< draft-ietf-httpbis-bcp56bis-00.txt   draft-ietf-httpbis-bcp56bis-01.txt >
HTTP M. Nottingham HTTP M. Nottingham
Internet-Draft December 12, 2017 Internet-Draft February 12, 2018
Obsoletes: 3205 (if approved) Obsoletes: 3205 (if approved)
Intended status: Best Current Practice Intended status: Best Current Practice
Expires: June 15, 2018 Expires: August 16, 2018
On the use of HTTP as a Substrate On the use of HTTP as a Substrate
draft-ietf-httpbis-bcp56bis-00 draft-ietf-httpbis-bcp56bis-01
Abstract Abstract
HTTP is often used as a substrate for other application protocols. HTTP is often used as a substrate for other application protocols.
This document specifies best practices for these protocols' use of This document specifies best practices for these protocols' use of
HTTP. HTTP.
Note to Readers Note to Readers
Discussion of this draft takes place on the HTTP working group Discussion of this draft takes place on the HTTP working group
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Internet-Drafts are working documents of the Internet Engineering Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF). Note that other groups may also distribute Task Force (IETF). Note that other groups may also distribute
working documents as Internet-Drafts. The list of current Internet- working documents as Internet-Drafts. The list of current Internet-
Drafts is at https://datatracker.ietf.org/drafts/current/. Drafts is at https://datatracker.ietf.org/drafts/current/.
Internet-Drafts are draft documents valid for a maximum of six months Internet-Drafts are draft documents valid for a maximum of six months
and may be updated, replaced, or obsoleted by other documents at any and may be updated, replaced, or obsoleted by other documents at any
time. It is inappropriate to use Internet-Drafts as reference time. It is inappropriate to use Internet-Drafts as reference
material or to cite them other than as "work in progress." material or to cite them other than as "work in progress."
This Internet-Draft will expire on June 15, 2018. This Internet-Draft will expire on August 16, 2018.
Copyright Notice Copyright Notice
Copyright (c) 2017 IETF Trust and the persons identified as the Copyright (c) 2018 IETF Trust and the persons identified as the
document authors. All rights reserved. document authors. All rights reserved.
This document is subject to BCP 78 and the IETF Trust's Legal This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents Provisions Relating to IETF Documents
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publication of this document. Please review these documents publication of this document. Please review these documents
carefully, as they describe your rights and restrictions with respect carefully, as they describe your rights and restrictions with respect
to this document. Code Components extracted from this document must to this document. Code Components extracted from this document must
include Simplified BSD License text as described in Section 4.e of include Simplified BSD License text as described in Section 4.e of
the Trust Legal Provisions and are provided without warranty as the Trust Legal Provisions and are provided without warranty as
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2. Is HTTP Being Used? . . . . . . . . . . . . . . . . . . . . . 4 2. Is HTTP Being Used? . . . . . . . . . . . . . . . . . . . . . 4
3. What's Important About HTTP . . . . . . . . . . . . . . . . . 5 3. What's Important About HTTP . . . . . . . . . . . . . . . . . 5
3.1. Generic Semantics . . . . . . . . . . . . . . . . . . . . 5 3.1. Generic Semantics . . . . . . . . . . . . . . . . . . . . 5
3.2. Links . . . . . . . . . . . . . . . . . . . . . . . . . . 6 3.2. Links . . . . . . . . . . . . . . . . . . . . . . . . . . 6
3.3. Getting Value from HTTP . . . . . . . . . . . . . . . . . 6 3.3. Getting Value from HTTP . . . . . . . . . . . . . . . . . 6
4. Best Practices for Using HTTP . . . . . . . . . . . . . . . . 7 4. Best Practices for Using HTTP . . . . . . . . . . . . . . . . 7
4.1. Specifying the Use of HTTP . . . . . . . . . . . . . . . 7 4.1. Specifying the Use of HTTP . . . . . . . . . . . . . . . 7
4.2. Defining HTTP Resources . . . . . . . . . . . . . . . . . 8 4.2. Defining HTTP Resources . . . . . . . . . . . . . . . . . 8
4.3. HTTP URLs . . . . . . . . . . . . . . . . . . . . . . . . 9 4.3. HTTP URLs . . . . . . . . . . . . . . . . . . . . . . . . 9
4.3.1. Initial URL Discovery . . . . . . . . . . . . . . . . 9 4.3.1. Initial URL Discovery . . . . . . . . . . . . . . . . 9
4.3.2. URL Schemes . . . . . . . . . . . . . . . . . . . . . 9 4.3.2. URL Schemes . . . . . . . . . . . . . . . . . . . . . 10
4.3.3. Transport Ports . . . . . . . . . . . . . . . . . . . 10 4.3.3. Transport Ports . . . . . . . . . . . . . . . . . . . 11
4.4. HTTP Methods . . . . . . . . . . . . . . . . . . . . . . 11 4.4. HTTP Methods . . . . . . . . . . . . . . . . . . . . . . 11
4.5. HTTP Status Codes . . . . . . . . . . . . . . . . . . . . 11 4.5. HTTP Status Codes . . . . . . . . . . . . . . . . . . . . 12
4.6. HTTP Header Fields . . . . . . . . . . . . . . . . . . . 12 4.6. HTTP Header Fields . . . . . . . . . . . . . . . . . . . 13
