draft-ietf-httpauth-mutual-00.txt   draft-ietf-httpauth-mutual-01.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: January 2, 2014 RISEC, AIST Expires: April 24, 2014 RISEC, AIST
B. Kihara
T. Hayashi T. Hayashi
Lepidum Lepidum
Y. Ioku Y. Ioku
Yahoo! Japan Individual
July 1, 2013 October 21, 2013
Mutual Authentication Protocol for HTTP Mutual Authentication Protocol for HTTP
draft-ietf-httpauth-mutual-00 draft-ietf-httpauth-mutual-01
Abstract Abstract
This document specifies a mutual authentication method for the Hyper- This document specifies a mutual authentication method for the Hyper-
text Transport Protocol (HTTP). This method provides a true mutual text Transfer Protocol (HTTP). This method provides a true mutual
authentication between an HTTP client and an HTTP server using authentication between an HTTP client and an HTTP server using
password-based authentication. Unlike the Basic and Digest password-based authentication. Unlike the Basic and Digest
authentication methods, the Mutual authentication method specified in authentication methods, the Mutual authentication method specified in
this document assures the user that the server truly knows the user's this document assures the user that the server truly knows the user's
encrypted password. This prevents common phishing attacks: a encrypted password.
phishing attacker controlling a fake website cannot convince a user
that he authenticated to the genuine website. Furthermore, even when
a user authenticates to an illegitimate server, the server cannot
gain any information about the user's password. The Mutual
authentication method is designed as an extension to the HTTP
protocol, and is intended to replace the existing authentication
methods used in HTTP (the Basic method, Digest method, and
authentication using HTML forms).
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 January 2, 2014.
This Internet-Draft will expire on April 24, 2014.
Copyright Notice Copyright Notice
Copyright (c) 2013 IETF Trust and the persons identified as the Copyright (c) 2013 IETF Trust and the persons identified as the
document authors. All rights reserved. document authors. All rights reserved.
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Table of Contents Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 5 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 4
1.1. Relations to other technologies . . . . . . . . . . . . . 6 1.1. Terminology . . . . . . . . . . . . . . . . . . . . . . . 4
1.1.1. Technologies updated or superceded by this proposal . 6 1.2. Document Structure and Related Documents . . . . . . . . . 5
1.1.1.1. HTTP Basic and Digest authentication . . . . . . . 6 2. Protocol Overview . . . . . . . . . . . . . . . . . . . . . . 5
1.1.1.2. HTML Form authentication . . . . . . . . . . . . . 6 2.1. Messages Overview . . . . . . . . . . . . . . . . . . . . 6
1.1.2. Technologies not updated by this proposal . . . . . . 7 2.2. Typical Flows of the Protocol . . . . . . . . . . . . . . 6
1.1.2.1. Federated identity/authorization management . . . 7 2.3. Alternative Flows . . . . . . . . . . . . . . . . . . . . 9
1.1.2.2. HTTPS and HTTPS client-certificate 3. Message Syntax . . . . . . . . . . . . . . . . . . . . . . . . 10
authentication . . . . . . . . . . . . . . . . . . 8 3.1. Values . . . . . . . . . . . . . . . . . . . . . . . . . . 11
1.1.2.3. Protocols for local identity-management 3.1.1. Tokens . . . . . . . . . . . . . . . . . . . . . . . . 11
frameworks . . . . . . . . . . . . . . . . . . . . 8 3.1.2. Strings . . . . . . . . . . . . . . . . . . . . . . . 12
1.1.2.4. HTTP and HTTP authentication architecture . . . . 8 3.1.3. Numbers . . . . . . . . . . . . . . . . . . . . . . . 12
1.2. Terminology . . . . . . . . . . . . . . . . . . . . . . . 9 4. Messages . . . . . . . . . . . . . . . . . . . . . . . . . . . 13
1.3. Document Structure and Related Documents . . . . . . . . . 9 4.1. 401-INIT and 401-STALE . . . . . . . . . . . . . . . . . . 14
2. Protocol Overview . . . . . . . . . . . . . . . . . . . . . . 10 4.2. req-KEX-C1 . . . . . . . . . . . . . . . . . . . . . . . . 17
2.1. Messages Overview . . . . . . . . . . . . . . . . . . . . 10 4.3. 401-KEX-S1 . . . . . . . . . . . . . . . . . . . . . . . . 17
2.2. Typical Flows of the Protocol . . . . . . . . . . . . . . 11 4.4. req-VFY-C . . . . . . . . . . . . . . . . . . . . . . . . 18
2.3. Alternative Flows . . . . . . . . . . . . . . . . . . . . 14 4.5. 200-VFY-S . . . . . . . . . . . . . . . . . . . . . . . . 19
3. Message Syntax . . . . . . . . . . . . . . . . . . . . . . . . 15 5. Authentication Realms . . . . . . . . . . . . . . . . . . . . 19
3.1. Values . . . . . . . . . . . . . . . . . . . . . . . . . . 16 5.1. Resolving Ambiguities . . . . . . . . . . . . . . . . . . 21
3.1.1. Tokens . . . . . . . . . . . . . . . . . . . . . . . . 16 6. Session Management . . . . . . . . . . . . . . . . . . . . . . 22
3.1.2. Strings . . . . . . . . . . . . . . . . . . . . . . . 17 7. Host Validation Methods . . . . . . . . . . . . . . . . . . . 23
3.1.3. Numbers . . . . . . . . . . . . . . . . . . . . . . . 17 7.1. Applicability notes . . . . . . . . . . . . . . . . . . . 25
4. Messages . . . . . . . . . . . . . . . . . . . . . . . . . . . 18 7.2. Interoperability notes on tls-unique . . . . . . . . . . . 25
4.1. 401-INIT and 401-STALE . . . . . . . . . . . . . . . . . . 19 8. Authentication Extensions . . . . . . . . . . . . . . . . . . 26
4.2. req-KEX-C1 . . . . . . . . . . . . . . . . . . . . . . . . 22 9. Decision Procedure for Clients . . . . . . . . . . . . . . . . 26
4.3. 401-KEX-S1 . . . . . . . . . . . . . . . . . . . . . . . . 22 10. Decision Procedure for Servers . . . . . . . . . . . . . . . . 31
4.4. req-VFY-C . . . . . . . . . . . . . . . . . . . . . . . . 23 11. Authentication Algorithms . . . . . . . . . . . . . . . . . . 33
4.5. 200-VFY-S . . . . . . . . . . . . . . . . . . . . . . . . 24 11.1. Support Functions and Notations . . . . . . . . . . . . . 34
5. Authentication Realms . . . . . . . . . . . . . . . . . . . . 24 11.2. Default Functions for Algorithms . . . . . . . . . . . . . 35
5.1. Resolving Ambiguities . . . . . . . . . . . . . . . . . . 26 12. Application Channel Binding . . . . . . . . . . . . . . . . . 36
6. Session Management . . . . . . . . . . . . . . . . . . . . . . 27 13. Application for Proxy Authentication . . . . . . . . . . . . . 36
7. Host Validation Methods . . . . . . . . . . . . . . . . . . . 28 14. Methods to Extend This Protocol . . . . . . . . . . . . . . . 37
8. Authentication Extensions . . . . . . . . . . . . . . . . . . 30 15. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 38
9. Decision Procedure for Clients . . . . . . . . . . . . . . . . 30 16. Security Considerations . . . . . . . . . . . . . . . . . . . 38
10. Decision Procedure for Servers . . . . . . . . . . . . . . . . 35 16.1. Security Properties . . . . . . . . . . . . . . . . . . . 38
11. Authentication Algorithms . . . . . . . . . . . . . . . . . . 37 16.2. Denial-of-service Attacks to Servers . . . . . . . . . . . 39
11.1. Support Functions and Notations . . . . . . . . . . . . . 38 16.2.1. On-line Active Password Attacks . . . . . . . . . . . 39
11.2. Default Functions for Algorithms . . . . . . . . . . . . . 39 16.3. Communicating the status of mutual authentication with
12. Application Channel Binding . . . . . . . . . . . . . . . . . 40 users . . . . . . . . . . . . . . . . . . . . . . . . . . 39
13. Application for Proxy Authentication . . . . . . . . . . . . . 40 16.4. Implementation Considerations . . . . . . . . . . . . . . 40
14. Methods to Extend This Protocol . . . . . . . . . . . . . . . 41 16.5. Usage Considerations . . . . . . . . . . . . . . . . . . . 41
15. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 42 17. Notice on Intellectual Properties . . . . . . . . . . . . . . 41
16. Security Considerations . . . . . . . . . . . . . . . . . . . 42 18. References . . . . . . . . . . . . . . . . . . . . . . . . . . 42
16.1. Security Properties . . . . . . . . . . . . . . . . . . . 42 18.1. Normative References . . . . . . . . . . . . . . . . . . . 42
16.2. Denial-of-service Attacks to Servers . . . . . . . . . . . 43 18.2. Informative References . . . . . . . . . . . . . . . . . . 42
16.3. Implementation Considerations . . . . . . . . . . . . . . 43 Appendix A. (Informative) Draft Remarks from Authors . . . . . . 44
16.4. Usage Considerations . . . . . . . . . . . . . . . . . . . 44 Appendix B. (Informative) Draft Change Log . . . . . . . . . . . 44
17. Notice on Intellectual Properties . . . . . . . . . . . . . . 44 B.1. Changes in Httpauth WG Revision 01 . . . . . . . . . . . . 44
18. References . . . . . . . . . . . . . . . . . . . . . . . . . . 45 B.2. Changes in Httpauth Revision 00 . . . . . . . . . . . . . 44
18.1. Normative References . . . . . . . . . . . . . . . . . . . 45 B.3. Changes in HttpBis Revision 00 . . . . . . . . . . . . . . 45
18.2. Informative References . . . . . . . . . . . . . . . . . . 46 B.4. Changes in Revision 12 . . . . . . . . . . . . . . . . . . 45
Appendix A. (Informative) Draft Remarks from Authors . . . . . . 47 B.5. Changes in Revision 11 . . . . . . . . . . . . . . . . . . 45
Appendix B. (Informative) Draft Change Log . . . . . . . . . . . 48 B.6. Changes in Revision 10 . . . . . . . . . . . . . . . . . . 45
B.1. Changes in Httpauth Revision 00 . . . . . . . . . . . . . 48 B.7. Changes in Revision 09 . . . . . . . . . . . . . . . . . . 46
B.2. Changes in HttpBis Revision 00 . . . . . . . . . . . . . . 48 B.8. Changes in Revision 08 . . . . . . . . . . . . . . . . . . 46
B.3. Changes in Revision 12 . . . . . . . . . . . . . . . . . . 48 B.9. Changes in Revision 07 . . . . . . . . . . . . . . . . . . 46
B.4. Changes in Revision 11 . . . . . . . . . . . . . . . . . . 48 B.10. Changes in Revision 06 . . . . . . . . . . . . . . . . . . 47
B.5. Changes in Revision 10 . . . . . . . . . . . . . . . . . . 48 B.11. Changes in Revision 05 . . . . . . . . . . . . . . . . . . 47
B.6. Changes in Revision 09 . . . . . . . . . . . . . . . . . . 49 B.12. Changes in Revision 04 . . . . . . . . . . . . . . . . . . 47
B.7. Changes in Revision 08 . . . . . . . . . . . . . . . . . . 50 B.13. Changes in Revision 03 . . . . . . . . . . . . . . . . . . 48
B.8. Changes in Revision 07 . . . . . . . . . . . . . . . . . . 50 B.14. Changes in Revision 02 . . . . . . . . . . . . . . . . . . 48
B.9. Changes in Revision 06 . . . . . . . . . . . . . . . . . . 50 B.15. Changes in Revision 01 . . . . . . . . . . . . . . . . . . 48
B.10. Changes in Revision 05 . . . . . . . . . . . . . . . . . . 50 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 48
B.11. Changes in Revision 04 . . . . . . . . . . . . . . . . . . 51
B.12. Changes in Revision 03 . . . . . . . . . . . . . . . . . . 51
B.13. Changes in Revision 02 . . . . . . . . . . . . . . . . . . 51
B.14. Changes in Revision 01 . . . . . . . . . . . . . . . . . . 51
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 52
1. Introduction 1. Introduction
This document specifies a mutual authentication method for Hyper-Text This document specifies a mutual authentication method for Hyper-Text
Transport Protocol (HTTP). The method, called "Mutual Authentication Transfer Protocol (HTTP). The method, called "Mutual Authentication
Protocol" in this document, provides a true mutual authentication Protocol" in this document, provides a true mutual authentication
between an HTTP client and an HTTP server, using just a simple between an HTTP client and an HTTP server, using just a simple
password as a credential. password as a credential.
The currently available methods for authentication in HTTP and Web The authentication method proposed in this document has the following
systems have several deficiencies. The Basic authentication method main characteristics:
[RFC2617] sends a plaintext password to a server without any
protection; the Digest method uses a hash function that suffers from
simple dictionary-based off-line attacks, and people have begun to
think it is obsolete.
The authentication method proposed in this document solves these
problems, substitutes for these existing methods, and serves as a
long-term solution to Web authentication security. It has the
following main characteristics:
o It provides "true" mutual authentication: in addition to assuring o It provides "true" mutual authentication: in addition to assuring
the server that the user knows the password, it also assures the the server that the user knows the password, it also assures the
user that the server truly knows the user's encrypted password at user that the server truly knows the user's encrypted password at
the same time. This makes it impossible for fake website owners the same time. This makes it impossible for fake website owners
to persuade users that they have authenticated with the original to persuade users that they have authenticated with the original
websites. websites.
o It uses only passwords as the user's credential: unlike public- o It uses only passwords as the user's credential: unlike public-
key-based security algorithms, the method does not rely on secret key-based security algorithms, the method does not rely on secret
keys or other cryptographic data that have to be stored inside the keys or other cryptographic data that have to be stored inside the
users' computers. The proposed method can be used as a drop-in users' computers. The proposed method can be used as a drop-in
replacement to the current authentication methods like Basic or replacement to the current authentication methods like Basic or
Digest, while ensuring a much stronger level of security. Digest, while ensuring a much stronger level of security.
o It is secure: when the server fails to authenticate with a user, o It is secure: when the server fails to authenticate with a user,
the protocol will not reveal any bit of the user's password. the protocol will not reveal any tiny bit of information about the
user's password.
