Internet DRAFT - draft-vanrein-http-unauth-user
draft-vanrein-http-unauth-user
Network Working Group R. Van Rein
Internet-Draft InternetWide.org
Intended status: Standards Track February 3, 2020
Expires: August 6, 2020
HTTP Resources with User Names
draft-vanrein-http-unauth-user-05
Abstract
Many protocols support users under domain names, but HTTP does not.
This specification defines a header for user names, independent of
authenticated identities, and a link to userinfo in HTTP URIs. This
intergrates naturally with HTTP, and results in a more refined
resource authentication model, in support of advanced usage
scenarios.
Status of This Memo
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This Internet-Draft will expire on August 6, 2020.
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the Trust Legal Provisions and are provided without warranty as
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
2. Definition of the HTTP User Header . . . . . . . . . . . . . 3
3. URI with Resource User . . . . . . . . . . . . . . . . . . . 3
4. Protocol Handling of URI and User Header . . . . . . . . . . 4
5. The Logic of User in HTTP . . . . . . . . . . . . . . . . . . 5
6. Environment Variable with Local User . . . . . . . . . . . . 6
7. Orthogonality of Authentication (Example) . . . . . . . . . . 6
8. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 8
9. Security Considerations . . . . . . . . . . . . . . . . . . . 8
10. References . . . . . . . . . . . . . . . . . . . . . . . . . 8
10.1. Normative References . . . . . . . . . . . . . . . . . . 8
10.2. Informative References . . . . . . . . . . . . . . . . . 9
Appendix A. Compatibility with Basic Authentication . . . . . . 9
Appendix B. Compatibility with RESTful Patterns . . . . . . . . 10
Appendix C. Compatibility with Caching . . . . . . . . . . . . . 10
Appendix D. Acknowledgements . . . . . . . . . . . . . . . . . . 11
Author's Address . . . . . . . . . . . . . . . . . . . . . . . . 11
1. Introduction
Many protocols support global identities like john@example.com to
represent users like john under domains such as example.com. The URI
format for HTTP can express [Section 2.7.1 of [RFC7230]] such
authority components (with a userid named "resource user" herein),
with an intended interpretation of locating user-specific resources.
Many online applications publish resources on individual users, but
there is no standard in HTTP to express user names to address them.
This specification adds that through a header "User", closely
paralleling the "Host" header.
Some current URIs for HTTP have used the userinfo field in the URI to
express an authentication user (named "client identity" herein), in
spite of the intended use to refine the authority information. This
conflates the resource user with the client identity. This
specification defines client identity and resource user as orthogonal
concepts, and specifies a clear relation to the URI format.
Orthogonality yields a generalisation, but voluntary conflation of
client identity and resource user remains possible. In fact,
software may use it as default behaviour. Servers can be configured
with resource users that demand authentication with the same client
identity; they may even accept authentication with a client identity
as a bypass to the same resource user. Clients may accept
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authentication requests and use the resource user from the target URI
as a hint to the expected client identity.
Orthogonal concepts can however be untied to support advanced use
cases. Servers may use resource users to identify groups and welcome
members to authenticate against such a group resource. While
authenticating, client identities can be drawn from another domain,
so it is possible to "bring your own identity" as long as the server
can rely on a mechanism of realm crossover for credentials.
TOBEREMOVED: We have designed two mechanisms for realm crossover in
other specifications; SXOVER is a SASL mechanism for realm crossover
via a Diameter backend, which can be provisioned to user agents
through HTTP SASL; KXOVER is a Kerberos mechanism that is taken care
of in the KDC. Both rely on DNSSEC, DANE and TLS.
The purpose of this specification is to define clear meaning for http
and https URIs and their userinfo mappings to HTTP.
2. Definition of the HTTP User Header
The "User" header carries a resource user as part of the requested
authority, and therefore refines the resource name scope. The value
can be explicitly inserted
or be
the user in the userinfo component of the target URI.
The User header value holds precisely one value with the following
ABNF grammar:
User = *( unreserved / pct-encoded / sub-delims )
The referenced non-terminals are as for URIs [RFC3986] and can be
directly included in the quoted-string header form; a plain token
cannot express "(", ")", "=", ";" and "," without escaping
[Section 3.2.6 of [RFC7230]]. Note that the header MUST NOT include
a ":" colon (U+003a) character.
