/docs/rfc3875.txt
Plain Text | 2019 lines | 1392 code | 627 blank | 0 comment | 0 complexity | bcc195229bb970719dbfd6dc4ef06049 MD5 | raw file
Possible License(s): GPL-3.0
- Network Working Group D. Robinson
- Request for Comments: 3875 K. Coar
- Category: Informational The Apache Software Foundation
- October 2004
- The Common Gateway Interface (CGI) Version 1.1
- Status of this Memo
- This memo provides information for the Internet community. It does
- not specify an Internet standard of any kind. Distribution of this
- memo is unlimited.
- Copyright Notice
- Copyright (C) The Internet Society (2004).
- IESG Note
- This document is not a candidate for any level of Internet Standard.
- The IETF disclaims any knowledge of the fitness of this document for
- any purpose, and in particular notes that it has not had IETF review
- for such things as security, congestion control or inappropriate
- interaction with deployed protocols. The RFC Editor has chosen to
- publish this document at its discretion. Readers of this document
- should exercise caution in evaluating its value for implementation
- and deployment.
- Abstract
- The Common Gateway Interface (CGI) is a simple interface for running
- external programs, software or gateways under an information server
- in a platform-independent manner. Currently, the supported
- information servers are HTTP servers.
- The interface has been in use by the World-Wide Web (WWW) since 1993.
- This specification defines the 'current practice' parameters of the
- 'CGI/1.1' interface developed and documented at the U.S. National
- Centre for Supercomputing Applications. This document also defines
- the use of the CGI/1.1 interface on UNIX(R) and other, similar
- systems.
- Robinson & Coar Informational [Page 1]
- RFC 3875 CGI Version 1.1 October 2004
- Table of Contents
- 1. Introduction. . . . . . . . . . . . . . . . . . . . . . . . . 4
- 1.1. Purpose . . . . . . . . . . . . . . . . . . . . . . . . 4
- 1.2. Requirements . . . . . . . . . . . . . . . . . . . . . . 4
- 1.3. Specifications . . . . . . . . . . . . . . . . . . . . . 4
- 1.4. Terminology . . . . . . . . . . . . . . . . . . . . . . 5
- 2. Notational Conventions and Generic Grammar. . . . . . . . . . 5
- 2.1. Augmented BNF . . . . . . . . . . . . . . . . . . . . . 5
- 2.2. Basic Rules . . . . . . . . . . . . . . . . . . . . . . 6
- 2.3. URL Encoding . . . . . . . . . . . . . . . . . . . . . . 7
- 3. Invoking the Script . . . . . . . . . . . . . . . . . . . . . 8
- 3.1. Server Responsibilities . . . . . . . . . . . . . . . . 8
- 3.2. Script Selection . . . . . . . . . . . . . . . . . . . . 9
- 3.3. The Script-URI . . . . . . . . . . . . . . . . . . . . . 9
- 3.4. Execution . . . . . . . . . . . . . . . . . . . . . . . 10
- 4. The CGI Request . . . . . . . . . . . . . . . . . . . . . . . 10
- 4.1. Request Meta-Variables . . . . . . . . . . . . . . . . . 10
- 4.1.1. AUTH_TYPE. . . . . . . . . . . . . . . . . . . . 11
- 4.1.2. CONTENT_LENGTH . . . . . . . . . . . . . . . . . 12
- 4.1.3. CONTENT_TYPE . . . . . . . . . . . . . . . . . . 12
- 4.1.4. GATEWAY_INTERFACE. . . . . . . . . . . . . . . . 13
- 4.1.5. PATH_INFO. . . . . . . . . . . . . . . . . . . . 13
- 4.1.6. PATH_TRANSLATED. . . . . . . . . . . . . . . . . 14
- 4.1.7. QUERY_STRING . . . . . . . . . . . . . . . . . . 15
- 4.1.8. REMOTE_ADDR. . . . . . . . . . . . . . . . . . . 15
- 4.1.9. REMOTE_HOST. . . . . . . . . . . . . . . . . . . 16
- 4.1.10. REMOTE_IDENT . . . . . . . . . . . . . . . . . . 16
- 4.1.11. REMOTE_USER. . . . . . . . . . . . . . . . . . . 16
- 4.1.12. REQUEST_METHOD . . . . . . . . . . . . . . . . . 17
- 4.1.13. SCRIPT_NAME. . . . . . . . . . . . . . . . . . . 17
- 4.1.14. SERVER_NAME. . . . . . . . . . . . . . . . . . . 17
- 4.1.15. SERVER_PORT. . . . . . . . . . . . . . . . . . . 18
- 4.1.16. SERVER_PROTOCOL. . . . . . . . . . . . . . . . . 18
- 4.1.17. SERVER_SOFTWARE. . . . . . . . . . . . . . . . . 19
- 4.1.18. Protocol-Specific Meta-Variables . . . . . . . . 19
- 4.2. Request Message-Body . . . . . . . . . . . . . . . . . . 20
- 4.3. Request Methods . . . . . . . . . . . . . . . . . . . . 20
- 4.3.1. GET. . . . . . . . . . . . . . . . . . . . . . . 20
- 4.3.2. POST . . . . . . . . . . . . . . . . . . . . . . 21
- 4.3.3. HEAD . . . . . . . . . . . . . . . . . . . . . . 21
- 4.3.4. Protocol-Specific Methods. . . . . . . . . . . . 21
- 4.4. The Script Command Line. . . . . . . . . . . . . . . . . 21
- Robinson & Coar Informational [Page 2]
- RFC 3875 CGI Version 1.1 October 2004
- 5. NPH Scripts . . . . . . . . . . . . . . . . . . . . . . . . . 22
- 5.1. Identification . . . . . . . . . . . . . . . . . . . . . 22
- 5.2. NPH Response . . . . . . . . . . . . . . . . . . . . . . 22
- 6. CGI Response. . . . . . . . . . . . . . . . . . . . . . . . . 23
- 6.1. Response Handling. . . . . . . . . . . . . . . . . . . . 23
- 6.2. Response Types . . . . . . . . . . . . . . . . . . . . . 23
- 6.2.1. Document Response. . . . . . . . . . . . . . . . 23
- 6.2.2. Local Redirect Response. . . . . . . . . . . . . 24
- 6.2.3. Client Redirect Response . . . . . . . . . . . . 24
- 6.2.4. Client Redirect Response with Document . . . . . 24
- 6.3. Response Header Fields . . . . . . . . . . . . . . . . . 25
- 6.3.1. Content-Type . . . . . . . . . . . . . . . . . . 25
- 6.3.2. Location . . . . . . . . . . . . . . . . . . . . 26
- 6.3.3. Status . . . . . . . . . . . . . . . . . . . . . 26
- 6.3.4. Protocol-Specific Header Fields. . . . . . . . . 27
- 6.3.5. Extension Header Fields. . . . . . . . . . . . . 27
- 6.4. Response Message-Body. . . . . . . . . . . . . . . . . . 28
- 7. System Specifications . . . . . . . . . . . . . . . . . . . . 28
- 7.1. AmigaDOS . . . . . . . . . . . . . . . . . . . . . . . . 28
- 7.2. UNIX . . . . . . . . . . . . . . . . . . . . . . . . . . 28
- 7.3. EBCDIC/POSIX . . . . . . . . . . . . . . . . . . . . . . 29
- 8. Implementation. . . . . . . . . . . . . . . . . . . . . . . . 29
- 8.1. Recommendations for Servers. . . . . . . . . . . . . . . 29
- 8.2. Recommendations for Scripts. . . . . . . . . . . . . . . 30
- 9. Security Considerations . . . . . . . . . . . . . . . . . . . 30
- 9.1. Safe Methods . . . . . . . . . . . . . . . . . . . . . . 30
- 9.2. Header Fields Containing Sensitive Information . . . . . 31
- 9.3. Data Privacy . . . . . . . . . . . . . . . . . . . . . . 31
- 9.4. Information Security Model . . . . . . . . . . . . . . . 31
- 9.5. Script Interference with the Server. . . . . . . . . . . 31
- 9.6. Data Length and Buffering Considerations . . . . . . . . 32
- 9.7. Stateless Processing . . . . . . . . . . . . . . . . . . 32
- 9.8. Relative Paths . . . . . . . . . . . . . . . . . . . . . 33
- 9.9. Non-parsed Header Output . . . . . . . . . . . . . . . . 33
- 10. Acknowledgements. . . . . . . . . . . . . . . . . . . . . . . 33
- 11. References. . . . . . . . . . . . . . . . . . . . . . . . . . 33
- 11.1. Normative References. . . . . . . . . . . . . . . . . . 33
- 11.2. Informative References. . . . . . . . . . . . . . . . . 34
- 12. Authors' Addresses. . . . . . . . . . . . . . . . . . . . . . 35
- 13. Full Copyright Statement. . . . . . . . . . . . . . . . . . . 36
- Robinson & Coar Informational [Page 3]
- RFC 3875 CGI Version 1.1 October 2004
- 1. Introduction
- 1.1. Purpose
- The Common Gateway Interface (CGI) [22] allows an HTTP [1], [4]
- server and a CGI script to share responsibility for responding to
- client requests. The client request comprises a Uniform Resource
- Identifier (URI) [11], a request method and various ancillary
- information about the request provided by the transport protocol.