Users can discriminate between true and fake Web servers using their
own passwords by using the proposed method. Even when a user inputs
his/her password to a fake website owned by illegitimate phishers,
the user will certainly notice that the authentication has failed.
Phishers will not be successful in their authentication attempts,
even if they forward the received data from a user to a legitimate
server or vice versa. Users can input sensitive data to the web
forms after confirming that the mutual authentication has succeeded,
without fear of phishing attacks.
The document, along with [I-D.ietf-httpauth-extension], also proposes
several extensions to the current HTTP authentication framework, to
replace current widely-used form-based Web authentication. The
extensions provided include:
o Multi-host single authentication within an Internet domain
(Section 5),
o non-mandatory, optional authentication on HTTP (Section 8),
o log out from both server and client side (Section 8), and
o finer control for redirection depending on authentication status
(Section 8).
1.1. Relations to other technologies
1.1.1. Technologies updated or superceded by this proposal
1.1.1.1. HTTP Basic and Digest authentication
The main purpose of this proposal is obviously providing an upgrade
for the two existing HTTP authentication methods, Basic and Digest
[RFC2617].
HTTP Basic authentication, as its name suggests, provides very simple
authentication mechanism using plain-text password directly upon the
HTTP transport. HTTP Digest authentication focuses on mitigating the
fundamental weakness of Basic authentication by using MD5-based
hashing to the authentication, but that has almost failed to deploy
due to improper implementations, interoperability problems, and
missing feature implementations before MD5 has deprecated by its
cryptographic weakness. Digest also has a fundamental problem that
the server-side must posses a password-equivalent to perform
authentication, which increases risks of server-side data leakage.
1.1.1.2. HTML Form authentication
Another aim of this protocol is (at least) partially replacing the
HTML form authentication. Because of inflexibility of the HTTP Basic
authentication, recent Web applications tend to use application-level
implementations for user authentication using HTML Forms and Web
browser rendering engines. However, that method has many potential
security weaknesses as same as the HTTP Basic authentication as it
uses plaintext. Considering server-impersonations and existence of
human-forging rogue servers (i.e. phishing), script-based
implementations of hash-based authentication does not help, because
its behavior is completely controlled by the web-page content itself,
which is possibly provided by such a rogue server. This also closes
any possibilities for extending HTML forms to implement cryptography,
as its user-interface could not be prevented from being imitated
using plain-text forms. Using HTTP-level authentication is better in
this field, because it is under the control of the client software
(Web browsers), which can enforce security checks regardless of
server-provided contents.
Of course, we could not ignore the strong reasons of favoring Form
authentication over Basic authentication: its flexibility. HTTP
authentication framework lacks many features for recent Web
applications, mainly for interactions between HTTP-level
authentications and application-level management of "authentication
sessions". As long as current HTTP-layer (and lower-layer)
authentication are used, the new method would share the same problem.
To solve this problem, this protocol has a companion mechanism for
application-level control of authentication behaviors as a separate
draft [I-D.ietf-httpauth-extension]. By using this additional
mechanism, Web applications can implement most of these required
features as easy as just calling an already-provided API for them.
1.1.2. Technologies not updated by this proposal
1.1.2.1. Federated identity/authorization management
There are several technologies (protocols, frameworks, or systems)
for managing authentications/authorizations involving multiple-
parties: some of those examples are OAuth [RFC6749], OpenID Connect
[OIDF.Connect.Standard], SAML [OASIS.saml-core-2.0-os] etc. These
technologies can be further divided to two categories: federated
authentication and authorization delegation, although some of these
technologies cover both.
Federated authentication provides so-called "three-legged
authentication": provided the result of user authentication to a
single entity (identity provider) and the user's consent, the
mechanism can provide other entities assertion of the user's identity
without performing a separate identity management by every entity.
Authorization delegation gives a mechanism for transferring a part of
the user's privilege on an entity (resource owners) to another entity
without requiring users give away the full credential for the
authentication.
Essentially, both of those technologies are transforming a result of
conventional, one-by-one (two-legged) authentication into a multi-
party privilege management. The purpose of this protocol is to
secure the very part of the two-legged authentication, and so it can
be naturally combined with existing federated management frameworks
for increasing security of the entire system.
Additionally, this protocol can provide a secure peer-to-peer shared
key generated during authentication to the higher-layer applications
Section 12. These keys can be possibly used by such federating
mechanisms in future for simplifying/securing the framework.
1.1.2.2. HTTPS and HTTPS client-certificate authentication
This protocol will not replace the wide-spread and widely-accepted
technology of SSL/TLS and HTTPS [RFC2818]. This protocol will be
still relying on the HTTPS for the integrity and secrecy of the HTTP
payload. This protocol ensures users the integrity and secrecy of
the authentication credentials, and authenticity of the talking peer
server.
Client certificate (and other public-key-based) authentications have
a fair-amount of applications (mainly for high-assurance
applications), and there are possible needs for redesigning/updating
the whole framework. However, currently public-key-based user-
authentication and connection-based user identification is out-of-
scope of this proposal.
1.1.2.3. Protocols for local identity-management frameworks
There are several existing frameworks for managing user identity of
tightly-managed, closed group of users, such as Kerberos [RFC3961] /
GSS-API [RFC2743] etc. Some of these have defined a bridging
protocol for HTTP authentication. This protocol does not currently
aim to replace such existing frameworks.
More precisely, requirements for those framework and usual Web user
authentication differ fundamentally. In such framework, user
authentication in performed first, and the result of the
authentication tends to be shared in all applications, sometimes even
shared regardless of the underlying protocols. In those systems, it
is almost never likely to use a multiple identity to be used inside a
single server and inside a single client machine at the same time.
In such applications, connection-based or even a machine-based
authentication can be used without a trouble. This is not a case for
the general Web authentication applications.
1.1.2.4. HTTP and HTTP authentication architecture
Although HTTP and generic HTTP authentication architecture lacks some
required features (see above), the whole structure of per-request,
per-resource authentication is well-suited for general Web
applications compared with connection-based or machine-based
authentication/authorization framework (those which tie user identity
to either connections or machines). The whole protocol in this
specification is designed on top of the framework of
[I-D.ietf-httpbis-p7-auth]. Small extensions to the framework in
this specification and [I-D.ietf-httpauth-extension], which are
designed for filling the missing features, are carefully designed so
that it can be implemented easily only by the client-side without
changing the whole framework.
1.2. 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
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
security, 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".
The term "natural numbers" refers to the non-negative integers The term "natural numbers" refers to the non-negative integers
(including zero) throughout this document. (including zero) throughout this document.
This document treats target (codomain) of hash functions to be This document treats target (codomain) of hash functions to be octet
natural numbers. The notation OCTETS(H(s)) gives a usual octet- strings. The notation INT(H(s)) gives a numerical (natural-number)
string output of hash function H applied to string s. output of hash function H applied to string s.
1.3. Document Structure and Related Documents 1.2. Document Structure and Related Documents
The entire document is organized as follows: The entire document is organized as follows:
o Section 2 presents an overview of the protocol design. o Section 2 presents an overview of the protocol design.
o Sections 3 to 10 define a general framework of the Mutual o Sections 3 to 10 define a general framework of the Mutual
authentication protocol. This framework is independent of authentication protocol. This framework is independent of
specific cryptographic primitives. specific cryptographic primitives.
o Section 11 describes properties needed for cryptographic o Section 11 describes properties needed for cryptographic
skipping to change at page 10, line 49 skipping to change at page 6, line 18
mutual authentication. These messages have specific names within mutual authentication. These messages have specific names within
this specification. this specification.
o Authentication request messages: used by the servers to request o Authentication request messages: used by the servers to request
clients to start mutual authentication. clients to start mutual authentication.
* 401-INIT message: a general message to start the authentication * 401-INIT message: a general message to start the authentication
protocol. It is also used as a message indicating an protocol. It is also used as a message indicating an
authentication failure. authentication failure.
* 200-Optional-INIT message: a variant of the 401-INIT message
indicating that an authentication is not mandatory.
* 401-STALE message: a message indicating that it has to start a * 401-STALE message: a message indicating that it has to start a
new authentication trial. new authentication trial.
o Authenticated key exchange messages: used by both peers to perform o Authenticated key exchange messages: used by both peers to perform
authentication and the sharing of a cryptographic secret. authentication and the sharing of a cryptographic secret.
* req-KEX-C1 message: a message sent from the client. * req-KEX-C1 message: a message sent from the client.
* 401-KEX-S1 message: a message sent from the server as a * 401-KEX-S1 message: a message sent from the server as a
response to a req-KEX-C1 message. response to a req-KEX-C1 message.
skipping to change at page 13, line 29 skipping to change at page 8, line 29
o The client will send a request with a client-side authentication o The client will send a request with a client-side authentication
verification value (req-VFY-C) (6), generated from the client- verification value (req-VFY-C) (6), generated from the client-
owned session secret. The server will check the validity of the owned session secret. The server will check the validity of the
verification value using its own session secret. verification value using its own session secret.
o If the authentication verification value from the client was o If the authentication verification value from the client was
correct, it means that the client definitely owns the credential correct, it means that the client definitely owns the credential
based on the expected password (i.e. the client authentication based on the expected password (i.e. the client authentication
succeeded.) The server will respond with a successful message succeeded.) The server will respond with a successful message
(200-VFY-S) (7). Contrary to the usual one-way authentication (200-VFY-S) (7). Contrary to the usual one-way authentication
(e.g. HTTP Basic authentication or POP APOP authentication), this (e.g. HTTP Basic authentication or POP APOP authentication
message also contains a server-side authentication verification [RFC1939]), this message also contains a server-side
value. authentication verification value.
When the client's verification value is incorrect (e.g. because When the client's verification value is incorrect (e.g. because
the user-supplied password was incorrect), the server will respond the user-supplied password was incorrect), the server will respond
with the 401-INIT message (the same one as used in (2)) instead. with the 401-INIT message (the same one as used in (2)) instead.
o The client MUST first check the validity of the server-side o The client MUST first check the validity of the server-side
authentication verification value contained in the message (7). authentication verification value contained in the message (7).
If the value was equal to the expected one, the server If the value was equal to the expected one, the server
authentication succeeded. authentication succeeded.
If it is not the value expected, or if the message does not If it is not the value expected, or if the message does not
contain the authentication verification value, it means that the contain the authentication verification value, it means that the
mutual authentication has been broken for some unexpected reason. mutual authentication has been broken for some unexpected reason.
The client MUST NOT process any body or header values contained in The client MUST NOT process any body or header values contained in
this case. (Note: This case should not happen between a this case. (Note: This case should not happen between a
correctly-implemented server and a client.) correctly-implemented server and a client without any
interventions. Possible cause of such cases might be either a
man-in-the-middle attack or a mis-implementation.)
2.3. Alternative Flows 2.3. Alternative Flows
As shown above, the typical flow for a first authenticated request As shown above, the typical flow for a first authenticated request
requires three request-response pairs. To reduce the protocol requires three request-response pairs. To reduce the protocol
overhead, the protocol enables several short-cut flows which require overhead, the protocol enables several short-cut flows which require
fewer messages. fewer messages.
o (case A) If the client knows that the resource is likely to o (case A) If the client knows that the resource is likely to
require the authentication, the client MAY omit the first require the authentication, the client MAY omit the first
skipping to change at page 16, line 37 skipping to change at page 11, line 37
3.1. Values 3.1. Values
The parameter values contained in challenge/credentials MUST be The parameter values contained in challenge/credentials MUST be
parsed strictly conforming to the HTTP semantics (especially un- parsed strictly conforming to the HTTP semantics (especially un-
quoting of the string parameter values). In this protocol, those quoting of the string parameter values). In this protocol, those
values are further categorized into the following value types: tokens values are further categorized into the following value types: tokens
(bare-token and extensive-token), string, integer, hex-fixed-number, (bare-token and extensive-token), string, integer, hex-fixed-number,
and base64-fixed-number. and base64-fixed-number.
For clarity, implementations are encouraged to use the canonical For clarity, implementations are RECOMMENDED to use the canonical
representations specified in the following subsections for sending representations specified in the following subsections for sending
values. Recipients SHOULD accept both quoted and unquoted values. Recipients SHOULD accept both quoted and unquoted
representations interchangeably as specified in HTTP. representations interchangeably as specified in HTTP.
3.1.1. Tokens 3.1.1. Tokens
For sustaining both security and extensibility at the same time, this For sustaining both security and extensibility at the same time, this
protocol defines a stricter sub-syntax for the "token" to be used. protocol defines a stricter sub-syntax for the "token" to be used.
The extensive-token values SHOULD follow the following syntax (after The extensive-token values SHOULD follow the following syntax (after
HTTP value parsing): HTTP value parsing):
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party who defines the extensions. party who defines the extensions.
Bare-tokens and extensive-tokens are also used for parameter names Bare-tokens and extensive-tokens are also used for parameter names
(of course in the unquoted form). Requirements for using the (of course in the unquoted form). Requirements for using the
extension-token for the parameter names are the same as the above. extension-token for the parameter names are the same as the above.
The canonical format for bare-tokens and tokens are unquoted tokens. The canonical format for bare-tokens and tokens are unquoted tokens.
3.1.2. Strings 3.1.2. Strings
All character strings outside ASCII character sets MUST be encoded All character strings MUST be encoded to octet strings using the
using the UTF-8 encoding [RFC3629] for the ISO 10646-1 character set UTF-8 encoding [RFC3629] for the ISO 10646-1 character set
[ISO.10646-1.1993], without any leading BOM characters. Both peers [ISO.10646-1.1993]. Such strings MUST NOT contain any leading BOM
are RECOMMENDED to reject any invalid UTF-8 sequences that might characters (ZERO WIDTH NO-BREAK SPACE, U+FEFF or EF BB BF). Both
cause decoding ambiguities (e.g., containing <"> in the second or peers are RECOMMENDED to reject any invalid UTF-8 sequences that
later byte of the UTF-8 encoded characters). might cause decoding ambiguities (e.g., containing <"> in the second
or later bytes of the UTF-8 encoded characters).
