Internet DRAFT - draft-ietf-httpauth-extension
draft-ietf-httpauth-extension
HTTPAUTH Working Group Y. Oiwa
Internet-Draft H. Watanabe
Intended status: Experimental H. Takagi
Expires: November 23, 2016 ITRI, AIST
T. Hayashi
Lepidum
Y. Ioku
Individual
May 22, 2016
HTTP Authentication Extensions for Interactive Clients
draft-ietf-httpauth-extension-06
Abstract
This document specifies extensions of HTTP authentication framework
for interactive clients. Recently, fundamental features of HTTP-
level authentication are insufficient for complex requirements of
various Web-based applications. This forces these applications to
implement their own authentication frameworks using HTML Forms and
other means, which becomes one of the hurdles against introducing
secure authentication mechanisms handled jointly by servers and user-
agent. The extended framework fills gaps between Web application
requirements and HTTP authentication provisions to solve the above
problems, while maintaining compatibility against existing Web and
non-Web uses of HTTP authentications.
Status of this Memo
This Internet-Draft is submitted in full conformance with the
provisions of BCP 78 and BCP 79.
Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF). Note that other groups may also distribute
working documents as Internet-Drafts. The list of current Internet-
Drafts is at http://datatracker.ietf.org/drafts/current/.
Internet-Drafts are draft documents valid for a maximum of six months
and may be updated, replaced, or obsoleted by other documents at any
time. It is inappropriate to use Internet-Drafts as reference
material or to cite them other than as "work in progress."
This Internet-Draft will expire on November 23, 2016.
Copyright Notice
Copyright (c) 2016 IETF Trust and the persons identified as the
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document authors. All rights reserved.
This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents
(http://trustee.ietf.org/license-info) in effect on the date of
publication of this document. Please review these documents
carefully, as they describe your rights and restrictions with respect
to this document. Code Components extracted from this document must
include Simplified BSD License text as described in Section 4.e of
the Trust Legal Provisions and are provided without warranty as
described in the Simplified BSD License.
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 4
1.1. Terminology . . . . . . . . . . . . . . . . . . . . . . . 4
2. Definitions . . . . . . . . . . . . . . . . . . . . . . . . . 5
2.1. Terms for describing authentication protocol flow . . . . 5
2.2. Syntax Notation . . . . . . . . . . . . . . . . . . . . . 7
3. Optional Authentication . . . . . . . . . . . . . . . . . . . 8
4. Authentication-Control header . . . . . . . . . . . . . . . . 9
4.1. Non-ASCII extended header parameters . . . . . . . . . . . 11
4.2. Auth-style parameter . . . . . . . . . . . . . . . . . . . 12
4.3. Location-when-unauthenticated parameter . . . . . . . . . 13
4.4. No-auth parameter . . . . . . . . . . . . . . . . . . . . 13
4.5. Location-when-logout parameter . . . . . . . . . . . . . . 14
4.6. Logout-timeout parameter . . . . . . . . . . . . . . . . . 15
4.7. Username parameter . . . . . . . . . . . . . . . . . . . . 15
5. Usage examples (informative) . . . . . . . . . . . . . . . . . 16
5.1. Example 1: a portal site . . . . . . . . . . . . . . . . . 16
5.1.1. Case 1: a simple application . . . . . . . . . . . . . 17
5.1.2. Case 2: specific action required on log-out . . . . . 17
5.1.3. Case 3: specific page displayed before log-in . . . . 18
5.2. Example 2: authenticated user-only sites . . . . . . . . . 18
5.3. When to use Cookies . . . . . . . . . . . . . . . . . . . 18
5.4. Parallel deployment with Form/Cookie authentications . . . 19
6. Methods to extend this protocol . . . . . . . . . . . . . . . 20
7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 20
8. Security Considerations . . . . . . . . . . . . . . . . . . . 21
9. References . . . . . . . . . . . . . . . . . . . . . . . . . . 22
9.1. Normative References . . . . . . . . . . . . . . . . . . . 22
9.2. Informative References . . . . . . . . . . . . . . . . . . 23
Appendix A. (Informative) Applicability of features for each
messages . . . . . . . . . . . . . . . . . . . . . . 23
Appendix B. (Informative) Draft Change Log . . . . . . . . . . . 24
B.1. Changes in Httpauth WG Revision 06 . . . . . . . . . . . . 24
B.2. Changes in Httpauth WG Revision 05 . . . . . . . . . . . . 24
B.3. Changes in Httpauth WG revision 04 . . . . . . . . . . . . 24
B.4. Changes in Httpauth WG revision 03 . . . . . . . . . . . . 24
B.5. Changes in Httpauth WG revision 02 . . . . . . . . . . . . 24
B.6. Changes in Httpauth WG revision 01 . . . . . . . . . . . . 24
B.7. Changes in Httpauth revision 00 and HttpBis revision 00 . 24
B.8. Changes in revision 02 . . . . . . . . . . . . . . . . . . 24
B.9. Changes in revision 01 . . . . . . . . . . . . . . . . . . 25
B.10. Changes in revision 00 . . . . . . . . . . . . . . . . . . 25
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 25
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1. Introduction
The document proposes several extensions to the current HTTP
authentication framework, to provide functionality comparable with
current widely-used form-based Web authentication. A majority of the
recent websites on the Internet use custom application-layer
authentication implementations using Web forms. The reasons for
these may vary, but many people believe that the current HTTP Basic
and Digest authentication methods do not have enough functionality
(including good user interfaces) to support most realistic Web-based
applications. However, this method is very weak against phishing and
other attacks, because all behavior of the authentication is
controlled from the server-side application. This makes it really
hard to implement any cryptographically strong authentication
mechanisms into Web systems. To overcome this problem, we need to
"modernize" the HTTP authentication framework so that better client-
controlled secure methods can be used with Web applications. The
extensions proposed in this document include:
o optional authentication on HTTP (Section 3),
o log out from both server and client side (Section 4), and
o finer control for redirection depending on authentication status
(Section 4).
