.
MAY propose a different default.
The above two different methods of authentication may introduce a The above two different methods of authentication possibly introduce
observable difference of semantics when the response contains state- a observable difference of semantics when the response contains
changing side effects; for example, it may change whether Cookie state-changing side effects; for example, it can affect how Cookie
headers [RFC6265] in 401 responses are processed or not. However, headers [RFC6265] in 401 responses are processed. However, the
the server applications SHOULD NOT depend on both existence and non- server applications SHOULD NOT depend on existence of such side
existence of such side effects. effects.
4.3. Location-when-unauthenticated parameter 4.3. Location-when-unauthenticated parameter
Example:
Authentication-Control: Mutual realm="auth-space-1", Authentication-Control: Mutual realm="auth-space-1",
location-when-unauthenticated="http://www.example.com/login.html" location-when-unauthenticated="http://www.example.com/login.html"
The parameter "location-when-unauthenticated" specifies a location The parameter "location-when-unauthenticated" specifies a location
where any unauthenticated clients should be redirected to. This where any unauthenticated clients should be redirected to. This
header may be used, for example, when there is a central login page header can be used, for example, when there is a central login page
for the entire Web application. The value of this parameter is a for the entire Web application. The value of this parameter is a
string that contains an absolute URL location. Senders MUST always string that contains an URL location. If a received URL is not
send an absolute URL location. If a received URL is not absolute, absolute, the clients SHOULD consider it a relative URL from the
the clients SHOULD either ignore it or consider it a relative URL current location.
from the current location.
This parameter MAY be used with a 401 response for an authentication- This parameter MAY be used with a 401 response for an authentication-
initializing response. It can also be contained, although this is initializing response. It can also be contained, although this is
NOT RECOMMENDED, in a positive response with an NOT RECOMMENDED, in a positive response with an
Optional-WWW-Authenticate header. The clients MUST ignore this Optional-WWW-Authenticate header. The clients MUST ignore this
parameter when a response is either successfully-authenticated or parameter when a response is either successfully-authenticated or
intermediately-authenticated. The clients SHOULD ignore this intermediately-authenticated.
parameter when a response is a negatively-authenticated one (the case
is unlikely to happen, though).
When a client receives an authentication-initiating response with When a client receives an authentication-initiating response with
this parameter, if the client has to ask users for authentication this parameter, and if the client has to ask users for authentication
credentials, the client will treat the entire response as if it were credentials, the client will treat the entire response as if it were
a 303 "See Other" response with a Location header that contains the a 303 "See Other" response with a Location header that contains the
value of this parameter (i.e., client will be redirected to the value of this parameter (i.e., client will be redirected to the
specified location with a GET request). Unlike a normal 303 specified location with a GET request). Unlike a normal 303
response, if the client can process authentication without the user's response, if the client can process authentication without the user's
interaction, this parameter MUST be ignored. interaction, this parameter MUST be ignored.
4.4. No-auth parameter 4.4. No-auth parameter
Example:
Authentication-Control: Basic realm="entrance", no-auth=true Authentication-Control: Basic realm="entrance", no-auth=true
The parameter "no-auth" is a variant of the The parameter "no-auth" is a variant of the
location-when-unauthenticated parameter; it specifies that new location-when-unauthenticated parameter; it specifies that new
authentication attempts are not to be performed on this location in authentication attempts are not to be performed on this location in
order to improve the user experience, without specifying the order to improve the user experience, without specifying the
redirection on the HTTP level. This header may be used, for example, redirection on the HTTP level. This header can be used, for example,
when there is a central login page for the entire Web application, when there is a central login page for the entire Web application,
and when an explicit user interaction with the Web content is desired and when an explicit user interaction with the Web content is desired
before authentications. The value of this parameter MUST be a token before authentications. The value of this parameter MUST be a token
"true". If the value is incorrect, client MAY ignore this parameter. "true". If the value is incorrect, client MAY ignore this parameter.
This parameter MAY be used with authentication-initiating responses. This parameter MAY be used with authentication-initiating responses.