4.7. Defining Message Payloads . . . . . . . . . . . . . . . . 13 4.7. Defining Message Payloads . . . . . . . . . . . . . . . . 14
4.8. Ensuring Browser Interoperability . . . . . . . . . . . . 13 4.8. Authentication and Application State . . . . . . . . . . 14
4.9. Access Control . . . . . . . . . . . . . . . . . . . . . 13 4.9. Co-Existing with Web Browsing . . . . . . . . . . . . . . 14
4.9.1. Authentication and Application State . . . . . . . . 13 4.10. Co-Existing with Other Applications . . . . . . . . . . . 15
5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 13 5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 15
6. Security Considerations . . . . . . . . . . . . . . . . . . . 14 6. Security Considerations . . . . . . . . . . . . . . . . . . . 15
7. References . . . . . . . . . . . . . . . . . . . . . . . . . 14 7. References . . . . . . . . . . . . . . . . . . . . . . . . . 16
7.1. Normative References . . . . . . . . . . . . . . . . . . 14 7.1. Normative References . . . . . . . . . . . . . . . . . . 16
7.2. Informative References . . . . . . . . . . . . . . . . . 15 7.2. Informative References . . . . . . . . . . . . . . . . . 18
7.3. URIs . . . . . . . . . . . . . . . . . . . . . . . . . . 17 7.3. URIs . . . . . . . . . . . . . . . . . . . . . . . . . . 20
Appendix A. Changes from RFC3205 . . . . . . . . . . . . . . . . 17 Appendix A. Changes from RFC3205 . . . . . . . . . . . . . . . . 20
Author's Address . . . . . . . . . . . . . . . . . . . . . . . . 17 Author's Address . . . . . . . . . . . . . . . . . . . . . . . . 20
1. Introduction 1. Introduction
HTTP [RFC7230] is often used as a substrate for other application HTTP [RFC7230] is often used as a substrate for other application
protocols. This is done for a variety of reasons, including: protocols. This is done for a variety of reasons, including:
o familiarity by implementers, specifiers, administrators, o familiarity by implementers, specifiers, administrators,
developers and users, developers and users,
o availability of a variety of client, server and proxy o availability of a variety of client, server and proxy
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2. Is HTTP Being Used? 2. Is HTTP Being Used?
Different applications have different goals when using HTTP. In this Different applications have different goals when using HTTP. In this
document, we say an application is _using HTTP_ when any of the document, we say an application is _using HTTP_ when any of the
following conditions are true: following conditions are true:
o The transport port in use is 80 or 443, o The transport port in use is 80 or 443,
o The URL scheme "http" or "https" is used, o The URL scheme "http" or "https" is used,
o The ALPN protocol ID [RFC7301] "http/1.1", "h2" or "h2c" is used, o The ALPN protocol ID [RFC7301] generically identifies HTTP (e.g.,
or "http/1.1", "h2", "h2c"), or
o The message formats described in [RFC7230] and/or [RFC7540] are o The message formats described in [RFC7230] and/or [RFC7540] are
used in conjunction with the IANA registries defined for HTTP. used in conjunction with the IANA registries defined for HTTP.
When an application is using HTTP, all of the requirements of the When an application is using HTTP, all of the requirements of the
HTTP protocol suite (including but not limited to [RFC7230], HTTP protocol suite (including but not limited to [RFC7230],
[RFC7231], [RFC7232], [RFC7233], [RFC7234], [RFC7235] and [RFC7540]) [RFC7231], [RFC7232], [RFC7233], [RFC7234], [RFC7235] and [RFC7540])
are in force. are in force.
An application might not be _using HTTP_ according to this An application might not be _using HTTP_ according to this
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outlined above, as most HTTP implementations won't be easily outlined above, as most HTTP implementations won't be easily
adaptable to these changes, and as the protocol diverges from HTTP, adaptable to these changes, and as the protocol diverges from HTTP,
the benefit of mindshare will be lost. the benefit of mindshare will be lost.
Protocols that are based upon HTTP MUST NOT reuse HTTP's URL schemes, Protocols that are based upon HTTP MUST NOT reuse HTTP's URL schemes,
transport ports, ALPN protocol IDs or IANA registries; rather, they transport ports, ALPN protocol IDs or IANA registries; rather, they
are encouraged to establish their own. are encouraged to establish their own.
3. What's Important About HTTP 3. What's Important About HTTP
There are many ways that HTTP applications are defined and deployed, There are many ways that applications using HTTP are defined and
and sometimes they are brought to the IETF for standardisation. In deployed, and sometimes they are brought to the IETF for
that process, what might be workable for deployment in a limited standardisation. In that process, what might be workable for
fashion isn't appropriate for standardisation and the corresponding deployment in a limited fashion isn't appropriate for standardisation
broader deployment. and the corresponding broader deployment.
This section examines the facets of the protocol that are important This section examines the facets of the protocol that are important
to preserve in these situations. to preserve in these situations.