If strings are representing a domain name or URI that contains non- If strings are representing a domain name or URI that contains non-
ASCII characters, the host parts SHOULD be encoded as it is used in ASCII characters, the host parts SHOULD be encoded as it is used in
the HTTP protocol layer (e.g. in a Host: header); under current the HTTP protocol layer (e.g. in a Host: header); under current
standards it will be the one defined in [RFC5890]. It SHOULD use standards it will be the one defined in [RFC5890]. It SHOULD use
lower-case ASCII characters. lower-case ASCII characters.
The canonical format for strings are quoted-string (as it may contain The canonical format for strings are quoted-string (as it may contain
equal sign, plus sign and slashs). equal signs, plus signs and slashes).
3.1.3. Numbers 3.1.3. Numbers
The following syntax definitions gives a syntax for number-type The following syntax definitions gives a syntax for number-type
values: values:
integer = "0" / (%x31-39 *DIGIT) ; no leading zeros integer = "0" / (%x31-39 *DIGIT) ; no leading zeros
hex-fixed-number = 1*(2(DIGIT / %x41-46 / %x61-66)) hex-fixed-number = 1*(2(DIGIT / %x41-46 / %x61-66))
base64-fixed-number = 1*( ALPHA / DIGIT / base64-fixed-number = 1*( ALPHA / DIGIT / "+" / "/" ) 0*2"="
"-" / "." / "_" / "~" / "+" / "/" ) *"="
Figure 4: BNF syntax for number types Figure 4: BNF syntax for number types
The syntax definition of the integers only allows representations The syntax definition of the integers only allows representations
that do not contain extra leading zeros. that do not contain extra leading zeros.
The numbers represented as a hex-fixed-number MUST include an even The numbers represented as a hex-fixed-number MUST include an even
number of characters (i.e. multiples of eight bits). Those values number of characters (i.e. multiples of eight bits). Those values
are case-insensitive, and SHOULD be sent in lower-case. When these are case-insensitive, and SHOULD be sent in lower-case. When these
values are generated from any cryptographic values, they SHOULD have values are generated from any cryptographic values, they SHOULD have
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explicitly specified in the following sections. Recipients who do explicitly specified in the following sections. Recipients who do
not understand such parameters MUST silently ignore those. However, not understand such parameters MUST silently ignore those. However,
all credentials and challenges MUST meet the following criteria: all credentials and challenges MUST meet the following criteria:
o For responses, the parameters "reason", any "ks*" (where * stands o For responses, the parameters "reason", any "ks*" (where * stands
for any decimal integers), and "vks" are mutually exclusive: any for any decimal integers), and "vks" are mutually exclusive: any
challenge MUST NOT contain two or more parameters among them. challenge MUST NOT contain two or more parameters among them.
They MUST NOT contain any "kc*" and "vkc" parameters. They MUST NOT contain any "kc*" and "vkc" parameters.
o For requests, the parameters "kc*" (where * stands for any decimal o For requests, the parameters "kc*" (where * stands for any decimal
integers), and "vks" are mutually exclusive and any challenge integers), and "vkc" are mutually exclusive and any challenge
MUST NOT contain two or more parameters among them. They MUST NOT MUST NOT contain two or more parameters among them. They MUST NOT
contain any "ks*" and "vks" parameters. contain any "ks*" and "vks" parameters.
Every message in this section contains a "version" field, to detect
future incompatible revisions of the protocol. Implementations of
the protocol described in this specification MUST always send a token
"-wg-draft01", and recipients MUST reject messages which contain any
other value as a version, unless another specification defines a
behavior for that version. [[Editorial Note: This token is updated
on every draft revisions which will affect the wire protocol. It
will (shall) be updated to "1" in the final published RFC.]]
4.1. 401-INIT and 401-STALE 4.1. 401-INIT and 401-STALE
Every 401-INIT or 401-STALE message SHALL be a valid HTTP 401-status Every 401-INIT or 401-STALE message SHALL be a valid HTTP 401-status
(Authentication Required) message containing one (and only one: (Authentication Required) message containing one (and only one:
hereafter not explicitly noticed) "WWW-Authenticate" header hereafter not explicitly noticed) "WWW-Authenticate" header
containing a "reason" parameter in the challenge. The challenge containing a "reason" parameter in the challenge. The challenge
SHALL contain all of the parameters marked "mandatory" below, and MAY SHALL contain all of the parameters marked "mandatory" below, and MAY
contain those marked "non-mandatory". contain those marked "non-mandatory".
version: (mandatory extensive-token) should be the token "-wg- version: (mandatory extensive-token) should be the token "-wg-
draft00" in this specification. The behavior is draft01".
undefined when other values are specified.
algorithm: (mandatory extensive-token) specifies the algorithm: (mandatory extensive-token) specifies the
authentication algorithm to be used. The value MUST authentication algorithm to be used. The value MUST
be one of the tokens specified in be one of the tokens specified in
[I-D.oiwa-httpauth-mutual-algo] or other supplemental [I-D.oiwa-httpauth-mutual-algo] or other supplemental
specification documentation. specification documentation.
validation: (mandatory extensive-token) specifies the method of validation: (mandatory extensive-token) specifies the method of
host validation. The value MUST be one of the tokens host validation. The value MUST be one of the tokens
described in Section 7, or the tokens specified in described in Section 7, or the tokens specified in
other supplemental specification documentation. other supplemental specification documentation.
auth-domain: (non-mandatory string) specifies the authentication auth-domain: (non-mandatory string) specifies the authentication
domain, the set of hosts for which the authentication domain, the set of hosts for which the authentication
credentials are valid. It MUST be one of the strings credentials are valid. It MUST be one of the strings
described in Section 5. If the value is omitted, it described in Section 5. If the value is omitted, it
is assumed to be the "single-port" type domain in is assumed to be the "single-server" type domain in
Section 5. Section 5.
realm: (mandatory string) is a UTF-8 encoded string realm: (mandatory string) is a UTF-8 encoded string
representing the name of the authentication realm representing the name of the authentication realm
inside the authentication domain. As specified in inside the authentication domain. As specified in
[I-D.ietf-httpbis-p7-auth], this value MUST always be [I-D.ietf-httpbis-p7-auth], this value MUST always be
sent in the quoted-string form. sent in the quoted-string form.
pwd-hash: (non-mandatory extensive-token) specifies the hash pwd-hash: (non-mandatory extensive-token) specifies the hash
algorithm (hereafter referred to by ph) used for algorithm (hereafter referred to by ph) used for
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* md5: ph(p) = MD5(p) * md5: ph(p) = MD5(p)
* digest-md5: ph(p) = MD5(username | ":" | realm | * digest-md5: ph(p) = MD5(username | ":" | realm |
":" | p), the same value as MD5(A1) for "MD5" ":" | p), the same value as MD5(A1) for "MD5"
algorithm in [RFC2617]. algorithm in [RFC2617].
* sha1: ph(p) = SHA1(p) * sha1: ph(p) = SHA1(p)
If omitted, the value "none" is assumed. The use of If omitted, the value "none" is assumed. The use of
"none" is recommended. "none" is desirable.
reason: (mandatory extensive-token) SHALL be an extensive- reason: (mandatory extensive-token) SHALL be an extensive-
token which describes the possible reason of the token which describes the possible reason of the
failed authentication/authorization. Both servers and failed authentication/authorization. Both servers and
clients SHALL understand and support the following clients SHALL understand and support the following
three tokens: three tokens:
* initial: authentication was not tried because there * initial: authentication was not tried because there
was no Authorization header in the corresponding was no Authorization header in the corresponding
request. request.
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4.2. req-KEX-C1 4.2. req-KEX-C1
Every req-KEX-C1 message SHALL be a valid HTTP request message Every req-KEX-C1 message SHALL be a valid HTTP request message
containing an "Authorization" header with a credential containing a containing an "Authorization" header with a credential containing a
"kc1" parameter. "kc1" parameter.
The credential SHALL contain the parameters with the following names: The credential SHALL contain the parameters with the following names:
version: (mandatory, extensive-token) should be the token "-wg- version: (mandatory, extensive-token) should be the token "-wg-
draft00" in this specification. The behavior is draft01".
undefined when other values are specified.
algorithm, validation, auth-domain, realm: MUST be the same value as algorithm, validation, auth-domain, realm: MUST be the same value as
it is when received from the server. it is when received from the server.
user: (mandatory, string) is the UTF-8 encoded name of the user: (mandatory, string) is the UTF-8 encoded name of the
user. If this name comes from a user input, client user. If this name comes from a user input, client
software SHOULD prepare the string using SASLprep software SHOULD prepare the string using HTTPAUTHprep
[RFC4013] before encoding it to UTF-8. [I-D.oiwa-precis-httpauthprep] before encoding it to
UTF-8. [[Editorial: merger with new SASLprep is being
considered and discussed in precis WG. Replace the
reference once it is done.]]
kc1: (mandatory, algorithm-determined) is the client-side kc1: (mandatory, algorithm-determined) is the client-side
key exchange value K_c1, which is specified by the key exchange value K_c1, which is specified by the
algorithm that is used. algorithm that is used.
rekey-sid: (non-mandatory, hex-fixed-number): reserved for future
extensions (see rekey-method in "200-VFY-S" message).
4.3. 401-KEX-S1 4.3. 401-KEX-S1
Every 401-KEX-S1 message SHALL be a valid HTTP 401-status Every 401-KEX-S1 message SHALL be a valid HTTP 401-status
(Authentication Required) response message containing a (Authentication Required) response message containing a
"WWW-Authenticate" header with a challenge containing a "ks1" "WWW-Authenticate" header with a challenge containing a "ks1"
parameter. parameter.
The challenge SHALL contain the parameters with the following names: The challenge SHALL contain the parameters with the following names:
version: (mandatory, extensive-token) should be the token "-wg- version: (mandatory, extensive-token) should be the token "-wg-
draft00" in this specification. The behavior is draft01".
undefined when other values are specified.
algorithm, validation, auth-domain, realm: MUST be the same value as algorithm, validation, auth-domain, realm: MUST be the same value as
it is when received from the client. it is when received from the client.
sid: (mandatory, hex-fixed-number) MUST be a session sid: (mandatory, hex-fixed-number) MUST be a session
identifier, which is a random integer. The sid SHOULD identifier, which is a random integer. The sid SHOULD
have uniqueness of at least 80 bits or the square of have uniqueness of at least 80 bits or the square of
the maximal estimated transactions concurrently the maximal estimated transactions concurrently
available in the session table, whichever is larger. available in the session table, whichever is larger.
See Section 6 for more details. See Section 6 for more details.
ks1: (mandatory, algorithm-determined) is the server-side ks1: (mandatory, algorithm-determined) is the server-side
key exchange value K_s1, which is specified by the key exchange value K_s1, which is specified by the
algorithm. algorithm.
nc-max: (mandatory, integer) is the maximal value of nonce nc-max: (mandatory, integer) is the maximal value of nonce
counts that the server accepts. counts that the server accepts.
nc-window: (mandatory, integer) the number of available nonce nc-window: (mandatory, integer) the number of available nonce
skipping to change at page 23, line 29 skipping to change at page 18, line 37
seconds) that the client can reuse the session seconds) that the client can reuse the session
represented by the sid. It is RECOMMENDED to be at represented by the sid. It is RECOMMENDED to be at
least 60. The value of this parameter is not directly least 60. The value of this parameter is not directly
linked to the duration that the server keeps track of linked to the duration that the server keeps track of
the session represented by the sid. the session represented by the sid.
path: (non-mandatory, string) specifies which path in the path: (non-mandatory, string) specifies which path in the
URI space the same authentication is expected to be URI space the same authentication is expected to be
applied. The value is a space-separated list of URIs, applied. The value is a space-separated list of URIs,
in the same format as it was specified in domain in the same format as it was specified in domain
parameter [RFC2617] for the Digest authentications, parameter [RFC2617] for the Digest authentications.
and clients are RECOMMENDED to recognize it. The all The all path elements contained in the parameter MUST
path elements contained in the parameter MUST be be inside the specified auth-domain; if not, clients
inside the specified auth-domain: if not, clients SHOULD ignore such elements. For better performance,
SHOULD ignore such elements. recognition of this parameter by clients are
significantly important.
4.4. req-VFY-C 4.4. req-VFY-C
Every req-VFY-C message SHALL be a valid HTTP request message Every req-VFY-C message SHALL be a valid HTTP request message
containing an "Authorization" header with a credential containing a containing an "Authorization" header with a credential containing a
"vkc" parameter. "vkc" parameter.
The parameters contained in the header are as follows: The parameters contained in the header are as follows:
version: (mandatory, extensive-token) should be the token "-wg- version: (mandatory, extensive-token) should be the token "-wg-
draft00" in this specification. The behavior is draft01".
undefined when other values are specified.
algorithm, validation, auth-domain, realm: MUST be the same value as algorithm, validation, auth-domain, realm: MUST be the same value as
it is when received from the server for the session. it is when received from the server for the session.
sid: (mandatory, hex-fixed-number) MUST be one of the sid sid: (mandatory, hex-fixed-number) MUST be one of the sid
values that was received from the server for the same values that was received from the server for the same
authentication realm. authentication realm.
nc: (mandatory, integer) is a nonce value that is unique nc: (mandatory, integer) is a nonce value that is unique
among the requests sharing the same sid. The values among the requests sharing the same sid. The values
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4.5. 200-VFY-S 4.5. 200-VFY-S
Every 200-VFY-S message SHALL be a valid HTTP message that is not of Every 200-VFY-S message SHALL be a valid HTTP message that is not of
the 401 (Authentication Required) status, containing an the 401 (Authentication Required) status, containing an
"Authentication-Info" header with a "vks" parameter. "Authentication-Info" header with a "vks" parameter.
