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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: 27 January 2022 J. Reschke, Ed.
7 greenbytes
8 26 July 2021
10 HTTP/1.1
11 draft-ietf-httpbis-messaging-17
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.18.
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 27 January 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 . . . . . . . . . . . . . . . . 27
114 9. Connection Management . . . . . . . . . . . . . . . . . . . . 28
115 9.1. Establishment . . . . . . . . . . . . . . . . . . . . . . 29
116 9.2. Associating a Response to a Request . . . . . . . . . . . 29
117 9.3. Persistence . . . . . . . . . . . . . . . . . . . . . . . 29
118 9.3.1. Retrying Requests . . . . . . . . . . . . . . . . . . 30
119 9.3.2. Pipelining . . . . . . . . . . . . . . . . . . . . . 31
120 9.4. Concurrency . . . . . . . . . . . . . . . . . . . . . . . 31
121 9.5. Failures and Timeouts . . . . . . . . . . . . . . . . . . 32
122 9.6. Tear-down . . . . . . . . . . . . . . . . . . . . . . . . 33
123 9.7. TLS Connection Initiation . . . . . . . . . . . . . . . . 34
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 . . . . . . . . . . . . . . . . . . . 39
132 11.4. Message Confidentiality . . . . . . . . . . . . . . . . 40
133 12. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 40
134 12.1. Field Name Registration . . . . . . . . . . . . . . . . 40
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 . . . . . . . . . . . . . . . . . . . . . . . . . 42
139 13.1. Normative References . . . . . . . . . . . . . . . . . . 42
140 13.2. Informative References . . . . . . . . . . . . . . . . . 43
141 Appendix A. Collected ABNF . . . . . . . . . . . . . . . . . . . 44
142 Appendix B. Differences between HTTP and MIME . . . . . . . . . 46
143 B.1. MIME-Version . . . . . . . . . . . . . . . . . . . . . . 46
144 B.2. Conversion to Canonical Form . . . . . . . . . . . . . . 47
145 B.3. Conversion of Date Formats . . . . . . . . . . . . . . . 47
146 B.4. Conversion of Content-Encoding . . . . . . . . . . . . . 47
147 B.5. Conversion of Content-Transfer-Encoding . . . . . . . . . 47
148 B.6. MHTML and Line Length Limitations . . . . . . . . . . . . 48
149 Appendix C. Changes from previous RFCs . . . . . . . . . . . . . 48
150 C.1. Changes from HTTP/0.9 . . . . . . . . . . . . . . . . . . 48
151 C.2. Changes from HTTP/1.0 . . . . . . . . . . . . . . . . . . 48
152 C.2.1. Multihomed Web Servers . . . . . . . . . . . . . . . 48
153 C.2.2. Keep-Alive Connections . . . . . . . . . . . . . . . 49
154 C.2.3. Introduction of Transfer-Encoding . . . . . . . . . . 49
155 C.3. Changes from RFC 7230 . . . . . . . . . . . . . . . . . . 50
156 Appendix D. Change Log . . . . . . . . . . . . . . . . . . . . . 50
157 D.1. Between RFC7230 and draft 00 . . . . . . . . . . . . . . 50
158 D.2. Since draft-ietf-httpbis-messaging-00 . . . . . . . . . . 51
159 D.3. Since draft-ietf-httpbis-messaging-01 . . . . . . . . . . 51
160 D.4. Since draft-ietf-httpbis-messaging-02 . . . . . . . . . . 52
161 D.5. Since draft-ietf-httpbis-messaging-03 . . . . . . . . . . 52
162 D.6. Since draft-ietf-httpbis-messaging-04 . . . . . . . . . . 52
163 D.7. Since draft-ietf-httpbis-messaging-05 . . . . . . . . . . 53
164 D.8. Since draft-ietf-httpbis-messaging-06 . . . . . . . . . . 53
165 D.9. Since draft-ietf-httpbis-messaging-07 . . . . . . . . . . 53
166 D.10. Since draft-ietf-httpbis-messaging-08 . . . . . . . . . . 54
167 D.11. Since draft-ietf-httpbis-messaging-09 . . . . . . . . . . 54
168 D.12. Since draft-ietf-httpbis-messaging-10 . . . . . . . . . . 54
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 . . . . . . . . . . 55
172 D.16. Since draft-ietf-httpbis-messaging-14 . . . . . . . . . . 55
173 D.17. Since draft-ietf-httpbis-messaging-15 . . . . . . . . . . 56
174 D.18. Since draft-ietf-httpbis-messaging-16 . . . . . . . . . . 56
175 Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . . 56
176 Index . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 57
177 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 59
179 1. Introduction
181 The Hypertext Transfer Protocol (HTTP) is a stateless application-
182 level request/response protocol that uses extensible semantics and
183 self-descriptive messages for flexible interaction with network-based
184 hypertext information systems. HTTP/1.1 is defined by:
186 * This document
188 * "HTTP Semantics" [HTTP]
190 * "HTTP Caching" [CACHING]
191 This document specifies how HTTP semantics are conveyed using the
192 HTTP/1.1 message syntax, framing and connection management
193 mechanisms. Its goal is to define the complete set of requirements
194 for HTTP/1.1 message parsers and message-forwarding intermediaries.
196 This document obsoletes the portions of RFC 7230 related to HTTP/1.1
197 messaging and connection management, with the changes being
198 summarized in Appendix C.3. The other parts of RFC 7230 are
199 obsoleted by "HTTP Semantics" [HTTP].
201 1.1. Requirements Notation
203 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
204 "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and
205 "OPTIONAL" in this document are to be interpreted as described in BCP
206 14 [RFC2119] [RFC8174] when, and only when, they appear in all
207 capitals, as shown here.
209 Conformance criteria and considerations regarding error handling are
210 defined in Section 2 of [HTTP].
212 1.2. Syntax Notation
214 This specification uses the Augmented Backus-Naur Form (ABNF)
215 notation of [RFC5234], extended with the notation for case-
216 sensitivity in strings defined in [RFC7405].
218 It also uses a list extension, defined in Section 5.6.1 of [HTTP],
219 that allows for compact definition of comma-separated lists using a
220 '#' operator (similar to how the '*' operator indicates repetition).
221 Appendix A shows the collected grammar with all list operators
222 expanded to standard ABNF notation.
224 As a convention, ABNF rule names prefixed with "obs-" denote
225 "obsolete" grammar rules that appear for historical reasons.
227 The following core rules are included by reference, as defined in
228 [RFC5234], Appendix B.1: ALPHA (letters), CR (carriage return), CRLF
229 (CR LF), CTL (controls), DIGIT (decimal 0-9), DQUOTE (double quote),
230 HEXDIG (hexadecimal 0-9/A-F/a-f), HTAB (horizontal tab), LF (line
231 feed), OCTET (any 8-bit sequence of data), SP (space), and VCHAR (any
232 visible [USASCII] character).
234 The rules below are defined in [HTTP]:
236 BWS =
237 OWS =
238 RWS =
239 absolute-path =
240 field-name =
241 field-value =
242 obs-text =
243 quoted-string =
244 token =
245 transfer-coding =
246
248 The rules below are defined in [URI]:
250 absolute-URI =
251 authority =
252 uri-host =
253 port =
254 query =
256 2. Message
258 HTTP/1.1 communication consists of sending stateless request and
259 response messages across a connection. See Section 3 of [HTTP] for
260 the general terminology and core concepts of HTTP.
262 2.1. Message Format
264 An HTTP/1.1 message consists of a start-line followed by a CRLF and a
265 sequence of octets in a format similar to the Internet Message Format
266 [RFC5322]: zero or more header field lines (collectively referred to
267 as the "headers" or the "header section"), an empty line indicating
268 the end of the header section, and an optional message body.
270 HTTP-message = start-line CRLF
271 *( field-line CRLF )
272 CRLF
273 [ message-body ]
275 A message can be either a request from client to server or a response
276 from server to client. Syntactically, the two types of message
277 differ only in the start-line, which is either a request-line (for
278 requests) or a status-line (for responses), and in the algorithm for
279 determining the length of the message body (Section 6).
281 start-line = request-line / status-line
283 In theory, a client could receive requests and a server could receive
284 responses, distinguishing them by their different start-line formats.
285 In practice, servers are implemented to only expect a request (a
286 response is interpreted as an unknown or invalid request method) and
287 clients are implemented to only expect a response.
289 HTTP makes use of some protocol elements similar to the Multipurpose
290 Internet Mail Extensions (MIME) [RFC2045]. See Appendix B for the
291 differences between HTTP and MIME messages.
293 2.2. Message Parsing
295 The normal procedure for parsing an HTTP message is to read the
296 start-line into a structure, read each header field line into a hash
297 table by field name until the empty line, and then use the parsed
298 data to determine if a message body is expected. If a message body
299 has been indicated, then it is read as a stream until an amount of
300 octets equal to the message body length is read or the connection is
301 closed.