3.1. Generic Semantics 3.1. Generic Semantics
When writing an application's specification, it's often tempting to When writing an application's specification, it's often tempting to
specify exactly how HTTP is to be implemented, supported and used. specify exactly how HTTP is to be implemented, supported and used.
However, this can easily lead to an unintended profile of HTTP's However, this can easily lead to an unintended profile of HTTP's
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status code might differ in a real deployment. If the client does status code might differ in a real deployment. If the client does
not anticipate this, the application's deployment is brittle. not anticipate this, the application's deployment is brittle.
Much of the value of HTTP is in its _generic semantics_ - that is, Much of the value of HTTP is in its _generic semantics_ - that is,
the protocol elements defined by HTTP are potentially applicable to the protocol elements defined by HTTP are potentially applicable to
every resource, not specific to a particular context. Application- every resource, not specific to a particular context. Application-
specific semantics are expressed in the payload; mostly, in the body, specific semantics are expressed in the payload; mostly, in the body,
but also in header fields. but also in header fields.
This allows a HTTP message to be examined by generic HTTP software This allows a HTTP message to be examined by generic HTTP software
(e.g., HTTP servers, intermediaries, client implementatiions), and (e.g., HTTP servers, intermediaries, client implementations), and its
its handling to be correctly determined. It also allows people to handling to be correctly determined. It also allows people to
leverage their knowledge of HTTP semantics without special-casing leverage their knowledge of HTTP semantics without special-casing
them for a particular application. them for a particular application.
Therefore, applications that use HTTP MUST NOT re-define, refine or Therefore, applications that use HTTP MUST NOT re-define, refine or
overlay the semantics of defined protocol elements. Instead, they overlay the semantics of defined protocol elements. Instead, they
SHOULD focus their specifications on protocol elements that are SHOULD focus their specifications on protocol elements that are
specific to them; namely their HTTP resources. specific to that application; namely their HTTP resources.
See Section 4.2 for details. See Section 4.2 for details.
3.2. Links 3.2. Links
Another common practice is assuming that the HTTP server's name space Another common practice is assuming that the HTTP server's name space
(or a portion thereof) is exclusively for the use of a single (or a portion thereof) is exclusively for the use of a single
application. This effectively overlays special, application-specific application. This effectively overlays special, application-specific
semantics onto that space, precludes other applications from using semantics onto that space, precludes other applications from using
it. it.
As explained in [RFC7320], such "squatting" on a part of the URL As explained in [RFC7320], such "squatting" on a part of the URL
space by a standard usurps the server's authority over its own space by a standard usurps the server's authority over its own
resources, can cause deployment issues, and is therefore bad practice resources, can cause deployment issues, and is therefore bad practice
in standards. in standards.
Instead of statically defining URL paths, it is RECOMMENDED that Instead of statically defining URL components like paths, it is
applications using HTTP define links in payloads, to allow RECOMMENDED that applications using HTTP define links in payloads, to
flexibility in deployment. allow flexibility in deployment.
Using runtime links in this fashion has a number of other benefits. Using runtime links in this fashion has a number of other benefits.
For example, navigating with a link allows a request to be routed to For example, navigating with a link allows a request to be routed to
a different server without the overhead of a redirection, thereby a different server without the overhead of a redirection, thereby
supporting deployment across machines well. It becomes possible to supporting deployment across machines well. It becomes possible to
"mix" different applications on the same server, and offers a natural "mix" different applications on the same server, and offers a natural
path for extensibility, versioning and capability management. path for extensibility, versioning and capability management.
3.3. Getting Value from HTTP 3.3. Getting Value from HTTP
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function SHOULD degrade gracefully if they are not (although this function SHOULD degrade gracefully if they are not (although this
might be achieved by informing the user that their task cannot be might be achieved by informing the user that their task cannot be
completed). completed).
For example, an application can specify that it uses HTTP like this: For example, an application can specify that it uses HTTP like this:
Foo Application uses HTTP {{RFC7230}}. Implementations MUST support Foo Application uses HTTP {{RFC7230}}. Implementations MUST support
HTTP/1.1, and MAY support later versions. Support for common HTTP HTTP/1.1, and MAY support later versions. Support for common HTTP
mechanisms such as redirection and caching are assumed. mechanisms such as redirection and caching are assumed.
When specifying examples of protocol interactions, applications
SHOULD document both the request and response messages, with full
headers, preferably in HTTP/1.1 format. For example:
GET /thing HTTP/1.1
Host: example.com
Accept: application/things+json
User-Agent: Foo/1.0
HTTP/1.1 200 OK
Content-Type: application/things+json
Content-Length: 500
Server: Bar/2.2
[payload here]
4.2. Defining HTTP Resources 4.2. Defining HTTP Resources
HTTP Applications SHOULD focus on defining the following application- HTTP Applications SHOULD focus on defining the following application-
specific protocol elements: specific protocol elements:
o Media types [RFC6838], often based upon a format convention such o Media types [RFC6838], often based upon a format convention such
as JSON [RFC7159], as JSON [RFC7159],
o HTTP header fields, as per Section 4.6, and o HTTP header fields, as per Section 4.6, and
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server by requesting an initial document that contains information server by requesting an initial document that contains information
about that particular deployment, potentially including links to about that particular deployment, potentially including links to
other relevant resources. other relevant resources.