1.1. Terminology
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and
"OPTIONAL" in this document are to be interpreted as described in
[RFC2119].
The terms "encouraged" and "advised" are used for suggestions that do
not constitute "SHOULD"-level requirements. People MAY freely choose
not to include the suggested items regarding [RFC2119], but complying
with those suggestions would be a best practice; it will improve the
security, interoperability, and/or operational performance.
This document distinguishes the terms "client" and "user" in the
following way: A "client" is an entity understanding and talking HTTP
and the specified authentication protocol, usually computer software;
a "user" is a (usually natural) person who wants to access data
resources using "a client".
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2. Definitions
2.1. Terms for describing authentication protocol flow
HTTP Authentication defined in [RFC7235] may involve several pairs of
HTTP requests/responses. Throughout this document, the following
terms are used to categorize those messages: for requests,
1) A non-authenticating request is a request not attempting any
authentication: a request without any Authorization header.
2) An authenticating request is the opposite: a request with an
Authorization header.
For responses,
1) A non-authenticated response is a response which does not involve
any HTTP authentication. It does not contain any WWW-Authenticate
or Authentication-Info header.
Servers send this response when the requested resource is not
protected by an HTTP authentication mechanism. In context of this
specification, non-authentication-related negative responses (e.g.
403 and 404) are also considered non-authenticated responses.
(See note on successfully-authenticated responses below for some
ambiguous cases.)
2) An authentication-initializing response is a response which
requires or allows clients to start authentication attempts.
Servers send this response when the requested resource is
protected by HTTP authentication mechanism, and the request meets
one of the following cases:
* The request is a non-authenticating request, or
* The request contained an authentication trial directed to a
protection space (realm) other than the one the server
expected.
The server will specify the protection space for authentication in
this response.
Upon receiving this response, the client's behavior is further
divided to two possible cases.
* If the client has no prior knowledge on authentication
credentials (e.g. a user-name and a password) related to the
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requested protection space, the protocol flow terminates and
the client will ask the user to provide authentication
credentials,
* On the other hand, if client already has enough authentication
credentials to the requested protection space, the client will
automatically send an authenticating request. Such cases often
occur when the client did not know beforehand that the current
request-URL requires authentication.
3) A successfully-authenticated response is a response for an
authenticating request meaning that the authentication attempt was
granted. (Note: if the authentication scheme used does not use an
Authentication-Info header, it may be indistinguishable from a
non-authenticated response.)
4) An intermediate authenticating response is a response for an
authenticating request which requires more reaction by the client
software without involving users. Such a response is required
when an authentication scheme requires two or more round-trip
messages to perform authentication, or when an authentication
scheme uses some speculative short-cut method (such as uses of
cached shared secrets) and it failed.
5) A negatively-authenticated response is a response for an
authenticating request which means that the authentication attempt
was declined and can not continue without a different set of
authentication credentials. Clients typically erase memory of the
active credentials and ask the user for other ones.
Usually the format of these responses are as same as the one for
authentication-initializing responses. Client can distinguish
negatively-authenticated responses from authentication-
initializing responses by comparing the protection spaces
contained in the request and in the response.
Figure 1 shows a state diagram of generic HTTP authentication with
the above message categorization. Note that many authentication
schemes use only a subset of the transitions described on the
diagram. Labels in the figure show the abbreviated names of response
types.