It can also be contained, although this is NOT RECOMMENDED, in a It can also be contained, although this is NOT RECOMMENDED, in a
positive response with an Optional-WWW-Authenticate header. The positive response with an Optional-WWW-Authenticate header. The
clients MUST ignore this parameter when a response is either clients MUST ignore this parameter when a response is either
successfully-authenticated or intermediately-authenticated. The successfully-authenticated or intermediately-authenticated.
clients SHOULD ignore this parameter when a response is a negatively-
authenticated one (the case is unlikely to happen, though).
When a client receives an authentication-initiating response with When a client receives an authentication-initiating response with
this parameter, if the client has to ask users for authentication this parameter, if the client has to ask users for authentication
credentials, the client will ignore the WWW-Authenticate header credentials, the client will ignore the WWW-Authenticate header
contained in the response and treat the whole response as a normal contained in the response and treat the whole response as a normal
negative 4xx-class response instead of giving the user an opportunity negative 4xx-class response instead of giving the user an opportunity
to start authentication. If the client can process authentication to start authentication. If the client can process authentication
without the user's interaction, this parameter MUST be ignored. without the user's interaction, this parameter MUST be ignored.
This parameter SHOULD NOT be used along with the This parameter SHOULD NOT be used along with the
location-when-unauthenticated parameter. If both were supplied, location-when-unauthenticated parameter. If both were supplied,
clients MAY choose which one is to be honored. clients MAY choose which one is to be honored.
This parameter SHOULD NOT be used as a security measure to prevent This parameter SHOULD NOT be used as a security measure to prevent
authentication attempts, as it is easily circumvented by users. This authentication attempts, as it is easily circumvented by users. This
parameter SHOULD be used solely for improving user experience of Web parameter SHOULD be used solely for improving user experience of Web
applications. applications.
4.5. Location-when-logout parameter 4.5. Location-when-logout parameter
Example:
Authentication-Control: Digest realm="protected space", Authentication-Control: Digest realm="protected space",
location-when-logout="http://www.example.com/byebye.html" location-when-logout="http://www.example.com/byebye.html"
The parameter "location-when-logout" specifies a location where the The parameter "location-when-logout" specifies a location where the
client is to be redirected when the user explicitly requests a client is to be redirected when the user explicitly requests a
logout. The value of this parameter MUST be a string that contains logout. The value of this parameter MUST be a string that contains
an absolute URL location. If a given URL is not absolute, the an URL location. If a given URL is not absolute, the clients MUST
clients MAY consider it a relative URL from the current location. consider it a relative URL from the current location.
This parameter MAY be used with successfully-authenticated responses. This parameter MAY be used with successfully-authenticated responses.
If this parameter is contained in other kinds of responses, the If this parameter is contained in other kinds of responses, the
clients MUST ignore this parameter. clients MUST ignore this parameter.
When the user requests termination of an authentication period, and When the user requests termination of an authentication period, and
if the client currently displays a page supplied by a response with if the client currently displays a page supplied by a response with
this parameter, the client will be redirected to the specified this parameter, the client will be redirected to the specified
location by a new GET request (as if it received a 303 response). location by a new GET request (as if it received a 303 response).
The log-out operation (e.g. erasing memories of user name, The log-out operation (e.g. erasing memories of user name,
authentication credential and all related one-time credentials such authentication credential and all related one-time credentials such
as nonce or keys) SHOULD occur before processing a redirection. as nonce or keys) SHOULD occur before processing a redirection.
When the user requests termination of an authentication period, if When the user requests termination of an authentication period, if
the client supports this parameter but the server response does not the client supports this parameter but the server response does not
contain this parameter, the client's RECOMMENDED behavior is as contain this parameter, the client's RECOMMENDED behavior is as
follows: if the request corresponding to the current content was safe follows: if the request corresponding to the current content was GET
(e.g. GET), reload the page without the authentication credential. method, reload the page without the authentication credential.
If the request was non-idempotent (e.g. POST), keep the current Otherwise, keep the current content as-is and simply forget the
content as-is and simply forget the authentication status. The authentication status. The client SHOULD NOT replay a non-idempotent
client SHOULD NOT replay a non-idempotent request without the user's request without the user's explicit approval.
explicit approval.
