Internet DRAFT - draft-nottingham-http-over-version
draft-nottingham-http-over-version
Network Working Group M. Nottingham
Internet-Draft
Intended status: Informational June 20, 2014
Expires: December 22, 2014
The Over-Version HTTP Response Header Field
draft-nottingham-http-over-version-00
Abstract
The 505 (HTTP Version Not Supported) status code does not clearly
indicate, on its own, the scope of the assertion, nor the version(s)
supported. This document introduces a new header field, "Over-
Version", to indicate this information.
Status of This Memo
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
1.1. Use Case: TLS Client Authentication . . . . . . . . . . . 2
1.2. Notational Conventions . . . . . . . . . . . . . . . . . 3
2. The Over-Version HTTP Header Field . . . . . . . . . . . . . 3
2.1. Over-Version Scopes . . . . . . . . . . . . . . . . . . . 3
3. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 4
4. Security Considerations . . . . . . . . . . . . . . . . . . . 4
5. References . . . . . . . . . . . . . . . . . . . . . . . . . 4
5.1. Normative References . . . . . . . . . . . . . . . . . . 4
5.2. Informative References . . . . . . . . . . . . . . . . . 5
Author's Address . . . . . . . . . . . . . . . . . . . . . . . . 5
1. Introduction
The semantics of the 505 (Version Not Supported) status code are
defined by [RFC7231] as:
The 505 (HTTP Version Not Supported) status code indicates that the
server does not support, or refuses to support, the major version of
HTTP that was used in the request message. The server is indicating
that it is unable or unwilling to complete the request using the same
major version as the client, as described in Section 2.6 of
[RFC7230], other than with this error message. The server should
generate a representation for the 505 response that describes why
that version is not supported and what other protocols are supported
by that server.
This document defines a new HTTP response header, "Over-Version", to
be used in 505 responses to specify the protocol version(s) that can
be used, what resource(s) that assertion applies to, and how long it
is valid for (leveraging Cache-Control).
1.1. Use Case: TLS Client Authentication
While Over-Version might have a variety of applications, the primary
use case for them is the signaling that a resource (or set of
resources) requires TLS Client Authentication in HTTP/2
[I-D.ietf-httpbis-http2]. Since TLS renegotiation has been forbidden
in that protocol, a means of signaling that a particular request
should be made on a HTTP/1.1 connection is needed, so that a client
can use that protocol, allowing the server to perform renegotiation
to initiate client authentication.
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1.2. Notational Conventions
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
document are to be interpreted as described in [RFC2119].
Furthermore, this document uses the Augmented BNF defined in
[RFC5234], along with the #rule list extension defined in [RFC7230],
Section 7.
2. The Over-Version HTTP Header Field
The Over-Version HTTP Header field, when occurring in 505 (Version
Not Supported) responses, asserts the version or versions of HTTP
that are supported, and what resource(s) the assertion applies to,
and optionally how long it lasts.
Over-Version = 1*( OWS ";" OWS parameter )
This document specifies the following over-version parameters:
o "scope" - one of "origin", "resource" or "prefix" (see below)
o "version-id" - a space-separated list of ALPN protocol identifiers
[I-D.ietf-tls-applayerprotoneg].
Additionally, when Over-Version is in use, it indicates that the
Cache-Control header conveys a cache policy that is applicable to
this information (as well as the response itself).
For example:
HTTP/1.1 505 Version Not Supported
Over-Version: scope="prefix", version-id="h2"
Cache-Control: max=age=60
This response indicates that the requested resource and its children
cannot be reached over the current protocol version, and that for the
next 60 seconds, the client can successfully request them using the
"h2" protocol (in this case, HTTP/2).
2.1. Over-Version Scopes
This document defines the following values for the "scope" parameter;
o "origin" - indicates that the over-version applies to all
resources on the origin of the request
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o "resource" - indicates that the over-version applies to the
requested resource only (i.e., matching origin, path, and query)
o "prefix" - indicates that the over-version applies to resources
when the origin matches and the requested resource's path segments
are a prefix. For example, if the requested resource's path is
"/foo" then "/foo", "/foo?bar", "/foo/bar", "/foo/bar/baz" would
share the over-version, while "/bar", "/foobar" and "/bar/foo"
would not.
3. IANA Considerations
This document registers a new HTTP header field, "Over-Version", into
the Permanent Message Header Field Name Registry.
o Header Field Name: Over-Version
o Protocol: HTTP
o Status: standard
o Reference: [this document]
4. Security Considerations
Over-Version can be used to effect a downgrade attack by a man-in-
the-middle. When received over an insecure channel, it SHOULD be
ignored.
Over-Version can also be used to effect a downgrade attack by a party
that has the ability to inject response headers on the same origin.
The "origin" scope in particular is able to be misused, and SHOULD be
ignored unless the security properties of the new protocol are equal
to or better than the existing one.
5. References
5.1. Normative References
[I-D.ietf-tls-applayerprotoneg]
Friedl, S., Popov, A., Langley, A., and S. Emile,
"Transport Layer Security (TLS) Application Layer Protocol
Negotiation Extension", draft-ietf-tls-applayerprotoneg-05
(work in progress), March 2014.
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.
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[RFC5234] Crocker, D. and P. Overell, "Augmented BNF for Syntax
Specifications: ABNF", STD 68, RFC 5234, January 2008.
[RFC7230] Fielding, R. and J. Reschke, "Hypertext Transfer Protocol
(HTTP/1.1): Message Syntax and Routing", RFC 7230, June
2014.
[RFC7231] Fielding, R. and J. Reschke, "Hypertext Transfer Protocol
(HTTP/1.1): Semantics and Content", RFC 7231, June 2014.
5.2. Informative References
[I-D.ietf-httpbis-http2]
Belshe, M., Peon, R., and M. Thomson, "Hypertext Transfer
Protocol version 2", draft-ietf-httpbis-http2-13 (work in
progress), June 2014.
Author's Address
Mark Nottingham
Email: mnot@mnot.net
URI: http://www.mnot.net/
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