frankenRFC723x_msg.txt   draft-ietf-httpbis-messaging-12.txt 
Internet Engineering Task Force (IETF) R. Fielding, Ed. HTTP Working Group R. Fielding, Ed.
Request for Comments: 7230 Adobe Internet-Draft Adobe
Obsoletes: 2145, 2616 J. Reschke, Ed. Obsoletes: 7230 (if approved) M. Nottingham, Ed.
Updates: 2817, 2818 greenbytes Intended status: Standards Track Fastly
Category: Standards Track June 2014 Expires: April 5, 2021 J. Reschke, Ed.
ISSN: 2070-1721 greenbytes
October 2, 2020
Hypertext Transfer Protocol (HTTP/1.1): Message Syntax and Routing HTTP/1.1 Messaging
draft-ietf-httpbis-messaging-12
Abstract Abstract
The Hypertext Transfer Protocol (HTTP) is a stateless application- The Hypertext Transfer Protocol (HTTP) is a stateless application-
level protocol for distributed, collaborative, hypertext information level protocol for distributed, collaborative, hypertext information
systems. This document provides an overview of HTTP architecture and systems. This document specifies the HTTP/1.1 message syntax,
its associated terminology, defines the "http" and "https" Uniform message parsing, connection management, and related security
Resource Identifier (URI) schemes, defines the HTTP/1.1 message concerns.
syntax and parsing requirements, and describes related security
concerns for implementations. This document obsoletes portions of RFC 7230.
Editorial Note Editorial Note
This note is not in the original RFC. This note is to be removed before publishing as an RFC.
The purpose of this document is to produce diffs that show just the Discussion of this draft takes place on the HTTP working group
changes from text in the original RFCs that were input for http-core. mailing list (ietf-http-wg@w3.org), which is archived at
Hence, the frankenRFC documents show all of the original text (including <https://lists.w3.org/Archives/Public/ietf-http-wg/>.
stuff that has been deleted) plus some new text [in brackets] to anchor
context, rearranged to minimize the resulting diffs when compared to the
most recently published version of draft-ietf-httpbis-messaging.
After this document is updated to match any reorg changes in the latest Working Group information can be found at <https://httpwg.org/>;
version, the franken diffs are saved and published in this directory as source code and issues list for this draft can be found at
diff_messaging_frfc_to_NN.html (where NN is the I-D draft revision) <https://github.com/httpwg/http-core>.
The changes in this draft are summarized in Appendix D.13.
Status of This Memo Status of This Memo
This is an Internet Standards Track document. This Internet-Draft is submitted in full conformance with the
provisions of BCP 78 and BCP 79.
This document is a product of the Internet Engineering Task Force Internet-Drafts are working documents of the Internet Engineering
(IETF). It represents the consensus of the IETF community. It has Task Force (IETF). Note that other groups may also distribute
received public review and has been approved for publication by the working documents as Internet-Drafts. The list of current Internet-
Internet Engineering Steering Group (IESG). Further information on Drafts is at https://datatracker.ietf.org/drafts/current/.
Internet Standards is available in Section 2 of RFC 5741.
Information about the current status of this document, any errata, Internet-Drafts are draft documents valid for a maximum of six months
and how to provide feedback on it may be obtained at and may be updated, replaced, or obsoleted by other documents at any
http://www.rfc-editor.org/info/rfc7230. time. It is inappropriate to use Internet-Drafts as reference
material or to cite them other than as "work in progress."
This Internet-Draft will expire on April 5, 2021.
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Table of Contents Table of Contents
1. Introduction ....................................................5 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 4
1.1. Requirements Notation ......................................6 1.1. Requirements Notation . . . . . . . . . . . . . . . . . . 5
1.2. Syntax Notation ............................................6 1.2. Syntax Notation . . . . . . . . . . . . . . . . . . . . . 5
2. Architecture ....................................................6 2. Message . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
2.1. Client/Server Messaging ....................................7 2.1. Message Format . . . . . . . . . . . . . . . . . . . . . 6
2.2. Implementation Diversity ...................................8 2.2. Message Parsing . . . . . . . . . . . . . . . . . . . . . 7
2.3. Intermediaries .............................................9 2.3. HTTP Version . . . . . . . . . . . . . . . . . . . . . . 8
2.4. Caches ....................................................11 3. Request Line . . . . . . . . . . . . . . . . . . . . . . . . 9
2.5. Conformance and Error Handling ............................12 3.1. Method . . . . . . . . . . . . . . . . . . . . . . . . . 10
2.6. Protocol Versioning .......................................13 3.2. Request Target . . . . . . . . . . . . . . . . . . . . . 10
2.7. Uniform Resource Identifiers ..............................16 3.2.1. origin-form . . . . . . . . . . . . . . . . . . . . . 11
2.7.1. http URI Scheme ....................................17 3.2.2. absolute-form . . . . . . . . . . . . . . . . . . . . 11
2.7.2. https URI Scheme ...................................18 3.2.3. authority-form . . . . . . . . . . . . . . . . . . . 12
2.7.3. http and https URI Normalization and Comparison ....19 3.2.4. asterisk-form . . . . . . . . . . . . . . . . . . . . 12
3. Message Format .................................................19 3.3. Reconstructing the Target URI . . . . . . . . . . . . . . 13
3.1. Start Line ................................................20 4. Status Line . . . . . . . . . . . . . . . . . . . . . . . . . 14
3.1.1. Request Line .......................................21 5. Field Syntax . . . . . . . . . . . . . . . . . . . . . . . . 15
3.1.2. Status Line ........................................22 5.1. Field Line Parsing . . . . . . . . . . . . . . . . . . . 16
3.2. Header Fields .............................................22 5.2. Obsolete Line Folding . . . . . . . . . . . . . . . . . . 17
3.2.1. Field Extensibility ................................23 6. Message Body . . . . . . . . . . . . . . . . . . . . . . . . 17
3.2.2. Field Order ........................................23 6.1. Transfer-Encoding . . . . . . . . . . . . . . . . . . . . 18
3.2.3. Whitespace .........................................24 6.2. Content-Length . . . . . . . . . . . . . . . . . . . . . 19
3.2.4. Field Parsing ......................................25 6.3. Message Body Length . . . . . . . . . . . . . . . . . . . 20
3.2.5. Field Limits .......................................26 7. Transfer Codings . . . . . . . . . . . . . . . . . . . . . . 22
3.2.6. Field Value Components .............................27 7.1. Chunked Transfer Coding . . . . . . . . . . . . . . . . . 23
3.3. Message Body ..............................................28 7.1.1. Chunk Extensions . . . . . . . . . . . . . . . . . . 24
3.3.1. Transfer-Encoding ..................................28 7.1.2. Chunked Trailer Section . . . . . . . . . . . . . . . 25
3.3.2. Content-Length .....................................30 7.1.3. Decoding Chunked . . . . . . . . . . . . . . . . . . 25
3.3.3. Message Body Length ................................32 7.2. Transfer Codings for Compression . . . . . . . . . . . . 26
3.4. Handling Incomplete Messages ..............................34 7.3. Transfer Coding Registry . . . . . . . . . . . . . . . . 26
3.5. Message Parsing Robustness ................................34 7.4. Negotiating Transfer Codings . . . . . . . . . . . . . . 27
4. Transfer Codings ...............................................35 8. Handling Incomplete Messages . . . . . . . . . . . . . . . . 27
4.1. Chunked Transfer Coding ...................................36 9. Connection Management . . . . . . . . . . . . . . . . . . . . 28
4.1.1. Chunk Extensions ...................................36 9.1. Establishment . . . . . . . . . . . . . . . . . . . . . . 28
4.1.2. Chunked Trailer Part ...............................37 9.2. Associating a Response to a Request . . . . . . . . . . . 29
4.1.3. Decoding Chunked ...................................38 9.3. Persistence . . . . . . . . . . . . . . . . . . . . . . . 29
4.2. Compression Codings .......................................38 9.3.1. Retrying Requests . . . . . . . . . . . . . . . . . . 30
4.2.1. Compress Coding ....................................38 9.3.2. Pipelining . . . . . . . . . . . . . . . . . . . . . 30
4.2.2. Deflate Coding .....................................38 9.4. Concurrency . . . . . . . . . . . . . . . . . . . . . . . 31
4.2.3. Gzip Coding ........................................39 9.5. Failures and Timeouts . . . . . . . . . . . . . . . . . . 32
4.3. TE ........................................................39 9.6. Tear-down . . . . . . . . . . . . . . . . . . . . . . . . 32
4.4. Trailer ...................................................40 9.7. TLS Connection Initiation . . . . . . . . . . . . . . . . 34
5. Message Routing ................................................40 9.8. TLS Connection Closure . . . . . . . . . . . . . . . . . 34
5.1. Identifying a Target Resource .............................40 10. Enclosing Messages as Data . . . . . . . . . . . . . . . . . 35
5.2. Connecting Inbound ........................................41 10.1. Media Type message/http . . . . . . . . . . . . . . . . 35
5.3. Request Target ............................................41 10.2. Media Type application/http . . . . . . . . . . . . . . 36
5.3.1. origin-form ........................................42 11. Security Considerations . . . . . . . . . . . . . . . . . . . 37
5.3.2. absolute-form ......................................42 11.1. Response Splitting . . . . . . . . . . . . . . . . . . . 37
5.3.3. authority-form .....................................43 11.2. Request Smuggling . . . . . . . . . . . . . . . . . . . 38
5.3.4. asterisk-form ......................................43 11.3. Message Integrity . . . . . . . . . . . . . . . . . . . 38
5.4. Host ......................................................44 11.4. Message Confidentiality . . . . . . . . . . . . . . . . 39
5.5. Effective Request URI .....................................45 12. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 39
5.6. Associating a Response to a Request .......................46 12.1. Field Name Registration . . . . . . . . . . . . . . . . 39
5.7. Message Forwarding ........................................47 12.2. Media Type Registration . . . . . . . . . . . . . . . . 39
5.7.1. Via ................................................47 12.3. Transfer Coding Registration . . . . . . . . . . . . . . 40
5.7.2. Transformations ....................................49 12.4. ALPN Protocol ID Registration . . . . . . . . . . . . . 40
6. Connection Management ..........................................50 13. References . . . . . . . . . . . . . . . . . . . . . . . . . 40
6.1. Connection ................................................51 13.1. Normative References . . . . . . . . . . . . . . . . . . 40
6.2. Establishment .............................................52 13.2. Informative References . . . . . . . . . . . . . . . . . 41
6.3. Persistence ...............................................52 Appendix A. Collected ABNF . . . . . . . . . . . . . . . . . . . 43
6.3.1. Retrying Requests ..................................53 Appendix B. Differences between HTTP and MIME . . . . . . . . . 44
6.3.2. Pipelining .........................................54 B.1. MIME-Version . . . . . . . . . . . . . . . . . . . . . . 45
6.4. Concurrency ...............................................55 B.2. Conversion to Canonical Form . . . . . . . . . . . . . . 45
6.5. Failures and Timeouts .....................................55 B.3. Conversion of Date Formats . . . . . . . . . . . . . . . 45
6.6. Tear-down .................................................56 B.4. Conversion of Content-Encoding . . . . . . . . . . . . . 46
6.7. Upgrade ...................................................57 B.5. Conversion of Content-Transfer-Encoding . . . . . . . . . 46
7. ABNF List Extension: #rule .....................................59 B.6. MHTML and Line Length Limitations . . . . . . . . . . . . 46
8. IANA Considerations ............................................61 Appendix C. HTTP Version History . . . . . . . . . . . . . . . . 46
8.1. Header Field Registration .................................61 C.1. Changes from HTTP/1.0 . . . . . . . . . . . . . . . . . . 47
8.2. URI Scheme Registration ...................................62 C.1.1. Multihomed Web Servers . . . . . . . . . . . . . . . 47
8.3. Internet Media Type Registration ..........................62 C.1.2. Keep-Alive Connections . . . . . . . . . . . . . . . 48
8.3.1. Internet Media Type message/http ...................62 C.1.3. Introduction of Transfer-Encoding . . . . . . . . . . 48
8.3.2. Internet Media Type application/http ...............63 C.2. Changes from RFC 7230 . . . . . . . . . . . . . . . . . . 49
8.4. Transfer Coding Registry ..................................64 Appendix D. Change Log . . . . . . . . . . . . . . . . . . . . . 49
8.4.1. Procedure ..........................................65 D.1. Between RFC7230 and draft 00 . . . . . . . . . . . . . . 49
8.4.2. Registration .......................................65 D.2. Since draft-ietf-httpbis-messaging-00 . . . . . . . . . . 50
8.5. Content Coding Registration ...............................66 D.3. Since draft-ietf-httpbis-messaging-01 . . . . . . . . . . 50
8.6. Upgrade Token Registry ....................................66 D.4. Since draft-ietf-httpbis-messaging-02 . . . . . . . . . . 51
8.6.1. Procedure ..........................................66 D.5. Since draft-ietf-httpbis-messaging-03 . . . . . . . . . . 51
8.6.2. Upgrade Token Registration .........................67 D.6. Since draft-ietf-httpbis-messaging-04 . . . . . . . . . . 51
9. Security Considerations ........................................67 D.7. Since draft-ietf-httpbis-messaging-05 . . . . . . . . . . 52
9.1. Establishing Authority ....................................67 D.8. Since draft-ietf-httpbis-messaging-06 . . . . . . . . . . 52
9.2. Risks of Intermediaries ...................................68 D.9. Since draft-ietf-httpbis-messaging-07 . . . . . . . . . . 52
9.3. Attacks via Protocol Element Length .......................69 D.10. Since draft-ietf-httpbis-messaging-08 . . . . . . . . . . 53
9.4. Response Splitting ........................................69 D.11. Since draft-ietf-httpbis-messaging-09 . . . . . . . . . . 53
9.5. Request Smuggling .........................................70 D.12. Since draft-ietf-httpbis-messaging-10 . . . . . . . . . . 53
9.6. Message Integrity .........................................70 D.13. Since draft-ietf-httpbis-messaging-11 . . . . . . . . . . 53
9.7. Message Confidentiality ...................................71 Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . . . 54
9.8. Privacy of Server Log Information .........................71 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 54
10. Acknowledgments ...............................................72
11. References ....................................................74
11.1. Normative References .....................................74
11.2. Informative References ...................................75
Appendix A. HTTP Version History ..................................78
A.1. Changes from HTTP/1.0 ....................................78
A.1.1. Multihomed Web Servers ............................78
A.1.2. Keep-Alive Connections ............................79
A.1.3. Introduction of Transfer-Encoding .................79
A.2. Changes from RFC 2616 ....................................80
Appendix B. Collected ABNF ........................................82
Index .............................................................85
1. Introduction 1. Introduction
The Hypertext Transfer Protocol (HTTP) is a stateless application- The Hypertext Transfer Protocol (HTTP) is a stateless application-
level request/response protocol that uses extensible semantics and level request/response protocol that uses extensible semantics and
self-descriptive message payloads for flexible interaction with self-descriptive messages for flexible interaction with network-based
network-based hypertext information systems. This document is the hypertext information systems. HTTP is defined by a series of
first in a series of documents that collectively form the HTTP/1.1 documents that collectively form the HTTP/1.1 specification:
specification:
1. "Message Syntax and Routing" (this document)
2. "Semantics and Content" [RFC7231]
3. "Conditional Requests" [RFC7232]
4. "Range Requests" [RFC7233]
5. "Caching" [RFC7234]
6. "Authentication" [RFC7235] o "HTTP Semantics" [Semantics]
This HTTP/1.1 specification obsoletes RFC 2616 and RFC 2145 (on HTTP o "HTTP Caching" [Caching]
versioning). This specification also updates the use of CONNECT to
establish a tunnel, previously defined in RFC 2817, and defines the
"https" URI scheme that was described informally in RFC 2818.
This document describes the architectural elements that are used or o "HTTP/1.1 Messaging" (this document)
referred to in HTTP, defines the "http" and "https" URI schemes, This document defines HTTP/1.1 message syntax and framing
describes overall network operation and connection management, and requirements and their associated connection management. Our goal is
defines HTTP message framing and forwarding requirements. Our goal to define all of the mechanisms necessary for HTTP/1.1 message
is to define all of the mechanisms necessary for HTTP message
handling that are independent of message semantics, thereby defining handling that are independent of message semantics, thereby defining
the complete set of requirements for message parsers and message- the complete set of requirements for message parsers and message-
forwarding intermediaries. forwarding intermediaries.
This document obsoletes the portions of RFC 7230 related to HTTP/1.1
messaging and connection management, with the changes being
summarized in Appendix C.2. The other parts of RFC 7230 are
obsoleted by "HTTP Semantics" [Semantics].
1.1. Requirements Notation 1.1. Requirements Notation
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and
document are to be interpreted as described in [RFC2119]. "OPTIONAL" in this document are to be interpreted as described in BCP
14 [RFC2119] [RFC8174] when, and only when, they appear in all
capitals, as shown here.
Conformance criteria and considerations regarding error handling are Conformance criteria and considerations regarding error handling are
defined in Section 2.5. defined in Section 2 of [Semantics].
1.2. Syntax Notation 1.2. Syntax Notation
This specification uses the Augmented Backus-Naur Form (ABNF) This specification uses the Augmented Backus-Naur Form (ABNF)
notation of [RFC5234] with a list extension, defined in Section 7, notation of [RFC5234], extended with the notation for case-
that allows for compact definition of comma-separated lists using a sensitivity in strings defined in [RFC7405].
'#' operator (similar to how the '*' operator indicates repetition).
Appendix B shows the collected grammar with all list operators It also uses a list extension, defined in Section 5.7.1 of
expanded to standard ABNF notation. [Semantics], that allows for compact definition of comma-separated
lists using a '#' operator (similar to how the '*' operator indicates
repetition). Appendix A shows the collected grammar with all list
operators expanded to standard ABNF notation.
As a convention, ABNF rule names prefixed with "obs-" denote As a convention, ABNF rule names prefixed with "obs-" denote
"obsolete" grammar rules that appear for historical reasons. "obsolete" grammar rules that appear for historical reasons.
The following core rules are included by reference, as defined in The following core rules are included by reference, as defined in
[RFC5234], Appendix B.1: ALPHA (letters), CR (carriage return), CRLF [RFC5234], Appendix B.1: ALPHA (letters), CR (carriage return), CRLF
(CR LF), CTL (controls), DIGIT (decimal 0-9), DQUOTE (double quote), (CR LF), CTL (controls), DIGIT (decimal 0-9), DQUOTE (double quote),
HEXDIG (hexadecimal 0-9/A-F/a-f), HTAB (horizontal tab), LF (line HEXDIG (hexadecimal 0-9/A-F/a-f), HTAB (horizontal tab), LF (line
feed), OCTET (any 8-bit sequence of data), SP (space), and VCHAR (any feed), OCTET (any 8-bit sequence of data), SP (space), and VCHAR (any
visible [USASCII] character). visible [USASCII] character).
The rules below are defined in [RFC7230]: The rules below are defined in [Semantics]:
BWS = <BWS, see [RFC7230], Section 3.2.3> BWS = <BWS, see [Semantics], Section 5.7.3>
OWS = <OWS, see [RFC7230], Section 3.2.3> OWS = <OWS, see [Semantics], Section 5.7.3>
RWS = <RWS, see [RFC7230], Section 3.2.3> RWS = <RWS, see [Semantics], Section 5.7.3>
URI-reference = <URI-reference, see [RFC7230], Section 2.7> absolute-URI = <absolute-URI, see [RFC3986], Section 4.3>
absolute-URI = <absolute-URI, see [RFC7230], Section 2.7> absolute-path = <absolute-path, see [Semantics], Section 4>
comment = <comment, see [RFC7230], Section 3.2.6> authority = <authority, see [RFC3986], Section 3.2>
field-name = <comment, see [RFC7230], Section 3.2> comment = <comment, see [Semantics], Section 5.7.5>
partial-URI = <partial-URI, see [RFC7230], Section 2.7> field-name = <field-name, see [Semantics], Section 5.4.3>
quoted-string = <quoted-string, see [RFC7230], Section 3.2.6> field-value = <field-value, see [Semantics], Section 5.4.4>
token = <token, see [RFC7230], Section 3.2.6> obs-text = <obs-text, see [Semantics], Section 5.7.4>
port = <port, see [RFC3986], Section 3.2.3>
query = <query, see [RFC3986], Section 3.4>
quoted-string = <quoted-string, see [Semantics], Section 5.7.4>
token = <token, see [Semantics], Section 5.7.2>
uri-host = <host, see [RFC3986], Section 3.2.2>
X. [Message] 2. Message
3. Message Format 2.1. Message Format
All HTTP/1.1 messages consist of a start-line followed by a sequence An HTTP/1.1 message consists of a start-line followed by a CRLF and a
of octets in a format similar to the Internet Message Format sequence of octets in a format similar to the Internet Message Format
[RFC5322]: zero or more header fields (collectively referred to as [RFC5322]: zero or more header field lines (collectively referred to
the "headers" or the "header section"), an empty line indicating the as the "headers" or the "header section"), an empty line indicating
end of the header section, and an optional message body. the end of the header section, and an optional message body.