The parameters contained in the header are as follows: The parameters contained in the header are as follows:
version: (mandatory, extensive-token) should be the token "-wg- version: (mandatory, extensive-token) should be the token "-wg-
draft00" in this specification. The behavior is draft01".
undefined when other values are specified.
sid: (mandatory, hex-fixed-number) MUST be the value sid: (mandatory, hex-fixed-number) MUST be the value
received from the client. received from the client.
vks: (mandatory, algorithm-determined) is the server-side vks: (mandatory, algorithm-determined) is the server-side
authentication verification value VK_s, which is authentication verification value VK_s, which is
specified by the algorithm. specified by the algorithm.
rekey-method: (non-mandatory, extensive-token): defining a
credential used for reestablishing a new session with
a new sid. It must be either omitted or the token
"passwords" at the current specification. The bare-
tokens "refresh-key" and "refresh-key-global" are
reserved for future extensions.
The header MUST be sent before the content body: it MUST NOT be sent The header MUST be sent before the content body: it MUST NOT be sent
in the trailer of a chunked-encoded response. If a "100 Continue" in the trailer of a chunked-encoded response. If a "100 Continue"
response is sent from the server, the Authentication-Info header response is sent from the server, the Authentication-Info header
SHOULD be included in that response, instead of the final response. SHOULD be included in that response, instead of the final response.
5. Authentication Realms 5. Authentication Realms
In this protocol, an "authentication realm" is defined as a set of In this protocol, an "authentication realm" is defined as a set of
resources (URIs) for which the same set of user names and passwords resources (URIs) for which the same set of user names and passwords
is valid for. If the server requests authentication for an is valid for. If the server requests authentication for an
authentication realm that the client is already authenticated for, authentication realm that the client is already authenticated for,
the client will automatically perform the authentication using the the client will automatically perform the authentication using the
already-known secrets. However, for the different authentication already-known secrets. However, for the different authentication
realms, the clients SHOULD NOT automatically reuse the usernames and realms, the clients MUST NOT automatically reuse the user names and
passwords for another realm. passwords for another realm.
Just like in Basic and Digest access authentication protocols, Mutual Just like in Basic and Digest access authentication protocols, Mutual
authentication protocol supports multiple, separate protection spaces authentication protocol supports multiple, separate protection spaces
to be set up inside each host. Furthermore, the protocol supports to be set up inside each host. Furthermore, the protocol supports
that a single authentication realm spans over several hosts within that a single authentication realm spans over several hosts within
the same Internet domain. the same Internet domain.
Each authentication realm is defined and distinguished by the triple Each authentication realm is defined and distinguished by the triple
of an "authentication algorithm", an "authentication domain", and a of an "authentication algorithm", an "authentication domain", and a
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the ASCII character set SHALL be represented in the way they are sent the ASCII character set SHALL be represented in the way they are sent
in the underlying HTTP protocol, represented in lower-case in the underlying HTTP protocol, represented in lower-case
characters; i.e. these SHALL be in the form of the LDH labels in IDNA characters; i.e. these SHALL be in the form of the LDH labels in IDNA
[RFC5890]. All "port"s MUST be in the shortest, unsigned, decimal [RFC5890]. All "port"s MUST be in the shortest, unsigned, decimal
number notation. Not obeying these requirements will cause failure number notation. Not obeying these requirements will cause failure
of valid authentication attempts. of valid authentication attempts.
5.1. Resolving Ambiguities 5.1. Resolving Ambiguities
In the above definitions of authentication domains, several domains In the above definitions of authentication domains, several domains
will overlap each other. Depending on the "path" parameters given in will overlap each other. If a client has already been authenticated
the "401-KEX-S1" message (see Section 4), there may be several to several realms applicable to the same server, the client may have
candidates when the client is going to send a request including an a multiple list of the "path" parameters received with the
authentication credential (Steps 3 and 4 of the decision procedure "401-KEX-S1" message (see Section 4). If these path lists have any
presented in Section 9). overlap, a single URI may belong to multiple possible candidate of
realms to be authenticated to. In such cases, clients faces an
ambiguity on deciding which credentials to be sent for a new request
(in steps 3 and 4 of the decision procedure presented in Section 9).
If such choices are required, the following procedure SHOULD be In such cases, clients MAY send requests which belongs to any of
followed. these candidate realms freely, or it MAY simply send an
unauthenticated request and see for which realm the server request an
authentication. Server operators are RECOMMENDED to provide
properly-configured "path" parameters (more precisely, disjoint path
sets for each realms) for clients so that such ambiguities will not
occur.
The following procedure are one of the possible tactics for resolving
ambiguity in such cases.
o If the client has previously sent a request to the same URI, and o If the client has previously sent a request to the same URI, and
if it remembers the authentication realm requested by 401-INIT if it remembers the authentication realm requested by 401-INIT
messages at that time, use that realm. messages at that time, use that realm.
o In other cases, use one of authentication realms representing the o In other cases, use one of authentication realms representing the
most-specific authentication domains. From the list of possible most-specific authentication domains. From the list of possible
domain specifications shown above, each one earlier has priority domain specifications shown above, each one earlier has priority
over ones described after that. over ones described after that.
If there are several choices with different domain-postfix If there are several choices with different domain-postfix
specifications, the one that has the longest domain-postfix has specifications, the one that has the longest domain-postfix has
priority over ones with a shorter domain-postfix. priority over ones with a shorter domain-postfix.
o If there are realms with the same authentication domain, there is o If there are realms with the same authentication domain, there is
no defined priority: the client MAY choose any one of the possible no defined priority: the client MAY choose any one of the possible
choices. choices.
If possible, server operators are encouraged to avoid such
ambiguities by properly setting the "path" parameters.
6. Session Management 6. Session Management
In the Mutual authentication protocol, a session represented by an In the Mutual authentication protocol, a session represented by an
sid is set up using first four messages (first request, 401-INIT, sid is set up using first four messages (first request, 401-INIT,
req-KEX-C1 and 401-KEX-S1), and a "session secret" (z) associated req-KEX-C1 and 401-KEX-S1), and a "session secret" (z) associated
with the session is established. After sharing a session secret, with the session is established. After sharing a session secret,
this session, along with the secret, can be used for one or more this session, along with the secret, can be used for one or more
requests for resources protected by the same realm in the same requests for resources protected by the same realm in the same
server. Note that session management is only an inside detail of the server. Note that session management is only an inside detail of the
protocol and usually not visible to normal users. If a session protocol and usually not visible to normal users. If a session
expires, the client and server SHOULD automatically re-establish expires, the client and server SHOULD automatically re-establish
another session without informing the users. another session without informing the users.
Sessions and session identifiers are local to each server (defined by Sessions and session identifiers are local to each server (defined by
scheme, host and port) inside an authentication domain; the clients scheme, host and port), even if an authentication domain covers
MUST establish separate sessions for each port of a host to be multiple servers; the clients MUST establish separate sessions for
accessed. Furthermore, sessions and identifiers are also local to each port of a host to be accessed. Furthermore, sessions and
each authentication realm, even if these are provided from the same identifiers are also local to each authentication realm, even if
server. The same session identifiers provided either from different these are provided from the same server. The same session
servers or for different realms SHOULD be treated as independent identifiers provided either from different servers or for different
ones. realms MUST be treated as independent ones.
The server SHOULD accept at least one req-VFY-C request for each The server SHOULD accept at least one req-VFY-C request for each
session, given that the request reaches the server in a time window session, given that the request reaches the server in a time window
specified by the timeout parameter in the 401-KEX-S1 message, and specified by the timeout parameter in the 401-KEX-S1 message, and
that there are no emergent reasons (such as flooding attacks) to that there are no emergent reasons (such as flooding attacks) to
forget the sessions. After that, the server MAY discard any session forget the sessions. After that, the server MAY discard any session
at any time and MAY send 401-STALE messages for any req-VFY-C at any time and MAY send 401-STALE messages for any req-VFY-C
requests. requests.
The client MAY send two or more requests using a single session The client MAY send two or more requests using a single session
skipping to change at page 28, line 30 skipping to change at page 23, line 37
{41-44, 61-62, 73-100}. The values {0, 21, 23, 25-29, 39-40} MAY be {41-44, 61-62, 73-100}. The values {0, 21, 23, 25-29, 39-40} MAY be
rejected by the server because they are not above the current "window rejected by the server because they are not above the current "window
limit" (40 = 72 - 32). limit" (40 = 72 - 32).
Typically, clients can ensure the above property by using a Typically, clients can ensure the above property by using a
monotonically-increasing integer counter that counts from zero upto monotonically-increasing integer counter that counts from zero upto
the value of nc-max. the value of nc-max.
The values of the nonces and any nonce-related values MUST always be The values of the nonces and any nonce-related values MUST always be
treated as natural numbers within an infinite range. Implementations treated as natural numbers within an infinite range. Implementations
using fixed-width integers or fixed-precision floating numbers MUST which uses fixed-width integer representations, fixed-precision
correctly and carefully handle integer overflows. Such floating numbers or similar representations SHOULD NOT reject any
implementations are RECOMMENDED to accept any larger values that larger values which overflow such representative limits, and MUST NOT
cannot be represented in the fixed-width integer representations, as silently truncate it using any modulus-like rounding operation (e.g.
long as other limits such as internal header-length restrictions are by mod 2^32). Instead, the whole protocol is carefully designed so
not involved. The protocol is designed carefully so that both the that recipients MAY replace any such overflowed values (e.g. 2^80)
clients and servers can implement the protocol using only fixed-width with some reasonably-large maximal representative integer (e.g. 2^31
integers, by rounding any overflowed values to the maximum possible - 1 or others).
value.
7. Host Validation Methods 7. Host Validation Methods
The "validation method" specifies a method to "relate" (or "bind") The "validation method" specifies a method to "relate" (or "bind")
the mutual authentication processed by this protocol with other the mutual authentication processed by this protocol with other
authentications already performed in the underlying layers and to authentications already performed in the underlying layers and to
prevent man-in-the-middle attacks. It decides the value vh that is prevent man-in-the-middle attacks. It decides the value vh that is
an input to the authentication protocols. an input to the authentication protocols.
When HTTPS or other possible secure transport is used, this
corresponds to the idea of "channel binding" described in [RFC5929].
Even when HTTP is used, similar, but somewhat limited, "binding" is
performed to prevent a malicious server from trying to authenticate
themselves to another server as a valid user by forwarding the
received credentials.
The valid tokens for the validation parameter and corresponding The valid tokens for the validation parameter and corresponding
values of vh are as follows: values of vh are as follows:
host: hostname validation: The value vh will be the ASCII host: host-name validation: The value vh will be the ASCII
string in the following format: string in the following format:
"<scheme>://<host>:<port>", where <scheme>, <host>, "<scheme>://<host>:<port>", where <scheme>, <host>,
and <port> are the URI components corresponding to the and <port> are the URI components corresponding to the
currently accessing resource. The scheme and host are currently accessing resource. The scheme and host are
in lower-case, and the port is in a shortest decimal in lower-case, and the port is in a shortest decimal
representation. Even if the request-URI does not have representation. Even if the request-URI does not have
a port part, v will include the default port number. a port part, v will include the default port number.
tls-cert: TLS certificate validation: The value vh will be the tls-server-end-point: TLS endpoint (certificate) validation: The
octet string of the hash value of the public key value vh will be the octet string of the hash value of
certificate used in the underlying TLS [RFC5246] (or the server's public key certificate used in the
SSL) connection. The hash value is defined as the underlying TLS [RFC5246] (or SSL) connection,
value of the entire signed certificate (specified as processed as specified in Section 4.1 of [RFC5929].
"Certificate" in [RFC5280]), hashed by the hash
algorithm specified by the authentication algorithm
used.
tls-key: TLS shared-key validation: The value v will be the [[Pending editorial issue: a small security issue is
octet string of the shared master secret negotiated in pending around here, awaiting analysis and WG
the underlying TLS (or SSL) connection. discussions for final adoption.]]
tls-unique: TLS shared-key validation: The value v will be the
channel binding material derived from the Finished
messages, as defined in Section 3.1 of [RFC5929].
If the HTTP protocol is used on a non-encrypted channel (TCP and If the HTTP protocol is used on a non-encrypted channel (TCP and
SCTP, for example), the validation type MUST be "host". If HTTP/TLS SCTP, for example), the validation type MUST be "host". If HTTP/TLS
[RFC2818] (HTTPS) protocol is used with the server certificates, the [RFC2818] (HTTPS) protocol is used with the server certificates, the
validation type MUST be "tls-cert". If HTTP/TLS protocol is used validation type MUST be "tls-server-end-point". If HTTP/TLS protocol
with an anonymous Diffie-Hellman key exchange, the validation type is used with an anonymous Diffie-Hellman key exchange, the validation
MUST be "tls-key" (see the note below). type MUST be "tls-unique" (see the note below).
If the validation type "tls-cert" is used, the server certificate Implementations supporting a Mutual authentication over the HTTPS
provided on TLS connection MUST be verified to make sure that the protocol SHOULD support the "tls-server-end-point" validation.
server actually owns the corresponding secret key. Support for "tls-unique" validation is OPTIONAL for both the servers
and clients.
If the validation type "tls-server-end-point" is used, the server
certificate provided on TLS connection MUST be verified at least to
make sure that the server actually owns the corresponding secret key.
(Note: this verification is automatic in some RSA-based key exchanges
but NOT automatic in Diffie-Hellman-based key exchanges with separate
exchange for server verifications.)
Clients MUST validate this parameter upon reception of the 401-INIT Clients MUST validate this parameter upon reception of the 401-INIT
messages. messages.
However, when the client is a Web browser with any scripting
capabilities, the underlying TLS channel used with HTTP/TLS MUST
provide server identity verification. This means (1) the anonymous
Diffie-Hellman key exchange ciphersuite MUST NOT be used, and (2) the
verification of the server certificate provided from the server MUST
be performed.
For other systems, when the underlying TLS channel used with HTTP/TLS
does not perform server identity verification, the client SHOULD
ensure that all the responses are validated using the Mutual
authentication protocol, regardless of the existence of the 401-INIT
responses.