- The CGI defines the abstract parameters, known as meta-variables,
- which describe a client's request. Together with a concrete
- programmer interface this specifies a platform-independent interface
- between the script and the HTTP server.
- The server is responsible for managing connection, data transfer,
- transport and network issues related to the client request, whereas
- the CGI script handles the application issues, such as data access
- and document processing.
- 1.2. Requirements
- The key words 'MUST', 'MUST NOT', 'REQUIRED', 'SHALL', 'SHALL NOT',
- 'SHOULD', 'SHOULD NOT', 'RECOMMENDED', 'MAY' and 'OPTIONAL' in this
- document are to be interpreted as described in BCP 14, RFC 2119 [3].
- An implementation is not compliant if it fails to satisfy one or more
- of the 'must' requirements for the protocols it implements. An
- implementation that satisfies all of the 'must' and all of the
- 'should' requirements for its features is said to be 'unconditionally
- compliant'; one that satisfies all of the 'must' requirements but not
- all of the 'should' requirements for its features is said to be
- 'conditionally compliant'.
- 1.3. Specifications
- Not all of the functions and features of the CGI are defined in the
- main part of this specification. The following phrases are used to
- describe the features that are not specified:
- 'system-defined'
- The feature may differ between systems, but must be the same for
- different implementations using the same system. A system will
- usually identify a class of operating systems. Some systems are
- defined in section 7 of this document. New systems may be defined
- by new specifications without revision of this document.
- Robinson & Coar Informational [Page 4]
- RFC 3875 CGI Version 1.1 October 2004
- 'implementation-defined'
- The behaviour of the feature may vary from implementation to
- implementation; a particular implementation must document its
- behaviour.
- 1.4. Terminology
- This specification uses many terms defined in the HTTP/1.1
- specification [4]; however, the following terms are used here in a
- sense which may not accord with their definitions in that document,
- or with their common meaning.
- 'meta-variable'
- A named parameter which carries information from the server to the
- script. It is not necessarily a variable in the operating
- system's environment, although that is the most common
- implementation.
- 'script'
- The software that is invoked by the server according to this
- interface. It need not be a standalone program, but could be a
- dynamically-loaded or shared library, or even a subroutine in the
- server. It might be a set of statements interpreted at run-time,
- as the term 'script' is frequently understood, but that is not a
- requirement and within the context of this specification the term
- has the broader definition stated.
- 'server'
- The application program that invokes the script in order to
- service requests from the client.
- 2. Notational Conventions and Generic Grammar
- 2.1. Augmented BNF
- All of the mechanisms specified in this document are described in
- both prose and an augmented Backus-Naur Form (BNF) similar to that
- used by RFC 822 [13]. Unless stated otherwise, the elements are
- case-sensitive. This augmented BNF contains the following
- constructs:
- name = definition
- The name of a rule and its definition are separated by the equals
- character ('='). Whitespace is only significant in that
- continuation lines of a definition are indented.
- Robinson & Coar Informational [Page 5]
- RFC 3875 CGI Version 1.1 October 2004
- "literal"
- Double quotation marks (") surround literal text, except for a
- literal quotation mark, which is surrounded by angle-brackets ('<'
- and '>').
- rule1 | rule2
- Alternative rules are separated by a vertical bar ('|').
- (rule1 rule2 rule3)
- Elements enclosed in parentheses are treated as a single element.
- *rule
- A rule preceded by an asterisk ('*') may have zero or more
- occurrences. The full form is 'n*m rule' indicating at least n
- and at most m occurrences of the rule. n and m are optional
- decimal values with default values of 0 and infinity respectively.
- [rule]
- An element enclosed in square brackets ('[' and ']') is optional,
- and is equivalent to '*1 rule'.
- N rule
- A rule preceded by a decimal number represents exactly N
- occurrences of the rule. It is equivalent to 'N*N rule'.
- 2.2. Basic Rules
- This specification uses a BNF-like grammar defined in terms of
- characters. Unlike many specifications which define the bytes
- allowed by a protocol, here each literal in the grammar corresponds
- to the character it represents. How these characters are represented
- in terms of bits and bytes within a system are either system-defined
- or specified in the particular context. The single exception is the
- rule 'OCTET', defined below.
- The following rules are used throughout this specification to
- describe basic parsing constructs.
- alpha = lowalpha | hialpha
- lowalpha = "a" | "b" | "c" | "d" | "e" | "f" | "g" | "h" |
- "i" | "j" | "k" | "l" | "m" | "n" | "o" | "p" |
- "q" | "r" | "s" | "t" | "u" | "v" | "w" | "x" |
- "y" | "z"
- hialpha = "A" | "B" | "C" | "D" | "E" | "F" | "G" | "H" |
- "I" | "J" | "K" | "L" | "M" | "N" | "O" | "P" |
- "Q" | "R" | "S" | "T" | "U" | "V" | "W" | "X" |
- "Y" | "Z"
- Robinson & Coar Informational [Page 6]
- RFC 3875 CGI Version 1.1 October 2004
- digit = "0" | "1" | "2" | "3" | "4" | "5" | "6" | "7" |
- "8" | "9"
- alphanum = alpha | digit
- OCTET = <any 8-bit byte>
- CHAR = alpha | digit | separator | "!" | "#" | "$" |
- "%" | "&" | "'" | "*" | "+" | "-" | "." | "`" |
- "^" | "_" | "{" | "|" | "}" | "~" | CTL
- CTL = <any control character>
- SP = <space character>
- HT = <horizontal tab character>
- NL = <newline>
- LWSP = SP | HT | NL
- separator = "(" | ")" | "<" | ">" | "@" | "," | ";" | ":" |
- "\" | <"> | "/" | "[" | "]" | "?" | "=" | "{" |
- "}" | SP | HT
- token = 1*<any CHAR except CTLs or separators>
- quoted-string = <"> *qdtext <">
- qdtext = <any CHAR except <"> and CTLs but including LWSP>
- TEXT = <any printable character>
- Note that newline (NL) need not be a single control character, but
- can be a sequence of control characters. A system MAY define TEXT to
- be a larger set of characters than <any CHAR excluding CTLs but
- including LWSP>.
- 2.3. URL Encoding
- Some variables and constructs used here are described as being
- 'URL-encoded'. This encoding is described in section 2 of RFC 2396
- [2]. In a URL-encoded string an escape sequence consists of a
- percent character ("%") followed by two hexadecimal digits, where the
- two hexadecimal digits form an octet. An escape sequence represents
- the graphic character that has the octet as its code within the
- US-ASCII [9] coded character set, if it exists. Currently there is
- no provision within the URI syntax to identify which character set
- non-ASCII codes represent, so CGI handles this issue on an ad-hoc
- basis.
- Note that some unsafe (reserved) characters may have different
- semantics when encoded. The definition of which characters are
- unsafe depends on the context; see section 2 of RFC 2396 [2], updated
- by RFC 2732 [7], for an authoritative treatment. These reserved
- characters are generally used to provide syntactic structure to the
- character string, for example as field separators. In all cases, the
- string is first processed with regard to any reserved characters
- present, and then the resulting data can be URL-decoded by replacing
- "%" escape sequences by their character values.
- Robinson & Coar Informational [Page 7]
- RFC 3875 CGI Version 1.1 October 2004
- To encode a character string, all reserved and forbidden characters
- are replaced by the corresponding "%" escape sequences. The string
- can then be used in assembling a URI. The reserved characters will
- vary from context to context, but will always be drawn from this set:
- reserved = ";" | "/" | "?" | ":" | "@" | "&" | "=" | "+" | "$" |
- "," | "[" | "]"
- The last two characters were added by RFC 2732 [7]. In any
- particular context, a sub-set of these characters will be reserved;
- the other characters from this set MUST NOT be encoded when a string
- is URL-encoded in that context. Other basic rules used to describe
- URI syntax are:
- hex = digit | "A" | "B" | "C" | "D" | "E" | "F" | "a" | "b"
- | "c" | "d" | "e" | "f"
- escaped = "%" hex hex
- unreserved = alpha | digit | mark
- mark = "-" | "_" | "." | "!" | "~" | "*" | "'" | "(" | ")"
- 3. Invoking the Script
- 3.1. Server Responsibilities
- The server acts as an application gateway. It receives the request
- from the client, selects a CGI script to handle the request, converts
- the client request to a CGI request, executes the script and converts
- the CGI response into a response for the client. When processing the
- client request, it is responsible for implementing any protocol or
- transport level authentication and security. The server MAY also
- function in a 'non-transparent' manner, modifying the request or
- response in order to provide some additional service, such as media
- type transformation or protocol reduction.