HTTP-message = start-line HTTP-message = start-line CRLF
*( header-field CRLF ) *( field-line CRLF )
CRLF CRLF
[ message-body ] [ message-body ]
3.1. Start Line A message can be either a request from client to server or a response
from server to client. Syntactically, the two types of message
An HTTP message can be either a request from client to server or a differ only in the start-line, which is either a request-line (for
response from server to client. Syntactically, the two types of requests) or a status-line (for responses), and in the algorithm for
message differ only in the start-line, which is either a request-line determining the length of the message body (Section 6).
(for requests) or a status-line (for responses), and in the algorithm
for determining the length of the message body (Section 3.3).
start-line = request-line / status-line start-line = request-line / status-line
In theory, a client could receive requests and a server could receive In theory, a client could receive requests and a server could receive
responses, distinguishing them by their different start-line formats, responses, distinguishing them by their different start-line formats.
but, in practice, servers are implemented to only expect a request (a In practice, servers are implemented to only expect a request (a
response is interpreted as an unknown or invalid request method) and response is interpreted as an unknown or invalid request method) and
clients are implemented to only expect a response. clients are implemented to only expect a response.
Messages are passed in a format similar to that used by Internet mail Although HTTP makes use of some protocol elements similar to the
[RFC5322] and the Multipurpose Internet Mail Extensions (MIME) [RFC2045], see
Multipurpose Internet Mail Extensions (MIME) [RFC2045] (see Appendix A Appendix B for the differences between HTTP and MIME messages.
of [RFC7231] for the differences between HTTP and MIME messages).
3.5. Message Parsing Robustness 2.2. Message Parsing
The normal procedure for parsing an HTTP message is to read the The normal procedure for parsing an HTTP message is to read the
start-line into a structure, read each header field into a hash table start-line into a structure, read each header field line into a hash
by field name until the empty line, and then use the parsed data to table by field name until the empty line, and then use the parsed
determine if a message body is expected. If a message body has been data to determine if a message body is expected. If a message body
indicated, then it is read as a stream until an amount of octets has been indicated, then it is read as a stream until an amount of
equal to the message body length is read or the connection is closed. octets equal to the message body length is read or the connection is
closed.
A recipient MUST parse an HTTP message as a sequence of octets in an A recipient MUST parse an HTTP message as a sequence of octets in an
encoding that is a superset of US-ASCII [USASCII]. Parsing an HTTP encoding that is a superset of US-ASCII [USASCII]. Parsing an HTTP
message as a stream of Unicode characters, without regard for the message as a stream of Unicode characters, without regard for the
specific encoding, creates security vulnerabilities due to the specific encoding, creates security vulnerabilities due to the
varying ways that string processing libraries handle invalid varying ways that string processing libraries handle invalid
multibyte character sequences that contain the octet LF (%x0A). multibyte character sequences that contain the octet LF (%x0A).
String-based parsers can only be safely used within protocol elements String-based parsers can only be safely used within protocol elements
after the element has been extracted from the message, such as within after the element has been extracted from the message, such as within
a header field-value after message parsing has delineated the a header field line value after message parsing has delineated the
individual fields. individual field lines.
Although the line terminator for the start-line and header fields is Although the line terminator for the start-line and header fields is
the sequence CRLF, a recipient MAY recognize a single LF as a line the sequence CRLF, a recipient MAY recognize a single LF as a line
terminator and ignore any preceding CR. terminator and ignore any preceding CR.
A sender MUST NOT generate a bare CR (a CR character not immediately
followed by LF) within any protocol elements other than the payload
body. A recipient of such a bare CR MUST consider that element to be
invalid or replace each bare CR with SP before processing the element
or forwarding the message.
Older HTTP/1.0 user agent implementations might send an extra CRLF Older HTTP/1.0 user agent implementations might send an extra CRLF
after a POST request as a workaround for some early server after a POST request as a workaround for some early server
applications that failed to read message body content that was not applications that failed to read message body content that was not
terminated by a line-ending. An HTTP/1.1 user agent MUST NOT preface terminated by a line-ending. An HTTP/1.1 user agent MUST NOT preface
or follow a request with an extra CRLF. If terminating the request or follow a request with an extra CRLF. If terminating the request
message body with a line-ending is desired, then the user agent MUST message body with a line-ending is desired, then the user agent MUST
count the terminating CRLF octets as part of the message body length. count the terminating CRLF octets as part of the message body length.
In the interest of robustness, a server that is expecting to receive In the interest of robustness, a server that is expecting to receive
and parse a request-line SHOULD ignore at least one empty line (CRLF) and parse a request-line SHOULD ignore at least one empty line (CRLF)
skipping to change at line 338 skipping to change at page 8, line 14
A sender MUST NOT send whitespace between the start-line and the A sender MUST NOT send whitespace between the start-line and the
first header field. A recipient that receives whitespace between the first header field. A recipient that receives whitespace between the
start-line and the first header field MUST either reject the message start-line and the first header field MUST either reject the message
as invalid or consume each whitespace-preceded line without further as invalid or consume each whitespace-preceded line without further
processing of it (i.e., ignore the entire line, along with any processing of it (i.e., ignore the entire line, along with any
subsequent lines preceded by whitespace, until a properly formed subsequent lines preceded by whitespace, until a properly formed
header field is received or the header section is terminated). header field is received or the header section is terminated).
The presence of such whitespace in a request might be an attempt to The presence of such whitespace in a request might be an attempt to
trick a server into ignoring that field or processing the line after trick a server into ignoring that field line or processing the line
it as a new request, either of which might result in a security after it as a new request, either of which might result in a security
vulnerability if other implementations within the request chain vulnerability if other implementations within the request chain
interpret the same message differently. Likewise, the presence of interpret the same message differently. Likewise, the presence of
such whitespace in a response might be ignored by some clients or such whitespace in a response might be ignored by some clients or
cause others to cease parsing. cause others to cease parsing.
When a server listening only for HTTP request messages, or processing When a server listening only for HTTP request messages, or processing
what appears from the start-line to be an HTTP request message, what appears from the start-line to be an HTTP request message,
receives a sequence of octets that does not match the HTTP-message receives a sequence of octets that does not match the HTTP-message
grammar aside from the robustness exceptions listed above, the server grammar aside from the robustness exceptions listed above, the server
SHOULD respond with a 400 (Bad Request) response. SHOULD respond with a 400 (Bad Request) response.
2.6. Protocol Versioning 2.3. HTTP Version
HTTP uses a "<major>.<minor>" numbering scheme to indicate versions HTTP uses a "<major>.<minor>" numbering scheme to indicate versions
of the protocol. This specification defines version "1.1". of the protocol. This specification defines version "1.1".
Section 5.1 of [Semantics] specifies the semantics of HTTP version
numbers.
The version of an HTTP message is indicated by an HTTP-version field The version of an HTTP/1.x message is indicated by an HTTP-version
in the first line of the message. HTTP-version is case-sensitive. field in the start-line. HTTP-version is case-sensitive.
HTTP-version = HTTP-name "/" DIGIT "." DIGIT HTTP-version = HTTP-name "/" DIGIT "." DIGIT
HTTP-name = %x48.54.54.50 ; "HTTP", case-sensitive HTTP-name = %s"HTTP"
When an HTTP/1.1 message is sent to an HTTP/1.0 recipient [RFC1945] When an HTTP/1.1 message is sent to an HTTP/1.0 recipient [RFC1945]
or a recipient whose version is unknown, the HTTP/1.1 message is or a recipient whose version is unknown, the HTTP/1.1 message is
constructed such that it can be interpreted as a valid HTTP/1.0 constructed such that it can be interpreted as a valid HTTP/1.0
message if all of the newer features are ignored. This specification message if all of the newer features are ignored. This specification
places recipient-version requirements on some new features so that a places recipient-version requirements on some new features so that a
conformant sender will only use compatible features until it has conformant sender will only use compatible features until it has
determined, through configuration or the receipt of a message, that determined, through configuration or the receipt of a message, that
the recipient supports HTTP/1.1. the recipient supports HTTP/1.1.
Intermediaries that process HTTP messages (i.e., all intermediaries Intermediaries that process HTTP messages (i.e., all intermediaries
other than those acting as tunnels) MUST send their own HTTP-version other than those acting as tunnels) MUST send their own HTTP-version
in forwarded messages. In other words, they are not allowed to in forwarded messages. In other words, they are not allowed to
blindly forward the first line of an HTTP message without ensuring blindly forward the start-line without ensuring that the protocol
that the protocol version in that message matches a version to which version in that message matches a version to which that intermediary
that intermediary is conformant for both the receiving and sending of is conformant for both the receiving and sending of messages.
messages. Forwarding an HTTP message without rewriting the Forwarding an HTTP message without rewriting the HTTP-version might
HTTP-version might result in communication errors when downstream result in communication errors when downstream recipients use the
recipients use the message sender's version to determine what message sender's version to determine what features are safe to use
features are safe to use for later communication with that sender. for later communication with that sender.
A server MAY send an HTTP/1.0 response to a request if it is known or A server MAY send an HTTP/1.0 response to an HTTP/1.1 request if it
suspected that the client incorrectly implements the HTTP is known or suspected that the client incorrectly implements the HTTP
specification and is incapable of correctly processing later version specification and is incapable of correctly processing later version
responses, such as when a client fails to parse the version number responses, such as when a client fails to parse the version number
correctly or when an intermediary is known to blindly forward the correctly or when an intermediary is known to blindly forward the
HTTP-version even when it doesn't conform to the given minor version HTTP-version even when it doesn't conform to the given minor version
of the protocol. Such protocol downgrades SHOULD NOT be performed of the protocol. Such protocol downgrades SHOULD NOT be performed
unless triggered by specific client attributes, such as when one or unless triggered by specific client attributes, such as when one or
more of the request header fields (e.g., User-Agent) uniquely match more of the request header fields (e.g., User-Agent) uniquely match
the values sent by a client known to be in error. the values sent by a client known to be in error.
3.1.1. Request Line 3. Request Line
A request-line begins with a method token, followed by a single space A request-line begins with a method token, followed by a single space
(SP), the request-target, another single space (SP), the protocol (SP), the request-target, another single space (SP), and ends with
version, and ends with CRLF. the protocol version.
request-line = method SP request-target SP HTTP-version CRLF request-line = method SP request-target SP HTTP-version
Although the request-line and status-line grammar rules require that Although the request-line grammar rule requires that each of the
each of the component elements be separated by a single SP octet, component elements be separated by a single SP octet, recipients MAY
recipients MAY instead parse on whitespace-delimited word boundaries instead parse on whitespace-delimited word boundaries and, aside from
and, aside from the CRLF terminator, treat any form of whitespace as the CRLF terminator, treat any form of whitespace as the SP separator
the SP separator while ignoring preceding or trailing whitespace; while ignoring preceding or trailing whitespace; such whitespace
such whitespace includes one or more of the following octets: SP, includes one or more of the following octets: SP, HTAB, VT (%x0B), FF
HTAB, VT (%x0B), FF (%x0C), or bare CR. However, lenient parsing can (%x0C), or bare CR. However, lenient parsing can result in request
result in security vulnerabilities if there are multiple recipients smuggling security vulnerabilities if there are multiple recipients
of the message and each has its own unique interpretation of of the message and each has its own unique interpretation of
robustness (see Section 9.5). robustness (see Section 11.2).
HTTP does not place a predefined limit on the length of a HTTP does not place a predefined limit on the length of a request-
request-line, as described in Section 2.5. A server that receives a line, as described in Section 2 of [Semantics]. A server that
method longer than any that it implements SHOULD respond with a 501 receives a method longer than any that it implements SHOULD respond
(Not Implemented) status code. A server that receives a with a 501 (Not Implemented) status code. A server that receives a
request-target longer than any URI it wishes to parse MUST respond request-target longer than any URI it wishes to parse MUST respond
with a 414 (URI Too Long) status code (see Section 6.5.12 of with a 414 (URI Too Long) status code (see Section 14.5.15 of
[RFC7231]). [Semantics]).
Various ad hoc limitations on request-line length are found in Various ad hoc limitations on request-line length are found in
practice. It is RECOMMENDED that all HTTP senders and recipients practice. It is RECOMMENDED that all HTTP senders and recipients
support, at a minimum, request-line lengths of 8000 octets. support, at a minimum, request-line lengths of 8000 octets.
3.1. Method
The method token indicates the request method to be performed on the The method token indicates the request method to be performed on the
target resource. The request method is case-sensitive. target resource. The request method is case-sensitive.
method = token method = token
The request methods defined by this specification can be found in The request methods defined by this specification can be found in
Section 4 of [RFC7231], along with information regarding the HTTP Section 8 of [Semantics], along with information regarding the HTTP
method registry and considerations for defining new methods. method registry and considerations for defining new methods.
5.3. Request Target 3.2. Request Target
The request-target identifies the target resource upon which to apply The request-target identifies the target resource upon which to apply
the request, as defined in Section 5.3. the request. The client derives a request-target from its desired
Once an inbound connection is obtained, the client sends an HTTP
request message (Section 3) with a request-target derived from the
target URI. There are four distinct formats for the request-target, target URI. There are four distinct formats for the request-target,
depending on both the method being requested and whether the request depending on both the method being requested and whether the request
is to a proxy. is to a proxy.
request-target = origin-form request-target = origin-form
/ absolute-form / absolute-form
/ authority-form / authority-form
/ asterisk-form / asterisk-form
Recipients typically parse the request-line into its component parts No whitespace is allowed in the request-target. Unfortunately, some
by splitting on whitespace (see Section 3.5), since no whitespace is user agents fail to properly encode or exclude whitespace found in
allowed in the three components. Unfortunately, some user agents hypertext references, resulting in those disallowed characters being
fail to properly encode or exclude whitespace found in hypertext sent as the request-target in a malformed request-line.
references, resulting in those disallowed characters being sent in a
request-target.
Recipients of an invalid request-line SHOULD respond with either a Recipients of an invalid request-line SHOULD respond with either a
400 (Bad Request) error or a 301 (Moved Permanently) redirect with 400 (Bad Request) error or a 301 (Moved Permanently) redirect with
the request-target properly encoded. A recipient SHOULD NOT attempt the request-target properly encoded. A recipient SHOULD NOT attempt
to autocorrect and then process the request without a redirect, since to autocorrect and then process the request without a redirect, since
the invalid request-line might be deliberately crafted to bypass the invalid request-line might be deliberately crafted to bypass
security filters along the request chain. security filters along the request chain.
5.3.1. origin-form A client MUST send a Host header field in all HTTP/1.1 request
messages. If the target URI includes an authority component, then a
client MUST send a field value for Host that is identical to that
authority component, excluding any userinfo subcomponent and its "@"
delimiter (Section 4.2.1 of [Semantics]). If the authority component
is missing or undefined for the target URI, then a client MUST send a
Host header field with an empty field value.
A server MUST respond with a 400 (Bad Request) status code to any
HTTP/1.1 request message that lacks a Host header field and to any
request message that contains more than one Host header field or a
Host header field with an invalid field value.
3.2.1. origin-form
The most common form of request-target is the origin-form. The most common form of request-target is the origin-form.
origin-form = absolute-path [ "?" query ] origin-form = absolute-path [ "?" query ]
When making a request directly to an origin server, other than a When making a request directly to an origin server, other than a
CONNECT or server-wide OPTIONS request (as detailed below), a client CONNECT or server-wide OPTIONS request (as detailed below), a client
MUST send only the absolute path and query components of the target MUST send only the absolute path and query components of the target
URI as the request-target. If the target URI's path component is URI as the request-target. If the target URI's path component is
empty, the client MUST send "/" as the path within the origin-form of empty, the client MUST send "/" as the path within the origin-form of
request-target. A Host header field is also sent, as defined in request-target. A Host header field is also sent, as defined in
Section 5.4. Section 6.1.2 of [Semantics].
For example, a client wishing to retrieve a representation of the For example, a client wishing to retrieve a representation of the
resource identified as resource identified as
http://www.example.org/where?q=now http://www.example.org/where?q=now
directly from the origin server would open (or reuse) a TCP directly from the origin server would open (or reuse) a TCP
connection to port 80 of the host "www.example.org" and send the connection to port 80 of the host "www.example.org" and send the
lines: lines:
GET /where?q=now HTTP/1.1 GET /where?q=now HTTP/1.1
Host: www.example.org Host: www.example.org
followed by the remainder of the request message. followed by the remainder of the request message.
5.3.2. absolute-form 3.2.2. absolute-form
When making a request to a proxy, other than a CONNECT or server-wide When making a request to a proxy, other than a CONNECT or server-wide
OPTIONS request (as detailed below), a client MUST send the target OPTIONS request (as detailed below), a client MUST send the target
URI in absolute-form as the request-target. URI in absolute-form as the request-target.
absolute-form = absolute-URI absolute-form = absolute-URI
The proxy is requested to either service that request from a valid The proxy is requested to either service that request from a valid
cache, if possible, or make the same request on the client's behalf cache, if possible, or make the same request on the client's behalf
to either the next inbound proxy server or directly to the origin to either the next inbound proxy server or directly to the origin
server indicated by the request-target. Requirements on such server indicated by the request-target. Requirements on such
"forwarding" of messages are defined in Section 5.7. "forwarding" of messages are defined in Section 6.4 of [Semantics].
An example absolute-form of request-line would be: An example absolute-form of request-line would be:
GET http://www.example.org/pub/WWW/TheProject.html HTTP/1.1 GET http://www.example.org/pub/WWW/TheProject.html HTTP/1.1
A client MUST send a Host header field in an HTTP/1.1 request even if A client MUST send a Host header field in an HTTP/1.1 request even if
the request-target is in the absolute-form, since this allows the the request-target is in the absolute-form, since this allows the
Host information to be forwarded through ancient HTTP/1.0 proxies Host information to be forwarded through ancient HTTP/1.0 proxies
that might not have implemented Host. that might not have implemented Host.
When a proxy receives a request with an absolute-form of When a proxy receives a request with an absolute-form of request-
request-target, the proxy MUST ignore the received Host header field target, the proxy MUST ignore the received Host header field (if any)
(if any) and instead replace it with the host information of the and instead replace it with the host information of the request-
request-target. A proxy that forwards such a request MUST generate a target. A proxy that forwards such a request MUST generate a new
new Host field-value based on the received request-target rather than Host field value based on the received request-target rather than
forward the received Host field-value. forward the received Host field value.
When an origin server receives a request with an absolute-form of
request-target, the origin server MUST ignore the received Host
header field (if any) and instead use the host information of the
request-target. Note that if the request-target does not have an
authority component, an empty Host header field will be sent in this
case.
To allow for transition to the absolute-form for all requests in some To allow for transition to the absolute-form for all requests in some
future version of HTTP, a server MUST accept the absolute-form in future version of HTTP, a server MUST accept the absolute-form in
requests, even though HTTP/1.1 clients will only send them in requests, even though HTTP/1.1 clients will only send them in
requests to proxies. requests to proxies.
5.3.3. authority-form 3.2.3. authority-form
The authority-form of request-target is only used for CONNECT The authority-form of request-target is only used for CONNECT
requests (Section 4.3.6 of [RFC7231]). requests (Section 8.3.6 of [Semantics]).
authority-form = authority authority-form = authority
When making a CONNECT request to establish a tunnel through one or When making a CONNECT request to establish a tunnel through one or
more proxies, a client MUST send only the target URI's authority more proxies, a client MUST send only the target URI's authority
component (excluding any userinfo and its "@" delimiter) as the component (excluding any userinfo and its "@" delimiter) as the
request-target. For example, request-target. For example,
CONNECT www.example.com:80 HTTP/1.1 CONNECT www.example.com:80 HTTP/1.1
5.3.4. asterisk-form 3.2.4. asterisk-form
The asterisk-form of request-target is only used for a server-wide The asterisk-form of request-target is only used for a server-wide
OPTIONS request (Section 4.3.7 of [RFC7231]). OPTIONS request (Section 8.3.7 of [Semantics]).
asterisk-form = "*" asterisk-form = "*"
When a client wishes to request OPTIONS for the server as a whole, as When a client wishes to request OPTIONS for the server as a whole, as
opposed to a specific named resource of that server, the client MUST opposed to a specific named resource of that server, the client MUST
send only "*" (%x2A) as the request-target. For example, send only "*" (%x2A) as the request-target. For example,
OPTIONS * HTTP/1.1 OPTIONS * HTTP/1.1
If a proxy receives an OPTIONS request with an absolute-form of If a proxy receives an OPTIONS request with an absolute-form of
request-target in which the URI has an empty path and no query request-target in which the URI has an empty path and no query
component, then the last proxy on the request chain MUST send a component, then the last proxy on the request chain MUST send a
request-target of "*" when it forwards the request to the indicated request-target of "*" when it forwards the request to the indicated
origin server. origin server.
For example, the request For example, the request
skipping to change at line 570 skipping to change at page 13, line 23
OPTIONS http://www.example.org:8001 HTTP/1.1 OPTIONS http://www.example.org:8001 HTTP/1.1
would be forwarded by the final proxy as would be forwarded by the final proxy as
OPTIONS * HTTP/1.1 OPTIONS * HTTP/1.1
Host: www.example.org:8001 Host: www.example.org:8001
after connecting to port 8001 of host "www.example.org". after connecting to port 8001 of host "www.example.org".