Note: The protocol defines two variants for validation on the TLS Note: The protocol defines two variants for validation on the TLS
connections. The "tls-key" method is more secure. However, there connections. The "tls-unique" method is more secure. However, there
are some situations where tls-cert is more preferable. are some situations where tls-server-end-point is more preferable.
o When TLS accelerating proxies are used, it is difficult for the o When TLS accelerating proxies are used, it is difficult for the
authenticating server to acquire the TLS key information that is authenticating server to acquire the TLS key information that is
used between the client and the proxy. This is not the case for used between the client and the proxy. This is not the case for
client-side "tunneling" proxies using a CONNECT method extension client-side "tunneling" proxies using a CONNECT method extension
of HTTP. of HTTP.
o When a black-box implementation of the TLS protocol is used on o When a black-box implementation of the TLS protocol is used on
either peer. either peer.
Implementations supporting a Mutual authentication over the HTTPS 7.1. Applicability notes
protocol SHOULD support the "tls-cert" validation. Support for
"tls-key" validation is OPTIONAL for both the servers and clients. When the client is a Web browser with any scripting capabilities, the
underlying TLS channel used with HTTP/TLS MUST provide server
identity verification. This means (1) the anonymous Diffie-Hellman
key exchange cipher-suite MUST NOT be used, and (2) the verification
of the server certificate provided from the server MUST be performed.
For other systems, when the underlying TLS channel used with HTTP/TLS
does not perform server identity verification, the client SHOULD
ensure that all the responses are validated using the Mutual
authentication protocol, regardless of the existence of the 401-INIT
responses.
7.2. Interoperability notes on tls-unique
As described in the interoperability note in the above channel
binding specification, the tls-unique verification value will be
changed by possible TLS renegotiation, causing an interoperability
problem. TLS re-negotiations are used in several HTTPS server
implementations for enforcing some security properties (such as
cryptographic strength) for some specific responses.
If an implementation supports "tls-unique" verification method, the
following caution SHOULD be taken:
o Both peers must be aware that the values vh used for vkc (in
req-VFY-C) and for vks (in 200-VFY-S) may be different. These
values MUST be retrieved from underlying TLS libraries each time
it is used.
o After calculating value vh and vkc to send a req-VFY-C request,
Clients SHOULD NOT initiate TLS renegotiation until the end of the
corresponding response header is received. Exceptionally, Clients
can and SHOULD perform TLS re-negotiation as a response to
server's request for TLS renegotiation, occurring before the top
of response header.
8. Authentication Extensions 8. Authentication Extensions
Interactive clients (e.g. Web browsers) supporting this protocol are Interactive clients (e.g. Web browsers) supporting this protocol are
RECOMMENDED to support non-mandatory authentication and the RECOMMENDED to support non-mandatory authentication and the
Authentication-Control header defined there, except the "auth-style" Authentication-Control header defined in
parameter. This specification also proposes (however, not mandates) [I-D.ietf-httpauth-extension], except the "auth-style" parameter.
default "auth-style" to be "non-modal". Web applications SHOULD This specification also proposes (however, not mandates) default
however consider the security impacts of the behaviors of clients "auth-style" to be "non-modal". Web applications SHOULD however
that do not support these headers. consider the security impacts of the behaviors of clients that do not
support these headers.
Authentication-initializing messages with the Authentication-initializing messages with the
Optional-WWW-Authenticate header are used where 401-INIT response is Optional-WWW-Authenticate header are used only where 401-INIT
valid. Such a message is called a 200-Optional-INIT message in this response is valid. It will not replace other 401-type messages such
document. (It will not replace other 401-type messages such as as 401-STALE and 401-KEX-S1.
401-STALE and 401-KEX-S1.)
9. Decision Procedure for Clients 9. Decision Procedure for Clients
To securely implement the protocol, the user client must be careful To securely implement the protocol, the user client must be careful
about accepting the authenticated responses from the server. This about accepting the authenticated responses from the server. This
also holds true for the reception of "normal responses" (responses also holds true for the reception of "normal responses" (responses
which do not contain Mutual-related headers) from HTTP servers. which do not contain Mutual-related headers) from HTTP servers.
Clients SHOULD implement a decision procedure equivalent to the one Clients SHOULD implement a decision procedure equivalent to the one
shown below. (Unless implementers understand what is required for shown below. (Unless implementers understand what is required for
skipping to change at page 31, line 24 skipping to change at page 27, line 23
Check whether there is an available sid for the authentication Check whether there is an available sid for the authentication
realm you expect. If there is one, go to Step 3. Otherwise, go realm you expect. If there is one, go to Step 3. Otherwise, go
to Step 4. to Step 4.
Step 3 (step_send_vfy_1): Step 3 (step_send_vfy_1):
Send a req-VFY-C request. Send a req-VFY-C request.
* If you receive a 401-INIT message with a different * If you receive a 401-INIT message with a different
authentication realm than expected, go to Step 6. authentication realm than expected, go to Step 6.
* If you receive a 200-Optional-INIT message with a different
authentication realm than expected, go to Step 6.
* If you receive a 401-STALE message, go to Step 9. * If you receive a 401-STALE message, go to Step 9.
* If you receive a 401-INIT message, go to Step 13. * If you receive a 401-INIT message, go to Step 13.
* If you receive a 200-VFY-S message, go to Step 14. * If you receive a 200-VFY-S message, go to Step 14.
* If you receive a normal response, go to Step 11. * If you receive a normal response, go to Step 11.
Step 4 (step_send_kex1_1): Step 4 (step_send_kex1_1):
Send a req-KEX-C1 request. Send a req-KEX-C1 request.
* If you receive a 401-INIT message with a different * If you receive a 401-INIT message with a different
authentication realm than expected, go to Step 6. authentication realm than expected, go to Step 6.
* If you receive a 200-Optional-INIT message with a different
authentication realm than expected, go to Step 6.
* If you receive a 401-KEX-S1 message, go to Step 10. * If you receive a 401-KEX-S1 message, go to Step 10.
* If you receive a 401-INIT message with the same authentication * If you receive a 401-INIT message with the same authentication
realm, go to Step 13 (see Note 1). realm, go to Step 13 (see Note 1).
* If you receive a normal response, go to Step 11. * If you receive a normal response, go to Step 11.
Step 5 (step_send_normal_1): Step 5 (step_send_normal_1):
Send a request without any Mutual authentication headers. Send a request without any Mutual authentication headers.
* If you receive a 401-INIT message, go to Step 6. * If you receive a 401-INIT message, go to Step 6.
* If you receive a 200-Optional-INIT message, go to Step 6.
* If you receive a normal response, go to Step 11. * If you receive a normal response, go to Step 11.
Step 6 (step_rcvd_init): Step 6 (step_rcvd_init):
Check whether you know the user's password for the requested Check whether you know the user's password for the requested
authentication realm. If yes, go to Step 7. Otherwise, go to authentication realm. If yes, go to Step 7. Otherwise, go to
Step 12. Step 12.
Step 7: Step 7:
Check whether there is an available sid for the authentication Check whether there is an available sid for the authentication
realm you expect. If there is one, go to Step 8. Otherwise, go realm you expect. If there is one, go to Step 8. Otherwise, go
skipping to change at page 33, line 19 skipping to change at page 29, line 12
from the server, and to ask user for a user name and a password. from the server, and to ask user for a user name and a password.
When those are supplied from the user, proceed to Step 9. When those are supplied from the user, proceed to Step 9.
Step 13 (step_rcvd_init_failed): Step 13 (step_rcvd_init_failed):
For some reason the authentication failed: possibly the password For some reason the authentication failed: possibly the password
or the username is invalid for the authenticated resource. or the username is invalid for the authenticated resource.
Forget the password for the authentication realm and go to Step Forget the password for the authentication realm and go to Step
12. 12.
Step 14 (step_rcvd_vfy): Step 14 (step_rcvd_vfy):
Check the validity of the received VK_s value. If it is equal to The received message is the 200-VFY-S message, which SHALL always
the expected value, it means that the mutual authentication has contain a vks field. Check the validity of the received VK_s
succeeded. The client will be in the "AUTH-SUCCEEDED" status. value. If it is equal to the expected value, it means that the
mutual authentication has succeeded. The client will be in the
"AUTH-SUCCEEDED" status.
If the value is unexpected, it is a fatal communication error. If the value is unexpected, it is a fatal communication error.
If a user explicitly requests to log out (via user interfaces), If a user explicitly requests to log out (via user interfaces),
the client MUST forget the user's password, go to step 5 and the client MUST forget the user's password, go to step 5 and
reload the current resource without an authentication header. reload the current resource without an authentication header.
Note 1: These transitions MAY be accepted by clients, but Note 1: These transitions MAY be accepted by clients, but
NOT RECOMMENDED for servers to initiate. NOT RECOMMENDED for servers to initiate.
Any kind of response (including a normal response) other than those Any kind of response (including a normal response) other than those
shown in the above procedure SHOULD be interpreted as a fatal shown in the above procedure SHOULD be interpreted as a fatal
communication error, and in such cases the clients MUST NOT process communication error, and in such cases the clients MUST NOT process
any data (response body and other content-related headers) sent from any data (response body and other content-related headers) sent from
the server. However, to handle exceptional error cases, clients MAY the server. However, to handle exceptional error cases, clients MAY
accept a message without an Authentication-Info header, if it is a accept a message without an Authentication-Info header, if it is a
Server-Error (5xx) status. The client will be in the Server-Error (5xx) status. In such cases, they SHOULD be careful
"UNAUTHENTICATED" status in these cases. about processing the body of the content (ignoring it is still
RECOMMENDED), and the client will be in the "UNAUTHENTICATED" status
then.
The client software SHOULD display the three client status to the If a request is a sub-request for a resource included in another
end-user. For an interactive client, however, if a request is a sub- resources (e.g., embedded images, style sheets, frames etc.), clients
request for a resource included in another page (e.g., embedded MAY treat an AUTH-REQUESTED status as the same as UNAUTHENTICATED
images, style sheets, frames etc.), its status MAY be omitted from status. In other words, the client MAY ignore server's request to
being shown, and any "AUTH-REQUESTED" statuses MAY be treated in the start authentication with new credentials via sub-requests.
same way as an "UNAUTHENTICATED" status.
Figure 5 shows a diagram of the client-side state. Figure 5 shows a diagram of the client-side state.
=========== -(11)------------ =========== -(11)------------
NEW REQUEST ( UNAUTHENTICATED ) NEW REQUEST ( UNAUTHENTICATED )
=========== ----------------- =========== -----------------
| ^ normal | ^ normal
v | response v | response
+(1)-------------------+ NO +(5)----------+ +(1)-------------------+ NO +(5)----------+
| The requested URI |--------------------------->| send normal | | The requested URI |--------------------------->| send normal |
| known to be auth'ed? | | request | | known to be auth'ed? | | request |
+----------------------+ +-------------+ +----------------------+ +-------------+
YES | 401-INIT, 200-Optional-INIT 401-INIT| YES | 401-INIT 401-INIT|
| with a different realm 200-Optional-INIT| | with a different realm |
| -----------------------------------. | | -----------------------------------. |
| / v v | / v v
| | -(12)------------ NO +(6)--------+ | | -(12)------------ NO +(6)--------+
| | ( AUTH-REQUESTED )<------| user/pass | | | ( AUTH-REQUESTED )<------| user/pass |
| | ----------------- | known? | | | ----------------- | known? |
| | +-----------+ | | +-----------+
| | |YES | | |YES
v | v v | v
+(2)--------+ | +(7)--------+ +(2)--------+ | +(7)--------+
| session | | | session | NO | session | | | session | NO
skipping to change at page 35, line 40 skipping to change at page 31, line 40
* The largest nc received from the client (largest-nc) * The largest nc received from the client (largest-nc)
* For each possible nc values between (largest-nc - nc- * For each possible nc values between (largest-nc - nc-
window + 1) and max_nc, a flag whether or not a request with window + 1) and max_nc, a flag whether or not a request with
the corresponding nc has been received. the corresponding nc has been received.
The table MAY contain other information. The table MAY contain other information.
Servers SHOULD respond to the client requests according to the Servers SHOULD respond to the client requests according to the
following procedure: following procedure: (See Note 1 below for 401-INIT message with *
marks)
o When the server receives a normal request: o When the server receives a normal request:
* If the requested resource is not protected by the Mutual * If the requested resource is not protected by the Mutual
Authentication, send a normal response. Authentication, send a normal response.
* If the resource is protected by the Mutual Authentication, send * If the resource is protected by the Mutual Authentication, send
a 401-INIT response. a 401-INIT response.
* If the resource is protected by the optional Mutual
Authentication, send a 200-Optional-INIT response.
o When the server receives a req-KEX-C1 request: o When the server receives a req-KEX-C1 request:
* If the requested resource is not protected by the Mutual * If the requested resource is not protected by the Mutual
Authentication, send a normal response. Authentication, send a normal response.
* If the authentication realm specified in the req-KEX-C1 request * If the authentication realm specified in the req-KEX-C1 request
is not the expected one, send either a 401-INIT or a is not the expected one, send a 401-INIT response.
200-Optional-INIT response.
* If the server cannot validate the parameter kc1, send a * If the server cannot validate the parameter kc1, send a
401-INIT response. 401-INIT (*) response.
* If the received user name is either invalid, unknown or * If the received user name is either invalid, unknown or
unacceptable, create a new session, mark it a "fake" session, unacceptable, create a new session, mark it a "fake" session,
compute a random value as K_s1, and send a fake 401-KEX-S1 compute a random value as K_s1, and send a fake 401-KEX-S1
response. (Note: the server SHOULD NOT send a 401-INIT response. (Note 2)
response in this case, because it will leak the information to
the client that the specified user will not be accepted.
Instead, postpone it to the response for the next req-VFY-C
request.)
* Otherwise, create a new session, compute K_s1 and send a * Otherwise, create a new session, compute K_s1 and send a
401-KEX-S1 response. 401-KEX-S1 response.
The created session has the "key exchanging" state. The created session has the "key exchanging" state.
o When the server receives a req-VFY-C request: o When the server receives a req-VFY-C request:
* If the requested resource is not protected by the Mutual * If the requested resource is not protected by the Mutual
Authentication, send a normal response. Authentication, send a normal response.
* If the authentication realm specified in the req-VFY-C request * If the authentication realm specified in the req-VFY-C request
is not the expected one, send either a 401-INIT or a is not the expected one, send a 401-INIT response.