Web applications are encouraged to send this parameter with an Web applications are encouraged to send this parameter with an
appropriate value for any responses (except those with redirection appropriate value for any responses (except those with redirection
(3XX) statuses) for non-GET requests. (3XX) statuses) for non-GET requests.
4.6. Logout-timeout parameter 4.6. Logout-timeout parameter
Example:
Authentication-Control: Basic realm="entrance", logout-timeout=300 Authentication-Control: Basic realm="entrance", logout-timeout=300
The parameter "logout-timeout", when contained in a successfully- The parameter "logout-timeout", when contained in a successfully-
authenticated response, means that any authentication credentials and authenticated response, means that any authentication credentials and
state related to the current protection space are to be discarded if state related to the current protection space are to be discarded if
a time specified in this header (in seconds) has passed since from a time specified in this header (in seconds) has passed since from
the time this header was received. The value MUST be an integer. As the time this header was received. The value MUST be an integer. As
a special case, the value 0 means that the client is requested to a special case, the value 0 means that the client is requested to
immediately log-out from the current authentication space and revert immediately log-out from the current authentication space and revert
to an unauthenticated status. This does not, however, mean that the to an unauthenticated status. This does not, however, mean that the
long-term memories for the passwords and passwords-related details long-term memories for the passwords and passwords-related details
(such as the password reminders and auto fill-ins) should be removed. (such as the password reminders and auto fill-ins) should be removed.
If a new timeout value is received for the same authentication space, If a new timeout value is received for the same authentication space,
it cancels the previous timeout and sets a new timeout. it cancels the previous timeout and sets a new timeout.
4.7. Username parameter 4.7. Username parameter
Example:
Authentication-Control: Basic realm="configuration", username="admin" Authentication-Control: Basic realm="configuration", username="admin"
The parameter "username" tells that the only "user name" to be The parameter "username" tells that the only "user name" to be
accepted by the server is the value given in this parameter. This accepted by the server is the value given in this parameter. This
parameter is particularly useful, for example, for routers and other parameter is particularly useful, for example, for routers and other
appliances with a Web configuration interface. appliances with a Web configuration interface.
This parameter MAY be used with authentication-initiating responses This parameter MAY be used with authentication-initiating responses
or negatively-authenticated responses requiring another attempt of or negatively-authenticated responses requiring another attempt of
authentication. The clients MUST ignore this parameter when a authentication. The clients MUST ignore this parameter when a
response is either successfully-authenticated or intermediately- response is either successfully-authenticated or intermediately-
authenticated. authenticated.
If the authentication scheme to be used has a syntax limitation on If the authentication scheme to be used has a syntax limitation on
the allowed user names (e.g. Basic and Digest do not allow colons in the allowed user names (e.g. Basic and Digest do not allow colons in
user names), the specified value MUST follow that limitation. user names), the specified value MUST follow that limitation.
Clients SHOULD ignore any values which do not conform to such Clients SHOULD ignore any values which do not conform to such
limitations. limitations.
Also, if the used authentication scheme requires a specific style of
text preparation for the user name (e.g., PRECIS [RFC7564] string
preparation or Unicode normalization), the server SHOULD send the
values satisfying such requirements (so that clients can use the
given user name as is).
Clients MAY still send any authentication requests with other user Clients MAY still send any authentication requests with other user
names, possibly in vain. Servers are not strictly required to reject names, possibly in vain. Servers are not strictly required to reject
user names other than specified, but doing so will give bad user user names other than specified, but doing so will give bad user
experiences and may confuse users and clients. experiences and may confuse users and clients.
If the used authentication scheme requires a specific style of text 5. Usage examples
preparation for the user name (e.g., PRECIS string preparation or
Unicode normalization), the specified user name SHOULD follow such
requirements.
5. Usage examples (informative)
This section shows some examples for applying this extension to This section shows some examples for applying this extension to
typical websites which are using Forms and cookies for managing typical websites which are using Forms and cookies for managing
authentication and authorization. The content of this section is not authentication and authorization. The content of this section is not
normative and for illustrative purposes only. normative and for illustrative purposes only.