5.5. Effective Request URI 3.3. Reconstructing the Target URI
Since the request-target often contains only part of the user agent's Since the request-target often contains only part of the user agent's
target URI, a server reconstructs the intended target as an target URI, a server constructs its value to properly service the
"effective request URI" to properly service the request. request (Section 6.1 of [Semantics]).
If the request-target is in absolute-form, the effective request URI If the request-target is in absolute-form, the target URI is the same
is the same as the request-target. Otherwise, the effective request as the request-target. Otherwise, the target URI is constructed as
URI is constructed as follows: follows:
If the server's configuration (or outbound gateway) provides a o If the server's configuration (or outbound gateway) provides a
fixed URI scheme, that scheme is used for the effective request fixed URI scheme, that scheme is used for the target URI.
URI. Otherwise, if the request is received over a TLS-secured TCP Otherwise, if the request is received over a secured connection,
connection, the effective request URI's scheme is "https"; if not, the target URI's scheme is "https"; if not, the scheme is "http".
the scheme is "http".
If the server's configuration (or outbound gateway) provides a o If the server's configuration (or outbound gateway) provides a
fixed URI authority component, that authority is used for the fixed URI authority component, that authority is used for the
effective request URI. If not, then if the request-target is in target URI. If not, then if the request-target is in
authority-form, the effective request URI's authority component is authority-form, the target URI's authority component is the same
the same as the request-target. If not, then if a Host header as the request-target. If not, then if a Host header field is
field is supplied with a non-empty field-value, the authority supplied with a non-empty field-value, the authority component is
component is the same as the Host field-value. Otherwise, the the same as the Host field-value. Otherwise, the authority
authority component is assigned the default name configured for component is assigned the default name configured for the server
the server and, if the connection's incoming TCP port number and, if the connection's incoming TCP port number differs from the
differs from the default port for the effective request URI's default port for the target URI's scheme, then a colon (":") and
scheme, then a colon (":") and the incoming port number (in the incoming port number (in decimal form) are appended to the
decimal form) are appended to the authority component. authority component.
If the request-target is in authority-form or asterisk-form, the o If the request-target is in authority-form or asterisk-form, the
effective request URI's combined path and query component is target URI's combined path and query component is empty.
empty. Otherwise, the combined path and query component is the Otherwise, the combined path and query component is the same as
same as the request-target. the request-target.
The components of the effective request URI, once determined as o The components of the target URI, once determined as above, can be
above, can be combined into absolute-URI form by concatenating the combined into absolute-URI form by concatenating the scheme,
scheme, "://", authority, and combined path and query component. "://", authority, and combined path and query component.
Example 1: the following message received over an insecure TCP Example 1: the following message received over an insecure TCP
connection connection
GET /pub/WWW/TheProject.html HTTP/1.1 GET /pub/WWW/TheProject.html HTTP/1.1
Host: www.example.org:8080 Host: www.example.org:8080
has an effective request URI of has a target URI of
http://www.example.org:8080/pub/WWW/TheProject.html http://www.example.org:8080/pub/WWW/TheProject.html
Example 2: the following message received over a TLS-secured TCP Example 2: the following message received over a secured connection
connection
OPTIONS * HTTP/1.1 OPTIONS * HTTP/1.1
Host: www.example.org Host: www.example.org
has an effective request URI of has a target URI of
https://www.example.org https://www.example.org
Recipients of an HTTP/1.0 request that lacks a Host header field Recipients of an HTTP/1.0 request that lacks a Host header field
might need to use heuristics (e.g., examination of the URI path for might need to use heuristics (e.g., examination of the URI path for
something unique to a particular host) in order to guess the something unique to a particular host) in order to guess the target
effective request URI's authority component. URI's authority component.
3.1.2. Status Line 4. Status Line
The first line of a response message is the status-line, consisting The first line of a response message is the status-line, consisting
of the protocol version, a space (SP), the status code, another of the protocol version, a space (SP), the status code, another
space, a possibly empty textual phrase describing the status code, space, and ending with an OPTIONAL textual phrase describing the
and ending with CRLF. status code.
status-line = HTTP-version SP status-code SP reason-phrase CRLF status-line = HTTP-version SP status-code SP [reason-phrase]
Although the request-line and status-line grammar rules require that Although the status-line grammar rule requires that each of the
each of the component elements be separated by a single SP octet, component elements be separated by a single SP octet, recipients MAY
recipients MAY instead parse on whitespace-delimited word boundaries instead parse on whitespace-delimited word boundaries and, aside from
and, aside from the CRLF terminator, treat any form of whitespace as the line terminator, treat any form of whitespace as the SP separator
the SP separator while ignoring preceding or trailing whitespace; while ignoring preceding or trailing whitespace; such whitespace
such whitespace includes one or more of the following octets: SP, includes one or more of the following octets: SP, HTAB, VT (%x0B), FF
HTAB, VT (%x0B), FF (%x0C), or bare CR. However, lenient parsing can (%x0C), or bare CR. However, lenient parsing can result in response
result in security vulnerabilities if there are multiple recipients splitting security vulnerabilities if there are multiple recipients
of the message and each has its own unique interpretation of of the message and each has its own unique interpretation of
robustness (see Section 9.5). robustness (see Section 11.1).
The status-code element is a 3-digit integer code describing the The status-code element is a 3-digit integer code describing the
result of the server's attempt to understand and satisfy the client's result of the server's attempt to understand and satisfy the client's
corresponding request. The rest of the response message is to be corresponding request. The rest of the response message is to be
interpreted in light of the semantics defined for that status code. interpreted in light of the semantics defined for that status code.
See Section 6 of [RFC7231] for information about the semantics of See Section 14 of [Semantics] for information about the semantics of
status codes, including the classes of status code (indicated by the status codes, including the classes of status code (indicated by the
first digit), the status codes defined by this specification, first digit), the status codes defined by this specification,
considerations for the definition of new status codes, and the IANA considerations for the definition of new status codes, and the IANA
registry. registry.
status-code = 3DIGIT status-code = 3DIGIT
The reason-phrase element exists for the sole purpose of providing a The reason-phrase element exists for the sole purpose of providing a
textual description associated with the numeric status code, mostly textual description associated with the numeric status code, mostly
out of deference to earlier Internet application protocols that were out of deference to earlier Internet application protocols that were
more frequently used with interactive text clients. A client SHOULD more frequently used with interactive text clients.
ignore the reason-phrase content.
reason-phrase = *( HTAB / SP / VCHAR / obs-text ) reason-phrase = 1*( HTAB / SP / VCHAR / obs-text )
A client SHOULD ignore the reason-phrase content because it is not a
reliable channel for information (it might be translated for a given
locale, overwritten by intermediaries, or discarded when the message
is forwarded via other versions of HTTP). A server MUST send the
space that separates status-code from the reason-phrase even when the
reason-phrase is absent (i.e., the status-line would end with the
three octets SP CR LF).
5. Field Syntax 5. Field Syntax
Each header field consists of a case-insensitive field name followed Each field line consists of a case-insensitive field name followed by
by a colon (":"), optional leading whitespace, the field value, and a colon (":"), optional leading whitespace, the field line value, and
optional trailing whitespace. optional trailing whitespace.
header-field = field-name ":" OWS field-value OWS field-line = field-name ":" OWS field-value OWS
This document defines the following HTTP header fields. Most HTTP field names and the rules for parsing within field values
are defined in Section 5.4 of [Semantics]. This section covers the
generic syntax for header field inclusion within, and extraction
from, HTTP/1.1 messages. In addition, the following header fields
are defined by this document because they are specific to HTTP/1.1
message processing:
+-------------------+----------+----------+---------------+ ------------------- ---------- ------
| Header Field Name | Protocol | Status | Reference | Field Name Status Ref.
+-------------------+----------+----------+---------------+ ------------------- ---------- ------
| MIME-Version | http | standard | Appendix A.1 | MIME-Version standard B.1
| Transfer-Encoding | http | standard | Section 3.3.1 | Transfer-Encoding standard 6.1
+-------------------+----------+----------+---------------+ ------------------- ---------- ------
Furthermore, the header field-name "Close" has been registered as Table 1
"reserved", since using that name as an HTTP header field might
conflict with the "close" connection option of the Connection header
field (Section 6.1).
+-------------------+----------+----------+------------+ Furthermore, the field name "Close" is reserved, since using that
| Header Field Name | Protocol | Status | Reference | name as an HTTP header field might conflict with the "close"
+-------------------+----------+----------+------------+ connection option of the Connection header field (Section 6.4.1 of
| Close | http | reserved | Section 8.1 | [Semantics]).
+-------------------+----------+----------+------------+
5.1. Field Parsing ------------ ---------- ----------- ------------
Field Name Status Reference Comments
------------ ---------- ----------- ------------
Close standard Section 5 (reserved)
------------ ---------- ----------- ------------
Table 2
5.1. Field Line Parsing
Messages are parsed using a generic algorithm, independent of the Messages are parsed using a generic algorithm, independent of the
individual header field names. The contents within a given field individual field names. The contents within a given field line value
value are not parsed until a later stage of message interpretation are not parsed until a later stage of message interpretation (usually
(usually after the message's entire header section has been after the message's entire header section has been processed).
processed).
No whitespace is allowed between the header field-name and colon. In No whitespace is allowed between the field name and colon. In the
the past, differences in the handling of such whitespace have led to past, differences in the handling of such whitespace have led to
security vulnerabilities in request routing and response handling. A security vulnerabilities in request routing and response handling. A
server MUST reject any received request message that contains server MUST reject any received request message that contains
whitespace between a header field-name and colon with a response code whitespace between a header field name and colon with a response
of 400 (Bad Request). A proxy MUST remove any such whitespace from a status code of 400 (Bad Request). A proxy MUST remove any such
response message before forwarding the message downstream. whitespace from a response message before forwarding the message
downstream.
A field value might be preceded and/or followed by optional A field line value might be preceded and/or followed by optional
whitespace (OWS); a single SP preceding the field-value is preferred whitespace (OWS); a single SP preceding the field line value is
for consistent readability by humans. The field value does not preferred for consistent readability by humans. The field line value
include any leading or trailing whitespace: OWS occurring before the does not include any leading or trailing whitespace: OWS occurring
first non-whitespace octet of the field value or after the last before the first non-whitespace octet of the field line value or
non-whitespace octet of the field value ought to be excluded by after the last non-whitespace octet of the field line value ought to
parsers when extracting the field value from a header field. be excluded by parsers when extracting the field line value from a
header field line.
Historically, HTTP header field values could be extended over 5.2. Obsolete Line Folding
Historically, HTTP header field line values could be extended over
multiple lines by preceding each extra line with at least one space multiple lines by preceding each extra line with at least one space
or horizontal tab (obs-fold). This specification deprecates such or horizontal tab (obs-fold). This specification deprecates such
line folding except within the message/http media type line folding except within the message/http media type
(Section 8.3.1). (Section 10.1).
obs-fold = CRLF 1*( SP / HTAB ) obs-fold = OWS CRLF RWS
; obsolete line folding ; obsolete line folding
; see Section 3.2.4
A sender MUST NOT generate a message that includes A sender MUST NOT generate a message that includes line folding
line folding (i.e., that has any field-value that contains a match to (i.e., that has any field line value that contains a match to the
the obs-fold rule) unless the message is intended for packaging obs-fold rule) unless the message is intended for packaging within
within the message/http media type. the message/http media type.
A server that receives an obs-fold in a request message that is not A server that receives an obs-fold in a request message that is not
within a message/http container MUST either reject the message by within a message/http container MUST either reject the message by
sending a 400 (Bad Request), preferably with a representation sending a 400 (Bad Request), preferably with a representation
explaining that obsolete line folding is unacceptable, or replace explaining that obsolete line folding is unacceptable, or replace
each received obs-fold with one or more SP octets prior to each received obs-fold with one or more SP octets prior to
interpreting the field value or forwarding the message downstream. interpreting the field value or forwarding the message downstream.
A proxy or gateway that receives an obs-fold in a response message A proxy or gateway that receives an obs-fold in a response message
that is not within a message/http container MUST either discard the that is not within a message/http container MUST either discard the
skipping to change at line 760 skipping to change at page 17, line 41
with a representation explaining that unacceptable line folding was with a representation explaining that unacceptable line folding was
received, or replace each received obs-fold with one or more SP received, or replace each received obs-fold with one or more SP
octets prior to interpreting the field value or forwarding the octets prior to interpreting the field value or forwarding the
message downstream. message downstream.
A user agent that receives an obs-fold in a response message that is A user agent that receives an obs-fold in a response message that is
not within a message/http container MUST replace each received not within a message/http container MUST replace each received
obs-fold with one or more SP octets prior to interpreting the field obs-fold with one or more SP octets prior to interpreting the field
value. value.
3.3. Message Body 6. Message Body
The message body (if any) of an HTTP message is used to carry the The message body (if any) of an HTTP message is used to carry the
payload body of that request or response. The message body is payload body (Section 5.5.4 of [Semantics]) of that request or
identical to the payload body unless a transfer coding has been response. The message body is identical to the payload body unless a
applied, as described in Section 3.3.1. transfer coding has been applied, as described in Section 6.1.
message-body = *OCTET message-body = *OCTET
The rules for when a message body is allowed in a message differ for The rules for determining when a message body is present in an
requests and responses. HTTP/1.1 message differ for requests and responses.
The presence of a message body in a request is signaled by a The presence of a message body in a request is signaled by a
Content-Length or Transfer-Encoding header field. Request message Content-Length or Transfer-Encoding header field. Request message
framing is independent of method semantics, even if the method does framing is independent of method semantics, even if the method does
not define any use for a message body. not define any use for a message body.
The presence of a message body in a response depends on both the The presence of a message body in a response depends on both the
request method to which it is responding and the response status code request method to which it is responding and the response status code
(Section 3.1.2). (Section 4), and corresponds to when a payload body is allowed; see
Section 5.5.4 of [Semantics].
3.3.1. Transfer-Encoding 6.1. Transfer-Encoding
The Transfer-Encoding header field lists the transfer coding names The Transfer-Encoding header field lists the transfer coding names
corresponding to the sequence of transfer codings that have been (or corresponding to the sequence of transfer codings that have been (or
will be) applied to the payload body in order to form the message will be) applied to the payload body in order to form the message
body. Transfer codings are defined in Section 4. body. Transfer codings are defined in Section 7.
Transfer-Encoding = 1#transfer-coding Transfer-Encoding = #transfer-coding
Transfer-Encoding is analogous to the Content-Transfer-Encoding field Transfer-Encoding is analogous to the Content-Transfer-Encoding field
of MIME, which was designed to enable safe transport of binary data of MIME, which was designed to enable safe transport of binary data
over a 7-bit transport service ([RFC2045], Section 6). However, safe over a 7-bit transport service ([RFC2045], Section 6). However, safe
transport has a different focus for an 8bit-clean transfer protocol. transport has a different focus for an 8bit-clean transfer protocol.
In HTTP's case, Transfer-Encoding is primarily intended to accurately In HTTP's case, Transfer-Encoding is primarily intended to accurately
delimit a dynamically generated payload and to distinguish payload delimit a dynamically generated payload and to distinguish payload
encodings that are only applied for transport efficiency or security encodings that are only applied for transport efficiency or security
from those that are characteristics of the selected resource. from those that are characteristics of the selected resource.
A recipient MUST be able to parse the chunked transfer coding A recipient MUST be able to parse the chunked transfer coding
(Section 4.1) because it plays a crucial role in framing messages (Section 7.1) because it plays a crucial role in framing messages
when the payload body size is not known in advance. A sender MUST when the payload body size is not known in advance. A sender MUST
NOT apply chunked more than once to a message body (i.e., chunking an NOT apply chunked more than once to a message body (i.e., chunking an
already chunked message is not allowed). If any transfer coding already chunked message is not allowed). If any transfer coding
other than chunked is applied to a request payload body, the sender other than chunked is applied to a request payload body, the sender
MUST apply chunked as the final transfer coding to ensure that the MUST apply chunked as the final transfer coding to ensure that the
message is properly framed. If any transfer coding other than message is properly framed. If any transfer coding other than
chunked is applied to a response payload body, the sender MUST either chunked is applied to a response payload body, the sender MUST either
apply chunked as the final transfer coding or terminate the message apply chunked as the final transfer coding or terminate the message
by closing the connection. by closing the connection.
For example, For example,
Transfer-Encoding: gzip, chunked Transfer-Encoding: gzip, chunked
indicates that the payload body has been compressed using the gzip indicates that the payload body has been compressed using the gzip
coding and then chunked using the chunked coding while forming the coding and then chunked using the chunked coding while forming the
message body. message body.
Unlike Content-Encoding (Section 3.1.2.1 of [RFC7231]), Unlike Content-Encoding (Section 7.5.1 of [Semantics]), Transfer-
Transfer-Encoding is a property of the message, not of the Encoding is a property of the message, not of the representation, and
representation, and any recipient along the request/response chain any recipient along the request/response chain MAY decode the
MAY decode the received transfer coding(s) or apply additional received transfer coding(s) or apply additional transfer coding(s) to
transfer coding(s) to the message body, assuming that corresponding the message body, assuming that corresponding changes are made to the
changes are made to the Transfer-Encoding field-value. Additional Transfer-Encoding field value. Additional information about the
information about the encoding parameters can be provided by other encoding parameters can be provided by other header fields not
header fields not defined by this specification. defined by this specification.
Transfer-Encoding MAY be sent in a response to a HEAD request or in a Transfer-Encoding MAY be sent in a response to a HEAD request or in a
304 (Not Modified) response (Section 4.1 of [RFC7232]) to a GET 304 (Not Modified) response (Section 14.4.5 of [Semantics]) to a GET
request, neither of which includes a message body, to indicate that request, neither of which includes a message body, to indicate that
the origin server would have applied a transfer coding to the message the origin server would have applied a transfer coding to the message
body if the request had been an unconditional GET. This indication body if the request had been an unconditional GET. This indication
is not required, however, because any recipient on the response chain is not required, however, because any recipient on the response chain
(including the origin server) can remove transfer codings when they (including the origin server) can remove transfer codings when they
are not needed. are not needed.
A server MUST NOT send a Transfer-Encoding header field in any A server MUST NOT send a Transfer-Encoding header field in any
response with a status code of 1xx (Informational) or 204 (No response with a status code of 1xx (Informational) or 204 (No
Content). A server MUST NOT send a Transfer-Encoding header field in Content). A server MUST NOT send a Transfer-Encoding header field in
any 2xx (Successful) response to a CONNECT request (Section 4.3.6 of any 2xx (Successful) response to a CONNECT request (Section 8.3.6 of
[RFC7231]). [Semantics]).
Transfer-Encoding was added in HTTP/1.1. It is generally assumed Transfer-Encoding was added in HTTP/1.1. It is generally assumed
that implementations advertising only HTTP/1.0 support will not that implementations advertising only HTTP/1.0 support will not
understand how to process a transfer-encoded payload. A client MUST understand how to process a transfer-encoded payload. A client MUST
NOT send a request containing Transfer-Encoding unless it knows the NOT send a request containing Transfer-Encoding unless it knows the
server will handle HTTP/1.1 (or later) requests; such knowledge might server will handle HTTP/1.1 requests (or later minor revisions); such
be in the form of specific user configuration or by remembering the knowledge might be in the form of specific user configuration or by
version of a prior received response. A server MUST NOT send a remembering the version of a prior received response. A server MUST
response containing Transfer-Encoding unless the corresponding NOT send a response containing Transfer-Encoding unless the
request indicates HTTP/1.1 (or later). corresponding request indicates HTTP/1.1 (or later minor revisions).
A server that receives a request message with a transfer coding it A server that receives a request message with a transfer coding it
does not understand SHOULD respond with 501 (Not Implemented). does not understand SHOULD respond with 501 (Not Implemented).
3.3.2. Content-Length 6.2. Content-Length
When a message does not have a Transfer-Encoding header field, a When a message does not have a Transfer-Encoding header field, a
Content-Length header field can provide the anticipated size, as a Content-Length header field can provide the anticipated size, as a
decimal number of octets, for a potential payload body. For messages decimal number of octets, for a potential payload body. For messages
that do include a payload body, the Content-Length field-value that do include a payload body, the Content-Length field value
provides the framing information necessary for determining where the provides the framing information necessary for determining where the
body (and message) ends. For messages that do not include a payload body (and message) ends. For messages that do not include a payload
body, the Content-Length indicates the size of the selected body, the Content-Length indicates the size of the selected
representation (Section 3 of [RFC7231]). representation (Section 7.7 of [Semantics]).
Note: HTTP's use of Content-Length for message framing differs | *Note:* HTTP's use of Content-Length for message framing
significantly from the same field's use in MIME, where it is an | differs significantly from the same field's use in MIME, where
optional field used only within the "message/external-body" | it is an optional field used only within the "message/external-
media-type. | body" media-type.
