Virtual World Region Agent Protocol : Client Application Launch Message
draft-hamrick-vwrap-launch-00

Abstract

This document describes the LLIDL interface description for the Virtual World Region Agent Protocol (VWRAP) Client Application Launch message format. Messages in this format are intended to be used in conjunction with standard web authentication or authorization technologies such as OpenID or OAuth. This document describes the message format, the processing expectations and three MIME types that may be used to identify requests to initiate a virtual worlds session.

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Table of Contents

1.  Introduction
    1.1.  Requirements Language
2.  The VWRAP Client Application Launch Message Format
3.  Message Flow
4.  Processing Expectations
5.  IANA Considerations
6.  MIME Type Registrations
    6.1.  MIME Type Registration for application/calm+xml
    6.2.  MIME Type Registration for application/calm+json
    6.3.  MIME Type Registration for application/calm+binary
7.  Security Considerations
8.  References
    8.1.  Normative References
    8.2.  Informative References
§  Authors' Addresses

1.  Introduction

Web authentication protocols such as OpenID (OpenID Foundation, “OpenID Authentication 2.0 - Final,” 2007.) [OPENID] and web authorization protocols such as OAuth (Hammer-Lahav, E. and B. Cook, “The OAuth Core Protocol,” March 2009.) [I‑D.hammer‑oauth] are of increasing interest to the internet community. They have great utility in web-based application environments. Best practice for their use in conjunction with applications that do not expose a HTML rendering interface is less clear. Virtual World (VW) client applications, for instance, are often implemented as "desktop applications" instead of "web apps". This introduces difficulty in using web based authentication and authorization protocols to initiate a virtual world session.

OpenID and OAuth traditionally use a HTTP redirect [RFC2616] (Fielding, R., Gettys, J., Mogul, J., Frystyk, H., Masinter, L., Leach, P., and T. Berners-Lee, “Hypertext Transfer Protocol -- HTTP/1.1,” June 1999.) after user or token authentication to begin an authorized session with a web application. The problem in using desktop applications with "web auth" technologies is that desktop applications do not generally have a URL to act as the target of HTTP redirection.

One possible solution to this problem is to register a unique MIME type [RFC2046] (Freed, N. and N. Borenstein, “Multipurpose Internet Mail Extensions (MIME) Part Two: Media Types,” November 1996.) with the user's web browser and following successful user or token authentication, redirect the user's web browser to a resource with that MIME type. Upon receipt of such a resource, a properly configured web browser could then launch the client desktop application.

This document describes the format of a web resource suitable for signaling the user's web browser to launch a virtual world client application that uses Virtual World Region Agent Protocol (VWRAP) Authentication [I‑D.hamrick‑vwrap‑authentication] (Chu, T., Hamrick, M., and M. Lentczner, “VWRAP Trust Model and User Authentication,” February 2010.) to establish a session between the client application and network resources implementing the virtual world.

1.1.  Requirements Language

The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this document are to be interpreted as described in RFC 2119 (Bradner, S., “Key words for use in RFCs to Indicate Requirement Levels,” March 1997.) [RFC2119].

2.  The VWRAP Client Application Launch Message Format

The Client Application Launch message is an LLSD [I‑D.hamrick‑vwrap‑type‑system] (Brashears, A., Hamrick, M., and M. Lentczner, “VWRAP : Abstract Type System for the Transmission of Dynamic Structured Data,” February 2010.) message, defined by the LLIDL below, but is identified with a unique MIME type (described below.) It may be transmitted in XML, JSON or Binary format, at the web server's convenience. Compliant client applications SHOULD support XML, JSON and Binary serialization formats.

; note that the &request defined here uses named types &authenticator
; and &identifier which are defined in
; draft-hamrick-vwrap-authentication-00

&request = {
  authenticator : &authenticator,
  identifier : &identifier,
  loginurl : uri,
  region : uri
}

%% launch_request << &request

Figure 1 : VWRAP Client Application Launch Message

3.  Message Flow

The VWRAP Client Application Launch Message is intended to be sent by a web server to a web browser following successful authentication. Requirements for web authentication are explicitly not defined in this document, and left as a responsibility of the authenticating web service.

Two techniques for processing a client application launch message are defined. The first requests a one time "single use only" secret from an agent domain. This secret is used to authenticate the client to the agent domain. The second technique uses possession of a web capability to authenticate the client. The message flow for both techniques is the same.

