idnits 2.17.1
draft-ietf-httpbis-messaging-18.txt:
Checking boilerplate required by RFC 5378 and the IETF Trust (see
https://trustee.ietf.org/license-info):
----------------------------------------------------------------------------
No issues found here.
Checking nits according to https://www.ietf.org/id-info/1id-guidelines.txt:
----------------------------------------------------------------------------
== There is 1 instance of lines with non-ascii characters in the document.
Checking nits according to https://www.ietf.org/id-info/checklist :
----------------------------------------------------------------------------
-- The draft header indicates that this document obsoletes RFC7230, but the
abstract doesn't seem to directly say this. It does mention RFC7230
though, so this could be OK.
Miscellaneous warnings:
----------------------------------------------------------------------------
== The copyright year in the IETF Trust and authors Copyright Line does not
match the current year
== The document seems to contain a disclaimer for pre-RFC5378 work, but was
first submitted on or after 10 November 2008. The disclaimer is usually
necessary only for documents that revise or obsolete older RFCs, and that
take significant amounts of text from those RFCs. If you can contact all
authors of the source material and they are willing to grant the BCP78
rights to the IETF Trust, you can and should remove the disclaimer.
Otherwise, the disclaimer is needed and you can ignore this comment.
(See the Legal Provisions document at
https://trustee.ietf.org/license-info for more information.)
-- The document date (18 August 2021) is 981 days in the past. Is this
intentional?
Checking references for intended status: Proposed Standard
----------------------------------------------------------------------------
(See RFCs 3967 and 4897 for information about using normative references
to lower-maturity documents in RFCs)
== Outdated reference: A later version (-19) exists of
draft-ietf-httpbis-cache-18
-- Possible downref: Normative reference to a draft: ref. 'CACHING'
== Outdated reference: A later version (-19) exists of
draft-ietf-httpbis-semantics-18
-- Possible downref: Normative reference to a draft: ref. 'HTTP'
** Downref: Normative reference to an Informational RFC: RFC 1950
** Downref: Normative reference to an Informational RFC: RFC 1951
** Downref: Normative reference to an Informational RFC: RFC 1952
-- Possible downref: Non-RFC (?) normative reference: ref. 'USASCII'
-- Possible downref: Non-RFC (?) normative reference: ref. 'Welch'
-- Obsolete informational reference (is this intentional?): RFC 7230 (ref.
'Err4667') (Obsoleted by RFC 9110, RFC 9112)
-- Obsolete informational reference (is this intentional?): RFC 2068
(Obsoleted by RFC 2616)
-- Duplicate reference: RFC7230, mentioned in 'RFC7230', was also mentioned
in 'Err4667'.
-- Obsolete informational reference (is this intentional?): RFC 7230
(Obsoleted by RFC 9110, RFC 9112)
Summary: 3 errors (**), 0 flaws (~~), 5 warnings (==), 10 comments (--).
Run idnits with the --verbose option for more detailed information about
the items above.
--------------------------------------------------------------------------------
2 HTTP Working Group R. Fielding, Ed.
3 Internet-Draft Adobe
4 Obsoletes: 7230 (if approved) M. Nottingham, Ed.
5 Intended status: Standards Track Fastly
6 Expires: 19 February 2022 J. Reschke, Ed.
7 greenbytes
8 18 August 2021
10 HTTP/1.1
11 draft-ietf-httpbis-messaging-18
13 Abstract
15 The Hypertext Transfer Protocol (HTTP) is a stateless application-
16 level protocol for distributed, collaborative, hypertext information
17 systems. This document specifies the HTTP/1.1 message syntax,
18 message parsing, connection management, and related security
19 concerns.
21 This document obsoletes portions of RFC 7230.
23 Editorial Note
25 This note is to be removed before publishing as an RFC.
27 Discussion of this draft takes place on the HTTP working group
28 mailing list (ietf-http-wg@w3.org), which is archived at
29 .
31 Working Group information can be found at ;
32 source code and issues list for this draft can be found at
33 .
35 The changes in this draft are summarized in Appendix D.19.
37 Status of This Memo
39 This Internet-Draft is submitted in full conformance with the
40 provisions of BCP 78 and BCP 79.
42 Internet-Drafts are working documents of the Internet Engineering
43 Task Force (IETF). Note that other groups may also distribute
44 working documents as Internet-Drafts. The list of current Internet-
45 Drafts is at https://datatracker.ietf.org/drafts/current/.
47 Internet-Drafts are draft documents valid for a maximum of six months
48 and may be updated, replaced, or obsoleted by other documents at any
49 time. It is inappropriate to use Internet-Drafts as reference
50 material or to cite them other than as "work in progress."
52 This Internet-Draft will expire on 19 February 2022.
54 Copyright Notice
56 Copyright (c) 2021 IETF Trust and the persons identified as the
57 document authors. All rights reserved.
59 This document is subject to BCP 78 and the IETF Trust's Legal
60 Provisions Relating to IETF Documents (https://trustee.ietf.org/
61 license-info) in effect on the date of publication of this document.
62 Please review these documents carefully, as they describe your rights
63 and restrictions with respect to this document. Code Components
64 extracted from this document must include Simplified BSD License text
65 as described in Section 4.e of the Trust Legal Provisions and are
66 provided without warranty as described in the Simplified BSD License.
68 This document may contain material from IETF Documents or IETF
69 Contributions published or made publicly available before November
70 10, 2008. The person(s) controlling the copyright in some of this
71 material may not have granted the IETF Trust the right to allow
72 modifications of such material outside the IETF Standards Process.
73 Without obtaining an adequate license from the person(s) controlling
74 the copyright in such materials, this document may not be modified
75 outside the IETF Standards Process, and derivative works of it may
76 not be created outside the IETF Standards Process, except to format
77 it for publication as an RFC or to translate it into languages other
78 than English.
80 Table of Contents
82 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 4
83 1.1. Requirements Notation . . . . . . . . . . . . . . . . . . 5
84 1.2. Syntax Notation . . . . . . . . . . . . . . . . . . . . . 5
85 2. Message . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
86 2.1. Message Format . . . . . . . . . . . . . . . . . . . . . 6
87 2.2. Message Parsing . . . . . . . . . . . . . . . . . . . . . 7
88 2.3. HTTP Version . . . . . . . . . . . . . . . . . . . . . . 8
89 3. Request Line . . . . . . . . . . . . . . . . . . . . . . . . 9
90 3.1. Method . . . . . . . . . . . . . . . . . . . . . . . . . 10
91 3.2. Request Target . . . . . . . . . . . . . . . . . . . . . 10
92 3.2.1. origin-form . . . . . . . . . . . . . . . . . . . . . 11
93 3.2.2. absolute-form . . . . . . . . . . . . . . . . . . . . 11
94 3.2.3. authority-form . . . . . . . . . . . . . . . . . . . 12
95 3.2.4. asterisk-form . . . . . . . . . . . . . . . . . . . . 12
96 3.3. Reconstructing the Target URI . . . . . . . . . . . . . . 13
97 4. Status Line . . . . . . . . . . . . . . . . . . . . . . . . . 15
98 5. Field Syntax . . . . . . . . . . . . . . . . . . . . . . . . 16
99 5.1. Field Line Parsing . . . . . . . . . . . . . . . . . . . 16
100 5.2. Obsolete Line Folding . . . . . . . . . . . . . . . . . . 17
101 6. Message Body . . . . . . . . . . . . . . . . . . . . . . . . 17
102 6.1. Transfer-Encoding . . . . . . . . . . . . . . . . . . . . 18
103 6.2. Content-Length . . . . . . . . . . . . . . . . . . . . . 20
104 6.3. Message Body Length . . . . . . . . . . . . . . . . . . . 20
105 7. Transfer Codings . . . . . . . . . . . . . . . . . . . . . . 23
106 7.1. Chunked Transfer Coding . . . . . . . . . . . . . . . . . 23
107 7.1.1. Chunk Extensions . . . . . . . . . . . . . . . . . . 24
108 7.1.2. Chunked Trailer Section . . . . . . . . . . . . . . . 25
109 7.1.3. Decoding Chunked . . . . . . . . . . . . . . . . . . 25
110 7.2. Transfer Codings for Compression . . . . . . . . . . . . 26
111 7.3. Transfer Coding Registry . . . . . . . . . . . . . . . . 26
112 7.4. Negotiating Transfer Codings . . . . . . . . . . . . . . 27
113 8. Handling Incomplete Messages . . . . . . . . . . . . . . . . 28
114 9. Connection Management . . . . . . . . . . . . . . . . . . . . 29
115 9.1. Establishment . . . . . . . . . . . . . . . . . . . . . . 29
116 9.2. Associating a Response to a Request . . . . . . . . . . . 29
117 9.3. Persistence . . . . . . . . . . . . . . . . . . . . . . . 30
118 9.3.1. Retrying Requests . . . . . . . . . . . . . . . . . . 31
119 9.3.2. Pipelining . . . . . . . . . . . . . . . . . . . . . 31
120 9.4. Concurrency . . . . . . . . . . . . . . . . . . . . . . . 32
121 9.5. Failures and Timeouts . . . . . . . . . . . . . . . . . . 32
122 9.6. Tear-down . . . . . . . . . . . . . . . . . . . . . . . . 33
123 9.7. TLS Connection Initiation . . . . . . . . . . . . . . . . 35
124 9.8. TLS Connection Closure . . . . . . . . . . . . . . . . . 35
125 10. Enclosing Messages as Data . . . . . . . . . . . . . . . . . 36
126 10.1. Media Type message/http . . . . . . . . . . . . . . . . 36
127 10.2. Media Type application/http . . . . . . . . . . . . . . 37
128 11. Security Considerations . . . . . . . . . . . . . . . . . . . 38
129 11.1. Response Splitting . . . . . . . . . . . . . . . . . . . 38
130 11.2. Request Smuggling . . . . . . . . . . . . . . . . . . . 39
131 11.3. Message Integrity . . . . . . . . . . . . . . . . . . . 40
132 11.4. Message Confidentiality . . . . . . . . . . . . . . . . 40
133 12. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 41
134 12.1. Field Name Registration . . . . . . . . . . . . . . . . 41
135 12.2. Media Type Registration . . . . . . . . . . . . . . . . 41
136 12.3. Transfer Coding Registration . . . . . . . . . . . . . . 41
137 12.4. ALPN Protocol ID Registration . . . . . . . . . . . . . 42
138 13. References . . . . . . . . . . . . . . . . . . . . . . . . . 43
139 13.1. Normative References . . . . . . . . . . . . . . . . . . 43
140 13.2. Informative References . . . . . . . . . . . . . . . . . 44
141 Appendix A. Collected ABNF . . . . . . . . . . . . . . . . . . . 45
142 Appendix B. Differences between HTTP and MIME . . . . . . . . . 47
143 B.1. MIME-Version . . . . . . . . . . . . . . . . . . . . . . 47
144 B.2. Conversion to Canonical Form . . . . . . . . . . . . . . 47
145 B.3. Conversion of Date Formats . . . . . . . . . . . . . . . 48
146 B.4. Conversion of Content-Encoding . . . . . . . . . . . . . 48
147 B.5. Conversion of Content-Transfer-Encoding . . . . . . . . . 48
148 B.6. MHTML and Line Length Limitations . . . . . . . . . . . . 48
149 Appendix C. Changes from previous RFCs . . . . . . . . . . . . . 49
150 C.1. Changes from HTTP/0.9 . . . . . . . . . . . . . . . . . . 49
151 C.2. Changes from HTTP/1.0 . . . . . . . . . . . . . . . . . . 49
152 C.2.1. Multihomed Web Servers . . . . . . . . . . . . . . . 49
153 C.2.2. Keep-Alive Connections . . . . . . . . . . . . . . . 49
154 C.2.3. Introduction of Transfer-Encoding . . . . . . . . . . 50
155 C.3. Changes from RFC 7230 . . . . . . . . . . . . . . . . . . 50
156 Appendix D. Change Log . . . . . . . . . . . . . . . . . . . . . 51
157 D.1. Between RFC7230 and draft 00 . . . . . . . . . . . . . . 51
158 D.2. Since draft-ietf-httpbis-messaging-00 . . . . . . . . . . 51
159 D.3. Since draft-ietf-httpbis-messaging-01 . . . . . . . . . . 52
160 D.4. Since draft-ietf-httpbis-messaging-02 . . . . . . . . . . 52
161 D.5. Since draft-ietf-httpbis-messaging-03 . . . . . . . . . . 53
162 D.6. Since draft-ietf-httpbis-messaging-04 . . . . . . . . . . 53
163 D.7. Since draft-ietf-httpbis-messaging-05 . . . . . . . . . . 53
164 D.8. Since draft-ietf-httpbis-messaging-06 . . . . . . . . . . 54
165 D.9. Since draft-ietf-httpbis-messaging-07 . . . . . . . . . . 54
166 D.10. Since draft-ietf-httpbis-messaging-08 . . . . . . . . . . 54
167 D.11. Since draft-ietf-httpbis-messaging-09 . . . . . . . . . . 55
168 D.12. Since draft-ietf-httpbis-messaging-10 . . . . . . . . . . 55
169 D.13. Since draft-ietf-httpbis-messaging-11 . . . . . . . . . . 55
170 D.14. Since draft-ietf-httpbis-messaging-12 . . . . . . . . . . 55
171 D.15. Since draft-ietf-httpbis-messaging-13 . . . . . . . . . . 56
172 D.16. Since draft-ietf-httpbis-messaging-14 . . . . . . . . . . 56
173 D.17. Since draft-ietf-httpbis-messaging-15 . . . . . . . . . . 57
174 D.18. Since draft-ietf-httpbis-messaging-16 . . . . . . . . . . 57
175 D.19. Since draft-ietf-httpbis-messaging-17 . . . . . . . . . . 57
176 Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . . 57
177 Index . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 57
178 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 60
180 1. Introduction
182 The Hypertext Transfer Protocol (HTTP) is a stateless application-
183 level request/response protocol that uses extensible semantics and
184 self-descriptive messages for flexible interaction with network-based
185 hypertext information systems. HTTP/1.1 is defined by:
187 * This document
189 * "HTTP Semantics" [HTTP]
190 * "HTTP Caching" [CACHING]
192 This document specifies how HTTP semantics are conveyed using the
193 HTTP/1.1 message syntax, framing and connection management
194 mechanisms. Its goal is to define the complete set of requirements
195 for HTTP/1.1 message parsers and message-forwarding intermediaries.