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=========== -----------------
NEW REQUEST ( UNAUTHENTICATED )
=========== -----------------
| ^ non-auth.
v | response
+----------------------+ NO +-------------+
| The requested URI |--------------------------->| send normal |
| known to be auth'ed? | ---------------->| request |
+----------------------+ / +-------------+
YES | / initializing|
v / |
+------------------+ NO / |
| Can auth-req.(*1)|--------- |
| be constructed? | |
+------------------+ |
YES | initializing |
| ---------------------------------------. |
| / v v
| | ---------------- NO +-----------+
| | ( AUTH-REQUESTED )<------|credentials|
| | ---------------- | known? |
v | +-----------+
+-----------+ negative ------------- negative |YES
| send |---------->( AUTH-FAILED )<---------, |
/| auth-req | ------------- | |
/ +-----------+\ | v
| \ \ intermediate +-----------+
| \ -------------------------------->| send |
| \ | auth-req |
| non-auth. \successful successful +-----------+
| response (*2) \ / | ^
v \ / | |
----------------- \ -------------- / `----'
( UNAUTHENTICATED ) ----->( AUTH-SUCCEED )<---- intermediate
----------------- --------------
Figure 1: Generic state diagram for HTTP authentication
Note: (*1) For example, "Digest" scheme requires server-provided
nonce to construct client-side challenges.
(*2) In "Basic" and some others, this cannot be distinguished from a
successfully-authenticated response.
2.2. Syntax Notation
This specification uses an extended BNF syntax defined in [RFC7230].
The following syntax definitions are quoted from [RFC7230] and
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[RFC7235]: auth-scheme, quoted-string, auth-param, SP, BWS, header-
field, and challenge. It also uses the convention of using header
names for specifying the syntax of header values.
Additionally, this specification uses the following syntax
definitions as a refinement for token and the right-hand-side of
auth-param in [RFC7235]. (Note: these definitions are consistent
with those in [I-D.ietf-httpauth-mutual].)
bare-token = 1*(%x30-39 / %x41-5A / %x61-7A / "-" / "_")
extension-token = "-" bare-token 1*("." bare-token)
extensive-token = bare-token / extension-token
integer = "0" / (%x31-39 *%x30-39) ; no leading zeros
Figure 2: the BNF syntax for common notations
Extensive-tokens are used in this protocol where the set of
acceptable tokens may include private extensions. Any private
extensions of this protocol MUST use extension-tokens with the 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
The Optional-WWW-Authenticate header enables a non-mandatory
authentication, which is not possible under the current HTTP
authentication mechanism. In several Web applications, users can
access the same contents as both a guest user and an authenticated
user. In most Web applications, This functionality is implemented
using HTTP cookies [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
Optional-WWW-Authenticate header as a replacement of a 401 response
when it the response is authentication-initializing. The
Optional-WWW-Authenticate header MUST NOT sent on 401 responses (i.e.
a usual WWW-Authenticate header MUST be used on 401 responses.)
HTTP/1.1 200 OK
Optional-WWW-Authenticate: Basic realm="xxxx"
Optional-WWW-Authenticate = 1#challenge
Figure 3: BNF syntax for Optional-WWW-Authenticate header
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The challenges contained in the Optional-WWW-Authenticate header are
the same as those for a 401 responses corresponding to the same
request. For authentication-related matters, an optional
authentication request will have the same meaning as a 401 message
with a corresponding WWW-Authenticate header (as an authentication-
initializing response). (The behavior for other matters, such as
caching, MAY be different between the optional authentication and 401
messages.)
A response with an Optional-WWW-Authenticate header SHOULD be
returned from the server only when the request is either non-
authenticated or authenticating to a wrong (not the server's
expected) protection space. If a response is either an intermediate
or a negative response to a client's authentication attempt, the
server MUST respond with a 401 status response with a
WWW-Authenticate header instead. Failure to comply with this rule
will render clients unable to distinguish authentication successes
and failures.
The server is NOT RECOMMENDED to include an Optional-WWW-Authenticate
header in a positive response when a client's authentication attempt
succeeds.
Whenever an authentication scheme supports servers sending some
parameter which gives a hint of the URL space for the corresponding
protection space for the same realm (e.g. "path" or "domain"),
servers requesting non-mandatory authentication SHOULD send such
parameter with the response. Clients supporting non-mandatory
authentication MUST recognize the parameter, and MUST send a request
with an appropriate authentication credential in an Authorization
header for any URI inside the specified paths.
Support of this header is OPTIONAL; Clients MAY also choose any set
of authentication schemes for which optional authentication is
supported (in other words, its support MAY be scheme-dependent).
However, some authentication schemes MAY require mandatory/
recommended support for this header, so that server-side applications
MAY assume that clients supporting such schemes are likely to support
the extension as well.
4. Authentication-Control header
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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
/ extensive-token "*" BWS "=" BWS ext-value
ext-value = <see RFC 5987, Section 3.2>
Figure 4: the BNF syntax for the Authentication-Control header
The Authentication-Control header provides a more precise control of
the client behavior for Web applications using an HTTP authentication
protocol. This header is supposed to be generated in the application
layer, as opposed to WWW-Authenticate headers which will usually be
generated by the Web servers.
Support of this header is OPTIONAL, and clients MAY choose any subset
of these parameters to be supported. The set of supported parameters
MAY also be authentication scheme-dependent. However, some
authentication schemes MAY require mandatory/recommended support for
some or all of the features provided in this header.