3. URI with Resource User
This section is informative.
Naming a user in the authority component of a URI is a general idea,
already used for addressing users with SMTP, SIP, XMPP and many other
protocols. The addition of users in the URIs for HTTP, a refined
resource name is provided, and better crossover of identities with
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these protocols can be achieved. Unlike server-specific user name
mapping conventions, the specified generic meaning of URI userinfo as
part of the authority information enables such crossovers to be
automated.
There is a current practice of writing a client identity in the
userinfo portion of a URI. This is considered useful if it adds
Basic authentication to the first request; Basic can do this because
it does not incorporate a server-sent challenge.
Having never been standardised, the mechanistic side of this practice
is highly diverse, and URIs are far from portable between browsers or
even the various places where they occur within one browser. As a
result, these URIs cannot be distributed freely and their usage
pattern is dedicated to the client software in use. This
specification does completely support [Appendix A] this pattern as a
special case.
This specification follows the URI's intention of the userinfo field,
and prescribes copying its value into the User header. It will
however remove anything from a colon onward, to suppress the portion
of userinfo that should not be rendered [Section 3.2.1 of [RFC3986]]
as well as a colon hinting at an empty password.
4. Protocol Handling of URI and User Header
Compliant user agents MUST pass userinfo from the target URI (up to
but excluding the first colon ":" (U+003a) if it contains any) as a
User header field if, and only if, the target URI contains a userinfo
part. They MUST NOT remove userinfo from the target URI during this
process. Empty userinfo MUST be treated as any other userinfo
string.
The User header MAY appear in requests and MUST NOT occur in
responses.
When sending it, the user agent SHOULD generate User as the next
header field after Host. Transparent intermediates such as proxies
and caches MUST NOT add, remove or modify the User header. The
CONNECT method and Host header both exclude this information, so the
User header complements them.
Compliant servers MAY ignore the User header [Section 3.2.1 of
[RFC7230]] and they MAY impose a more restrictive grammar (like a
NAI's utf8-username [RFC7542]) than the URI syntax before further
processing it. When they do use it, the Effective Request URI
[Section 5.5 of [RFC7230]] MUST be constructed with the userinfo and
the "@" at delimiter (U+0040) prefixed to the host name and optional
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port. Realms are specific to an authority section [Section 2.2 of
[RFC7235]] and so a realm never spans across different userinfo
values.
As a result of a consistent translation of any User header value into
the Effective Request URI, the server would map consistently to
resources. It is merely enabled to include a User header as an extra
input variable to this mapping to resources.
HTTP caches [RFC7234] need to differentiate requests based on the
User header. To accommodate that, the Vary header [Section 7.1.4 of
[RFC7231]] MUST be generated by the server in the matching response,
and the header MUST either be a single "*" star (U+002a) or list the
"User" name, for all responses whose processing was influenced by the
User header. This requirement has no bearing on software and
configurations that ignore the User header.
Compliant user agents MUST NOT change the support of the User header
depending on the source of a reference; be it a redirect form a
server, a click in a hyperlinked document, a script or a part of a
browser interface or an external source. When processing URIs that
are relative to the context of a previous URI, compliant user agents
MUST replace the userinfo in the target URI when the new URI
specifies an authority component, and MUST keep it otherwise.
5. The Logic of User in HTTP
This section is informative.
HTTP structures a number of things around the authority component of
its URIs, and the addition of resource users in this position form a
logical extension. This leads to improved user experiences.
Realms are identified by a scheme, the authority and a descriptive
string passed with authentication challenges. Clients can use this
combination to decide about a client identity to present to a server;
it is common for people to have roles relative to one another, and
the standard definition of realm identity allows the user agent to
select an identity to match the role for the remote party. This can
even be used for credentials passed in the TLS handshake, such as
X.509 certificates.
A similar logic is found for robot exclusion files. They are found
at a path /robots.txt for a given scheme and authority. The
inclusion of the resource user in the authority enables personal
pages to each have their own robot exclusion file.