197 This document obsoletes the portions of RFC 7230 related to HTTP/1.1
198 messaging and connection management, with the changes being
199 summarized in Appendix C.3. The other parts of RFC 7230 are
200 obsoleted by "HTTP Semantics" [HTTP].
202 1.1. Requirements Notation
204 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
205 "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and
206 "OPTIONAL" in this document are to be interpreted as described in BCP
207 14 [RFC2119] [RFC8174] when, and only when, they appear in all
208 capitals, as shown here.
210 Conformance criteria and considerations regarding error handling are
211 defined in Section 2 of [HTTP].
213 1.2. Syntax Notation
215 This specification uses the Augmented Backus-Naur Form (ABNF)
216 notation of [RFC5234], extended with the notation for case-
217 sensitivity in strings defined in [RFC7405].
219 It also uses a list extension, defined in Section 5.6.1 of [HTTP],
220 that allows for compact definition of comma-separated lists using a
221 '#' operator (similar to how the '*' operator indicates repetition).
222 Appendix A shows the collected grammar with all list operators
223 expanded to standard ABNF notation.
225 As a convention, ABNF rule names prefixed with "obs-" denote
226 "obsolete" grammar rules that appear for historical reasons.
228 The following core rules are included by reference, as defined in
229 [RFC5234], Appendix B.1: ALPHA (letters), CR (carriage return), CRLF
230 (CR LF), CTL (controls), DIGIT (decimal 0-9), DQUOTE (double quote),
231 HEXDIG (hexadecimal 0-9/A-F/a-f), HTAB (horizontal tab), LF (line
232 feed), OCTET (any 8-bit sequence of data), SP (space), and VCHAR (any
233 visible [USASCII] character).
235 The rules below are defined in [HTTP]:
237 BWS =
238 OWS =
239 RWS =
240 absolute-path =
241 field-name =
242 field-value =
243 obs-text =
244 quoted-string =
245 token =
246 transfer-coding =
247
249 The rules below are defined in [URI]:
251 absolute-URI =
252 authority =
253 uri-host =
254 port =
255 query =
257 2. Message
259 HTTP/1.1 clients and servers communicate by sending messages. See
260 Section 3 of [HTTP] for the general terminology and core concepts of
261 HTTP.
263 2.1. Message Format
265 An HTTP/1.1 message consists of a start-line followed by a CRLF and a
266 sequence of octets in a format similar to the Internet Message Format
267 [RFC5322]: zero or more header field lines (collectively referred to
268 as the "headers" or the "header section"), an empty line indicating
269 the end of the header section, and an optional message body.
271 HTTP-message = start-line CRLF
272 *( field-line CRLF )
273 CRLF
274 [ message-body ]
276 A message can be either a request from client to server or a response
277 from server to client. Syntactically, the two types of message
278 differ only in the start-line, which is either a request-line (for
279 requests) or a status-line (for responses), and in the algorithm for
280 determining the length of the message body (Section 6).
282 start-line = request-line / status-line
284 In theory, a client could receive requests and a server could receive
285 responses, distinguishing them by their different start-line formats.
286 In practice, servers are implemented to only expect a request (a
287 response is interpreted as an unknown or invalid request method) and
288 clients are implemented to only expect a response.
290 HTTP makes use of some protocol elements similar to the Multipurpose
291 Internet Mail Extensions (MIME) [RFC2045]. See Appendix B for the
292 differences between HTTP and MIME messages.
294 2.2. Message Parsing
296 The normal procedure for parsing an HTTP message is to read the
297 start-line into a structure, read each header field line into a hash
298 table by field name until the empty line, and then use the parsed
299 data to determine if a message body is expected. If a message body
300 has been indicated, then it is read as a stream until an amount of
301 octets equal to the message body length is read or the connection is
302 closed.
304 A recipient MUST parse an HTTP message as a sequence of octets in an
305 encoding that is a superset of US-ASCII [USASCII]. Parsing an HTTP
306 message as a stream of Unicode characters, without regard for the
307 specific encoding, creates security vulnerabilities due to the
308 varying ways that string processing libraries handle invalid
309 multibyte character sequences that contain the octet LF (%x0A).
310 String-based parsers can only be safely used within protocol elements
311 after the element has been extracted from the message, such as within
312 a header field line value after message parsing has delineated the
313 individual field lines.
315 Although the line terminator for the start-line and fields is the
316 sequence CRLF, a recipient MAY recognize a single LF as a line
317 terminator and ignore any preceding CR.
319 A sender MUST NOT generate a bare CR (a CR character not immediately
320 followed by LF) within any protocol elements other than the content.
321 A recipient of such a bare CR MUST consider that element to be
322 invalid or replace each bare CR with SP before processing the element
323 or forwarding the message.
325 Older HTTP/1.0 user agent implementations might send an extra CRLF
326 after a POST request as a workaround for some early server
327 applications that failed to read message body content that was not
328 terminated by a line-ending. An HTTP/1.1 user agent MUST NOT preface
329 or follow a request with an extra CRLF. If terminating the request
330 message body with a line-ending is desired, then the user agent MUST
331 count the terminating CRLF octets as part of the message body length.
333 In the interest of robustness, a server that is expecting to receive
334 and parse a request-line SHOULD ignore at least one empty line (CRLF)
335 received prior to the request-line.
337 A sender MUST NOT send whitespace between the start-line and the
338 first header field.
340 A recipient that receives whitespace between the start-line and the
341 first header field MUST either reject the message as invalid or
342 consume each whitespace-preceded line without further processing of
343 it (i.e., ignore the entire line, along with any subsequent lines
344 preceded by whitespace, until a properly formed header field is
345 received or the header section is terminated). Rejection or removal
346 of invalid whitespace-preceded lines is necessary to prevent their
347 misinterpretation by downstream recipients that might be vulnerable
348 to request smuggling (Section 11.2) or response splitting
349 (Section 11.1) attacks.
351 When a server listening only for HTTP request messages, or processing
352 what appears from the start-line to be an HTTP request message,
353 receives a sequence of octets that does not match the HTTP-message
354 grammar aside from the robustness exceptions listed above, the server
355 SHOULD respond with a 400 (Bad Request) response and close the
356 connection.
358 2.3. HTTP Version
360 HTTP uses a "." numbering scheme to indicate versions
361 of the protocol. This specification defines version "1.1".
362 Section 2.5 of [HTTP] specifies the semantics of HTTP version
363 numbers.
365 The version of an HTTP/1.x message is indicated by an HTTP-version
366 field in the start-line. HTTP-version is case-sensitive.
368 HTTP-version = HTTP-name "/" DIGIT "." DIGIT
369 HTTP-name = %s"HTTP"
371 When an HTTP/1.1 message is sent to an HTTP/1.0 recipient [HTTP/1.0]
372 or a recipient whose version is unknown, the HTTP/1.1 message is
373 constructed such that it can be interpreted as a valid HTTP/1.0
374 message if all of the newer features are ignored. This specification
375 places recipient-version requirements on some new features so that a
376 conformant sender will only use compatible features until it has
377 determined, through configuration or the receipt of a message, that
378 the recipient supports HTTP/1.1.
380 Intermediaries that process HTTP messages (i.e., all intermediaries
381 other than those acting as tunnels) MUST send their own HTTP-version
382 in forwarded messages, unless it is purposefully downgraded as a
383 workaround for an upstream issue. In other words, an intermediary is
384 not allowed to blindly forward the start-line without ensuring that
385 the protocol version in that message matches a version to which that
386 intermediary is conformant for both the receiving and sending of
387 messages. Forwarding an HTTP message without rewriting the HTTP-
388 version might result in communication errors when downstream
389 recipients use the message sender's version to determine what
390 features are safe to use for later communication with that sender.
392 A server MAY send an HTTP/1.0 response to an HTTP/1.1 request if it
393 is known or suspected that the client incorrectly implements the HTTP
394 specification and is incapable of correctly processing later version
395 responses, such as when a client fails to parse the version number
396 correctly or when an intermediary is known to blindly forward the
397 HTTP-version even when it doesn't conform to the given minor version
398 of the protocol. Such protocol downgrades SHOULD NOT be performed
399 unless triggered by specific client attributes, such as when one or
400 more of the request header fields (e.g., User-Agent) uniquely match
401 the values sent by a client known to be in error.
403 3. Request Line
405 A request-line begins with a method token, followed by a single space
406 (SP), the request-target, another single space (SP), and ends with
407 the protocol version.
409 request-line = method SP request-target SP HTTP-version
411 Although the request-line grammar rule requires that each of the
412 component elements be separated by a single SP octet, recipients MAY
413 instead parse on whitespace-delimited word boundaries and, aside from
414 the CRLF terminator, treat any form of whitespace as the SP separator
415 while ignoring preceding or trailing whitespace; such whitespace
416 includes one or more of the following octets: SP, HTAB, VT (%x0B), FF
417 (%x0C), or bare CR. However, lenient parsing can result in request
418 smuggling security vulnerabilities if there are multiple recipients
419 of the message and each has its own unique interpretation of
420 robustness (see Section 11.2).
422 HTTP does not place a predefined limit on the length of a request-
423 line, as described in Section 2 of [HTTP]. A server that receives a
424 method longer than any that it implements SHOULD respond with a 501
425 (Not Implemented) status code. A server that receives a request-
426 target longer than any URI it wishes to parse MUST respond with a 414
427 (URI Too Long) status code (see Section 15.5.15 of [HTTP]).
429 Various ad hoc limitations on request-line length are found in
430 practice. It is RECOMMENDED that all HTTP senders and recipients
431 support, at a minimum, request-line lengths of 8000 octets.
433 3.1. Method
435 The method token indicates the request method to be performed on the
436 target resource. The request method is case-sensitive.
438 method = token
440 The request methods defined by this specification can be found in
441 Section 9 of [HTTP], along with information regarding the HTTP method
442 registry and considerations for defining new methods.
444 3.2. Request Target
446 The request-target identifies the target resource upon which to apply
447 the request. The client derives a request-target from its desired
448 target URI. There are four distinct formats for the request-target,
449 depending on both the method being requested and whether the request
450 is to a proxy.
452 request-target = origin-form
453 / absolute-form
454 / authority-form
455 / asterisk-form
457 No whitespace is allowed in the request-target. Unfortunately, some
458 user agents fail to properly encode or exclude whitespace found in
459 hypertext references, resulting in those disallowed characters being
460 sent as the request-target in a malformed request-line.
462 Recipients of an invalid request-line SHOULD respond with either a
463 400 (Bad Request) error or a 301 (Moved Permanently) redirect with
464 the request-target properly encoded. A recipient SHOULD NOT attempt
465 to autocorrect and then process the request without a redirect, since
466 the invalid request-line might be deliberately crafted to bypass
467 security filters along the request chain.
469 A client MUST send a Host header field in all HTTP/1.1 request
470 messages. If the target URI includes an authority component, then a
471 client MUST send a field value for Host that is identical to that
472 authority component, excluding any userinfo subcomponent and its "@"
473 delimiter (Section 4.2.1 of [HTTP]). If the authority component is
474 missing or undefined for the target URI, then a client MUST send a
475 Host header field with an empty field value.
477 A server MUST respond with a 400 (Bad Request) status code to any
478 HTTP/1.1 request message that lacks a Host header field and to any
479 request message that contains more than one Host header field line or
480 a Host header field with an invalid field value.
482 3.2.1. origin-form
484 The most common form of request-target is the _origin-form_.
486 origin-form = absolute-path [ "?" query ]
488 When making a request directly to an origin server, other than a
489 CONNECT or server-wide OPTIONS request (as detailed below), a client
490 MUST send only the absolute path and query components of the target
491 URI as the request-target. If the target URI's path component is
492 empty, the client MUST send "/" as the path within the origin-form of
493 request-target. A Host header field is also sent, as defined in
494 Section 7.2 of [HTTP].
496 For example, a client wishing to retrieve a representation of the
497 resource identified as
499 http://www.example.org/where?q=now
501 directly from the origin server would open (or reuse) a TCP
502 connection to port 80 of the host "www.example.org" and send the
503 lines:
505 GET /where?q=now HTTP/1.1
506 Host: www.example.org
508 followed by the remainder of the request message.
510 3.2.2. absolute-form
512 When making a request to a proxy, other than a CONNECT or server-wide
513 OPTIONS request (as detailed below), a client MUST send the target
514 URI in _absolute-form_ as the request-target.
516 absolute-form = absolute-URI
518 The proxy is requested to either service that request from a valid
519 cache, if possible, or make the same request on the client's behalf
520 to either the next inbound proxy server or directly to the origin
521 server indicated by the request-target. Requirements on such
522 "forwarding" of messages are defined in Section 7.6 of [HTTP].
524 An example absolute-form of request-line would be:
526 GET http://www.example.org/pub/WWW/TheProject.html HTTP/1.1
528 A client MUST send a Host header field in an HTTP/1.1 request even if
529 the request-target is in the absolute-form, since this allows the
530 Host information to be forwarded through ancient HTTP/1.0 proxies
531 that might not have implemented Host.
533 When a proxy receives a request with an absolute-form of request-
534 target, the proxy MUST ignore the received Host header field (if any)
535 and instead replace it with the host information of the request-
536 target. A proxy that forwards such a request MUST generate a new
537 Host field value based on the received request-target rather than
538 forward the received Host field value.
540 When an origin server receives a request with an absolute-form of
541 request-target, the origin server MUST ignore the received Host
542 header field (if any) and instead use the host information of the
543 request-target. Note that if the request-target does not have an
544 authority component, an empty Host header field will be sent in this
545 case.