Applications that use HTTP SHOULD allow an arbitrary URL to be used Applications that use HTTP SHOULD allow an arbitrary URL to be used
as that entry point. For example, rather than specifying "the as that entry point. For example, rather than specifying "the
initial document is at "/foo/v1", they should allow a deployment to initial document is at "/foo/v1", they should allow a deployment to
use any URL as the entry point for the application. use any URL as the entry point for the application.
In cases where doing so is impractical (e.g., it is not possible to In cases where doing so is impractical (e.g., it is not possible to
convey a whole URL, but only a hostname) applications that use HTTP convey a whole URL, but only a hostname) standard applications that
MAY define a well-known URL [RFC5785] as an entry point. use HTTP can request a well-known URL [RFC5785] as an entry point.
4.3.2. URL Schemes 4.3.2. URL Schemes
Applications that use HTTP will typically use the "http" and/or Applications that use HTTP will typically use the "http" and/or
"https" URL schemes. "https" is preferred to mitigate pervasive "https" URL schemes. "https" is preferred to provide authentication,
integrity and confidentiality, as well as mitigate pervasive
monitoring attacks [RFC7258]. monitoring attacks [RFC7258].
However, application-specific schemes can be defined as well. However, application-specific schemes can be defined as well.
When defining an URL scheme for an application using HTTP, there are When defining an URL scheme for an application using HTTP, there are
a number of tradeoffs and caveats to keep in mind: a number of tradeoffs and caveats to keep in mind:
o Unmodified Web browsers will not support the new scheme. While it o Unmodified Web browsers will not support the new scheme. While it
is possible to register new URL schemes with Web browsers (e.g. is possible to register new URL schemes with Web browsers (e.g.
registerProtocolHandler() in [HTML5] Section 8.7.1.3, as well as registerProtocolHandler() in [HTML5] Section 8.7.1.3, as well as
several proprietary approaches), support for these mechanisms is several proprietary approaches), support for these mechanisms is
not shared by all browsers, and their capabilities can vary. not shared by all browsers, and their capabilities vary.
o Likewise, existing non-browser clients, intermediaries, servers o Existing non-browser clients, intermediaries, servers and
and associated software will not recognise the new scheme, and associated software will not recognise the new scheme. For
might fail to operate. For example, a client library might fail example, a client library might fail to dispatch the request; a
to dispatch the request; a cache might refuse to store the cache might refuse to store the response, and a proxy might fail
response, and a proxy might fail to forward the request. to forward the request.
o Because URLs occur in and are generated in HTTP artefacts o Because URLs occur in and are generated in HTTP artefacts
commonly, often without human intervention (e.g., in the commonly, often without human intervention (e.g., in the
"Location" header), it can be difficult to assure that the new "Location" response header), it can be difficult to assure that
scheme is used consistently. the new scheme is used consistently.
o The resources identified by the new scheme will still be available o The resources identified by the new scheme will still be available
with "http" and/or "https" URLs to clients. While it is possible using "http" and/or "https" URLs. Those URLs can "leak" into use,
to define the relationship between these resources in the new which can present security and operability issues. For example,
scheme's specification, existing HTTP software (such as clients, using a new scheme to assure that requests don't get sent to a
caches, intermediaries and servers) will not be available, so "normal" Web site is likely to fail.
there is a danger of confusion when the "wrong" URL is used.
o Features that rely upon the URL's origin [RFC6454], such as the o Features that rely upon the URL's origin [RFC6454], such as the
Web's same-origin policy, will be impacted by a change of scheme. Web's same-origin policy, will be impacted by a change of scheme.
o HTTP-specific features such as cookies [RFC6265], authentication o HTTP-specific features such as cookies [RFC6265], authentication
[RFC7235], caching [RFC7234], and CORS [FETCH] might or might not [RFC7235], caching [RFC7234], and CORS [FETCH] might or might not
work correctly, depending on how they are defined and implemented. work correctly, depending on how they are defined and implemented.
Generally, they are designed and implemented with an assumption Generally, they are designed and implemented with an assumption
that the URL will always be "http" or "https". that the URL will always be "http" or "https".
o Web features that require a secure context o Web features that require a secure context
[W3C.CR-secure-contexts-20160915] will likely treat a new scheme [W3C.CR-secure-contexts-20160915] will likely treat a new scheme
as insecure. as insecure.
See [RFC7595] for more information about minting new URL schemes. See [RFC7595] for more information about minting new URL schemes.
4.3.3. Transport Ports 4.3.3. Transport Ports
Applications that use HTTP SHOULD use the default port for the URL Applications that use HTTP can use the applicable default port (80
scheme in use. If it is felt that networks might need to distinguish for HTTP, 443 for HTTPS), or they can be deployed upon other ports.
the application's traffic for operational reasons, it MAY register a This decision can be made at deployment time, or might be encouraged
separate port, but be aware that this has privacy implications for by the application's specification (e.g., by registering a port for
that protocol's users. The impact of doing so MUST be documented in that application).
