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<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.0 Transitional//EN"
"http://www.w3.org/TR/REC-html40/loose.dtd">
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<TITLE>Common Gateway Interface - 1.1 *Draft 03* [http://cgi-spec.golux.com/draft-coar-cgi-v11-03-clean.html]
</TITLE>
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<LINK REL="STYLESHEET" HREF="cgip-style-rfc.css" TYPE="text/css">
<META name="latexstyle" content="rfc">
<META name="author" content="Ken A L Coar">
<META name="institute" content="IBM Corporation">
<META name="date" content="25 June 1999">
<META name="expires" content="Expires 31 December 1999">
<META name="document" content="INTERNET-DRAFT">
<META name="file" content="<draft-coar-cgi-v11-03.txt>">
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<PRE>
Coar, et al. CGI/1.1 Specification May, 1998
INTERNET-DRAFT Expires 1 December 1998 [Page 2]
</PRE>
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<TD ALIGN="LEFT">
INTERNET-DRAFT
</TD>
<TD ALIGN="RIGHT">
Ken A L Coar
</TD>
</TR>
<TR VALIGN="TOP">
<TD ALIGN="LEFT">
draft-coar-cgi-v11-03.{html,txt}
</TD>
<TD ALIGN="RIGHT">
IBM Corporation
</TD>
</TR>
<TR VALIGN="TOP">
<TD ALIGN="LEFT">
</TD>
<TD ALIGN="RIGHT">
D.R.T. Robinson
</TD>
</TR>
<TR VALIGN="TOP">
<TD ALIGN="LEFT">
</TD>
<TD ALIGN="RIGHT">
E*TRADE UK Ltd.
</TD>
</TR>
<TR VALIGN="TOP">
<TD ALIGN="LEFT">
</TD>
<TD ALIGN="RIGHT">
25 June 1999
</TD>
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</TABLE>
</DIV>
<H1 ALIGN="CENTER">
The WWW Common Gateway Interface
<BR>
Version 1.1
</H1>
<!--#include virtual="I-D-statement" -->
<H2>
<A NAME="Abstract">
Abstract
</A>
</H2>
<P>
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.
</P>
<P>
The interface has been in use by the World-Wide Web 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 [NCSA-CGI].
This document also defines the use of the CGI/1.1 interface
on the Unix and AmigaDOS(tm) systems.
</P>
<P>
Discussion of this draft occurs on the CGI-WG mailing list; see the
project Web page at
<SAMP><URL:<A HREF="http://CGI-Spec.Golux.Com/"
>http://CGI-Spec.Golux.Com/</A>></SAMP>
for details on the mailing list and the status of the project.
</P>
<!--#if expr="$GUI" -->
<H2>
Revision History
</H2>
<P>
The revision history of this draft is being maintained using Web-based
GUI notation, such as struck-through characters and colour-coded
sections. The following legend describes how to determine the origin
of a particular revision according to the colour of the text:
</P>
<DL COMPACT>
<DT>Black
</DT>
<DD>Revision 00, released 28 May 1998
</DD>
<DT>Green
</DT>
<DD>Revision 01, released 28 December 1998
<BR>
Major structure change: Section 4, "Request Metadata (Meta-Variables)"
was moved entirely under <A HREF="#7.0">Section 7</A>, "Data Input to the
CGI Script."
Due to the size of this change, it is noted here and the text in its
former location does <EM>not</EM> appear as struckthrough. This has
caused major <A HREF="#6.0">sections 5</A> and following to decrement
by one. Other
large text movements are likewise not marked up. References to RFC
1738 were changed to 2396 (1738's replacement).
</DD>
<DT>Red
</DT>
<DD>Revision 02, released 2 April, 1999
<BR>
Added text to <A HREF="#8.3">section 8.3</A> defining correct handling
of HTTP/1.1
requests using "chunked" Transfer-Encoding. Labelled metavariable
names in <A HREF="#8.0">section 8</A> with the appropriate detail section
numbers.
Clarified allowed usage of <SAMP>Status</SAMP> and
<SAMP>Location</SAMP> response header fields. Included new
Internet-Draft language.
</DD>
<DT>Fuchsia
</DT>
<DD>Revision 03, released 25 June 1999
<BR>
Changed references from "HTTP" to "Protocol-Specific" for the listing of
things like HTTP_ACCEPT. Changed 'entity-body' and 'content-body' to
'message-body.' Added a note that response headers must comply with
requirements of the protocol level in use. Added a lot of stuff about
security (section 11). Clarified a bunch of productions. Pointed out
that zero-length and omitted values are indistinguishable in this
specification. Clarified production describing order of fields in
script response header. Clarified issues surrounding encoding of
data. Acknowledged additional contributors, and changed one of
the authors' addresses.
</DD>
</DL>
<!--#endif -->
<H2>
<A NAME="Contents">
Table of Contents
</A>
</H2>
<DIV ALIGN="CENTER">
<PRE>
1 Introduction..............................................<A
HREF="#1.0"
>TBD</A>
1.1 Purpose................................................<A
HREF="#1.1"
>TBD</A>
1.2 Requirements...........................................<A
HREF="#1.2"
>TBD</A>
1.3 Specifications.........................................<A
HREF="#1.3"
>TBD</A>
1.4 Terminology............................................<A
HREF="#1.4"
>TBD</A>
2 Notational Conventions and Generic Grammar................<A
HREF="#2.0"
>TBD</A>
2.1 Augmented BNF..........................................<A
HREF="#2.1"
>TBD</A>
2.2 Basic Rules............................................<A
HREF="#2.2"
>TBD</A>
3 Protocol Parameters.......................................<A
HREF="#3.0"
>TBD</A>
3.1 URL Encoding...........................................<A
HREF="#3.1"
>TBD</A>
3.2 The Script-URI.........................................<A
HREF="#3.2"
>TBD</A>
4 Invoking the Script.......................................<A
HREF="#4.0"
>TBD</A>
5 The CGI Script Command Line...............................<A
HREF="#5.0"
>TBD</A>
6 Data Input to the CGI Script..............................<A
HREF="#6.0"
>TBD</A>
6.1 Request Metadata (Metavariables).......................<A
HREF="#6.1"
>TBD</A>
6.1.1 AUTH_TYPE...........................................<A
HREF="#6.1.1"
>TBD</A>
6.1.2 CONTENT_LENGTH......................................<A
HREF="#6.1.2"
>TBD</A>
6.1.3 CONTENT_TYPE........................................<A
HREF="#6.1.3"
>TBD</A>
6.1.4 GATEWAY_INTERFACE...................................<A
HREF="#6.1.4"
>TBD</A>
6.1.5 Protocol-Specific Metavariables.....................<A
HREF="#6.1.5"
>TBD</A>
6.1.6 PATH_INFO...........................................<A
HREF="#6.1.6"
>TBD</A>
6.1.7 PATH_TRANSLATED.....................................<A
HREF="#6.1.7"
>TBD</A>
6.1.8 QUERY_STRING........................................<A
HREF="#6.1.8"
>TBD</A>
6.1.9 REMOTE_ADDR.........................................<A
HREF="#6.1.9"
>TBD</A>
6.1.10 REMOTE_HOST........................................<A
HREF="#6.1.10"
>TBD</A>
6.1.11 REMOTE_IDENT.......................................<A
HREF="#6.1.11"
>TBD</A>
6.1.12 REMOTE_USER........................................<A
HREF="#6.1.12"
>TBD</A>
6.1.13 REQUEST_METHOD.....................................<A
HREF="#6.1.13"
>TBD</A>
6.1.14 SCRIPT_NAME........................................<A
HREF="#6.1.14"
>TBD</A>
6.1.15 SERVER_NAME........................................<A
HREF="#6.1.15"
>TBD</A>
6.1.16 SERVER_PORT........................................<A
HREF="#6.1.16"
>TBD</A>
6.1.17 SERVER_PROTOCOL....................................<A
HREF="#6.1.17"
>TBD</A>
6.1.18 SERVER_SOFTWARE....................................<A
HREF="#6.1.18"
>TBD</A>
6.2 Request Message-Bodies................................<A
HREF="#6.2"
>TBD</A>
7 Data Output from the CGI Script...........................<A
HREF="#7.0"
>TBD</A>
7.1 Non-Parsed Header Output...............................<A
HREF="#7.1"
>TBD</A>
7.2 Parsed Header Output...................................<A
HREF="#7.2"
>TBD</A>
7.2.1 CGI header fields...................................<A
HREF="#7.2.1"
>TBD</A>
7.2.1.1 Content-Type.....................................<A
HREF="#7.2.1.1"
>TBD</A>
7.2.1.2 Location.........................................<A
HREF="#7.2.1.2"
>TBD</A>
7.2.1.3 Status...........................................<A
HREF="#7.2.1.3"
>TBD</A>
7.2.1.4 Extension header fields..........................<A
HREF="#7.2.1.3"
>TBD</A>
7.2.2 HTTP header fields..................................<A