3.3.3. Message Body Length 6.3. Message Body Length
The length of a message body is determined by one of the following The length of a message body is determined by one of the following
(in order of precedence): (in order of precedence):
1. Any response to a HEAD request and any response with a 1xx 1. Any response to a HEAD request and any response with a 1xx
(Informational), 204 (No Content), or 304 (Not Modified) status (Informational), 204 (No Content), or 304 (Not Modified) status
code is always terminated by the first empty line after the code is always terminated by the first empty line after the
header fields, regardless of the header fields present in the header fields, regardless of the header fields present in the
message, and thus cannot contain a message body. message, and thus cannot contain a message body.
2. Any 2xx (Successful) response to a CONNECT request implies that 2. Any 2xx (Successful) response to a CONNECT request implies that
the connection will become a tunnel immediately after the empty the connection will become a tunnel immediately after the empty
line that concludes the header fields. A client MUST ignore any line that concludes the header fields. A client MUST ignore any
Content-Length or Transfer-Encoding header fields received in Content-Length or Transfer-Encoding header fields received in
such a message. such a message.
3. If a Transfer-Encoding header field is present and the chunked 3. If a Transfer-Encoding header field is present and the chunked
transfer coding (Section 4.1) is the final encoding, the message transfer coding (Section 7.1) is the final encoding, the message
body length is determined by reading and decoding the chunked body length is determined by reading and decoding the chunked
data until the transfer coding indicates the data is complete. data until the transfer coding indicates the data is complete.
If a Transfer-Encoding header field is present in a response and If a Transfer-Encoding header field is present in a response and
the chunked transfer coding is not the final encoding, the the chunked transfer coding is not the final encoding, the
message body length is determined by reading the connection until message body length is determined by reading the connection until
it is closed by the server. If a Transfer-Encoding header field it is closed by the server. If a Transfer-Encoding header field
is present in a request and the chunked transfer coding is not is present in a request and the chunked transfer coding is not
the final encoding, the message body length cannot be determined the final encoding, the message body length cannot be determined
reliably; the server MUST respond with the 400 (Bad Request) reliably; the server MUST respond with the 400 (Bad Request)
status code and then close the connection. status code and then close the connection.
If a message is received with both a Transfer-Encoding and a If a message is received with both a Transfer-Encoding and a
Content-Length header field, the Transfer-Encoding overrides the Content-Length header field, the Transfer-Encoding overrides the
Content-Length. Such a message might indicate an attempt to Content-Length. Such a message might indicate an attempt to
perform request smuggling (Section 9.5) or response splitting perform request smuggling (Section 11.2) or response splitting
(Section 9.4) and ought to be handled as an error. A sender MUST (Section 11.1) and ought to be handled as an error. A sender
remove the received Content-Length field prior to forwarding such MUST remove the received Content-Length field prior to forwarding
a message downstream. such a message downstream.
4. If a message is received without Transfer-Encoding and with 4. If a message is received without Transfer-Encoding and with an
either multiple Content-Length header fields having differing invalid Content-Length header field, then the message framing is
field-values or a single Content-Length header field having an invalid and the recipient MUST treat it as an unrecoverable
invalid value, then the message framing is invalid and the error, unless the field value can be successfully parsed as a
recipient MUST treat it as an unrecoverable error. If this is a comma-separated list (Section 5.7.1 of [Semantics]), all values
request message, the server MUST respond with a 400 (Bad Request) in the list are valid, and all values in the list are the same.
status code and then close the connection. If this is a response If this is a request message, the server MUST respond with a 400
message received by a proxy, the proxy MUST close the connection (Bad Request) status code and then close the connection. If this
to the server, discard the received response, and send a 502 (Bad is a response message received by a proxy, the proxy MUST close
Gateway) response to the client. If this is a response message the connection to the server, discard the received response, and
received by a user agent, the user agent MUST close the send a 502 (Bad Gateway) response to the client. If this is a
connection to the server and discard the received response. response message received by a user agent, the user agent MUST
close the connection to the server and discard the received
response.
5. If a valid Content-Length header field is present without 5. If a valid Content-Length header field is present without
Transfer-Encoding, its decimal value defines the expected message Transfer-Encoding, its decimal value defines the expected message
body length in octets. If the sender closes the connection or body length in octets. If the sender closes the connection or
the recipient times out before the indicated number of octets are the recipient times out before the indicated number of octets are
received, the recipient MUST consider the message to be received, the recipient MUST consider the message to be
incomplete and close the connection. incomplete and close the connection.
6. If this is a request message and none of the above are true, then 6. If this is a request message and none of the above are true, then
the message body length is zero (no message body is present). the message body length is zero (no message body is present).
7. Otherwise, this is a response message without a declared message 7. Otherwise, this is a response message without a declared message
body length, so the message body length is determined by the body length, so the message body length is determined by the
number of octets received prior to the server closing the number of octets received prior to the server closing the
connection. connection.
Since there is no way to distinguish a successfully completed, Since there is no way to distinguish a successfully completed, close-
close-delimited message from a partially received message interrupted delimited response message from a partially received message
by network failure, a server SHOULD generate encoding or interrupted by network failure, a server SHOULD generate encoding or
length-delimited messages whenever possible. The close-delimiting length-delimited messages whenever possible. The close-delimiting
feature exists primarily for backwards compatibility with HTTP/1.0. feature exists primarily for backwards compatibility with HTTP/1.0.
| *Note:* Request messages are never close-delimited because they
| are always explicitly framed by length or transfer coding, with
| the absence of both implying the request ends immediately after
| the header section.
A server MAY reject a request that contains a message body but not a A server MAY reject a request that contains a message body but not a
Content-Length by responding with 411 (Length Required). Content-Length by responding with 411 (Length Required).
Unless a transfer coding other than chunked has been applied, a Unless a transfer coding other than chunked has been applied, a
client that sends a request containing a message body SHOULD use a client that sends a request containing a message body SHOULD use a
valid Content-Length header field if the message body length is known valid Content-Length header field if the message body length is known
in advance, rather than the chunked transfer coding, since some in advance, rather than the chunked transfer coding, since some
existing services respond to chunked with a 411 (Length Required) existing services respond to chunked with a 411 (Length Required)
status code even though they understand the chunked transfer coding. status code even though they understand the chunked transfer coding.
This is typically because such services are implemented via a gateway This is typically because such services are implemented via a gateway
skipping to change at line 974 skipping to change at page 22, line 31
If the final response to the last request on a connection has been If the final response to the last request on a connection has been
completely received and there remains additional data to read, a user completely received and there remains additional data to read, a user
agent MAY discard the remaining data or attempt to determine if that agent MAY discard the remaining data or attempt to determine if that
data belongs as part of the prior response body, which might be the data belongs as part of the prior response body, which might be the
case if the prior message's Content-Length value is incorrect. A case if the prior message's Content-Length value is incorrect. A
client MUST NOT process, cache, or forward such extra data as a client MUST NOT process, cache, or forward such extra data as a
separate response, since such behavior would be vulnerable to cache separate response, since such behavior would be vulnerable to cache
poisoning. poisoning.
4. Transfer Codings 7. Transfer Codings
Transfer coding names are used to indicate an encoding transformation Transfer coding names are used to indicate an encoding transformation
that has been, can be, or might need to be applied to a payload body that has been, can be, or might need to be applied to a payload body
in order to ensure "safe transport" through the network. This in order to ensure "safe transport" through the network. This
differs from a content coding in that the transfer coding is a differs from a content coding in that the transfer coding is a
property of the message rather than a property of the representation property of the message rather than a property of the representation
that is being transferred. that is being transferred.
transfer-coding = "chunked" ; Section 4.1 transfer-coding = token *( OWS ";" OWS transfer-parameter )
/ "compress" ; Section 4.2.1
/ "deflate" ; Section 4.2.2
/ "gzip" ; Section 4.2.3
/ transfer-extension
transfer-extension = token *( OWS ";" OWS transfer-parameter )
Parameters are in the form of a name or name=value pair. Parameters are in the form of a name=value pair.
transfer-parameter = token BWS "=" BWS ( token / quoted-string ) transfer-parameter = token BWS "=" BWS ( token / quoted-string )
All transfer-coding names are case-insensitive and ought to be All transfer-coding names are case-insensitive and ought to be
registered within the HTTP Transfer Coding registry, as defined in registered within the HTTP Transfer Coding registry, as defined in
Section 8.4. They are used in the TE (Section 4.3) and Section 7.3. They are used in the TE (Section 9.1.4 of [Semantics])
Transfer-Encoding (Section 3.3.1) header fields. and Transfer-Encoding (Section 6.1) header fields.
+------------+--------------------------------------+---------------+ ------------ ------------------------------- -----------
| Name | Description | Reference | Name Description Reference
+------------+--------------------------------------+---------------+ ------------ ------------------------------- -----------
| chunked | Transfer in a series of chunks | Section 4.1 | chunked Transfer in a series of Section
| compress | UNIX "compress" data format [Welch] | Section 4.2.1 | chunks 7.1
| deflate | "deflate" compressed data | Section 4.2.2 | compress UNIX "compress" data format Section
| | ([RFC1951]) inside the "zlib" data | | [Welch] 7.2
| | format ([RFC1950]) | | deflate "deflate" compressed data Section
| gzip | GZIP file format [RFC1952] | Section 4.2.3 | ([RFC1951]) inside the "zlib" 7.2
| x-compress | Deprecated (alias for compress) | Section 4.2.1 | data format ([RFC1950])
| x-gzip | Deprecated (alias for gzip) | Section 4.2.3 | gzip GZIP file format [RFC1952] Section
+------------+--------------------------------------+---------------+ 7.2
trailers (reserved) Section 7
x-compress Deprecated (alias for Section
compress) 7.2
x-gzip Deprecated (alias for gzip) Section
7.2
------------ ------------------------------- -----------
Table 3
| *Note:* the coding name "trailers" is reserved because its use
| would conflict with the keyword "trailers" in the TE header
| field (Section 9.1.4 of [Semantics]).
7.1. Chunked Transfer Coding 7.1. Chunked Transfer Coding
The chunked transfer coding wraps the payload body in order to The chunked transfer coding wraps the payload body in order to
transfer it as a series of chunks, each with its own size indicator, transfer it as a series of chunks, each with its own size indicator,
followed by an OPTIONAL trailer containing header fields. Chunked followed by an OPTIONAL trailer section containing trailer fields.
enables content streams of unknown size to be transferred as a Chunked enables content streams of unknown size to be transferred as
sequence of length-delimited buffers, which enables the sender to a sequence of length-delimited buffers, which enables the sender to
retain connection persistence and the recipient to know when it has retain connection persistence and the recipient to know when it has
received the entire message. received the entire message.
chunked-body = *chunk chunked-body = *chunk
last-chunk last-chunk
trailer-part trailer-section
CRLF CRLF
chunk = chunk-size [ chunk-ext ] CRLF chunk = chunk-size [ chunk-ext ] CRLF
chunk-data CRLF chunk-data CRLF
chunk-size = 1*HEXDIG chunk-size = 1*HEXDIG
last-chunk = 1*("0") [ chunk-ext ] CRLF last-chunk = 1*("0") [ chunk-ext ] CRLF
chunk-data = 1*OCTET ; a sequence of chunk-size octets chunk-data = 1*OCTET ; a sequence of chunk-size octets
The chunk-size field is a string of hex digits indicating the size of The chunk-size field is a string of hex digits indicating the size of
the chunk-data in octets. The chunked transfer coding is complete the chunk-data in octets. The chunked transfer coding is complete
when a chunk with a chunk-size of zero is received, possibly followed when a chunk with a chunk-size of zero is received, possibly followed
by a trailer, and finally terminated by an empty line. by a trailer section, and finally terminated by an empty line.
A recipient MUST be able to parse and decode the chunked transfer A recipient MUST be able to parse and decode the chunked transfer
coding. coding.
Note that HTTP/1.1 does not define any means to limit the size of a
chunked response such that an intermediary can be assured of
buffering the entire response.
The chunked encoding does not define any parameters. Their presence
SHOULD be treated as an error.
7.1.1. Chunk Extensions 7.1.1. Chunk Extensions
The chunked encoding allows each chunk to include zero or more chunk The chunked encoding allows each chunk to include zero or more chunk
extensions, immediately following the chunk-size, for the sake of extensions, immediately following the chunk-size, for the sake of
supplying per-chunk metadata (such as a signature or hash), supplying per-chunk metadata (such as a signature or hash), mid-
mid-message control information, or randomization of message body message control information, or randomization of message body size.
size.
chunk-ext = *( ";" chunk-ext-name [ "=" chunk-ext-val ] ) chunk-ext = *( BWS ";" BWS chunk-ext-name
[ BWS "=" BWS chunk-ext-val ] )
chunk-ext-name = token chunk-ext-name = token
chunk-ext-val = token / quoted-string chunk-ext-val = token / quoted-string
The chunked encoding is specific to each connection and is likely to The chunked encoding is specific to each connection and is likely to
be removed or recoded by each recipient (including intermediaries) be removed or recoded by each recipient (including intermediaries)
before any higher-level application would have a chance to inspect before any higher-level application would have a chance to inspect
the extensions. Hence, use of chunk extensions is generally limited the extensions. Hence, use of chunk extensions is generally limited
to specialized HTTP services such as "long polling" (where client and to specialized HTTP services such as "long polling" (where client and
server can have shared expectations regarding the use of chunk server can have shared expectations regarding the use of chunk
extensions) or for padding within an end-to-end secured connection. extensions) or for padding within an end-to-end secured connection.
A recipient MUST ignore unrecognized chunk extensions. A server A recipient MUST ignore unrecognized chunk extensions. A server
ought to limit the total length of chunk extensions received in a ought to limit the total length of chunk extensions received in a
request to an amount reasonable for the services provided, in the request to an amount reasonable for the services provided, in the
same way that it applies length limitations and timeouts for other same way that it applies length limitations and timeouts for other
parts of a message, and generate an appropriate 4xx (Client Error) parts of a message, and generate an appropriate 4xx (Client Error)
response if that amount is exceeded. response if that amount is exceeded.
7.1.2. Chunked Trailer Part 7.1.2. Chunked Trailer Section
A trailer allows the sender to include additional fields at the end A trailer section allows the sender to include additional fields at
of a chunked message in order to supply metadata that might be the end of a chunked message in order to supply metadata that might
dynamically generated while the message body is sent, such as a be dynamically generated while the message body is sent, such as a
message integrity check, digital signature, or post-processing message integrity check, digital signature, or post-processing
status. The trailer fields are identical to header fields, except status. The proper use and limitations of trailer fields are defined
they are sent in a chunked trailer instead of the message's header in Section 5.6 of [Semantics].
section.
trailer-part = *( header-field CRLF ) trailer-section = *( field-line CRLF )
When a chunked message containing a non-empty trailer is received, A recipient that decodes and removes the chunked encoding from a
the recipient MAY process the fields (aside from those forbidden message (e.g., for storage or forwarding to a non-HTTP/1.1 peer) MUST
above) as if they were appended to the message's header section. A discard any received trailer fields, store/forward them separately
recipient MUST ignore (or consider as an error) any fields that are from the header fields, or selectively merge into the header section
forbidden to be sent in a trailer, since processing them as if they only those trailer fields corresponding to header field definitions
were present in the header section might bypass external security that are understood by the recipient to explicitly permit and define
filters. how their corresponding trailer field value can be safely merged.
7.1.3. Decoding Chunked 7.1.3. Decoding Chunked
A process for decoding the chunked transfer coding can be represented A process for decoding the chunked transfer coding can be represented
in pseudo-code as: in pseudo-code as:
length := 0 length := 0
read chunk-size, chunk-ext (if any), and CRLF read chunk-size, chunk-ext (if any), and CRLF
while (chunk-size > 0) { while (chunk-size > 0) {
read chunk-data and CRLF read chunk-data and CRLF
append chunk-data to decoded-body append chunk-data to decoded-body
length := length + chunk-size length := length + chunk-size
read chunk-size, chunk-ext (if any), and CRLF read chunk-size, chunk-ext (if any), and CRLF
} }
read trailer field read trailer field
while (trailer field is not empty) { while (trailer field is not empty) {
if (trailer field is allowed to be sent in a trailer) { if (trailer fields are stored/forwarded separately) {
append trailer field to existing header fields append trailer field to existing trailer fields
} }
read trailer-field else if (trailer field is understood and defined as mergeable) {
merge trailer field with existing header fields
}
else {
discard trailer field
}
read trailer field
} }
Content-Length := length Content-Length := length
Remove "chunked" from Transfer-Encoding Remove "chunked" from Transfer-Encoding
Remove Trailer from existing header fields Remove Trailer from existing header fields
7.2. Compression Codings 7.2. Transfer Codings for Compression
The codings defined below can be used to compress the payload of a The following transfer coding names for compression are defined by
message. the same algorithm as their corresponding content coding:
compress (and x-compress)
See Section 7.5.1.1 of [Semantics].
deflate
See Section 7.5.1.2 of [Semantics].
gzip (and x-gzip)
See Section 7.5.1.3 of [Semantics].
The compression codings do not define any parameters. Their presence
SHOULD be treated as an error.
7.3. Transfer Coding Registry 7.3. Transfer Coding Registry
The "HTTP Transfer Coding Registry" defines the namespace for The "HTTP Transfer Coding Registry" defines the namespace for
transfer coding names. It is maintained at transfer coding names. It is maintained at
<http://www.iana.org/assignments/http-parameters>. <https://www.iana.org/assignments/http-parameters>.
8.4.1. Procedure
Registrations MUST include the following fields: Registrations MUST include the following fields:
o Name o Name
o Description o Description
o Pointer to specification text o Pointer to specification text
Names of transfer codings MUST NOT overlap with names of content Names of transfer codings MUST NOT overlap with names of content
codings (Section 3.1.2.1 of [RFC7231]) unless the encoding codings (Section 7.5.1 of [Semantics]) unless the encoding
transformation is identical, as is the case for the compression transformation is identical, as is the case for the compression
codings defined in Section 4.2. codings defined in Section 7.2.
Values to be added to this namespace require IETF Review (see Section The TE header field (Section 9.1.4 of [Semantics]) uses a pseudo
4.1 of [RFC5226]), and MUST conform to the purpose of transfer coding parameter named "q" as rank value when multiple transfer codings are
defined in this specification. acceptable. Future registrations of transfer codings SHOULD NOT
define parameters called "q" (case-insensitively) in order to avoid
ambiguities.
Values to be added to this namespace require IETF Review (see
Section 4.8 of [RFC8126]), and MUST conform to the purpose of
transfer coding defined in this specification.
Use of program names for the identification of encoding formats is Use of program names for the identification of encoding formats is
not desirable and is discouraged for future encodings. not desirable and is discouraged for future encodings.
7.4. Negotiating Transfer Codings 7.4. Negotiating Transfer Codings
The TE field (Section 9.1.4 of [Semantics]) is used in HTTP/1.1 to
indicate what transfer-codings, besides chunked, the client is
willing to accept in the response, and whether or not the client is
willing to accept trailer fields in a chunked transfer coding.
A client MUST NOT send the chunked transfer coding name in TE;
chunked is always acceptable for HTTP/1.1 recipients.
Three examples of TE use are below. Three examples of TE use are below.
TE: deflate TE: deflate
TE: TE:
TE: trailers, deflate;q=0.5 TE: trailers, deflate;q=0.5
The presence of the keyword "trailers" indicates that the client is
willing to accept trailer fields in a chunked transfer coding, as
defined in Section 4.1.2, on behalf of itself and any downstream
clients. For requests from an intermediary, this implies that
either: (a) all downstream clients are willing to accept trailer
fields in the forwarded response; or, (b) the intermediary will
attempt to buffer the response on behalf of downstream recipients.
Note that HTTP/1.1 does not define any means to limit the size of a
chunked response such that an intermediary can be assured of
buffering the entire response.
When multiple transfer codings are acceptable, the client MAY rank When multiple transfer codings are acceptable, the client MAY rank
the codings by preference using a case-insensitive "q" parameter the codings by preference using a case-insensitive "q" parameter
(similar to the qvalues used in content negotiation fields, Section (similar to the qvalues used in content negotiation fields,
5.3.1 of [RFC7231]). The rank value is a real number in the range 0 Section 11.1.1.2 of [Semantics]). The rank value is a real number in
through 1, where 0.001 is the least preferred and 1 is the most the range 0 through 1, where 0.001 is the least preferred and 1 is
preferred; a value of 0 means "not acceptable". the most preferred; a value of 0 means "not acceptable".
If the TE field-value is empty or if no TE field is present, the only If the TE field value is empty or if no TE field is present, the only
acceptable transfer coding is chunked. A message with no transfer acceptable transfer coding is chunked. A message with no transfer
coding is always acceptable. coding is always acceptable.
The keyword "trailers" indicates that the sender will not discard
trailer fields, as described in Section 5.6 of [Semantics].
Since the TE header field only applies to the immediate connection, a Since the TE header field only applies to the immediate connection, a
sender of TE MUST also send a "TE" connection option within the sender of TE MUST also send a "TE" connection option within the
Connection header field (Section 6.1) in order to prevent the TE Connection header field (Section 6.4.1 of [Semantics]) in order to
field from being forwarded by intermediaries that do not support its prevent the TE field from being forwarded by intermediaries that do
semantics. not support its semantics.