The Authentication-Control header contains one or more
"authentication control entries" each of which corresponds to a
single realm for a specific authentication scheme. If the
auth-scheme specified for an entry supports the HTTP "realm" feature,
that entry MUST contain the "realm" parameter. If not, the entry
MUST NOT contain the "realm" parameter.
Among the multiple entries in the header, the meaningful entries in
the header are those corresponding to an auth-scheme and a realm (if
any), for which "the authentication process is being performed, or
going to be performed". In more detail,
(1) If the response is either an authentication-initializing
response or a negatively-authenticated response, there may be
multiple challenges in the WWW-Authenticate header (or the
Optional-WWW-Authenticate header defined in this extension),
each of which corresponds to a different scheme and realm. In
this case, the client has a choice on the scheme and realm they
will use to authenticate. Only the entry in the
&Authentication-Control; header corresponding to that scheme and
realm are meaningful.
(2) If the response is either an intermediate authenticating
response or a successfully-authenticated response, the scheme
and realm given in the Authorization header of the HTTP request
will determine the currently-ongoing authentication process.
Only the entry corresponding to that scheme and realm are
meaningful.
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The server MAY send an Authentication-Control header containing non-
meaningful entries. The client MUST ignore all non-meaningful
entries it received.
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.
Clients MUST ignore any unknown parameters contained in this header.
The entries for the same auth-scheme and the realm MUST NOT contain
duplicated parameters for the same name.
The type of parameter value depends on the parameter name as defined
in the following subsections. Regardless of the type, however, the
recipients SHOULD accept both quoted and unquoted representations of
values as defined in HTTP. If the parameter is defined to have a
string value, implementations SHOULD send the parameter in a quoted
form or an ext-value form (see Section 4.1). If the parameter is
defined as a token (or similar) or an integer, the value SHOULD
follow the corresponding ABNF syntax after possible unquoting of the
quoted-string value (as defined in HTTP), and SHOULD be sent in a
unquoted form.
Server-side applications SHOULD be aware that any parameters
contained in this header MAY be ignored by clients. Also, even when
a client accepts this header, users may always be able to circumvent
the semantics of this header. Therefore, if this header is used for
security purposes, its use MUST be limited to providing some non-
fundamental additional security measures valuable for end-users (such
as client-side log-out for protecting against console takeover).
Server-side applications MUST NOT rely on the use of this header for
protecting server-side resources.
Note: The header syntax allows servers to specify Authentication-
Control for multiple authentication schemes, either as multiple
occurrences of this header or as a combined single header (see
Section 3.2.2 of [RFC7230] for rationale). The same care as for
parsing multiple authentication challenges SHALL be taken.
4.1. Non-ASCII extended header parameters
Parameters contained in the Authentication-Control header MAY be
extended to ISO 10646-1 values using the framework described in
[RFC5987]. All servers and clients MUST be capable of receiving and
sending values encoded in [RFC5987] syntax.
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
5987 MUST NOT be used in this case.
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If a value (except the "realm" header) contains one or more non-ASCII
characters, the parameter SHOULD be sent using the ext-value syntax
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
omitted (have an empty value). The same parameter MUST NOT be sent
more than once, regardless of the used syntax.
For example, a parameter "username" with value "Renee of France"
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-
8''Ren%C3%89e%20of%20France > instead.
4.2. Auth-style parameter
Authentication-Control: Digest realm="protected space",
auth-style=modal
The parameter "auth-style" specifies the server's preferences for
user interface behavior for user authentication. This parameter can
be included in any kind of response, however, it is only meaningful
for either authentication-initializing or negatively-authenticated
responses. The value of this parameter MUST be one of the bare-
tokens "modal" or "non-modal". When the Optional-WWW-Authenticate
header is used, the value of this parameter MUST be disregarded and
the value "non-modal" is implied.
The value "modal" means that the server thinks the content of the
response (body and other content-related headers) is valuable only
for users refusing the authentication request. The clients are
expected to ask the user for a password before processing the
content. This behavior is common for most of the current
implementations of Basic and Digest authentication schemes.
The value "non-modal" means that the server thinks the content of the
response (body and other content-related headers) is valuable for
users before processing an authentication request. The clients are
expected to first process the content and then provide users the
opportunity to perform authentication.
The default behavior for clients is implementation-dependent, and
clients MAY choose different defaults for different authentication
schemes. The proposed default behavior is "modal" for all
authentication schemes, but specifications for authentication schemes
MAY propose a different default.
The above two different methods of authentication may introduce a
observable difference of semantics when the response contains state-
changing side effects; for example, it may change whether Cookie
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headers [RFC6265] in 401 responses are processed or not. However,
the server applications SHOULD NOT depend on both existence and non-
existence of such side effects.