- The server MUST perform translations and protocol conversions on the
- client request data required by this specification. Furthermore, the
- server retains its responsibility to the client to conform to the
- relevant network protocol even if the CGI script fails to conform to
- this specification.
- If the server is applying authentication to the request, then it MUST
- NOT execute the script unless the request passes all defined access
- controls.
- Robinson & Coar Informational [Page 8]
- RFC 3875 CGI Version 1.1 October 2004
- 3.2. Script Selection
- The server determines which CGI is script to be executed based on a
- generic-form URI supplied by the client. This URI includes a
- hierarchical path with components separated by "/". For any
- particular request, the server will identify all or a leading part of
- this path with an individual script, thus placing the script at a
- particular point in the path hierarchy. The remainder of the path,
- if any, is a resource or sub-resource identifier to be interpreted by
- the script.
- Information about this split of the path is available to the script
- in the meta-variables, described below. Support for non-hierarchical
- URI schemes is outside the scope of this specification.
- 3.3. The Script-URI
- The mapping from client request URI to choice of script is defined by
- the particular server implementation and its configuration. The
- server may allow the script to be identified with a set of several
- different URI path hierarchies, and therefore is permitted to replace
- the URI by other members of this set during processing and generation
- of the meta-variables. The server
- 1. MAY preserve the URI in the particular client request; or
- 2. it MAY select a canonical URI from the set of possible values
- for each script; or
- 3. it can implement any other selection of URI from the set.
- From the meta-variables thus generated, a URI, the 'Script-URI', can
- be constructed. This MUST have the property that if the client had
- accessed this URI instead, then the script would have been executed
- with the same values for the SCRIPT_NAME, PATH_INFO and QUERY_STRING
- meta-variables. The Script-URI has the structure of a generic URI as
- defined in section 3 of RFC 2396 [2], with the exception that object
- parameters and fragment identifiers are not permitted. The various
- components of the Script-URI are defined by some of the
- meta-variables (see below);
- script-URI = <scheme> "://" <server-name> ":" <server-port>
- <script-path> <extra-path> "?" <query-string>
- where <scheme> is found from SERVER_PROTOCOL, <server-name>,
- <server-port> and <query-string> are the values of the respective
- meta-variables. The SCRIPT_NAME and PATH_INFO values, URL-encoded
- with ";", "=" and "?" reserved, give <script-path> and <extra-path>.
- Robinson & Coar Informational [Page 9]
- RFC 3875 CGI Version 1.1 October 2004
- See section 4.1.5 for more information about the PATH_INFO
- meta-variable.
- The scheme and the protocol are not identical as the scheme
- identifies the access method in addition to the application protocol.
- For example, a resource accessed using Transport Layer Security (TLS)
- [14] would have a request URI with a scheme of https when using the
- HTTP protocol [19]. CGI/1.1 provides no generic means for the script
- to reconstruct this, and therefore the Script-URI as defined includes
- the base protocol used. However, a script MAY make use of
- scheme-specific meta-variables to better deduce the URI scheme.
- Note that this definition also allows URIs to be constructed which
- would invoke the script with any permitted values for the path-info
- or query-string, by modifying the appropriate components.
- 3.4. Execution
- The script is invoked in a system-defined manner. Unless specified
- otherwise, the file containing the script will be invoked as an
- executable program. The server prepares the CGI request as described
- in section 4; this comprises the request meta-variables (immediately
- available to the script on execution) and request message data. The
- request data need not be immediately available to the script; the
- script can be executed before all this data has been received by the
- server from the client. The response from the script is returned to
- the server as described in sections 5 and 6.
- In the event of an error condition, the server can interrupt or
- terminate script execution at any time and without warning. That
- could occur, for example, in the event of a transport failure between
- the server and the client; so the script SHOULD be prepared to handle
- abnormal termination.
- 4. The CGI Request
- Information about a request comes from two different sources; the
- request meta-variables and any associated message-body.
- 4.1. Request Meta-Variables
- Meta-variables contain data about the request passed from the server
- to the script, and are accessed by the script in a system-defined
- manner. Meta-variables are identified by case-insensitive names;
- there cannot be two different variables whose names differ in case
- only. Here they are shown using a canonical representation of
- capitals plus underscore ("_"). A particular system can define a
- different representation.
- Robinson & Coar Informational [Page 10]
- RFC 3875 CGI Version 1.1 October 2004
- meta-variable-name = "AUTH_TYPE" | "CONTENT_LENGTH" |
- "CONTENT_TYPE" | "GATEWAY_INTERFACE" |
- "PATH_INFO" | "PATH_TRANSLATED" |
- "QUERY_STRING" | "REMOTE_ADDR" |
- "REMOTE_HOST" | "REMOTE_IDENT" |
- "REMOTE_USER" | "REQUEST_METHOD" |
- "SCRIPT_NAME" | "SERVER_NAME" |
- "SERVER_PORT" | "SERVER_PROTOCOL" |
- "SERVER_SOFTWARE" | scheme |
- protocol-var-name | extension-var-name
- protocol-var-name = ( protocol | scheme ) "_" var-name
- scheme = alpha *( alpha | digit | "+" | "-" | "." )
- var-name = token
- extension-var-name = token
- Meta-variables with the same name as a scheme, and names beginning
- with the name of a protocol or scheme (e.g., HTTP_ACCEPT) are also
- defined. The number and meaning of these variables may change
- independently of this specification. (See also section 4.1.18.)
- The server MAY set additional implementation-defined extension meta-
- variables, whose names SHOULD be prefixed with "X_".
- This specification does not distinguish between zero-length (NULL)
- values and missing values. For example, a script cannot distinguish
- between the two requests http://host/script and http://host/script?
- as in both cases the QUERY_STRING meta-variable would be NULL.
- meta-variable-value = "" | 1*<TEXT, CHAR or tokens of value>
- An optional meta-variable may be omitted (left unset) if its value is
- NULL. Meta-variable values MUST be considered case-sensitive except
- as noted otherwise. The representation of the characters in the
- meta-variables is system-defined; the server MUST convert values to
- that representation.
- 4.1.1. AUTH_TYPE
- The AUTH_TYPE variable identifies any mechanism used by the server to
- authenticate the user. It contains a case-insensitive value defined
- by the client protocol or server implementation.
- For HTTP, if the client request required authentication for external
- access, then the server MUST set the value of this variable from the
- 'auth-scheme' token in the request Authorization header field.
- Robinson & Coar Informational [Page 11]
- RFC 3875 CGI Version 1.1 October 2004
- AUTH_TYPE = "" | auth-scheme
- auth-scheme = "Basic" | "Digest" | extension-auth
- extension-auth = token
- HTTP access authentication schemes are described in RFC 2617 [5].
- 4.1.2. CONTENT_LENGTH
- The CONTENT_LENGTH variable contains the size of the message-body
- attached to the request, if any, in decimal number of octets. If no
- data is attached, then NULL (or unset).
- CONTENT_LENGTH = "" | 1*digit
- The server MUST set this meta-variable if and only if the request is
- accompanied by a message-body entity. The CONTENT_LENGTH value must
- reflect the length of the message-body after the server has removed
- any transfer-codings or content-codings.
- 4.1.3. CONTENT_TYPE
- If the request includes a message-body, the CONTENT_TYPE variable is
- set to the Internet Media Type [6] of the message-body.
- CONTENT_TYPE = "" | media-type
- media-type = type "/" subtype *( ";" parameter )
- type = token
- subtype = token
- parameter = attribute "=" value
- attribute = token
- value = token | quoted-string
- The type, subtype and parameter attribute names are not
- case-sensitive. Parameter values may be case sensitive. Media types
- and their use in HTTP are described section 3.7 of the HTTP/1.1
- specification [4].
- There is no default value for this variable. If and only if it is
- unset, then the script MAY attempt to determine the media type from
- the data received. If the type remains unknown, then the script MAY
- choose to assume a type of application/octet-stream or it may reject
- the request with an error (as described in section 6.3.3).
- Each media-type defines a set of optional and mandatory parameters.