HREF="#7.2.2"
>TBD</A>
8 Server Implementation.....................................<A
HREF="#8.0"
>TBD</A>
8.1 Requirements for Servers...............................<A
HREF="#8.1"
>TBD</A>
8.1.1 Script-URI..........................................<A
HREF="#8.1"
>TBD</A>
8.1.2 Request Message-body Handling.......................<A
HREF="#8.1.2"
>TBD</A>
8.1.3 Required Metavariables..............................<A
HREF="#8.1.3"
>TBD</A>
8.1.4 Response Compliance.................................<A
HREF="#8.1.4"
>TBD</A>
8.2 Recommendations for Servers............................<A
HREF="#8.2"
>TBD</A>
8.3 Summary of Metavariables...............................<A
HREF="#8.3"
>TBD</A>
9 Script Implementation.....................................<A
HREF="#9.0"
>TBD</A>
9.1 Requirements for Scripts...............................<A
HREF="#9.1"
>TBD</A>
9.2 Recommendations for Scripts............................<A
HREF="#9.2"
>TBD</A>
10 System Specifications....................................<A
HREF="#10.0"
>TBD</A>
10.1 AmigaDOS..............................................<A
HREF="#10.1"
>TBD</A>
10.2 Unix..................................................<A
HREF="#10.2"
>TBD</A>
11 Security Considerations..................................<A
HREF="#11.0"
>TBD</A>
11.1 Safe Methods..........................................<A
HREF="#11.1"
>TBD</A>
11.2 HTTP Header Fields Containing Sensitive Information...<A
HREF="#11.2"
>TBD</A>
11.3 Script Interference with the Server...................<A
HREF="#11.3"
>TBD</A>
11.4 Data Length and Buffering Considerations..............<A
HREF="#11.4"
>TBD</A>
11.5 Stateless Processing..................................<A
HREF="#11.5"
>TBD</A>
12 Acknowledgments..........................................<A
HREF="#12.0"
>TBD</A>
13 References...............................................<A
HREF="#13.0"
>TBD</A>
14 Authors' Addresses.......................................<A
HREF="#14.0"
>TBD</A>
</PRE>
</DIV>
<H2>
<A NAME="1.0">
1. Introduction
</A>
</H2>
<H3>
<A NAME="1.1">
1.1. Purpose
</A>
</H3>
<P>
Together the HTTP [<A HREF="#[3]">3</A>,<A HREF="#[8]">8</A>] server
and the CGI script are responsible
for servicing a client
request by sending back responses. The client
request comprises a Universal Resource Identifier (URI)
[<A HREF="#[1]">1</A>], a
request method, and various ancillary
information about the request
provided by the transport mechanism.
</P>
<P>
The CGI defines the abstract parameters, known as
metavariables,
which describe the client's
request. Together with a
concrete programmer interface this specifies a platform-independent
interface between the script and the HTTP server.
</P>
<H3>
<A NAME="1.2">
1.2. Requirements
</A>
</H3>
<P>
This specification uses the same words as RFC 1123
[<A HREF="#[5]">5</A>] to define the
significance of each particular requirement. These are:
</P><!--#if expr="! $GUI" -->
<P></P><!--#endif -->
<DL>
<DT><EM>MUST</EM>
</DT>
<DD>
<P>
This word or the adjective 'required' means that the item is an
absolute requirement of the specification.
</P>
</DD>
<DT><EM>SHOULD</EM>
</DT>
<DD>
<P>
This word or the adjective 'recommended' means that there may
exist valid reasons in particular circumstances to ignore this
item, but the full implications should be understood and the case
carefully weighed before choosing a different course.
</P>
</DD>
<DT><EM>MAY</EM>
</DT>
<DD>
<P>
This word or the adjective 'optional' means that this item is
truly optional. One vendor may choose to include the item because
a particular marketplace requires it or because it enhances the
product, for example; another vendor may omit the same item.
</P>
</DD>
</DL>
<P>
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.'
</P>
<H3>
<A NAME="1.3">
1.3. Specifications
</A>
</H3>
<P>
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 which are not specified:
</P>
<DL>
<DT><EM>system defined</EM>
</DT>
<DD>
<P>
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
<A HREF="#10.0"
>section 10</A> of this document.
New systems may be defined
by new specifications without revision of this document.
</P>
</DD>
<DT><EM>implementation defined</EM>
</DT>
<DD>
<P>
The behaviour of the feature may vary from implementation to
implementation, but a particular implementation must document its
behaviour.
</P>
</DD>
</DL>
<H3>
<A NAME="1.4">
1.4. Terminology
</A>
</H3>
<P>
This specification uses many terms defined in the HTTP/1.1
specification [<A HREF="#[8]">8</A>]; 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.
</P>
<DL>
<DT><EM>metavariable</EM>
</DT>
<DD>
<P>
A named parameter that 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.
</P>
</DD>
<DT><EM>script</EM>
</DT>
<DD>
<P>
The software which is invoked by the server <EM>via</EM> 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 <EM>may</EM> 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.
</P>
</DD>
<DT><EM>server</EM>
</DT>
<DD>
<P>
The application program which invokes the script in order to service
requests.
</P>
</DD>
</DL>
<H2>
<A NAME="2.0">
2. Notational Conventions and Generic Grammar
</A>
</H2>
<H3>
<A NAME="2.1">
2.1. Augmented BNF
</A>
</H3>
<P>
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 [<A HREF="#[6]">6</A>]. This augmented BNF contains
the following constructs:
</P>
<DL>
<DT>name = definition
</DT>
<DD>
<P>
The
definition by the equal character ("="). Whitespace is only
significant in that continuation lines of a definition are
indented.
</P>
</DD>
<DT>"literal"
</DT>
<DD>
<P>
Quotation marks (") surround literal text, except for a literal
quotation mark, which is surrounded by angle-brackets ("<" and ">").
Unless stated otherwise, the text is case-sensitive.
</P>
</DD>
<DT>rule1 | rule2
</DT>
<DD>
<P>
Alternative rules are separated by a vertical bar ("|").
</P>
</DD>
<DT>(rule1 rule2 rule3)
</DT>
<DD>
<P>
Elements enclosed in parentheses are treated as a single element.
</P>
</DD>
<DT>*rule
</DT>
<DD>
<P>
A rule preceded by an asterisk ("*") may have zero or more
occurrences. A rule preceded by an integer followed by an asterisk
must occur at least the specified number of times.
</P>
</DD>
<DT>[rule]
</DT>
<DD>
<P>
An element enclosed in square
brackets ("[" and "]") is optional.
</P>
</DD>
</DL>
<H3>
<A NAME="2.2">
2.2. Basic Rules
</A>
</H3>
<P>
The following rules are used throughout this specification to
describe basic parsing constructs.
</P><!--#if expr="! $GUI" -->
<P></P><!--#endif -->
<PRE>
alpha = lowalpha | hialpha
alphanum = alpha | digit
lowalpha = "a" | "b" | "c" | "d" | "e" | "f" | "g" | "h"
| "i" | "j" | "k" | "l" | "m" | "n" | "o" | "p"
| "q" | "r" | "s" | "t" | "u" | "v" | "w" | "x"
| "y" | "z"
hialpha = "A" | "B" | "C" | "D" | "E" | "F" | "G" | "H"
| "I" | "J" | "K" | "L" | "M" | "N" | "O" | "P"
| "Q" | "R" | "S" | "T" | "U" | "V" | "W" | "X"
| "Y" | "Z"
digit = "0" | "1" | "2" | "3" | "4" | "5" | "6" | "7"
| "8" | "9"
hex = digit | "A" | "B" | "C" | "D" | "E" | "F" | "a"
| "b" | "c" | "d" | "e" | "f"
escaped = "%" hex hex
OCTET = <any 8-bit sequence of data>
CHAR = <any US-ASCII character (octets 0 - 127)>
CTL = <any US-ASCII control character
(octets 0 - 31) and DEL (127)>
CR = <US-ASCII CR, carriage return (13)>
LF = <US-ASCII LF, linefeed (10)>
SP = <US-ASCII SP, space (32)>
HT = <US-ASCII HT, horizontal tab (9)>
NL = CR | LF
LWSP = SP | HT | NL
tspecial = "(" | ")" | "@" | "," | ";" | ":" | "\" | <">
| "/" | "[" | "]" | "?" | "<" | ">" | "{" | "}"
| SP | HT | NL
token = 1*<any CHAR except CTLs or tspecials>
quoted-string = ( <"> *qdtext <"> ) | ( "<" *qatext ">")
qdtext = <any CHAR except <"> and CTLs but including LWSP>
qatext = <any CHAR except "<", ">" and CTLs but
including LWSP>
mark = "-" | "_" | "." | "!" | "~" | "*" | "'" | "(" | ")"
unreserved = alphanum | mark
reserved = ";" | "/" | "?" | ":" | "@" | "&" | "=" |
"$" | ","
uric = reserved | unreserved | escaped
</PRE>
<P>
Note that newline (NL) need not be a single character, but can be a
character sequence.