200-Optional-INIT response.
If none of above holds true, the server will lookup the session If none of above holds true, the server will lookup the session
corresponding to the received sid and the authentication realm. corresponding to the received sid and the authentication realm.
* If the session corresponding to the received sid could not be * If the session corresponding to the received sid could not be
found, or it is in the "inactive" state, send a 401-STALE found, or it is in the "inactive" state, send a 401-STALE
response. response.
* If the session is in the "rejected" state, send either a * If the session is in the "rejected" state, send either a
401-INIT or a 401-STALE message. 401-INIT (*) or a 401-STALE message.
* If the session is in the "authenticated" state, and the request * If the session is in the "authenticated" state, and the request
has an nc value that was previously received from the client, has an nc value that was previously received from the client,
send a 401-STALE message. The session SHOULD be changed to the send a 401-STALE message. The session SHOULD be changed to the
"inactive" status. "inactive" status.
* If the nc value in the request is larger than the nc-max * If the nc value in the request is larger than the nc-max
parameter sent from the server, or if it is not larger then parameter sent from the server, or if it is not larger then
(largest-nc - nc-window) (when in "authenticated" status), the (largest-nc - nc-window) (when in "authenticated" status), the
server MAY (but not REQUIRED to) send a 401-STALE message. The server MAY (but not REQUIRED to) send a 401-STALE message. The
session SHOULD be changed to the "inactive" status if so. session SHOULD be changed to the "inactive" status if so.
* If the session is a "fake" session, or if the received vkc is * If the session is a "fake" session, or if the received vkc is
incorrect, then send a 401-INIT response. If the session is in incorrect, then send a 401-INIT (*) response. If the session
the "key exchanging" state, it SHOULD be changed to the is in the "key exchanging" state, it SHOULD be changed to the
"rejected" state; otherwise, it MAY either be changed to the "rejected" state; otherwise, it MAY either be changed to the
"rejected" status or kept in the previous state. "rejected" status or kept in the previous state.
* Otherwise, send a 200-VFY-S response. If the session was in * Otherwise, send a 200-VFY-S response. If the session was in
the "key exchanging" state, the session SHOULD be changed to an the "key exchanging" state, the session SHOULD be changed to an
"authenticated" state. The maximum nc and nc flags of the "authenticated" state. The maximum nc and nc flags of the
state SHOULD be updated properly. state SHOULD be updated properly.
At any time, the server MAY change any state entries with both the At any time, the server MAY change any state entries with both the
"rejected" and "authenticated" statuses to the "inactive" status, and "rejected" and "authenticated" statuses to the "inactive" status, and
MAY discard any "inactive" states from the table. The entries with MAY discard any "inactive" states from the table. The entries with
the "key exchanging" status SHOULD be kept unless there is an the "key exchanging" status SHOULD be kept unless there is an
emergency situation such as a server reboot or a table capacity emergency situation such as a server reboot or a table capacity
overflow. overflow.
Note 1: In relation with, and following the specification of the
optional authentication defined in [I-D.ietf-httpauth-extension], the
401-INIT messages marked with the asterisks can not be replaced with
a successful responses with an Optional-WWW-Authenticate header.
Every other 401-INIT can be a response with an
Optional-WWW-Authenticate.
Note 2: the server SHOULD NOT send a 401-INIT response in this case,
because it will leak the information to the client that the specified
user will not be accepted. Instead, postpone it to the response for
the next req-VFY-C request.
11. Authentication Algorithms 11. Authentication Algorithms
Cryptographic authentication algorithms which are used with this Cryptographic authentication algorithms which are used with this
protocol will be defined separately. The algorithm definition MUST protocol will be defined separately. The algorithm definition MUST
at least provide a definitions for the following functions: at least provide a definitions for the following functions:
o The server-side authentication credential J, derived from user- o The server-side authentication credential J, derived from user-
side authentication credential pi. side authentication credential pi.
o Key exchange values K_c1, K_s1 (exchanged on wire) and S_c1, S_s1 o Key exchange values K_c1, K_s1 (exchanged on wire) and S_c1, S_s1
skipping to change at page 39, line 14 skipping to change at page 35, line 21
VI(1000000) = "\275\204@" VI(1000000) = "\275\204@"
VS("") = "\000" VS("") = "\000"
VS("Tea") = "\003Tea" VS("Tea") = "\003Tea"
VS("Caf<e acute>" [in UTF-8]) = "\005Caf\303\251" VS("Caf<e acute>" [in UTF-8]) = "\005Caf\303\251"
VS([10000 "a"s]) = "\316\020aaaaa..." (10002 octets) VS([10000 "a"s]) = "\316\020aaaaa..." (10002 octets)
[Editorial note: Unlike the colon-separated notion used in the Basic/ (Note: Unlike the colon-separated notion used in the Basic/Digest
Digest HTTP authentication scheme, the string generated by a HTTP authentication scheme, the string generated by a concatenation
concatenation of the VS-encoded strings will be unique, regardless of of the VS-encoded strings will be unique, regardless of the
the characters included in the strings to be encoded.] characters included in the strings to be encoded.)
The function OCTETS converts an integer into the corresponding radix- The function OCTETS converts an integer into the corresponding radix-
256 big-endian octet string having its natural length: See 256 big-endian octet string having its natural length: See
Section 3.1.3 for the definition of "natural length". Section 3.1.3 for the definition of "natural length".
The function INT converts an octet string into a natural number,
where the input string is treated as a radix-256 big-endian notation.
The identity INT(OCTETS(n)) = n always holds for any natural number
n.
11.2. Default Functions for Algorithms 11.2. Default Functions for Algorithms
The functions defined in this section are common default functions The functions defined in this section are common default functions
among authentication algorithms. among authentication algorithms.
The client-side password-based string pi used by this authentication The client-side password-based (credential) pi used by this
is derived in the following manner: authentication is a natural number derived in the following manner:
pi = H(VS(algorithm) | VS(auth-domain) | VS(realm) | VS(username) | pi = INT(H(VS(algorithm) | VS(auth-domain) | VS(realm) | VS(username)
VS(ph(password))). | VS(ph(password)))).
The values of algorithm, realm, and auth-domain are taken from the The values of algorithm, realm, and auth-domain are taken from the
values contained in the 401-INIT (or 200-Optional-INIT, hereafter values contained in the 401-INIT message. The function ph is
implied) message. When pi is used in the context of an octet string,
it SHALL have the natural length derived from the size of the output
of function H (e.g. 32 octets for SHA-256). The function ph is
determined by the value of the pwd-hash parameter given in a 401-INIT determined by the value of the pwd-hash parameter given in a 401-INIT
message. If the password comes from a user input, it SHOULD first be message. If the password comes from a user input, it SHOULD first be
prepared using SASLprep [RFC4013]. Then, the password SHALL be prepared using I-D.oiwa-precis-httpauthprep [RFC4013]. Then, the
encoded as a UTF-8 string before passed to ph. password SHALL be encoded as a UTF-8 string before passed to ph.
The values VK_c and VK_s are derived by the following equation. The values VK_c and VK_s are derived by the following equation.
VK_c = H(octet(4) | OCTETS(K_c1) | OCTETS(K_s1) | OCTETS(z) | VI(nc) VK_c = INT(H(octet(4) | OCTETS(K_c1) | OCTETS(K_s1) | OCTETS(z) |
| VS(vh)) VI(nc) | VS(vh)))
VK_s = INT(H(octet(3) | OCTETS(K_c1) | OCTETS(K_s1) | OCTETS(z) |
VI(nc) | VS(vh)))
VK_s = H(octet(3) | OCTETS(K_c1) | OCTETS(K_s1) | OCTETS(z) | VI(nc)
| VS(vh))
Specifications for cryptographic algorithms used with this framework Specifications for cryptographic algorithms used with this framework
MAY override the functions pi, VK_c, and VK_s defined above. In such MAY override the functions pi, VK_c, and VK_s defined above. In such
cases implementations MUST use the ones defined with such algorithm cases implementations MUST use the ones defined with such algorithm
specifications. specifications.
12. Application Channel Binding 12. Application Channel Binding
Applications and upper-layer communication protocols may need Applications and upper-layer communication protocols may need
authentication binding to the HTTP-layer authenticated user. Such authentication binding to the HTTP-layer authenticated user. Such
applications MAY use the following values as a standard shared applications MAY use the following values as a standard shared
skipping to change at page 40, line 25 skipping to change at page 36, line 34
These values are parameterized with an optional octet string (t) These values are parameterized with an optional octet string (t)
which may be arbitrarily chosen by each applications or protocols. which may be arbitrarily chosen by each applications or protocols.
If there is no appropriate value to be specified, use a null string If there is no appropriate value to be specified, use a null string
for t. for t.
For applications requiring binding to either an authenticated user or For applications requiring binding to either an authenticated user or
a shared-key session (to ensure that the requesting client is a shared-key session (to ensure that the requesting client is
certainly authenticated), the following value b_1 MAY be used. certainly authenticated), the following value b_1 MAY be used.
b_1 = OCTETS(H(OCTETS(H(octet(6) | OCTETS(K_c1) | OCTETS(K_s1) | b_1 = H(H(octet(6) | OCTETS(K_c1) | OCTETS(K_s1) | OCTETS(z) | VI(0)
OCTETS(z) | VI(0) | VS(vh))) | VS(t))). | VS(vh)) | VS(t)).
For applications requiring binding to a specific request (to ensure For applications requiring binding to a specific request (to ensure
that the payload data is generated for the exact HTTP request), the that the payload data is generated for the exact HTTP request), the
following value b_2 MAY be used. following value b_2 MAY be used.
b_2 = OCTETS(H(OCTETS(H(octet(7) | OCTETS(K_c1) | OCTETS(K_s1) | b_2 = H(H(octet(7) | OCTETS(K_c1) | OCTETS(K_s1) | OCTETS(z) | VI(nc)
OCTETS(z) | VI(nc) | VS(vh))) | VS(t))). | VS(vh)) | VS(t)).
Note: Channel bindings to lower-layer transports (TCP and TLS) are Note: Channel bindings to lower-layer transports (TCP and TLS) are
defined in Section 7. defined in Section 7.
13. Application for Proxy Authentication 13. Application for Proxy Authentication
The authentication scheme defined by the previous sections can be The authentication scheme defined by the previous sections can be
applied m.m. for proxy authentications. In such cases, the following applied (with modifications) for proxy authentications. In such
alterations MUST be applied: cases, the following alterations MUST be applied:
o The 407 status is to be sent and recognized for places where the o The 407 status is to be sent and recognized for places where the
401 status is used, 401 status is used,
o Proxy-Authenticate: header is to be used for places where WWW- o Proxy-Authenticate: header is to be used for places where WWW-
Authenticate: is used, Authenticate: is used,
o Proxy-Authorization: header is to be used for places where o Proxy-Authorization: header is to be used for places where
Authorization: is used, Authorization: is used,
skipping to change at page 41, line 25 skipping to change at page 37, line 32
o The limitation for the paths contained in the path parameter of o The limitation for the paths contained in the path parameter of
401-KEX-S1 messages is disregarded, 401-KEX-S1 messages is disregarded,
o The omission of the path parameter of 401-KEX-S1 messages means o The omission of the path parameter of 401-KEX-S1 messages means
that the authentication realm will potentially cover all requests that the authentication realm will potentially cover all requests
processed by the proxy, processed by the proxy,
o The scheme, host name and the port of the proxy is used for host o The scheme, host name and the port of the proxy is used for host
validation tokens, and validation tokens, and
o Authentication extension in [I-D.ietf-httpauth-extension] is not o Authentication extensions in [I-D.ietf-httpauth-extension] are not
applicable. applicable.
The requirements for client software to display the authentication
status to the end-user is also not applicable for proxy
authentication. If the client software supports both end-to-end and
proxy authentication using this protocol, it SHOULD be careful that
the authentication status of the proxy communication will never be
confused by users with authentication statuses of the end-to-end
resource authentications.
14. Methods to Extend This Protocol 14. 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-tokens defined in Section 3 to avoid conflicts with the extension-tokens defined in Section 3 to avoid conflicts with
this protocol and other extensions. (standardized or being- this protocol and other extensions. (standardized or being-
standardizing extensions MAY use either bare-tokens or extension- standardizing extensions MAY use either bare-tokens or extension-
tokens.) tokens.)
Specifications defining authentication algorithms MAY use other Specifications defining authentication algorithms MAY use other
representations for the parameters "kc1", "ks1", "vkc", and "vks", representations for the parameters "kc1", "ks1", "vkc", and "vks",
skipping to change at page 42, line 31 skipping to change at page 38, line 31
meet the RFC 5226 requirements. meet the RFC 5226 requirements.
16. Security Considerations 16. Security Considerations
16.1. Security Properties 16.1. Security Properties
o The protocol is secure against passive eavesdropping and replay o The protocol is secure against passive eavesdropping and replay
attacks. However, the protocol relies on transport security attacks. However, the protocol relies on transport security
including DNS integrity for data secrecy and integrity. HTTP/TLS including DNS integrity for data secrecy and integrity. HTTP/TLS
SHOULD be used where transport security is not assured and/or data SHOULD be used where transport security is not assured and/or data
secrecy is important. confidentiality is important.
o When used with HTTP/TLS, if TLS server certificates are reliably o When used with HTTP/TLS, if TLS server certificates are reliably
verified, the protocol provides true protection against active verified, the protocol provides true protection against active
man-in-the-middle attacks. man-in-the-middle attacks.
o Even if the server certificate is not used or is unreliable, the o Even if the server certificate is not used or is unreliable, the
protocol provides protection against active man-in-the-middle protocol provides protection against active man-in-the-middle
attacks for each HTTP request/response pair. However, in such attacks for each HTTP request/response pair. However, in such
cases, JavaScript or similar scripting facilities can be used to cases, JavaScript or similar scripting facilities can be used to
affect the Mutually-authenticated contents from other contents not affect the Mutually-authenticated contents from other contents not
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verification request is processed for each session identifier. After verification request is processed for each session identifier. After
that, servers MAY discard sessions internally at any time, without that, servers MAY discard sessions internally at any time, without
causing any operational problems to clients. Clients will silently causing any operational problems to clients. Clients will silently
reestablishes a new session then. reestablishes a new session then.