- This may include a charset parameter with a case-insensitive value
- defining the coded character set for the message-body. If the
- Robinson & Coar Informational [Page 12]
- RFC 3875 CGI Version 1.1 October 2004
- charset parameter is omitted, then the default value should be
- derived according to whichever of the following rules is the first to
- apply:
- 1. There MAY be a system-defined default charset for some
- media-types.
- 2. The default for media-types of type "text" is ISO-8859-1 [4].
- 3. Any default defined in the media-type specification.
- 4. The default is US-ASCII.
- The server MUST set this meta-variable if an HTTP Content-Type field
- is present in the client request header. If the server receives a
- request with an attached entity but no Content-Type header field, it
- MAY attempt to determine the correct content type, otherwise it
- should omit this meta-variable.
- 4.1.4. GATEWAY_INTERFACE
- The GATEWAY_INTERFACE variable MUST be set to the dialect of CGI
- being used by the server to communicate with the script. Syntax:
- GATEWAY_INTERFACE = "CGI" "/" 1*digit "." 1*digit
- Note that the major and minor numbers are treated as separate
- integers and hence each may be incremented higher than a single
- digit. Thus CGI/2.4 is a lower version than CGI/2.13 which in turn
- is lower than CGI/12.3. Leading zeros MUST be ignored by the script
- and MUST NOT be generated by the server.
- This document defines the 1.1 version of the CGI interface.
- 4.1.5. PATH_INFO
- The PATH_INFO variable specifies a path to be interpreted by the CGI
- script. It identifies the resource or sub-resource to be returned by
- the CGI script, and is derived from the portion of the URI path
- hierarchy following the part that identifies the script itself.
- Unlike a URI path, the PATH_INFO is not URL-encoded, and cannot
- contain path-segment parameters. A PATH_INFO of "/" represents a
- single void path segment.
- PATH_INFO = "" | ( "/" path )
- path = lsegment *( "/" lsegment )
- lsegment = *lchar
- lchar = <any TEXT or CTL except "/">
- Robinson & Coar Informational [Page 13]
- RFC 3875 CGI Version 1.1 October 2004
- The value is considered case-sensitive and the server MUST preserve
- the case of the path as presented in the request URI. The server MAY
- impose restrictions and limitations on what values it permits for
- PATH_INFO, and MAY reject the request with an error if it encounters
- any values considered objectionable. That MAY include any requests
- that would result in an encoded "/" being decoded into PATH_INFO, as
- this might represent a loss of information to the script. Similarly,
- treatment of non US-ASCII characters in the path is system-defined.
- URL-encoded, the PATH_INFO string forms the extra-path component of
- the Script-URI (see section 3.3) which follows the SCRIPT_NAME part
- of that path.
- 4.1.6. PATH_TRANSLATED
- The PATH_TRANSLATED variable is derived by taking the PATH_INFO
- value, parsing it as a local URI in its own right, and performing any
- virtual-to-physical translation appropriate to map it onto the
- server's document repository structure. The set of characters
- permitted in the result is system-defined.
- PATH_TRANSLATED = *<any character>
- This is the file location that would be accessed by a request for
- <scheme> "://" <server-name> ":" <server-port> <extra-path>
- where <scheme> is the scheme for the original client request and
- <extra-path> is a URL-encoded version of PATH_INFO, with ";", "=" and
- "?" reserved. For example, a request such as the following:
- http://somehost.com/cgi-bin/somescript/this%2eis%2epath%3binfo
- would result in a PATH_INFO value of
- /this.is.the.path;info
- An internal URI is constructed from the scheme, server location and
- the URL-encoded PATH_INFO:
- http://somehost.com/this.is.the.path%3binfo
- This would then be translated to a location in the server's document
- repository, perhaps a filesystem path something like this:
- /usr/local/www/htdocs/this.is.the.path;info
- The value of PATH_TRANSLATED is the result of the translation.
- Robinson & Coar Informational [Page 14]
- RFC 3875 CGI Version 1.1 October 2004
- The value is derived in this way irrespective of whether it maps to a
- valid repository location. The server MUST preserve the case of the
- extra-path segment unless the underlying repository supports case-
- insensitive names. If the repository is only case-aware, case-
- preserving, or case-blind with regard to document names, the server
- is not required to preserve the case of the original segment through
- the translation.
- The translation algorithm the server uses to derive PATH_TRANSLATED
- is implementation-defined; CGI scripts which use this variable may
- suffer limited portability.
- The server SHOULD set this meta-variable if the request URI includes
- a path-info component. If PATH_INFO is NULL, then the
- PATH_TRANSLATED variable MUST be set to NULL (or unset).
- 4.1.7. QUERY_STRING
- The QUERY_STRING variable contains a URL-encoded search or parameter
- string; it provides information to the CGI script to affect or refine
- the document to be returned by the script.
- The URL syntax for a search string is described in section 3 of RFC
- 2396 [2]. The QUERY_STRING value is case-sensitive.
- QUERY_STRING = query-string
- query-string = *uric
- uric = reserved | unreserved | escaped
- When parsing and decoding the query string, the details of the
- parsing, reserved characters and support for non US-ASCII characters
- depends on the context. For example, form submission from an HTML
- document [18] uses application/x-www-form-urlencoded encoding, in
- which the characters "+", "&" and "=" are reserved, and the ISO
- 8859-1 encoding may be used for non US-ASCII characters.
- The QUERY_STRING value provides the query-string part of the
- Script-URI. (See section 3.3).
- The server MUST set this variable; if the Script-URI does not include
- a query component, the QUERY_STRING MUST be defined as an empty
- string ("").
- 4.1.8. REMOTE_ADDR
- The REMOTE_ADDR variable MUST be set to the network address of the
- client sending the request to the server.
- Robinson & Coar Informational [Page 15]
- RFC 3875 CGI Version 1.1 October 2004
- REMOTE_ADDR = hostnumber
- hostnumber = ipv4-address | ipv6-address
- ipv4-address = 1*3digit "." 1*3digit "." 1*3digit "." 1*3digit
- ipv6-address = hexpart [ ":" ipv4-address ]
- hexpart = hexseq | ( [ hexseq ] "::" [ hexseq ] )
- hexseq = 1*4hex *( ":" 1*4hex )
- The format of an IPv6 address is described in RFC 3513 [15].
- 4.1.9. REMOTE_HOST
- The REMOTE_HOST variable contains the fully qualified domain name of
- the client sending the request to the server, if available, otherwise
- NULL. Fully qualified domain names take the form as described in
- section 3.5 of RFC 1034 [17] and section 2.1 of RFC 1123 [12].
- Domain names are not case sensitive.
- REMOTE_HOST = "" | hostname | hostnumber
- hostname = *( domainlabel "." ) toplabel [ "." ]
- domainlabel = alphanum [ *alphahypdigit alphanum ]
- toplabel = alpha [ *alphahypdigit alphanum ]
- alphahypdigit = alphanum | "-"
- The server SHOULD set this variable. If the hostname is not
- available for performance reasons or otherwise, the server MAY
- substitute the REMOTE_ADDR value.
- 4.1.10. REMOTE_IDENT
- The REMOTE_IDENT variable MAY be used to provide identity information
- reported about the connection by an RFC 1413 [20] request to the
- remote agent, if available. The server may choose not to support
- this feature, or not to request the data for efficiency reasons, or
- not to return available identity data.
- REMOTE_IDENT = *TEXT
- The data returned may be used for authentication purposes, but the
- level of trust reposed in it should be minimal.
- 4.1.11. REMOTE_USER
- The REMOTE_USER variable provides a user identification string
- supplied by client as part of user authentication.
- REMOTE_USER = *TEXT
- Robinson & Coar Informational [Page 16]
- RFC 3875 CGI Version 1.1 October 2004
- If the client request required HTTP Authentication [5] (e.g., the
- AUTH_TYPE meta-variable is set to "Basic" or "Digest"), then the
- value of the REMOTE_USER meta-variable MUST be set to the user-ID
- supplied.
- 4.1.12. REQUEST_METHOD
- The REQUEST_METHOD meta-variable MUST be set to the method which
- should be used by the script to process the request, as described in
- section 4.3.
- REQUEST_METHOD = method
- method = "GET" | "POST" | "HEAD" | extension-method
- extension-method = "PUT" | "DELETE" | token
- The method is case sensitive. The HTTP methods are described in
- section 5.1.1 of the HTTP/1.0 specification [1] and section 5.1.1 of
- the HTTP/1.1 specification [4].
- 4.1.13. SCRIPT_NAME
- The SCRIPT_NAME variable MUST be set to a URI path (not URL-encoded)
- which could identify the CGI script (rather than the script's
- output). The syntax is the same as for PATH_INFO (section 4.1.5)
- SCRIPT_NAME = "" | ( "/" path )
- The leading "/" is not part of the path. It is optional if the path
- is NULL; however, the variable MUST still be set in that case.