547 A server MUST accept the absolute-form in requests even though most
548 HTTP/1.1 clients will only send the absolute-form to a proxy.
550 3.2.3. authority-form
552 The _authority-form_ of request-target is only used for CONNECT
553 requests (Section 9.3.6 of [HTTP]). It consists of only the uri-host
554 and port number of the tunnel destination, separated by a colon
555 (":").
557 authority-form = uri-host ":" port
559 When making a CONNECT request to establish a tunnel through one or
560 more proxies, a client MUST send only the host and port of the tunnel
561 destination as the request-target. The client obtains the host and
562 port from the target URI's authority component, except that it sends
563 the scheme's default port if the target URI elides the port. For
564 example, a CONNECT request to "http://www.example.com" looks like
566 CONNECT www.example.com:80 HTTP/1.1
567 Host: www.example.com
569 3.2.4. asterisk-form
571 The _asterisk-form_ of request-target is only used for a server-wide
572 OPTIONS request (Section 9.3.7 of [HTTP]).
574 asterisk-form = "*"
576 When a client wishes to request OPTIONS for the server as a whole, as
577 opposed to a specific named resource of that server, the client MUST
578 send only "*" (%x2A) as the request-target. For example,
580 OPTIONS * HTTP/1.1
582 If a proxy receives an OPTIONS request with an absolute-form of
583 request-target in which the URI has an empty path and no query
584 component, then the last proxy on the request chain MUST send a
585 request-target of "*" when it forwards the request to the indicated
586 origin server.
588 For example, the request
590 OPTIONS http://www.example.org:8001 HTTP/1.1
592 would be forwarded by the final proxy as
594 OPTIONS * HTTP/1.1
595 Host: www.example.org:8001
597 after connecting to port 8001 of host "www.example.org".
599 3.3. Reconstructing the Target URI
601 The target URI is the request-target when the request-target is in
602 absolute-form. In that case, a server will parse the URI into its
603 generic components for further evaluation.
605 Otherwise, the server reconstructs the target URI from the connection
606 context and various parts of the request message in order to identify
607 the target resource (Section 7.1 of [HTTP]):
609 * If the server's configuration provides for a fixed URI scheme, or
610 a scheme is provided by a trusted outbound gateway, that scheme is
611 used for the target URI. This is common in large-scale
612 deployments because a gateway server will receive the client's
613 connection context and replace that with their own connection to
614 the inbound server. Otherwise, if the request is received over a
615 secured connection, the target URI's scheme is "https"; if not,
616 the scheme is "http".
618 * If the request-target is in authority-form, the target URI's
619 authority component is the request-target. Otherwise, the target
620 URI's authority component is the field value of the Host header
621 field. If there is no Host header field or if its field value is
622 empty or invalid, the target URI's authority component is empty.
624 * If the request-target is in authority-form or asterisk-form, the
625 target URI's combined path and query component is empty.
626 Otherwise, the target URI's combined path and query component is
627 the request-target.
629 * The components of a reconstructed target URI, once determined as
630 above, can be recombined into absolute-URI form by concatenating
631 the scheme, "://", authority, and combined path and query
632 component.
634 Example 1: the following message received over a secure connection
636 GET /pub/WWW/TheProject.html HTTP/1.1
637 Host: www.example.org
639 has a target URI of
641 https://www.example.org/pub/WWW/TheProject.html
643 Example 2: the following message received over an insecure connection
645 OPTIONS * HTTP/1.1
646 Host: www.example.org:8080
648 has a target URI of
650 http://www.example.org:8080
652 If the target URI's authority component is empty and its URI scheme
653 requires a non-empty authority (as is the case for "http" and
654 "https"), the server can reject the request or determine whether a
655 configured default applies that is consistent with the incoming
656 connection's context. Context might include connection details like
657 address and port, what security has been applied, and locally-defined
658 information specific to that server's configuration. An empty
659 authority is replaced with the configured default before further
660 processing of the request.
662 Supplying a default name for authority within the context of a
663 secured connection is inherently unsafe if there is any chance that
664 the user agent's intended authority might differ from the default. A
665 server that can uniquely identify an authority from the request
666 context MAY use that identity as a default without this risk.
667 Alternatively, it might be better to redirect the request to a safe
668 resource that explains how to obtain a new client.
670 Note that reconstructing the client's target URI is only half of the
671 process for identifying a target resource. The other half is
672 determining whether that target URI identifies a resource for which
673 the server is willing and able to send a response, as defined in
674 Section 7.4 of [HTTP].
676 4. Status Line
678 The first line of a response message is the status-line, consisting
679 of the protocol version, a space (SP), the status code, another
680 space, and ending with an OPTIONAL textual phrase describing the
681 status code.
683 status-line = HTTP-version SP status-code SP [reason-phrase]
685 Although the status-line grammar rule requires that each of the
686 component elements be separated by a single SP octet, recipients MAY
687 instead parse on whitespace-delimited word boundaries and, aside from
688 the line terminator, treat any form of whitespace as the SP separator
689 while ignoring preceding or trailing whitespace; such whitespace
690 includes one or more of the following octets: SP, HTAB, VT (%x0B), FF
691 (%x0C), or bare CR. However, lenient parsing can result in response
692 splitting security vulnerabilities if there are multiple recipients
693 of the message and each has its own unique interpretation of
694 robustness (see Section 11.1).
696 The status-code element is a 3-digit integer code describing the
697 result of the server's attempt to understand and satisfy the client's
698 corresponding request. A recipient parses and interprets the
699 remainder of the response message in light of the semantics defined
700 for that status code, if the status code is recognized by that
701 recipient, or in accordance with the class of that status code when
702 the specific code is unrecognized.
704 status-code = 3DIGIT
706 HTTP's core status codes are defined in Section 15 of [HTTP], along
707 with the classes of status codes, considerations for the definition
708 of new status codes, and the IANA registry for collecting such
709 definitions.
711 The reason-phrase element exists for the sole purpose of providing a
712 textual description associated with the numeric status code, mostly
713 out of deference to earlier Internet application protocols that were
714 more frequently used with interactive text clients.
716 reason-phrase = 1*( HTAB / SP / VCHAR / obs-text )
718 A client SHOULD ignore the reason-phrase content because it is not a
719 reliable channel for information (it might be translated for a given
720 locale, overwritten by intermediaries, or discarded when the message
721 is forwarded via other versions of HTTP). A server MUST send the
722 space that separates status-code from the reason-phrase even when the
723 reason-phrase is absent (i.e., the status-line would end with the
724 three octets SP CR LF).
726 5. Field Syntax
728 Each field line consists of a case-insensitive field name followed by
729 a colon (":"), optional leading whitespace, the field line value, and
730 optional trailing whitespace.
732 field-line = field-name ":" OWS field-value OWS
734 Most HTTP field names and the rules for parsing within field values
735 are defined in Section 6.3 of [HTTP]. This section covers the
736 generic syntax for header field inclusion within, and extraction
737 from, HTTP/1.1 messages.
739 5.1. Field Line Parsing
741 Messages are parsed using a generic algorithm, independent of the
742 individual field names. The contents within a given field line value
743 are not parsed until a later stage of message interpretation (usually
744 after the message's entire field section has been processed).
746 No whitespace is allowed between the field name and colon. In the
747 past, differences in the handling of such whitespace have led to
748 security vulnerabilities in request routing and response handling. A
749 server MUST reject, with a response status code of 400 (Bad Request),
750 any received request message that contains whitespace between a
751 header field name and colon. A proxy MUST remove any such whitespace
752 from a response message before forwarding the message downstream.
754 A field line value might be preceded and/or followed by optional
755 whitespace (OWS); a single SP preceding the field line value is
756 preferred for consistent readability by humans. The field line value
757 does not include that leading or trailing whitespace: OWS occurring
758 before the first non-whitespace octet of the field line value, or
759 after the last non-whitespace octet of the field line value, is
760 excluded by parsers when extracting the field line value from a field
761 line.
763 5.2. Obsolete Line Folding
765 Historically, HTTP/1.x field values could be extended over multiple
766 lines by preceding each extra line with at least one space or
767 horizontal tab (obs-fold). This specification deprecates such line
768 folding except within the message/http media type (Section 10.1).
770 obs-fold = OWS CRLF RWS
771 ; obsolete line folding
773 A sender MUST NOT generate a message that includes line folding
774 (i.e., that has any field line value that contains a match to the
775 obs-fold rule) unless the message is intended for packaging within
776 the message/http media type.
778 A server that receives an obs-fold in a request message that is not
779 within a message/http container MUST either reject the message by
780 sending a 400 (Bad Request), preferably with a representation
781 explaining that obsolete line folding is unacceptable, or replace
782 each received obs-fold with one or more SP octets prior to
783 interpreting the field value or forwarding the message downstream.
785 A proxy or gateway that receives an obs-fold in a response message
786 that is not within a message/http container MUST either discard the
787 message and replace it with a 502 (Bad Gateway) response, preferably
788 with a representation explaining that unacceptable line folding was
789 received, or replace each received obs-fold with one or more SP
790 octets prior to interpreting the field value or forwarding the
791 message downstream.
793 A user agent that receives an obs-fold in a response message that is
794 not within a message/http container MUST replace each received
795 obs-fold with one or more SP octets prior to interpreting the field
796 value.
798 6. Message Body
800 The message body (if any) of an HTTP/1.1 message is used to carry
801 content (Section 6.4 of [HTTP]) for the request or response. The
802 message body is identical to the content unless a transfer coding has
803 been applied, as described in Section 6.1.
805 message-body = *OCTET
807 The rules for determining when a message body is present in an
808 HTTP/1.1 message differ for requests and responses.
810 The presence of a message body in a request is signaled by a
811 Content-Length or Transfer-Encoding header field. Request message
812 framing is independent of method semantics.
814 The presence of a message body in a response depends on both the
815 request method to which it is responding and the response status code
816 (Section 4), and corresponds to when content is allowed; see
817 Section 6.4 of [HTTP].
819 6.1. Transfer-Encoding
821 The Transfer-Encoding header field lists the transfer coding names
822 corresponding to the sequence of transfer codings that have been (or
823 will be) applied to the content in order to form the message body.
824 Transfer codings are defined in Section 7.
826 Transfer-Encoding = #transfer-coding
827 ; defined in [HTTP], Section 10.1.4
829 Transfer-Encoding is analogous to the Content-Transfer-Encoding field
830 of MIME, which was designed to enable safe transport of binary data
831 over a 7-bit transport service ([RFC2045], Section 6). However, safe
832 transport has a different focus for an 8bit-clean transfer protocol.
833 In HTTP's case, Transfer-Encoding is primarily intended to accurately
834 delimit dynamically generated content. It also serves to distinguish
835 encodings that are only applied in transit from the encodings that
836 are a characteristic of the selected representation.
838 A recipient MUST be able to parse the chunked transfer coding
839 (Section 7.1) because it plays a crucial role in framing messages
840 when the content size is not known in advance. A sender MUST NOT
841 apply the chunked transfer coding more than once to a message body
842 (i.e., chunking an already chunked message is not allowed). If any
843 transfer coding other than chunked is applied to a request's content,
844 the sender MUST apply chunked as the final transfer coding to ensure
845 that the message is properly framed. If any transfer coding other
846 than chunked is applied to a response's content, the sender MUST
847 either apply chunked as the final transfer coding or terminate the
848 message by closing the connection.
850 For example,
852 Transfer-Encoding: gzip, chunked
853 indicates that the content has been compressed using the gzip coding
854 and then chunked using the chunked coding while forming the message
855 body.
857 Unlike Content-Encoding (Section 8.4.1 of [HTTP]), Transfer-Encoding
858 is a property of the message, not of the representation, and any
859 recipient along the request/response chain MAY decode the received
860 transfer coding(s) or apply additional transfer coding(s) to the
861 message body, assuming that corresponding changes are made to the
862 Transfer-Encoding field value. Additional information about the
863 encoding parameters can be provided by other header fields not
864 defined by this specification.
866 Transfer-Encoding MAY be sent in a response to a HEAD request or in a
867 304 (Not Modified) response (Section 15.4.5 of [HTTP]) to a GET
868 request, neither of which includes a message body, to indicate that
869 the origin server would have applied a transfer coding to the message
870 body if the request had been an unconditional GET. This indication
871 is not required, however, because any recipient on the response chain
872 (including the origin server) can remove transfer codings when they
873 are not needed.
875 A server MUST NOT send a Transfer-Encoding header field in any
876 response with a status code of 1xx (Informational) or 204 (No
877 Content). A server MUST NOT send a Transfer-Encoding header field in
878 any 2xx (Successful) response to a CONNECT request (Section 9.3.6 of
879 [HTTP]).
881 A server that receives a request message with a transfer coding it
882 does not understand SHOULD respond with 501 (Not Implemented).
884 Transfer-Encoding was added in HTTP/1.1. It is generally assumed
885 that implementations advertising only HTTP/1.0 support will not
886 understand how to process transfer-encoded content, and that an
887 HTTP/1.0 message received with a Transfer-Encoding is likely to have
888 been forwarded without proper handling of the chunked encoding in
889 transit.
891 A client MUST NOT send a request containing Transfer-Encoding unless
892 it knows the server will handle HTTP/1.1 requests (or later minor
893 revisions); such knowledge might be in the form of specific user
894 configuration or by remembering the version of a prior received
895 response. A server MUST NOT send a response containing Transfer-
896 Encoding unless the corresponding request indicates HTTP/1.1 (or
897 later minor revisions).
899 Early implementations of Transfer-Encoding would occasionally send
900 both a chunked encoding for message framing and an estimated Content-
901 Length header field for use by progress bars. This is why Transfer-
902 Encoding is defined as overriding Content-Length, as opposed to them
903 being mutually incompatible. Unfortunately, forwarding such a
904 message can lead to vulnerabilities regarding request smuggling
905 (Section 11.2) or response splitting (Section 11.1) attacks if any
906 downstream recipient fails to parse the message according to this
907 specification, particularly when a downstream recipient only
908 implements HTTP/1.0.
910 A server MAY reject a request that contains both Content-Length and
911 Transfer-Encoding or process such a request in accordance with the
912 Transfer-Encoding alone. Regardless, the server MUST close the
913 connection after responding to such a request to avoid the potential
914 attacks.