4.3. Location-when-unauthenticated parameter
Authentication-Control: Mutual realm="auth-space-1",
location-when-unauthenticated="http://www.example.com/login.html"
The parameter "location-when-unauthenticated" specifies a location
where any unauthenticated clients should be redirected to. This
header may be used, for example, when there is a central login page
for the entire Web application. The value of this parameter is a
string that contains an absolute URL location. Senders MUST always
send an absolute URL location. If a received URL is not absolute,
the clients SHOULD either ignore it or consider it a relative URL
from the current location.
This parameter MAY be used with a 401 response for an authentication-
initializing response. It can also be contained, although this is
NOT RECOMMENDED, in a positive response with an
Optional-WWW-Authenticate header. The clients MUST ignore this
parameter when a response is either successfully-authenticated or
intermediately-authenticated. The 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
this parameter, if the client has to ask users for authentication
credentials, the client will treat the entire response as if it were
a 303 "See Other" response with a Location header that contains the
value of this parameter (i.e., client will be redirected to the
specified location with a GET request). Unlike a normal 303
response, if the client can process authentication without the user's
interaction, this parameter MUST be ignored.
4.4. No-auth parameter
Authentication-Control: Basic realm="entrance", no-auth=true
The parameter "no-auth" is a variant of the
location-when-unauthenticated parameter; it specifies that new
authentication attempts are not to be performed on this location in
order to improve the user experience, without specifying the
redirection on the HTTP level. This header may be used, for example,
when there is a central login page for the entire Web application,
and when an explicit user interaction with the Web content is desired
before authentications. The value of this parameter MUST be a token
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"true". If the value is incorrect, client MAY ignore this parameter.
This parameter MAY be used with authentication-initiating responses.
It can also be contained, although this is NOT RECOMMENDED, in a
positive response with an Optional-WWW-Authenticate header. The
clients MUST ignore this parameter when a response is either
successfully-authenticated or intermediately-authenticated. The
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
this parameter, if the client has to ask users for authentication
credentials, the client will ignore the WWW-Authenticate header
contained in the response and treat the whole response as a normal
negative 4xx-class response instead of giving the user an opportunity
to start authentication. If the client can process authentication
without the user's interaction, this parameter MUST be ignored.
This parameter SHOULD NOT be used along with the
location-when-unauthenticated parameter. If both were supplied,
clients MAY choose which one is to be honored.
This parameter SHOULD NOT be used as a security measure to prevent
authentication attempts, as it is easily circumvented by users. This
parameter SHOULD be used solely for improving user experience of Web
applications.
4.5. Location-when-logout parameter
Authentication-Control: Digest realm="protected space",
location-when-logout="http://www.example.com/byebye.html"
The parameter "location-when-logout" specifies a location where the
client is to be redirected when the user explicitly requests a
logout. The value of this parameter MUST be a string that contains
an absolute URL location. If a given URL is not absolute, the
clients MAY consider it a relative URL from the current location.
This parameter MAY be used with successfully-authenticated responses.
If this parameter is contained in other kinds of responses, the
clients MUST ignore this parameter.
When the user requests termination of an authentication period, and
if the client currently displays a page supplied by a response with
this parameter, the client will be redirected to the specified
location by a new GET request (as if it received a 303 response).
The log-out operation (e.g. erasing memories of user name,
authentication credential and all related one-time credentials such
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as nonce or keys) SHOULD occur before processing a redirection.
When the user requests termination of an authentication period, if
the client supports this parameter but the server response does not
contain this parameter, the client's RECOMMENDED behavior is as
follows: if the request corresponding to the current content was safe
(e.g. GET), reload the page without the authentication credential.
If the request was non-idempotent (e.g. POST), keep the current
content as-is and simply forget the authentication status. The
client SHOULD NOT replay a non-idempotent request without the user's
explicit approval.
Web applications are encouraged to send this parameter with an
appropriate value for any responses (except those with redirection
(3XX) statuses) for non-GET requests.
4.6. Logout-timeout parameter
Authentication-Control: Basic realm="entrance", logout-timeout=300
The parameter "logout-timeout", when contained in a successfully-
authenticated response, means that any authentication credentials and
state related to the current protection space are to be discarded if
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
a special case, the value 0 means that the client is requested to
immediately log-out from the current authentication space and revert
to an unauthenticated status. This does not, however, mean that the
long-term memories for the passwords and passwords-related details
(such as the password reminders and auto fill-ins) should be removed.
If a new timeout value is received for the same authentication space,
it cancels the previous timeout and sets a new timeout.
4.7. Username parameter
Authentication-Control: Basic realm="configuration", username="admin"
The parameter "username" tells that the only "user name" to be
accepted by the server is the value given in this parameter. This
parameter is particularly useful, for example, for routers and other
appliances with a Web configuration interface.
This parameter MAY be used with authentication-initiating responses
or negatively-authenticated responses requiring another attempt of
authentication. The clients MUST ignore this parameter when a
response is either successfully-authenticated or intermediately-
authenticated.
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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
user names), the specified value MUST follow that limitation.