</P>
<H2>
<A NAME="3.0">
3. Protocol Parameters
</A>
</H2>
<H3>
<A NAME="3.1">
3.1. URL Encoding
</A>
</H3>
<P>
Some variables and constructs used here are described as being
'URL-encoded'. This encoding is described in section
2 of RFC
2396
[<A HREF="#[4]">4</A>].
</P>
<P>
An alternate "shortcut" encoding for representing the space
character exists and is in common use. Scripts MUST be prepared to
recognise both '+' and '%20' as an encoded space in a
URL-encoded value.
</P>
<P>
Note that some unsafe characters may have different semantics if
they are encoded. The definition of which characters are unsafe
depends on the context.
For example, the following two URLs do not
necessarily refer to the same resource:
</P><!--#if expr="! $GUI" -->
<P></P><!--#endif -->
<PRE>
http://somehost.com/somedir%2Fvalue
http://somehost.com/somedir/value
</PRE>
<P>
See section
2 of RFC
2396 [<A HREF="#[4]">4</A>]
for authoritative treatment of this issue.
</P>
<H3>
<A NAME="3.2">
3.2. The Script-URI
</A>
</H3>
<P>
The 'Script-URI' is defined as the URI of the resource identified
by the metavariables. Often,
this URI will be the same as
the URI requested by the client (the 'Client-URI'); however, it need
not be. Instead, it could be a URI invented by the server, and so it
can only be used in the context of the server and its CGI interface.
</P>
<P>
The Script-URI has the syntax of generic-RL as defined in section 2.1
of RFC 1808 [<A HREF="#[7]">7</A>], with the exception that object
parameters and
fragment identifiers are not permitted:
</P><!--#if expr="! $GUI" -->
<P></P><!--#endif -->
<PRE>
<scheme>://<host><port>/<path>?<query>
</PRE>
<P>
The various components of the
Script-URI
are defined by some of the
metavariables (see
<A HREF="#4.0">section 4</A>
below);
</P><!--#if expr="! $GUI" -->
<P></P><!--#endif -->
<PRE>
script-uri = protocol "://" SERVER_NAME ":" SERVER_PORT enc-script
enc-path-info "?" QUERY_STRING
</PRE>
<P>
where 'protocol' is obtained
from SERVER_PROTOCOL, 'enc-script' is a
URL-encoded version of SCRIPT_NAME and 'enc-path-info' is a
URL-encoded version of PATH_INFO. See
<A HREF="#4.6">section 4.6</A> for more information about the PATH_INFO
metavariable.
</P>
<P>
Note that the scheme and the protocol are <EM>not</EM> identical;
for instance, a resource accessed <EM>via</EM> an SSL mechanism
may have a Client-URI with a scheme of "<SAMP>https</SAMP>"
rather than "<SAMP>http</SAMP>". CGI/1.1 provides no means
for the script to reconstruct this, and therefore
the Script-URI includes the base protocol used.
</P>
<H2>
<A NAME="4.0">
4. Invoking the Script
</A>
</H2>
<P>
The
script is invoked in a system defined manner. Unless specified
otherwise, the file containing the script will be invoked as an
executable program.
</P>
<H2>
<A NAME="5.0">
5. The CGI Script Command Line
</A>
</H2>
<P>
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' query.
This is identified by a "GET" or "HEAD" HTTP request with a URL
query
string not containing any unencoded "=" characters. For such a
request,
servers SHOULD parse the search string
into words, using the following rules:
</P><!--#if expr="! $GUI" -->
<P></P><!--#endif -->
<PRE>
search-string = search-word *( "+" search-word )
search-word = 1*schar
schar = xunreserved | escaped | xreserved
xunreserved = alpha | digit | xsafe | extra
xsafe = "$" | "-" | "_" | "."
xreserved = ";" | "/" | "?" | ":" | "@" | "&"
</PRE>
<P>
After parsing, each word is URL-decoded, optionally encoded in a
system defined manner,
and then the argument list is set to the list
of words.
</P>
<P>
If the server cannot create any part of the argument list, then the
server SHOULD NOT generate any command line information. For example, the
number of arguments may be greater than operating system or server
limitations permit, or one of the words may not be representable as an
argument.
</P>
<P>
Scripts SHOULD check to see if the QUERY_STRING value contains an
unencoded "=" character, and SHOULD NOT use the command line arguments
if it does.
</P>
<H2>
<A NAME="6.0">
6. Data Input to the CGI Script
</A>
</H2>
<P>
Information about a request comes from two different sources: the
request header, and any associated
message-body.
Servers MUST
make portions of this information available to
scripts.
</P>
<H3>
<A NAME="6.1">
6.1. Request Metadata
(Metavariables)
</A>
</H3>
<P>
Each CGI server
implementation MUST define a mechanism
to pass data about the request from
the server to the script.
The metavariables containing these
data
are accessed by the script in a system
defined manner.
The
representation of the characters in the
metavariables is
system defined.
</P>
<P>
This specification does not distinguish between the representation of
null values and missing ones. Whether null or missing values
(such as a query component of "?" or "", respectively) are represented
by undefined metavariables or by metavariables with values of "" is
implementation-defined.
</P>
<P>
Case is not significant in the
metavariable
names, in that there cannot be two
different variables
whose names differ in case only. Here they are
shown using a canonical representation of capitals plus underscore
("_"). The actual representation of the names is system defined; for
a particular system the representation MAY be defined differently
than this.
</P>
<P>
Metavariable
values MUST be
considered case-sensitive except as noted
otherwise.
</P>
<P>
The canonical
metavariables
defined by this specification are:
</P><!--#if expr="! $GUI" -->
<P></P><!--#endif -->
<PRE>
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
</PRE>
<P>
Metavariables with names beginning with the protocol name (<EM>e.g.</EM>,
"HTTP_ACCEPT") are also canonical in their description of request header
fields. The number and meaning of these fields may change independently
of this specification. (See also <A HREF="#6.1.5">section 6.1.5</A>.)
</P>
<H4>
<A NAME="6.1.1">
6.1.1. AUTH_TYPE
</A>
</H4>
<P>
This variable is specific to requests made
<EM>via</EM> the
"<CODE>http</CODE>"
scheme.
</P>
<P>
If the Script-URI
required access authentication for external
access, then the server
MUST set
the value of
this variable
from the '<SAMP>auth-scheme</SAMP>' token in
the request's "<SAMP>Authorization</SAMP>" header
field.
Otherwise
it is
set to NULL.
</P><!--#if expr="! $GUI" -->
<P></P><!--#endif -->
<PRE>
AUTH_TYPE = "" | auth-scheme
auth-scheme = "Basic" | "Digest" | token
</PRE>
<P>
HTTP access authentication schemes are described in section 11 of the
HTTP/1.1 specification [<A HREF="#[8]">8</A>]. The auth-scheme is
not case-sensitive.
</P>
<P>
Servers
MUST
provide this metavariable
to scripts if the request
header included an "<SAMP>Authorization</SAMP>" field
that was authenticated.
</P>
<H4>
<A NAME="6.1.2">
6.1.2. CONTENT_LENGTH
</A>
</H4>
<P>
This
metavariable
is set to the
size of the message-body
entity attached to the request, if any, in decimal
number of octets. If no data are attached, then this
metavariable
is either NULL or not
defined. The syntax is
the same as for
the HTTP "<SAMP>Content-Length</SAMP>" header field (section 14.14, HTTP/1.1
specification [<A HREF="#[8]">8</A>]).
</P><!--#if expr="! $GUI" -->
<P></P><!--#endif -->
<PRE>
CONTENT_LENGTH = "" | 1*digit
</PRE>
<P>
Servers MUST provide this metavariable
to scripts if the request
was accompanied by a
message-body entity.
</P>
<H4>
<A NAME="6.1.3">
6.1.3. CONTENT_TYPE
</A>
</H4>
<P>
If the request includes a
message-body,
CONTENT_TYPE is set
to
the Internet Media Type
[<A HREF="#[9]">9</A>] of the attached
entity if the type was provided <EM>via</EM>
a "<SAMP>Content-type</SAMP>" field in the
request header, or if the server can determine it in the absence
of a supplied "<SAMP>Content-type</SAMP>" field. The syntax is the
same as for the HTTP
"<SAMP>Content-Type</SAMP>" header field.