303 A recipient MUST parse an HTTP message as a sequence of octets in an
304 encoding that is a superset of US-ASCII [USASCII]. Parsing an HTTP
305 message as a stream of Unicode characters, without regard for the
306 specific encoding, creates security vulnerabilities due to the
307 varying ways that string processing libraries handle invalid
308 multibyte character sequences that contain the octet LF (%x0A).
309 String-based parsers can only be safely used within protocol elements
310 after the element has been extracted from the message, such as within
311 a header field line value after message parsing has delineated the
312 individual field lines.
314 Although the line terminator for the start-line and fields is the
315 sequence CRLF, a recipient MAY recognize a single LF as a line
316 terminator and ignore any preceding CR.
318 A sender MUST NOT generate a bare CR (a CR character not immediately
319 followed by LF) within any protocol elements other than the content.
320 A recipient of such a bare CR MUST consider that element to be
321 invalid or replace each bare CR with SP before processing the element
322 or forwarding the message.
324 Older HTTP/1.0 user agent implementations might send an extra CRLF
325 after a POST request as a workaround for some early server
326 applications that failed to read message body content that was not
327 terminated by a line-ending. An HTTP/1.1 user agent MUST NOT preface
328 or follow a request with an extra CRLF. If terminating the request
329 message body with a line-ending is desired, then the user agent MUST
330 count the terminating CRLF octets as part of the message body length.
332 In the interest of robustness, a server that is expecting to receive
333 and parse a request-line SHOULD ignore at least one empty line (CRLF)
334 received prior to the request-line.
336 A sender MUST NOT send whitespace between the start-line and the
337 first header field. A recipient that receives whitespace between the
338 start-line and the first header field MUST either reject the message
339 as invalid or consume each whitespace-preceded line without further
340 processing of it (i.e., ignore the entire line, along with any
341 subsequent lines preceded by whitespace, until a properly formed
342 header field is received or the header section is terminated).
344 The presence of such whitespace in a request might be an attempt to
345 trick a server into ignoring that field line or processing the line
346 after it as a new request, either of which might result in a security
347 vulnerability if other implementations within the request chain
348 interpret the same message differently. Likewise, the presence of
349 such whitespace in a response might be ignored by some clients or
350 cause others to cease parsing.
352 When a server listening only for HTTP request messages, or processing
353 what appears from the start-line to be an HTTP request message,
354 receives a sequence of octets that does not match the HTTP-message
355 grammar aside from the robustness exceptions listed above, the server
356 SHOULD respond with a 400 (Bad Request) response and close the
357 connection.
359 2.3. HTTP Version
361 HTTP uses a "." numbering scheme to indicate versions
362 of the protocol. This specification defines version "1.1".
363 Section 2.5 of [HTTP] specifies the semantics of HTTP version
364 numbers.
366 The version of an HTTP/1.x message is indicated by an HTTP-version
367 field in the start-line. HTTP-version is case-sensitive.
369 HTTP-version = HTTP-name "/" DIGIT "." DIGIT
370 HTTP-name = %s"HTTP"
372 When an HTTP/1.1 message is sent to an HTTP/1.0 recipient [HTTP/1.0]
373 or a recipient whose version is unknown, the HTTP/1.1 message is
374 constructed such that it can be interpreted as a valid HTTP/1.0
375 message if all of the newer features are ignored. This specification
376 places recipient-version requirements on some new features so that a
377 conformant sender will only use compatible features until it has
378 determined, through configuration or the receipt of a message, that
379 the recipient supports HTTP/1.1.
381 Intermediaries that process HTTP messages (i.e., all intermediaries
382 other than those acting as tunnels) MUST send their own HTTP-version
383 in forwarded messages, unless it is purposefully downgraded as a
384 workaround for an upstream issue. In other words, an intermediary is
385 not allowed to blindly forward the start-line without ensuring that
386 the protocol version in that message matches a version to which that
387 intermediary is conformant for both the receiving and sending of
388 messages. Forwarding an HTTP message without rewriting the HTTP-
389 version might result in communication errors when downstream
390 recipients use the message sender's version to determine what
391 features are safe to use for later communication with that sender.
393 A server MAY send an HTTP/1.0 response to an HTTP/1.1 request if it
394 is known or suspected that the client incorrectly implements the HTTP
395 specification and is incapable of correctly processing later version
396 responses, such as when a client fails to parse the version number
397 correctly or when an intermediary is known to blindly forward the
398 HTTP-version even when it doesn't conform to the given minor version
399 of the protocol. Such protocol downgrades SHOULD NOT be performed
400 unless triggered by specific client attributes, such as when one or
401 more of the request header fields (e.g., User-Agent) uniquely match
402 the values sent by a client known to be in error.
404 3. Request Line
406 A request-line begins with a method token, followed by a single space
407 (SP), the request-target, another single space (SP), and ends with
408 the protocol version.
410 request-line = method SP request-target SP HTTP-version
412 Although the request-line grammar rule requires that each of the
413 component elements be separated by a single SP octet, recipients MAY
414 instead parse on whitespace-delimited word boundaries and, aside from
415 the CRLF terminator, treat any form of whitespace as the SP separator
416 while ignoring preceding or trailing whitespace; such whitespace
417 includes one or more of the following octets: SP, HTAB, VT (%x0B), FF
418 (%x0C), or bare CR. However, lenient parsing can result in request
419 smuggling security vulnerabilities if there are multiple recipients
420 of the message and each has its own unique interpretation of
421 robustness (see Section 11.2).
423 HTTP does not place a predefined limit on the length of a request-
424 line, as described in Section 2 of [HTTP]. A server that receives a
425 method longer than any that it implements SHOULD respond with a 501
426 (Not Implemented) status code. A server that receives a request-
427 target longer than any URI it wishes to parse MUST respond with a 414
428 (URI Too Long) status code (see Section 15.5.15 of [HTTP]).
430 Various ad hoc limitations on request-line length are found in
431 practice. It is RECOMMENDED that all HTTP senders and recipients
432 support, at a minimum, request-line lengths of 8000 octets.
434 3.1. Method
436 The method token indicates the request method to be performed on the
437 target resource. The request method is case-sensitive.
439 method = token
441 The request methods defined by this specification can be found in
442 Section 9 of [HTTP], along with information regarding the HTTP method
443 registry and considerations for defining new methods.
445 3.2. Request Target
447 The request-target identifies the target resource upon which to apply
448 the request. The client derives a request-target from its desired
449 target URI. There are four distinct formats for the request-target,
450 depending on both the method being requested and whether the request
451 is to a proxy.
453 request-target = origin-form
454 / absolute-form
455 / authority-form
456 / asterisk-form
458 No whitespace is allowed in the request-target. Unfortunately, some
459 user agents fail to properly encode or exclude whitespace found in
460 hypertext references, resulting in those disallowed characters being
461 sent as the request-target in a malformed request-line.
463 Recipients of an invalid request-line SHOULD respond with either a
464 400 (Bad Request) error or a 301 (Moved Permanently) redirect with
465 the request-target properly encoded. A recipient SHOULD NOT attempt
466 to autocorrect and then process the request without a redirect, since
467 the invalid request-line might be deliberately crafted to bypass
468 security filters along the request chain.
470 A client MUST send a Host header field in all HTTP/1.1 request
471 messages. If the target URI includes an authority component, then a
472 client MUST send a field value for Host that is identical to that
473 authority component, excluding any userinfo subcomponent and its "@"
474 delimiter (Section 4.2.1 of [HTTP]). If the authority component is
475 missing or undefined for the target URI, then a client MUST send a
476 Host header field with an empty field value.
478 A server MUST respond with a 400 (Bad Request) status code to any
479 HTTP/1.1 request message that lacks a Host header field and to any
480 request message that contains more than one Host header field line or
481 a Host header field with an invalid field value.
483 3.2.1. origin-form
485 The most common form of request-target is the _origin-form_.
487 origin-form = absolute-path [ "?" query ]
489 When making a request directly to an origin server, other than a
490 CONNECT or server-wide OPTIONS request (as detailed below), a client
491 MUST send only the absolute path and query components of the target
492 URI as the request-target. If the target URI's path component is
493 empty, the client MUST send "/" as the path within the origin-form of
494 request-target. A Host header field is also sent, as defined in
495 Section 7.2 of [HTTP].
497 For example, a client wishing to retrieve a representation of the
498 resource identified as
500 http://www.example.org/where?q=now
502 directly from the origin server would open (or reuse) a TCP
503 connection to port 80 of the host "www.example.org" and send the
504 lines:
506 GET /where?q=now HTTP/1.1
507 Host: www.example.org
509 followed by the remainder of the request message.