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More futuristic would be a suggestion that a server may relay
connections to user-operated web servers on the basis of the resource
user; this is once again an intended use of the authority field. It
may not be possible under current specifications yet, but HTTP with
User header can support it as soon as TLS can.
6. Environment Variable with Local User
The following variable SHOULD be passed to applications that run on
top of the HTTP stack in a server:
LOCAL_USER gives the HTTP User header value after syntax checking
and percent-decoding. If used at all, it MUST be treated as a
resource user. This header does not describe the authenticated
client identity, which is usually passed in a variable
REMOTE_USER.
7. Orthogonality of Authentication (Example)
This section is informative.
This section provides an example of an advanced use case. Not only
does this use the resource user to locate a shared server account, it
is also distinct from the client identity used during authentication.
Whether the client identity is welcomed by the resource user is
determined with an access control list. Furthermore, this example
shows the logic of a realm identity that involves the resource user
in finding the right client identity to the contacted resource user.
John and Mary are both part of the Sales group of Example, Inc and
John has written a document that he wants Mary to review. Mary opens
a link to the document name space under the group's shared account
"sales" at https://sales@example.com/docs and her user agent sends:
GET /docs HTTP/1.1
Host: example.com
User: sales
The server redirects to add a slash, and when this is specific to the
sales name space, it must inform caches about this with the Vary
header:
HTTP/1.1 301 Moved Permanently
Location: /docs/
Vary: User
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Since the new location lacks an authority component, this part is
retained from the referring URI, and the user agent redirects to
https://sales@example.com/docs/ by sending:
GET /docs/ HTTP/1.1
Host: example.com
User: sales
By this time, the server runs into access control, and decides that
it needs an authenticated client identity. To this end, it responds
with a challenge to the "Documents" realm:
HTTP/1.1 401 Unauthorized
WWW-Authenticate: KnockKnock realm="Documents"
Vary: User
Mary's user agent needs to collect credentials, and may hint at the
user name "sales" from the URI but, this being the name of a shared
resource, Mary has no fitting credentials and instead authenticates
with client identity "mary":
GET /docs/ HTTP/1.1
Host: example.com
User: sales
Authorization: KnockKnock realm="Documents", user="mary", ...
At some point, the server accepts Mary's authentication and proceeds
to access control. This phase checks if client identity "mary" may
access realm "Documents" of "https://sales@example.com" by checking
that Mary works for the Sales department. Once this is assured, the
server returns the requested document list:
HTTP/1.1 200 OK
Vary: User
Content-Type: text/html
...
<a href="/docs/review.cgi?docid=123">Review 123 now</a>
...
Mary clicks on the link to /docs/review.cgi?docid=123 and her user
agent sees a relative reference with no authority component, so this
is again reused from the referring URI. The new URI is
https://sales@example.com/docs/review.cgi?docid=123 with same root
https://sales@example.com for which Mary has an authenticated client
identity, so the same "Documents" realm can be tried. The user agent
therefore sends:
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GET /docs/review.cgi?docid=123 HTTP/1.1
Host: example.com
User: sales
Authorization: KnockKnock realm="Documents", user="mary", ...
After access control, the server starts the CGI script with
environment variables LOCAL_USER=sales and REMOTE_USER=mary for the
resource user and authenticated client identity, respectively. The
script interprets the LOCAL_USER as a group account and the
REMOTE_USER as the acting group member, and returns a page for review
of the document and Mary can get to work.
8. IANA Considerations
Please add the following entry to the Message Headers registry:
Header Field Name Template Protocol Status Reference
------------------ --------- --------- ------- ----------
User http TBD TBD:THIS_SPEC
9. Security Considerations
The User header field as defined herein is orthogonal to issues of
authentication and authorisation, and adds no security concerns.
10. References
10.1. 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,
<https://www.rfc-editor.org/info/rfc3986>.
[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,
<https://www.rfc-editor.org/info/rfc7230>.
[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,
<https://www.rfc-editor.org/info/rfc7231>.
[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,
<https://www.rfc-editor.org/info/rfc7234>.