</P><!--#if expr="! $GUI" -->
<P></P><!--#endif -->
<PRE>
CONTENT_TYPE = "" | media-type
media-type = type "/" subtype *( ";" parameter)
type = token
subtype = token
parameter = attribute "=" value
attribute = token
value = token | quoted-string
</PRE>
<P>
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
in section 3.7 of the
HTTP/1.1 specification [<A HREF="#[8]">8</A>].
</P>
<P>
Example:
</P><!--#if expr="! $GUI" -->
<P></P><!--#endif -->
<PRE>
application/x-www-form-urlencoded
</PRE>
<P>
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 either assume a
content-type of
<SAMP>application/octet-stream</SAMP>
or reject the request with a 415 ("Unsupported Media Type")
error. See <A HREF="#7.2.1.3">section 7.2.1.3</A>
for more information about returning error status values.
</P>
<P>
Servers MUST provide this metavariable
to scripts if
a "<SAMP>Content-Type</SAMP>" field was present
in the original request header. If the server receives a request
with an attached entity but no "<SAMP>Content-Type</SAMP>"
header field, it MAY attempt to
determine the correct datatype, or it MAY omit this
metavariable when
communicating the request information to the script.
</P>
<H4>
<A NAME="6.1.4">
6.1.4. GATEWAY_INTERFACE
</A>
</H4>
<P>
This
metavariable
is set to
the dialect of CGI being used
by the server to communicate with the script.
Syntax:
</P><!--#if expr="! $GUI" -->
<P></P><!--#endif -->
<PRE>
GATEWAY_INTERFACE = "CGI" "/" major "." minor
major = 1*digit
minor = 1*digit
</PRE>
<P>
Note that the major and minor numbers are treated as separate
integers and hence each may be
more 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 in either
the major or the minor number MUST be ignored by scripts and
SHOULD NOT be generated by servers.
</P>
<P>
This document defines the 1.1 version of the CGI interface
("CGI/1.1").
</P>
<P>
Servers MUST provide this metavariable
to scripts.
</P>
<H4>
<A NAME="6.1.5">
6.1.5. Protocol-Specific Metavariables
</A>
</H4>
<P>
These metavariables are specific to
the protocol
<EM>via</EM> which the request is made.
Interpretation of these variables depends on the value of
the
SERVER_PROTOCOL
metavariable
(see
<A HREF="#6.1.17">section 6.1.17</A>).
</P>
<P>
Metavariables
with names beginning with "HTTP_" contain
values from the request header, if the
scheme used was HTTP.
Each
HTTP header field name is converted to upper case, has all occurrences of
"-" replaced with "_",
and has "HTTP_" prepended to form
the metavariable name.
Similar transformations are applied for other
protocols.
The header data MAY be presented as sent
by the client, or MAY 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 though they
had been received as a single header field having the same
semantics before being represented in a
metavariable.
Similarly, a header field that is received on more than one line
MUST be merged into 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
metavariable.
<!-- ###NOTE: See if 2068 describes this thoroughly, and
point there if so. -->
</P>
<P>
Servers are
not required to create
metavariables for all
the request
header fields that they
receive. In particular,
they MAY
decline to make available any
header fields carrying authentication information, such as
"<SAMP>Authorization</SAMP>", or
which are available to the script
<EM>via</EM> other metavariables,
such as "<SAMP>Content-Length</SAMP>" and "<SAMP>Content-Type</SAMP>".
</P>
<H4>
<A NAME="6.1.6">
6.1.6. PATH_INFO
</A>
</H4>
<P>
The PATH_INFO
metavariable
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 it is derived from the portion
of the URI path following the script name but preceding
any query data.
The syntax
and semantics are similar to a decoded HTTP URL
'path' token
(defined in
RFC 2396
[<A HREF="#[4]">4</A>]), with the exception
that a PATH_INFO of "/"
represents a single void path segment.
</P><!--#if expr="! $GUI" -->
<P></P><!--#endif -->
<PRE>
PATH_INFO = "" | ( "/" path )
path = segment *( "/" segment )
segment = *pchar
pchar = <any CHAR except "/">
</PRE>
<P>
The PATH_INFO string is the trailing part of the <path> component of
the Script-URI
(see <A HREF="#3.2">section 3.2</A>)
that follows the SCRIPT_NAME
portion of the path.
</P>
<P>
Servers MAY impose their own restrictions and
limitations on what values they will accept for PATH_INFO, and MAY
reject or edit any values they
consider objectionable before passing
them to the script.
</P>
<P>
Servers MUST make this URI component available
to CGI scripts. The PATH_INFO
value is case-sensitive, and the
server MUST preserve the case of the PATH_INFO element of the URI
when making it available to scripts.
</P>
<H4>
<A NAME="6.1.7">
6.1.7. PATH_TRANSLATED
</A>
</H4>
<P>
PATH_TRANSLATED is derived by taking any path-info component of the
request URI (see
<A HREF="#6.1.6">section 6.1.6</A>), decoding it
(see <A HREF="#3.1">section 3.1</A>), parsing it as a URI in its own
right, and performing any virtual-to-physical
translation appropriate to map it onto the
server's document repository structure.
If the request URI includes no path-info
component, the PATH_TRANSLATED metavariable SHOULD NOT be defined.
</P><!--#if expr="! $GUI" -->
<P></P><!--#endif -->
<PRE>
PATH_TRANSLATED = *CHAR
</PRE>
<P>
For a request such as the following:
</P><!--#if expr="! $GUI" -->
<P></P><!--#endif -->
<PRE>
http://somehost.com/cgi-bin/somescript/this%2eis%2epath%2einfo
</PRE>
<P>
the PATH_INFO component would be decoded, and the result
parsed as though it were a request for the following:
</P><!--#if expr="! $GUI" -->
<P></P><!--#endif -->
<PRE>
http://somehost.com/this.is.the.path.info
</PRE>
<P>
This would then be translated to a
location in the server's document repository,
perhaps a filesystem path something
like this:
</P><!--#if expr="! $GUI" -->
<P></P><!--#endif -->
<PRE>
/usr/local/www/htdocs/this.is.the.path.info
</PRE>
<P>
The result of the translation is the value of PATH_TRANSLATED.
</P>
<P>
The value of PATH_TRANSLATED may or may not map to a valid
repository
location.
Servers MUST preserve the case of the path-info
segment if and only if the underlying
repository
supports case-sensitive
names. If the
repository
is only case-aware, case-preserving, or case-blind
with regard to
document names,
servers are not required to preserve the
case of the original segment through the translation.
</P>
<P>
The
translation
algorithm the server uses to derive PATH_TRANSLATED is
implementation defined; CGI scripts which use this variable may
suffer limited portability.
</P>
<P>
Servers SHOULD provide this metavariable
to scripts if and only if the request URI includes a
path-info component.
</P>
<H4>
<A NAME="6.1.8">
6.1.8. QUERY_STRING
</A>
</H4>
<P>
A URL-encoded
string; the <query> part of the
Script-URI.
(See
<A HREF="#3.2">section 3.2</A>.)
</P><!--#if expr="! $GUI" -->
<P></P><!--#endif -->
<PRE>
QUERY_STRING = query-string
query-string = *uric
</PRE>
<P>
The URL syntax for a query
string is described in
section 3 of
RFC 2396
[<A HREF="#[4]">4</A>].
</P>
<P>
Servers MUST supply this value to scripts.
The QUERY_STRING value is case-sensitive.
If the Script-URI does not include a query component,
the QUERY_STRING metavariable MUST be defined as an empty string ("").
</P>
<H4>
<A NAME="6.1.9">
6.1.9. REMOTE_ADDR
</A>
</H4>
<P>
The IP address of the client
sending the request to the server. This
is not necessarily that of the user
agent
(such as if the request came through a proxy).
</P><!--#if expr="! $GUI" -->
<P></P><!--#endif -->
<PRE>
REMOTE_ADDR = hostnumber
hostnumber = ipv4-address | ipv6-address
</PRE>
<P>
The definitions of <SAMP>ipv4-address</SAMP> and <SAMP>ipv6-address</SAMP>
are provided in Appendix B of RFC 2373 [<A HREF="#[13]">13</A>].
</P>
<P>
Servers MUST supply this value to scripts.
</P>
<H4>
<A NAME="6.1.10">
6.1.10. REMOTE_HOST
</A>
</H4>
<P>
The fully qualified domain name of the
client sending the request to
the server, if available, otherwise NULL.
(See <A HREF="#6.1.9">section 6.1.9</A>.)
Fully qualified domain names take the form as described in
section 3.5 of RFC 1034 [<A HREF="#[10]">10</A>] and section 2.1 of
RFC 1123 [<A HREF="#[5]">5</A>]. Domain names are not case sensitive.
</P>
<P>
Servers SHOULD provide this information to
scripts.