Figure 2 below shows message flows between four conceptual entities. It is provided for expository purposes only; implementers may choose to combine conceptual entities into fewer reified components. That is, nothing in this specification should be interpreted to require four distinct, deployed entities.

+------------------+        2.       +------------------+
|                  |---------------->|                  |
| Web Auth Service |        3.       | VWRAP Agent Domain |
|                  |<----------------|                  |
+------------------+                 +------------------+
       ^     |                              ^
    1. |     | 4.                           | 6.
       |     v                              |
+------------------+        5.       +------------------+
|                  |---------------->|                  |
|    Web Browser   |                 |  VWRAP Client App  |
|                  |                 |                  |
+------------------+                 +------------------+

Figure 2 : Message Flow For Client Application Launch Requests

0. Registering MIME types as Web Browser Helper Applications

The technique defined in this document depends on the traditional web browser capability to define a "helper application" when the browser receives a MIME type it cannot handle itself. Compliant VWRAP Client Applications SHOULD register themselves as the helper application for the three MIME types listed in IANA Considerations (IANA Considerations) below.
The exact technique used to register the client application with the VWRAP Client Application Launch Message is beyond the scope of this document.

1. Web Client to Web Server Authentication / Authorization

The process of launching an VWRAP client application using a web based authentication or authorization system begins with successful user authentication or token authentication. It is traditional in these systems for the user's web browser to be redirected to a web based application following authentication. This document assumes the user's web browser will instead be redirected to an HTTP or HTTPS URI that will eventually respond with a Client Application Launch Message.
The exact nature of the web-based authentication or authorization scheme used is beyond the scope of this document.

2. One Time Password or LoginURL Capability Request

Before the web service responsible for communicating the launch message to the user's web browser may download the message, it must first request a "single use only" shared secret or the LoginURL web capability.
The exact mechanism for this request is beyond the scope of this document. However, the request from the authentication service to the agent domain SHOULD contain an account or avatar name known to the agent domain and SHOULD be communicated over a secure channel.

3. One Time Password or LoginURL Capability Response

The agent domain responds with a One Time Password or web capability. If the one time password is used, the password SHOULD be a sequence of unguessable octets, thought the exact encoding and transport of the request is beyond the scope of this document.

4. Client Application Launch Download

After the One Time Password or web capability is passed from the agent domain to the authorization service, it is included in the Client Application Launch Message along with an account or avatar identifier, a login URI for the agent domain and an initial region URI indicating the avatar's initial location in the virtual world.

5. Web Browser Launches Client Application

When the user's web browser receives the Client Application Launch Message, it forwards the contents of the message AND the message's MIME type to the registered Client Application.

6. VWRAP Authentication

In response to receipt of the Client Application Launch Message, the client application uses the information in the message to begin the VWRAP Authentication process and initial placement of the user's avatar in the virtual world.

4.  Processing Expectations

When a client application receives a client application launch message, it is expected to request a seed capability from the service endpoint from in the loginurl specified in message. The loginurl is expected to identify the service endpoint for an agent_login resource defined in the VWRAP Trust Model and User Authentication (Chu, T., Hamrick, M., and M. Lentczner, “VWRAP Trust Model and User Authentication,” February 2010.) [I‑D.hamrick‑vwrap‑authentication] specification. The client SHOULD pass the &authenticator and &identifier map entries to the agent_login resource unaltered.

5.  IANA Considerations

In accordance with [RFC5226] (Narten, T. and H. Alvestrand, “Guidelines for Writing an IANA Considerations Section in RFCs,” May 2008.), this document registers the following mime types:

application/calm+xml

application/calm+json

application/calm+binary

See the MIME Type Registrations section (MIME Type Registrations) below for detailed information on MIME Type registrations.

6.  MIME Type Registrations

This section provides media-type registration applications (as per RFC 4288 (Freed, N. and J. Klensin, “Media Type Specifications and Registration Procedures,” December 2005.) [RFC4288].)

6.1.  MIME Type Registration for application/calm+xml

To: ietf-types@iana.org

Subject: Registration of media type application/calm+xml

Type name: application

Subtype name: calm+xml

Required Parameters: none

Optional Parameters: none

Encoding Considerations:

The Extensible Markup Language (XML) specification allows for the use of multiple character sets. The character set used to encode the body of the message is defined as part of the XML header. If no character set is indicated in the XML header, compliant systems MUST assume UTF-8. When encoding binary data using RFC 4648 (Josefsson, S., “The Base16, Base32, and Base64 Data Encodings,” October 2006.) [RFC4648], characters outside the base alphabet are explicitly allowable and should be ignored.