8. Handling Incomplete Messages 8. Handling Incomplete Messages
A server that receives an incomplete request message, usually due to A server that receives an incomplete request message, usually due to
a canceled request or a triggered timeout exception, MAY send an a canceled request or a triggered timeout exception, MAY send an
error response prior to closing the connection. error response prior to closing the connection.
A client that receives an incomplete response message, which can A client that receives an incomplete response message, which can
occur when a connection is closed prematurely or when decoding a occur when a connection is closed prematurely or when decoding a
supposedly chunked transfer coding fails, MUST record the message as supposedly chunked transfer coding fails, MUST record the message as
incomplete. Cache requirements for incomplete responses are defined incomplete. Cache requirements for incomplete responses are defined
in Section 3 of [RFC7234]. in Section 3 of [Caching].
If a response terminates in the middle of the header section (before If a response terminates in the middle of the header section (before
the empty line is received) and the status code might rely on header the empty line is received) and the status code might rely on header
fields to convey the full meaning of the response, then the client fields to convey the full meaning of the response, then the client
cannot assume that meaning has been conveyed; the client might need cannot assume that meaning has been conveyed; the client might need
to repeat the request in order to determine what action to take next. to repeat the request in order to determine what action to take next.
A message body that uses the chunked transfer coding is incomplete if A message body that uses the chunked transfer coding is incomplete if
the zero-sized chunk that terminates the encoding has not been the zero-sized chunk that terminates the encoding has not been
received. A message that uses a valid Content-Length is incomplete received. A message that uses a valid Content-Length is incomplete
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9. Connection Management 9. Connection Management
HTTP messaging is independent of the underlying transport- or HTTP messaging is independent of the underlying transport- or
session-layer connection protocol(s). HTTP only presumes a reliable session-layer connection protocol(s). HTTP only presumes a reliable
transport with in-order delivery of requests and the corresponding transport with in-order delivery of requests and the corresponding
in-order delivery of responses. The mapping of HTTP request and in-order delivery of responses. The mapping of HTTP request and
response structures onto the data units of an underlying transport response structures onto the data units of an underlying transport
protocol is outside the scope of this specification. protocol is outside the scope of this specification.
As described in Section 5.2, the specific connection protocols to be As described in Section 6.2 of [Semantics], the specific connection
used for an HTTP interaction are determined by client configuration protocols to be used for an HTTP interaction are determined by client
and the target URI. For example, the "http" URI scheme configuration and the target URI. For example, the "http" URI scheme
(Section 2.7.1) indicates a default connection of TCP over IP, with a (Section 4.2.1 of [Semantics]) indicates a default connection of TCP
default TCP port of 80, but the client might be configured to use a over IP, with a default TCP port of 80, but the client might be
proxy via some other connection, port, or protocol. configured to use a proxy via some other connection, port, or
protocol.
HTTP implementations are expected to engage in connection management, HTTP implementations are expected to engage in connection management,
which includes maintaining the state of current connections, which includes maintaining the state of current connections,
establishing a new connection or reusing an existing connection, establishing a new connection or reusing an existing connection,
processing messages received on a connection, detecting connection processing messages received on a connection, detecting connection
failures, and closing each connection. Most clients maintain failures, and closing each connection. Most clients maintain
multiple connections in parallel, including more than one connection multiple connections in parallel, including more than one connection
per server endpoint. Most servers are designed to maintain thousands per server endpoint. Most servers are designed to maintain thousands
of concurrent connections, while controlling request queues to enable of concurrent connections, while controlling request queues to enable
fair use and detect denial-of-service attacks. fair use and detect denial-of-service attacks.
9.2. Establishment 9.1. Establishment
It is beyond the scope of this specification to describe how It is beyond the scope of this specification to describe how
connections are established via various transport- or session-layer connections are established via various transport- or session-layer
protocols. Each connection applies to only one transport link. protocols. Each connection applies to only one transport link.
9.3. Associating a Response to a Request 9.2. Associating a Response to a Request
HTTP does not include a request identifier for associating a given HTTP/1.1 does not include a request identifier for associating a
request message with its corresponding one or more response messages. given request message with its corresponding one or more response
Hence, it relies on the order of response arrival to correspond messages. Hence, it relies on the order of response arrival to
exactly to the order in which requests are made on the same correspond exactly to the order in which requests are made on the
connection. More than one response message per request only occurs same connection. More than one response message per request only
when one or more informational responses (1xx, see Section 6.2 of occurs when one or more informational responses (1xx, see
[RFC7231]) precede a final response to the same request. Section 14.2 of [Semantics]) precede a final response to the same
request.
A client that has more than one outstanding request on a connection A client that has more than one outstanding request on a connection
MUST maintain a list of outstanding requests in the order sent and MUST maintain a list of outstanding requests in the order sent and
MUST associate each received response message on that connection to MUST associate each received response message on that connection to
the highest ordered request that has not yet received a final the highest ordered request that has not yet received a final (non-
(non-1xx) response. 1xx) response.
9.4. Persistence If an HTTP/1.1 client receives data on a connection that doesn't have
any outstanding requests, it MUST NOT consider them to be a response
to a not-yet-issued request; it SHOULD close the connection, since
message delimitation is now ambiguous, unless the data consists only
of one or more CRLF (which can be discarded, as per Section 2.2).
9.3. Persistence
HTTP/1.1 defaults to the use of "persistent connections", allowing HTTP/1.1 defaults to the use of "persistent connections", allowing
multiple requests and responses to be carried over a single multiple requests and responses to be carried over a single
connection. The "close" connection option is used to signal that a connection. The "close" connection option is used to signal that a
connection will not persist after the current request/response. HTTP connection will not persist after the current request/response. HTTP
implementations SHOULD support persistent connections. implementations SHOULD support persistent connections.
A recipient determines whether a connection is persistent or not A recipient determines whether a connection is persistent or not
based on the most recently received message's protocol version and based on the most recently received message's protocol version and
Connection header field (if any): Connection header field (Section 6.4.1 of [Semantics]), if any:
o If the "close" connection option is present, the connection will o If the "close" connection option is present, the connection will
not persist after the current response; else, not persist after the current response; else,
o If the received protocol is HTTP/1.1 (or later), the connection o If the received protocol is HTTP/1.1 (or later), the connection
will persist after the current response; else, will persist after the current response; else,
o If the received protocol is HTTP/1.0, the "keep-alive" connection o If the received protocol is HTTP/1.0, the "keep-alive" connection
option is present, the recipient is not a proxy, and the recipient option is present, either the recipient is not a proxy or the
wishes to honor the HTTP/1.0 "keep-alive" mechanism, the message is a response, and the recipient wishes to honor the
connection will persist after the current response; otherwise, HTTP/1.0 "keep-alive" mechanism, the connection will persist after
the current response; otherwise,
o The connection will close after the current response. o The connection will close after the current response.
A client that does not support persistent connections MUST send the
"close" connection option in every request message.
A server that does not support persistent connections MUST send the
"close" connection option in every response message that does not
have a 1xx (Informational) status code.
A client MAY send additional requests on a persistent connection A client MAY send additional requests on a persistent connection
until it sends or receives a "close" connection option or receives an until it sends or receives a "close" connection option or receives an
HTTP/1.0 response without a "keep-alive" connection option. HTTP/1.0 response without a "keep-alive" connection option.
In order to remain persistent, all messages on a connection need to In order to remain persistent, all messages on a connection need to
have a self-defined message length (i.e., one not defined by closure have a self-defined message length (i.e., one not defined by closure
of the connection), as described in Section 3.3. A server MUST read of the connection), as described in Section 6. A server MUST read
the entire request message body or close the connection after sending the entire request message body or close the connection after sending
its response, since otherwise the remaining data on a persistent its response, since otherwise the remaining data on a persistent
connection would be misinterpreted as the next request. Likewise, a connection would be misinterpreted as the next request. Likewise, a
client MUST read the entire response message body if it intends to client MUST read the entire response message body if it intends to
reuse the same connection for a subsequent request. reuse the same connection for a subsequent request.
A proxy server MUST NOT maintain a persistent connection with an A proxy server MUST NOT maintain a persistent connection with an
HTTP/1.0 client (see Section 19.7.1 of [RFC2068] for information and HTTP/1.0 client (see Section 19.7.1 of [RFC2068] for information and
discussion of the problems with the Keep-Alive header field discussion of the problems with the Keep-Alive header field
implemented by many HTTP/1.0 clients). implemented by many HTTP/1.0 clients).
See Appendix A.1.2 for more information on backwards compatibility See Appendix C.1.2 for more information on backwards compatibility
with HTTP/1.0 clients. with HTTP/1.0 clients.
6.3.1. Retrying Requests 9.3.1. Retrying Requests
Connections can be closed at any time, with or without intention. Connections can be closed at any time, with or without intention.
Implementations ought to anticipate the need to recover from Implementations ought to anticipate the need to recover from
asynchronous close events. asynchronous close events. The conditions under which a client can
automatically retry a sequence of outstanding requests are defined in
When an inbound connection is closed prematurely, a client MAY open a Section 8.2.2 of [Semantics].
new connection and automatically retransmit an aborted sequence of
requests if all of those requests have idempotent methods (Section
4.2.2 of [RFC7231]).
6.3.2. Pipelining 9.3.2. Pipelining
A client that supports persistent connections MAY "pipeline" its A client that supports persistent connections MAY "pipeline" its
requests (i.e., send multiple requests without waiting for each requests (i.e., send multiple requests without waiting for each
response). A server MAY process a sequence of pipelined requests in response). A server MAY process a sequence of pipelined requests in
parallel if they all have safe methods (Section 4.2.1 of [RFC7231]), parallel if they all have safe methods (Section 8.2.1 of
but it MUST send the corresponding responses in the same order that [Semantics]), but it MUST send the corresponding responses in the
the requests were received. same order that the requests were received.
A client that pipelines requests SHOULD retry unanswered requests if A client that pipelines requests SHOULD retry unanswered requests if
the connection closes before it receives all of the corresponding the connection closes before it receives all of the corresponding
responses. When retrying pipelined requests after a failed responses. When retrying pipelined requests after a failed
connection (a connection not explicitly closed by the server in its connection (a connection not explicitly closed by the server in its
last complete response), a client MUST NOT pipeline immediately after last complete response), a client MUST NOT pipeline immediately after
connection establishment, since the first remaining request in the connection establishment, since the first remaining request in the
prior pipeline might have caused an error response that can be lost prior pipeline might have caused an error response that can be lost
again if multiple requests are sent on a prematurely closed again if multiple requests are sent on a prematurely closed
connection (see the TCP reset problem described in Section 6.6). connection (see the TCP reset problem described in Section 9.6).
Idempotent methods (Section 4.2.2 of [RFC7231]) are significant to Idempotent methods (Section 8.2.2 of [Semantics]) are significant to
pipelining because they can be automatically retried after a pipelining because they can be automatically retried after a
connection failure. A user agent SHOULD NOT pipeline requests after connection failure. A user agent SHOULD NOT pipeline requests after
a non-idempotent method, until the final response status code for a non-idempotent method, until the final response status code for
that method has been received, unless the user agent has a means to that method has been received, unless the user agent has a means to
detect and recover from partial failure conditions involving the detect and recover from partial failure conditions involving the
pipelined sequence. pipelined sequence.
An intermediary that receives pipelined requests MAY pipeline those An intermediary that receives pipelined requests MAY pipeline those
requests when forwarding them inbound, since it can rely on the requests when forwarding them inbound, since it can rely on the
outbound user agent(s) to determine what requests can be safely outbound user agent(s) to determine what requests can be safely
pipelined. If the inbound connection fails before receiving a pipelined. If the inbound connection fails before receiving a
response, the pipelining intermediary MAY attempt to retry a sequence response, the pipelining intermediary MAY attempt to retry a sequence
of requests that have yet to receive a response if the requests all of requests that have yet to receive a response if the requests all
have idempotent methods; otherwise, the pipelining intermediary have idempotent methods; otherwise, the pipelining intermediary
SHOULD forward any received responses and then close the SHOULD forward any received responses and then close the
corresponding outbound connection(s) so that the outbound user corresponding outbound connection(s) so that the outbound user
agent(s) can recover accordingly. agent(s) can recover accordingly.
6.4. Concurrency 9.4. Concurrency
A client ought to limit the number of simultaneous open connections A client ought to limit the number of simultaneous open connections
that it maintains to a given server. that it maintains to a given server.
Previous revisions of HTTP gave a specific number of connections as a Previous revisions of HTTP gave a specific number of connections as a
ceiling, but this was found to be impractical for many applications. ceiling, but this was found to be impractical for many applications.
As a result, this specification does not mandate a particular maximum As a result, this specification does not mandate a particular maximum
number of connections but, instead, encourages clients to be number of connections but, instead, encourages clients to be
conservative when opening multiple connections. conservative when opening multiple connections.
Multiple connections are typically used to avoid the "head-of-line Multiple connections are typically used to avoid the "head-of-line
blocking" problem, wherein a request that takes significant blocking" problem, wherein a request that takes significant server-
server-side processing and/or has a large payload blocks subsequent side processing and/or has a large payload blocks subsequent requests
requests on the same connection. However, each connection consumes on the same connection. However, each connection consumes server
server resources. Furthermore, using multiple connections can cause resources. Furthermore, using multiple connections can cause
undesirable side effects in congested networks. undesirable side effects in congested networks.
Note that a server might reject traffic that it deems abusive or Note that a server might reject traffic that it deems abusive or
characteristic of a denial-of-service attack, such as an excessive characteristic of a denial-of-service attack, such as an excessive
number of open connections from a single client. number of open connections from a single client.
6.5. Failures and Timeouts 9.5. Failures and Timeouts
Servers will usually have some timeout value beyond which they will Servers will usually have some timeout value beyond which they will
no longer maintain an inactive connection. Proxy servers might make no longer maintain an inactive connection. Proxy servers might make
this a higher value since it is likely that the client will be making this a higher value since it is likely that the client will be making
more connections through the same proxy server. The use of more connections through the same proxy server. The use of
persistent connections places no requirements on the length (or persistent connections places no requirements on the length (or
existence) of this timeout for either the client or the server. existence) of this timeout for either the client or the server.
A client or server that wishes to time out SHOULD issue a graceful A client or server that wishes to time out SHOULD issue a graceful
close on the connection. Implementations SHOULD constantly monitor close on the connection. Implementations SHOULD constantly monitor
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expectation that clients will retry. The latter technique can expectation that clients will retry. The latter technique can
exacerbate network congestion. exacerbate network congestion.
A client sending a message body SHOULD monitor the network connection A client sending a message body SHOULD monitor the network connection
for an error response while it is transmitting the request. If the for an error response while it is transmitting the request. If the
client sees a response that indicates the server does not wish to client sees a response that indicates the server does not wish to
receive the message body and is closing the connection, the client receive the message body and is closing the connection, the client
SHOULD immediately cease transmitting the body and close its side of SHOULD immediately cease transmitting the body and close its side of
the connection. the connection.
6.6. Tear-down 9.6. Tear-down
The Connection header field (Section 6.1) provides a "close" The Connection header field (Section 6.4.1 of [Semantics]) provides a
connection option that a sender SHOULD send when it wishes to close "close" connection option that a sender SHOULD send when it wishes to
the connection after the current request/response pair. close the connection after the current request/response pair.
A client that sends a "close" connection option MUST NOT send further A client that sends a "close" connection option MUST NOT send further
requests on that connection (after the one containing "close") and requests on that connection (after the one containing "close") and
MUST close the connection after reading the final response message MUST close the connection after reading the final response message
corresponding to this request. corresponding to this request.
A server that receives a "close" connection option MUST initiate a A server that receives a "close" connection option MUST initiate a
close of the connection (see below) after it sends the final response close of the connection (see below) after it sends the final response
to the request that contained "close". The server SHOULD send a to the request that contained "close". The server SHOULD send a
"close" connection option in its final response on that connection. "close" connection option in its final response on that connection.
skipping to change at line 1462 skipping to change at page 33, line 45
the write side of the read/write connection. The server then the write side of the read/write connection. The server then
continues to read from the connection until it receives a continues to read from the connection until it receives a
corresponding close by the client, or until the server is reasonably corresponding close by the client, or until the server is reasonably
certain that its own TCP stack has received the client's certain that its own TCP stack has received the client's
acknowledgement of the packet(s) containing the server's last acknowledgement of the packet(s) containing the server's last
response. Finally, the server fully closes the connection. response. Finally, the server fully closes the connection.
It is unknown whether the reset problem is exclusive to TCP or might It is unknown whether the reset problem is exclusive to TCP or might
also be found in other transport connection protocols. also be found in other transport connection protocols.
9.7. TLS Connection Initiation Note that a TCP connection that is half-closed by the client does not
delimit a request message, nor does it imply that the client is no
5.4.3. Initiating HTTP Over TLS [RFC2818] longer interested in a response. In general, transport signals
cannot be relied upon to signal edge cases, since HTTP/1.1 is
independent of transport.
Conceptually, HTTP/TLS is very simple. Simply use HTTP over TLS 9.7. TLS Connection Initiation
precisely as you would use HTTP over TCP.
2.1. Connection Initiation Conceptually, HTTP/TLS is simply sending HTTP messages over a
connection secured via TLS [RFC8446].
The agent acting as the HTTP client should also act as the TLS The HTTP client also acts as the TLS client. It initiates a
client. It should initiate a connection to the server on the connection to the server on the appropriate port and sends the TLS
appropriate port and then send the TLS ClientHello to begin the TLS ClientHello to begin the TLS handshake. When the TLS handshake has
handshake. When the TLS handshake has finished. The client may then finished, the client may then initiate the first HTTP request. All
initiate the first HTTP request. All HTTP data MUST be sent as TLS HTTP data MUST be sent as TLS "application data", but is otherwise
"application data". Normal HTTP behavior, including retained treated like a normal connection for HTTP (including potential reuse
connections should be followed. as a persistent connection).
9.8. TLS Connection Closure 9.8. TLS Connection Closure
TLS provides a facility for secure connection closure. When a valid TLS provides a facility for secure connection closure. When a valid
closure alert is received, an implementation can be assured that no closure alert is received, an implementation can be assured that no
further data will be received on that connection. TLS further data will be received on that connection. TLS
implementations MUST initiate an exchange of closure alerts before implementations MUST initiate an exchange of closure alerts before
closing a connection. A TLS implementation MAY, after sending a closing a connection. A TLS implementation MAY, after sending a
closure alert, close the connection without waiting for the peer to closure alert, close the connection without waiting for the peer to
send its closure alert, generating an "incomplete close". Note that send its closure alert, generating an "incomplete close". Note that
an implementation which does this MAY choose to reuse the session. an implementation which does this MAY choose to reuse the session.
This SHOULD only be done when the application knows (typically This SHOULD only be done when the application knows (typically
through detecting HTTP message boundaries) that it has received all through detecting HTTP message boundaries) that it has received all
the message data that it cares about. the message data that it cares about.
As specified in [RFC2246], any implementation which receives a As specified in [RFC8446], any implementation which receives a
connection close without first receiving a valid closure alert (a connection close without first receiving a valid closure alert (a
"premature close") MUST NOT reuse that session. Note that a "premature close") MUST NOT reuse that session. Note that a
premature close does not call into question the security of the data premature close does not call into question the security of the data
already received, but simply indicates that subsequent data might already received, but simply indicates that subsequent data might
have been truncated. Because TLS is oblivious to HTTP have been truncated. Because TLS is oblivious to HTTP request/
request/response boundaries, it is necessary to examine the HTTP data response boundaries, it is necessary to examine the HTTP data itself
itself (specifically the Content-Length header) to determine whether (specifically the Content-Length header) to determine whether the
the truncation occurred inside a message or between messages. truncation occurred inside a message or between messages.
2.2.1. Client Behavior
Because HTTP uses connection closure to signal end of server data,
client implementations MUST treat any premature closes as errors and
the data received as potentially truncated. While in some cases the
HTTP protocol allows the client to find out whether truncation took
place so that, if it received the complete reply, it may tolerate
such errors following the principle to "[be] strict when sending and
tolerant when receiving" [RFC1958], often truncation does not show in
the HTTP protocol data; two cases in particular deserve special note:
A HTTP response without a Content-Length header. Since data length
in this situation is signalled by connection close a premature
close generated by the server cannot be distinguished from a
spurious close generated by an attacker.
A HTTP response with a valid Content-Length header closed before
all data has been read. Because TLS does not provide document
oriented protection, it is impossible to determine whether the
server has miscomputed the Content-Length or an attacker has
truncated the connection.
There is one exception to the above rule.
When encountering a premature close, a client SHOULD treat as When encountering a premature close, a client SHOULD treat as
completed all requests for which it has received as much data as completed all requests for which it has received as much data as
specified in the Content-Length header. specified in the Content-Length header.
A client detecting an incomplete close SHOULD recover gracefully. It A client detecting an incomplete close SHOULD recover gracefully. It
MAY resume a TLS session closed in this fashion. MAY resume a TLS session closed in this fashion.