</P>
<H4>
<A NAME="6.1.11">
6.1.11. REMOTE_IDENT
</A>
</H4>
<P>
The identity information reported about the connection by a
RFC 1413 [<A HREF="#[11]">11</A>] request to the remote agent, if
available. Servers
MAY choose not
to support this feature, or not to request the data
for efficiency reasons.
</P><!--#if expr="! $GUI" -->
<P></P><!--#endif -->
<PRE>
REMOTE_IDENT = *CHAR
</PRE>
<P>
The data returned
may be used for authentication purposes, but the level
of trust reposed in them should be minimal.
</P>
<P>
Servers MAY supply this information to scripts if the
RFC1413 [<A HREF="#[11]">11</A>] lookup is performed.
</P>
<H4>
<A NAME="6.1.12">
6.1.12. REMOTE_USER
</A>
</H4>
<P>
If the request required authentication using the "Basic"
mechanism (<EM>i.e.</EM>, the AUTH_TYPE
metavariable is set
to "Basic"), then the value of the REMOTE_USER
metavariable is set to the
user-ID supplied. In all other cases
the value of this metavariable
is undefined.
</P><!--#if expr="! $GUI" -->
<P></P><!--#endif -->
<PRE>
REMOTE_USER = *OCTET
</PRE>
<P>
This variable is specific to requests made <EM>via</EM> the
HTTP protocol.
</P>
<P>
Servers SHOULD provide this metavariable
to scripts.
</P>
<H4>
<A NAME="6.1.13">
6.1.13. REQUEST_METHOD
</A>
</H4>
<P>
The REQUEST_METHOD
metavariable
is set to the
method with which the request was made, as described in section
5.1.1 of the HTTP/1.0 specification [<A HREF="#[3]">3</A>] and
section 5.1.1 of the
HTTP/1.1 specification [<A HREF="#[8]">8</A>].
</P><!--#if expr="! $GUI" -->
<P></P><!--#endif -->
<PRE>
REQUEST_METHOD = http-method
http-method = "GET" | "HEAD" | "POST" | "PUT" | "DELETE"
| "OPTIONS" | "TRACE" | extension-method
extension-method = token
</PRE>
<P>
The method is case sensitive.
CGI/1.1 servers MAY choose to process some methods
directly rather than passing them to scripts.
</P>
<P>
This variable is specific to requests made with HTTP.
</P>
<P>
Servers MUST provide this metavariable
to scripts.
</P>
<H4>
<A NAME="6.1.14">
6.1.14. SCRIPT_NAME
</A>
</H4>
<P>
The SCRIPT_NAME
metavariable
is
set to a URL path that could identify the CGI script (rather than the
script's
output). The syntax and semantics are identical to a
decoded HTTP URL 'path' token
(see RFC 2396
[<A HREF="#[4]">4</A>]).
</P><!--#if expr="! $GUI" -->
<P></P><!--#endif -->
<PRE>
SCRIPT_NAME = "" | ( "/" [ path ] )
</PRE>
<P>
The SCRIPT_NAME string is some leading part of the <path> component
of the Script-URI derived in some
implementation defined manner.
No PATH_INFO or QUERY_STRING segments
(see sections <A HREF="#6.1.6">6.1.6</A> and
<A HREF="#6.1.8">6.1.8</A>) are included
in the SCRIPT_NAME value.
</P>
<P>
Servers MUST provide this metavariable
to scripts.
</P>
<H4>
<A NAME="6.1.15">
6.1.15. SERVER_NAME
</A>
</H4>
<P>
The SERVER_NAME
metavariable
is set to the
name of the
server, as
derived from the <host> part of the
Script-URI
(see <A HREF="#3.2">section 3.2</A>).
</P><!--#if expr="! $GUI" -->
<P></P><!--#endif -->
<PRE>
SERVER_NAME = hostname | hostnumber
</PRE>
<P>
Servers MUST provide this metavariable
to scripts.
</P>
<H4>
<A NAME="6.1.16">
6.1.16. SERVER_PORT
</A>
</H4>
<P>
The SERVER_PORT
metavariable
is set to the
port on which the
request was received, as used in the <port>
part of the Script-URI.
</P><!--#if expr="! $GUI" -->
<P></P><!--#endif -->
<PRE>
SERVER_PORT = 1*digit
</PRE>
<P>
If the <port> portion of the script-URI is blank, the actual
port number upon which the request was received MUST be supplied.
</P>
<P>
Servers MUST provide this metavariable
to scripts.
</P>
<H4>
<A NAME="6.1.17">
6.1.17. SERVER_PROTOCOL
</A>
</H4>
<P>
The SERVER_PROTOCOL
metavariable
is set to
the
name and revision of the information protocol with which
the
request
arrived. This is not necessarily the same as the protocol version used by
the server in its response to the client.
</P><!--#if expr="! $GUI" -->
<P></P><!--#endif -->
<PRE>
SERVER_PROTOCOL = HTTP-Version | extension-version
| extension-token
HTTP-Version = "HTTP" "/" 1*digit "." 1*digit
extension-version = protocol "/" 1*digit "." 1*digit
protocol = 1*( alpha | digit | "+" | "-" | "." )
extension-token = token
</PRE>
<P>
'protocol' is a version of the <scheme> part of the
Script-URI, but is
not identical to it. For example, the scheme of a request may be
"<SAMP>https</SAMP>" while the protocol remains "<SAMP>http</SAMP>".
The protocol is not case sensitive, but
by convention, 'protocol' is in
upper case.
</P>
<P>
A well-known extension token value 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.
</P>
<P>
Servers MUST provide this metavariable
to scripts.
</P>
<H4>
<A NAME="6.1.18">
6.1.18. SERVER_SOFTWARE
</A>
</H4>
<P>
The SERVER_SOFTWARE
metavariable
is set to the
name and version of the information server software answering the
request (and running the gateway).
</P><!--#if expr="! $GUI" -->
<P></P><!--#endif -->
<PRE>
SERVER_SOFTWARE = 1*product
product = token [ "/" product-version ]
product-version = token
</PRE>
<P>
Servers MUST provide this metavariable
to scripts.
</P>
<H3>
<A NAME="6.2">
6.2. Request Message-Bodies
</A>
</H3>
<P>
As there may be a data entity attached to the request, there MUST be
a system defined method for the script to read
these data. Unless
defined otherwise, this will be <EM>via</EM> the 'standard input' file
descriptor.
</P>
<P>
If the CONTENT_LENGTH value (see <A HREF="#6.1.2">section 6.1.2</A>)
is non-NULL, the server MUST supply at least that many bytes to
scripts on the standard input stream.
Scripts are
not obliged to read the data.
Servers MAY signal an EOF condition after CONTENT_LENGTH bytes have been
read, but are
not obligated to do so. Therefore, scripts
MUST NOT
attempt to read more than CONTENT_LENGTH bytes, even if more data
are available.
</P>
<P>
For non-parsed header (NPH) scripts (see
<A HREF="#7.1">section 7.1</A>
below),
servers SHOULD
attempt to ensure that the data
supplied to the script are precisely
as supplied by the client and unaltered by
the server.
</P>
<P>
<A HREF="#8.1.2">Section 8.1.2</A> describes the requirements of
servers with regard to requests that include
message-bodies.
</P>
<H2>
<A NAME="7.0">
7. Data Output from the CGI Script
</A>
</H2>
<P>
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 <EM>via</EM> the 'standard
output' file descriptor.
</P>
<P>
There are two forms of output that scripts can supply to servers: non-parsed
header (NPH) output, and parsed header output.
Servers MUST support parsed header
output and MAY support NPH output. The method of
distinguishing between the two
types of output (or scripts) is implementation defined.
</P>
<P>
Servers MAY implement a timeout period within which data must be
received from scripts. 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 and SHOULD
abort the client request with
either a
'504 Gateway Timed Out' or a
'500 Internal Server Error' response.
</P>
<H3>
<A NAME="7.1">
7.1. Non-Parsed Header Output
</A>
</H3>
<P>
Scripts using the NPH output form
MUST return a complete HTTP response message, as described
in Section 6 of the HTTP specifications
[<A HREF="#[3]">3</A>,<A HREF="#[8]">8</A>].
NPH scripts
MUST use the SERVER_PROTOCOL variable to determine the appropriate format
for a response.
</P>
<P>
Servers
SHOULD attempt to ensure that the script output is sent
directly to the client, with minimal
internal and no transport-visible
buffering.
</P>
<H3>
<A NAME="7.2">
7.2. Parsed Header Output
</A>
</H3>
<P>
Scripts using the parsed header output form MUST supply
a CGI response message to the server
as follows:
</P><!--#if expr="! $GUI" -->
<P></P><!--#endif -->
<PRE>
CGI-Response = *optional-field CGI-Field *optional-field NL [ Message-Body ]
optional-field = ( CGI-Field | HTTP-Field )
CGI-Field = Content-type
| Location
| Status
| extension-header
</PRE>
<P><!-- ##### If HTTP defines x-headers, remove ours except x-cgi- -->
The response comprises a header and a body, separated by a blank line.