In either case, non-default ports will need to be reflected in the
authority of all URLs for that resource; the only mechanism for
changing a default port is changing the scheme (see Section 4.3.2).
Using a port other than the default has privacy implications (i.e.,
the protocol can now be distinguished from other traffic), as well as
operability concerns (as some networks might block or otherwise
interfere with it). Privacy implications SHOULD be documented in
Security Considerations. Security Considerations.
See [RFC7605] for further guidance. See [RFC7605] for further guidance.
4.4. HTTP Methods 4.4. HTTP Methods
Applications that use HTTP MUST confine themselves to using Applications that use HTTP MUST confine themselves to using
registered HTTP methods such as GET, POST, PUT, DELETE, and PATCH. registered HTTP methods such as GET, POST, PUT, DELETE, and PATCH.
New HTTP methods are rare; they are required to be registered with New HTTP methods are rare; they are required to be registered with
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Therefore, applications MUST NOT specify additional semantics or Therefore, applications MUST NOT specify additional semantics or
refine existing semantics for status codes. refine existing semantics for status codes.
In particular, specifying that a particular status code has a In particular, specifying that a particular status code has a
specific meaning in the context of an application is harmful, as specific meaning in the context of an application is harmful, as
these are not generic semantics, since the consumer needs to be in these are not generic semantics, since the consumer needs to be in
the context of the application to understand them. the context of the application to understand them.
Furthermore, applications using HTTP MUST NOT re-specify the Furthermore, applications using HTTP MUST NOT re-specify the
semantics of HTTP status codes, even if it is only by copying their semantics of HTTP status codes, even if it is only by copying their
definition. They MUST NOT require specific status phrases to be definition. They MUST NOT require specific reason phrases to be
used; the status phrase has no function in HTTP, and is not used; the reason phrase has no function in HTTP, and is not
guaranteed to be preserved by implementations. guaranteed to be preserved by implementations. The reason phrase is
not carried in the [RFC7540] message format.
Typically, applications using HTTP will convey application-specific Typically, applications using HTTP will convey application-specific
information in the message body and/or HTTP header fields, not the information in the message body and/or HTTP header fields, not the
status code. status code.
Specifications sometimes also create a "laundry list" of potential Specifications sometimes also create a "laundry list" of potential
status codes, in an effort to be helpful. The problem with doing so status codes, in an effort to be helpful. The problem with doing so
is that such a list is never complete; for example, if a network is that such a list is never complete; for example, if a network
proxy is interposed, the client might encounter a "407 Proxy proxy is interposed, the client might encounter a "407 Proxy
Authentication Required" response; or, if the server is rate limiting Authentication Required" response; or, if the server is rate limiting
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RECOMMENDED. RECOMMENDED.
New header fields MUST be registered, as per [RFC7231] and [RFC3864]. New header fields MUST be registered, as per [RFC7231] and [RFC3864].
It is RECOMMENDED that header field names be short (even when HTTP/2 It is RECOMMENDED that header field names be short (even when HTTP/2
header compression is in effect, there is an overhead) but header compression is in effect, there is an overhead) but
appropriately specific. In particular, if a header field is specific appropriately specific. In particular, if a header field is specific
to an application, an identifier for that application SHOULD form a to an application, an identifier for that application SHOULD form a
prefix to the header field name, separated by a "-". prefix to the header field name, separated by a "-".
For example, if the "example" application needs to create three
headers, they might be called "example-foo", "example-bar" and
"example-baz". Note that the primary motivation here is to avoid
consuming more generic header names, not to reserve a portion of the
namespace for the application; see [RFC6648] for related
considerations.
The semantics of existing HTTP header fields MUST NOT be re-defined The semantics of existing HTTP header fields MUST NOT be re-defined
without updating their registration or defining an extension to them without updating their registration or defining an extension to them
(if allowed). For example, an application using HTTP cannot specify (if allowed). For example, an application using HTTP cannot specify
that the "Location" header has a special meaning in a certain that the "Location" header has a special meaning in a certain
context. context.
See Section 4.9.1 for requirements regarding header fields that carry See Section 4.8 for requirements regarding header fields that carry
application state (e.g,. Cookie). application state (e.g,. Cookie).
4.7. Defining Message Payloads 4.7. Defining Message Payloads
4.8. Ensuring Browser Interoperability There are many potential formats for payloads; for example, JSON
[RFC8259] and XML [W3C.REC-xml-20081126]. Best practices for their
4.9. Access Control use are out of scope for this document.
Modern Web browsers constrain the ability of content from one origin Applications SHOULD register distinct media types for each format
(as defined by [RFC6454]) to access resources from another, to avoid they define; this makes it possible to identify them unambiguously
the "confused deputy" problem. As a result, applications that wish and negotiate for their use. See [RFC6838] for more information.
to expose cross-origin data to browsers will need to implement
[W3C.REC-cors-20140116].
4.9.1. Authentication and Application State 4.8. Authentication and Application State
Applications that use HTTP MAY use stateful cookies [RFC6265] to Applications that use HTTP MAY use stateful cookies [RFC6265] to
identify a client and/or store client-specific data to contextualise identify a client and/or store client-specific data to contextualise
requests. requests.