Clients SHOULD ignore any values which do not conform to such
limitations.
Clients MAY still send any authentication requests with other user
names, possibly in vain. Servers are not strictly required to reject
user names other than specified, but doing so will give bad user
experiences and may confuse users and clients.
If the used authentication scheme requires a specific style of text
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
typical websites which are using Forms and cookies for managing
authentication and authorization. The content of this section is not
normative and for illustrative purposes only.
We assume that all features described in the previous sections are
implemented in clients (Web browsers). We also assume that browsers
will have a user interface which allows users to deactivate (log-out
from) current authentication sessions. If this assumption is not
value, the text below provides another approach with de-
authentication pages used instead of such a UI.
When not explicitly specified, all settings described below are to be
applied with Authentication-Control headers, and these can be sent to
clients regardless of the authentication status (these will be
silently ignored whenever not effective).
5.1. Example 1: a portal site
This subsection provides an example application for a site whose
structure is somewhat similar to conventional portal sites. In
particular, most web pages are available for guest (unauthenticated)
users, and if authentication is performed, the content of these pages
is customized for each user. We assume the site has the following
kinds of pages currently:
o Content pages.
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o Pages/mechanism for performing authentication:
* There is one page which asks a user name and a password using a
HTML POST form.
* After the authentication attempt, the user will be redirected
to either the page which is previously displayed before the
authentication, or some specific page.
o A de-authentication (log-out) page.
5.1.1. Case 1: a simple application
When such a site does not require specific actions upon log-in and
log-out, the following simple settings can be used.
o Set up an optional authentication to all pages available to
guests. Set up an Authentication-Control header with "auth-
style=non-modal" setting.
o If there are pages only available to authenticated users, set up a
mandatory authentication with "auth-style=non-modal" setting.
o No specific pages for authentication are needed. It will be
performed automatically, directed by the above setting.
o A de-authentication page is also not needed. If the site has one,
put "logout-timeout=0" there.
o For all pages for POST requests, it is advisable to have
"location-when-logout=<some page>".
5.1.2. Case 2: specific action required on log-out
If the site requires specific actions upon log-out, the following
settings can be used.
o All settings in the Case 1 are applied.
o For all pages, set up the Authentication-Control header "location-
when-logout=<de-authentication page>".
o In the de-authentication page, no specific set-up is needed. If
there are any direct links to the de-authentication page, put
"logout-timeout=0".
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5.1.3. Case 3: specific page displayed before log-in
If the site needs to display a specific page before log-in actions
(some announcements, user notices, or even advertisements), the
following settings can be applied.
o Set up an optional authentication to all pages available to
guests. Set up an Authentication-Control header with "no-
auth=true". Put a link to a specific log-in page in contents.
o If there are pages only available to authenticated users, set up a
mandatory authentication with "location-when-unauthenticated=<the
log-in page>".
o For the specific log-in page, set up a mandatory authentication.
o For all pages for POST requests, it is advisable to have
"location-when-logout=<some page>", too.
o De-authentication pages are not needed. If the site has one, put
"logout-timeout=0".
5.2. Example 2: authenticated user-only sites
If almost all pages in the target site require authentication (e.g.,
an Internet banking site), or if there are no needs to support both
unauthenticated and authenticated users on the same resource, the
settings will become simpler. The following are an example for such
a site:
o Set up a mandatory authentication to all pages available to
authenticated users. Set up an Authentication-Control header with
"auth-style=non-modal" setting.
o Set up a handler for the 401-status which requests users to
authenticate.
o For all pages for POST requests, it is advisable to have
"location-when-logout=<some page>", too.
o De-authentication pages are not needed. If the site will have
one, put "logout-timeout=0" there.
5.3. When to use Cookies
In the current Web sites using form-based authentications, Cookies
[RFC6265] are used for managing both authorization and application
sessions. Using the extensions in this document, the former features
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will be provided by using (extended) HTTP authentication/
authorization mechanisms. In some cases, there will be ambiguity on
whether some functions are for authorization management or for
session management. The following hints will be helpful for deciding
which features to use.
o If there is a need to serve multiple sessions for a single user
using multiple browsers concurrently, use a Cookie for
distinguishing between sessions for the same user. (C.f. if there
is a need to distinguish sessions in the same browser, HTML5 Web
Storage [W3C.REC-webstorage-20130730] features may be used instead
of Cookies.)
o If a web site is currently deploying a session time-out feature,
consider who benefits from the feature. In most cases, the main
requirement for such a feature is to protect users from having
their consoles and browsers hijacked (i.e. benefits are on the
users' side). In such cases, the time-out features provided in
this extension may be used. On the other hand, the requirement is
to protect server's privilege (e.g. when some regulations require
to limit the time difference between user's two-factor
authentication and financial transaction commitment; the
requirement is strictly on the servers' side), that should be
managed on the server side using Cookies or other session
management mechanisms.