511 3.2.2. absolute-form
513 When making a request to a proxy, other than a CONNECT or server-wide
514 OPTIONS request (as detailed below), a client MUST send the target
515 URI in _absolute-form_ as the request-target.
517 absolute-form = absolute-URI
519 The proxy is requested to either service that request from a valid
520 cache, if possible, or make the same request on the client's behalf
521 to either the next inbound proxy server or directly to the origin
522 server indicated by the request-target. Requirements on such
523 "forwarding" of messages are defined in Section 7.6 of [HTTP].
525 An example absolute-form of request-line would be:
527 GET http://www.example.org/pub/WWW/TheProject.html HTTP/1.1
529 A client MUST send a Host header field in an HTTP/1.1 request even if
530 the request-target is in the absolute-form, since this allows the
531 Host information to be forwarded through ancient HTTP/1.0 proxies
532 that might not have implemented Host.
534 When a proxy receives a request with an absolute-form of request-
535 target, the proxy MUST ignore the received Host header field (if any)
536 and instead replace it with the host information of the request-
537 target. A proxy that forwards such a request MUST generate a new
538 Host field value based on the received request-target rather than
539 forward the received Host field value.
541 When an origin server receives a request with an absolute-form of
542 request-target, the origin server MUST ignore the received Host
543 header field (if any) and instead use the host information of the
544 request-target. Note that if the request-target does not have an
545 authority component, an empty Host header field will be sent in this
546 case.
548 A server MUST accept the absolute-form in requests even though most
549 HTTP/1.1 clients will only send the absolute-form to a proxy.
551 3.2.3. authority-form
553 The _authority-form_ of request-target is only used for CONNECT
554 requests (Section 9.3.6 of [HTTP]). It consists of only the uri-host
555 and port number of the tunnel destination, separated by a colon
556 (":").
558 authority-form = uri-host ":" port
560 When making a CONNECT request to establish a tunnel through one or
561 more proxies, a client MUST send only the host and port of the tunnel
562 destination as the request-target. The client obtains the host and
563 port from the target URI's authority component, except that it sends
564 the scheme's default port if the target URI elides the port. For
565 example, a CONNECT request to "http://www.example.com" looks like
567 CONNECT www.example.com:80 HTTP/1.1
568 Host: www.example.com
570 3.2.4. asterisk-form
572 The _asterisk-form_ of request-target is only used for a server-wide
573 OPTIONS request (Section 9.3.7 of [HTTP]).
575 asterisk-form = "*"
577 When a client wishes to request OPTIONS for the server as a whole, as
578 opposed to a specific named resource of that server, the client MUST
579 send only "*" (%x2A) as the request-target. For example,
581 OPTIONS * HTTP/1.1
583 If a proxy receives an OPTIONS request with an absolute-form of
584 request-target in which the URI has an empty path and no query
585 component, then the last proxy on the request chain MUST send a
586 request-target of "*" when it forwards the request to the indicated
587 origin server.
589 For example, the request
591 OPTIONS http://www.example.org:8001 HTTP/1.1
593 would be forwarded by the final proxy as
595 OPTIONS * HTTP/1.1
596 Host: www.example.org:8001
598 after connecting to port 8001 of host "www.example.org".
600 3.3. Reconstructing the Target URI
602 The target URI is the request-target when the request-target is in
603 absolute-form. In that case, a server will parse the URI into its
604 generic components for further evaluation.
606 Otherwise, the server reconstructs the target URI from the connection
607 context and various parts of the request message in order to identify
608 the target resource (Section 7.1 of [HTTP]):
610 * If the server's configuration provides for a fixed URI scheme, or
611 a scheme is provided by a trusted outbound gateway, that scheme is
612 used for the target URI. This is common in large-scale
613 deployments because a gateway server will receive the client's
614 connection context and replace that with their own connection to
615 the inbound server. Otherwise, if the request is received over a
616 secured connection, the target URI's scheme is "https"; if not,
617 the scheme is "http".
619 * If the request-target is in authority-form, the target URI's
620 authority component is the request-target. Otherwise, the target
621 URI's authority component is the field value of the Host header
622 field. If there is no Host header field or if its field value is
623 empty or invalid, the target URI's authority component is empty.
625 * If the request-target is in authority-form or asterisk-form, the
626 target URI's combined path and query component is empty.
627 Otherwise, the target URI's combined path and query component is
628 the request-target.
630 * The components of a reconstructed target URI, once determined as
631 above, can be recombined into absolute-URI form by concatenating
632 the scheme, "://", authority, and combined path and query
633 component.
635 Example 1: the following message received over a secure connection
637 GET /pub/WWW/TheProject.html HTTP/1.1
638 Host: www.example.org
640 has a target URI of
642 https://www.example.org/pub/WWW/TheProject.html
644 Example 2: the following message received over an insecure connection
646 OPTIONS * HTTP/1.1
647 Host: www.example.org:8080
649 has a target URI of
651 http://www.example.org:8080
653 If the target URI's authority component is empty and its URI scheme
654 requires a non-empty authority (as is the case for "http" and
655 "https"), the server can reject the request or determine whether a
656 configured default applies that is consistent with the incoming
657 connection's context. Context might include connection details like
658 address and port, what security has been applied, and locally-defined
659 information specific to that server's configuration. An empty
660 authority is replaced with the configured default before further
661 processing of the request.
663 Supplying a default name for authority within the context of a
664 secured connection is inherently unsafe if there is any chance that
665 the user agent's intended authority might differ from the selected
666 default. A server that can uniquely identify an authority from the
667 request context MAY use that identity as a default without this risk.
668 Alternatively, it might be better to redirect the request to a safe
669 resource that explains how to obtain a new client.
671 Note that reconstructing the client's target URI is only half of the
672 process for identifying a target resource. The other half is
673 determining whether that target URI identifies a resource for which
674 the server is willing and able to send a response, as defined in
675 Section 7.4 of [HTTP].
677 4. Status Line
679 The first line of a response message is the status-line, consisting
680 of the protocol version, a space (SP), the status code, another
681 space, and ending with an OPTIONAL textual phrase describing the
682 status code.
684 status-line = HTTP-version SP status-code SP [reason-phrase]
686 Although the status-line grammar rule requires that each of the
687 component elements be separated by a single SP octet, recipients MAY
688 instead parse on whitespace-delimited word boundaries and, aside from
689 the line terminator, treat any form of whitespace as the SP separator
690 while ignoring preceding or trailing whitespace; such whitespace
691 includes one or more of the following octets: SP, HTAB, VT (%x0B), FF
692 (%x0C), or bare CR. However, lenient parsing can result in response
693 splitting security vulnerabilities if there are multiple recipients
694 of the message and each has its own unique interpretation of
695 robustness (see Section 11.1).
697 The status-code element is a 3-digit integer code describing the
698 result of the server's attempt to understand and satisfy the client's
699 corresponding request. The rest of the response message is to be
700 interpreted in light of the semantics defined for that status code.
701 See Section 15 of [HTTP] for information about the semantics of
702 status codes, including the classes of status code (indicated by the
703 first digit), the status codes defined by this specification,
704 considerations for the definition of new status codes, and the IANA
705 registry.
707 status-code = 3DIGIT
709 The reason-phrase element exists for the sole purpose of providing a
710 textual description associated with the numeric status code, mostly
711 out of deference to earlier Internet application protocols that were
712 more frequently used with interactive text clients.
714 reason-phrase = 1*( HTAB / SP / VCHAR / obs-text )
716 A client SHOULD ignore the reason-phrase content because it is not a
717 reliable channel for information (it might be translated for a given
718 locale, overwritten by intermediaries, or discarded when the message
719 is forwarded via other versions of HTTP). A server MUST send the
720 space that separates status-code from the reason-phrase even when the
721 reason-phrase is absent (i.e., the status-line would end with the
722 three octets SP CR LF).
724 5. Field Syntax
726 Each field line consists of a case-insensitive field name followed by
727 a colon (":"), optional leading whitespace, the field line value, and
728 optional trailing whitespace.
730 field-line = field-name ":" OWS field-value OWS
732 Most HTTP field names and the rules for parsing within field values
733 are defined in Section 6.3 of [HTTP]. This section covers the
734 generic syntax for header field inclusion within, and extraction
735 from, HTTP/1.1 messages.
737 5.1. Field Line Parsing
739 Messages are parsed using a generic algorithm, independent of the
740 individual field names. The contents within a given field line value
741 are not parsed until a later stage of message interpretation (usually
742 after the message's entire field section has been processed).
744 No whitespace is allowed between the field name and colon. In the
745 past, differences in the handling of such whitespace have led to
746 security vulnerabilities in request routing and response handling. A
747 server MUST reject any received request message that contains
748 whitespace between a header field name and colon with a response
749 status code of 400 (Bad Request). A proxy MUST remove any such
750 whitespace from a response message before forwarding the message
751 downstream.
753 A field line value might be preceded and/or followed by optional
754 whitespace (OWS); a single SP preceding the field line value is
755 preferred for consistent readability by humans. The field line value
756 does not include any leading or trailing whitespace: OWS occurring
757 before the first non-whitespace octet of the field line value or
758 after the last non-whitespace octet of the field line value ought to
759 be excluded by parsers when extracting the field line value from a
760 field line.