Clients MUST send a closure alert before closing the connection. Clients MUST send a closure alert before closing the connection.
Clients which are unprepared to receive any more data MAY choose not Clients which are unprepared to receive any more data MAY choose not
to wait for the server's closure alert and simply close the to wait for the server's closure alert and simply close the
connection, thus generating an incomplete close on the server side. connection, thus generating an incomplete close on the server side.
2.2.2. Server Behavior Servers SHOULD be prepared to receive an incomplete close from the
client, since the client can often determine when the end of server
RFC 2616 permits an HTTP client to close the connection at any time, data is. Servers SHOULD be willing to resume TLS sessions closed in
and requires servers to recover gracefully. In particular, servers this fashion.
SHOULD be prepared to receive an incomplete close from the client,
since the client can often determine when the end of server data is.
Servers SHOULD be willing to resume TLS sessions closed in this
fashion.
Implementation note: In HTTP implementations which do not use
persistent connections, the server ordinarily expects to be able to
signal end of data by closing the connection. When Content-Length is
used, however, the client may have already sent the closure alert and
dropped the connection.
Servers MUST attempt to initiate an exchange of closure alerts with Servers MUST attempt to initiate an exchange of closure alerts with
the client before closing the connection. Servers MAY close the the client before closing the connection. Servers MAY close the
connection after sending the closure alert, thus generating an connection after sending the closure alert, thus generating an
incomplete close on the client side. incomplete close on the client side.
X. Enclosing Messages as Data 10. Enclosing Messages as Data
8.3.1. Internet Media Type message/http 10.1. Media Type message/http
The message/http type can be used to enclose a single HTTP request or The message/http media type can be used to enclose a single HTTP
response message, provided that it obeys the MIME restrictions for request or response message, provided that it obeys the MIME
all "message" types regarding line length and encodings. restrictions for all "message" types regarding line length and
encodings.
Type name: message Type name: message
Subtype name: http Subtype name: http
Required parameters: N/A Required parameters: N/A
Optional parameters: version, msgtype Optional parameters: version, msgtype
version: The HTTP-version number of the enclosed message (e.g., version: The HTTP-version number of the enclosed message (e.g.,
"1.1"). If not present, the version can be determined from the "1.1"). If not present, the version can be determined from the
first line of the body. first line of the body.
msgtype: The message type -- "request" or "response". If not msgtype: The message type - "request" or "response". If not
present, the type can be determined from the first line of the present, the type can be determined from the first line of the
body. body.
Encoding considerations: only "7bit", "8bit", or "binary" are Encoding considerations: only "7bit", "8bit", or "binary" are
permitted permitted
Security considerations: see Section 9 Security considerations: see Section 11
Interoperability considerations: N/A Interoperability considerations: N/A
Published specification: This specification (see Section 8.3.1). Published specification: This specification (see Section 10.1).
Applications that use this media type: N/A Applications that use this media type: N/A
Fragment identifier considerations: N/A Fragment identifier considerations: N/A
Additional information: Magic number(s): N/A
Additional information: Deprecated alias names for this type: N/A
Magic number(s): N/A
Deprecated alias names for this type: N/A
File extension(s): N/A File extension(s): N/A
Macintosh file type code(s): N/A Macintosh file type code(s): N/A
Person and email address to contact for further information: Person and email address to contact for further information: See Aut
See Authors' Addresses section. hors' Addresses section.
Intended usage: COMMON Intended usage: COMMON
Restrictions on usage: N/A Restrictions on usage: N/A
Author: See Authors' Addresses section. Author: See Authors' Addresses section.
Change controller: IESG Change controller: IESG
8.3.2. Internet Media Type application/http 10.2. Media Type application/http
The application/http type can be used to enclose a pipeline of one or The application/http media type can be used to enclose a pipeline of
more HTTP request or response messages (not intermixed). one or more HTTP request or response messages (not intermixed).
Type name: application Type name: application
Subtype name: http Subtype name: http
Required parameters: N/A Required parameters: N/A
Optional parameters: version, msgtype Optional parameters: version, msgtype
version: The HTTP-version number of the enclosed messages (e.g., version: The HTTP-version number of the enclosed messages (e.g.,
"1.1"). If not present, the version can be determined from the "1.1"). If not present, the version can be determined from the
first line of the body. first line of the body.
msgtype: The message type -- "request" or "response". If not msgtype: The message type - "request" or "response". If not
present, the type can be determined from the first line of the present, the type can be determined from the first line of the
body. body.
Encoding considerations: HTTP messages enclosed by this type are in Encoding considerations: HTTP messages enclosed by this type are in
"binary" format; use of an appropriate Content-Transfer-Encoding "binary" format; use of an appropriate Content-Transfer-Encoding
is required when transmitted via email. is required when transmitted via email.
Security considerations: see Section 9 Security considerations: see Section 11
Interoperability considerations: N/A Interoperability considerations: N/A
Published specification: This specification (see Section 10.2).
Published specification: This specification (see Section 8.3.2).
Applications that use this media type: N/A Applications that use this media type: N/A
Fragment identifier considerations: N/A Fragment identifier considerations: N/A
Additional information: Additional information: Deprecated alias names for this type: N/A
Deprecated alias names for this type: N/A
Magic number(s): N/A Magic number(s): N/A
File extension(s): N/A File extension(s): N/A
Macintosh file type code(s): N/A Macintosh file type code(s): N/A
Person and email address to contact for further information: Person and email address to contact for further information: See Aut
See Authors' Addresses section. hors' Addresses section.
Intended usage: COMMON Intended usage: COMMON
Restrictions on usage: N/A Restrictions on usage: N/A
Author: See Authors' Addresses section. Author: See Authors' Addresses section.
Change controller: IESG Change controller: IESG
9. Security Considerations 11. Security Considerations
This section is meant to inform developers, information providers, This section is meant to inform developers, information providers,
and users of known security considerations relevant to HTTP message and users of known security considerations relevant to HTTP message
syntax, parsing, and routing. Security considerations about HTTP syntax, parsing, and routing. Security considerations about HTTP
semantics and payloads are addressed in [RFC7231]. semantics and payloads are addressed in [Semantics].
9.4. Response Splitting 11.1. Response Splitting
Response splitting (a.k.a, CRLF injection) is a common technique, Response splitting (a.k.a, CRLF injection) is a common technique,
used in various attacks on Web usage, that exploits the line-based used in various attacks on Web usage, that exploits the line-based
nature of HTTP message framing and the ordered association of nature of HTTP message framing and the ordered association of
requests to responses on persistent connections [Klein]. This requests to responses on persistent connections [Klein]. This
technique can be particularly damaging when the requests pass through technique can be particularly damaging when the requests pass through
a shared cache. a shared cache.
Response splitting exploits a vulnerability in servers (usually Response splitting exploits a vulnerability in servers (usually
within an application server) where an attacker can send encoded data within an application server) where an attacker can send encoded data
skipping to change at line 1721 skipping to change at page 38, line 29
However, that assumes the application server is only performing URI However, that assumes the application server is only performing URI
decoding, rather than more obscure data transformations like charset decoding, rather than more obscure data transformations like charset
transcoding, XML entity translation, base64 decoding, sprintf transcoding, XML entity translation, base64 decoding, sprintf
reformatting, etc. A more effective mitigation is to prevent reformatting, etc. A more effective mitigation is to prevent
anything other than the server's core protocol libraries from sending anything other than the server's core protocol libraries from sending
a CR or LF within the header section, which means restricting the a CR or LF within the header section, which means restricting the
output of header fields to APIs that filter for bad octets and not output of header fields to APIs that filter for bad octets and not
allowing application servers to write directly to the protocol allowing application servers to write directly to the protocol
stream. stream.
9.5. Request Smuggling 11.2. Request Smuggling
Request smuggling ([Linhart]) is a technique that exploits Request smuggling ([Linhart]) is a technique that exploits
differences in protocol parsing among various recipients to hide differences in protocol parsing among various recipients to hide
additional requests (which might otherwise be blocked or disabled by additional requests (which might otherwise be blocked or disabled by
policy) within an apparently harmless request. Like response policy) within an apparently harmless request. Like response
splitting, request smuggling can lead to a variety of attacks on HTTP splitting, request smuggling can lead to a variety of attacks on HTTP
usage. usage.
This specification has introduced new requirements on request This specification has introduced new requirements on request
parsing, particularly with regard to message framing in parsing, particularly with regard to message framing in Section 6.3,
Section 3.3.3, to reduce the effectiveness of request smuggling. to reduce the effectiveness of request smuggling.
9.6. Message Integrity 11.3. Message Integrity
HTTP does not define a specific mechanism for ensuring message HTTP does not define a specific mechanism for ensuring message
integrity, instead relying on the error-detection ability of integrity, instead relying on the error-detection ability of
underlying transport protocols and the use of length or underlying transport protocols and the use of length or chunk-
chunk-delimited framing to detect completeness. Additional integrity delimited framing to detect completeness. Additional integrity
mechanisms, such as hash functions or digital signatures applied to mechanisms, such as hash functions or digital signatures applied to
the content, can be selectively added to messages via extensible the content, can be selectively added to messages via extensible
metadata header fields. Historically, the lack of a single integrity metadata fields. Historically, the lack of a single integrity
mechanism has been justified by the informal nature of most HTTP mechanism has been justified by the informal nature of most HTTP
communication. However, the prevalence of HTTP as an information communication. However, the prevalence of HTTP as an information
access mechanism has resulted in its increasing use within access mechanism has resulted in its increasing use within
environments where verification of message integrity is crucial. environments where verification of message integrity is crucial.
User agents are encouraged to implement configurable means for User agents are encouraged to implement configurable means for
detecting and reporting failures of message integrity such that those detecting and reporting failures of message integrity such that those
means can be enabled within environments for which integrity is means can be enabled within environments for which integrity is
necessary. For example, a browser being used to view medical history necessary. For example, a browser being used to view medical history
or drug interaction information needs to indicate to the user when or drug interaction information needs to indicate to the user when
such information is detected by the protocol to be incomplete, such information is detected by the protocol to be incomplete,
expired, or corrupted during transfer. Such mechanisms might be expired, or corrupted during transfer. Such mechanisms might be
selectively enabled via user agent extensions or the presence of selectively enabled via user agent extensions or the presence of
message integrity metadata in a response. At a minimum, user agents message integrity metadata in a response. At a minimum, user agents
ought to provide some indication that allows a user to distinguish ought to provide some indication that allows a user to distinguish
between a complete and incomplete response message (Section 3.4) when between a complete and incomplete response message (Section 8) when
such verification is desired. such verification is desired.
9.7. Message Confidentiality 11.4. Message Confidentiality
HTTP relies on underlying transport protocols to provide message HTTP relies on underlying transport protocols to provide message
confidentiality when that is desired. HTTP has been specifically confidentiality when that is desired. HTTP has been specifically
designed to be independent of the transport protocol, such that it designed to be independent of the transport protocol, such that it
can be used over many different forms of encrypted connection, with can be used over many different forms of encrypted connection, with
the selection of such transports being identified by the choice of the selection of such transports being identified by the choice of
URI scheme or within user agent configuration. URI scheme or within user agent configuration.
The "https" scheme can be used to identify resources that require a The "https" scheme can be used to identify resources that require a
confidential connection, as described in Section 2.7.2. confidential connection, as described in Section 4.2.2 of
[Semantics].
12. IANA Considerations 12. IANA Considerations
The change controller is: "IETF (iesg@ietf.org) - Internet The change controller for the following registrations is: "IETF
Engineering Task Force". (iesg@ietf.org) - Internet Engineering Task Force".
12.1. Header Field Registration 12.1. Field Name Registration
HTTP header fields are registered within the "Message Headers" Please update the "Hypertext Transfer Protocol (HTTP) Field Name
registry maintained at Registry" at <https://www.iana.org/assignments/http-fields> with the
<http://www.iana.org/assignments/message-headers/>. field names listed in the two tables of Section 5.
, so the
"Permanent Message Header Field Names" registry has been updated
accordingly (see [BCP90])
12.2. Internet Media Type Registration 12.2. Media Type Registration
IANA maintains the registry of Internet media types [BCP13] at Please update the "Media Types" registry at
<http://www.iana.org/assignments/media-types>. <https://www.iana.org/assignments/media-types> with the registration
information in Section 10.1 and Section 10.2 for the media types
"message/http" and "application/http", respectively.
This document serves as the specification for the Internet media 12.3. Transfer Coding Registration
types "message/http" and "application/http". The following has been
registered with IANA.
12.3. [Transfer Coding] Registration Please update the "HTTP Transfer Coding Registry" at
<https://www.iana.org/assignments/http-parameters/> with the
registration procedure of Section 7.3 and the content coding names
summarized in the table of Section 7.
The "HTTP Transfer Coding Registry" has been updated with the 12.4. ALPN Protocol ID Registration
registrations below:
13. References Please update the "TLS Application-Layer Protocol Negotiation (ALPN)
Protocol IDs" registry at <https://www.iana.org/assignments/tls-
extensiontype-values/tls-extensiontype-values.xhtml> with the
registration below:
13.1. Normative References ---------- ----------------------------- ----------------
Protocol Identification Sequence Reference
---------- ----------------------------- ----------------
HTTP/1.1 0x68 0x74 0x74 0x70 0x2f (this
0x31 0x2e 0x31 ("http/1.1") specification)
---------- ----------------------------- ----------------
[RFC1950] Deutsch, L. and J-L. Gailly, "ZLIB Compressed Data Table 4
Format Specification version 3.3", RFC 1950, May 1996.
[RFC1951] Deutsch, P., "DEFLATE Compressed Data Format 13. References
Specification version 1.3", RFC 1951, May 1996.
[RFC1952] Deutsch, P., Gailly, J-L., Adler, M., Deutsch, L., and 13.1. Normative References
G. Randers-Pehrson, "GZIP file format specification
version 4.3", RFC 1952, May 1996.
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate [Caching] Fielding, R., Ed., Nottingham, M., Ed., and J. Reschke,
Requirement Levels", BCP 14, RFC 2119, March 1997. Ed., "HTTP Caching", Work in Progress, Internet-Draft,
draft-ietf-httpbis-cache-12, October 2, 2020,
<https://tools.ietf.org/html/draft-ietf-httpbis-cache-12>.
[RFC3986] Berners-Lee, T., Fielding, R., and L. Masinter, [RFC1950] Deutsch, L.P. and J-L. Gailly, "ZLIB Compressed Data
"Uniform Resource Identifier (URI): Generic Syntax", Format Specification version 3.3", RFC 1950,
STD 66, RFC 3986, January 2005. DOI 10.17487/RFC1950, May 1996,
<https://www.rfc-editor.org/info/rfc1950>.
[RFC5234] Crocker, D., Ed. and P. Overell, "Augmented BNF for [RFC1951] Deutsch, P., "DEFLATE Compressed Data Format Specification
Syntax Specifications: ABNF", STD 68, RFC 5234, version 1.3", RFC 1951, DOI 10.17487/RFC1951, May 1996,
January 2008. <https://www.rfc-editor.org/info/rfc1951>.
[RFC7231] Fielding, R., Ed. and J. Reschke, Ed., "Hypertext [RFC1952] Deutsch, P., Gailly, J-L., Adler, M., Deutsch, L.P., and
Transfer Protocol (HTTP/1.1): Semantics and Content", G. Randers-Pehrson, "GZIP file format specification
RFC 7231, June 2014. version 4.3", RFC 1952, DOI 10.17487/RFC1952, May 1996,
<https://www.rfc-editor.org/info/rfc1952>.
[RFC7232] Fielding, R., Ed. and J. Reschke, Ed., "Hypertext [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Transfer Protocol (HTTP/1.1): Conditional Requests", Requirement Levels", BCP 14, RFC 2119,
RFC 7232, June 2014. DOI 10.17487/RFC2119, March 1997,
<https://www.rfc-editor.org/info/rfc2119>.
[RFC7233] Fielding, R., Ed., Lafon, Y., Ed., and J. Reschke, Ed., [RFC3986] Berners-Lee, T., Fielding, R., and L. Masinter, "Uniform
"Hypertext Transfer Protocol (HTTP/1.1): Range Resource Identifier (URI): Generic Syntax", STD 66,
Requests", RFC 7233, June 2014. RFC 3986, DOI 10.17487/RFC3986, January 2005,
<https://www.rfc-editor.org/info/rfc3986>.
[RFC7234] Fielding, R., Ed., Nottingham, M., Ed., and J. Reschke, [RFC5234] Crocker, D., Ed. and P. Overell, "Augmented BNF for Syntax
Ed., "Hypertext Transfer Protocol (HTTP/1.1): Caching", Specifications: ABNF", STD 68, RFC 5234,
RFC 7234, June 2014. DOI 10.17487/RFC5234, January 2008,
<https://www.rfc-editor.org/info/rfc5234>.
[RFC7235] Fielding, R., Ed. and J. Reschke, Ed., "Hypertext [RFC7405] Kyzivat, P., "Case-Sensitive String Support in ABNF",
Transfer Protocol (HTTP/1.1): Authentication", RFC 7405, DOI 10.17487/RFC7405, December 2014,
RFC 7235, June 2014. <https://www.rfc-editor.org/info/rfc7405>.
[USASCII] American National Standards Institute, "Coded Character [RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC
Set -- 7-bit American Standard Code for Information 2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174,
Interchange", ANSI X3.4, 1986. May 2017, <https://www.rfc-editor.org/info/rfc8174>.
[Welch] Welch, T., "A Technique for High-Performance Data [RFC8446] Rescorla, E., "The Transport Layer Security (TLS) Protocol
Compression", IEEE Computer 17(6), June 1984. Version 1.3", RFC 8446, DOI 10.17487/RFC8446, August 2018,
<https://www.rfc-editor.org/info/rfc8446>.
13.2. Informative References [Semantics]
Fielding, R., Ed., Nottingham, M., Ed., and J. Reschke,
Ed., "HTTP Semantics", Work in Progress, Internet-Draft,
draft-ietf-httpbis-semantics-12, October 2, 2020,
<https://tools.ietf.org/html/draft-ietf-httpbis-semantics-
12>.
[BCP13] Freed, N., Klensin, J., and T. Hansen, "Media Type [USASCII] American National Standards Institute, "Coded Character
Specifications and Registration Procedures", BCP 13, Set -- 7-bit American Standard Code for Information
RFC 6838, January 2013. Interchange", ANSI X3.4, 1986.
[BCP90] Klyne, G., Nottingham, M., and J. Mogul, "Registration [Welch] Welch, T. A., "A Technique for High-Performance Data
Procedures for Message Header Fields", BCP 90, Compression", IEEE Computer 17(6), June 1984.
RFC 3864, September 2004.
[ISO-8859-1] International Organization for Standardization, 13.2. Informative References
"Information technology -- 8-bit single-byte coded
graphic character sets -- Part 1: Latin alphabet No.
1", ISO/IEC 8859-1:1998, 1998.
[Klein] Klein, A., "Divide and Conquer - HTTP Response [Err4667] RFC Errata, Erratum ID 4667, RFC 7230,
Splitting, Web Cache Poisoning Attacks, and Related <https://www.rfc-editor.org/errata/eid4667>.
Topics", March 2004, <http://packetstormsecurity.com/
papers/general/whitepaper_httpresponse.pdf>.
[Kri2001] Kristol, D., "HTTP Cookies: Standards, Privacy, and [Klein] Klein, A., "Divide and Conquer - HTTP Response Splitting,
Politics", ACM Transactions on Internet Web Cache Poisoning Attacks, and Related Topics", March
Technology 1(2), November 2001, 2004, <http://packetstormsecurity.com/papers/general/
<http://arxiv.org/abs/cs.SE/0105018>. whitepaper_httpresponse.pdf>.
[Linhart] Linhart, C., Klein, A., Heled, R., and S. Orrin, "HTTP [Linhart] Linhart, C., Klein, A., Heled, R., and S. Orrin, "HTTP
Request Smuggling", June 2005, Request Smuggling", June 2005,
<http://www.watchfire.com/news/whitepapers.aspx>. <http://www.watchfire.com/news/whitepapers.aspx>.
[RFC1945] Berners-Lee, T., Fielding, R., and H. Nielsen, [RFC1945] Berners-Lee, T., Fielding, R.T., and H.F. Nielsen,
"Hypertext Transfer Protocol -- HTTP/1.0", RFC 1945, "Hypertext Transfer Protocol -- HTTP/1.0", RFC 1945,
May 1996. DOI 10.17487/RFC1945, May 1996,
<https://www.rfc-editor.org/info/rfc1945>.
[RFC2045] Freed, N. and N. Borenstein, "Multipurpose Internet [RFC2045] Freed, N. and N.S. Borenstein, "Multipurpose Internet Mail
Mail Extensions (MIME) Part One: Format of Internet Extensions (MIME) Part One: Format of Internet Message
Message Bodies", RFC 2045, November 1996. Bodies", RFC 2045, DOI 10.17487/RFC2045, November 1996,
<https://www.rfc-editor.org/info/rfc2045>.