- The SCRIPT_NAME string forms some leading part of the path component
- of the Script-URI derived in some implementation-defined manner. No
- PATH_INFO segment (see section 4.1.5) is included in the SCRIPT_NAME
- value.
- 4.1.14. SERVER_NAME
- The SERVER_NAME variable MUST be set to the name of the server host
- to which the client request is directed. It is a case-insensitive
- hostname or network address. It forms the host part of the
- Script-URI.
- SERVER_NAME = server-name
- server-name = hostname | ipv4-address | ( "[" ipv6-address "]" )
- Robinson & Coar Informational [Page 17]
- RFC 3875 CGI Version 1.1 October 2004
- A deployed server can have more than one possible value for this
- variable, where several HTTP virtual hosts share the same IP address.
- In that case, the server would use the contents of the request's Host
- header field to select the correct virtual host.
- 4.1.15. SERVER_PORT
- The SERVER_PORT variable MUST be set to the TCP/IP port number on
- which this request is received from the client. This value is used
- in the port part of the Script-URI.
- SERVER_PORT = server-port
- server-port = 1*digit
- Note that this variable MUST be set, even if the port is the default
- port for the scheme and could otherwise be omitted from a URI.
- 4.1.16. SERVER_PROTOCOL
- The SERVER_PROTOCOL variable MUST be set to the name and version of
- the application protocol used for this CGI request. This MAY differ
- from the protocol version used by the server in its communication
- with the client.
- SERVER_PROTOCOL = HTTP-Version | "INCLUDED" | extension-version
- HTTP-Version = "HTTP" "/" 1*digit "." 1*digit
- extension-version = protocol [ "/" 1*digit "." 1*digit ]
- protocol = token
- Here, 'protocol' defines the syntax of some of the information
- passing between the server and the script (the 'protocol-specific'
- features). It is not case sensitive and is usually presented in
- upper case. The protocol is not the same as the scheme part of the
- script URI, which defines the overall access mechanism used by the
- client to communicate with the server. For example, a request that
- reaches the script with a protocol of "HTTP" may have used an "https"
- scheme.
- A well-known value for SERVER_PROTOCOL which the server MAY use is
- "INCLUDED", which signals that the current document is being included
- as part of a composite document, rather than being the direct target
- of the client request. The script should treat this as an HTTP/1.0
- request.
- Robinson & Coar Informational [Page 18]
- RFC 3875 CGI Version 1.1 October 2004
- 4.1.17. SERVER_SOFTWARE
- The SERVER_SOFTWARE meta-variable MUST be set to the name and version
- of the information server software making the CGI request (and
- running the gateway). It SHOULD be the same as the server
- description reported to the client, if any.
- SERVER_SOFTWARE = 1*( product | comment )
- product = token [ "/" product-version ]
- product-version = token
- comment = "(" *( ctext | comment ) ")"
- ctext = <any TEXT excluding "(" and ")">
- 4.1.18. Protocol-Specific Meta-Variables
- The server SHOULD set meta-variables specific to the protocol and
- scheme for the request. Interpretation of protocol-specific
- variables depends on the protocol version in SERVER_PROTOCOL. The
- server MAY set a meta-variable with the name of the scheme to a
- non-NULL value if the scheme is not the same as the protocol. The
- presence of such a variable indicates to a script which scheme is
- used by the request.
- Meta-variables with names beginning with "HTTP_" contain values read
- from the client request header fields, if the protocol used is HTTP.
- The HTTP header field name is converted to upper case, has all
- occurrences of "-" replaced with "_" and has "HTTP_" prepended to
- give the meta-variable name. The header data can be presented as
- sent by the client, or can be rewritten in ways which do not change
- its semantics. If multiple header fields with the same field-name
- are received then the server MUST rewrite them as a single value
- having the same semantics. Similarly, a header field that spans
- multiple lines MUST be merged onto a single line. The server MUST,
- if necessary, change the representation of the data (for example, the
- character set) to be appropriate for a CGI meta-variable.
- The server is not required to create meta-variables for all the
- header fields that it receives. In particular, it SHOULD remove any
- header fields carrying authentication information, such as
- 'Authorization'; or that are available to the script in other
- variables, such as 'Content-Length' and 'Content-Type'. The server
- MAY remove header fields that relate solely to client-side
- communication issues, such as 'Connection'.
- Robinson & Coar Informational [Page 19]
- RFC 3875 CGI Version 1.1 October 2004
- 4.2. Request Message-Body
- Request data is accessed by the script in a system-defined method;
- unless defined otherwise, this will be by reading the 'standard
- input' file descriptor or file handle.
- Request-Data = [ request-body ] [ extension-data ]
- request-body = <CONTENT_LENGTH>OCTET
- extension-data = *OCTET
- A request-body is supplied with the request if the CONTENT_LENGTH is
- not NULL. The server MUST make at least that many bytes available
- for the script to read. The server MAY signal an end-of-file
- condition after CONTENT_LENGTH bytes have been read or it MAY supply
- extension data. Therefore, the script MUST NOT attempt to read more
- than CONTENT_LENGTH bytes, even if more data is available. However,
- it is not obliged to read any of the data.
- For non-parsed header (NPH) scripts (section 5), the server SHOULD
- attempt to ensure that the data supplied to the script is precisely
- as supplied by the client and is unaltered by the server.
- As transfer-codings are not supported on the request-body, the server
- MUST remove any such codings from the message-body, and recalculate
- the CONTENT_LENGTH. If this is not possible (for example, because of
- large buffering requirements), the server SHOULD reject the client
- request. It MAY also remove content-codings from the message-body.
- 4.3. Request Methods
- The Request Method, as supplied in the REQUEST_METHOD meta-variable,
- identifies the processing method to be applied by the script in
- producing a response. The script author can choose to implement the
- methods most appropriate for the particular application. If the
- script receives a request with a method it does not support it SHOULD
- reject it with an error (see section 6.3.3).
- 4.3.1. GET
- The GET method indicates that the script should produce a document
- based on the meta-variable values. By convention, the GET method is
- 'safe' and 'idempotent' and SHOULD NOT have the significance of
- taking an action other than producing a document.
- The meaning of the GET method may be modified and refined by
- protocol-specific meta-variables.
- Robinson & Coar Informational [Page 20]
- RFC 3875 CGI Version 1.1 October 2004
- 4.3.2. POST
- The POST method is used to request the script perform processing and
- produce a document based on the data in the request message-body, in
- addition to meta-variable values. A common use is form submission in
- HTML [18], intended to initiate processing by the script that has a
- permanent affect, such a change in a database.
- The script MUST check the value of the CONTENT_LENGTH variable before
- reading the attached message-body, and SHOULD check the CONTENT_TYPE
- value before processing it.
- 4.3.3. HEAD
- The HEAD method requests the script to do sufficient processing to
- return the response header fields, without providing a response
- message-body. The script MUST NOT provide a response message-body
- for a HEAD request. If it does, then the server MUST discard the
- message-body when reading the response from the script.
- 4.3.4. Protocol-Specific Methods
- The script MAY implement any protocol-specific method, such as
- HTTP/1.1 PUT and DELETE; it SHOULD check the value of SERVER_PROTOCOL
- when doing so.
- The server MAY decide that some methods are not appropriate or
- permitted for a script, and may handle the methods itself or return
- an error to the client.
- 4.4. The Script Command Line
- Some systems support a method for supplying an array of strings to
- the CGI script. This is only used in the case of an 'indexed' HTTP
- query, which is identified by a 'GET' or 'HEAD' request with a URI
- query string that does not contain any unencoded "=" characters. For
- such a request, the server SHOULD treat the query-string as a
- search-string and parse it into words, using the rules
- search-string = search-word *( "+" search-word )
- search-word = 1*schar
- schar = unreserved | escaped | xreserved
- xreserved = ";" | "/" | "?" | ":" | "@" | "&" | "=" | "," |
- "$"
- After parsing, each search-word is URL-decoded, optionally encoded in
- a system-defined manner and then added to the command line argument
- list.
- Robinson & Coar Informational [Page 21]
- RFC 3875 CGI Version 1.1 October 2004
- If the server cannot create any part of the argument list, then the
- server MUST NOT generate any command line information. For example,
- the number of arguments may be greater than operating system or
- server limits, or one of the words may not be representable as an
- argument.
- The script SHOULD check to see if the QUERY_STRING value contains an
- unencoded "=" character, and SHOULD NOT use the command line
- arguments if it does.