If it is only necessary to identify clients, applications that use If it is only necessary to identify clients, applications that use
HTTP MAY use HTTP authentication [RFC7235]; if the Basic HTTP MAY use HTTP authentication [RFC7235]; if either of the Basic
authentication scheme [RFC7617] is used, it MUST NOT be used with the [RFC7617] or Digest [RFC7616] authentication schemes is used, it MUST
'http' URL scheme. NOT be used with the 'http' URL scheme.
In either case, it is important to carefully specify the scoping and In either case, it is important to carefully specify the scoping and
use of these mechanisms; if they expose sensitive data or use of these mechanisms; if they expose sensitive data or
capabilities (e.g., by acting as an ambient authority), exploits are capabilities (e.g., by acting as an ambient authority), exploits are
possible. Mitigations include using a request-specific token to possible. Mitigations include using a request-specific token to
assure the intent of the client. assure the intent of the client.
Applications MUST NOT make assumptions about the relationship between
separate requests on a single transport connection; doing so breaks
many of the assumptions of HTTP as a stateless protocol, and will
cause problems in interoperability, security, operability and
evolution.
4.9. Co-Existing with Web Browsing
Even if there is not an intent for an application that uses HTTP to
be used with a Web browser, its resources will remain available to
browsers and other HTTP clients.
This means that all such applications need to consider how browsers
will interact with them, particularly regarding security.
For example, if an application's state can be changed using a POST
request, a Web browser can easily be coaxed into making that request
by a HTML form on an arbitrary Web site.
Or, if a resource reflects data from the request into a response,
that can be used to perform a Cross-Site Scripting attack on Web
browsers directed to it.
This is only a small sample of the kinds of issues that applications
using HTTP must consider. Generally, the best approach is to
consider the application _as_ a Web application, and to follow best
practices for their secure development.
A complete enumeration of such practices is out of scope for this
document. External resources are numerous; e.g.,
https://www.owasp.org/index.php/OWASP_Guide_Project [4].
4.10. Co-Existing with Other Applications
Because the origin [RFC6454] is how many HTTP capabilities are
scoped, applications also need to consider how deployments might
interact with other applications (including Web browsing) on the same
origin.
For example, if Cookies [RFC6265] are used to carry application
state, they will be sent with all requests to the origin by default,
unless scoped by path, and the application might receive cookies from
other applications on the origin. This can lead to security issues,
as well as collisions in cookie name.
As a result, when specifying the use of Cookies, HTTP authentication
[RFC7235], or other origin-wide HTTP mechanisms, applications using
HTTP SHOULD NOT mandate the use of a particular identifier, but
instead let deployments configure them.
Note that dedicating a hostname to a single application is not a
solution to the issues above; see [RFC7320].
Modern Web browsers constrain the ability of content from one origin
to access resources from another, to avoid the "confused deputy"
problem. As a result, applications that wish to expose cross-origin
data to browsers will need to implement [W3C.REC-cors-20140116].
5. IANA Considerations 5. IANA Considerations
This document has no requirements for IANA. This document has no requirements for IANA.
6. Security Considerations 6. Security Considerations
Section 4.9.1 discusses the impact of using stateful mechanisms in Section 4.8 discusses the impact of using stateful mechanisms in the
the protocol as ambient authority, and suggests a mitigation. protocol as ambient authority, and suggests a mitigation.
Section 4.3.2 requires support for 'https' URLs, and discourages the Section 4.3.2 requires support for 'https' URLs, and discourages the
use of 'http' URLs, to mitigate pervasive monitoring attacks. use of 'http' URLs, to provide authentication, integrity and
confidentiality, as well as mitigate pervasive monitoring attacks.
Section 4.9 highlights the implications of Web browsers' capabilities
on applications that use HTTP.
Applications that use HTTP in a manner that involves modification of Applications that use HTTP in a manner that involves modification of
implementations - for example, requiring support for a new URL implementations - for example, requiring support for a new URL
scheme, or a non-standard method - risk having those implementations scheme, or a non-standard method - risk having those implementations
"fork" from their parent HTTP implementations, with the possible "fork" from their parent HTTP implementations, with the possible
result that they do not benefit from patches and other security result that they do not benefit from patches and other security
improvements incorporated upstream. improvements incorporated upstream.
7. References 7. References
skipping to change at page 14, line 38 skipping to change at page 16, line 37
[RFC3864] Klyne, G., Nottingham, M., and J. Mogul, "Registration [RFC3864] Klyne, G., Nottingham, M., and J. Mogul, "Registration
Procedures for Message Header Fields", BCP 90, RFC 3864, Procedures for Message Header Fields", BCP 90, RFC 3864,
DOI 10.17487/RFC3864, September 2004, DOI 10.17487/RFC3864, September 2004,
<https://www.rfc-editor.org/info/rfc3864>. <https://www.rfc-editor.org/info/rfc3864>.
[RFC5988] Nottingham, M., "Web Linking", RFC 5988, [RFC5988] Nottingham, M., "Web Linking", RFC 5988,
DOI 10.17487/RFC5988, October 2010, DOI 10.17487/RFC5988, October 2010,
<https://www.rfc-editor.org/info/rfc5988>. <https://www.rfc-editor.org/info/rfc5988>.