The body may be NULL.
The header fields are either CGI header fields to be interpreted by
the server, or HTTP header fields
to be included in the response returned
to the client
if the request method is HTTP. At least one
CGI-Field MUST be
supplied, but no CGI field name may be used more than once
in a response.
If a body is supplied, then a "<SAMP>Content-type</SAMP>"
header field MUST be
supplied by the script,
otherwise the script MUST send a "<SAMP>Location</SAMP>"
or "<SAMP>Status</SAMP>" header field. If a
<SAMP>Location</SAMP> CGI-Field
is returned, then the script MUST NOT supply
any HTTP-Fields.
</P>
<P>
Each header field in a CGI-Response MUST be specified on a single line;
CGI/1.1 does not support continuation lines.
</P>
<H4>
<A NAME="7.2.1">
7.2.1. CGI header fields
</A>
</H4>
<P>
The CGI header fields have the generic syntax:
</P><!--#if expr="! $GUI" -->
<P></P><!--#endif -->
<PRE>
generic-field = field-name ":" [ field-value ] NL
field-name = token
field-value = *( field-content | LWSP )
field-content = *( token | tspecial | quoted-string )
</PRE>
<P>
The field-name is not case sensitive; a NULL field value is
equivalent to the header field not being sent.
</P>
<H4>
<A NAME="7.2.1.1">
7.2.1.1. Content-Type
</A>
</H4>
<P>
The Internet Media Type [<A HREF="#[9]">9</A>] of the entity
body, which is to be sent unmodified to the client.
</P><!--#if expr="! $GUI" -->
<P></P><!--#endif -->
<PRE>
Content-Type = "Content-Type" ":" media-type NL
</PRE>
<P>
This is actually an HTTP-Field
rather than a CGI-Field, but
it is listed here because of its importance in the CGI dialogue as
a member of the "one of these is required" set of header
fields.
</P>
<H4>
<A NAME="7.2.1.2">
7.2.1.2. Location
</A>
</H4>
<P>
This is used to specify to the server that the script is returning a
reference to a document rather than an actual document.
</P><!--#if expr="! $GUI" -->
<P></P><!--#endif -->
<PRE>
Location = "Location" ":"
( fragment-URI | rel-URL-abs-path ) NL
fragment-URI = URI [ # fragmentid ]
URI = scheme ":" *qchar
fragmentid = *qchar
rel-URL-abs-path = "/" [ hpath ] [ "?" query-string ]
hpath = fpsegment *( "/" psegment )
fpsegment = 1*hchar
psegment = *hchar
hchar = alpha | digit | safe | extra
| ":" | "@" | "& | "="
</PRE>
<P>
The Location
value is either an absolute URI with optional fragment,
as defined in RFC 1630 [<A HREF="#[1]">1</A>], or an absolute path
within the server's URI space (<EM>i.e.</EM>,
omitting the scheme and network-related fields) and optional
query-string. If an absolute URI is returned by the script,
then the
server MUST generate a
'302 redirect' HTTP response
message unless the script has supplied an
explicit Status response header field.
Scripts returning an absolute URI MAY choose to
provide a message-body. Servers MUST make any appropriate modifications
to the script's output to ensure the response to the user-agent complies
with the response protocol version.
If the Location value is a path, then the server
MUST generate
the response that it would have produced in response to a request
containing the URL
</P><!--#if expr="! $GUI" -->
<P></P><!--#endif -->
<PRE>
scheme "://" SERVER_NAME ":" SERVER_PORT rel-URL-abs-path
</PRE>
<P>
Note: If the request was accompanied by a
message-body
(such as for a POST request), and the script
redirects the request with a Location field, the
message-body
may not be
available to the resource that is the target of the redirect.
</P>
<H4>
<A NAME="7.2.1.3">
7.2.1.3. Status
</A>
</H4>
<P>
The "<SAMP>Status</SAMP>" header field is used to indicate to the server what
status code the server MUST use in the response message.
</P><!--#if expr="! $GUI" -->
<P></P><!--#endif -->
<PRE>
Status = "Status" ":" digit digit digit SP reason-phrase NL
reason-phrase = *<CHAR, excluding CTLs, NL>
</PRE>
<P>
The valid status codes are listed in section 6.1.1 of the HTTP/1.0
specifications [<A HREF="#[3]">3</A>]. If the SERVER_PROTOCOL is
"HTTP/1.1", then the status codes defined in the HTTP/1.1
specification [<A HREF="#[8]">8</A>] may
be used. If the script does not return a "<SAMP>Status</SAMP>" header
field, then "200 OK" SHOULD be assumed by the server.
</P>
<P>
If a script is being used to handle a particular error or condition
encountered by the server, such as a '404 Not Found' error, the script
SHOULD use the "<SAMP>Status</SAMP>" CGI header field to propagate the error
condition back to the client. <EM>E.g.</EM>, in the example mentioned it
SHOULD include a "Status: 404 Not Found" in the
header data returned to the server.
</P>
<H4>
<A NAME="7.2.1.4">
7.2.1.4. Extension header fields
</A>
</H4>
<P>
Scripts MAY include in their CGI response header additional fields
not defined in this or the HTTP specification.
These are called "extension" fields,
and have the syntax of a <SAMP>generic-field</SAMP> as defined in
<A HREF="#7.2.1">section 7.2.1</A>. The name of an extension field
MUST NOT conflict with a field name defined in this or any other
specification; extension field names SHOULD begin with "X-CGI-"
to ensure uniqueness.
</P>
<H4>
<A NAME="7.2.2">
7.2.2. HTTP header fields
</A>
</H4>
<P>
The script MAY return any other header fields defined by the
specification
for the SERVER_PROTOCOL (HTTP/1.0 [<A HREF="#[3]">3</A>] or HTTP/1.1
[<A HREF="#[8]">8</A>]).
Servers MUST resolve conflicts beteen CGI header
and HTTP header formats or names (see <A HREF="#8.0">section 8</A>).
</P>
<H2>
<A NAME="8.0">
8. Server Implementation
</A>
</H2>
<P>
This section defines the requirements that must be met by HTTP
servers in order to provide a coherent and correct CGI/1.1
environment in which scripts may function. It is intended
primarily for server implementors, but it is useful for
script authors to be familiar with the information as well.
</P>
<H3>
<A NAME="8.1">
8.1. Requirements for Servers
</A>
</H3>
<P>
In order to be considered CGI/1.1-compliant, a server must meet
certain basic criteria and provide certain minimal functionality.
The details of these requirements are described in the following sections.
</P>
<H3>
<A NAME="8.1.1">
8.1.1. Script-URI
</A>
</H3>
<P>
Servers MUST support the standard mechanism (described below) which
allows
script authors to determine
what URL to use in documents
which reference the script;
specifically, what URL to use in order to
achieve particular settings of the
metavariables. This
mechanism is as follows:
</P>
<P>
The server
MUST translate the header data from the CGI header field syntax to
the HTTP
header field syntax if these differ. For example, the character
sequence for
newline (such as Unix's ASCII NL) used by CGI scripts may not be the
same as that used by HTTP (ASCII CR followed by LF). The server MUST
also resolve any conflicts between header fields returned by the script
and header fields that it would otherwise send itself.
</P>
<H3>
<A NAME="8.1.2">
8.1.2. Request Message-body Handling
</A>
</H3>
<P>
These are the requirements for server handling of message-bodies directed
to CGI/1.1 resources:
</P>
<OL>
<LI>The message-body the server provides to the CGI script MUST
have any transfer encodings removed.
</LI>
<LI>The server MUST derive and provide a value for the CONTENT_LENGTH
metavariable that reflects the length of the message-body after any
transfer decoding.
</LI>
<LI>The server MUST leave intact any content-encodings of the message-body.
</LI>
</OL>
<H3>
<A NAME="8.1.3">
8.1.3. Required Metavariables
</A>
</H3>
<P>
Servers MUST provide scripts with certain information and
metavariables
as described in <A HREF="#8.3">section 8.3</A>.
</P>
<H3>
<A NAME="8.1.4">
8.1.4. Response Compliance
</A>
</H3>
<P>
Servers MUST ensure that responses sent to the user-agent meet all
requirements of the protocol level in effect. This may involve
modifying, deleting, or augmenting any header
fields and/or message-body supplied by the script.
</P>
<H3>
<A NAME="8.2">
8.2. Recommendations for Servers
</A>
</H3>
<P>
Servers SHOULD provide the "<SAMP>query</SAMP>" component of the script-URI
as command-line arguments to scripts if it does not
contain any unencoded '=' characters and the command-line arguments can
be generated in an unambiguous manner.
(See <A HREF="#5.0">section 5</A>.)