We assume that all features described in the previous sections are In these examples, we assume that there are two kinds of clients (Web
implemented in clients (Web browsers). We also assume that browsers browsers). One kind of these implements all features described in
will have a user interface which allows users to deactivate (log-out the previous sections. We also assume that browsers will have a user
from) current authentication sessions. If this assumption is not interface which allows users to deactivate (log-out from) current
value, the text below provides another approach with de- authentication sessions. The other kind are the "existing"
authentication pages used instead of such a UI. implementations which do not support any of these features.
When not explicitly specified, all settings described below are to be When not explicitly specified, all settings described below are to be
applied with Authentication-Control headers, and these can be sent to applied with Authentication-Control headers, and these can be sent to
clients regardless of the authentication status (these will be clients regardless of the authentication status (these will be
silently ignored whenever not effective). silently ignored whenever not effective).
5.1. Example 1: a portal site 5.1. Example 1: a portal site
This subsection provides an example application for a site whose This subsection provides an example application for a site whose
structure is somewhat similar to conventional portal sites. In structure is somewhat similar to conventional portal sites. In
skipping to change at page 19, line 14 skipping to change at page 20, line 29
will be provided by using (extended) HTTP authentication/ will be provided by using (extended) HTTP authentication/
authorization mechanisms. In some cases, there will be ambiguity on authorization mechanisms. In some cases, there will be ambiguity on
whether some functions are for authorization management or for whether some functions are for authorization management or for
session management. The following hints will be helpful for deciding session management. The following hints will be helpful for deciding
which features to use. which features to use.
o If there is a need to serve multiple sessions for a single user o If there is a need to serve multiple sessions for a single user
using multiple browsers concurrently, use a Cookie for using multiple browsers concurrently, use a Cookie for
distinguishing between sessions for the same user. (C.f. if there distinguishing between sessions for the same user. (C.f. if there
is a need to distinguish sessions in the same browser, HTML5 Web is a need to distinguish sessions in the same browser, HTML5 Web
Storage [W3C.REC-webstorage-20130730] features may be used instead Storage [W3C.REC-webstorage-20130730] features can be used instead
of Cookies.) of Cookies.)
o If a web site is currently deploying a session time-out feature, o If a web site is currently deploying a session time-out feature,
consider who benefits from the feature. In most cases, the main consider who benefits from the feature. In most cases, the main
requirement for such a feature is to protect users from having requirement for such a feature is to protect users from having
their consoles and browsers hijacked (i.e. benefits are on the their consoles and browsers hijacked (i.e. benefits are on the
users' side). In such cases, the time-out features provided in users' side). In such cases, the time-out features provided in
this extension may be used. On the other hand, the requirement is this extension can be used. On the other hand, the requirement is
to protect server's privilege (e.g. when some regulations require to protect server's privilege (e.g. when some regulations require
to limit the time difference between user's two-factor to limit the time difference between user's two-factor
authentication and financial transaction commitment; the authentication and financial transaction commitment; the
requirement is strictly on the servers' side), that should be requirement is strictly on the servers' side), that should be
managed on the server side using Cookies or other session managed on the server side using Cookies or other session
management mechanisms. management mechanisms.
5.4. Parallel deployment with Form/Cookie authentications 5.4. Parallel deployment with Form/Cookie authentications
In some transition periods, sites may need to support both HTTP-layer In some transition periods, sites can need to support both HTTP-layer
and form-based authentication. The following example shows one way and form-based authentication. The following example shows one way
to achieve that. to achieve that.
o If Cookies are used even for HTTP-authenticated users, each o If Cookies are used even for HTTP-authenticated users, each
session determined by Cookies should identify which authentication session determined by Cookies SHOULD identify which authentication
has been used for the session. has been used for the session.
o First, set up any of the above settings for enabling HTTP-layer o First, set up any of the above settings for enabling HTTP-layer
authentication. authentication.
o For unauthenticated users, add the following things to the Web o For unauthenticated users, add the following things to the Web
pages, unless the client supports this extension and HTTP-level pages, unless the client supports this extension and HTTP-level
authentication. authentication.
* For non-mandatory authenticated pages, put a link to Form-based * For non-mandatory authenticated pages, put a link to Form-based
authenticated pages. authenticated pages.