[RFC6454] Barth, A., "The Web Origin Concept", RFC 6454,
DOI 10.17487/RFC6454, December 2011,
<https://www.rfc-editor.org/info/rfc6454>.
[RFC6648] Saint-Andre, P., Crocker, D., and M. Nottingham,
"Deprecating the "X-" Prefix and Similar Constructs in
Application Protocols", BCP 178, RFC 6648,
DOI 10.17487/RFC6648, June 2012,
<https://www.rfc-editor.org/info/rfc6648>.
[RFC6838] Freed, N., Klensin, J., and T. Hansen, "Media Type [RFC6838] Freed, N., Klensin, J., and T. Hansen, "Media Type
Specifications and Registration Procedures", BCP 13, Specifications and Registration Procedures", BCP 13,
RFC 6838, DOI 10.17487/RFC6838, January 2013, RFC 6838, DOI 10.17487/RFC6838, January 2013,
<https://www.rfc-editor.org/info/rfc6838>. <https://www.rfc-editor.org/info/rfc6838>.
[RFC7230] Fielding, R., Ed. and J. Reschke, Ed., "Hypertext Transfer [RFC7230] Fielding, R., Ed. and J. Reschke, Ed., "Hypertext Transfer
Protocol (HTTP/1.1): Message Syntax and Routing", Protocol (HTTP/1.1): Message Syntax and Routing",
RFC 7230, DOI 10.17487/RFC7230, June 2014, RFC 7230, DOI 10.17487/RFC7230, June 2014,
<https://www.rfc-editor.org/info/rfc7230>. <https://www.rfc-editor.org/info/rfc7230>.
skipping to change at page 15, line 50 skipping to change at page 18, line 12
2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174, 2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174,
May 2017, <https://www.rfc-editor.org/info/rfc8174>. May 2017, <https://www.rfc-editor.org/info/rfc8174>.
[W3C.REC-cors-20140116] [W3C.REC-cors-20140116]
Kesteren, A., "Cross-Origin Resource Sharing", World Wide Kesteren, A., "Cross-Origin Resource Sharing", World Wide
Web Consortium Recommendation REC-cors-20140116, January Web Consortium Recommendation REC-cors-20140116, January
2014, <http://www.w3.org/TR/2014/REC-cors-20140116>. 2014, <http://www.w3.org/TR/2014/REC-cors-20140116>.
7.2. Informative References 7.2. Informative References
[FETCH] various, ., "Fetch - Living Standard", September 2017, [FETCH] WHATWG, "Fetch - Living Standard", n.d.,
<https://fetch.spec.whatwg.org>. <https://fetch.spec.whatwg.org>.
[HTML5] various, ., "HTML - Living Standard", September 2017, [HTML5] WHATWG, "HTML - Living Standard", n.d.,
<https://html.spec.whatwg.org>. <https://html.spec.whatwg.org>.
[RFC0793] Postel, J., "Transmission Control Protocol", STD 7, [RFC0793] Postel, J., "Transmission Control Protocol", STD 7,
RFC 793, DOI 10.17487/RFC0793, September 1981, RFC 793, DOI 10.17487/RFC0793, September 1981,
<https://www.rfc-editor.org/info/rfc793>. <https://www.rfc-editor.org/info/rfc793>.
[RFC0854] Postel, J. and J. Reynolds, "Telnet Protocol [RFC0854] Postel, J. and J. Reynolds, "Telnet Protocol
Specification", STD 8, RFC 854, DOI 10.17487/RFC0854, May Specification", STD 8, RFC 854, DOI 10.17487/RFC0854, May
1983, <https://www.rfc-editor.org/info/rfc854>. 1983, <https://www.rfc-editor.org/info/rfc854>.
skipping to change at page 16, line 43 skipping to change at page 19, line 5
[RFC5785] Nottingham, M. and E. Hammer-Lahav, "Defining Well-Known [RFC5785] Nottingham, M. and E. Hammer-Lahav, "Defining Well-Known
Uniform Resource Identifiers (URIs)", RFC 5785, Uniform Resource Identifiers (URIs)", RFC 5785,
DOI 10.17487/RFC5785, April 2010, DOI 10.17487/RFC5785, April 2010,
<https://www.rfc-editor.org/info/rfc5785>. <https://www.rfc-editor.org/info/rfc5785>.
[RFC6265] Barth, A., "HTTP State Management Mechanism", RFC 6265, [RFC6265] Barth, A., "HTTP State Management Mechanism", RFC 6265,
DOI 10.17487/RFC6265, April 2011, DOI 10.17487/RFC6265, April 2011,
<https://www.rfc-editor.org/info/rfc6265>. <https://www.rfc-editor.org/info/rfc6265>.
[RFC6454] Barth, A., "The Web Origin Concept", RFC 6454,
DOI 10.17487/RFC6454, December 2011,
<https://www.rfc-editor.org/info/rfc6454>.