916 A server or client that receives an HTTP/1.0 message containing a
917 Transfer-Encoding header field MUST treat the message as if the
918 framing is faulty, even if a Content-Length is present, and close the
919 connection after processing the message. The message sender might
920 have retained a portion of the message, in buffer, that could be
921 misinterpreted by further use of the connection.
923 6.2. Content-Length
925 When a message does not have a Transfer-Encoding header field, a
926 Content-Length header field (Section 8.6 of [HTTP]) can provide the
927 anticipated size, as a decimal number of octets, for potential
928 content. For messages that do include content, the Content-Length
929 field value provides the framing information necessary for
930 determining where the data (and message) ends. For messages that do
931 not include content, the Content-Length indicates the size of the
932 selected representation (Section 8.6 of [HTTP]).
934 A sender MUST NOT send a Content-Length header field in any message
935 that contains a Transfer-Encoding header field.
937 | *Note:* HTTP's use of Content-Length for message framing
938 | differs significantly from the same field's use in MIME, where
939 | it is an optional field used only within the "message/external-
940 | body" media-type.
942 6.3. Message Body Length
944 The length of a message body is determined by one of the following
945 (in order of precedence):
947 1. Any response to a HEAD request and any response with a 1xx
948 (Informational), 204 (No Content), or 304 (Not Modified) status
949 code is always terminated by the first empty line after the
950 header fields, regardless of the header fields present in the
951 message, and thus cannot contain a message body or trailer
952 section.
954 2. Any 2xx (Successful) response to a CONNECT request implies that
955 the connection will become a tunnel immediately after the empty
956 line that concludes the header fields. A client MUST ignore any
957 Content-Length or Transfer-Encoding header fields received in
958 such a message.
960 3. If a message is received with both a Transfer-Encoding and a
961 Content-Length header field, the Transfer-Encoding overrides the
962 Content-Length. Such a message might indicate an attempt to
963 perform request smuggling (Section 11.2) or response splitting
964 (Section 11.1) and ought to be handled as an error. An
965 intermediary that chooses to forward the message MUST first
966 remove the received Content-Length field and process the
967 Transfer-Encoding (as described below) prior to forwarding the
968 message downstream.
970 4. If a Transfer-Encoding header field is present and the chunked
971 transfer coding (Section 7.1) is the final encoding, the message
972 body length is determined by reading and decoding the chunked
973 data until the transfer coding indicates the data is complete.
975 If a Transfer-Encoding header field is present in a response and
976 the chunked transfer coding is not the final encoding, the
977 message body length is determined by reading the connection until
978 it is closed by the server.
980 If a Transfer-Encoding header field is present in a request and
981 the chunked transfer coding is not the final encoding, the
982 message body length cannot be determined reliably; the server
983 MUST respond with the 400 (Bad Request) status code and then
984 close the connection.
986 5. If a message is received without Transfer-Encoding and with an
987 invalid Content-Length header field, then the message framing is
988 invalid and the recipient MUST treat it as an unrecoverable
989 error, unless the field value can be successfully parsed as a
990 comma-separated list (Section 5.6.1 of [HTTP]), all values in the
991 list are valid, and all values in the list are the same (in which
992 case the message is processed with that single value used as the
993 Content-Length field value). If the unrecoverable error is in a
994 request message, the server MUST respond with a 400 (Bad Request)
995 status code and then close the connection. If it is in a
996 response message received by a proxy, the proxy MUST close the
997 connection to the server, discard the received response, and send
998 a 502 (Bad Gateway) response to the client. If it is in a
999 response message received by a user agent, the user agent MUST
1000 close the connection to the server and discard the received
1001 response.
1003 6. If a valid Content-Length header field is present without
1004 Transfer-Encoding, its decimal value defines the expected message
1005 body length in octets. If the sender closes the connection or
1006 the recipient times out before the indicated number of octets are
1007 received, the recipient MUST consider the message to be
1008 incomplete and close the connection.
1010 7. If this is a request message and none of the above are true, then
1011 the message body length is zero (no message body is present).
1013 8. Otherwise, this is a response message without a declared message
1014 body length, so the message body length is determined by the
1015 number of octets received prior to the server closing the
1016 connection.
1018 Since there is no way to distinguish a successfully completed, close-
1019 delimited response message from a partially received message
1020 interrupted by network failure, a server SHOULD generate encoding or
1021 length-delimited messages whenever possible. The close-delimiting
1022 feature exists primarily for backwards compatibility with HTTP/1.0.
1024 | *Note:* Request messages are never close-delimited because they
1025 | are always explicitly framed by length or transfer coding, with
1026 | the absence of both implying the request ends immediately after
1027 | the header section.
1029 A server MAY reject a request that contains a message body but not a
1030 Content-Length by responding with 411 (Length Required).
1032 Unless a transfer coding other than chunked has been applied, a
1033 client that sends a request containing a message body SHOULD use a
1034 valid Content-Length header field if the message body length is known
1035 in advance, rather than the chunked transfer coding, since some
1036 existing services respond to chunked with a 411 (Length Required)
1037 status code even though they understand the chunked transfer coding.
1038 This is typically because such services are implemented via a gateway
1039 that requires a content-length in advance of being called and the
1040 server is unable or unwilling to buffer the entire request before
1041 processing.
1043 A user agent that sends a request that contains a message body MUST
1044 send either a valid Content-Length header field or use the chunked
1045 transfer coding. A client MUST NOT use the chunked transfer encoding
1046 unless it knows the server will handle HTTP/1.1 (or later) requests;
1047 such knowledge can be in the form of specific user configuration or
1048 by remembering the version of a prior received response.
1050 If the final response to the last request on a connection has been
1051 completely received and there remains additional data to read, a user
1052 agent MAY discard the remaining data or attempt to determine if that
1053 data belongs as part of the prior message body, which might be the
1054 case if the prior message's Content-Length value is incorrect. A
1055 client MUST NOT process, cache, or forward such extra data as a
1056 separate response, since such behavior would be vulnerable to cache
1057 poisoning.
1059 7. Transfer Codings
1061 Transfer coding names are used to indicate an encoding transformation
1062 that has been, can be, or might need to be applied to a message's
1063 content in order to ensure "safe transport" through the network.
1064 This differs from a content coding in that the transfer coding is a
1065 property of the message rather than a property of the representation
1066 that is being transferred.
1068 All transfer-coding names are case-insensitive and ought to be
1069 registered within the HTTP Transfer Coding registry, as defined in
1070 Section 7.3. They are used in the Transfer-Encoding (Section 6.1)
1071 and TE (Section 10.1.4 of [HTTP]) header fields (the latter also
1072 defining the "transfer-coding" grammar).
1074 7.1. Chunked Transfer Coding
1076 The chunked transfer coding wraps content in order to transfer it as
1077 a series of chunks, each with its own size indicator, followed by an
1078 OPTIONAL trailer section containing trailer fields. Chunked enables
1079 content streams of unknown size to be transferred as a sequence of
1080 length-delimited buffers, which enables the sender to retain
1081 connection persistence and the recipient to know when it has received
1082 the entire message.
1084 chunked-body = *chunk
1085 last-chunk
1086 trailer-section
1087 CRLF
1089 chunk = chunk-size [ chunk-ext ] CRLF
1090 chunk-data CRLF
1091 chunk-size = 1*HEXDIG
1092 last-chunk = 1*("0") [ chunk-ext ] CRLF
1094 chunk-data = 1*OCTET ; a sequence of chunk-size octets
1096 The chunk-size field is a string of hex digits indicating the size of
1097 the chunk-data in octets. The chunked transfer coding is complete
1098 when a chunk with a chunk-size of zero is received, possibly followed
1099 by a trailer section, and finally terminated by an empty line.
1101 A recipient MUST be able to parse and decode the chunked transfer
1102 coding.
1104 HTTP/1.1 does not define any means to limit the size of a chunked
1105 response such that an intermediary can be assured of buffering the
1106 entire response. Additionally, very large chunk sizes may cause
1107 overflows or loss of precision if their values are not represented
1108 accurately in a receiving implementation. Therefore, recipients MUST
1109 anticipate potentially large hexadecimal numerals and prevent parsing
1110 errors due to integer conversion overflows or precision loss due to
1111 integer representation.
1113 The chunked encoding does not define any parameters. Their presence
1114 SHOULD be treated as an error.
1116 7.1.1. Chunk Extensions
1118 The chunked encoding allows each chunk to include zero or more chunk
1119 extensions, immediately following the chunk-size, for the sake of
1120 supplying per-chunk metadata (such as a signature or hash), mid-
1121 message control information, or randomization of message body size.
1123 chunk-ext = *( BWS ";" BWS chunk-ext-name
1124 [ BWS "=" BWS chunk-ext-val ] )
1126 chunk-ext-name = token
1127 chunk-ext-val = token / quoted-string
1129 The chunked encoding is specific to each connection and is likely to
1130 be removed or recoded by each recipient (including intermediaries)
1131 before any higher-level application would have a chance to inspect
1132 the extensions. Hence, use of chunk extensions is generally limited
1133 to specialized HTTP services such as "long polling" (where client and
1134 server can have shared expectations regarding the use of chunk
1135 extensions) or for padding within an end-to-end secured connection.
1137 A recipient MUST ignore unrecognized chunk extensions. A server
1138 ought to limit the total length of chunk extensions received in a
1139 request to an amount reasonable for the services provided, in the
1140 same way that it applies length limitations and timeouts for other
1141 parts of a message, and generate an appropriate 4xx (Client Error)
1142 response if that amount is exceeded.
1144 7.1.2. Chunked Trailer Section
1146 A trailer section allows the sender to include additional fields at
1147 the end of a chunked message in order to supply metadata that might
1148 be dynamically generated while the content is sent, such as a message
1149 integrity check, digital signature, or post-processing status. The
1150 proper use and limitations of trailer fields are defined in
1151 Section 6.5 of [HTTP].
1153 trailer-section = *( field-line CRLF )
1155 A recipient that decodes and removes the chunked encoding from a
1156 message (e.g., for storage or forwarding to a non-HTTP/1.1 peer) MUST
1157 discard any received trailer fields, store/forward them separately
1158 from the header fields, or selectively merge into the header section
1159 only those trailer fields corresponding to header field definitions
1160 that are understood by the recipient to explicitly permit and define
1161 how their corresponding trailer field value can be safely merged.
1163 7.1.3. Decoding Chunked
1165 A process for decoding the chunked transfer coding can be represented
1166 in pseudo-code as:
1168 length := 0
1169 read chunk-size, chunk-ext (if any), and CRLF
1170 while (chunk-size > 0) {
1171 read chunk-data and CRLF
1172 append chunk-data to content
1173 length := length + chunk-size
1174 read chunk-size, chunk-ext (if any), and CRLF
1175 }
1176 read trailer field
1177 while (trailer field is not empty) {
1178 if (trailer fields are stored/forwarded separately) {
1179 append trailer field to existing trailer fields
1180 }
1181 else if (trailer field is understood and defined as mergeable) {
1182 merge trailer field with existing header fields
1183 }
1184 else {
1185 discard trailer field
1186 }
1187 read trailer field
1188 }
1189 Content-Length := length
1190 Remove "chunked" from Transfer-Encoding
1192 7.2. Transfer Codings for Compression
1194 The following transfer coding names for compression are defined by
1195 the same algorithm as their corresponding content coding:
1197 compress (and x-compress)
1198 See Section 8.4.1.1 of [HTTP].
1200 deflate
1201 See Section 8.4.1.2 of [HTTP].
1203 gzip (and x-gzip)
1204 See Section 8.4.1.3 of [HTTP].
1206 The compression codings do not define any parameters. The presence
1207 of parameters with any of these compression codings SHOULD be treated
1208 as an error.
1210 7.3. Transfer Coding Registry
1212 The "HTTP Transfer Coding Registry" defines the namespace for
1213 transfer coding names. It is maintained at
1214 .
1216 Registrations MUST include the following fields:
1218 * Name
1220 * Description
1222 * Pointer to specification text
1224 Names of transfer codings MUST NOT overlap with names of content
1225 codings (Section 8.4.1 of [HTTP]) unless the encoding transformation
1226 is identical, as is the case for the compression codings defined in
1227 Section 7.2.
1229 The TE header field (Section 10.1.4 of [HTTP]) uses a pseudo
1230 parameter named "q" as rank value when multiple transfer codings are
1231 acceptable. Future registrations of transfer codings SHOULD NOT
1232 define parameters called "q" (case-insensitively) in order to avoid
1233 ambiguities.
1235 Values to be added to this namespace require IETF Review (see
1236 Section 4.8 of [RFC8126]), and MUST conform to the purpose of
1237 transfer coding defined in this specification.
1239 Use of program names for the identification of encoding formats is
1240 not desirable and is discouraged for future encodings.
1242 7.4. Negotiating Transfer Codings
1244 The TE field (Section 10.1.4 of [HTTP]) is used in HTTP/1.1 to
1245 indicate what transfer-codings, besides chunked, the client is
1246 willing to accept in the response, and whether the client is willing
1247 to preserve trailer fields in a chunked transfer coding.
1249 A client MUST NOT send the chunked transfer coding name in TE;
1250 chunked is always acceptable for HTTP/1.1 recipients.
1252 Three examples of TE use are below.
1254 TE: deflate
1255 TE:
1256 TE: trailers, deflate;q=0.5
1258 When multiple transfer codings are acceptable, the client MAY rank
1259 the codings by preference using a case-insensitive "q" parameter
1260 (similar to the qvalues used in content negotiation fields,
1261 Section 12.4.2 of [HTTP]). The rank value is a real number in the
1262 range 0 through 1, where 0.001 is the least preferred and 1 is the
1263 most preferred; a value of 0 means "not acceptable".
1265 If the TE field value is empty or if no TE field is present, the only
1266 acceptable transfer coding is chunked. A message with no transfer
1267 coding is always acceptable.
1269 The keyword "trailers" indicates that the sender will not discard
1270 trailer fields, as described in Section 6.5 of [HTTP].