5.4. Parallel deployment with Form/Cookie authentications
In some transition periods, sites may need to support both HTTP-layer
and form-based authentication. The following example shows one way
to achieve that.
o If Cookies are used even for HTTP-authenticated users, each
session determined by Cookies should identify which authentication
has been used for the session.
o First, set up any of the above settings for enabling HTTP-layer
authentication.
o For unauthenticated users, add the following things to the Web
pages, unless the client supports this extension and HTTP-level
authentication.
* For non-mandatory authenticated pages, put a link to Form-based
authenticated pages.
* For mandatory authenticated pages, either put a link to Form-
based authenticated pages, or put a HTML-level redirection
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(using META element) to such pages.
o In Form-based authenticated pages, if users are not authenticated,
the page may have a diversion for HTTP-level authentication by
"location-when-unauthenticated" setting.
o Users are identified to authorization and content customization by
the following logic.
* First, check the result of the HTTP-level authentication. If
there is a Cookie session tied to a specific user, both should
match.
* If the user is not authenticated on the HTTP-level, use the
conventional Form-based method to determine the user.
* If there is a Cookie tied to HTTP authentication, but there is
no corresponding HTTP authentication result, that session will
be discarded (because it means that authentication is
deactivated by the corresponding user).
6. Methods to extend this protocol
If a private extension to this protocol is implemented, it MUST use
the extension-param to avoid conflicts with this protocol and other
future official extensions.
When bare-tokens are used in this protocol, these MUST be allocated
by IANA. Any tokens used for non-private, non-experimental
parameters are RECOMMENDED to be registered to IANA, regardless of
the kind of tokens used.
Extension-tokens MAY be freely used for any non-standard, private,
and/or experimental uses. An extension-tokens MUST use the format
"-<bare-token>.<domain-name>", where <domain-name> is a validly
registered (sub-)domain name on the Internet owned by the party who
defines the extensions. Unknown parameter names are to be ignored
regardless of whether it is extension-tokens or bare-tokens.
7. IANA Considerations
This document defines two new entries for the "Permanent Message
Header Field Names" registry.
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+---------------------------+----------+----------------------------+
| Header Field Name | Protocol | Specification |
+---------------------------+----------+----------------------------+
| Optional-WWW-Authenticate | http | Section 3 of this document |
| Authentication-Control | http | Section 4 of this document |
+---------------------------+----------+----------------------------+
This document also establishes a registry for HTTP authentication
control parameters. The registry manages a case-insensitive ASCII
strings. The string MUST follow the extensive-token syntax defined
in Section 2.2.
To acquire registered tokens, a specification for the use of such
tokens MUST be available as a publicly-accessible documents, as
outlined as "Specification Required" level in [RFC5226].
Registrations for authentication algorithms are required to include a
description of the control extension. New registrations are advised
to provide the following information:
o Token: a token used in HTTP headers for identifying the algorithm.
o Specification: A reference for a specification defining the
algorithm.
The initial content of this registry is as follows:
+-------------------------------+------------------------------+
| Token | Specification |
+-------------------------------+------------------------------+
| auth-style | Section 4.2 of this document |
| location-when-unauthenticated | Section 4.3 of this document |
| no-auth | Section 4.4 of this document |
| location-when-logout | Section 4.5 of this document |
| logout-timeout | Section 4.6 of this document |
| username | Section 4.7 of this document |
+-------------------------------+------------------------------+
8. Security Considerations
The purpose of the log-out timeout feature in the Authentication-
control header is to protect users of clients from impersonation
caused by an attacker having access to the same console. The server
application implementer SHOULD be aware that the directive may always
be ignored by either malicious clients or clients not supporting this
extension. If the purpose of introducing a timeout for an
authentication period is to protect server-side resources, this
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protection MUST be implemented by other means such as HTTP Cookies
[RFC6265].
All parameters in Authentication-Control header SHOULD NOT be used
for any security-enforcement purposes. Server-side applications MUST
always consider that the header may be either ignored by clients or
even bypassed by users.
The "username" parameter may reveal sensitive information about the
HTTP server and its configurations, useful for security attacks. The
use of the "username" parameter SHOULD be limited to cases where the
all of the following conditions are met:
(1) the valid user name is pre-configured and not modifiable (such
as root, admin or similar ones);
(2) the valid user name for such an appliance is publicly known (for
example, written in a manual); and
(3) either the valid user name for the server is easily guessable by
other means (for example, from the model number shown in an
unauthenticated page), or the server is only accessible from
limited networks.
Most importantly, the "username" parameter SHOULD NOT be used in any
case when the valid user names are configured by users or
administrators.
9. References
9.1. Normative References
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, DOI 10.17487/
RFC2119, March 1997,
<http://www.rfc-editor.org/info/rfc2119>.
[RFC5226] Narten, T. and H. Alvestrand, "Guidelines for Writing an
IANA Considerations Section in RFCs", BCP 26, RFC 5226,
DOI 10.17487/RFC5226, May 2008,
<http://www.rfc-editor.org/info/rfc5226>.