762 5.2. Obsolete Line Folding
764 Historically, HTTP field line values could be extended over multiple
765 lines by preceding each extra line with at least one space or
766 horizontal tab (obs-fold). This specification deprecates such line
767 folding except within the message/http media type (Section 10.1).
769 obs-fold = OWS CRLF RWS
770 ; obsolete line folding
772 A sender MUST NOT generate a message that includes line folding
773 (i.e., that has any field line value that contains a match to the
774 obs-fold rule) unless the message is intended for packaging within
775 the message/http media type.
777 A server that receives an obs-fold in a request message that is not
778 within a message/http container MUST either reject the message by
779 sending a 400 (Bad Request), preferably with a representation
780 explaining that obsolete line folding is unacceptable, or replace
781 each received obs-fold with one or more SP octets prior to
782 interpreting the field value or forwarding the message downstream.
784 A proxy or gateway that receives an obs-fold in a response message
785 that is not within a message/http container MUST either discard the
786 message and replace it with a 502 (Bad Gateway) response, preferably
787 with a representation explaining that unacceptable line folding was
788 received, or replace each received obs-fold with one or more SP
789 octets prior to interpreting the field value or forwarding the
790 message downstream.
792 A user agent that receives an obs-fold in a response message that is
793 not within a message/http container MUST replace each received
794 obs-fold with one or more SP octets prior to interpreting the field
795 value.
797 6. Message Body
799 The message body (if any) of an HTTP/1.1 message is used to carry
800 content (Section 6.4 of [HTTP]) for the request or response. The
801 message body is identical to the content unless a transfer coding has
802 been applied, as described in Section 6.1.
804 message-body = *OCTET
806 The rules for determining when a message body is present in an
807 HTTP/1.1 message differ for requests and responses.
809 The presence of a message body in a request is signaled by a
810 Content-Length or Transfer-Encoding header field. Request message
811 framing is independent of method semantics.
813 The presence of a message body in a response depends on both the
814 request method to which it is responding and the response status code
815 (Section 4), and corresponds to when content is allowed; see
816 Section 6.4 of [HTTP].
818 6.1. Transfer-Encoding
820 The Transfer-Encoding header field lists the transfer coding names
821 corresponding to the sequence of transfer codings that have been (or
822 will be) applied to the content in order to form the message body.
823 Transfer codings are defined in Section 7.
825 Transfer-Encoding = #transfer-coding
826 ; defined in [HTTP], Section 10.1.4
828 Transfer-Encoding is analogous to the Content-Transfer-Encoding field
829 of MIME, which was designed to enable safe transport of binary data
830 over a 7-bit transport service ([RFC2045], Section 6). However, safe
831 transport has a different focus for an 8bit-clean transfer protocol.
832 In HTTP's case, Transfer-Encoding is primarily intended to accurately
833 delimit dynamically generated content and to distinguish encodings
834 that are only applied for transport efficiency or security from those
835 that are characteristics of the selected resource.
837 A recipient MUST be able to parse the chunked transfer coding
838 (Section 7.1) because it plays a crucial role in framing messages
839 when the content size is not known in advance. A sender MUST NOT
840 apply the chunked transfer coding more than once to a message body
841 (i.e., chunking an already chunked message is not allowed). If any
842 transfer coding other than chunked is applied to a request's content,
843 the sender MUST apply chunked as the final transfer coding to ensure
844 that the message is properly framed. If any transfer coding other
845 than chunked is applied to a response's content, the sender MUST
846 either apply chunked as the final transfer coding or terminate the
847 message by closing the connection.
849 For example,
851 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 highest ordered request that has not yet received a final (non-
1354 1xx) response.
1356 If an HTTP/1.1 client receives data on a connection that doesn't have
1357 any outstanding requests, it MUST NOT consider them to be a response
1358 to a not-yet-issued request; it SHOULD close the connection, since
1359 message delimitation is now ambiguous, unless the data consists only
1360 of one 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 number of multiple
1481 connections can also cause side effects in otherwise uncongested
1482 networks, because their aggregate and initially synchronized sending
1483 behavior can cause congestion that would not have been present if
1484 fewer 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. When a valid
1609 closure alert is received, an implementation can be assured that no
1610 further data will be received on that connection. TLS
1611 implementations MUST initiate an exchange of closure alerts before
1612 closing a connection. A TLS implementation MAY, after sending a
1613 closure alert, close the connection without waiting for the peer to
1614 send its closure alert, generating an "incomplete close". This
1615 SHOULD only be done when the application knows (typically through
1616 detecting HTTP message boundaries) that it has sent or received all
1617 the message data that it cares about.
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. Handing 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.
1660 Type name: message
1662 Subtype name: http
1664 Required parameters: N/A
1666 Optional parameters: version, msgtype
1668 version: The HTTP-version number of the enclosed message (e.g.,
1669 "1.1"). If not present, the version can be determined from the
1670 first line of the body.
1672 msgtype: The message type - "request" or "response". If not
1673 present, the type can be determined from the first line of the
1674 body.
1676 Encoding considerations: only "7bit", "8bit", or "binary" are
1677 permitted
1679 Security considerations: see Section 11
1681 Interoperability considerations: N/A
1683 Published specification: This specification (see Section 10.1).
1685 Applications that use this media type: N/A
1687 Fragment identifier considerations: N/A
1689 Additional information: Magic number(s): N/A
1691 Deprecated alias names for this type: N/A
1693 File extension(s): N/A
1695 Macintosh file type code(s): N/A
1697 Person and email address to contact for further information: See Aut
1698 hors' Addresses section.
1700 Intended usage: COMMON
1702 Restrictions on usage: N/A
1704 Author: See Authors' Addresses section.
1706 Change controller: IESG
1708 10.2. Media Type application/http
1710 The application/http media type can be used to enclose a pipeline of
1711 one or more HTTP request or response messages (not intermixed).
1713 Type name: application
1715 Subtype name: http
1717 Required parameters: N/A
1719 Optional parameters: version, msgtype
1721 version: The HTTP-version number of the enclosed messages (e.g.,
1722 "1.1"). If not present, the version can be determined from the
1723 first line of the body.
1725 msgtype: The message type - "request" or "response". If not
1726 present, the type can be determined from the first line of the
1727 body.
1729 Encoding considerations: HTTP messages enclosed by this type are in
1730 "binary" format; use of an appropriate Content-Transfer-Encoding
1731 is required when transmitted via email.
1733 Security considerations: see Section 11
1735 Interoperability considerations: N/A
1737 Published specification: This specification (see Section 10.2).
1739 Applications that use this media type: N/A
1741 Fragment identifier considerations: N/A
1743 Additional information: Deprecated alias names for this type: N/A
1745 Magic number(s): N/A
1747 File extension(s): N/A
1748 Macintosh file type code(s): N/A
1750 Person and email address to contact for further information: See Aut
1751 hors' Addresses section.
1753 Intended usage: COMMON
1755 Restrictions on usage: N/A
1757 Author: See Authors' Addresses section.
1759 Change controller: IESG
1761 11. Security Considerations
1763 This section is meant to inform developers, information providers,
1764 and users about known security considerations relevant to HTTP
1765 message syntax and parsing. Security considerations about HTTP
1766 semantics, content, and routing are addressed in [HTTP].
1768 11.1. Response Splitting
1770 Response splitting (a.k.a., CRLF injection) is a common technique,
1771 used in various attacks on Web usage, that exploits the line-based
1772 nature of HTTP message framing and the ordered association of
1773 requests to responses on persistent connections [Klein]. This
1774 technique can be particularly damaging when the requests pass through
1775 a shared cache.
1777 Response splitting exploits a vulnerability in servers (usually
1778 within an application server) where an attacker can send encoded data
1779 within some parameter of the request that is later decoded and echoed
1780 within any of the response header fields of the response. If the
1781 decoded data is crafted to look like the response has ended and a
1782 subsequent response has begun, the response has been split and the
1783 content within the apparent second response is controlled by the
1784 attacker. The attacker can then make any other request on the same
1785 persistent connection and trick the recipients (including
1786 intermediaries) into believing that the second half of the split is
1787 an authoritative answer to the second request.
1789 For example, a parameter within the request-target might be read by
1790 an application server and reused within a redirect, resulting in the
1791 same parameter being echoed in the Location header field of the
1792 response. If the parameter is decoded by the application and not
1793 properly encoded when placed in the response field, the attacker can
1794 send encoded CRLF octets and other content that will make the
1795 application's single response look like two or more responses.
1797 A common defense against response splitting is to filter requests for
1798 data that looks like encoded CR and LF (e.g., "%0D" and "%0A").