1272 Since the TE header field only applies to the immediate connection, a
1273 sender of TE MUST also send a "TE" connection option within the
1274 Connection header field (Section 7.6.1 of [HTTP]) in order to prevent
1275 the TE header field from being forwarded by intermediaries that do
1276 not support its semantics.
1278 8. Handling Incomplete Messages
1280 A server that receives an incomplete request message, usually due to
1281 a canceled request or a triggered timeout exception, MAY send an
1282 error response prior to closing the connection.
1284 A client that receives an incomplete response message, which can
1285 occur when a connection is closed prematurely or when decoding a
1286 supposedly chunked transfer coding fails, MUST record the message as
1287 incomplete. Cache requirements for incomplete responses are defined
1288 in Section 3 of [CACHING].
1290 If a response terminates in the middle of the header section (before
1291 the empty line is received) and the status code might rely on header
1292 fields to convey the full meaning of the response, then the client
1293 cannot assume that meaning has been conveyed; the client might need
1294 to repeat the request in order to determine what action to take next.
1296 A message body that uses the chunked transfer coding is incomplete if
1297 the zero-sized chunk that terminates the encoding has not been
1298 received. A message that uses a valid Content-Length is incomplete
1299 if the size of the message body received (in octets) is less than the
1300 value given by Content-Length. A response that has neither chunked
1301 transfer coding nor Content-Length is terminated by closure of the
1302 connection and, if the header section was received intact, is
1303 considered complete unless an error was indicated by the underlying
1304 connection (e.g., an "incomplete close" in TLS would leave the
1305 response incomplete, as described in Section 9.8).
1307 9. Connection Management
1309 HTTP messaging is independent of the underlying transport- or
1310 session-layer connection protocol(s). HTTP only presumes a reliable
1311 transport with in-order delivery of requests and the corresponding
1312 in-order delivery of responses. The mapping of HTTP request and
1313 response structures onto the data units of an underlying transport
1314 protocol is outside the scope of this specification.
1316 As described in Section 7.3 of [HTTP], the specific connection
1317 protocols to be used for an HTTP interaction are determined by client
1318 configuration and the target URI. For example, the "http" URI scheme
1319 (Section 4.2.1 of [HTTP]) indicates a default connection of TCP over
1320 IP, with a default TCP port of 80, but the client might be configured
1321 to use a proxy via some other connection, port, or protocol.
1323 HTTP implementations are expected to engage in connection management,
1324 which includes maintaining the state of current connections,
1325 establishing a new connection or reusing an existing connection,
1326 processing messages received on a connection, detecting connection
1327 failures, and closing each connection. Most clients maintain
1328 multiple connections in parallel, including more than one connection
1329 per server endpoint. Most servers are designed to maintain thousands
1330 of concurrent connections, while controlling request queues to enable
1331 fair use and detect denial-of-service attacks.
1333 9.1. Establishment
1335 It is beyond the scope of this specification to describe how
1336 connections are established via various transport- or session-layer
1337 protocols. Each HTTP connection maps to one underlying transport
1338 connection.
1340 9.2. Associating a Response to a Request
1342 HTTP/1.1 does not include a request identifier for associating a
1343 given request message with its corresponding one or more response
1344 messages. Hence, it relies on the order of response arrival to
1345 correspond exactly to the order in which requests are made on the
1346 same connection. More than one response message per request only
1347 occurs when one or more informational responses (1xx, see
1348 Section 15.2 of [HTTP]) precede a final response to the same request.
1350 A client that has more than one outstanding request on a connection
1351 MUST maintain a list of outstanding requests in the order sent and
1352 MUST associate each received response message on that connection to
1353 the first outstanding request that has not yet received a final (non-
1354 1xx) response.
1356 If a client receives data on a connection that doesn't have
1357 outstanding requests, the client MUST NOT consider that data to be a
1358 valid response; the client SHOULD close the connection, since message
1359 delimitation is now ambiguous, unless the data consists only of one
1360 or more CRLF (which can be discarded, as per Section 2.2).
1362 9.3. Persistence
1364 HTTP/1.1 defaults to the use of _persistent connections_, allowing
1365 multiple requests and responses to be carried over a single
1366 connection. HTTP implementations SHOULD support persistent
1367 connections.
1369 A recipient determines whether a connection is persistent or not
1370 based on the protocol version and Connection header field
1371 (Section 7.6.1 of [HTTP]) in the most recently received message, if
1372 any:
1374 * If the close connection option is present (Section 9.6), the
1375 connection will not persist after the current response; else,
1377 * If the received protocol is HTTP/1.1 (or later), the connection
1378 will persist after the current response; else,
1380 * If the received protocol is HTTP/1.0, the "keep-alive" connection
1381 option is present, either the recipient is not a proxy or the
1382 message is a response, and the recipient wishes to honor the
1383 HTTP/1.0 "keep-alive" mechanism, the connection will persist after
1384 the current response; otherwise,
1386 * The connection will close after the current response.
1388 A client that does not support persistent connections MUST send the
1389 close connection option in every request message.
1391 A server that does not support persistent connections MUST send the
1392 close connection option in every response message that does not have
1393 a 1xx (Informational) status code.
1395 A client MAY send additional requests on a persistent connection
1396 until it sends or receives a close connection option or receives an
1397 HTTP/1.0 response without a "keep-alive" connection option.
1399 In order to remain persistent, all messages on a connection need to
1400 have a self-defined message length (i.e., one not defined by closure
1401 of the connection), as described in Section 6. A server MUST read
1402 the entire request message body or close the connection after sending
1403 its response, since otherwise the remaining data on a persistent
1404 connection would be misinterpreted as the next request. Likewise, a
1405 client MUST read the entire response message body if it intends to
1406 reuse the same connection for a subsequent request.
1408 A proxy server MUST NOT maintain a persistent connection with an
1409 HTTP/1.0 client (see Section 19.7.1 of [RFC2068] for information and
1410 discussion of the problems with the Keep-Alive header field
1411 implemented by many HTTP/1.0 clients).
1413 See Appendix C.2.2 for more information on backwards compatibility
1414 with HTTP/1.0 clients.
1416 9.3.1. Retrying Requests
1418 Connections can be closed at any time, with or without intention.
1419 Implementations ought to anticipate the need to recover from
1420 asynchronous close events. The conditions under which a client can
1421 automatically retry a sequence of outstanding requests are defined in
1422 Section 9.2.2 of [HTTP].
1424 9.3.2. Pipelining
1426 A client that supports persistent connections MAY _pipeline_ its
1427 requests (i.e., send multiple requests without waiting for each
1428 response). A server MAY process a sequence of pipelined requests in
1429 parallel if they all have safe methods (Section 9.2.1 of [HTTP]), but
1430 it MUST send the corresponding responses in the same order that the
1431 requests were received.
1433 A client that pipelines requests SHOULD retry unanswered requests if
1434 the connection closes before it receives all of the corresponding
1435 responses. When retrying pipelined requests after a failed
1436 connection (a connection not explicitly closed by the server in its
1437 last complete response), a client MUST NOT pipeline immediately after
1438 connection establishment, since the first remaining request in the
1439 prior pipeline might have caused an error response that can be lost
1440 again if multiple requests are sent on a prematurely closed
1441 connection (see the TCP reset problem described in Section 9.6).
1443 Idempotent methods (Section 9.2.2 of [HTTP]) are significant to
1444 pipelining because they can be automatically retried after a
1445 connection failure. A user agent SHOULD NOT pipeline requests after
1446 a non-idempotent method, until the final response status code for
1447 that method has been received, unless the user agent has a means to
1448 detect and recover from partial failure conditions involving the
1449 pipelined sequence.
1451 An intermediary that receives pipelined requests MAY pipeline those
1452 requests when forwarding them inbound, since it can rely on the
1453 outbound user agent(s) to determine what requests can be safely
1454 pipelined. If the inbound connection fails before receiving a
1455 response, the pipelining intermediary MAY attempt to retry a sequence
1456 of requests that have yet to receive a response if the requests all
1457 have idempotent methods; otherwise, the pipelining intermediary
1458 SHOULD forward any received responses and then close the
1459 corresponding outbound connection(s) so that the outbound user
1460 agent(s) can recover accordingly.
1462 9.4. Concurrency
1464 A client ought to limit the number of simultaneous open connections
1465 that it maintains to a given server.
1467 Previous revisions of HTTP gave a specific number of connections as a
1468 ceiling, but this was found to be impractical for many applications.
1469 As a result, this specification does not mandate a particular maximum
1470 number of connections but, instead, encourages clients to be
1471 conservative when opening multiple connections.
1473 Multiple connections are typically used to avoid the "head-of-line
1474 blocking" problem, wherein a request that takes significant server-
1475 side processing and/or transfers very large content would block
1476 subsequent requests on the same connection. However, each connection
1477 consumes server resources.
1479 Furthermore, using multiple connections can cause undesirable side
1480 effects in congested networks. Using larger numbers of connections
1481 can also cause side effects in otherwise uncongested networks,
1482 because their aggregate and initially synchronized sending behavior
1483 can cause congestion that would not have been present if fewer
1484 parallel connections had been used.
1486 Note that a server might reject traffic that it deems abusive or
1487 characteristic of a denial-of-service attack, such as an excessive
1488 number of open connections from a single client.
1490 9.5. Failures and Timeouts
1492 Servers will usually have some timeout value beyond which they will
1493 no longer maintain an inactive connection. Proxy servers might make
1494 this a higher value since it is likely that the client will be making
1495 more connections through the same proxy server. The use of
1496 persistent connections places no requirements on the length (or
1497 existence) of this timeout for either the client or the server.
1499 A client or server that wishes to time out SHOULD issue a graceful
1500 close on the connection. Implementations SHOULD constantly monitor
1501 open connections for a received closure signal and respond to it as
1502 appropriate, since prompt closure of both sides of a connection
1503 enables allocated system resources to be reclaimed.
1505 A client, server, or proxy MAY close the transport connection at any
1506 time. For example, a client might have started to send a new request
1507 at the same time that the server has decided to close the "idle"
1508 connection. From the server's point of view, the connection is being
1509 closed while it was idle, but from the client's point of view, a
1510 request is in progress.
1512 A server SHOULD sustain persistent connections, when possible, and
1513 allow the underlying transport's flow-control mechanisms to resolve
1514 temporary overloads, rather than terminate connections with the
1515 expectation that clients will retry. The latter technique can
1516 exacerbate network congestion or server load.
1518 A client sending a message body SHOULD monitor the network connection
1519 for an error response while it is transmitting the request. If the
1520 client sees a response that indicates the server does not wish to
1521 receive the message body and is closing the connection, the client
1522 SHOULD immediately cease transmitting the body and close its side of
1523 the connection.
1525 9.6. Tear-down
1527 The "close" connection option is defined as a signal that the sender
1528 will close this connection after completion of the response. A
1529 sender SHOULD send a Connection header field (Section 7.6.1 of
1530 [HTTP]) containing the close connection option when it intends to
1531 close a connection. For example,
1533 Connection: close
1535 as a request header field indicates that this is the last request
1536 that the client will send on this connection, while in a response the
1537 same field indicates that the server is going to close this
1538 connection after the response message is complete.
1540 Note that the field name "Close" is reserved, since using that name
1541 as a header field might conflict with the close connection option.
1543 A client that sends a close connection option MUST NOT send further
1544 requests on that connection (after the one containing the close) and
1545 MUST close the connection after reading the final response message
1546 corresponding to this request.
1548 A server that receives a close connection option MUST initiate
1549 closure of the connection (see below) after it sends the final
1550 response to the request that contained the close connection option.
1551 The server SHOULD send a close connection option in its final
1552 response on that connection. The server MUST NOT process any further
1553 requests received on that connection.
1555 A server that sends a close connection option MUST initiate closure
1556 of the connection (see below) after it sends the response containing
1557 the close connection option. The server MUST NOT process any further
1558 requests received on that connection.
1560 A client that receives a close connection option MUST cease sending
1561 requests on that connection and close the connection after reading
1562 the response message containing the close connection option; if
1563 additional pipelined requests had been sent on the connection, the
1564 client SHOULD NOT assume that they will be processed by the server.
1566 If a server performs an immediate close of a TCP connection, there is
1567 a significant risk that the client will not be able to read the last
1568 HTTP response. If the server receives additional data from the
1569 client on a fully closed connection, such as another request sent by
1570 the client before receiving the server's response, the server's TCP
1571 stack will send a reset packet to the client; unfortunately, the
1572 reset packet might erase the client's unacknowledged input buffers
1573 before they can be read and interpreted by the client's HTTP parser.
1575 To avoid the TCP reset problem, servers typically close a connection
1576 in stages. First, the server performs a half-close by closing only
1577 the write side of the read/write connection. The server then
1578 continues to read from the connection until it receives a
1579 corresponding close by the client, or until the server is reasonably
1580 certain that its own TCP stack has received the client's
1581 acknowledgement of the packet(s) containing the server's last
1582 response. Finally, the server fully closes the connection.
1584 It is unknown whether the reset problem is exclusive to TCP or might
1585 also be found in other transport connection protocols.
1587 Note that a TCP connection that is half-closed by the client does not
1588 delimit a request message, nor does it imply that the client is no
1589 longer interested in a response. In general, transport signals
1590 cannot be relied upon to signal edge cases, since HTTP/1.1 is
1591 independent of transport.
1593 9.7. TLS Connection Initiation
1595 Conceptually, HTTP/TLS is simply sending HTTP messages over a
1596 connection secured via TLS [TLS13].
1598 The HTTP client also acts as the TLS client. It initiates a
1599 connection to the server on the appropriate port and sends the TLS
1600 ClientHello to begin the TLS handshake. When the TLS handshake has
1601 finished, the client may then initiate the first HTTP request. All
1602 HTTP data MUST be sent as TLS "application data", but is otherwise
1603 treated like a normal connection for HTTP (including potential reuse
1604 as a persistent connection).
1606 9.8. TLS Connection Closure
1608 TLS provides a facility for secure connection closure through an
1609 exchange of closure alerts prior to closing a connection [TLS13].