- 5. NPH Scripts
- 5.1. Identification
- The server MAY support NPH (Non-Parsed Header) scripts; these are
- scripts to which the server passes all responsibility for response
- processing.
- This specification provides no mechanism for an NPH script to be
- identified on the basis of its output data alone. By convention,
- therefore, any particular script can only ever provide output of one
- type (NPH or CGI) and hence the script itself is described as an 'NPH
- script'. A server with NPH support MUST provide an implementation-
- defined mechanism for identifying NPH scripts, perhaps based on the
- name or location of the script.
- 5.2. NPH Response
- There MUST be a system-defined method for the script to send data
- back to the server or client; a script MUST always return some data.
- Unless defined otherwise, this will be the same as for conventional
- CGI scripts.
- Currently, NPH scripts are only defined for HTTP client requests. An
- (HTTP) NPH script MUST return a complete HTTP response message,
- currently described in section 6 of the HTTP specifications [1], [4].
- The script MUST use the SERVER_PROTOCOL variable to determine the
- appropriate format for a response. It MUST also take account of any
- generic or protocol-specific meta-variables in the request as might
- be mandated by the particular protocol specification.
- The server MUST ensure that the script output is sent to the client
- unmodified. Note that this requires the script to use the correct
- character set (US-ASCII [9] and ISO 8859-1 [10] for HTTP) in the
- header fields. The server SHOULD attempt to ensure that the script
- output is sent directly to the client, with minimal internal and no
- transport-visible buffering.
- Robinson & Coar Informational [Page 22]
- RFC 3875 CGI Version 1.1 October 2004
- Unless the implementation defines otherwise, the script MUST NOT
- indicate in its response that the client can send further requests
- over the same connection.
- 6. CGI Response
- 6.1. Response Handling
- A script MUST always provide a non-empty response, and so there is a
- system-defined method for it to send this data back to the server.
- Unless defined otherwise, this will be via the 'standard output' file
- descriptor.
- The script MUST check the REQUEST_METHOD variable when processing the
- request and preparing its response.
- The server MAY implement a timeout period within which data must be
- received from the script. If a server implementation defines such a
- timeout and receives no data from a script within the timeout period,
- the server MAY terminate the script process.
- 6.2. Response Types
- The response comprises a message-header and a message-body, separated
- by a blank line. The message-header contains one or more header
- fields. The body may be NULL.
- generic-response = 1*header-field NL [ response-body ]
- The script MUST return one of either a document response, a local
- redirect response or a client redirect (with optional document)
- response. In the response definitions below, the order of header
- fields in a response is not significant (despite appearing so in the
- BNF). The header fields are defined in section 6.3.
- CGI-Response = document-response | local-redir-response |
- client-redir-response | client-redirdoc-response
- 6.2.1. Document Response
- The CGI script can return a document to the user in a document
- response, with an optional error code indicating the success status
- of the response.
- document-response = Content-Type [ Status ] *other-field NL
- response-body
- Robinson & Coar Informational [Page 23]
- RFC 3875 CGI Version 1.1 October 2004
- The script MUST return a Content-Type header field. A Status header
- field is optional, and status 200 'OK' is assumed if it is omitted.
- The server MUST make any appropriate modifications to the script's
- output to ensure that the response to the client complies with the
- response protocol version.
- 6.2.2. Local Redirect Response
- The CGI script can return a URI path and query-string
- ('local-pathquery') for a local resource in a Location header field.
- This indicates to the server that it should reprocess the request
- using the path specified.
- local-redir-response = local-Location NL
- The script MUST NOT return any other header fields or a message-body,
- and the server MUST generate the response that it would have produced
- in response to a request containing the URL
- scheme "://" server-name ":" server-port local-pathquery
- 6.2.3. Client Redirect Response
- The CGI script can return an absolute URI path in a Location header
- field, to indicate to the client that it should reprocess the request
- using the URI specified.
- client-redir-response = client-Location *extension-field NL
- The script MUST not provide any other header fields, except for
- server-defined CGI extension fields. For an HTTP client request, the
- server MUST generate a 302 'Found' HTTP response message.
- 6.2.4. Client Redirect Response with Document
- The CGI script can return an absolute URI path in a Location header
- field together with an attached document, to indicate to the client
- that it should reprocess the request using the URI specified.
- client-redirdoc-response = client-Location Status Content-Type
- *other-field NL response-body
- The Status header field MUST be supplied and MUST contain a status
- value of 302 'Found', or it MAY contain an extension-code, that is,
- another valid status code that means client redirection. The server
- MUST make any appropriate modifications to the script's output to
- ensure that the response to the client complies with the response
- protocol version.
- Robinson & Coar Informational [Page 24]
- RFC 3875 CGI Version 1.1 October 2004
- 6.3. Response Header Fields
- The response header fields are either CGI or extension header fields
- to be interpreted by the server, or protocol-specific header fields
- to be included in the response returned to the client. At least one
- CGI field MUST be supplied; each CGI field MUST NOT appear more than
- once in the response. The response header fields have the syntax:
- header-field = CGI-field | other-field
- CGI-field = Content-Type | Location | Status
- other-field = protocol-field | extension-field
- protocol-field = generic-field
- extension-field = generic-field
- generic-field = field-name ":" [ field-value ] NL
- field-name = token
- field-value = *( field-content | LWSP )
- field-content = *( token | separator | quoted-string )
- The field-name is not case sensitive. A NULL field value is
- equivalent to a field not being sent. Note that each header field in
- a CGI-Response MUST be specified on a single line; CGI/1.1 does not
- support continuation lines. Whitespace is permitted between the ":"
- and the field-value (but not between the field-name and the ":"), and
- also between tokens in the field-value.
- 6.3.1. Content-Type
- The Content-Type response field sets the Internet Media Type [6] of
- the entity body.
- Content-Type = "Content-Type:" media-type NL
- If an entity body is returned, the script MUST supply a Content-Type
- field in the response. If it fails to do so, the server SHOULD NOT
- attempt to determine the correct content type. The value SHOULD be
- sent unmodified to the client, except for any charset parameter
- changes.
- Unless it is otherwise system-defined, the default charset assumed by
- the client for text media-types is ISO-8859-1 if the protocol is HTTP
- and US-ASCII otherwise. Hence the script SHOULD include a charset
- parameter. See section 3.4.1 of the HTTP/1.1 specification [4] for a
- discussion of this issue.
- Robinson & Coar Informational [Page 25]
- RFC 3875 CGI Version 1.1 October 2004
- 6.3.2. Location
- The Location header field is used to specify to the server that the
- script is returning a reference to a document rather than an actual
- document (see sections 6.2.3 and 6.2.4). It is either an absolute
- URI (optionally with a fragment identifier), indicating that the
- client is to fetch the referenced document, or a local URI path
- (optionally with a query string), indicating that the server is to
- fetch the referenced document and return it to the client as the
- response.
- Location = local-Location | client-Location
- client-Location = "Location:" fragment-URI NL
- local-Location = "Location:" local-pathquery NL
- fragment-URI = absoluteURI [ "#" fragment ]
- fragment = *uric
- local-pathquery = abs-path [ "?" query-string ]
- abs-path = "/" path-segments
- path-segments = segment *( "/" segment )
- segment = *pchar
- pchar = unreserved | escaped | extra
- extra = ":" | "@" | "&" | "=" | "+" | "$" | ","
- The syntax of an absoluteURI is incorporated into this document from
- that specified in RFC 2396 [2] and RFC 2732 [7]. A valid absoluteURI
- always starts with the name of scheme followed by ":"; scheme names
- start with a letter and continue with alphanumerics, "+", "-" or ".".
- The local URI path and query must be an absolute path, and not a
- relative path or NULL, and hence must start with a "/".
- Note that any message-body attached to the request (such as for a
- POST request) may not be available to the resource that is the target
- of the redirect.
- 6.3.3. Status
- The Status header field contains a 3-digit integer result code that
- indicates the level of success of the script's attempt to handle the
- request.
- Status = "Status:" status-code SP reason-phrase NL
- status-code = "200" | "302" | "400" | "501" | extension-code
- extension-code = 3digit
- reason-phrase = *TEXT
- Status code 200 'OK' indicates success, and is the default value
- assumed for a document response. Status code 302 'Found' is used
- with a Location header field and response message-body. Status code
- Robinson & Coar Informational [Page 26]
- RFC 3875 CGI Version 1.1 October 2004
- 400 'Bad Request' may be used for an unknown request format, such as
- a missing CONTENT_TYPE. Status code 501 'Not Implemented' may be
- returned by a script if it receives an unsupported REQUEST_METHOD.