1799 However, that assumes the application server is only performing URI
1800 decoding, rather than more obscure data transformations like charset
1801 transcoding, XML entity translation, base64 decoding, sprintf
1802 reformatting, etc. A more effective mitigation is to prevent
1803 anything other than the server's core protocol libraries from sending
1804 a CR or LF within the header section, which means restricting the
1805 output of header fields to APIs that filter for bad octets and not
1806 allowing application servers to write directly to the protocol
1807 stream.
1809 11.2. Request Smuggling
1811 Request smuggling ([Linhart]) is a technique that exploits
1812 differences in protocol parsing among various recipients to hide
1813 additional requests (which might otherwise be blocked or disabled by
1814 policy) within an apparently harmless request. Like response
1815 splitting, request smuggling can lead to a variety of attacks on HTTP
1816 usage.
1818 This specification has introduced new requirements on request
1819 parsing, particularly with regard to message framing in Section 6.3,
1820 to reduce the effectiveness of request smuggling.
1822 11.3. Message Integrity
1824 HTTP does not define a specific mechanism for ensuring message
1825 integrity, instead relying on the error-detection ability of
1826 underlying transport protocols and the use of length or chunk-
1827 delimited framing to detect completeness. Historically, the lack of
1828 a single integrity mechanism has been justified by the informal
1829 nature of most HTTP communication. However, the prevalence of HTTP
1830 as an information access mechanism has resulted in its increasing use
1831 within environments where verification of message integrity is
1832 crucial.
1834 The mechanisms provided with the "https" scheme, such as
1835 authenticated encryption, provide protection against modification of
1836 messages. Care is needed however to ensure that connection closure
1837 cannot be used to truncate messages (see Section 9.8). User agents
1838 might refuse to accept incomplete messages or treat them specially.
1839 For example, a browser being used to view medical history or drug
1840 interaction information needs to indicate to the user when such
1841 information is detected by the protocol to be incomplete, expired, or
1842 corrupted during transfer. Such mechanisms might be selectively
1843 enabled via user agent extensions or the presence of message
1844 integrity metadata in a response.
1846 The "http" scheme provides no protection against accidental or
1847 malicious modification of messages.
1849 Extensions to the protocol might be used to mitigate the risk of
1850 unwanted modification of messages by intermediaries, even when the
1851 "https" scheme is used. Integrity might be assured by using message
1852 authentication codes or digital signatures that are selectively added
1853 to messages via extensible metadata fields.
1855 11.4. Message Confidentiality
1857 HTTP relies on underlying transport protocols to provide message
1858 confidentiality when that is desired. HTTP has been specifically
1859 designed to be independent of the transport protocol, such that it
1860 can be used over many forms of encrypted connection, with the
1861 selection of such transports being identified by the choice of URI
1862 scheme or within user agent configuration.
1864 The "https" scheme can be used to identify resources that require a
1865 confidential connection, as described in Section 4.2.2 of [HTTP].
1867 12. IANA Considerations
1869 The change controller for the following registrations is: "IETF
1870 (iesg@ietf.org) - Internet Engineering Task Force".
1872 12.1. Field Name Registration
1874 First, introduce the new "Hypertext Transfer Protocol (HTTP) Field
1875 Name Registry" at as
1876 described in Section 18.4 of [HTTP].
1878 Then, please update the registry with the field names listed in the
1879 table below:
1881 +===================+==========+======+============+
1882 | Field Name | Status | Ref. | Comments |
1883 +===================+==========+======+============+
1884 | Close | standard | 9.6 | (reserved) |
1885 +-------------------+----------+------+------------+
1886 | MIME-Version | standard | B.1 | |
1887 +-------------------+----------+------+------------+
1888 | Transfer-Encoding | standard | 6.1 | |
1889 +-------------------+----------+------+------------+
1891 Table 1
1893 12.2. Media Type Registration
1895 Please update the "Media Types" registry at
1896 with the registration
1897 information in Section 10.1 and Section 10.2 for the media types
1898 "message/http" and "application/http", respectively.
1900 12.3. Transfer Coding Registration
1902 Please update the "HTTP Transfer Coding Registry" at
1903 with the
1904 registration procedure of Section 7.3 and the content coding names
1905 summarized in the table below.
1907 +============+===============================+===========+
1908 | Name | Description | Reference |
1909 +============+===============================+===========+
1910 | chunked | Transfer in a series of | Section |
1911 | | chunks | 7.1 |
1912 +------------+-------------------------------+-----------+
1913 | compress | UNIX "compress" data format | Section |
1914 | | [Welch] | 7.2 |
1915 +------------+-------------------------------+-----------+
1916 | deflate | "deflate" compressed data | Section |
1917 | | ([RFC1951]) inside the "zlib" | 7.2 |
1918 | | data format ([RFC1950]) | |
1919 +------------+-------------------------------+-----------+
1920 | gzip | GZIP file format [RFC1952] | Section |
1921 | | | 7.2 |
1922 +------------+-------------------------------+-----------+
1923 | trailers | (reserved) | Section |
1924 | | | 12.3 |
1925 +------------+-------------------------------+-----------+
1926 | x-compress | Deprecated (alias for | Section |
1927 | | compress) | 7.2 |
1928 +------------+-------------------------------+-----------+
1929 | x-gzip | Deprecated (alias for gzip) | Section |
1930 | | | 7.2 |
1931 +------------+-------------------------------+-----------+
1933 Table 2
1935 | *Note:* the coding name "trailers" is reserved because its use
1936 | would conflict with the keyword "trailers" in the TE header
1937 | field (Section 10.1.4 of [HTTP]).
1939 12.4. ALPN Protocol ID Registration
1941 Please update the "TLS Application-Layer Protocol Negotiation (ALPN)
1942 Protocol IDs" registry at with the
1944 registration below:
1946 +==========+=============================+================+
1947 | Protocol | Identification Sequence | Reference |
1948 +==========+=============================+================+
1949 | HTTP/1.1 | 0x68 0x74 0x74 0x70 0x2f | (this |
1950 | | 0x31 0x2e 0x31 ("http/1.1") | specification) |
1951 +----------+-----------------------------+----------------+
1953 Table 3
1955 13. References
1957 13.1. Normative References
1959 [CACHING] Fielding, R., Ed., Nottingham, M., Ed., and J. Reschke,
1960 Ed., "HTTP Caching", Work in Progress, Internet-Draft,
1961 draft-ietf-httpbis-cache-17, 26 July 2021,
1962 .
1965 [HTTP] Fielding, R., Ed., Nottingham, M., Ed., and J. Reschke,
1966 Ed., "HTTP Semantics", Work in Progress, Internet-Draft,
1967 draft-ietf-httpbis-semantics-17, 26 July 2021,
1968 .
1971 [RFC1950] Deutsch, L.P. and J-L. Gailly, "ZLIB Compressed Data
1972 Format Specification version 3.3", RFC 1950,
1973 DOI 10.17487/RFC1950, May 1996,
1974 .
1976 [RFC1951] Deutsch, P., "DEFLATE Compressed Data Format Specification
1977 version 1.3", RFC 1951, DOI 10.17487/RFC1951, May 1996,
1978 .
1980 [RFC1952] Deutsch, P., Gailly, J-L., Adler, M., Deutsch, L.P., and
1981 G. Randers-Pehrson, "GZIP file format specification
1982 version 4.3", RFC 1952, DOI 10.17487/RFC1952, May 1996,
1983 .
1985 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
1986 Requirement Levels", BCP 14, RFC 2119,
1987 DOI 10.17487/RFC2119, March 1997,
1988 .
1990 [RFC5234] Crocker, D., Ed. and P. Overell, "Augmented BNF for Syntax
1991 Specifications: ABNF", STD 68, RFC 5234,
1992 DOI 10.17487/RFC5234, January 2008,
1993 .
1995 [RFC7405] Kyzivat, P., "Case-Sensitive String Support in ABNF",
1996 RFC 7405, DOI 10.17487/RFC7405, December 2014,
1997 .
1999 [RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC
2000 2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174,
2001 May 2017, .
2003 [TLS13] Rescorla, E., "The Transport Layer Security (TLS) Protocol
2004 Version 1.3", RFC 8446, DOI 10.17487/RFC8446, August 2018,
2005 .
2007 [URI] Berners-Lee, T., Fielding, R., and L. Masinter, "Uniform
2008 Resource Identifier (URI): Generic Syntax", STD 66,
2009 RFC 3986, DOI 10.17487/RFC3986, January 2005,
2010 .
2012 [USASCII] American National Standards Institute, "Coded Character
2013 Set -- 7-bit American Standard Code for Information
2014 Interchange", ANSI X3.4, 1986.
2016 [Welch] Welch, T. A., "A Technique for High-Performance Data
2017 Compression", IEEE Computer 17(6), June 1984.
2019 13.2. Informative References
2021 [Err4667] RFC Errata, Erratum ID 4667, RFC 7230,
2022 .
2024 [HTTP/1.0] Berners-Lee, T., Fielding, R.T., and H.F. Nielsen,
2025 "Hypertext Transfer Protocol -- HTTP/1.0", RFC 1945,
2026 DOI 10.17487/RFC1945, May 1996,
2027 .