[RFC6455] Fette, I. and A. Melnikov, "The WebSocket Protocol", [RFC6455] Fette, I. and A. Melnikov, "The WebSocket Protocol",
RFC 6455, DOI 10.17487/RFC6455, December 2011, RFC 6455, DOI 10.17487/RFC6455, December 2011,
<https://www.rfc-editor.org/info/rfc6455>. <https://www.rfc-editor.org/info/rfc6455>.
[RFC7159] Bray, T., Ed., "The JavaScript Object Notation (JSON) Data [RFC7159] Bray, T., Ed., "The JavaScript Object Notation (JSON) Data
Interchange Format", RFC 7159, DOI 10.17487/RFC7159, March Interchange Format", RFC 7159, DOI 10.17487/RFC7159, March
2014, <https://www.rfc-editor.org/info/rfc7159>. 2014, <https://www.rfc-editor.org/info/rfc7159>.
[RFC7258] Farrell, S. and H. Tschofenig, "Pervasive Monitoring Is an [RFC7258] Farrell, S. and H. Tschofenig, "Pervasive Monitoring Is an
Attack", BCP 188, RFC 7258, DOI 10.17487/RFC7258, May Attack", BCP 188, RFC 7258, DOI 10.17487/RFC7258, May
skipping to change at page 17, line 22 skipping to change at page 19, line 26
[RFC7595] Thaler, D., Ed., Hansen, T., and T. Hardie, "Guidelines [RFC7595] Thaler, D., Ed., Hansen, T., and T. Hardie, "Guidelines
and Registration Procedures for URI Schemes", BCP 35, and Registration Procedures for URI Schemes", BCP 35,
RFC 7595, DOI 10.17487/RFC7595, June 2015, RFC 7595, DOI 10.17487/RFC7595, June 2015,
<https://www.rfc-editor.org/info/rfc7595>. <https://www.rfc-editor.org/info/rfc7595>.
[RFC7605] Touch, J., "Recommendations on Using Assigned Transport [RFC7605] Touch, J., "Recommendations on Using Assigned Transport
Port Numbers", BCP 165, RFC 7605, DOI 10.17487/RFC7605, Port Numbers", BCP 165, RFC 7605, DOI 10.17487/RFC7605,
August 2015, <https://www.rfc-editor.org/info/rfc7605>. August 2015, <https://www.rfc-editor.org/info/rfc7605>.
[RFC7616] Shekh-Yusef, R., Ed., Ahrens, D., and S. Bremer, "HTTP
Digest Access Authentication", RFC 7616,
DOI 10.17487/RFC7616, September 2015,
<https://www.rfc-editor.org/info/rfc7616>.
[RFC7617] Reschke, J., "The 'Basic' HTTP Authentication Scheme", [RFC7617] Reschke, J., "The 'Basic' HTTP Authentication Scheme",
RFC 7617, DOI 10.17487/RFC7617, September 2015, RFC 7617, DOI 10.17487/RFC7617, September 2015,
<https://www.rfc-editor.org/info/rfc7617>. <https://www.rfc-editor.org/info/rfc7617>.
[RFC8259] Bray, T., Ed., "The JavaScript Object Notation (JSON) Data
Interchange Format", STD 90, RFC 8259,
DOI 10.17487/RFC8259, December 2017,
<https://www.rfc-editor.org/info/rfc8259>.
[W3C.CR-secure-contexts-20160915] [W3C.CR-secure-contexts-20160915]
West, M., "Secure Contexts", World Wide Web Consortium CR West, M., "Secure Contexts", World Wide Web Consortium CR
CR-secure-contexts-20160915, September 2016, CR-secure-contexts-20160915, September 2016,
<https://www.w3.org/TR/2016/CR-secure-contexts-20160915>. <https://www.w3.org/TR/2016/CR-secure-contexts-20160915>.
[W3C.REC-xml-20081126]
Bray, T., Paoli, J., Sperberg-McQueen, M., Maler, E., and
F. Yergeau, "Extensible Markup Language (XML) 1.0 (Fifth
Edition)", World Wide Web Consortium Recommendation REC-
xml-20081126, November 2008,
<http://www.w3.org/TR/2008/REC-xml-20081126>.
7.3. URIs 7.3. URIs
[1] https://lists.w3.org/Archives/Public/ietf-http-wg/ [1] https://lists.w3.org/Archives/Public/ietf-http-wg/
[2] http://httpwg.github.io/ [2] http://httpwg.github.io/
[3] https://github.com/httpwg/http-extensions/labels/bcp56bis [3] https://github.com/httpwg/http-extensions/labels/bcp56bis
[4] https://www.owasp.org/index.php/OWASP_Guide_Project
Appendix A. Changes from RFC3205 Appendix A. Changes from RFC3205
RFC3205 captured the Best Current Practice in the early 2000's, based RFC3205 captured the Best Current Practice in the early 2000's, based
on the concerns facing protocol designers at the time. Use of HTTP on the concerns facing protocol designers at the time. Use of HTTP
has changed considerably since then, and as a result this document is has changed considerably since then, and as a result this document is
substantially different. As a result, the changes are too numerous substantially different. As a result, the changes are too numerous
to list individually. to list individually.
Author's Address Author's Address
 End of changes. 39 change blocks. 
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