* For mandatory authenticated pages, either put a link to Form- * For mandatory authenticated pages, either put a link to Form-
based authenticated pages, or put a HTML-level redirection based authenticated pages, or put a HTML-level redirection
(using META element) to such pages. (using >META http-equiv="refresh" ...< element) to such pages.
o In Form-based authenticated pages, if users are not authenticated, o In Form-based authenticated pages, if users are not authenticated,
the page may have a diversion for HTTP-level authentication by the page can provide a redirection for HTTP-level authentication
"location-when-unauthenticated" setting. by "location-when-unauthenticated" setting.
o Users are identified to authorization and content customization by o Users are identified to authorization and content customization by
the following logic. the following logic.
* First, check the result of the HTTP-level authentication. If * First, check the result of the HTTP-level authentication. If
there is a Cookie session tied to a specific user, both should there is a Cookie session tied to a specific user, both should
match. match.
* If the user is not authenticated on the HTTP-level, use the * If the user is not authenticated on the HTTP-level, use the
conventional Form-based method to determine the user. conventional Form-based method to determine the user.
* If there is a Cookie tied to HTTP authentication, but there is * If there is a Cookie tied to HTTP authentication, but there is
no corresponding HTTP authentication result, that session will no corresponding HTTP authentication result, that session will
be discarded (because it means that authentication is be discarded (because it means that authentication is
deactivated by the corresponding user). deactivated by the corresponding user).
6. Methods to extend this protocol 6. Methods to extend this protocol
If a private extension to this protocol is implemented, it MUST use If a private extension to this protocol is implemented, it MUST use
the extension-param to avoid conflicts with this protocol and other the extension-param to avoid conflicts with this protocol and any
future official extensions. other extensions. (Standardized or being-standardized extensions MAY
use either bare-tokens or extension-tokens.)
When bare-tokens are used in this protocol, these MUST be allocated When bare-tokens are used in this protocol, these MUST be allocated
by IANA. Any tokens used for non-private, non-experimental by IANA. Any tokens used for non-private, non-experimental
parameters are RECOMMENDED to be registered to IANA, regardless of parameters are RECOMMENDED to be registered to IANA, regardless of
the kind of tokens used. the kind of tokens used.
Extension-tokens MAY be freely used for any non-standard, private, Extension-tokens MAY be freely used for any non-standard, private,
and/or experimental uses. An extension-tokens MUST use the format and/or experimental uses. An extension-tokens MUST use the format
"-<bare-token>.<domain-name>", where <domain-name> is a validly "-<bare-token>.<domain-name>", where <domain-name> is a validly
registered (sub-)domain name on the Internet owned by the party who registered (sub-)domain name on the Internet owned by the party who
defines the extensions. Unknown parameter names are to be ignored defines the extensions. Any unknown parameter name is to be ignored
regardless of whether it is extension-tokens or bare-tokens. regardless of whether it is an extension-token or a bare-token.
7. IANA Considerations 7. IANA Considerations
This document defines two new entries for the "Permanent Message This document defines two new entries for the "Permanent Message
Header Field Names" registry. Header Field Names" registry.
+---------------------------+----------+----------------------------+ +---------------------------+----------+----------------------------+
| Header Field Name | Protocol | Specification | | Header Field Name | Protocol | Specification |
+---------------------------+----------+----------------------------+ +---------------------------+----------+----------------------------+
| Optional-WWW-Authenticate | http | Section 3 of this document | | Optional-WWW-Authenticate | http | Section 3 of this document |
| Authentication-Control | http | Section 4 of this document | | Authentication-Control | http | Section 4 of this document |
+---------------------------+----------+----------------------------+ +---------------------------+----------+----------------------------+
This document also establishes a registry for HTTP authentication This document also establishes a registry for HTTP authentication
control parameters. The registry manages a case-insensitive ASCII control parameters. The registry manages case-insensitive ASCII
strings. The string MUST follow the extensive-token syntax defined strings. The string MUST follow the extensive-token syntax defined
in Section 2.2. in Section 2.2.