[RFC5987] Reschke, J., "Character Set and Language Encoding for
Hypertext Transfer Protocol (HTTP) Header Field
Parameters", RFC 5987, DOI 10.17487/RFC5987, August 2010,
<http://www.rfc-editor.org/info/rfc5987>.
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[RFC7230] Fielding, R., Ed. and J. Reschke, Ed., "Hypertext Transfer
Protocol (HTTP/1.1): Message Syntax and Routing",
RFC 7230, DOI 10.17487/RFC7230, June 2014,
<http://www.rfc-editor.org/info/rfc7230>.
[RFC7235] Fielding, R., Ed. and J. Reschke, Ed., "Hypertext Transfer
Protocol (HTTP/1.1): Authentication", RFC 7235,
DOI 10.17487/RFC7235, June 2014,
<http://www.rfc-editor.org/info/rfc7235>.
9.2. Informative References
[I-D.ietf-httpauth-mutual]
Oiwa, Y., Watanabe, H., Takagi, H., Maeda, K., Hayashi,
T., and Y. Ioku, "Mutual Authentication Protocol for
HTTP", draft-ietf-httpauth-mutual-07 (work in progress),
January 2016.
[RFC6265] Barth, A., "HTTP State Management Mechanism", RFC 6265,
DOI 10.17487/RFC6265, April 2011,
<http://www.rfc-editor.org/info/rfc6265>.
[W3C.REC-webstorage-20130730]
Hickson, I., "Web Storage", World Wide Web Consortium
Recommendation REC-webstorage-20130730, July 2013,
<http://www.w3.org/TR/2013/REC-webstorage-20130730>.
Appendix A. (Informative) Applicability of features for each messages
This section provides a cross-reference table showing the
applicability of the features provided in this specification to each
kind of responses described in Section 2.1. The table provided in
this section is for informative purposes only.
+-------------------+-------+----------+-----------+------+
| | init. | success. | intermed. | neg. |
+-------------------+-------+----------+-----------+------+
| Optional auth. | O | n | N | N |
| auth-style | O | - | - | O |
| loc.-when-unauth. | O | I | I | i |
| no-auth | O | I | I | i |
| loc.-when-logout | - | O | - | - |
| logout-timeout | - | O | - | - |
| username | O | - | - | O |
+-------------------+-------+----------+-----------+------+
Legends:
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O = MAY contain; n = SHOULD NOT contain; N = MUST NOT contain
i = SHOULD be ignored; I = MUST be ignored;
- = meaningless (to be ignored)
Appendix B. (Informative) Draft Change Log
[To be removed on final publication]
B.1. Changes in Httpauth WG Revision 06
o Several comments from reviewers are reflected to the text.
B.2. Changes in Httpauth WG Revision 05
o Authors' addresses updated.
B.3. Changes in Httpauth WG revision 04
o IANA consideration section added.
B.4. Changes in Httpauth WG revision 03
o Adopting RFC 5987 extended syntax for non-ASCII parameter values.
B.5. Changes in Httpauth WG revision 02
o Added realm parameter.
o Added username parameter. We acknowledge Michael Sweet's proposal
for including this to the Basic authentication.
B.6. Changes in Httpauth WG revision 01
o Clarification on peers' responsibility about handling of relative
URLs.
o Automatic reloading should be allowed only on safe methods, not
always on idempotent methods.
B.7. Changes in Httpauth revision 00 and HttpBis revision 00
None.
B.8. Changes in revision 02
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o Added usage examples.
B.9. Changes in revision 01
o Syntax notations and parsing semantics changed to match httpbis
style.
B.10. Changes in revision 00
o Separated from HTTP Mutual authentication proposal (-09).
o Adopting httpbis works as a referencing point to HTTP.
o Generalized, now applicable for all HTTP authentication schemes.
o Added "no-auth" and "auth-style" parameters.
o Loosened standardization requirements for parameter-name tokens
registration.
Authors' Addresses
Yutaka Oiwa
National Institute of Advanced Industrial Science and Technology
Information Technology Research Institute
Tsukuba Central 1
1-1-1 Umezono
Tsukuba-shi, Ibaraki
JP
Email: mutual-auth-contact-ml@aist.go.jp
Hajime Watanabe
National Institute of Advanced Industrial Science and Technology
Information Technology Research Institute
Tsukuba Central 1
1-1-1 Umezono
Tsukuba-shi, Ibaraki
JP
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Hiromitsu Takagi
National Institute of Advanced Industrial Science and Technology
Information Technology Research Institute
Tsukuba Central 1
1-1-1 Umezono
Tsukuba-shi, Ibaraki
JP
Tatsuya Hayashi
Lepidum Co. Ltd.
#602, Village Sasazuka 3
1-30-3 Sasazuka
Shibuya-ku, Tokyo
JP
Yuichi Ioku
Individual
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