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[RFC7235] Fielding, R., Ed. and J. Reschke, Ed., "Hypertext Transfer
Protocol (HTTP/1.1): Authentication", RFC 7235,
DOI 10.17487/RFC7235, June 2014,
<https://www.rfc-editor.org/info/rfc7235>.
10.2. Informative References
[RFC7542] DeKok, A., "The Network Access Identifier", RFC 7542,
DOI 10.17487/RFC7542, May 2015,
<https://www.rfc-editor.org/info/rfc7542>.
Appendix A. Compatibility with Basic Authentication
This appendix is informative.
Basic authentication is regularly used as a quick and easy HTTP
authentication technique. Several user agents continue to support it
with the "user:password@" URI prefix to a hostname, despite its
deprecation [Section 3.2.1 of [RFC3986]]. This specification imposes
no new constraints on this practice; it merely prescribes sending the
User header field, and leaves it to client software whether to also
sends Basic authentication.
The mapping from HTTP requests to resources is the prerogative of the
server. A server supportive of resource selection through Basic
authentication could ignore the User header field and still comply
with this specification. A server that does recognise the User
header field would use it to locate a resource, before deciding about
access control to that resource; it may subsequently require
authentication, and select schemes that could be supported. At this
time, it may or may not welcome an added Basic authentication
attempt. All this depends on server configuration.
This flexibility can support a transition from Basic authentication
to User headers on the server, and allows client software to also
migrate by first adding the User header, and later supporting the
advanced uses by allowing differentiation between resource user and
client identity. Server administrators have a free choice whether to
gradually phase out older clients or to continue to support them.
Sending both the User header and Basic authentication is only to be
expected from user agents who conflate resource user with client
identity. Such user agents will be less flexible, and will not be
able to support more advanced usage patterns that separate these
concepts, such as shared/group resources addressed with the User
header field and, when desired, authentication through a set of other
headers.
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Appendix B. Compatibility with RESTful Patterns
This appendix is informative.
Whether and how the User header is interpreted is the prerogative of
the server. The server will translate resources in the same manner
when provided with the same User header, and may do so without regard
for the HTTP method. The main concern is now if it will be addressed
in the same manner in every case. This depends on the user agents.
Development environments make sending the User header field simple,
so application support is as easy as the applications are flexible.
Binary user agents and ones that may lag behind in updates do however
call for backward compatibility support of consistent translation to
resources.
Backward compatibility can be guaranteed for host names that always
require a User header; all resources would be described with URIs
having a (possibly empty) userinfo field. Failure to send a User
header to such resources when the URI holds userinfo indicates that
the user agent fails to support the User header. When an offer for
Basic authentication is presented, it may be interpreted as the
conflated approach to userinfo, and treated as a substitute for the
User header. If neither is offered, then an error may be reported or
control redirected to another means of selecting a resource user,
perhaps through an alternate local naming convention.
This indicates that the server is able to detect inconsistent
tranlation risks, and avoid accidentally binding a request to an
unintended resource as a result of a missing User header.
Appendix C. Compatibility with Caching
This appendix is informative.
Whether and how the User header is used to find resources is the
prerogative of their server. A conservative cache design might
insert the User header value in request URIs, but lose the capability
of seeing the equivalence of a resource as perceived by the server.
The inclusion of the name "User" in the Vary header of the response
adds explicit non-equivalence information, and thereby provides a
more accurate cache controlling instruction.
Whether a result is "private" is independent of the User header, as
that only signifies a refinement of the resource name space on the
server. The rules that signify authentication as default indicator
of privacy is orthogonal to the User header. Independent inclusion
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of Basic authentication may still invalidate caching, but not as a
result of this specification.
User agents that send Basic authentication will invalidate
intermediate caching. When an empty password is used to select a
resource user, it would improve caching performance to switch from
Basic authentication to the User header.
Appendix D. Acknowledgements
This specification could be improved thanks to input from Daniel
Stenberg, Amos Jeffries, Paul Vixie, James Fuller and Henri Manson.
Author's Address
Rick van Rein
InternetWide.org
Haarlebrink 5
Enschede, Overijssel 7544 WP
The Netherlands
Email: rick@openfortress.nl
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