To acquire registered tokens, a specification for the use of such To acquire registered tokens, a specification for the use of such
tokens MUST be available as a publicly-accessible documents, as tokens MUST be available as a publicly-accessible documents, as
outlined as "Specification Required" level in [RFC5226]. outlined as "Specification Required" level in [RFC5226].
Registrations for authentication algorithms are required to include a Registrations for authentication control parameters are required to
description of the control extension. New registrations are advised include a description of the control extension. New registrations
to provide the following information: are advised to provide the following information:
o Token: a token used in HTTP headers for identifying the algorithm. o Token: a token used in HTTP headers for identifying the algorithm.
o Specification: A reference for a specification defining the o Specification: A reference for a specification defining the
algorithm. algorithm.
The initial content of this registry is as follows: The initial content of this registry is as follows:
+-------------------------------+------------------------------+ +-------------------------------+------------------------------+
| Token | Specification | | Token | Specification |
skipping to change at page 22, line 7 skipping to change at page 23, line 28
The purpose of the log-out timeout feature in the Authentication- The purpose of the log-out timeout feature in the Authentication-
control header is to protect users of clients from impersonation control header is to protect users of clients from impersonation
caused by an attacker having access to the same console. The server caused by an attacker having access to the same console. The server
application implementer SHOULD be aware that the directive may always application implementer SHOULD be aware that the directive may always
be ignored by either malicious clients or clients not supporting this be ignored by either malicious clients or clients not supporting this
extension. If the purpose of introducing a timeout for an extension. If the purpose of introducing a timeout for an
authentication period is to protect server-side resources, this authentication period is to protect server-side resources, this
protection MUST be implemented by other means such as HTTP Cookies protection MUST be implemented by other means such as HTTP Cookies
[RFC6265]. [RFC6265].
All parameters in Authentication-Control header SHOULD NOT be used All parameters in the Authentication-Control header SHOULD NOT be
for any security-enforcement purposes. Server-side applications MUST used for any security-enforcement purposes. Server-side applications
always consider that the header may be either ignored by clients or MUST NOT assume that the header will be honored by clients and users.
even bypassed by users.
The "username" parameter may reveal sensitive information about the The "username" parameter sometimes reveals sensitive information
HTTP server and its configurations, useful for security attacks. The about the HTTP server and its configurations, useful for security
use of the "username" parameter SHOULD be limited to cases where the attacks. The use of the "username" parameter SHOULD be limited to
all of the following conditions are met: cases where the all of the following conditions are met:
(1) the valid user name is pre-configured and not modifiable (such (1) the valid user name is pre-configured and not modifiable (such
as root, admin or similar ones); as root, admin or similar ones);
(2) the valid user name for such an appliance is publicly known (for (2) the valid user name for such an appliance is publicly known (for
example, written in a manual); and example, written in a manual document); and
(3) either the valid user name for the server is easily guessable by (3) either the valid user name for the server is easily guessable by
other means (for example, from the model number shown in an other means (for example, from the model number shown in an
unauthenticated page), or the server is only accessible from unauthenticated page), or the server is only accessible from
limited networks. limited networks.
Most importantly, the "username" parameter SHOULD NOT be used in any Most importantly, the "username" parameter SHOULD NOT be used in any
case when the valid user names are configured by users or case when the valid user names can be changed by users or
administrators. administrators.
9. References 9. References
9.1. Normative References 9.1. Normative References
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, DOI 10.17487/ Requirement Levels", BCP 14, RFC 2119, DOI 10.17487/
RFC2119, March 1997, RFC2119, March 1997,
<http://www.rfc-editor.org/info/rfc2119>. <http://www.rfc-editor.org/info/rfc2119>.
[RFC5226] Narten, T. and H. Alvestrand, "Guidelines for Writing an [RFC5226] Narten, T. and H. Alvestrand, "Guidelines for Writing an
IANA Considerations Section in RFCs", BCP 26, RFC 5226, IANA Considerations Section in RFCs", BCP 26, RFC 5226,
DOI 10.17487/RFC5226, May 2008, DOI 10.17487/RFC5226, May 2008,
<http://www.rfc-editor.org/info/rfc5226>. <http://www.rfc-editor.org/info/rfc5226>.