2029 [Klein] Klein, A., "Divide and Conquer - HTTP Response Splitting,
2030 Web Cache Poisoning Attacks, and Related Topics", March
2031 2004, .
2034 [Linhart] Linhart, C., Klein, A., Heled, R., and S. Orrin, "HTTP
2035 Request Smuggling", June 2005,
2036 .
2039 [RFC2045] Freed, N. and N.S. Borenstein, "Multipurpose Internet Mail
2040 Extensions (MIME) Part One: Format of Internet Message
2041 Bodies", RFC 2045, DOI 10.17487/RFC2045, November 1996,
2042 .
2044 [RFC2046] Freed, N. and N. Borenstein, "Multipurpose Internet Mail
2045 Extensions (MIME) Part Two: Media Types", RFC 2046,
2046 DOI 10.17487/RFC2046, November 1996,
2047 .
2049 [RFC2049] Freed, N. and N.S. Borenstein, "Multipurpose Internet Mail
2050 Extensions (MIME) Part Five: Conformance Criteria and
2051 Examples", RFC 2049, DOI 10.17487/RFC2049, November 1996,
2052 .
2054 [RFC2068] Fielding, R., Gettys, J., Mogul, J., Nielsen, H., and T.
2055 Berners-Lee, "Hypertext Transfer Protocol -- HTTP/1.1",
2056 RFC 2068, DOI 10.17487/RFC2068, January 1997,
2057 .
2059 [RFC2557] Palme, F., Hopmann, A., Shelness, N., and E. Stefferud,
2060 "MIME Encapsulation of Aggregate Documents, such as HTML
2061 (MHTML)", RFC 2557, DOI 10.17487/RFC2557, March 1999,
2062 .
2064 [RFC5322] Resnick, P., "Internet Message Format", RFC 5322,
2065 DOI 10.17487/RFC5322, October 2008,
2066 .
2068 [RFC7230] Fielding, R., Ed. and J. F. Reschke, Ed., "Hypertext
2069 Transfer Protocol (HTTP/1.1): Message Syntax and Routing",
2070 RFC 7230, DOI 10.17487/RFC7230, June 2014,
2071 .
2073 [RFC8126] Cotton, M., Leiba, B., and T. Narten, "Guidelines for
2074 Writing an IANA Considerations Section in RFCs", BCP 26,
2075 RFC 8126, DOI 10.17487/RFC8126, June 2017,
2076 .
2078 Appendix A. Collected ABNF
2080 In the collected ABNF below, list rules are expanded as per
2081 Section 5.6.1.1 of [HTTP].
2083 BWS =
2085 HTTP-message = start-line CRLF *( field-line CRLF ) CRLF [
2086 message-body ]
2087 HTTP-name = %x48.54.54.50 ; HTTP
2088 HTTP-version = HTTP-name "/" DIGIT "." DIGIT
2090 OWS =
2092 RWS =
2094 Transfer-Encoding = [ transfer-coding *( OWS "," OWS transfer-coding
2095 ) ]
2097 absolute-URI =
2098 absolute-form = absolute-URI
2099 absolute-path =
2100 asterisk-form = "*"
2101 authority =
2102 authority-form = uri-host ":" port
2104 chunk = chunk-size [ chunk-ext ] CRLF chunk-data CRLF
2105 chunk-data = 1*OCTET
2106 chunk-ext = *( BWS ";" BWS chunk-ext-name [ BWS "=" BWS chunk-ext-val
2107 ] )
2108 chunk-ext-name = token
2109 chunk-ext-val = token / quoted-string
2110 chunk-size = 1*HEXDIG
2111 chunked-body = *chunk last-chunk trailer-section CRLF
2113 field-line = field-name ":" OWS field-value OWS
2114 field-name =
2115 field-value =
2117 last-chunk = 1*"0" [ chunk-ext ] CRLF
2119 message-body = *OCTET
2120 method = token
2122 obs-fold = OWS CRLF RWS
2123 obs-text =
2124 origin-form = absolute-path [ "?" query ]
2126 port =
2128 query =
2129 quoted-string =
2130 reason-phrase = 1*( HTAB / SP / VCHAR / obs-text )
2131 request-line = method SP request-target SP HTTP-version
2132 request-target = origin-form / absolute-form / authority-form /
2133 asterisk-form
2135 start-line = request-line / status-line
2136 status-code = 3DIGIT
2137 status-line = HTTP-version SP status-code SP [ reason-phrase ]
2139 token =
2140 trailer-section = *( field-line CRLF )
2141 transfer-coding =
2143 uri-host =
2145 Appendix B. Differences between HTTP and MIME
2147 HTTP/1.1 uses many of the constructs defined for the Internet Message
2148 Format [RFC5322] and the Multipurpose Internet Mail Extensions (MIME)
2149 [RFC2045] to allow a message body to be transmitted in an open
2150 variety of representations and with extensible fields. However, RFC
2151 2045 is focused only on email; applications of HTTP have many
2152 characteristics that differ from email; hence, HTTP has features that
2153 differ from MIME. These differences were carefully chosen to
2154 optimize performance over binary connections, to allow greater
2155 freedom in the use of new media types, to make date comparisons
2156 easier, and to acknowledge the practice of some early HTTP servers
2157 and clients.
2159 This appendix describes specific areas where HTTP differs from MIME.
2160 Proxies and gateways to and from strict MIME environments need to be
2161 aware of these differences and provide the appropriate conversions
2162 where necessary.
2164 B.1. MIME-Version
2166 HTTP is not a MIME-compliant protocol. However, messages can include
2167 a single MIME-Version header field to indicate what version of the
2168 MIME protocol was used to construct the message. Use of the MIME-
2169 Version header field indicates that the message is in full
2170 conformance with the MIME protocol (as defined in [RFC2045]).
2171 Senders are responsible for ensuring full conformance (where
2172 possible) when exporting HTTP messages to strict MIME environments.
2174 B.2. Conversion to Canonical Form
2176 MIME requires that an Internet mail body part be converted to
2177 canonical form prior to being transferred, as described in Section 4
2178 of [RFC2049], and that content with a type of "text" represent line
2179 breaks as CRLF, forbidding the use of CR or LF outside of line break
2180 sequences [RFC2046]. In contrast, HTTP does not care whether CRLF,
2181 bare CR, or bare LF are used to indicate a line break within content.
2183 A proxy or gateway from HTTP to a strict MIME environment ought to
2184 translate all line breaks within text media types to the RFC 2049
2185 canonical form of CRLF. Note, however, this might be complicated by
2186 the presence of a Content-Encoding and by the fact that HTTP allows
2187 the use of some charsets that do not use octets 13 and 10 to
2188 represent CR and LF, respectively.
2190 Conversion will break any cryptographic checksums applied to the
2191 original content unless the original content is already in canonical
2192 form. Therefore, the canonical form is recommended for any content
2193 that uses such checksums in HTTP.
2195 B.3. Conversion of Date Formats
2197 HTTP/1.1 uses a restricted set of date formats (Section 5.6.7 of
2198 [HTTP]) to simplify the process of date comparison. Proxies and
2199 gateways from other protocols ought to ensure that any Date header
2200 field present in a message conforms to one of the HTTP/1.1 formats
2201 and rewrite the date if necessary.
2203 B.4. Conversion of Content-Encoding
2205 MIME does not include any concept equivalent to HTTP/1.1's Content-
2206 Encoding header field. Since this acts as a modifier on the media
2207 type, proxies and gateways from HTTP to MIME-compliant protocols
2208 ought to either change the value of the Content-Type header field or
2209 decode the representation before forwarding the message. (Some
2210 experimental applications of Content-Type for Internet mail have used
2211 a media-type parameter of ";conversions=" to perform
2212 a function equivalent to Content-Encoding. However, this parameter
2213 is not part of the MIME standards).
2215 B.5. Conversion of Content-Transfer-Encoding
2217 HTTP does not use the Content-Transfer-Encoding field of MIME.
2218 Proxies and gateways from MIME-compliant protocols to HTTP need to
2219 remove any Content-Transfer-Encoding prior to delivering the response
2220 message to an HTTP client.
2222 Proxies and gateways from HTTP to MIME-compliant protocols are
2223 responsible for ensuring that the message is in the correct format
2224 and encoding for safe transport on that protocol, where "safe
2225 transport" is defined by the limitations of the protocol being used.
2226 Such a proxy or gateway ought to transform and label the data with an
2227 appropriate Content-Transfer-Encoding if doing so will improve the
2228 likelihood of safe transport over the destination protocol.
2230 B.6. MHTML and Line Length Limitations
2232 HTTP implementations that share code with MHTML [RFC2557]
2233 implementations need to be aware of MIME line length limitations.
