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Network Working Group                                        R. Van Rein
Internet-Draft                                          InternetWide.org
Intended status: Standards Track                        January 24, 2020
Expires: July 27, 2020

                     User Names for HTTP Resources


   Most protocols support users under domain names, but HTTP does not.
   Usage patterns in the wild do suggest a desire to have this facility.
   This specification defines a header for user names, orthogonal to any
   authentication or authorisation concerns.

Status of This Memo

   This Internet-Draft is submitted in full conformance with the
   provisions of BCP 78 and BCP 79.

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   This Internet-Draft will expire on July 27, 2020.

Copyright Notice

   Copyright (c) 2020 IETF Trust and the persons identified as the
   document authors.  All rights reserved.

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Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   2
   2.  The HTTP User Header  . . . . . . . . . . . . . . . . . . . .   3
   3.  Protocol Handling of HTTP User  . . . . . . . . . . . . . . .   3
   4.  Caching Behaviour . . . . . . . . . . . . . . . . . . . . . .   3
   5.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .   4
   6.  Security Considerations . . . . . . . . . . . . . . . . . . .   4
   7.  Normative References  . . . . . . . . . . . . . . . . . . . .   4
   Appendix A.  HTTP User Environment Variable . . . . . . . . . . .   4
   Author's Address  . . . . . . . . . . . . . . . . . . . . . . . .   5

1.  Introduction

   Most protocols support Network Access Identifiers [RFC7542] like
   john@example.com to identify users like john under domains such as
   example.com.  The URI format for HTTP can express [Section 2.7.1 of
   [RFC7230]] such authority sections, and many online applications seem
   to want to address individual users, but HTTP URIs do not usually
   express user names.  This specification therefore introduces a header
   "User", in close parallel to the "Host" header.

   Historically, user names have been coupled to (Basic and Digest)
   authentication.  This is not generally correct; the user name in the
   URI indicates a resource name space, not an (authenticating) visitor.
   By using a new header field, this specification allows authentication
   to be orthogonal to resource name space selection.

   Some user agents have supported (Basic and Digest) authentication
   with a "user:password" format in the authority section of URIs.  This
   has now been deprecated [Section 3.2.1 of [RFC3986]] but the form
   with just "user" and no ":password" continues to be acceptable.
   Various HTTP clients have different handling for this form, sometimes
   flagging it incorrectly as a security hazard, which also motivates a
   specification for proper handling.

   TODO: Issue filed with HTTPbis, https://github.com/httpwg/http-core/
   issues/278 and offered a Pull Request, https://github.com/httpwg/
   http-core/compare/master...arpa2:userinfo-password as a followup of
   somewhat late Errata against RFC7230, https://www.rfc-

   The purpose of this specification is to define clear meaning for HTTP
   URIs with a user name.

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2.  The HTTP User Header

   The "User" header field provides an aspect of the desired resource
   name scope.  The value is usually taken from the authority section
   [Section 3.2 of [RFC3986]] of the target URI and MUST NOT include a
   ":" colon (U+003a) character.

   The User header value holds precisely one value with the following
   ABNF grammar:

   User = 1*( unreserved / pct-encoded / sub-delims )

   The referenced non-terminals are as for URIs [RFC3986].  Zeal in the
   use of the "pct-encoded" non-terminal for plain characters that have
   a direct representation MAY be treated as an attempted attack.

   The User header MAY appear in requests and MUST NOT occur in

   When unrecognised by HTTP servers, the User header is ignored
   [Section 3.2.1 of [RFC7230]].  Intermediates such as proxies and
   caches MUST NOT add, remove or modify the User header.

3.  Protocol Handling of HTTP User

   User agents SHOULD render user names in authority sections whenever
   they render host names, though it may be helpful if it stands out
   graphically [Section 7.6 of [RFC3986]].  User agents SHOULD NOT
   remove user names from the target URI.  User agents MAY remove the
   "@" (U+0040) symbol from a URI when the preceding user name is empty.
   User agents MUST refuse URIs with a ":" colon (U+003a) in the user
   name but MUST NOT complain about a user name that does not have that

   During redirects or other traversals to (relative) HTTP URIs, the
   user name MUST be overwritten when the new URI specifies an authority
   component, and it MUST be kept otherwise.

4.  Caching Behaviour

   The privacy or security of an HTTP resource is not impacted by the
   use of a User header.  This is because User is about resource
   location, but not about client identity.

   HTTP caches [RFC7234] need to distinguish requests with different
   User header values.  The Vary header [Section 7.1.4 of [RFC7231]]
   MUST be present in the matching response, and the header MUST either
   be a single "*" star (U+002a) or list the "user" name, for all

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   responses whose processing was influenced by the User header.  This
   requirement does not apply to software and configurations that ignore
   the User header.

5.  IANA Considerations

   IANA adds the following entry to the Message Headers registry:

   Header Field Name   Template   Protocol   Status    Reference
   ------------------  ---------  ---------  -------   ----------
   User                           http       TBD       TBD:THIS_SPEC

6.  Security Considerations

   The User header field as defined herein is orthogonal to issues of
   authentication or authorisation, and adds no security concerns.

7.  Normative References

   [RFC3986]  Berners-Lee, T., Fielding, R., and L. Masinter, "Uniform
              Resource Identifier (URI): Generic Syntax", STD 66,
              RFC 3986, DOI 10.17487/RFC3986, January 2005,

   [RFC7230]  Fielding, R., Ed. and J. Reschke, Ed., "Hypertext Transfer
              Protocol (HTTP/1.1): Message Syntax and Routing",
              RFC 7230, DOI 10.17487/RFC7230, June 2014,

   [RFC7231]  Fielding, R., Ed. and J. Reschke, Ed., "Hypertext Transfer
              Protocol (HTTP/1.1): Semantics and Content", RFC 7231,
              DOI 10.17487/RFC7231, June 2014,

   [RFC7234]  Fielding, R., Ed., Nottingham, M., Ed., and J. Reschke,
              Ed., "Hypertext Transfer Protocol (HTTP/1.1): Caching",
              RFC 7234, DOI 10.17487/RFC7234, June 2014,

   [RFC7542]  DeKok, A., "The Network Access Identifier", RFC 7542,
              DOI 10.17487/RFC7542, May 2015,

Appendix A.  HTTP User Environment Variable

   The following variable SHOULD be passed up to applications on a HTTP

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   HTTP_USER  gives the HTTP User header value after parsing and
         percent-decoding.  Like the customary variables HTTP_HOST and
         PATH_INFO, this specifies the resource being requested.  The
         HTTP_USER header does not describe the identity of the HTTP

Author's Address

   Rick van Rein
   Haarlebrink 5
   Enschede, Overijssel  7544 WP
   The Netherlands

   Email: rick@openfortress.nl

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