1610 When a valid closure alert is received, an implementation can be
1611 assured that no further data will be received on that connection.
1613 When an implementation knows that it has sent or received all the
1614 message data that it cares about, typically by detecting HTTP message
1615 boundaries, it might generate an "incomplete close" by sending a
1616 closure alert and then closing the connection without waiting to
1617 receive the corresponding closure alert from its peer.
1619 An incomplete close does not call into question the security of the
1620 data already received, but it could indicate that subsequent data
1621 might have been truncated. As TLS is not directly aware of HTTP
1622 message framing, it is necessary to examine the HTTP data itself to
1623 determine whether messages were complete. Handling of incomplete
1624 messages is defined in Section 8.
1626 When encountering an incomplete close, a client SHOULD treat as
1627 completed all requests for which it has received as much data as
1628 specified in the Content-Length header or, when a Transfer-Encoding
1629 of chunked is used, for which the terminal zero-length chunk has been
1630 received. A response that has neither chunked transfer coding nor
1631 Content-Length is complete only if a valid closure alert has been
1632 received. Treating an incomplete message as complete could expose
1633 implementations to attack.
1635 A client detecting an incomplete close SHOULD recover gracefully.
1637 Clients MUST send a closure alert before closing the connection.
1638 Clients that do not expect to receive any more data MAY choose not to
1639 wait for the server's closure alert and simply close the connection,
1640 thus generating an incomplete close on the server side.
1642 Servers SHOULD be prepared to receive an incomplete close from the
1643 client, since the client can often determine when the end of server
1644 data is.
1646 Servers MUST attempt to initiate an exchange of closure alerts with
1647 the client before closing the connection. Servers MAY close the
1648 connection after sending the closure alert, thus generating an
1649 incomplete close on the client side.
1651 10. Enclosing Messages as Data
1653 10.1. Media Type message/http
1655 The message/http media type can be used to enclose a single HTTP
1656 request or response message, provided that it obeys the MIME
1657 restrictions for all "message" types regarding line length and
1658 encodings. Because of the line length limitations, field values
1659 within message/http are allowed to use line folding (obs-fold), as
1660 described in Section 5.2, to convey the field value over multiple
1661 lines. A recipient of message/http data MUST replace any obsolete
1662 line folding with one or more SP characters when the message is
1663 consumed.
1665 Type name: message
1667 Subtype name: http
1669 Required parameters: N/A
1671 Optional parameters: version, msgtype
1673 version: The HTTP-version number of the enclosed message (e.g.,
1674 "1.1"). If not present, the version can be determined from the
1675 first line of the body.
1677 msgtype: The message type - "request" or "response". If not
1678 present, the type can be determined from the first line of the
1679 body.
1681 Encoding considerations: only "7bit", "8bit", or "binary" are
1682 permitted
1684 Security considerations: see Section 11
1686 Interoperability considerations: N/A
1688 Published specification: This specification (see Section 10.1).
1690 Applications that use this media type: N/A
1692 Fragment identifier considerations: N/A
1694 Additional information: Magic number(s): N/A
1696 Deprecated alias names for this type: N/A
1698 File extension(s): N/A
1700 Macintosh file type code(s): N/A
1702 Person and email address to contact for further information: See Aut
1703 hors' Addresses section.
1705 Intended usage: COMMON
1707 Restrictions on usage: N/A
1709 Author: See Authors' Addresses section.
1711 Change controller: IESG
1713 10.2. Media Type application/http
1715 The application/http media type can be used to enclose a pipeline of
1716 one or more HTTP request or response messages (not intermixed).
1718 Type name: application
1720 Subtype name: http
1722 Required parameters: N/A
1724 Optional parameters: version, msgtype
1726 version: The HTTP-version number of the enclosed messages (e.g.,
1727 "1.1"). If not present, the version can be determined from the
1728 first line of the body.
1730 msgtype: The message type - "request" or "response". If not
1731 present, the type can be determined from the first line of the
1732 body.
1734 Encoding considerations: HTTP messages enclosed by this type are in
1735 "binary" format; use of an appropriate Content-Transfer-Encoding
1736 is required when transmitted via email.
1738 Security considerations: see Section 11
1740 Interoperability considerations: N/A
1742 Published specification: This specification (see Section 10.2).
1744 Applications that use this media type: N/A
1746 Fragment identifier considerations: N/A
1748 Additional information: Deprecated alias names for this type: N/A
1750 Magic number(s): N/A
1752 File extension(s): N/A
1754 Macintosh file type code(s): N/A
1756 Person and email address to contact for further information: See Aut
1757 hors' Addresses section.
1759 Intended usage: COMMON
1761 Restrictions on usage: N/A
1763 Author: See Authors' Addresses section.
1765 Change controller: IESG
1767 11. Security Considerations
1769 This section is meant to inform developers, information providers,
1770 and users about known security considerations relevant to HTTP
1771 message syntax and parsing. Security considerations about HTTP
1772 semantics, content, and routing are addressed in [HTTP].
1774 11.1. Response Splitting
1776 Response splitting (a.k.a., CRLF injection) is a common technique,
1777 used in various attacks on Web usage, that exploits the line-based
1778 nature of HTTP message framing and the ordered association of
1779 requests to responses on persistent connections [Klein]. This
1780 technique can be particularly damaging when the requests pass through
1781 a shared cache.
1783 Response splitting exploits a vulnerability in servers (usually
1784 within an application server) where an attacker can send encoded data
1785 within some parameter of the request that is later decoded and echoed
1786 within any of the response header fields of the response. If the
1787 decoded data is crafted to look like the response has ended and a
1788 subsequent response has begun, the response has been split and the
1789 content within the apparent second response is controlled by the
1790 attacker. The attacker can then make any other request on the same
1791 persistent connection and trick the recipients (including
1792 intermediaries) into believing that the second half of the split is
1793 an authoritative answer to the second request.
1795 For example, a parameter within the request-target might be read by
1796 an application server and reused within a redirect, resulting in the
1797 same parameter being echoed in the Location header field of the
1798 response. If the parameter is decoded by the application and not
1799 properly encoded when placed in the response field, the attacker can
1800 send encoded CRLF octets and other content that will make the
1801 application's single response look like two or more responses.
1803 A common defense against response splitting is to filter requests for
1804 data that looks like encoded CR and LF (e.g., "%0D" and "%0A").
1805 However, that assumes the application server is only performing URI
1806 decoding, rather than more obscure data transformations like charset
1807 transcoding, XML entity translation, base64 decoding, sprintf
1808 reformatting, etc. A more effective mitigation is to prevent
1809 anything other than the server's core protocol libraries from sending
1810 a CR or LF within the header section, which means restricting the
1811 output of header fields to APIs that filter for bad octets and not
1812 allowing application servers to write directly to the protocol
1813 stream.
1815 11.2. Request Smuggling
1817 Request smuggling ([Linhart]) is a technique that exploits
1818 differences in protocol parsing among various recipients to hide
1819 additional requests (which might otherwise be blocked or disabled by
1820 policy) within an apparently harmless request. Like response
1821 splitting, request smuggling can lead to a variety of attacks on HTTP
1822 usage.
1824 This specification has introduced new requirements on request
1825 parsing, particularly with regard to message framing in Section 6.3,
1826 to reduce the effectiveness of request smuggling.
1828 11.3. Message Integrity
1830 HTTP does not define a specific mechanism for ensuring message
1831 integrity, instead relying on the error-detection ability of
1832 underlying transport protocols and the use of length or chunk-
1833 delimited framing to detect completeness. Historically, the lack of
1834 a single integrity mechanism has been justified by the informal
1835 nature of most HTTP communication. However, the prevalence of HTTP
1836 as an information access mechanism has resulted in its increasing use
1837 within environments where verification of message integrity is
1838 crucial.
1840 The mechanisms provided with the "https" scheme, such as
1841 authenticated encryption, provide protection against modification of
1842 messages. Care is needed however to ensure that connection closure
1843 cannot be used to truncate messages (see Section 9.8). User agents
1844 might refuse to accept incomplete messages or treat them specially.
1845 For example, a browser being used to view medical history or drug
1846 interaction information needs to indicate to the user when such
1847 information is detected by the protocol to be incomplete, expired, or
1848 corrupted during transfer. Such mechanisms might be selectively
1849 enabled via user agent extensions or the presence of message
1850 integrity metadata in a response.
1852 The "http" scheme provides no protection against accidental or
1853 malicious modification of messages.
1855 Extensions to the protocol might be used to mitigate the risk of
1856 unwanted modification of messages by intermediaries, even when the
1857 "https" scheme is used. Integrity might be assured by using message
1858 authentication codes or digital signatures that are selectively added
1859 to messages via extensible metadata fields.
1861 11.4. Message Confidentiality
1863 HTTP relies on underlying transport protocols to provide message
1864 confidentiality when that is desired. HTTP has been specifically
1865 designed to be independent of the transport protocol, such that it
1866 can be used over many forms of encrypted connection, with the
1867 selection of such transports being identified by the choice of URI
1868 scheme or within user agent configuration.
1870 The "https" scheme can be used to identify resources that require a
1871 confidential connection, as described in Section 4.2.2 of [HTTP].
1873 12. IANA Considerations
1875 The change controller for the following registrations is: "IETF
1876 (iesg@ietf.org) - Internet Engineering Task Force".
1878 12.1. Field Name Registration
1880 First, introduce the new "Hypertext Transfer Protocol (HTTP) Field
1881 Name Registry" at as
1882 described in Section 18.4 of [HTTP].
1884 Then, please update the registry with the field names listed in the
1885 table below:
1887 +===================+==========+======+============+
1888 | Field Name | Status | Ref. | Comments |
1889 +===================+==========+======+============+
1890 | Close | standard | 9.6 | (reserved) |
1891 +-------------------+----------+------+------------+
1892 | MIME-Version | standard | B.1 | |
1893 +-------------------+----------+------+------------+
1894 | Transfer-Encoding | standard | 6.1 | |
1895 +-------------------+----------+------+------------+
1897 Table 1
1899 12.2. Media Type Registration
1901 Please update the "Media Types" registry at
1902 with the registration
1903 information in Section 10.1 and Section 10.2 for the media types
1904 "message/http" and "application/http", respectively.
1906 12.3. Transfer Coding Registration
1908 Please update the "HTTP Transfer Coding Registry" at
1909 with the
1910 registration procedure of Section 7.3 and the content coding names
1911 summarized in the table below.
1913 +============+===============================+===========+
1914 | Name | Description | Reference |
1915 +============+===============================+===========+
1916 | chunked | Transfer in a series of | Section |
1917 | | chunks | 7.1 |
1918 +------------+-------------------------------+-----------+
1919 | compress | UNIX "compress" data format | Section |
1920 | | [Welch] | 7.2 |
1921 +------------+-------------------------------+-----------+
1922 | deflate | "deflate" compressed data | Section |
1923 | | ([RFC1951]) inside the "zlib" | 7.2 |
1924 | | data format ([RFC1950]) | |
1925 +------------+-------------------------------+-----------+
1926 | gzip | GZIP file format [RFC1952] | Section |
1927 | | | 7.2 |
1928 +------------+-------------------------------+-----------+
1929 | trailers | (reserved) | Section |
1930 | | | 12.3 |
1931 +------------+-------------------------------+-----------+
1932 | x-compress | Deprecated (alias for | Section |
1933 | | compress) | 7.2 |
1934 +------------+-------------------------------+-----------+
1935 | x-gzip | Deprecated (alias for gzip) | Section |
1936 | | | 7.2 |
1937 +------------+-------------------------------+-----------+
1939 Table 2
1941 | *Note:* the coding name "trailers" is reserved because its use
1942 | would conflict with the keyword "trailers" in the TE header
1943 | field (Section 10.1.4 of [HTTP]).
1945 12.4. ALPN Protocol ID Registration
1947 Please update the "TLS Application-Layer Protocol Negotiation (ALPN)
1948 Protocol IDs" registry at with the
1950 registration below:
1952 +==========+=============================+================+
1953 | Protocol | Identification Sequence | Reference |
1954 +==========+=============================+================+
1955 | HTTP/1.1 | 0x68 0x74 0x74 0x70 0x2f | (this |
1956 | | 0x31 0x2e 0x31 ("http/1.1") | specification) |
1957 +----------+-----------------------------+----------------+
1959 Table 3
1961 13. References
1963 13.1. Normative References
1965 [CACHING] Fielding, R., Ed., Nottingham, M., Ed., and J. Reschke,
1966 Ed., "HTTP Caching", Work in Progress, Internet-Draft,
1967 draft-ietf-httpbis-cache-18, 18 August 2021,
1968 .
1971 [HTTP] Fielding, R., Ed., Nottingham, M., Ed., and J. Reschke,
1972 Ed., "HTTP Semantics", Work in Progress, Internet-Draft,
1973 draft-ietf-httpbis-semantics-18, 18 August 2021,
1974 .
1977 [RFC1950] Deutsch, L.P. and J-L. Gailly, "ZLIB Compressed Data
1978 Format Specification version 3.3", RFC 1950,
1979 DOI 10.17487/RFC1950, May 1996,
1980 .
1982 [RFC1951] Deutsch, P., "DEFLATE Compressed Data Format Specification
1983 version 1.3", RFC 1951, DOI 10.17487/RFC1951, May 1996,
1984 .
1986 [RFC1952] Deutsch, P., Gailly, J-L., Adler, M., Deutsch, L.P., and
1987 G. Randers-Pehrson, "GZIP file format specification
1988 version 4.3", RFC 1952, DOI 10.17487/RFC1952, May 1996,
1989 .
1991 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
1992 Requirement Levels", BCP 14, RFC 2119,
1993 DOI 10.17487/RFC2119, March 1997,
1994 .
1996 [RFC5234] Crocker, D., Ed. and P. Overell, "Augmented BNF for Syntax
1997 Specifications: ABNF", STD 68, RFC 5234,
1998 DOI 10.17487/RFC5234, January 2008,
1999 .
2001 [RFC7405] Kyzivat, P., "Case-Sensitive String Support in ABNF",
2002 RFC 7405, DOI 10.17487/RFC7405, December 2014,
2003 .