2234 Since HTTP does not have this limitation, HTTP does not fold long
2235 lines. MHTML messages being transported by HTTP follow all
2236 conventions of MHTML, including line length limitations and folding,
2237 canonicalization, etc., since HTTP transfers message-bodies without
2238 modification and, aside from the "multipart/byteranges" type
2239 (Section 14.6 of [HTTP]), does not interpret the content or any MIME
2240 header lines that might be contained therein.
2242 Appendix C. Changes from previous RFCs
2244 C.1. Changes from HTTP/0.9
2246 Since HTTP/0.9 did not support header fields in a request, there is
2247 no mechanism for it to support name-based virtual hosts (selection of
2248 resource by inspection of the Host header field). Any server that
2249 implements name-based virtual hosts ought to disable support for
2250 HTTP/0.9. Most requests that appear to be HTTP/0.9 are, in fact,
2251 badly constructed HTTP/1.x requests caused by a client failing to
2252 properly encode the request-target.
2254 C.2. Changes from HTTP/1.0
2256 C.2.1. Multihomed Web Servers
2258 The requirements that clients and servers support the Host header
2259 field (Section 7.2 of [HTTP]), report an error if it is missing from
2260 an HTTP/1.1 request, and accept absolute URIs (Section 3.2) are among
2261 the most important changes defined by HTTP/1.1.
2263 Older HTTP/1.0 clients assumed a one-to-one relationship of IP
2264 addresses and servers; there was no other established mechanism for
2265 distinguishing the intended server of a request than the IP address
2266 to which that request was directed. The Host header field was
2267 introduced during the development of HTTP/1.1 and, though it was
2268 quickly implemented by most HTTP/1.0 browsers, additional
2269 requirements were placed on all HTTP/1.1 requests in order to ensure
2270 complete adoption. At the time of this writing, most HTTP-based
2271 services are dependent upon the Host header field for targeting
2272 requests.
2274 C.2.2. Keep-Alive Connections
2276 In HTTP/1.0, each connection is established by the client prior to
2277 the request and closed by the server after sending the response.
2278 However, some implementations implement the explicitly negotiated
2279 ("Keep-Alive") version of persistent connections described in
2280 Section 19.7.1 of [RFC2068].
2282 Some clients and servers might wish to be compatible with these
2283 previous approaches to persistent connections, by explicitly
2284 negotiating for them with a "Connection: keep-alive" request header
2285 field. However, some experimental implementations of HTTP/1.0
2286 persistent connections are faulty; for example, if an HTTP/1.0 proxy
2287 server doesn't understand Connection, it will erroneously forward
2288 that header field to the next inbound server, which would result in a
2289 hung connection.
2291 One attempted solution was the introduction of a Proxy-Connection
2292 header field, targeted specifically at proxies. In practice, this
2293 was also unworkable, because proxies are often deployed in multiple
2294 layers, bringing about the same problem discussed above.
2296 As a result, clients are encouraged not to send the Proxy-Connection
2297 header field in any requests.
2299 Clients are also encouraged to consider the use of Connection: keep-
2300 alive in requests carefully; while they can enable persistent
2301 connections with HTTP/1.0 servers, clients using them will need to
2302 monitor the connection for "hung" requests (which indicate that the
2303 client ought to stop sending the header field), and this mechanism
2304 ought not be used by clients at all when a proxy is being used.
2306 C.2.3. Introduction of Transfer-Encoding
2308 HTTP/1.1 introduces the Transfer-Encoding header field (Section 6.1).
2309 Transfer codings need to be decoded prior to forwarding an HTTP
2310 message over a MIME-compliant protocol.
2312 C.3. Changes from RFC 7230
2314 Most of the sections introducing HTTP's design goals, history,
2315 architecture, conformance criteria, protocol versioning, URIs,
2316 message routing, and header fields have been moved to [HTTP]. This
2317 document has been reduced to just the messaging syntax and connection
2318 management requirements specific to HTTP/1.1.
2320 Bare CRs have been prohibited outside of content. (Section 2.2)
2322 The ABNF definition of authority-form has changed from the more
2323 general authority component of a URI (in which port is optional) to
2324 the specific host:port format that is required by CONNECT.
2325 (Section 3.2.3)
2327 Required recipients to avoid smuggling/splitting attacks when
2328 processing an ambiguous message framing. (Section 6.1)
2330 In the ABNF for chunked extensions, re-introduced (bad) whitespace
2331 around ";" and "=". Whitespace was removed in [RFC7230], but that
2332 change was found to break existing implementations (see [Err4667]).
2333 (Section 7.1.1)
2335 Trailer field semantics now transcend the specifics of chunked
2336 encoding. The decoding algorithm for chunked (Section 7.1.3) has
2337 been updated to encourage storage/forwarding of trailer fields
2338 separately from the header section, to only allow merging into the
2339 header section if the recipient knows the corresponding field
2340 definition permits and defines how to merge, and otherwise to discard
2341 the trailer fields instead of merging. The trailer part is now
2342 called the trailer section to be more consistent with the header
2343 section and more distinct from a body part. (Section 7.1.2)
2345 Disallowed transfer coding parameters called "q" in order to avoid
2346 conflicts with the use of ranks in the TE header field.
2347 (Section 7.3)
2349 Appendix D. Change Log
2351 This section is to be removed before publishing as an RFC.
2353 D.1. Between RFC7230 and draft 00
2355 The changes were purely editorial:
2357 * Change boilerplate and abstract to indicate the "draft" status,
2358 and update references to ancestor specifications.
2360 * Adjust historical notes.
2362 * Update links to sibling specifications.
2364 * Replace sections listing changes from RFC 2616 by new empty
2365 sections referring to RFC 723x.
2367 * Remove acknowledgements specific to RFC 723x.
2369 * Move "Acknowledgements" to the very end and make them unnumbered.
2371 D.2. Since draft-ietf-httpbis-messaging-00
2373 The changes in this draft are editorial, with respect to HTTP as a
2374 whole, to move all core HTTP semantics into [HTTP]:
2376 * Moved introduction, architecture, conformance, and ABNF extensions
2377 from RFC 7230 (Messaging) to semantics [HTTP].
2379 * Moved discussion of MIME differences from RFC 7231 (Semantics) to
2380 Appendix B since they mostly cover transforming 1.1 messages.
2382 * Moved all extensibility tips, registration procedures, and
2383 registry tables from the IANA considerations to normative
2384 sections, reducing the IANA considerations to just instructions
2385 that will be removed prior to publication as an RFC.
2387 D.3. Since draft-ietf-httpbis-messaging-01
2389 * Cite RFC 8126 instead of RFC 5226 ()
2392 * Resolved erratum 4779, no change needed here
2393 (,
2394 )
2396 * In Section 7, fixed prose claiming transfer parameters allow bare
2397 names (,
2398 )
2400 * Resolved erratum 4225, no change needed here
2401 (,
2402 )
2404 * Replace "response code" with "response status code"
2405 (,
2406 )
2408 * In Section 9.3, clarify statement about HTTP/1.0 keep-alive
2409 (,
2410 )
2412 * In Section 7.1.1, re-introduce (bad) whitespace around ";" and "="
2413 (,
2414 , )
2417 * In Section 7.3, state that transfer codings should not use
2418 parameters named "q" (, )
2421 * In Section 7, mark coding name "trailers" as reserved in the IANA
2422 registry ()
2424 D.4. Since draft-ietf-httpbis-messaging-02
2426 * In Section 4, explain why the reason phrase should be ignored by
2427 clients ().