[RFC5234] Crocker, D., Ed. and P. Overell, "Augmented BNF for Syntax
Specifications: ABNF", STD 68, RFC 5234, DOI 10.17487/
RFC5234, January 2008,
<http://www.rfc-editor.org/info/rfc5234>.
[RFC5987] Reschke, J., "Character Set and Language Encoding for [RFC5987] Reschke, J., "Character Set and Language Encoding for
Hypertext Transfer Protocol (HTTP) Header Field Hypertext Transfer Protocol (HTTP) Header Field
Parameters", RFC 5987, DOI 10.17487/RFC5987, August 2010, Parameters", RFC 5987, DOI 10.17487/RFC5987, August 2010,
<http://www.rfc-editor.org/info/rfc5987>. <http://www.rfc-editor.org/info/rfc5987>.
[RFC7230] Fielding, R., Ed. and J. Reschke, Ed., "Hypertext Transfer [RFC7230] Fielding, R., Ed. and J. Reschke, Ed., "Hypertext Transfer
Protocol (HTTP/1.1): Message Syntax and Routing", Protocol (HTTP/1.1): Message Syntax and Routing",
RFC 7230, DOI 10.17487/RFC7230, June 2014, RFC 7230, DOI 10.17487/RFC7230, June 2014,
<http://www.rfc-editor.org/info/rfc7230>. <http://www.rfc-editor.org/info/rfc7230>.
[RFC7235] Fielding, R., Ed. and J. Reschke, Ed., "Hypertext Transfer [RFC7235] Fielding, R., Ed. and J. Reschke, Ed., "Hypertext Transfer
Protocol (HTTP/1.1): Authentication", RFC 7235, Protocol (HTTP/1.1): Authentication", RFC 7235,
DOI 10.17487/RFC7235, June 2014, DOI 10.17487/RFC7235, June 2014,
<http://www.rfc-editor.org/info/rfc7235>. <http://www.rfc-editor.org/info/rfc7235>.
9.2. Informative References 9.2. Informative References
[I-D.ietf-httpauth-mutual] [I-D.ietf-httpauth-mutual]
Oiwa, Y., Watanabe, H., Takagi, H., Maeda, K., Hayashi, Oiwa, Y., Watanabe, H., Takagi, H., Maeda, K., Hayashi,
T., and Y. Ioku, "Mutual Authentication Protocol for T., and Y. Ioku, "Mutual Authentication Protocol for
HTTP", draft-ietf-httpauth-mutual-07 (work in progress), HTTP", draft-ietf-httpauth-mutual-08 (work in progress),
January 2016. July 2016.
[RFC6265] Barth, A., "HTTP State Management Mechanism", RFC 6265, [RFC6265] Barth, A., "HTTP State Management Mechanism", RFC 6265,
DOI 10.17487/RFC6265, April 2011, DOI 10.17487/RFC6265, April 2011,
<http://www.rfc-editor.org/info/rfc6265>. <http://www.rfc-editor.org/info/rfc6265>.
[RFC7564] Saint-Andre, P. and M. Blanchet, "PRECIS Framework:
Preparation, Enforcement, and Comparison of
Internationalized Strings in Application Protocols",
RFC 7564, DOI 10.17487/RFC7564, May 2015,
<http://www.rfc-editor.org/info/rfc7564>.
[W3C.REC-webstorage-20130730] [W3C.REC-webstorage-20130730]
Hickson, I., "Web Storage", World Wide Web Consortium Hickson, I., "Web Storage", World Wide Web Consortium
Recommendation REC-webstorage-20130730, July 2013, Recommendation REC-webstorage-20130730, July 2013,
<http://www.w3.org/TR/2013/REC-webstorage-20130730>. <http://www.w3.org/TR/2013/REC-webstorage-20130730>.