2005 [RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC
2006 2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174,
2007 May 2017, .
2009 [TLS13] Rescorla, E., "The Transport Layer Security (TLS) Protocol
2010 Version 1.3", RFC 8446, DOI 10.17487/RFC8446, August 2018,
2011 .
2013 [URI] Berners-Lee, T., Fielding, R., and L. Masinter, "Uniform
2014 Resource Identifier (URI): Generic Syntax", STD 66,
2015 RFC 3986, DOI 10.17487/RFC3986, January 2005,
2016 .
2018 [USASCII] American National Standards Institute, "Coded Character
2019 Set -- 7-bit American Standard Code for Information
2020 Interchange", ANSI X3.4, 1986.
2022 [Welch] Welch, T. A., "A Technique for High-Performance Data
2023 Compression", IEEE Computer 17(6), June 1984.
2025 13.2. Informative References
2027 [Err4667] RFC Errata, Erratum ID 4667, RFC 7230,
2028 .
2030 [HTTP/1.0] Berners-Lee, T., Fielding, R.T., and H.F. Nielsen,
2031 "Hypertext Transfer Protocol -- HTTP/1.0", RFC 1945,
2032 DOI 10.17487/RFC1945, May 1996,
2033 .
2035 [Klein] Klein, A., "Divide and Conquer - HTTP Response Splitting,
2036 Web Cache Poisoning Attacks, and Related Topics", March
2037 2004, .
2040 [Linhart] Linhart, C., Klein, A., Heled, R., and S. Orrin, "HTTP
2041 Request Smuggling", June 2005,
2042 .
2045 [RFC2045] Freed, N. and N.S. Borenstein, "Multipurpose Internet Mail
2046 Extensions (MIME) Part One: Format of Internet Message
2047 Bodies", RFC 2045, DOI 10.17487/RFC2045, November 1996,
2048 .
2050 [RFC2046] Freed, N. and N. Borenstein, "Multipurpose Internet Mail
2051 Extensions (MIME) Part Two: Media Types", RFC 2046,
2052 DOI 10.17487/RFC2046, November 1996,
2053 .
2055 [RFC2049] Freed, N. and N.S. Borenstein, "Multipurpose Internet Mail
2056 Extensions (MIME) Part Five: Conformance Criteria and
2057 Examples", RFC 2049, DOI 10.17487/RFC2049, November 1996,
2058 .
2060 [RFC2068] Fielding, R., Gettys, J., Mogul, J., Nielsen, H., and T.
2061 Berners-Lee, "Hypertext Transfer Protocol -- HTTP/1.1",
2062 RFC 2068, DOI 10.17487/RFC2068, January 1997,
2063 .
2065 [RFC2557] Palme, F., Hopmann, A., Shelness, N., and E. Stefferud,
2066 "MIME Encapsulation of Aggregate Documents, such as HTML
2067 (MHTML)", RFC 2557, DOI 10.17487/RFC2557, March 1999,
2068 .
2070 [RFC5322] Resnick, P., "Internet Message Format", RFC 5322,
2071 DOI 10.17487/RFC5322, October 2008,
2072 .
2074 [RFC7230] Fielding, R., Ed. and J. F. Reschke, Ed., "Hypertext
2075 Transfer Protocol (HTTP/1.1): Message Syntax and Routing",
2076 RFC 7230, DOI 10.17487/RFC7230, June 2014,
2077 .
2079 [RFC8126] Cotton, M., Leiba, B., and T. Narten, "Guidelines for
2080 Writing an IANA Considerations Section in RFCs", BCP 26,
2081 RFC 8126, DOI 10.17487/RFC8126, June 2017,
2082 .
2084 Appendix A. Collected ABNF
2086 In the collected ABNF below, list rules are expanded as per
2087 Section 5.6.1.1 of [HTTP].
2089 BWS =
2091 HTTP-message = start-line CRLF *( field-line CRLF ) CRLF [
2092 message-body ]
2093 HTTP-name = %x48.54.54.50 ; HTTP
2094 HTTP-version = HTTP-name "/" DIGIT "." DIGIT
2096 OWS =
2098 RWS =
2100 Transfer-Encoding = [ transfer-coding *( OWS "," OWS transfer-coding
2101 ) ]
2103 absolute-URI =
2104 absolute-form = absolute-URI
2105 absolute-path =
2106 asterisk-form = "*"
2107 authority =
2108 authority-form = uri-host ":" port
2110 chunk = chunk-size [ chunk-ext ] CRLF chunk-data CRLF
2111 chunk-data = 1*OCTET
2112 chunk-ext = *( BWS ";" BWS chunk-ext-name [ BWS "=" BWS chunk-ext-val
2113 ] )
2114 chunk-ext-name = token
2115 chunk-ext-val = token / quoted-string
2116 chunk-size = 1*HEXDIG
2117 chunked-body = *chunk last-chunk trailer-section CRLF
2119 field-line = field-name ":" OWS field-value OWS
2120 field-name =
2121 field-value =
2123 last-chunk = 1*"0" [ chunk-ext ] CRLF
2125 message-body = *OCTET
2126 method = token
2128 obs-fold = OWS CRLF RWS
2129 obs-text =
2130 origin-form = absolute-path [ "?" query ]
2132 port =
2134 query =
2135 quoted-string =
2137 reason-phrase = 1*( HTAB / SP / VCHAR / obs-text )
2138 request-line = method SP request-target SP HTTP-version
2139 request-target = origin-form / absolute-form / authority-form /
2140 asterisk-form
2142 start-line = request-line / status-line
2143 status-code = 3DIGIT
2144 status-line = HTTP-version SP status-code SP [ reason-phrase ]
2146 token =
2147 trailer-section = *( field-line CRLF )
2148 transfer-coding =
2150 uri-host =
2152 Appendix B. Differences between HTTP and MIME
2154 HTTP/1.1 uses many of the constructs defined for the Internet Message
2155 Format [RFC5322] and the Multipurpose Internet Mail Extensions (MIME)
2156 [RFC2045] to allow a message body to be transmitted in an open
2157 variety of representations and with extensible fields. However, RFC
2158 2045 is focused only on email; applications of HTTP have many
2159 characteristics that differ from email; hence, HTTP has features that
2160 differ from MIME. These differences were carefully chosen to
2161 optimize performance over binary connections, to allow greater
2162 freedom in the use of new media types, to make date comparisons
2163 easier, and to acknowledge the practice of some early HTTP servers
2164 and clients.
2166 This appendix describes specific areas where HTTP differs from MIME.
2167 Proxies and gateways to and from strict MIME environments need to be
2168 aware of these differences and provide the appropriate conversions
2169 where necessary.
2171 B.1. MIME-Version
2173 HTTP is not a MIME-compliant protocol. However, messages can include
2174 a single MIME-Version header field to indicate what version of the
2175 MIME protocol was used to construct the message. Use of the MIME-
2176 Version header field indicates that the message is in full
2177 conformance with the MIME protocol (as defined in [RFC2045]).
2178 Senders are responsible for ensuring full conformance (where
2179 possible) when exporting HTTP messages to strict MIME environments.
2181 B.2. Conversion to Canonical Form
2183 MIME requires that an Internet mail body part be converted to
2184 canonical form prior to being transferred, as described in Section 4
2185 of [RFC2049], and that content with a type of "text" represent line
2186 breaks as CRLF, forbidding the use of CR or LF outside of line break
2187 sequences [RFC2046]. In contrast, HTTP does not care whether CRLF,
2188 bare CR, or bare LF are used to indicate a line break within content.
2190 A proxy or gateway from HTTP to a strict MIME environment ought to
2191 translate all line breaks within text media types to the RFC 2049
2192 canonical form of CRLF. Note, however, this might be complicated by
2193 the presence of a Content-Encoding and by the fact that HTTP allows
2194 the use of some charsets that do not use octets 13 and 10 to
2195 represent CR and LF, respectively.
2197 Conversion will break any cryptographic checksums applied to the
2198 original content unless the original content is already in canonical
2199 form. Therefore, the canonical form is recommended for any content
2200 that uses such checksums in HTTP.
2202 B.3. Conversion of Date Formats
2204 HTTP/1.1 uses a restricted set of date formats (Section 5.6.7 of
2205 [HTTP]) to simplify the process of date comparison. Proxies and
2206 gateways from other protocols ought to ensure that any Date header
2207 field present in a message conforms to one of the HTTP/1.1 formats
2208 and rewrite the date if necessary.
2210 B.4. Conversion of Content-Encoding
2212 MIME does not include any concept equivalent to HTTP/1.1's Content-
2213 Encoding header field. Since this acts as a modifier on the media
2214 type, proxies and gateways from HTTP to MIME-compliant protocols
2215 ought to either change the value of the Content-Type header field or
2216 decode the representation before forwarding the message. (Some
2217 experimental applications of Content-Type for Internet mail have used
2218 a media-type parameter of ";conversions=" to perform
2219 a function equivalent to Content-Encoding. However, this parameter
2220 is not part of the MIME standards).
2222 B.5. Conversion of Content-Transfer-Encoding
2224 HTTP does not use the Content-Transfer-Encoding field of MIME.
2225 Proxies and gateways from MIME-compliant protocols to HTTP need to
2226 remove any Content-Transfer-Encoding prior to delivering the response
2227 message to an HTTP client.
2229 Proxies and gateways from HTTP to MIME-compliant protocols are
2230 responsible for ensuring that the message is in the correct format
2231 and encoding for safe transport on that protocol, where "safe
2232 transport" is defined by the limitations of the protocol being used.
2233 Such a proxy or gateway ought to transform and label the data with an
2234 appropriate Content-Transfer-Encoding if doing so will improve the
2235 likelihood of safe transport over the destination protocol.
2237 B.6. MHTML and Line Length Limitations
2239 HTTP implementations that share code with MHTML [RFC2557]
2240 implementations need to be aware of MIME line length limitations.
2241 Since HTTP does not have this limitation, HTTP does not fold long
2242 lines. MHTML messages being transported by HTTP follow all
2243 conventions of MHTML, including line length limitations and folding,
2244 canonicalization, etc., since HTTP transfers message-bodies without
2245 modification and, aside from the "multipart/byteranges" type
2246 (Section 14.6 of [HTTP]), does not interpret the content or any MIME
2247 header lines that might be contained therein.
2249 Appendix C. Changes from previous RFCs
2251 C.1. Changes from HTTP/0.9
2253 Since HTTP/0.9 did not support header fields in a request, there is
2254 no mechanism for it to support name-based virtual hosts (selection of
2255 resource by inspection of the Host header field). Any server that
2256 implements name-based virtual hosts ought to disable support for
2257 HTTP/0.9. Most requests that appear to be HTTP/0.9 are, in fact,
2258 badly constructed HTTP/1.x requests caused by a client failing to
2259 properly encode the request-target.
2261 C.2. Changes from HTTP/1.0
2263 C.2.1. Multihomed Web Servers
2265 The requirements that clients and servers support the Host header
2266 field (Section 7.2 of [HTTP]), report an error if it is missing from
2267 an HTTP/1.1 request, and accept absolute URIs (Section 3.2) are among
2268 the most important changes defined by HTTP/1.1.
2270 Older HTTP/1.0 clients assumed a one-to-one relationship of IP
2271 addresses and servers; there was no other established mechanism for
2272 distinguishing the intended server of a request than the IP address
2273 to which that request was directed. The Host header field was
2274 introduced during the development of HTTP/1.1 and, though it was
2275 quickly implemented by most HTTP/1.0 browsers, additional
2276 requirements were placed on all HTTP/1.1 requests in order to ensure
2277 complete adoption. At the time of this writing, most HTTP-based
2278 services are dependent upon the Host header field for targeting
2279 requests.
2281 C.2.2. Keep-Alive Connections
2283 In HTTP/1.0, each connection is established by the client prior to
2284 the request and closed by the server after sending the response.
2285 However, some implementations implement the explicitly negotiated
2286 ("Keep-Alive") version of persistent connections described in
2287 Section 19.7.1 of [RFC2068].
2289 Some clients and servers might wish to be compatible with these
2290 previous approaches to persistent connections, by explicitly
2291 negotiating for them with a "Connection: keep-alive" request header
2292 field. However, some experimental implementations of HTTP/1.0
2293 persistent connections are faulty; for example, if an HTTP/1.0 proxy
2294 server doesn't understand Connection, it will erroneously forward
2295 that header field to the next inbound server, which would result in a
2296 hung connection.
2298 One attempted solution was the introduction of a Proxy-Connection
2299 header field, targeted specifically at proxies. In practice, this
2300 was also unworkable, because proxies are often deployed in multiple
2301 layers, bringing about the same problem discussed above.
2303 As a result, clients are encouraged not to send the Proxy-Connection
2304 header field in any requests.
2306 Clients are also encouraged to consider the use of Connection: keep-
2307 alive in requests carefully; while they can enable persistent
2308 connections with HTTP/1.0 servers, clients using them will need to
2309 monitor the connection for "hung" requests (which indicate that the
2310 client ought to stop sending the header field), and this mechanism
2311 ought not be used by clients at all when a proxy is being used.
2313 C.2.3. Introduction of Transfer-Encoding
2315 HTTP/1.1 introduces the Transfer-Encoding header field (Section 6.1).
2316 Transfer codings need to be decoded prior to forwarding an HTTP
2317 message over a MIME-compliant protocol.
2319 C.3. Changes from RFC 7230
2321 Most of the sections introducing HTTP's design goals, history,
2322 architecture, conformance criteria, protocol versioning, URIs,
2323 message routing, and header fields have been moved to [HTTP]. This
2324 document has been reduced to just the messaging syntax and connection
2325 management requirements specific to HTTP/1.1.
2327 Bare CRs have been prohibited outside of content. (Section 2.2)
2329 The ABNF definition of authority-form has changed from the more
2330 general authority component of a URI (in which port is optional) to
2331 the specific host:port format that is required by CONNECT.