- Other valid status codes are listed in section 6.1.1 of the HTTP
- specifications [1], [4], and also the IANA HTTP Status Code Registry
- [8] and MAY be used in addition to or instead of the ones listed
- above. The script SHOULD check the value of SERVER_PROTOCOL before
- using HTTP/1.1 status codes. The script MAY reject with error 405
- 'Method Not Allowed' HTTP/1.1 requests made using a method it does
- not support.
- Note that returning an error status code does not have to mean an
- error condition with the script itself. For example, a script that
- is invoked as an error handler by the server should return the code
- appropriate to the server's error condition.
- The reason-phrase is a textual description of the error to be
- returned to the client for human consumption.
- 6.3.4. Protocol-Specific Header Fields
- The script MAY return any other header fields that relate to the
- response message defined by the specification for the SERVER_PROTOCOL
- (HTTP/1.0 [1] or HTTP/1.1 [4]). The server MUST translate the header
- data from the CGI header syntax to the HTTP header syntax if these
- differ. For example, the character sequence for newline (such as
- UNIX's US-ASCII LF) used by CGI scripts may not be the same as that
- used by HTTP (US-ASCII CR followed by LF).
- The script MUST NOT return any header fields that relate to
- client-side communication issues and could affect the server's
- ability to send the response to the client. The server MAY remove
- any such header fields returned by the client. It SHOULD resolve any
- conflicts between header fields returned by the script and header
- fields that it would otherwise send itself.
- 6.3.5. Extension Header Fields
- There may be additional implementation-defined CGI header fields,
- whose field names SHOULD begin with "X-CGI-". The server MAY ignore
- (and delete) any unrecognised header fields with names beginning "X-
- CGI-" that are received from the script.
- Robinson & Coar Informational [Page 27]
- RFC 3875 CGI Version 1.1 October 2004
- 6.4. Response Message-Body
- The response message-body is an attached document to be returned to
- the client by the server. The server MUST read all the data provided
- by the script, until the script signals the end of the message-body
- by way of an end-of-file condition. The message-body SHOULD be sent
- unmodified to the client, except for HEAD requests or any required
- transfer-codings, content-codings or charset conversions.
- response-body = *OCTET
- 7. System Specifications
- 7.1. AmigaDOS
- Meta-Variables
- Meta-variables are passed to the script in identically named
- environment variables. These are accessed by the DOS library
- routine GetVar(). The flags argument SHOULD be 0. Case is
- ignored, but upper case is recommended for compatibility with
- case-sensitive systems.
- The current working directory
- The current working directory for the script is set to the
- directory containing the script.
- Character set
- The US-ASCII character set [9] is used for the definition of
- meta-variables, header fields and values; the newline (NL)
- sequence is LF; servers SHOULD also accept CR LF as a newline.
- 7.2. UNIX
- For UNIX compatible operating systems, the following are defined:
- Meta-Variables
- Meta-variables are passed to the script in identically named
- environment variables. These are accessed by the C library
- routine getenv() or variable environ.
- The command line
- This is accessed using the argc and argv arguments to main(). The
- words have any characters which are 'active' in the Bourne shell
- escaped with a backslash.
- The current working directory
- The current working directory for the script SHOULD be set to the
- directory containing the script.
- Robinson & Coar Informational [Page 28]
- RFC 3875 CGI Version 1.1 October 2004
- Character set
- The US-ASCII character set [9], excluding NUL, is used for the
- definition of meta-variables, header fields and CHAR values; TEXT
- values use ISO-8859-1. The PATH_TRANSLATED value can contain any
- 8-bit byte except NUL. The newline (NL) sequence is LF; servers
- should also accept CR LF as a newline.
- 7.3. EBCDIC/POSIX
- For POSIX compatible operating systems using the EBCDIC character
- set, the following are defined:
- Meta-Variables
- Meta-variables are passed to the script in identically named
- environment variables. These are accessed by the C library
- routine getenv().
- The command line
- This is accessed using the argc and argv arguments to main(). The
- words have any characters which are 'active' in the Bourne shell
- escaped with a backslash.
- The current working directory
- The current working directory for the script SHOULD be set to the
- directory containing the script.
- Character set
- The IBM1047 character set [21], excluding NUL, is used for the
- definition of meta-variables, header fields, values, TEXT strings
- and the PATH_TRANSLATED value. The newline (NL) sequence is LF;
- servers should also accept CR LF as a newline.
- media-type charset default
- The default charset value for text (and other implementation-
- defined) media types is IBM1047.
- 8. Implementation
- 8.1. Recommendations for Servers
- Although the server and the CGI script need not be consistent in
- their handling of URL paths (client URLs and the PATH_INFO data,
- respectively), server authors may wish to impose consistency. So the
- server implementation should specify its behaviour for the following
- cases:
- 1. define any restrictions on allowed path segments, in particular
- whether non-terminal NULL segments are permitted;
- Robinson & Coar Informational [Page 29]
- RFC 3875 CGI Version 1.1 October 2004
- 2. define the behaviour for "." or ".." path segments; i.e.,
- whether they are prohibited, treated as ordinary path segments
- or interpreted in accordance with the relative URL
- specification [2];
- 3. define any limits of the implementation, including limits on
- path or search string lengths, and limits on the volume of
- header fields the server will parse.
- 8.2. Recommendations for Scripts
- If the script does not intend processing the PATH_INFO data, then it
- should reject the request with 404 Not Found if PATH_INFO is not
- NULL.
- If the output of a form is being processed, check that CONTENT_TYPE
- is "application/x-www-form-urlencoded" [18] or "multipart/form-data"
- [16]. If CONTENT_TYPE is blank, the script can reject the request
- with a 415 'Unsupported Media Type' error, where supported by the
- protocol.
- When parsing PATH_INFO, PATH_TRANSLATED or SCRIPT_NAME the script
- should be careful of void path segments ("//") and special path
- segments ("." and ".."). They should either be removed from the path
- before use in OS system calls, or the request should be rejected with
- 404 'Not Found'.
- When returning header fields, the script should try to send the CGI
- header fields as soon as possible, and should send them before any
- HTTP header fields. This may help reduce the server's memory
- requirements.
- Script authors should be aware that the REMOTE_ADDR and REMOTE_HOST
- meta-variables (see sections 4.1.8 and 4.1.9) may not identify the
- ultimate source of the request. They identify the client for the
- immediate request to the server; that client may be a proxy, gateway,
- or other intermediary acting on behalf of the actual source client.
- 9. Security Considerations
- 9.1. Safe Methods
- As discussed in the security considerations of the HTTP
- specifications [1], [4], the convention has been established that the
- GET and HEAD methods should be 'safe' and 'idempotent' (repeated
- requests have the same effect as a single request). See section 9.1
- of RFC 2616 [4] for a full discussion.
- Robinson & Coar Informational [Page 30]
- RFC 3875 CGI Version 1.1 October 2004
- 9.2. Header Fields Containing Sensitive Information
- Some HTTP header fields may carry sensitive information which the
- server should not pass on to the script unless explicitly configured
- to do so. For example, if the server protects the script by using
- the Basic authentication scheme, then the client will send an
- Authorization header field containing a username and password. The
- server validates this information and so it should not pass on the
- password via the HTTP_AUTHORIZATION meta-variable without careful
- consideration. This also applies to the Proxy-Authorization header
- field and the corresponding HTTP_PROXY_AUTHORIZATION meta-variable.
- 9.3. Data Privacy
- Confidential data in a request should be placed in a message-body as
- part of a POST request, and not placed in the URI or message headers.
- On some systems, the environment used to pass meta-variables to a
- script may be visible to other scripts or users. In addition, many
- existing servers, proxies and clients will permanently record the URI
- where it might be visible to third parties.
- 9.4. Information Security Model
- For a client connection using TLS, the security model applies between
- the client and the server, and not between the client and the script.
- It is the server's responsibility to handle the TLS session, and thus
- it is the server which is authenticated to the client, not the CGI
- script.
- This specification provides no mechanism for the script to
- authenticate the server which invoked it. There is no enforced
- integrity on the CGI request and response messages.
- 9.5. Script Interference with the Server
- The most common implementation of CGI invokes the script as a child
- process using the same user and group as the server process. It
- should therefore be ensured that the script cannot interfere with the
- server process, its configuration, documents or log files.
- If the script is executed by calling a function linked in to the
- server software (either at compile-time or run-time) then precautions
- should be taken to protect the core memory of the server, or to
- ensure that untrusted code cannot be executed.
