Forwarded HTTP Extension
RFC 7239
Internet Engineering Task Force (IETF) A. Petersson
Request for Comments: 7239 M. Nilsson
Category: Standards Track Opera Software
ISSN: 2070-1721 June 2014
Forwarded HTTP Extension
Abstract
This document defines an HTTP extension header field that allows
proxy components to disclose information lost in the proxying
process, for example, the originating IP address of a request or IP
address of the proxy on the user-agent-facing interface. In a path
of proxying components, this makes it possible to arrange it so that
each subsequent component will have access to, for example, all IP
addresses used in the chain of proxied HTTP requests.
This document also specifies guidelines for a proxy administrator to
anonymize the origin of a request.
Status of This Memo
This is an Internet Standards Track document.
This document is a product of the Internet Engineering Task Force
(IETF). It represents the consensus of the IETF community. It has
received public review and has been approved for publication by the
Internet Engineering Steering Group (IESG). Further information on
Internet Standards is available in Section 2 of RFC 5741.
Information about the current status of this document, any errata,
and how to provide feedback on it may be obtained at
http://www.rfc-editor.org/info/rfc7239.
Petersson & Nilsson Standards Track [Page 1]
RFC 7239 Forwarded HTTP Extension June 2014
Copyright Notice
Copyright (c) 2014 IETF Trust and the persons identified as the
document authors. All rights reserved.
This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents
(http://trustee.ietf.org/license-info) in effect on the date of
publication of this document. Please review these documents
carefully, as they describe your rights and restrictions with respect
to this document. Code Components extracted from this document must
include Simplified BSD License text as described in Section 4.e of
the Trust Legal Provisions and are provided without warranty as
described in the Simplified BSD License.
Table of Contents
1. Introduction ....................................................3
2. Notational Conventions ..........................................4
3. Syntax Notations ................................................4
4. Forwarded HTTP Header Field .....................................4
5. Parameters ......................................................6
5.1. Forwarded By ...............................................6
5.2. Forwarded For ..............................................6
5.3. Forwarded Host .............................................7
5.4. Forwarded Proto ............................................7
5.5. Extensions .................................................7
6. Node Identifiers ................................................8
6.1. IPv4 and IPv6 Identifiers ..................................9
6.2. The "unknown" Identifier ...................................9
6.3. Obfuscated Identifier ......................................9
7. Implementation Considerations ..................................10
7.1. HTTP Lists ................................................10
7.2. Header Field Preservation .................................10
7.3. Relation to Via ...........................................10
7.4. Transition ................................................11
7.5. Example Usage .............................................11
8. Security Considerations ........................................12
8.1. Header Validity and Integrity .............................12
8.2. Information Leak ..........................................12
8.3. Privacy Considerations ....................................12
9. IANA Considerations ............................................14
10. References ....................................................14
10.1. Normative References .....................................14
10.2. Informative References ...................................15
Appendix A. Acknowledgments .......................................16
Petersson & Nilsson Standards Track [Page 2]
RFC 7239 Forwarded HTTP Extension June 2014
1. Introduction
In today's HTTP landscape, there are a multitude of different
applications that act as proxies for the user agents. In many cases,
these proxies exists without the action or knowledge of the end-user.
These cases occur, for example, when the proxy exists as a part of
the infrastructure within the organization running the web server.
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