Appendix A. (Informative) Applicability of features for each messages Appendix A. (Informative) Applicability of features for each messages
This section provides a cross-reference table showing the This section provides a cross-reference table showing the
applicability of the features provided in this specification to each applicability of the features provided in this specification to each
kind of responses described in Section 2.1. The table provided in kind of responses described in Section 2.1. The table provided in
skipping to change at page 24, line 4 skipping to change at page 25, line 33
| Optional auth. | O | n | N | N | | Optional auth. | O | n | N | N |
| auth-style | O | - | - | O | | auth-style | O | - | - | O |
| loc.-when-unauth. | O | I | I | i | | loc.-when-unauth. | O | I | I | i |
| no-auth | O | I | I | i | | no-auth | O | I | I | i |
| loc.-when-logout | - | O | - | - | | loc.-when-logout | - | O | - | - |
| logout-timeout | - | O | - | - | | logout-timeout | - | O | - | - |
| username | O | - | - | O | | username | O | - | - | O |
+-------------------+-------+----------+-----------+------+ +-------------------+-------+----------+-----------+------+
Legends: Legends:
O = MAY contain; n = SHOULD NOT contain; N = MUST NOT contain O = MAY contain; n = SHOULD NOT contain; N = MUST NOT contain
i = SHOULD be ignored; I = MUST be ignored; i = SHOULD be ignored; I = MUST be ignored;
- = meaningless (to be ignored) - = meaningless (to be ignored)
Appendix B. (Informative) Draft Change Log Appendix B. (Informative) Draft Change Log
[To be removed on final publication] [To be removed on final publication]
B.1. Changes in Httpauth WG Revision 06 B.1. Changes in Httpauth WG Revision 07
o WGLC comments are reflected to the text.
B.2. Changes in Httpauth WG Revision 06
o Several comments from reviewers are reflected to the text. o Several comments from reviewers are reflected to the text.
B.2. Changes in Httpauth WG Revision 05 B.3. Changes in Httpauth WG Revision 05
o Authors' addresses updated. o Authors' addresses updated.
B.3. Changes in Httpauth WG revision 04 B.4. Changes in Httpauth WG revision 04
o IANA consideration section added. o IANA consideration section added.
B.4. Changes in Httpauth WG revision 03 B.5. Changes in Httpauth WG revision 03
o Adopting RFC 5987 extended syntax for non-ASCII parameter values. o Adopting RFC 5987 extended syntax for non-ASCII parameter values.
B.5. Changes in Httpauth WG revision 02 B.6. Changes in Httpauth WG revision 02
o Added realm parameter. o Added realm parameter.
o Added username parameter. We acknowledge Michael Sweet's proposal o Added username parameter. We acknowledge Michael Sweet's proposal
for including this to the Basic authentication. for including this to the Basic authentication.
B.6. Changes in Httpauth WG revision 01 B.7. Changes in Httpauth WG revision 01
o Clarification on peers' responsibility about handling of relative o Clarification on peers' responsibility about handling of relative
URLs. URLs.
o Automatic reloading should be allowed only on safe methods, not o Automatic reloading should be allowed only on safe methods, not
always on idempotent methods. always on idempotent methods.
B.7. Changes in Httpauth revision 00 and HttpBis revision 00 B.8. Changes in Httpauth revision 00 and HttpBis revision 00
None. None.
B.8. Changes in revision 02 B.9. Changes in revision 02
o Added usage examples. o Added usage examples.
B.9. Changes in revision 01 B.10. Changes in revision 01
o Syntax notations and parsing semantics changed to match httpbis o Syntax notations and parsing semantics changed to match httpbis
style. style.
B.10. Changes in revision 00 B.11. Changes in revision 00
o Separated from HTTP Mutual authentication proposal (-09). o Separated from HTTP Mutual authentication proposal (-09).
o Adopting httpbis works as a referencing point to HTTP. o Adopting httpbis works as a referencing point to HTTP.
o Generalized, now applicable for all HTTP authentication schemes. o Generalized, now applicable for all HTTP authentication schemes.
o Added "no-auth" and "auth-style" parameters. o Added "no-auth" and "auth-style" parameters.
o Loosened standardization requirements for parameter-name tokens o Loosened standardization requirements for parameter-name tokens
 End of changes. 85 change blocks. 
210 lines changed or deleted 295 lines changed or added

This html diff was produced by rfcdiff 1.45. The latest version is available from http://tools.ietf.org/tools/rfcdiff/