[RFC2046] Freed, N. and N. Borenstein, "Multipurpose Internet Mail [RFC2046] Freed, N. and N. Borenstein, "Multipurpose Internet Mail
Extensions (MIME) Part Two: Media Types", RFC 2046, Extensions (MIME) Part Two: Media Types", RFC 2046,
November 1996. DOI 10.17487/RFC2046, November 1996,
<https://www.rfc-editor.org/info/rfc2046>.
[RFC2047] Moore, K., "MIME (Multipurpose Internet Mail
Extensions) Part Three: Message Header Extensions for
Non-ASCII Text", RFC 2047, November 1996.
[RFC2049] Freed, N. and N. Borenstein, "Multipurpose Internet Mail [RFC2049] Freed, N. and N.S. Borenstein, "Multipurpose Internet Mail
Extensions (MIME) Part Five: Conformance Criteria and Extensions (MIME) Part Five: Conformance Criteria and
Examples", RFC 2049, November 1996. Examples", RFC 2049, DOI 10.17487/RFC2049, November 1996,
<https://www.rfc-editor.org/info/rfc2049>.
[RFC2068] Fielding, R., Gettys, J., Mogul, J., Nielsen, H., and [RFC2068] Fielding, R., Gettys, J., Mogul, J., Nielsen, H., and T.
T. Berners-Lee, "Hypertext Transfer Protocol -- Berners-Lee, "Hypertext Transfer Protocol -- HTTP/1.1",
HTTP/1.1", RFC 2068, January 1997. RFC 2068, DOI 10.17487/RFC2068, January 1997,
<https://www.rfc-editor.org/info/rfc2068>.
[RFC2557] Palme, F., Hopmann, A., Shelness, N., and E. Stefferud, [RFC2557] Palme, F., Hopmann, A., Shelness, N., and E. Stefferud,
"MIME Encapsulation of Aggregate Documents, such as HTML "MIME Encapsulation of Aggregate Documents, such as HTML
(MHTML)", RFC 2557, March 1999. (MHTML)", RFC 2557, DOI 10.17487/RFC2557, March 1999,
<https://www.rfc-editor.org/info/rfc2557>.
[RFC2616] Fielding, R., Gettys, J., Mogul, J., Frystyk, H.,
Masinter, L., Leach, P., and T. Berners-Lee, "Hypertext
Transfer Protocol -- HTTP/1.1", RFC 2616, June 1999.
[RFC2817] Khare, R. and S. Lawrence, "Upgrading to TLS Within
HTTP/1.1", RFC 2817, May 2000.
[RFC5226] Narten, T. and H. Alvestrand, "Guidelines for Writing [RFC5322] Resnick, P., "Internet Message Format", RFC 5322,
an IANA Considerations Section in RFCs", BCP 26, DOI 10.17487/RFC5322, October 2008,
RFC 5226, May 2008. <https://www.rfc-editor.org/info/rfc5322>.
[RFC5322] Resnick, P., "Internet Message Format", RFC 5322, [RFC7230] Fielding, R., Ed. and J. F. Reschke, Ed., "Hypertext
October 2008. Transfer Protocol (HTTP/1.1): Message Syntax and Routing",
RFC 7230, DOI 10.17487/RFC7230, June 2014,
<https://www.rfc-editor.org/info/rfc7230>.
[RFC6265] Barth, A., "HTTP State Management Mechanism", RFC 6265, [RFC7231] Fielding, R., Ed. and J. F. Reschke, Ed., "Hypertext
April 2011. Transfer Protocol (HTTP/1.1): Semantics and Content",
RFC 7231, DOI 10.17487/RFC7231, June 2014,
<https://www.rfc-editor.org/info/rfc7231>.
[RFC6585] Nottingham, M. and R. Fielding, "Additional HTTP Status [RFC8126] Cotton, M., Leiba, B., and T. Narten, "Guidelines for
Codes", RFC 6585, April 2012. Writing an IANA Considerations Section in RFCs", BCP 26,
RFC 8126, DOI 10.17487/RFC8126, June 2017,
<https://www.rfc-editor.org/info/rfc8126>.
Appendix A. Collected ABNF Appendix A. Collected ABNF
BWS = OWS In the collected ABNF below, list rules are expanded as per
Section 5.7.1.1 of [Semantics].
Connection = *( "," OWS ) connection-option *( OWS "," [ OWS
connection-option ] )
Content-Length = 1*DIGIT BWS = <BWS, see [Semantics], Section 5.7.3>
HTTP-message = start-line *( header-field CRLF ) CRLF [ message-body HTTP-message = start-line CRLF *( field-line CRLF ) CRLF [
] message-body ]
HTTP-name = %x48.54.54.50 ; HTTP HTTP-name = %x48.54.54.50 ; HTTP
HTTP-version = HTTP-name "/" DIGIT "." DIGIT HTTP-version = HTTP-name "/" DIGIT "." DIGIT
Host = uri-host [ ":" port ]
OWS = *( SP / HTAB )
RWS = 1*( SP / HTAB ) OWS = <OWS, see [Semantics], Section 5.7.3>
TE = [ ( "," / t-codings ) *( OWS "," [ OWS t-codings ] ) ]
Trailer = *( "," OWS ) field-name *( OWS "," [ OWS field-name ] )
Transfer-Encoding = *( "," OWS ) transfer-coding *( OWS "," [ OWS
transfer-coding ] )
URI-reference = <URI-reference, see [RFC3986], Section 4.1> RWS = <RWS, see [Semantics], Section 5.7.3>
Upgrade = *( "," OWS ) protocol *( OWS "," [ OWS protocol ] )
Via = *( "," OWS ) ( received-protocol RWS received-by [ RWS comment Transfer-Encoding = [ transfer-coding *( OWS "," OWS transfer-coding
] ) *( OWS "," [ OWS ( received-protocol RWS received-by [ RWS ) ]
comment ] ) ] )
absolute-URI = <absolute-URI, see [RFC3986], Section 4.3> absolute-URI = <absolute-URI, see [RFC3986], Section 4.3>
absolute-form = absolute-URI absolute-form = absolute-URI
absolute-path = 1*( "/" segment ) absolute-path = <absolute-path, see [Semantics], Section 4>
asterisk-form = "*" asterisk-form = "*"
authority = <authority, see [RFC3986], Section 3.2> authority = <authority, see [RFC3986], Section 3.2>
authority-form = authority authority-form = authority
chunk = chunk-size [ chunk-ext ] CRLF chunk-data CRLF chunk = chunk-size [ chunk-ext ] CRLF chunk-data CRLF
chunk-data = 1*OCTET chunk-data = 1*OCTET
chunk-ext = *( ";" chunk-ext-name [ "=" chunk-ext-val ] ) chunk-ext = *( BWS ";" BWS chunk-ext-name [ BWS "=" BWS chunk-ext-val
] )
chunk-ext-name = token chunk-ext-name = token
chunk-ext-val = token / quoted-string chunk-ext-val = token / quoted-string
chunk-size = 1*HEXDIG chunk-size = 1*HEXDIG
chunked-body = *chunk last-chunk trailer-part CRLF chunked-body = *chunk last-chunk trailer-section CRLF
comment = "(" *( ctext / quoted-pair / comment ) ")" comment = <comment, see [Semantics], Section 5.7.5>
connection-option = token
ctext = HTAB / SP / %x21-27 ; '!'-'''
/ %x2A-5B ; '*'-'['
/ %x5D-7E ; ']'-'~'
/ obs-text
field-content = field-vchar [ 1*( SP / HTAB ) field-vchar ]
field-name = token
field-value = *( field-content / obs-fold )
field-vchar = VCHAR / obs-text
fragment = <fragment, see [RFC3986], Section 3.5>
header-field = field-name ":" OWS field-value OWS field-line = field-name ":" OWS field-value OWS
http-URI = "http://" authority path-abempty [ "?" query ] [ "#" field-name = <field-name, see [Semantics], Section 5.4.3>
fragment ] field-value = <field-value, see [Semantics], Section 5.4.4>
https-URI = "https://" authority path-abempty [ "?" query ] [ "#"
fragment ]
last-chunk = 1*"0" [ chunk-ext ] CRLF last-chunk = 1*"0" [ chunk-ext ] CRLF
message-body = *OCTET message-body = *OCTET
method = token method = token
obs-fold = CRLF 1*( SP / HTAB ) obs-fold = OWS CRLF RWS
obs-text = %x80-FF obs-text = <obs-text, see [Semantics], Section 5.7.4>
origin-form = absolute-path [ "?" query ] origin-form = absolute-path [ "?" query ]
partial-URI = relative-part [ "?" query ]
path-abempty = <path-abempty, see [RFC3986], Section 3.3>
port = <port, see [RFC3986], Section 3.2.3> port = <port, see [RFC3986], Section 3.2.3>
protocol = protocol-name [ "/" protocol-version ]
protocol-name = token
protocol-version = token
pseudonym = token
qdtext = HTAB / SP / "!" / %x23-5B ; '#'-'['
/ %x5D-7E ; ']'-'~'
/ obs-text
query = <query, see [RFC3986], Section 3.4> query = <query, see [RFC3986], Section 3.4>
quoted-pair = "\" ( HTAB / SP / VCHAR / obs-text ) quoted-string = <quoted-string, see [Semantics], Section 5.7.4>
quoted-string = DQUOTE *( qdtext / quoted-pair ) DQUOTE
rank = ( "0" [ "." *3DIGIT ] ) / ( "1" [ "." *3"0" ] ) reason-phrase = 1*( HTAB / SP / VCHAR / obs-text )
reason-phrase = *( HTAB / SP / VCHAR / obs-text ) request-line = method SP request-target SP HTTP-version
received-by = ( uri-host [ ":" port ] ) / pseudonym
received-protocol = [ protocol-name "/" ] protocol-version
relative-part = <relative-part, see [RFC3986], Section 4.2>
request-line = method SP request-target SP HTTP-version CRLF
request-target = origin-form / absolute-form / authority-form / request-target = origin-form / absolute-form / authority-form /
asterisk-form asterisk-form
scheme = <scheme, see [RFC3986], Section 3.1>
segment = <segment, see [RFC3986], Section 3.3>
start-line = request-line / status-line start-line = request-line / status-line
status-code = 3DIGIT status-code = 3DIGIT
status-line = HTTP-version SP status-code SP reason-phrase CRLF status-line = HTTP-version SP status-code SP [ reason-phrase ]
t-codings = "trailers" / ( transfer-coding [ t-ranking ] ) token = <token, see [Semantics], Section 5.7.2>
t-ranking = OWS ";" OWS "q=" rank trailer-section = *( field-line CRLF )
tchar = "!" / "#" / "$" / "%" / "&" / "'" / "*" / "+" / "-" / "." / transfer-coding = token *( OWS ";" OWS transfer-parameter )
"^" / "_" / "`" / "|" / "~" / DIGIT / ALPHA
token = 1*tchar
trailer-part = *( header-field CRLF )
transfer-coding = "chunked" / "compress" / "deflate" / "gzip" /
transfer-extension
transfer-extension = token *( OWS ";" OWS transfer-parameter )
transfer-parameter = token BWS "=" BWS ( token / quoted-string ) transfer-parameter = token BWS "=" BWS ( token / quoted-string )
uri-host = <host, see [RFC3986], Section 3.2.2> uri-host = <host, see [RFC3986], Section 3.2.2>
Appendix B. Differences between HTTP and MIME Appendix B. Differences between HTTP and MIME
HTTP/1.1 uses many of the constructs defined for the Internet Message HTTP/1.1 uses many of the constructs defined for the Internet Message
Format [RFC5322] and the Multipurpose Internet Mail Extensions (MIME) Format [RFC5322] and the Multipurpose Internet Mail Extensions (MIME)
[RFC2045] to allow a message body to be transmitted in an open [RFC2045] to allow a message body to be transmitted in an open
variety of representations and with extensible header fields. variety of representations and with extensible fields. However, RFC
However, RFC 2045 is focused only on email; applications of HTTP have 2045 is focused only on email; applications of HTTP have many
many characteristics that differ from email; hence, HTTP has features characteristics that differ from email; hence, HTTP has features that
that differ from MIME. These differences were carefully chosen to differ from MIME. These differences were carefully chosen to
optimize performance over binary connections, to allow greater optimize performance over binary connections, to allow greater
freedom in the use of new media types, to make date comparisons freedom in the use of new media types, to make date comparisons
easier, and to acknowledge the practice of some early HTTP servers easier, and to acknowledge the practice of some early HTTP servers
and clients. and clients.
This appendix describes specific areas where HTTP differs from MIME. This appendix describes specific areas where HTTP differs from MIME.
Proxies and gateways to and from strict MIME environments need to be Proxies and gateways to and from strict MIME environments need to be
aware of these differences and provide the appropriate conversions aware of these differences and provide the appropriate conversions
where necessary. where necessary.
B.1. MIME-Version B.1. MIME-Version
HTTP is not a MIME-compliant protocol. However, messages can include HTTP is not a MIME-compliant protocol. However, messages can include
a single MIME-Version header field to indicate what version of the a single MIME-Version header field to indicate what version of the
MIME protocol was used to construct the message. Use of the MIME protocol was used to construct the message. Use of the MIME-
MIME-Version header field indicates that the message is in full Version header field indicates that the message is in full
conformance with the MIME protocol (as defined in [RFC2045]). conformance with the MIME protocol (as defined in [RFC2045]).
Senders are responsible for ensuring full conformance (where Senders are responsible for ensuring full conformance (where
possible) when exporting HTTP messages to strict MIME environments. possible) when exporting HTTP messages to strict MIME environments.
B.2. Conversion to Canonical Form B.2. Conversion to Canonical Form
MIME requires that an Internet mail body part be converted to MIME requires that an Internet mail body part be converted to
canonical form prior to being transferred, as described in Section 4 canonical form prior to being transferred, as described in Section 4
of [RFC2049]. Section 3.1.1.3 of this document describes the forms of [RFC2049]. Section 7.4.3 of [Semantics] describes the forms
allowed for subtypes of the "text" media type when transmitted over allowed for subtypes of the "text" media type when transmitted over
HTTP. [RFC2046] requires that content with a type of "text" HTTP. [RFC2046] requires that content with a type of "text"
represent line breaks as CRLF and forbids the use of CR or LF outside represent line breaks as CRLF and forbids the use of CR or LF outside
of line break sequences. HTTP allows CRLF, bare CR, and bare LF to of line break sequences. HTTP allows CRLF, bare CR, and bare LF to
indicate a line break within text content. indicate a line break within text content.
A proxy or gateway from HTTP to a strict MIME environment ought to A proxy or gateway from HTTP to a strict MIME environment ought to
translate all line breaks within the text media types described in translate all line breaks within text media types to the RFC 2049
Section 3.1.1.3 of this document to the RFC 2049 canonical form of canonical form of CRLF. Note, however, this might be complicated by
CRLF. Note, however, this might be complicated by the presence of a the presence of a Content-Encoding and by the fact that HTTP allows
Content-Encoding and by the fact that HTTP allows the use of some the use of some charsets that do not use octets 13 and 10 to
charsets that do not use octets 13 and 10 to represent CR and LF, represent CR and LF, respectively.
respectively.
Conversion will break any cryptographic checksums applied to the Conversion will break any cryptographic checksums applied to the
original content unless the original content is already in canonical original content unless the original content is already in canonical
form. Therefore, the canonical form is recommended for any content form. Therefore, the canonical form is recommended for any content
that uses such checksums in HTTP. that uses such checksums in HTTP.
B.3. Conversion of Date Formats B.3. Conversion of Date Formats
HTTP/1.1 uses a restricted set of date formats (Section 7.1.1.1) to HTTP/1.1 uses a restricted set of date formats (Section 5.7.7 of
simplify the process of date comparison. Proxies and gateways from [Semantics]) to simplify the process of date comparison. Proxies and
other protocols ought to ensure that any Date header field present in gateways from other protocols ought to ensure that any Date header
a message conforms to one of the HTTP/1.1 formats and rewrite the field present in a message conforms to one of the HTTP/1.1 formats
date if necessary. and rewrite the date if necessary.
B.4. Conversion of Content-Encoding B.4. Conversion of Content-Encoding
MIME does not include any concept equivalent to HTTP/1.1's MIME does not include any concept equivalent to HTTP/1.1's Content-
Content-Encoding header field. Since this acts as a modifier on the Encoding header field. Since this acts as a modifier on the media
media type, proxies and gateways from HTTP to MIME-compliant type, proxies and gateways from HTTP to MIME-compliant protocols
protocols ought to either change the value of the Content-Type header ought to either change the value of the Content-Type header field or
field or decode the representation before forwarding the message. decode the representation before forwarding the message. (Some
(Some experimental applications of Content-Type for Internet mail experimental applications of Content-Type for Internet mail have used
have used a media-type parameter of ";conversions=<content-coding>" a media-type parameter of ";conversions=<content-coding>" to perform
to perform a function equivalent to Content-Encoding. However, this a function equivalent to Content-Encoding. However, this parameter
parameter is not part of the MIME standards). is not part of the MIME standards).
B.5. Conversion of Content-Transfer-Encoding B.5. Conversion of Content-Transfer-Encoding
HTTP does not use the Content-Transfer-Encoding field of MIME. HTTP does not use the Content-Transfer-Encoding field of MIME.
Proxies and gateways from MIME-compliant protocols to HTTP need to Proxies and gateways from MIME-compliant protocols to HTTP need to
remove any Content-Transfer-Encoding prior to delivering the response remove any Content-Transfer-Encoding prior to delivering the response
message to an HTTP client. message to an HTTP client.
Proxies and gateways from HTTP to MIME-compliant protocols are Proxies and gateways from HTTP to MIME-compliant protocols are
responsible for ensuring that the message is in the correct format responsible for ensuring that the message is in the correct format
skipping to change at line 2142 skipping to change at page 46, line 40
likelihood of safe transport over the destination protocol. likelihood of safe transport over the destination protocol.
B.6. MHTML and Line Length Limitations B.6. MHTML and Line Length Limitations
HTTP implementations that share code with MHTML [RFC2557] HTTP implementations that share code with MHTML [RFC2557]
implementations need to be aware of MIME line length limitations. implementations need to be aware of MIME line length limitations.
Since HTTP does not have this limitation, HTTP does not fold long Since HTTP does not have this limitation, HTTP does not fold long
lines. MHTML messages being transported by HTTP follow all lines. MHTML messages being transported by HTTP follow all
conventions of MHTML, including line length limitations and folding, conventions of MHTML, including line length limitations and folding,
canonicalization, etc., since HTTP transfers message-bodies as canonicalization, etc., since HTTP transfers message-bodies as
payload and, aside from the "multipart/byteranges" type (Appendix A payload and, aside from the "multipart/byteranges" type (Section 13.5
of [RFC7233]), does not interpret the content or any MIME header of [Semantics]), does not interpret the content or any MIME header
lines that might be contained therein. lines that might be contained therein.
Appendix C. HTTP Version History Appendix C. HTTP Version History
HTTP has been in use since 1990. The first version, later referred HTTP has been in use since 1990. The first version, later referred
to as HTTP/0.9, was a simple protocol for hypertext data transfer to as HTTP/0.9, was a simple protocol for hypertext data transfer
across the Internet, using only a single request method (GET) and no across the Internet, using only a single request method (GET) and no
metadata. HTTP/1.0, as defined by [RFC1945], added a range of metadata. HTTP/1.0, as defined by [RFC1945], added a range of
request methods and MIME-like messaging, allowing for metadata to be request methods and MIME-like messaging, allowing for metadata to be
transferred and modifiers placed on the request/response semantics. transferred and modifiers placed on the request/response semantics.
skipping to change at line 2191 skipping to change at page 47, line 40
properly encode the request-target. properly encode the request-target.
C.1. Changes from HTTP/1.0 C.1. Changes from HTTP/1.0
This section summarizes major differences between versions HTTP/1.0 This section summarizes major differences between versions HTTP/1.0
and HTTP/1.1. and HTTP/1.1.
C.1.1. Multihomed Web Servers C.1.1. Multihomed Web Servers
The requirements that clients and servers support the Host header The requirements that clients and servers support the Host header
field (Section 5.4), report an error if it is missing from an field (Section 6.1.2 of [Semantics]), report an error if it is
HTTP/1.1 request, and accept absolute URIs (Section 5.3) are among missing from an HTTP/1.1 request, and accept absolute URIs
the most important changes defined by HTTP/1.1. (Section 3.2) are among the most important changes defined by
HTTP/1.1.
Older HTTP/1.0 clients assumed a one-to-one relationship of IP Older HTTP/1.0 clients assumed a one-to-one relationship of IP
addresses and servers; there was no other established mechanism for addresses and servers; there was no other established mechanism for
distinguishing the intended server of a request than the IP address distinguishing the intended server of a request than the IP address
to which that request was directed. The Host header field was to which that request was directed. The Host header field was
introduced during the development of HTTP/1.1 and, though it was introduced during the development of HTTP/1.1 and, though it was
quickly implemented by most HTTP/1.0 browsers, additional quickly implemented by most HTTP/1.0 browsers, additional
requirements were placed on all HTTP/1.1 requests in order to ensure requirements were placed on all HTTP/1.1 requests in order to ensure
complete adoption. At the time of this writing, most HTTP-based complete adoption. At the time of this writing, most HTTP-based
services are dependent upon the Host header field for targeting services are dependent upon the Host header field for targeting
requests. requests.