Security Considerations:

The VWRAP Client Application Launch Request Message contains sensitive information. Compliant systems SHOULD ensure the confidentiality of the communications media between the web authentication service and the VWRAP agent domain as well as that between the web authentication service and the user's web browser.

Interoperability Considerations:

While it is possible for compliant implementations to specify the use of character sets other than UTF-8, such systems MUST accept UTF-8 input and SHOULD generate UTF-8 output.

Published specification: this specification.

Applications that use this media type:

Virtual world, tele-presence and content management systems related to "virtual reality" systems.

Additional Information:

Magic Number(s): none

File Extension: calmx

Macintosh File Type Code(s): CALX

Person & email address to contact for further information:

Meadhbh Hamrick <infinity@lindenlab.com>

Intended Usage: COMMON

Author: IESG

Change Controller: IESG

6.2.  MIME Type Registration for application/calm+json

To: ietf-types@iana.org

Subject: Registration of media type application/calm+json

Type name: application

Subtype name: calm+json

Required Parameters: none

Optional Parameters: none

Encoding Considerations: Use of Unicode is Mandatory

ECMA-262 (ECMA International, “Standard ECMA-262, 5th Edition : ECMAScript Language Specification,” December 2009.) [ECMA262r5] requires the use of Unicode, but allows the use of UTF-8, UTF-16 or UTF-32 character encodings.

Security Considerations:

The VWRAP Client Application Launch Request Message contains sensitive information. Compliant systems SHOULD ensure the confidentiality of the communications media between the web authentication service and the VWRAP agent domain as well as that between the web authentication service and the user's web browser.

Interoperability Considerations:

none

Published specification: This specification.

Applications that use this media type:

Virtual world, tele-presence and content management systems related to "virtual reality" systems.

Additional Information:

Magic Number(s): none

File Extension: calmj

Macintosh File Type Code(s): CALJ

Person & email address to contact for further information:

Meadhbh Hamrick <infinity@lindenlab.com>

Intended Usage: COMMON

Author: IESG

Change Controller: IESG

6.3.  MIME Type Registration for application/calm+binary

To: ietf-types@iana.org

Subject: Registration of media type application/calm+binary

Type name: application

Subtype name: calm+binary

Required Parameters: none

Optional Parameters: none

Encoding Considerations: LLSD Binary Serialization REQUIRES the use of binary content-transfer-encoding

Section 5 of RFC 2045 (Freed, N. and N. Borenstein, “Multipurpose Internet Mail Extensions (MIME) Part One: Format of Internet Message Bodies,” November 1996.) [RFC2045] describes the binary Content-Transfer-Encoding header field. This specification REQUIRES the use of this header to alert intermediary systems that information being included in the message should be interpreted as binary data with no end-of-line semantics which could be considerably longer than allowed in an RFC 821 transport.

Security Considerations:

The VWRAP Client Application Launch Request Message contains sensitive information. Compliant systems SHOULD ensure the confidentiality of the communications media between the web authentication service and the VWRAP agent domain as well as that between the web authentication service and the user's web browser.

Interoperability Considerations: none

Published specification: This specification.

Applications that use this media type:

Virtual world, tele-presence and content management systems related to "virtual reality" systems.

Additional Information:

Magic Number(s): none

File Extension: calb

Macintosh File Type Code(s): CALB

Person & email address to contact for further information:

Meadhbh Hamrick <infinity@lindenlab.com>

Intended Usage: COMMON

Author: IESG

Change Controller: IESG

7.  Security Considerations

Security considerations for this specification are, fortunately, either simple or beyond the scope of this document. RFC 3552 (Rescorla, E. and B. Korver, “Guidelines for Writing RFC Text on Security Considerations,” July 2003.) [RFC3552] describes several aspects to use when evaluating the security of a specification or implementation. The authors believe most common security concerns users of this specification will encounter are more appropriately considered as transport, network or link layer issues. Or, as higher level "application security" issues.

8.  References

8.1. Normative References

8.2. Informative References

Authors' Addresses