- Robinson & Coar Informational [Page 31]
- RFC 3875 CGI Version 1.1 October 2004
- 9.6. Data Length and Buffering Considerations
- This specification places no limits on the length of the message-body
- presented to the script. The script should not assume that
- statically allocated buffers of any size are sufficient to contain
- the entire submission at one time. Use of a fixed length buffer
- without careful overflow checking may result in an attacker
- exploiting 'stack-smashing' or 'stack-overflow' vulnerabilities of
- the operating system. The script may spool large submissions to disk
- or other buffering media, but a rapid succession of large submissions
- may result in denial of service conditions. If the CONTENT_LENGTH of
- a message-body is larger than resource considerations allow, scripts
- should respond with an error status appropriate for the protocol
- version; potentially applicable status codes include 503 'Service
- Unavailable' (HTTP/1.0 and HTTP/1.1), 413 'Request Entity Too Large'
- (HTTP/1.1), and 414 'Request-URI Too Large' (HTTP/1.1).
- Similar considerations apply to the server's handling of the CGI
- response from the script. There is no limit on the length of the
- header or message-body returned by the script; the server should not
- assume that statically allocated buffers of any size are sufficient
- to contain the entire response.
- 9.7. Stateless Processing
- The stateless nature of the Web makes each script execution and
- resource retrieval independent of all others even when multiple
- requests constitute a single conceptual Web transaction. Because of
- this, a script should not make any assumptions about the context of
- the user-agent submitting a request. In particular, scripts should
- examine data obtained from the client and verify that they are valid,
- both in form and content, before allowing them to be used for
- sensitive purposes such as input to other applications, commands, or
- operating system services. These uses include (but are not limited
- to) system call arguments, database writes, dynamically evaluated
- source code, and input to billing or other secure processes. It is
- important that applications be protected from invalid input
- regardless of whether the invalidity is the result of user error,
- logic error, or malicious action.
- Authors of scripts involved in multi-request transactions should be
- particularly cautious about validating the state information;
- undesirable effects may result from the substitution of dangerous
- values for portions of the submission which might otherwise be
- presumed safe. Subversion of this type occurs when alterations are
- made to data from a prior stage of the transaction that were not
- meant to be controlled by the client (e.g., hidden HTML form
- elements, cookies, embedded URLs, etc.).
- Robinson & Coar Informational [Page 32]
- RFC 3875 CGI Version 1.1 October 2004
- 9.8. Relative Paths
- The server should be careful of ".." path segments in the request
- URI. These should be removed or resolved in the request URI before
- it is split into the script-path and extra-path. Alternatively, when
- the extra-path is used to find the PATH_TRANSLATED, care should be
- taken to avoid the path resolution from providing translated paths
- outside an expected path hierarchy.
- 9.9. Non-parsed Header Output
- If a script returns a non-parsed header output, to be interpreted by
- the client in its native protocol, then the script must address all
- security considerations relating to that protocol.
- 10. Acknowledgements
- This work is based on the original CGI interface that arose out of
- discussions on the 'www-talk' mailing list. In particular, Rob
- McCool, John Franks, Ari Luotonen, George Phillips and Tony Sanders
- deserve special recognition for their efforts in defining and
- implementing the early versions of this interface.
- This document has also greatly benefited from the comments and
- suggestions made Chris Adie, Dave Kristol and Mike Meyer; also David
- Morris, Jeremy Madea, Patrick McManus, Adam Donahue, Ross Patterson
- and Harald Alvestrand.
- 11. References
- 11.1 Normative References
- [1] Berners-Lee, T., Fielding, R. and H. Frystyk, "Hypertext
- Transfer Protocol -- HTTP/1.0", RFC 1945, May 1996.
- [2] Berners-Lee, T., Fielding, R. and L. Masinter, "Uniform Resource
- Identifiers (URI) : Generic Syntax", RFC 2396, August 1998.
- [3] Bradner, S., "Key words for use in RFCs to Indicate Requirements
- Levels", BCP 14, RFC 2119, March 1997.
- [4] 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.
- [5] Franks, J., Hallam-Baker, P., Hostetler, J., Lawrence, S.,
- Leach, P., Luotonen, A., and L. Stewart, "HTTP Authentication:
- Basic and Digest Access Authentication", RFC 2617, June 1999.
- Robinson & Coar Informational [Page 33]
- RFC 3875 CGI Version 1.1 October 2004
- [6] Freed, N. and N. Borenstein, "Multipurpose Internet Mail
- Extensions (MIME) Part Two: Media Types", RFC 2046, November
- 1996.
- [7] Hinden, R., Carpenter, B., and L. Masinter, "Format for Literal
- IPv6 Addresses in URL's", RFC 2732, December 1999.
- [8] "HTTP Status Code Registry",
- http://www.iana.org/assignments/http-status-codes, IANA.
- [9] "Information Systems -- Coded Character Sets -- 7-bit American
- Standard Code for Information Interchange (7-Bit ASCII)", ANSI
- INCITS.4-1986 (R2002).
- [10] "Information technology -- 8-bit single-byte coded graphic
- character sets -- Part 1: Latin alphabet No. 1", ISO/IEC
- 8859-1:1998.
- 11.2. Informative References
- [11] Berners-Lee, T., "Universal Resource Identifiers in WWW: A
- Unifying Syntax for the Expression of Names and Addresses of
- Objects on the Network as used in the World-Wide Web", RFC 1630,
- June 1994.
- [12] Braden, R., Ed., "Requirements for Internet Hosts -- Application
- and Support", STD 3, RFC 1123, October 1989.
- [13] Crocker, D., "Standard for the Format of ARPA Internet Text
- Messages", STD 11, RFC 822, August 1982.
- [14] Dierks, T. and C. Allen, "The TLS Protocol Version 1.0", RFC
- 2246, January 1999.
- [15] Hinden R. and S. Deering, "Internet Protocol Version 6 (IPv6)
- Addressing Architecture", RFC 3513, April 2003.
- [16] Masinter, L., "Returning Values from Forms:
- multipart/form-data", RFC 2388, August 1998.
- [17] Mockapetris, P., "Domain Names - Concepts and Facilities", STD
- 13, RFC 1034, November 1987.
- [18] Raggett, D., Le Hors, A., and I. Jacobs, Eds., "HTML 4.01
- Specification", W3C Recommendation December 1999,
- http://www.w3.org/TR/html401/.
- [19] Rescola, E. "HTTP Over TLS", RFC 2818, May 2000.
- Robinson & Coar Informational [Page 34]
- RFC 3875 CGI Version 1.1 October 2004
- [20] St. Johns, M., "Identification Protocol", RFC 1413, February
- 1993.
- [21] IBM National Language Support Reference Manual Volume 2,
- SE09-8002-01, March 1990.
- [22] "The Common Gateway Interface",
- http://hoohoo.ncsa.uiuc.edu/cgi/, NCSA, University of Illinois.
- 12. Authors' Addresses
- David Robinson
- The Apache Software Foundation
- EMail: drtr@apache.org
- Ken A. L. Coar
- The Apache Software Foundation
- EMail: coar@apache.org
- Robinson & Coar Informational [Page 35]
- RFC 3875 CGI Version 1.1 October 2004
- 13. Full Copyright Statement
- Copyright (C) The Internet Society (2004). This document is subject
- to the rights, licenses and restrictions contained in BCP 78 and at
- www.rfc-editor.org, and except as set forth therein, the authors
- retain all their rights.
- This document and the information contained herein are provided on an
- "AS IS" basis and THE CONTRIBUTOR, THE ORGANIZATION HE/SHE REPRESENTS
- OR IS SPONSORED BY (IF ANY), THE INTERNET SOCIETY AND THE INTERNET
- ENGINEERING TASK FORCE DISCLAIM ALL WARRANTIES, EXPRESS OR IMPLIED,
- INCLUDING BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE
- INFORMATION HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED
- WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE.
- Intellectual Property
- The IETF takes no position regarding the validity or scope of any
- Intellectual Property Rights or other rights that might be claimed to
- pertain to the implementation or use of the technology described in
- this document or the extent to which any license under such rights
- might or might not be available; nor does it represent that it has
- made any independent effort to identify any such rights. Information
- on the ISOC's procedures with respect to rights in ISOC Documents can
- be found in BCP 78 and BCP 79.
- Copies of IPR disclosures made to the IETF Secretariat and any
- assurances of licenses to be made available, or the result of an
- attempt made to obtain a general license or permission for the use of
- such proprietary rights by implementers or users of this
- specification can be obtained from the IETF on-line IPR repository at
- http://www.ietf.org/ipr.
- The IETF invites any interested party to bring to its attention any
- copyrights, patents or patent applications, or other proprietary
- rights that may cover technology that may be required to implement
- this standard. Please address the information to the IETF at ietf-
- ipr@ietf.org.
- Acknowledgement
- Funding for the RFC Editor function is currently provided by the
- Internet Society.
- Robinson & Coar Informational [Page 36]