</P>
<P>
Servers SHOULD set the AUTH_TYPE
metavariable to the value of the
'<SAMP>auth-scheme</SAMP>' token of the "<SAMP>Authorization</SAMP>"
field if it was supplied as part of the request header.
(See <A HREF="#6.1.1">section 6.1.1</A>.)
</P>
<P>
Where applicable, servers SHOULD set the current working directory
to the directory in which the script is located before invoking
it.
</P>
<P>
Servers MAY reject with error '404 Not Found'
any requests that would result in
an encoded "/" being decoded into PATH_INFO or SCRIPT_NAME, as this
might represent a loss of information to the script.
</P>
<P>
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 define its behaviour for the
following cases:
</P>
<OL>
<LI>define any restrictions on allowed characters, in particular
whether ASCII NUL is permitted;
</LI>
<LI>define any restrictions on allowed path segments, in particular
whether non-terminal NULL segments are permitted;
</LI>
<LI>define the behaviour for <SAMP>"."</SAMP> or <SAMP>".."</SAMP> path
segments; <EM>i.e.</EM>, whether they are prohibited, treated as
ordinary path
segments or interpreted in accordance with the relative URL
specification [<A HREF="#[7]">7</A>];
</LI>
<LI>define any limits of the implementation, including limits on path or
search string lengths, and limits on the volume of header data the server
will parse.
</LI><!-- ##### Move the field resolution/translation para below here -->
</OL>
<P>
Servers MAY generate the
Script-URI in
any way from the client URI,
or from any other data (but the behaviour SHOULD be documented).
</P>
<P>
For non-parsed header (NPH) scripts (see
<A HREF="#7.1">section 7.1</A>), servers SHOULD
attempt to ensure that the script input comes directly from the
client, with minimal buffering. For all scripts the data will be
as supplied by the client.
</P>
<H3>
<A NAME="8.3">
8.3. Summary of
MetaVariables
</A>
</H3>
<P>
Servers MUST provide the following
metavariables to
scripts. See the individual descriptions for exceptions and semantics.
</P><!--#if expr="! $GUI" -->
<P></P><!--#endif -->
<PRE>
CONTENT_LENGTH (section <A HREF="#6.1.2">6.1.2</A>)
CONTENT_TYPE (section <A HREF="#6.1.3">6.1.3</A>)
GATEWAY_INTERFACE (section <A HREF="#6.1.4">6.1.4</A>)
PATH_INFO (section <A HREF="#6.1.6">6.1.6</A>)
QUERY_STRING (section <A HREF="#6.1.8">6.1.8</A>)
REMOTE_ADDR (section <A HREF="#6.1.9">6.1.9</A>)
REQUEST_METHOD (section <A HREF="#6.1.13">6.1.13</A>)
SCRIPT_NAME (section <A HREF="#6.1.14">6.1.14</A>)
SERVER_NAME (section <A HREF="#6.1.15">6.1.15</A>)
SERVER_PORT (section <A HREF="#6.1.16">6.1.16</A>)
SERVER_PROTOCOL (section <A HREF="#6.1.17">6.1.17</A>)
SERVER_SOFTWARE (section <A HREF="#6.1.18">6.1.18</A>)
</PRE>
<P>
Servers SHOULD define the following
metavariables for scripts.
See the individual descriptions for exceptions and semantics.
</P><!--#if expr="! $GUI" -->
<P></P><!--#endif -->
<PRE>
AUTH_TYPE (section <A HREF="#6.1.1">6.1.1</A>)
REMOTE_HOST (section <A HREF="#6.1.10">6.1.10</A>)
</PRE>
<P>
In addition, servers SHOULD provide
metavariables for all fields present
in the HTTP request header, with the exception of those involved with
access control. Servers MAY at their discretion provide
metavariables
for access control fields.
</P>
<P>
Servers MAY define the following
metavariables. See the individual
descriptions for exceptions and semantics.
</P><!--#if expr="! $GUI" -->
<P></P><!--#endif -->
<PRE>
PATH_TRANSLATED (section <A HREF="#6.1.7">6.1.7</A>)
REMOTE_IDENT (section <A HREF="#6.1.11">6.1.11</A>)
REMOTE_USER (section <A HREF="#6.1.12">6.1.12</A>)
</PRE>
<P>
Servers MAY
at their discretion define additional implementation-specific
extension metavariables
provided their names do not
conflict with defined header field names. Implementation-specific
metavariable names SHOULD
be prefixed with "X_" (<EM>e.g.</EM>,
"X_DBA") to avoid the potential for such conflicts.
</P>
<H2>
<A NAME="9.0">
9.
Script Implementation
</A>
</H2>
<P>
This section defines the requirements and recommendations for scripts
that are intended to function in a CGI/1.1 environment. It is intended
primarily as a reference for script authors, but server implementors
should be familiar with these issues as well.
</P>
<H3>
<A NAME="9.1">
9.1. Requirements for Scripts
</A>
</H3>
<P>
Scripts using the parsed-header method to communicate with servers
MUST supply a response header to the server.
(See <A HREF="#7.0">section 7</A>.)
</P>
<P>
Scripts using the NPH method to communicate with servers MUST
provide complete HTTP responses, and MUST use the value of the
SERVER_PROTOCOL metavariable
to determine the appropriate format.
(See <A HREF="#7.1">section 7.1</A>.)
</P>
<P>
Scripts MUST check the value of the REQUEST_METHOD
metavariable in order
to provide an appropriate response.
(See <A HREF="#6.1.13">section 6.1.13</A>.)
</P>
<P>
Scripts MUST be prepared to handled URL-encoded values in
metavariables.
In addition, they MUST recognise both "+" and "%20" in URL-encoded
quantities as representing the space character.
(See <A HREF="#3.1">section 3.1</A>.)
</P>
<P>
Scripts MUST ignore leading zeros in the major and minor version numbers
in the GATEWAY_INTERFACE
metavariable value. (See
<A HREF="#6.1.4">section 6.1.4</A>.)
</P>
<P>
When processing requests that include a
message-body, scripts
MUST NOT read more than CONTENT_LENGTH bytes from the input stream.
(See sections <A HREF="#6.1.2">6.1.2</A> and <A HREF="#6.2">6.2</A>.)
</P>
<H3>
<A NAME="9.2">
9.2. Recommendations for Scripts
</A>
</H3>
<P>
Servers may interrupt or terminate script execution at any time
and without warning, so scripts SHOULD be prepared to deal with
abnormal termination.
</P>
<P>
Scripts MUST
reject with
error '405 Method Not
Allowed' requests
made using methods that they do not support. 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.
</P>
<P>
If a script is processing the output of a form, it SHOULD
verify that the CONTENT_TYPE
is "<SAMP>application/x-www-form-urlencoded</SAMP>" [<A HREF="#[2]">2</A>]
or whatever other media type is expected.
</P>
<P>
Scripts parsing PATH_INFO,
PATH_TRANSLATED, or SCRIPT_NAME
SHOULD be careful
of void path segments ("<SAMP>//</SAMP>") and special path segments
(<SAMP>"."</SAMP> and
<SAMP>".."</SAMP>). They SHOULD either be removed from the path before
use in OS
system calls, or the request SHOULD be rejected with
'404 Not Found'.
</P>
<P>
As it is impossible for
scripts to determine the client URI that
initiated a
request without knowledge of the specific server in
use, the script SHOULD NOT return "<SAMP>text/html</SAMP>"
documents containing
relative URL links without including a "<SAMP><BASE></SAMP>"
tag in the document.
</P>
<P>
When returning header fields,
scripts SHOULD try to send the CGI
header fields (see section
<A HREF="#7.2">7.2</A>) as soon as possible, and
SHOULD send them
before any HTTP header fields. This may
help reduce the server's memory requirements.
</P>
<H2>
<A NAME="10.0">
10. System Specifications
</A>
</H2>
<H3>
<A NAME="10.1">
10.1. AmigaDOS
</A>
</H3>
<P>
The implementation of the CGI on an AmigaDOS operating system platform
SHOULD use environment variables as the mechanism of providing
request metadata to CGI scripts.
</P>
<DL>
<DT><STRONG>Environment variables</STRONG>
</DT>
<DD>
<P>
These are accessed by the DOS library routine <SAMP>GetVar</SAMP>. The
flags argument SHOULD be 0. Case is ignored, but upper case is
recommended for compatibility with case-sensitive systems.
</P>
</DD>
<DT><STRONG>The current working directory</STRONG>
</DT>
<DD>
<P>
The current working directory for the script is set to the directory
containing the script.
</P>
</DD>
<DT><STRONG>Character set</STRONG>
</DT>
<DD>
<P>
The US-ASCII character set is used for the definition of environment
variable names and header
field names; the newline (NL) sequence is LF;
servers SHOULD also accept CR LF as a newline.