C.1.2. Keep-Alive Connections C.1.2. Keep-Alive Connections
In HTTP/1.0, each connection is established by the client prior to In HTTP/1.0, each connection is established by the client prior to
the request and closed by the server after sending the response. the request and closed by the server after sending the response.
However, some implementations implement the explicitly negotiated However, some implementations implement the explicitly negotiated
("Keep-Alive") version of persistent connections described in Section ("Keep-Alive") version of persistent connections described in
19.7.1 of [RFC2068]. Section 19.7.1 of [RFC2068].
Some clients and servers might wish to be compatible with these Some clients and servers might wish to be compatible with these
previous approaches to persistent connections, by explicitly previous approaches to persistent connections, by explicitly
negotiating for them with a "Connection: keep-alive" request header negotiating for them with a "Connection: keep-alive" request header
field. However, some experimental implementations of HTTP/1.0 field. However, some experimental implementations of HTTP/1.0
persistent connections are faulty; for example, if an HTTP/1.0 proxy persistent connections are faulty; for example, if an HTTP/1.0 proxy
server doesn't understand Connection, it will erroneously forward server doesn't understand Connection, it will erroneously forward
that header field to the next inbound server, which would result in a that header field to the next inbound server, which would result in a
hung connection. hung connection.
One attempted solution was the introduction of a Proxy-Connection One attempted solution was the introduction of a Proxy-Connection
header field, targeted specifically at proxies. In practice, this header field, targeted specifically at proxies. In practice, this
was also unworkable, because proxies are often deployed in multiple was also unworkable, because proxies are often deployed in multiple
layers, bringing about the same problem discussed above. layers, bringing about the same problem discussed above.
As a result, clients are encouraged not to send the Proxy-Connection As a result, clients are encouraged not to send the Proxy-Connection
header field in any requests. header field in any requests.
Clients are also encouraged to consider the use of Connection: Clients are also encouraged to consider the use of Connection: keep-
keep-alive in requests carefully; while they can enable persistent alive in requests carefully; while they can enable persistent
connections with HTTP/1.0 servers, clients using them will need to connections with HTTP/1.0 servers, clients using them will need to
monitor the connection for "hung" requests (which indicate that the monitor the connection for "hung" requests (which indicate that the
client ought stop sending the header field), and this mechanism ought client ought stop sending the header field), and this mechanism ought
not be used by clients at all when a proxy is being used. not be used by clients at all when a proxy is being used.
C.1.3. Introduction of Transfer-Encoding C.1.3. Introduction of Transfer-Encoding
HTTP/1.1 introduces the Transfer-Encoding header field HTTP/1.1 introduces the Transfer-Encoding header field (Section 6.1).
(Section 3.3.1). Transfer codings need to be decoded prior to Transfer codings need to be decoded prior to forwarding an HTTP
forwarding an HTTP message over a MIME-compliant protocol. message over a MIME-compliant protocol.
C.2. Changes from RFC 2616 C.2. Changes from RFC 7230
[elided] Most of the sections introducing HTTP's design goals, history,
architecture, conformance criteria, protocol versioning, URIs,
message routing, and header fields have been moved to [Semantics].
This document has been reduced to just the messaging syntax and
connection management requirements specific to HTTP/1.1.
Prohibited generation of bare CRs outside of payload body.
(Section 2.2)
In the ABNF for chunked extensions, re-introduced (bad) whitespace
around ";" and "=". Whitespace was removed in [RFC7230], but that
change was found to break existing implementations (see [Err4667]).
(Section 7.1.1)
Trailer field semantics now transcend the specifics of chunked
encoding. The decoding algorithm for chunked (Section 7.1.3) has
been updated to encourage storage/forwarding of trailer fields
separately from the header section, to only allow merging into the
header section if the recipient knows the corresponding field
definition permits and defines how to merge, and otherwise to discard
the trailer fields instead of merging. The trailer part is now
called the trailer section to be more consistent with the header
section and more distinct from a body part. (Section 7.1.2)
Disallowed transfer coding parameters called "q" in order to avoid
conflicts with the use of ranks in the TE header field.
(Section 7.3)
Appendix D. Change Log Appendix D. Change Log
This section is to be removed before publishing as an RFC.
D.1. Between RFC7230 and draft 00 D.1. Between RFC7230 and draft 00
The changes were purely editorial:
o Change boilerplate and abstract to indicate the "draft" status,
and update references to ancestor specifications.
o Adjust historical notes.
o Update links to sibling specifications.
o Replace sections listing changes from RFC 2616 by new empty
sections referring to RFC 723x.
o Remove acknowledgements specific to RFC 723x.
o Move "Acknowledgements" to the very end and make them unnumbered.
D.2. Since draft-ietf-httpbis-messaging-00 D.2. Since draft-ietf-httpbis-messaging-00
The changes in this draft are editorial, with respect to HTTP as a
whole, to move all core HTTP semantics into [Semantics]:
o Moved introduction, architecture, conformance, and ABNF extensions
from RFC 7230 (Messaging) to semantics [Semantics].
o Moved discussion of MIME differences from RFC 7231 (Semantics) to
Appendix B since they mostly cover transforming 1.1 messages.
o Moved all extensibility tips, registration procedures, and
registry tables from the IANA considerations to normative
sections, reducing the IANA considerations to just instructions
that will be removed prior to publication as an RFC.
D.3. Since draft-ietf-httpbis-messaging-01 D.3. Since draft-ietf-httpbis-messaging-01
o Cite RFC 8126 instead of RFC 5226 (<https://github.com/httpwg/
http-core/issues/75>)
o Resolved erratum 4779, no change needed here
(<https://github.com/httpwg/http-core/issues/87>,
<https://www.rfc-editor.org/errata/eid4779>)
o In Section 7, fixed prose claiming transfer parameters allow bare
names (<https://github.com/httpwg/http-core/issues/88>,
<https://www.rfc-editor.org/errata/eid4839>)
o Resolved erratum 4225, no change needed here
(<https://github.com/httpwg/http-core/issues/90>,
<https://www.rfc-editor.org/errata/eid4225>)
o Replace "response code" with "response status code"
(<https://github.com/httpwg/http-core/issues/94>,
<https://www.rfc-editor.org/errata/eid4050>)
o In Section 9.3, clarify statement about HTTP/1.0 keep-alive
(<https://github.com/httpwg/http-core/issues/96>,
<https://www.rfc-editor.org/errata/eid4205>)
o In Section 7.1.1, re-introduce (bad) whitespace around ";" and "="
(<https://github.com/httpwg/http-core/issues/101>,
<https://www.rfc-editor.org/errata/eid4667>, <https://www.rfc-
editor.org/errata/eid4825>)
o In Section 7.3, state that transfer codings should not use
parameters named "q" (<https://github.com/httpwg/http-core/
issues/15>, <https://www.rfc-editor.org/errata/eid4683>)
o In Section 7, mark coding name "trailers" as reserved in the IANA
registry (<https://github.com/httpwg/http-core/issues/108>)
D.4. Since draft-ietf-httpbis-messaging-02 D.4. Since draft-ietf-httpbis-messaging-02
o In Section 4, explain why the reason phrase should be ignored by
clients (<https://github.com/httpwg/http-core/issues/60>).
o Add Section 9.2 to explain how request/response correlation is
performed (<https://github.com/httpwg/http-core/issues/145>)
D.5. Since draft-ietf-httpbis-messaging-03 D.5. Since draft-ietf-httpbis-messaging-03
o In Section 9.2, caution against treating data on a connection as
part of a not-yet-issued request (<https://github.com/httpwg/http-
core/issues/26>)
o In Section 7, remove the predefined codings from the ABNF and make
it generic instead (<https://github.com/httpwg/http-core/
issues/66>)
o Use RFC 7405 ABNF notation for case-sensitive string constants
(<https://github.com/httpwg/http-core/issues/133>)
D.6. Since draft-ietf-httpbis-messaging-04 D.6. Since draft-ietf-httpbis-messaging-04
o In Section 6.6 of [Semantics], clarify that protocol-name is to be
matched case-insensitively (<https://github.com/httpwg/http-core/
issues/8>)
o In Section 5.2, add leading optional whitespace to obs-fold ABNF
(<https://github.com/httpwg/http-core/issues/19>,
<https://www.rfc-editor.org/errata/eid4189>)
o In Section 4, add clarifications about empty reason phrases
(<https://github.com/httpwg/http-core/issues/197>)
o Move discussion of retries from Section 9.3.1 into [Semantics]
(<https://github.com/httpwg/http-core/issues/230>)
D.7. Since draft-ietf-httpbis-messaging-05 D.7. Since draft-ietf-httpbis-messaging-05
o In Section 7.1.2, the trailer part has been renamed the trailer
section (for consistency with the header section) and trailers are
no longer merged as header fields by default, but rather can be
discarded, kept separate from header fields, or merged with header
fields only if understood and defined as being mergeable
(<https://github.com/httpwg/http-core/issues/16>)
o In Section 2.1 and related Sections, move the trailing CRLF from
the line grammars into the message format
(<https://github.com/httpwg/http-core/issues/62>)
o Moved Section 2.3 down (<https://github.com/httpwg/http-core/
issues/68>)
o In Section 6.6 of [Semantics], use 'websocket' instead of
'HTTP/2.0' in examples (<https://github.com/httpwg/http-core/
issues/112>)
o Move version non-specific text from Section 6 into semantics as
"payload body" (<https://github.com/httpwg/http-core/issues/159>)
o In Section 9.8, add text from RFC 2818
(<https://github.com/httpwg/http-core/issues/236>)
D.8. Since draft-ietf-httpbis-messaging-06 D.8. Since draft-ietf-httpbis-messaging-06
o In Section 12.4, update the APLN protocol id for HTTP/1.1
(<https://github.com/httpwg/http-core/issues/49>)
o In Section 5, align with updates to field terminology in semantics
(<https://github.com/httpwg/http-core/issues/111>)
o In Section 6.4.1 of [Semantics], clarify that new connection
options indeed need to be registered (<https://github.com/httpwg/
http-core/issues/285>)
o In Section 1.1, reference RFC 8174 as well
(<https://github.com/httpwg/http-core/issues/303>)
D.9. Since draft-ietf-httpbis-messaging-07 D.9. Since draft-ietf-httpbis-messaging-07
o Move TE: trailers into [Semantics] (<https://github.com/httpwg/
http-core/issues/18>)
o In Section 6.3, adjust requirements for handling multiple content-
length values (<https://github.com/httpwg/http-core/issues/59>)
o Throughout, replace "effective request URI" with "target URI"
(<https://github.com/httpwg/http-core/issues/259>)
o In Section 6.1, don't claim Transfer-Encoding is supported by
HTTP/2 or later (<https://github.com/httpwg/http-core/issues/297>)
D.10. Since draft-ietf-httpbis-messaging-08 D.10. Since draft-ietf-httpbis-messaging-08
o In Section 2.2, disallow bare CRs (<https://github.com/httpwg/
http-core/issues/31>)
o Appendix A now uses the sender variant of the "#" list expansion
(<https://github.com/httpwg/http-core/issues/192>)
o In Section 5, adjust IANA "Close" entry for new registry format
(<https://github.com/httpwg/http-core/issues/273>)
D.11. Since draft-ietf-httpbis-messaging-09 D.11. Since draft-ietf-httpbis-messaging-09
10. Acknowledgments o Switch to xml2rfc v3 mode for draft generation
(<https://github.com/httpwg/http-core/issues/394>)
This edition of HTTP/1.1 builds on the many contributions that went D.12. Since draft-ietf-httpbis-messaging-10
into RFC 1945, RFC 2068, RFC 2145, and RFC 2616, including
substantial contributions made by the previous authors, editors, and
Working Group Chairs: Tim Berners-Lee, Ari Luotonen, Roy T. Fielding,
Henrik Frystyk Nielsen, Jim Gettys, Jeffrey C. Mogul, Larry Masinter,
and Paul J. Leach. Mark Nottingham oversaw this effort as Working
Group Chair.
Since 1999, the following contributors have helped improve the HTTP o In Section 6.3, note that TCP half-close does not delimit a
specification by reporting bugs, asking smart questions, drafting or request; talk about corresponding server-side behaviour in
reviewing text, and evaluating open issues: Section 9.6 (<https://github.com/httpwg/http-core/issues/22>)
Adam Barth, Adam Roach, Addison Phillips, Adrian Chadd, Adrian Cole, o Moved requirements specific to HTTP/1.1 from [Semantics] into
Adrien W. de Croy, Alan Ford, Alan Ruttenberg, Albert Lunde, Alek Section 3.2 (<https://github.com/httpwg/http-core/issues/182>)
Storm, Alex Rousskov, Alexandre Morgaut, Alexey Melnikov, Alisha
Smith, Amichai Rothman, Amit Klein, Amos Jeffries, Andreas Maier,
Andreas Petersson, Andrei Popov, Anil Sharma, Anne van Kesteren,
Anthony Bryan, Asbjorn Ulsberg, Ashok Kumar, Balachander
Krishnamurthy, Barry Leiba, Ben Laurie, Benjamin Carlyle, Benjamin
Niven-Jenkins, Benoit Claise, Bil Corry, Bill Burke, Bjoern
Hoehrmann, Bob Scheifler, Boris Zbarsky, Brett Slatkin, Brian Kell,
Brian McBarron, Brian Pane, Brian Raymor, Brian Smith, Bruce Perens,
Bryce Nesbitt, Cameron Heavon-Jones, Carl Kugler, Carsten Bormann,
Charles Fry, Chris Burdess, Chris Newman, Christian Huitema, Cyrus
Daboo, Dale Robert Anderson, Dan Wing, Dan Winship, Daniel Stenberg,
Darrel Miller, Dave Cridland, Dave Crocker, Dave Kristol, Dave
Thaler, David Booth, David Singer, David W. Morris, Diwakar Shetty,
Dmitry Kurochkin, Drummond Reed, Duane Wessels, Edward Lee, Eitan
Adler, Eliot Lear, Emile Stephan, Eran Hammer-Lahav, Eric D.
Williams, Eric J. Bowman, Eric Lawrence, Eric Rescorla, Erik
Aronesty, EungJun Yi, Evan Prodromou, Felix Geisendoerfer, Florian
Weimer, Frank Ellermann, Fred Akalin, Fred Bohle, Frederic Kayser,
Gabor Molnar, Gabriel Montenegro, Geoffrey Sneddon, Gervase Markham,
Gili Tzabari, Grahame Grieve, Greg Slepak, Greg Wilkins, Grzegorz
Calkowski, Harald Tveit Alvestrand, Harry Halpin, Helge Hess, Henrik
Nordstrom, Henry S. Thompson, Henry Story, Herbert van de Sompel,
Herve Ruellan, Howard Melman, Hugo Haas, Ian Fette, Ian Hickson, Ido
Safruti, Ilari Liusvaara, Ilya Grigorik, Ingo Struck, J. Ross Nicoll,
James Cloos, James H. Manger, James Lacey, James M. Snell, Jamie
Lokier, Jan Algermissen, Jari Arkko, Jeff Hodges (who came up with
the term 'effective Request-URI'), Jeff Pinner, Jeff Walden, Jim
Luther, Jitu Padhye, Joe D. Williams, Joe Gregorio, Joe Orton, Joel
Jaeggli, John C. Klensin, John C. Mallery, John Cowan, John Kemp,
John Panzer, John Schneider, John Stracke, John Sullivan, Jonas
Sicking, Jonathan A. Rees, Jonathan Billington, Jonathan Moore,
Jonathan Silvera, Jordi Ros, Joris Dobbelsteen, Josh Cohen, Julien
Pierre, Jungshik Shin, Justin Chapweske, Justin Erenkrantz, Justin
James, Kalvinder Singh, Karl Dubost, Kathleen Moriarty, Keith
Hoffman, Keith Moore, Ken Murchison, Koen Holtman, Konstantin
Voronkov, Kris Zyp, Leif Hedstrom, Lionel Morand, Lisa Dusseault,
Maciej Stachowiak, Manu Sporny, Marc Schneider, Marc Slemko, Mark
Baker, Mark Pauley, Mark Watson, Markus Isomaki, Markus Lanthaler,
Martin J. Duerst, Martin Musatov, Martin Nilsson, Martin Thomson,
Matt Lynch, Matthew Cox, Matthew Kerwin, Max Clark, Menachem Dodge,
Meral Shirazipour, Michael Burrows, Michael Hausenblas, Michael
Scharf, Michael Sweet, Michael Tuexen, Michael Welzl, Mike Amundsen,
Mike Belshe, Mike Bishop, Mike Kelly, Mike Schinkel, Miles Sabin,
Murray S. Kucherawy, Mykyta Yevstifeyev, Nathan Rixham, Nicholas
Shanks, Nico Williams, Nicolas Alvarez, Nicolas Mailhot, Noah Slater,
Osama Mazahir, Pablo Castro, Pat Hayes, Patrick R. McManus, Paul E.
Jones, Paul Hoffman, Paul Marquess, Pete Resnick, Peter Lepeska,
Peter Occil, Peter Saint-Andre, Peter Watkins, Phil Archer, Phil
Hunt, Philippe Mougin, Phillip Hallam-Baker, Piotr Dobrogost, Poul-
Henning Kamp, Preethi Natarajan, Rajeev Bector, Ray Polk, Reto
Bachmann-Gmuer, Richard Barnes, Richard Cyganiak, Rob Trace, Robby
Simpson, Robert Brewer, Robert Collins, Robert Mattson, Robert
O'Callahan, Robert Olofsson, Robert Sayre, Robert Siemer, Robert de
Wilde, Roberto Javier Godoy, Roberto Peon, Roland Zink, Ronny
Widjaja, Ryan Hamilton, S. Mike Dierken, Salvatore Loreto, Sam
Johnston, Sam Pullara, Sam Ruby, Saurabh Kulkarni, Scott Lawrence
(who maintained the original issues list), Sean B. Palmer, Sean
Turner, Sebastien Barnoud, Shane McCarron, Shigeki Ohtsu, Simon
Yarde, Stefan Eissing, Stefan Tilkov, Stefanos Harhalakis, Stephane
Bortzmeyer, Stephen Farrell, Stephen Kent, Stephen Ludin, Stuart
Williams, Subbu Allamaraju, Subramanian Moonesamy, Susan Hares,
Sylvain Hellegouarch, Tapan Divekar, Tatsuhiro Tsujikawa, Tatsuya
Hayashi, Ted Hardie, Ted Lemon, Thomas Broyer, Thomas Fossati, Thomas
Maslen, Thomas Nadeau, Thomas Nordin, Thomas Roessler, Tim Bray, Tim
Morgan, Tim Olsen, Tom Zhou, Travis Snoozy, Tyler Close, Vincent
Murphy, Wenbo Zhu, Werner Baumann, Wilbur Streett, Wilfredo Sanchez
Vega, William A. Rowe Jr., William Chan, Willy Tarreau, Xiaoshu Wang,
Yaron Goland, Yngve Nysaeter Pettersen, Yoav Nir, Yogesh Bang,
Yuchung Cheng, Yutaka Oiwa, Yves Lafon (long-time member of the
editor team), Zed A. Shaw, and Zhong Yu.
See Section 16 of [RFC2616] for additional acknowledgements from o In Section 6.1 (Transfer-Encoding), adjust ABNF to allow empty
prior revisions. lists (<https://github.com/httpwg/http-core/issues/210>)
o In Section 9.7, add text from RFC 2818
(<https://github.com/httpwg/http-core/issues/236>)
o Moved definitions of "TE" and "Upgrade" into [Semantics]
(<https://github.com/httpwg/http-core/issues/392>)
o Moved definition of "Connection" into [Semantics]
(<https://github.com/httpwg/http-core/issues/407>)
D.13. Since draft-ietf-httpbis-messaging-11
o Move IANA Upgrade Token Registry instructions to [Semantics]
(<https://github.com/httpwg/http-core/issues/450>)
Acknowledgments
See Appendix "Acknowledgments" of [Semantics].
Authors' Addresses Authors' Addresses
Roy T. Fielding (editor) Roy T. Fielding (editor)
Adobe Systems Incorporated Adobe
345 Park Ave 345 Park Ave
San Jose, CA 95110 San Jose, CA 95110
USA United States of America
EMail: fielding@gbiv.com Email: fielding@gbiv.com
URI: http://roy.gbiv.com/ URI: https://roy.gbiv.com/
Julian F. Reschke (editor) Mark Nottingham (editor)
Fastly
Prahran VIC
Australia
Email: mnot@mnot.net
URI: https://www.mnot.net/
Julian Reschke (editor)
greenbytes GmbH greenbytes GmbH
Hafenweg 16 Hafenweg 16
Muenster, NW 48155 48155 M√ľnster
Germany Germany
EMail: julian.reschke@greenbytes.de Email: julian.reschke@greenbytes.de
URI: http://greenbytes.de/tech/webdav/ URI: https://greenbytes.de/tech/webdav/
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