However, if a malicious client sends too many requests of key However, if a malicious client sends too many requests of key
exchanges (req-KEX-C1 messages) only, resource starvation might exchanges (req-KEX-C1 messages) only, resource starvation might
occur. In such critical situations, servers MAY discard any kind of occur. In such critical situations, servers MAY discard any kind of
existing sessions regardless of these statuses. One way to mitigate existing sessions regardless of these statuses. One way to mitigate
such attacks are that servers MAY have a number and a time limits for such attacks are that servers MAY have a number and a time limits for
unverified pending key exchange requests (in the "wa received" unverified pending key exchange requests (in the "key exchanging"
status). status).
This is a common weakness of authentication protocols with almost any This is a common weakness of authentication protocols with almost any
kind of negotiations or states, including Digest authentication kind of negotiations or states, including Digest authentication
method and most Cookie-based authentication implementations. method and most Cookie-based authentication implementations.
However, regarding the resource consumption, a situation of the However, regarding the resource consumption, a situation of the
mutual authentication method is a slightly better than the Digest, mutual authentication method is a slightly better than the Digest,
because HTTP requests without any kind of authentication requests because HTTP requests without any kind of authentication requests
will not generate any kind of sessions. Session identifiers are only will not generate any kind of sessions. Session identifiers are only
generated after a client starts a key negotiation. It means that generated after a client starts a key negotiation. It means that
simple clients such as web crawlers will not accidentally consume simple clients such as web crawlers will not accidentally consume
server-side resources for session managements. server-side resources for session managements.
16.3. Implementation Considerations 16.2.1. On-line Active Password Attacks
Although the protocol provides very strong protection against off-
line dictionary attacks from eavesdropped traffics, the protocol, by
its nature, can not prevent an active password attacks which the
attackers sends so many authentication trial requests for every
possible passwords.
Possible countermeasures for preventing such attacks may be rate-
limiting of the password authentication trials, statistics-based
intrusion detection measures or similar protection schemes. If the
server operators assume that the passwords of users are not strong
enough, it may be desirable to introduce such ad-hoc countermeasures.
16.3. Communicating the status of mutual authentication with users
This protocol is designed for two goals. The first goal is just
providing a secure alternative for existing Basic and Digest
authentication. The second goal is to provide users a way to detect
forged rogue servers imitating user's registered account on server-
side, commonly known as (a part or kind of) Phishing attacks.
For this protocol to effectively work as some countermeasures to such
attacks, it is very important that end users of clients will be
notified of the result of mutual authentication performed by this
protocol, especially the three states "AUTH-SUCCEED",
"UNAUTHENTICATED" and "AUTH-REQUIRED" defined in Section 9. The
design of secure users' interfaces of the HTTP interactive clients
are out of the scope of this document, but if possible, having some
kind of UI indication for the three states above will be desirable
for user's benefits on their security.
Of course, in such cases, the user interfaces for asking passwords
for this authentication shall be clearly identifiable against
imitation by other insecure password input fields (such as forms).
If the passwords are known to malicious attackers outside of the
protocol, the protocol can not work as an effective security
measures.
16.4. Implementation Considerations
o To securely implement the protocol, the Authentication-Info o To securely implement the protocol, the Authentication-Info
headers in the 200-VFY-S messages MUST always be validated by the headers in the 200-VFY-S messages MUST always be validated by the
client. If the validation fails, the client MUST NOT process any client. If the validation fails, the client MUST NOT process any
content sent with the message, including other headers and the content sent with the message, including other headers and the
body part. Non-compliance to this requirement will allow phishing body part. Non-compliance to this requirement will allow phishing
attacks. attacks.
o The authentication status on the client-side SHOULD be visible to
the users of the client. In addition, the method for asking for
the user's name and passwords SHOULD be carefully designed so that
(1) the user can easily distinguish the request from this
authentication method from any other authentication methods such
as Basic and Digest methods, and (2) the Web contents cannot
imitate the user-interfaces for this protocol.
An informational memo regarding user-interface considerations and
recommendations for implementing this protocol will be separately
published.
o For HTTP/TLS communications, when a web form is submitted from o For HTTP/TLS communications, when a web form is submitted from
Mutually-authenticated pages with the "tls-cert" validation method Mutually-authenticated pages with the "tls-server-end-point"
to a URI that is protected by the same realm (so indicated by the validation method to a URI that is protected by the same realm (so
path parameter), if the server certificate has been changed since indicated by the path parameter), if the server certificate has
the pages were received, the peer is RECOMMENDED to be revalidated been changed since the pages were received, the peer is
using a req-KEX-C1 message with an "Expect: 100-continue" header. RECOMMENDED to be revalidated using a req-KEX-C1 message with an
The same applies when the page is received with the "tls-key" "Expect: 100-continue" header. The same applies when the page is
validation method, and when the TLS session has expired. received with the "tls-unique" validation method, and when the TLS
session has expired.
o Server-side storages of user passwords are advised to contain the o For better protection against possible password database steal,
Server-side storages of user passwords are better containing the
values encrypted by one-way function J(pi), instead of the real values encrypted by one-way function J(pi), instead of the real
passwords, those hashed by ph, or pi. passwords, those hashed by ph, or pi.
16.4. Usage Considerations 16.5. Usage Considerations
o The user-names inputted by a user may be sent automatically to any o The user-names inputted by a user may be sent automatically to any
servers sharing the same auth-domain. This means that when host- servers sharing the same auth-domain. This means that when host-
type auth-domain is used for authentication on an HTTPS site, and type auth-domain is used for authentication on an HTTPS site, and
when an HTTP server on the same host requests Mutual when an HTTP server on the same host requests Mutual
authentication within the same realm, the client will send the authentication within the same realm, the client will send the
user-name in a clear text. If user-names have to be kept secret user-name in a clear text. If user-names have to be kept secret
against eavesdropping, the server must use full-scheme-type auth- against eavesdropping, the server must use full-scheme-type auth-
domain parameter. Contrarily, passwords are not exposed to domain parameter and HTTPS. Contrarily, passwords are not exposed
eavesdroppers even on HTTP requests. to eavesdroppers even on HTTP requests.
o The "pwd-hash" parameter is only provided for backward o The "pwd-hash" parameter is only provided for backward
compatibility of password databases. The use of "none" function compatibility of password databases. The use of "none" function
is the most secure choice and is RECOMMENDED. If values other is the most secure choice and is RECOMMENDED. If values other
than "none" are used, you MUST ensure that the hash values of the than "none" are used, you MUST ensure that the hash values of the
passwords were not exposed to the public. Note that hashed passwords were not exposed to the public. Note that hashed
password databases for plain-text authentications are usually not password databases for plain-text authentications are usually not
considered secret. considered secret.
o If the server provides several ways for storing server-side o If the server provides several ways for storing server-side
password secrets into the password database, it is advised to password secrets into the password database, it is desirable for
store the values encrypted by using the one-way function J(pi), better security to store the values encrypted by using the one-way
instead of the real passwords, those hashed by ph, or pi. function J(pi), instead of the real passwords, those hashed by ph,
or pi.
17. Notice on Intellectual Properties 17. Notice on Intellectual Properties
The National Institute of Advanced Industrial Science and Technology The National Institute of Advanced Industrial Science and Technology
(AIST) and Yahoo! Japan, Inc. has jointly submitted a patent (AIST) and Yahoo! Japan, Inc. has jointly submitted a patent
application on the protocol proposed in this documentation to the application on the protocol proposed in this documentation to the
Patent Office of Japan. The patent is intended to be open to any Patent Office of Japan. The patent is intended to be open to any
implementors of this protocol and its variants under non-exclusive implementors of this protocol and its variants under non-exclusive
royalty-free manner. For the details of the patent application and royalty-free manner. For the details of the patent application and
its status, please contact the author of this document. its status, please contact the author of this document.
skipping to change at page 45, line 13 skipping to change at page 42, line 4
implementors of this protocol and its variants under non-exclusive implementors of this protocol and its variants under non-exclusive
royalty-free manner. For the details of the patent application and royalty-free manner. For the details of the patent application and
its status, please contact the author of this document. its status, please contact the author of this document.
The elliptic-curve based authentication algorithms might involve The elliptic-curve based authentication algorithms might involve
several existing third-party patents. The authors of the document several existing third-party patents. The authors of the document
take no position regarding the validity or scope of such patents, and take no position regarding the validity or scope of such patents, and
other patents as well. other patents as well.
18. References 18. References
18.1. Normative References 18.1. Normative References
[I-D.ietf-httpauth-extension] [I-D.ietf-httpauth-extension]
Oiwa, Y., Watanabe, H., Takagi, H., Kihara, B., Hayashi, Oiwa, Y., Watanabe, H., Takagi, H., Hayashi, T., and Y.
T., and Y. Ioku, "HTTP Authentication Extensions for Ioku, "HTTP Authentication Extensions for Interactive
Interactive Clients", draft-ietf-httpauth-extension-00 Clients", draft-ietf-httpauth-extension-01 (work in
(work in progress), July 2013. progress), October 2013.
[I-D.ietf-httpbis-p1-messaging] [I-D.ietf-httpbis-p1-messaging]
Fielding, R. and J. Reschke, "Hypertext Transfer Protocol Fielding, R. and J. Reschke, "Hypertext Transfer Protocol
(HTTP/1.1): Message Syntax and Routing", (HTTP/1.1): Message Syntax and Routing",
draft-ietf-httpbis-p1-messaging-22 (work in progress), draft-ietf-httpbis-p1-messaging-24 (work in progress),
February 2013. September 2013.
[I-D.ietf-httpbis-p7-auth] [I-D.ietf-httpbis-p7-auth]
Fielding, R. and J. Reschke, "Hypertext Transfer Protocol Fielding, R. and J. Reschke, "Hypertext Transfer Protocol
(HTTP/1.1): Authentication", draft-ietf-httpbis-p7-auth-22 (HTTP/1.1): Authentication", draft-ietf-httpbis-p7-auth-24
(work in progress), February 2013. (work in progress), September 2013.
[I-D.oiwa-precis-httpauthprep]
Oiwa, Y., NEMOTO, T., and B. Kihara, "HTTPAuthPrep: PRECIS
profile for HTTP Authentication",
draft-oiwa-precis-httpauthprep-00 (work in progress),
July 2013.
[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, March 1997. Requirement Levels", BCP 14, RFC 2119, March 1997.
[RFC3629] Yergeau, F., "UTF-8, a transformation format of ISO [RFC3629] Yergeau, F., "UTF-8, a transformation format of ISO
10646", STD 63, RFC 3629, November 2003. 10646", STD 63, RFC 3629, November 2003.
[RFC4013] Zeilenga, K., "SASLprep: Stringprep Profile for User Names [RFC4013] Zeilenga, K., "SASLprep: Stringprep Profile for User Names
and Passwords", RFC 4013, February 2005. and Passwords", RFC 4013, February 2005.
skipping to change at page 46, line 10 skipping to change at page 43, line 4
Specifications: ABNF", STD 68, RFC 5234, January 2008. Specifications: ABNF", STD 68, RFC 5234, January 2008.
[RFC5246] Dierks, T. and E. Rescorla, "The Transport Layer Security [RFC5246] Dierks, T. and E. Rescorla, "The Transport Layer Security
(TLS) Protocol Version 1.2", RFC 5246, August 2008. (TLS) Protocol Version 1.2", RFC 5246, August 2008.
18.2. Informative References 18.2. Informative References
[I-D.ietf-precis-framework] [I-D.ietf-precis-framework]
Saint-Andre, P. and M. Blanchet, "PRECIS Framework: Saint-Andre, P. and M. Blanchet, "PRECIS Framework:
Preparation and Comparison of Internationalized Strings in Preparation and Comparison of Internationalized Strings in
Application Protocols", draft-ietf-precis-framework-08 Application Protocols", draft-ietf-precis-framework-11
(work in progress), April 2013. (work in progress), October 2013.
[I-D.oiwa-httpauth-mutual-algo] [I-D.oiwa-httpauth-mutual-algo]
Oiwa, Y., Watanabe, H., Takagi, H., Kihara, B., Hayashi, Oiwa, Y., Watanabe, H., Takagi, H., Hayashi, T., and Y.
T., and Y. Ioku, "Mutual Authentication Protocol for HTTP: Ioku, "Mutual Authentication Protocol for HTTP: KAM3-based
KAM3-based Cryptographic Algorithms", Cryptographic Algorithms",
draft-oiwa-httpauth-mutual-algo-00 (work in progress), draft-oiwa-httpauth-mutual-algo-01 (work in progress),
Jul 2013. October 2013.
[ISO.10646-1.1993] [ISO.10646-1.1993]
International Organization for Standardization, International Organization for Standardization,
"Information Technology - Universal Multiple-octet coded "Information Technology - Universal Multiple-octet coded
Character Set (UCS) - Part 1: Architecture and Basic Character Set (UCS) - Part 1: Architecture and Basic
Multilingual Plane", ISO Standard 10646-1, May 1993. Multilingual Plane", ISO Standard 10646-1, May 1993.
[ITU.X690.1994] [ITU.X690.1994]
International Telecommunications Union, "Information International Telecommunications Union, "Information
Technology - ASN.1 encoding rules: Specification of Basic Technology - ASN.1 encoding rules: Specification of Basic
Encoding Rules (BER), Canonical Encoding Rules (CER) and Encoding Rules (BER), Canonical Encoding Rules (CER) and
Distinguished Encoding Rules (DER)", ITU-T Recommendation Distinguished Encoding Rules (DER)", ITU-T Recommendation
X.690, 1994. X.690, 1994.
[OASIS.saml-core-2.0-os] [RFC1939] Myers, J. and M. Rose, "Post Office Protocol - Version 3",
Cantor, S., Kemp, J., Philpott, R., and E. Maler, STD 53, RFC 1939, May 1996.
"Assertions and Protocol for the OASIS Security Assertion
Markup Language (SAML) V2.0", OASIS Standard saml-core-
2.0-os, March 2005.