</P>
</DD>
</DL>
<H3>
<A NAME="10.2">
10.2. Unix
</A>
</H3>
<P>
The implementation of the CGI on a UNIX operating system platform
SHOULD use environment variables as the mechanism of providing
request metadata to CGI scripts.
</P>
<P>
For Unix compatible operating systems, the following are defined:
</P>
<DL>
<DT><STRONG>Environment variables</STRONG>
</DT>
<DD>
<P>
These are accessed by the C library routine <SAMP>getenv</SAMP>.
</P>
</DD>
<DT><STRONG>The command line</STRONG>
</DT>
<DD>
<P>
This is accessed using the
<SAMP>argc</SAMP> and <SAMP>argv</SAMP>
arguments to <SAMP>main()</SAMP>. The words have any characters
that
are 'active' in the Bourne shell escaped with a backslash.
If the value of the QUERY_STRING
metavariable
contains an unencoded equals-sign '=', then the command line
SHOULD NOT be used by the script.
</P>
</DD>
<DT><STRONG>The current working directory</STRONG>
</DT>
<DD>
<P>
The current working directory for the script
SHOULD be set to the directory
containing the script.
</P>
</DD>
<DT><STRONG>Character set</STRONG>
</DT>
<DD>
<P>
The US-ASCII character set is used for the definition of environment
variable names and header field names; the newline (NL) sequence is LF;
servers SHOULD also accept CR LF as a newline.
</P>
</DD>
</DL>
<H2>
<A NAME="11.0">
11. Security Considerations
</A>
</H2>
<H3>
<A NAME="11.1">
11.1. Safe Methods
</A>
</H3>
<P>
As discussed in the security considerations of the HTTP
specifications [<A HREF="#[3]">3</A>,<A HREF="#[8]">8</A>], the
convention has been established that the
GET and HEAD methods should be 'safe'; they should cause no
side-effects and only have the significance of resource retrieval.
</P>
<P>
CGI scripts are responsible for enforcing any HTTP security considerations
[<A HREF="#[3]">3</A>,<A HREF="#[8]">8</A>]
with respect to the protocol version level of the request and
any side effects generated by the scripts on behalf of
the server. Primary
among these
are the considerations of safe and idempotent methods. Idempotent
requests are those that may be repeated an arbitrary number of times
and produce side effects identical to a single request.
</P>
<H3>
<A NAME="11.2">
11.2. HTTP Header
Fields Containing Sensitive Information
</A>
</H3>
<P>
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 using the
"<SAMP>Basic</SAMP>"
authentication scheme, then the client will send an
"<SAMP>Authorization</SAMP>"
header field containing a username and password. If the server, rather
than the script, validates this information then the password SHOULD
NOT be passed on to the script <EM>via</EM> the HTTP_AUTHORIZATION
metavariable
without careful consideration.
This also applies to the
Proxy-Authorization header field and the corresponding
HTTP_PROXY_AUTHORIZATION
metavariable.
</P>
<H3>
<A NAME="11.3">
11.3. Script
Interference with the Server
</A>
</H3>
<P>
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, or documents.
</P>
<P>
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.
</P>
<H3>
<A NAME="11.4">
11.4. Data Length and Buffering Considerations
</A>
</H3>
<P>
This specification places no limits on the length of message-bodies
presented to the script. Scripts 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.
Scripts 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 Long' (HTTP/1.1).
</P>
<H3>
<A NAME="11.5">
11.5. Stateless Processing
</A>
</H3>
<P>
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.
</P>
<P>
Authors of scripts involved in multi-request transactions should be
particularly cautios 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 (<EM>e.g.</EM>, hidden
HTML form elements, cookies, embedded URLs, <EM>etc.</EM>).
</P>
<H2>
<A NAME="12.0">
12. Acknowledgements
</A>
</H2>
<P>
This work is based on a draft published in 1997 by David R. Robinson,
which in turn was based on the original CGI interface that arose out of
discussions on the <EM>www-talk</EM> 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.
</P>
<P>
This document has also greatly benefited from the comments and
suggestions made by Chris Adie, Dave Kristol,
Mike Meyer, David Morris, Jeremy Madea,
Patrick M<SUP>c</SUP>Manus, Adam Donahue,
Ross Patterson, and Harald Alvestrand.
</P>
<H2>
<A NAME="13.0">
13. References
</A>
</H2>
<DL COMPACT>
<DT><A NAME="[1]">[1]</A>
</DT>
<DD>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,
CERN, June 1994.
<P>
</P>
</DD>
<DT><A NAME="[2]">[2]</A>
</DT>
<DD>Berners-Lee, T. and Connolly, D., 'Hypertext Markup Language -
2.0', RFC 1866, MIT/W3C, November 1995.
<P>
</P>
</DD>
<DT><A NAME="[3]">[3]</A>
</DT>
<DD>Berners-Lee, T., Fielding, R. T. and Frystyk, H.,
'Hypertext Transfer Protocol -- HTTP/1.0', RFC 1945, MIT/LCS,
UC Irvine, May 1996.
<P>
</P>
</DD>
<DT><A NAME="[4]">[4]</A>
</DT>
<DD>Berners-Lee, T., Fielding, R., and Masinter, L., Editors,
'Uniform Resource Identifiers (URI): Generic Syntax', RFC 2396,
MIT, U.C. Irvine, Xerox Corporation, August 1996.
<P>
</P>
</DD>
<DT><A NAME="[5]">[5]</A>
</DT>
<DD>Braden, R., Editor, 'Requirements for Internet Hosts --
Application and Support', STD 3, RFC 1123, IETF, October 1989.
<P>
</P>
</DD>
<DT><A NAME="[6]">[6]</A>
</DT>
<DD>Crocker, D.H., 'Standard for the Format of ARPA Internet Text
Messages', STD 11, RFC 822, University of Delaware, August 1982.
<P>
</P>
</DD>
<DT><A NAME="[7]">[7]</A>
</DT>
<DD>Fielding, R., 'Relative Uniform Resource Locators', RFC 1808,
UC Irvine, June 1995.
<P>
</P>
</DD>
<DT><A NAME="[8]">[8]</A>
</DT>
<DD>Fielding, R., Gettys, J., Mogul, J., Frystyk, H. and
Berners-Lee, T., 'Hypertext Transfer Protocol -- HTTP/1.1',
RFC 2068, UC Irvine, DEC,
MIT/LCS, January 1997.
<P>
</P>
</DD>
<DT><A NAME="[9]">[9]</A>
</DT>
<DD>Freed, N. and Borenstein N., 'Multipurpose Internet Mail
Extensions (MIME) Part Two: Media Types', RFC 2046, Innosoft,
First Virtual, November 1996.
<P>
</P>
</DD>
<DT><A NAME="[10]">[10]</A>
</DT>
<DD>Mockapetris, P., 'Domain Names - Concepts and Facilities',
STD 13, RFC 1034, ISI, November 1987.
<P>
</P>
</DD>
<DT><A NAME="[11]">[11]</A>
</DT>
<DD>St. Johns, M., 'Identification Protocol', RFC 1431, US
Department of Defense, February 1993.
<P>
</P>
</DD>
<DT><A NAME="[12]">[12]</A>
</DT>
<DD>'Coded Character Set -- 7-bit American Standard Code for
Information Interchange', ANSI X3.4-1986.
<P>
</P>
</DD>
<DT><A NAME="[13]">[13]</A>
</DT>
<DD>Hinden, R. and Deering, S.,
'IP Version 6 Addressing Architecture', RFC 2373,
Nokia, Cisco Systems,
July 1998.
<P>
</P>
</DD>
</DL>
<H2>
<A NAME="14.0">
14. Authors' Addresses
</A>
</H2>
<ADDRESS>
<P>
Ken A L Coar
<BR>
MeepZor Consulting
<BR>
7824 Mayfaire Crest Lane, Suite 202
<BR>
Raleigh, NC 27615-4875
<BR>
U.S.A.
</P>
<P>
Tel: +1 (919) 254.4237
<BR>
Fax: +1 (919) 254.5250
<BR>
Email:
<A
HREF="mailto:Ken.Coar@Golux.Com"
><SAMP>Ken.Coar@Golux.Com</SAMP></A>
</P>
</ADDRESS>
<ADDRESS>
<P>
David Robinson
<BR>
E*TRADE UK Ltd
<BR>
Mount Pleasant House
<BR>
2 Mount Pleasant
<BR>
Huntingdon Road
<BR>
Cambridge CB3 0RN
<BR>
UK
</P>
<P>
Tel: +44 (1223) 566926
<BR>
Fax: +44 (1223) 506288
<BR>
Email:
<A
HREF="mailto:drtr@etrade.co.uk"
><SAMP>drtr@etrade.co.uk</SAMP></A>
</ADDRESS>
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