2429 * Add Section 9.2 to explain how request/response correlation is
2430 performed ()
2432 D.5. Since draft-ietf-httpbis-messaging-03
2434 * In Section 9.2, caution against treating data on a connection as
2435 part of a not-yet-issued request ()
2438 * In Section 7, remove the predefined codings from the ABNF and make
2439 it generic instead ()
2442 * Use RFC 7405 ABNF notation for case-sensitive string constants
2443 ()
2445 D.6. Since draft-ietf-httpbis-messaging-04
2447 * In Section 7.8 of [HTTP], clarify that protocol-name is to be
2448 matched case-insensitively ()
2451 * In Section 5.2, add leading optional whitespace to obs-fold ABNF
2452 (,
2453 )
2455 * In Section 4, add clarifications about empty reason phrases
2456 ()
2458 * Move discussion of retries from Section 9.3.1 into [HTTP]
2459 ()
2461 D.7. Since draft-ietf-httpbis-messaging-05
2463 * In Section 7.1.2, the trailer part has been renamed the trailer
2464 section (for consistency with the header section) and trailers are
2465 no longer merged as header fields by default, but rather can be
2466 discarded, kept separate from header fields, or merged with header
2467 fields only if understood and defined as being mergeable
2468 ()
2470 * In Section 2.1 and related Sections, move the trailing CRLF from
2471 the line grammars into the message format
2472 ()
2474 * Moved Section 2.3 down ()
2477 * In Section 7.8 of [HTTP], use 'websocket' instead of 'HTTP/2.0' in
2478 examples ()
2480 * Move version non-specific text from Section 6 into semantics as
2481 "payload" ()
2483 * In Section 9.8, add text from RFC 2818
2484 ()
2486 D.8. Since draft-ietf-httpbis-messaging-06
2488 * In Section 12.4, update the ALPN protocol ID for HTTP/1.1
2489 ()
2491 * In Section 5, align with updates to field terminology in semantics
2492 ()
2494 * In Section 7.6.1 of [HTTP], clarify that new connection options
2495 indeed need to be registered ()
2498 * In Section 1.1, reference RFC 8174 as well
2499 ()
2501 D.9. Since draft-ietf-httpbis-messaging-07
2502 * Move TE: trailers into [HTTP] ()
2505 * In Section 6.3, adjust requirements for handling multiple content-
2506 length values ()
2508 * Throughout, replace "effective request URI" with "target URI"
2509 ()
2511 * In Section 6.1, don't claim Transfer-Encoding is supported by
2512 HTTP/2 or later ()
2514 D.10. Since draft-ietf-httpbis-messaging-08
2516 * In Section 2.2, disallow bare CRs ()
2519 * Appendix A now uses the sender variant of the "#" list expansion
2520 ()
2522 * In Section 5, adjust IANA "Close" entry for new registry format
2523 ()
2525 D.11. Since draft-ietf-httpbis-messaging-09
2527 * Switch to xml2rfc v3 mode for draft generation
2528 ()
2530 D.12. Since draft-ietf-httpbis-messaging-10
2532 * In Section 6.3, note that TCP half-close does not delimit a
2533 request; talk about corresponding server-side behaviour in
2534 Section 9.6 ()
2536 * Moved requirements specific to HTTP/1.1 from [HTTP] into
2537 Section 3.2 ()
2539 * In Section 6.1 (Transfer-Encoding), adjust ABNF to allow empty
2540 lists ()
2542 * In Section 9.7, add text from RFC 2818
2543 ()
2545 * Moved definitions of "TE" and "Upgrade" into [HTTP]
2546 ()
2548 * Moved definition of "Connection" into [HTTP]
2549 ()
2551 D.13. Since draft-ietf-httpbis-messaging-11
2553 * Move IANA Upgrade Token Registry instructions to [HTTP]
2554 ()
2556 D.14. Since draft-ietf-httpbis-messaging-12
2558 * Moved content of history appendix to Semantics
2559 ()
2561 * Moved note about "close" being reserved as field name to
2562 Section 9.3 ()
2564 * Moved table of transfer codings into Section 12.3
2565 ()
2567 * In Section 13.2, updated the URI for the [Linhart] paper
2568 ()
2570 * Changed document title to just "HTTP/1.1"
2571 ()
2573 * In Section 7, moved transfer-coding ABNF to Section 10.1.4 of
2574 [HTTP] ()
2576 * Changed to using "payload data" when defining requirements about
2577 the data being conveyed within a message, instead of the terms
2578 "payload body" or "response body" or "representation body", since
2579 they often get confused with the HTTP/1.1 message body (which
2580 includes transfer coding) ()
2583 D.15. Since draft-ietf-httpbis-messaging-13
2585 * In Section 6.3, clarify that a message needs to be checked for
2586 both Content-Length and Transfer-Encoding, before processing
2587 Transfer-Encoding, and that ought to be treated as an error, but
2588 an intermediary can choose to forward the message downstream after
2589 removing the Content-Length and processing the Transfer-Encoding
2590 ()
2592 * Changed to using "content" instead of "payload" or "payload data"
2593 to avoid confusion with the payload of version-specific messaging
2594 frames ()
2596 D.16. Since draft-ietf-httpbis-messaging-14
2597 * In Section 9.6, define the close connection option, since its
2598 definition was removed from the Connection header field for being
2599 specific to 1.1 ()
2601 * In Section 3.3, clarify how the target URI is reconstructed when
2602 the request-target is not in absolute-form and highlight risk in
2603 selecting a default host ()
2606 * In Section 7.1, clarify large chunk handling issues
2607 ()
2609 * In Section 2.2, explicitly close the connection after sending a
2610 400 ()
2612 * In Section 2.3, refine version requirements for intermediaries
2613 ()
2615 * In Section 7.1.3, don't remove the Trailer header field
2616 ()
2618 * In Section 3.2.3, changed the ABNF definition of authority-form
2619 from the authority component (in which port is optional) to the
2620 host:port format that has always been required by CONNECT
2621 ()
2623 D.17. Since draft-ietf-httpbis-messaging-15
2625 * None.
2627 D.18. Since draft-ietf-httpbis-messaging-16
2629 This draft addresses mostly editorial issues raised during or past
2630 IETF Last Call; see for a summary.
2633 Furthermore:
2635 * In Section 6.1, require recipients to avoid smuggling/splitting
2636 attacks when processing an ambiguous message framing
2637 ()
2639 Acknowledgements
2641 See Appendix "Acknowledgements" of [HTTP].
2643 Index
2645 A C D F G H M O R T X
2647 A
2649 absolute-form (of request-target) Section 3.2.2
2650 application/http Media Type Section 10.2
2651 asterisk-form (of request-target) Section 3.2.4
2652 authority-form (of request-target) Section 3.2.3
2654 C
2656 Connection header field Section 9.6
2657 Content-Length header field Section 6.2
2658 Content-Transfer-Encoding header field Appendix B.5
2659 chunked (Coding Format) Section 6.1; Section 6.3
2660 chunked (transfer coding) Section 7.1
2661 close Section 9.3; Section 9.6
2662 compress (transfer coding) Section 7.2
2664 D
2666 deflate (transfer coding) Section 7.2
2668 F
2670 Fields
2671 Close Section 9.6, Paragraph 4
2672 MIME-Version Appendix B.1
2673 Transfer-Encoding Section 6.1
2675 G
2677 Grammar
2678 ALPHA Section 1.2
2679 CR Section 1.2
2680 CRLF Section 1.2
2681 CTL Section 1.2
2682 DIGIT Section 1.2
2683 DQUOTE Section 1.2
2684 HEXDIG Section 1.2
2685 HTAB Section 1.2
2686 HTTP-message Section 2.1
2687 HTTP-name Section 2.3
2688 HTTP-version Section 2.3
2689 LF Section 1.2
2690 OCTET Section 1.2
2691 SP Section 1.2
2692 Transfer-Encoding Section 6.1
2693 VCHAR Section 1.2
2694 absolute-form Section 3.2; Section 3.2.2
2695 asterisk-form Section 3.2; Section 3.2.4
2696 authority-form Section 3.2; Section 3.2.3
2697 chunk Section 7.1
2698 chunk-data Section 7.1
2699 chunk-ext Section 7.1; Section 7.1.1
2700 chunk-ext-name Section 7.1.1
2701 chunk-ext-val Section 7.1.1
2702 chunk-size Section 7.1
2703 chunked-body Section 7.1
2704 field-line Section 5; Section 7.1.2
2705 field-name Section 5
2706 field-value Section 5
2707 last-chunk Section 7.1
2708 message-body Section 6
2709 method Section 3.1
2710 obs-fold Section 5.2
2711 origin-form Section 3.2; Section 3.2.1
2712 reason-phrase Section 4
2713 request-line Section 3
2714 request-target Section 3.2
2715 start-line Section 2.1
2716 status-code Section 4
2717 status-line Section 4
2718 trailer-section Section 7.1; Section 7.1.2
2719 gzip (transfer coding) Section 7.2
2721 H
2723 Header Fields
2724 MIME-Version Appendix B.1
2725 Transfer-Encoding Section 6.1
2726 header line Section 2.1
2727 header section Section 2.1
2728 headers Section 2.1
2730 M
2732 MIME-Version header field Appendix B.1
2733 Media Type
2734 application/http Section 10.2
2735 message/http Section 10.1
2736 message/http Media Type Section 10.1
2737 method Section 3.1
2739 O
2741 origin-form (of request-target) Section 3.2.1
2743 R
2745 request-target Section 3.2
2747 T
2749 Transfer-Encoding header field Section 6.1
2751 X
2753 x-compress (transfer coding) Section 7.2
2754 x-gzip (transfer coding) Section 7.2
2756 Authors' Addresses
2758 Roy T. Fielding (editor)
2759 Adobe
2760 345 Park Ave
2761 San Jose, CA 95110
2762 United States of America
2764 Email: fielding@gbiv.com
2765 URI: https://roy.gbiv.com/
2767 Mark Nottingham (editor)
2768 Fastly
2769 Prahran VIC
2770 Australia
2772 Email: mnot@mnot.net
2773 URI: https://www.mnot.net/
2775 Julian Reschke (editor)
2776 greenbytes GmbH
2777 Hafenweg 16
2778 48155 Münster
2779 Germany
2781 Email: julian.reschke@greenbytes.de
2782 URI: https://greenbytes.de/tech/webdav/