[OIDF.Connect.Standard]
Sakimura, N., Bradley, J., Jones, M., de Medeiros, B.,
Mortimore, C., and E. Jay, "OpenID Connect Standard 1.0 -
draft 10", May 2012.
[RFC2617] Franks, J., Hallam-Baker, P., Hostetler, J., Lawrence, S., [RFC2617] Franks, J., Hallam-Baker, P., Hostetler, J., Lawrence, S.,
Leach, P., Luotonen, A., and L. Stewart, "HTTP Leach, P., Luotonen, A., and L. Stewart, "HTTP
Authentication: Basic and Digest Access Authentication", Authentication: Basic and Digest Access Authentication",
RFC 2617, June 1999. RFC 2617, June 1999.
[RFC2743] Linn, J., "Generic Security Service Application Program
Interface Version 2, Update 1", RFC 2743, January 2000.
[RFC2818] Rescorla, E., "HTTP Over TLS", RFC 2818, May 2000. [RFC2818] Rescorla, E., "HTTP Over TLS", RFC 2818, May 2000.
[RFC3961] Raeburn, K., "Encryption and Checksum Specifications for
Kerberos 5", RFC 3961, February 2005.
[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,
May 2008. May 2008.
[RFC5280] Cooper, D., Santesson, S., Farrell, S., Boeyen, S.,
Housley, R., and W. Polk, "Internet X.509 Public Key
Infrastructure Certificate and Certificate Revocation List
(CRL) Profile", RFC 5280, May 2008.
[RFC5890] Klensin, J., "Internationalized Domain Names for [RFC5890] Klensin, J., "Internationalized Domain Names for
Applications (IDNA): Definitions and Document Framework", Applications (IDNA): Definitions and Document Framework",
RFC 5890, August 2010. RFC 5890, August 2010.
[RFC5929] Altman, J., Williams, N., and L. Zhu, "Channel Bindings [RFC5929] Altman, J., Williams, N., and L. Zhu, "Channel Bindings
for TLS", RFC 5929, July 2010. for TLS", RFC 5929, July 2010.
[RFC6265] Barth, A., "HTTP State Management Mechanism", RFC 6265, [RFC6265] Barth, A., "HTTP State Management Mechanism", RFC 6265,
April 2011. April 2011.
[RFC6749] Hardt, D., "The OAuth 2.0 Authorization Framework",
RFC 6749, October 2012.
Appendix A. (Informative) Draft Remarks from Authors Appendix A. (Informative) Draft Remarks from Authors
The following items are currently under consideration for future The following items are currently under consideration for future
revisions by the authors. revisions by the authors.
o Whether to keep TLS-key validation or not. o Whether to keep TLS-unique validation or not.
o When keeping tls-key validation, whether to use "TLS channel o Whether to introduce PBKDF2 or similar password strengthening
binding" [RFC5929] for "tls-key" verification (Section 7). Note hashes into the function pi().
that existing TLS implementations should be considered to
determine this.
o Adopt [I-D.ietf-precis-framework] for replacing SASLprep o Whether to keep ph() function for legacy migration or not.
reference. Especially, use NFC canonicalization instead of NFKC.
o Adding test vectors for ensuring implementation correctness. o Adding test vectors for ensuring implementation correctness.
o Possibly adding a method for servers to detect availability of o Possibly adding a method for servers to detect availability of
Mutual authentication on client-side. Mutual authentication on client-side.
o Possible support for optional key renewal and cross-site federated
authentication.
Appendix B. (Informative) Draft Change Log Appendix B. (Informative) Draft Change Log
B.1. Changes in Httpauth Revision 00 B.1. Changes in Httpauth WG Revision 01
o Changed "tls-key" verification to "tls-unique" verification, and
"tls-cert" to "tls-server-end-point", adopting RFC 5929.
o Adopted [I-D.ietf-precis-framework].
o Reverted reservation of "rekey-sid" and "rekey-method" parameters.
o Degraded secure UI requirement to application note level, non-
normative.
o Adjusted levels of several requirements.
o Added warning text for handling of exceptional 5XX responses.
o Dropped several references for optional authentications, except
one "Note".
o Several textual fixes, improvements and revisions.
B.2. Changes in Httpauth Revision 00
o Changed the version token. o Changed the version token.
o Renamed "verification tokens" to "Host verification tokens" and o Renamed "verification tokens" to "Host verification tokens" and
variables "v" to "vh" for clarification. (Back-ported from variables "v" to "vh" for clarification. (Back-ported from
draft-oiwa-httpauth-multihop-template-00) draft-oiwa-httpauth-multihop-template-00)
B.2. Changes in HttpBis Revision 00 B.3. Changes in HttpBis Revision 00
None. None.
B.3. Changes in Revision 12 B.4. Changes in Revision 12
o Added a reason "authz-failed". o Added a reason "authz-failed".
B.4. Changes in Revision 11 B.5. Changes in Revision 11
o Message syntax definition reverted to pre-07 style as httpbis-p1 o Message syntax definition reverted to pre-07 style as httpbis-p1
and p7 now defines a precise rule for parameter value parsing. and p7 now defines a precise rule for parameter value parsing.
o Replaced "stale" parameter with more infomative/extensive "reason" o Replaced "stale" parameter with more infomative/extensive "reason"
parameter in 401-INIT and 401-STALE. parameter in 401-INIT and 401-STALE.
o Reserved "rekey-sid" and "rekey-method" parameters for future o Reserved "rekey-sid" and "rekey-method" parameters for future
extensions. extensions.
o Added descriptions for replacing/non-replacing existing o Added descriptions for replacing/non-replacing existing
technologies. technologies.
B.5. Changes in Revision 10 B.6. Changes in Revision 10
o The authentication extension parts (non-mandatory authentication o The authentication extension parts (non-mandatory authentication
and authentication controls) are separated to yet another draft. and authentication controls) are separated to yet another draft.
o The default auth-domain parameter is changed to the full scheme- o The default auth-domain parameter is changed to the full scheme-
host-port syntax, which is consistent with usual HTTP host-port syntax, which is consistent with usual HTTP
authentication framework behavior. authentication framework behavior.
o Provision for application channel binding is added. o Provision for application channel binding is added.
skipping to change at page 49, line 28 skipping to change at page 46, line 18
+------------+----------+-------------------------------------------+ +------------+----------+-------------------------------------------+
| S_c1, S_s1 | s_a, s_b | client/server-side secret randoms | | S_c1, S_s1 | s_a, s_b | client/server-side secret randoms |
| K_c1, K_s1 | w_a, w_b | client/server-side exchanged key | | K_c1, K_s1 | w_a, w_b | client/server-side exchanged key |
| | | components | | | | components |
| kc1, ks1 | wa, wb | parameter names for those | | kc1, ks1 | wa, wb | parameter names for those |
| VK_c, VK_s | o_a, o_b | client/server-side key verifiers | | VK_c, VK_s | o_a, o_b | client/server-side key verifiers |
| vkc, vks | oa, ob | parameter names for those | | vkc, vks | oa, ob | parameter names for those |
| z | z | session secrets | | z | z | session secrets |
+------------+----------+-------------------------------------------+ +------------+----------+-------------------------------------------+
B.6. Changes in Revision 09 B.7. Changes in Revision 09
o The (default) cryptographic algorithms are separated to another o The (default) cryptographic algorithms are separated to another
draft. draft.
o Names of the messages are changed to more informative ones than o Names of the messages are changed to more informative ones than
before. The following is the correspondence table of those names: before. The following is the correspondence table of those names:
+-------------------+-----------------+-----------------------------+ +-------------------+-----------------+-----------------------------+
| new name | old name | description | | new name | old name | description |
+-------------------+-----------------+-----------------------------+ +-------------------+-----------------+-----------------------------+
skipping to change at page 50, line 5 skipping to change at page 46, line 41
| req-KEX-C1 | req-A1 | client->server key exchange | | req-KEX-C1 | req-A1 | client->server key exchange |
| 401-KEX-S1 | 401-B1 | server->client key exchange | | 401-KEX-S1 | 401-B1 | server->client key exchange |
| req-VFY-C | req-A3 | client->server auth. | | req-VFY-C | req-A3 | client->server auth. |
| | | verification | | | | verification |
| 200-VFY-S | 200-B4 | server->client auth. | | 200-VFY-S | 200-B4 | server->client auth. |
| | | verification | | | | verification |
| 200-Optional-INIT | 200-Optional-B0 | initial with non-mandatory | | 200-Optional-INIT | 200-Optional-B0 | initial with non-mandatory |
| | | authentication | | | | authentication |
+-------------------+-----------------+-----------------------------+ +-------------------+-----------------+-----------------------------+
B.7. Changes in Revision 08 B.8. Changes in Revision 08
o The English text has been revised. o The English text has been revised.
B.8. Changes in Revision 07 B.9. Changes in Revision 07
o Adapt to httpbis HTTP/1.1 drafts: o Adapt to httpbis HTTP/1.1 drafts:
* Changed definition of extensive-token. * Changed definition of extensive-token.
* LWSP continuation-line (%0D.0A.20) deprecated. * LWSP continuation-line (%0D.0A.20) deprecated.
o To simplify the whole spec, the type of nonce-counter related o To simplify the whole spec, the type of nonce-counter related
parameters are change from hex-integer to integer. parameters are change from hex-integer to integer.
o Algorithm tokens are renamed to include names of hash algorithms. o Algorithm tokens are renamed to include names of hash algorithms.
o Clarified the session management, added details of server-side o Clarified the session management, added details of server-side
protocol decisions. protocol decisions.
o The whole draft was reorganized; introduction and overview has o The whole draft was reorganized; introduction and overview has
been rewritten. been rewritten.
B.9. Changes in Revision 06 B.10. Changes in Revision 06
o Integrated Optional Mutual Authentication to the main part. o Integrated Optional Mutual Authentication to the main part.
o Clarified the decision procedure for message recognitions. o Clarified the decision procedure for message recognitions.
o Clarified that a new authentication request for any sub-requests o Clarified that a new authentication request for any sub-requests
in interactive clients may be silently discarded. in interactive clients may be silently discarded.
o Typos and confusing phrases are fixed. o Typos and confusing phrases are fixed.
o Several "future considerations" are added. o Several "future considerations" are added.
B.10. Changes in Revision 05 B.11. Changes in Revision 05
o A new parameter called "version" is added for supporting future o A new parameter called "version" is added for supporting future
incompatible changes with a single implementation. In the (first) incompatible changes with a single implementation. In the (first)
final specification its value will be changed to 1. final specification its value will be changed to 1.
o A new header "Authentication-Control" is added for precise control o A new header "Authentication-Control" is added for precise control
of application-level authentication behavior. of application-level authentication behavior.
B.11. Changes in Revision 04 B.12. Changes in Revision 04
o Changed text of patent licenses: the phrase "once the protocol is o Changed text of patent licenses: the phrase "once the protocol is
accepted as an Internet standard" is removed so that the sentence accepted as an Internet standard" is removed so that the sentence
also covers the draft versions of this protocol. also covers the draft versions of this protocol.
o The "tls-key" verification is now OPTIONAL. o The "tls-key" verification is now OPTIONAL.
o Several description fixes and clarifications. o Several description fixes and clarifications.
B.12. Changes in Revision 03 B.13. Changes in Revision 03
o Wildcard domain specifications (e.g. "*.example.com") are allowed o Wildcard domain specifications (e.g. "*.example.com") are allowed
for auth-domain parameters (Section 4.1). for auth-domain parameters (Section 4.1).
o Specification of the "tls-cert" verification is updated o Specification of the tls-cert verification is updated
(incompatible change). (incompatible change).
o State transitions fixed. o State transitions fixed.
o Requirements for servers concerning w_a values are clarified. o Requirements for servers concerning w_a values are clarified.
o RFC references are updated. o RFC references are updated.
B.13. Changes in Revision 02 B.14. Changes in Revision 02
o Auth-realm is extended to allow full-scheme type. o Auth-realm is extended to allow full-scheme type.
o A decision diagram for clients and decision procedures for servers o A decision diagram for clients and decision procedures for servers
are added. are added.
o 401-B1 and req-A3 messages are changed to contain authentication o 401-B1 and req-A3 messages are changed to contain authentication
realm information. realm information.
o Bugs on equations for o_A and o_B are fixed. o Bugs on equations for o_A and o_B are fixed.
o Detailed equations for the entire algorithm are included. o Detailed equations for the entire algorithm are included.
o Elliptic-curve algorithms are updated. o Elliptic-curve algorithms are updated.
o Several clarifications and other minor updates. o Several clarifications and other minor updates.
B.14. Changes in Revision 01 B.15. Changes in Revision 01
o Several texts are rewritten for clarification. o Several texts are rewritten for clarification.
o Added several security consideration clauses. o Added several security consideration clauses.
Authors' Addresses Authors' Addresses
Yutaka Oiwa Yutaka Oiwa
National Institute of Advanced Industrial Science and Technology National Institute of Advanced Industrial Science and Technology
Research Institute for Secure Systems Research Institute for Secure Systems
skipping to change at page 52, line 32 skipping to change at page 49, line 32
JP JP
Hiromitsu Takagi Hiromitsu Takagi
National Institute of Advanced Industrial Science and Technology National Institute of Advanced Industrial Science and Technology
Research Institute for Secure Systems Research Institute for Secure Systems
Tsukuba Central 2 Tsukuba Central 2
1-1-1 Umezono 1-1-1 Umezono
Tsukuba-shi, Ibaraki Tsukuba-shi, Ibaraki
JP JP
Boku Kihara
Lepidum Co. Ltd.
#602, Village Sasazuka 3
1-30-3 Sasazuka
Shibuya-ku, Tokyo
JP
Tatsuya Hayashi Tatsuya Hayashi
Lepidum Co. Ltd. Lepidum Co. Ltd.
#602, Village Sasazuka 3 #602, Village Sasazuka 3
1-30-3 Sasazuka 1-30-3 Sasazuka
Shibuya-ku, Tokyo Shibuya-ku, Tokyo
JP JP
Yuichi Ioku Yuichi Ioku
Yahoo! Japan, Inc. Individual
Midtown Tower
9-7-1 Akasaka
Minato-ku, Tokyo
JP
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