2332 (Section 3.2.3)
2334 Required recipients to avoid smuggling/splitting attacks when
2335 processing an ambiguous message framing. (Section 6.1)
2337 In the ABNF for chunked extensions, re-introduced (bad) whitespace
2338 around ";" and "=". Whitespace was removed in [RFC7230], but that
2339 change was found to break existing implementations (see [Err4667]).
2340 (Section 7.1.1)
2341 Trailer field semantics now transcend the specifics of chunked
2342 encoding. The decoding algorithm for chunked (Section 7.1.3) has
2343 been updated to encourage storage/forwarding of trailer fields
2344 separately from the header section, to only allow merging into the
2345 header section if the recipient knows the corresponding field
2346 definition permits and defines how to merge, and otherwise to discard
2347 the trailer fields instead of merging. The trailer part is now
2348 called the trailer section to be more consistent with the header
2349 section and more distinct from a body part. (Section 7.1.2)
2351 Disallowed transfer coding parameters called "q" in order to avoid
2352 conflicts with the use of ranks in the TE header field.
2353 (Section 7.3)
2355 Appendix D. Change Log
2357 This section is to be removed before publishing as an RFC.
2359 D.1. Between RFC7230 and draft 00
2361 The changes were purely editorial:
2363 * Change boilerplate and abstract to indicate the "draft" status,
2364 and update references to ancestor specifications.
2366 * Adjust historical notes.
2368 * Update links to sibling specifications.
2370 * Replace sections listing changes from RFC 2616 by new empty
2371 sections referring to RFC 723x.
2373 * Remove acknowledgements specific to RFC 723x.
2375 * Move "Acknowledgements" to the very end and make them unnumbered.
2377 D.2. Since draft-ietf-httpbis-messaging-00
2379 The changes in this draft are editorial, with respect to HTTP as a
2380 whole, to move all core HTTP semantics into [HTTP]:
2382 * Moved introduction, architecture, conformance, and ABNF extensions
2383 from RFC 7230 (Messaging) to semantics [HTTP].
2385 * Moved discussion of MIME differences from RFC 7231 (Semantics) to
2386 Appendix B since they mostly cover transforming 1.1 messages.
2388 * Moved all extensibility tips, registration procedures, and
2389 registry tables from the IANA considerations to normative
2390 sections, reducing the IANA considerations to just instructions
2391 that will be removed prior to publication as an RFC.
2393 D.3. Since draft-ietf-httpbis-messaging-01
2395 * Cite RFC 8126 instead of RFC 5226 ()
2398 * Resolved erratum 4779, no change needed here
2399 (,
2400 )
2402 * In Section 7, fixed prose claiming transfer parameters allow bare
2403 names (,
2404 )
2406 * Resolved erratum 4225, no change needed here
2407 (,
2408 )
2410 * Replace "response code" with "response status code"
2411 (,
2412 )
2414 * In Section 9.3, clarify statement about HTTP/1.0 keep-alive
2415 (,
2416 )
2418 * In Section 7.1.1, re-introduce (bad) whitespace around ";" and "="
2419 (,
2420 , )
2423 * In Section 7.3, state that transfer codings should not use
2424 parameters named "q" (, )
2427 * In Section 7, mark coding name "trailers" as reserved in the IANA
2428 registry ()
2430 D.4. Since draft-ietf-httpbis-messaging-02
2432 * In Section 4, explain why the reason phrase should be ignored by
2433 clients ().
2435 * Add Section 9.2 to explain how request/response correlation is
2436 performed ()
2438 D.5. Since draft-ietf-httpbis-messaging-03
2440 * In Section 9.2, caution against treating data on a connection as
2441 part of a not-yet-issued request ()
2444 * In Section 7, remove the predefined codings from the ABNF and make
2445 it generic instead ()
2448 * Use RFC 7405 ABNF notation for case-sensitive string constants
2449 ()
2451 D.6. Since draft-ietf-httpbis-messaging-04
2453 * In Section 7.8 of [HTTP], clarify that protocol-name is to be
2454 matched case-insensitively ()
2457 * In Section 5.2, add leading optional whitespace to obs-fold ABNF
2458 (,
2459 )
2461 * In Section 4, add clarifications about empty reason phrases
2462 ()
2464 * Move discussion of retries from Section 9.3.1 into [HTTP]
2465 ()
2467 D.7. Since draft-ietf-httpbis-messaging-05
2469 * In Section 7.1.2, the trailer part has been renamed the trailer
2470 section (for consistency with the header section) and trailers are
2471 no longer merged as header fields by default, but rather can be
2472 discarded, kept separate from header fields, or merged with header
2473 fields only if understood and defined as being mergeable
2474 ()
2476 * In Section 2.1 and related Sections, move the trailing CRLF from
2477 the line grammars into the message format
2478 ()
2480 * Moved Section 2.3 down ()
2483 * In Section 7.8 of [HTTP], use 'websocket' instead of 'HTTP/2.0' in
2484 examples ()
2486 * Move version non-specific text from Section 6 into semantics as
2487 "payload" ()
2489 * In Section 9.8, add text from RFC 2818
2490 ()
2492 D.8. Since draft-ietf-httpbis-messaging-06
2494 * In Section 12.4, update the ALPN protocol ID for HTTP/1.1
2495 ()
2497 * In Section 5, align with updates to field terminology in semantics
2498 ()
2500 * In Section 7.6.1 of [HTTP], clarify that new connection options
2501 indeed need to be registered ()
2504 * In Section 1.1, reference RFC 8174 as well
2505 ()
2507 D.9. Since draft-ietf-httpbis-messaging-07
2509 * Move TE: trailers into [HTTP] ()
2512 * In Section 6.3, adjust requirements for handling multiple content-
2513 length values ()
2515 * Throughout, replace "effective request URI" with "target URI"
2516 ()
2518 * In Section 6.1, don't claim Transfer-Encoding is supported by
2519 HTTP/2 or later ()
2521 D.10. Since draft-ietf-httpbis-messaging-08
2523 * In Section 2.2, disallow bare CRs ()
2526 * Appendix A now uses the sender variant of the "#" list expansion
2527 ()
2529 * In Section 5, adjust IANA "Close" entry for new registry format
2530 ()
2532 D.11. Since draft-ietf-httpbis-messaging-09
2534 * Switch to xml2rfc v3 mode for draft generation
2535 ()
2537 D.12. Since draft-ietf-httpbis-messaging-10
2539 * In Section 6.3, note that TCP half-close does not delimit a
2540 request; talk about corresponding server-side behaviour in
2541 Section 9.6 ()
2543 * Moved requirements specific to HTTP/1.1 from [HTTP] into
2544 Section 3.2 ()
2546 * In Section 6.1 (Transfer-Encoding), adjust ABNF to allow empty
2547 lists ()
2549 * In Section 9.7, add text from RFC 2818
2550 ()
2552 * Moved definitions of "TE" and "Upgrade" into [HTTP]
2553 ()
2555 * Moved definition of "Connection" into [HTTP]
2556 ()
2558 D.13. Since draft-ietf-httpbis-messaging-11
2560 * Move IANA Upgrade Token Registry instructions to [HTTP]
2561 ()
2563 D.14. Since draft-ietf-httpbis-messaging-12
2565 * Moved content of history appendix to Semantics
2566 ()
2568 * Moved note about "close" being reserved as field name to
2569 Section 9.3 ()
2571 * Moved table of transfer codings into Section 12.3
2572 ()
2574 * In Section 13.2, updated the URI for the [Linhart] paper
2575 ()
2577 * Changed document title to just "HTTP/1.1"
2578 ()
2580 * In Section 7, moved transfer-coding ABNF to Section 10.1.4 of
2581 [HTTP] ()
2583 * Changed to using "payload data" when defining requirements about
2584 the data being conveyed within a message, instead of the terms
2585 "payload body" or "response body" or "representation body", since
2586 they often get confused with the HTTP/1.1 message body (which
2587 includes transfer coding) ()
2590 D.15. Since draft-ietf-httpbis-messaging-13
2592 * In Section 6.3, clarify that a message needs to be checked for
2593 both Content-Length and Transfer-Encoding, before processing
2594 Transfer-Encoding, and that ought to be treated as an error, but
2595 an intermediary can choose to forward the message downstream after
2596 removing the Content-Length and processing the Transfer-Encoding
2597 ()
2599 * Changed to using "content" instead of "payload" or "payload data"
2600 to avoid confusion with the payload of version-specific messaging
2601 frames ()
2603 D.16. Since draft-ietf-httpbis-messaging-14
2605 * In Section 9.6, define the close connection option, since its
2606 definition was removed from the Connection header field for being
2607 specific to 1.1 ()
2609 * In Section 3.3, clarify how the target URI is reconstructed when
2610 the request-target is not in absolute-form and highlight risk in
2611 selecting a default host ()
2614 * In Section 7.1, clarify large chunk handling issues
2615 ()
2617 * In Section 2.2, explicitly close the connection after sending a
2618 400 ()
2620 * In Section 2.3, refine version requirements for intermediaries
2621 ()
2623 * In Section 7.1.3, don't remove the Trailer header field
2624 ()
2626 * In Section 3.2.3, changed the ABNF definition of authority-form
2627 from the authority component (in which port is optional) to the
2628 host:port format that has always been required by CONNECT
2629 ()
2631 D.17. Since draft-ietf-httpbis-messaging-15
2633 * None.
2635 D.18. Since draft-ietf-httpbis-messaging-16
2637 This draft addresses mostly editorial issues raised during or past
2638 IETF Last Call; see for a summary.
2641 Furthermore:
2643 * In Section 6.1, require recipients to avoid smuggling/splitting
2644 attacks when processing an ambiguous message framing
2645 ()
2647 D.19. Since draft-ietf-httpbis-messaging-17
2649 * In Section 4, rephrase text about status code definitions in
2650 [HTTP] ()
2652 * In Section 9.2, clarify how to match responses to requests
2653 ()
2655 * Made reference to [RFC5322] normative, as it is referenced from
2656 the ABNF (for "From" header field) ()
2659 * In Section 5.2, include text about message/http that previously
2660 was in [HTTP] ()
2662 * Throughout, disambiguate "selected representation" and "selected
2663 response" (now "chosen response") ()
2666 Acknowledgements
2668 See Appendix "Acknowledgements" of [HTTP].
2670 Index
2672 A C D F G H M O R T X
2673 A
2675 absolute-form (of request-target) Section 3.2.2
2676 application/http Media Type Section 10.2
2677 asterisk-form (of request-target) Section 3.2.4
2678 authority-form (of request-target) Section 3.2.3
2680 C
2682 Connection header field Section 9.6
2683 Content-Length header field Section 6.2
2684 Content-Transfer-Encoding header field Appendix B.5
2685 chunked (Coding Format) Section 6.1; Section 6.3
2686 chunked (transfer coding) Section 7.1
2687 close Section 9.3; Section 9.6
2688 compress (transfer coding) Section 7.2
2690 D
2692 deflate (transfer coding) Section 7.2
2694 F
2696 Fields
2697 Close Section 9.6, Paragraph 4
2698 MIME-Version Appendix B.1
2699 Transfer-Encoding Section 6.1
2701 G
2703 Grammar
2704 ALPHA Section 1.2
2705 CR Section 1.2
2706 CRLF Section 1.2
2707 CTL Section 1.2
2708 DIGIT Section 1.2
2709 DQUOTE Section 1.2
2710 HEXDIG Section 1.2
2711 HTAB Section 1.2
2712 HTTP-message Section 2.1
2713 HTTP-name Section 2.3
2714 HTTP-version Section 2.3
2715 LF Section 1.2
2716 OCTET Section 1.2
2717 SP Section 1.2
2718 Transfer-Encoding Section 6.1
2719 VCHAR Section 1.2
2720 absolute-form Section 3.2; Section 3.2.2
2721 asterisk-form Section 3.2; Section 3.2.4
2722 authority-form Section 3.2; Section 3.2.3
2723 chunk Section 7.1
2724 chunk-data Section 7.1
2725 chunk-ext Section 7.1; Section 7.1.1
2726 chunk-ext-name Section 7.1.1
2727 chunk-ext-val Section 7.1.1
2728 chunk-size Section 7.1
2729 chunked-body Section 7.1
2730 field-line Section 5; Section 7.1.2
2731 field-name Section 5
2732 field-value Section 5
2733 last-chunk Section 7.1
2734 message-body Section 6
2735 method Section 3.1
2736 obs-fold Section 5.2
2737 origin-form Section 3.2; Section 3.2.1
2738 reason-phrase Section 4
2739 request-line Section 3
2740 request-target Section 3.2
2741 start-line Section 2.1
2742 status-code Section 4
2743 status-line Section 4
2744 trailer-section Section 7.1; Section 7.1.2
2745 gzip (transfer coding) Section 7.2
2747 H
2749 Header Fields
2750 MIME-Version Appendix B.1
2751 Transfer-Encoding Section 6.1
2752 header line Section 2.1
2753 header section Section 2.1
2754 headers Section 2.1
2756 M
2758 MIME-Version header field Appendix B.1
2759 Media Type
2760 application/http Section 10.2
2761 message/http Section 10.1
2762 message/http Media Type Section 10.1
2763 method Section 3.1
2765 O
2767 origin-form (of request-target) Section 3.2.1
2769 R
2771 request-target Section 3.2
2773 T
2775 Transfer-Encoding header field Section 6.1
2777 X
2779 x-compress (transfer coding) Section 7.2
2780 x-gzip (transfer coding) Section 7.2
2782 Authors' Addresses
2784 Roy T. Fielding (editor)
2785 Adobe
2786 345 Park Ave
2787 San Jose, CA 95110
2788 United States of America
2790 Email: fielding@gbiv.com
2791 URI: https://roy.gbiv.com/
2793 Mark Nottingham (editor)
2794 Fastly
2795 Prahran VIC
2796 Australia
2798 Email: mnot@mnot.net
2799 URI: https://www.mnot.net/
2801 Julian Reschke (editor)
2802 greenbytes GmbH
2803 Hafenweg 16
2804 48155 Münster
2805 Germany
2807 Email: julian.reschke@greenbytes.de
2808 URI: https://greenbytes.de/tech/webdav/