Working on Login functions, wrestling with JavaScript
[CGIscriptor.git] / CGIservlet.pl
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1 #! /usr/bin/perl
3 # Put the full path to perl on the first line, run the program with
4 # `perl CGIservlet`, or put a symbolic link to perl in
5 # the startup directory if you need a special version of perl.
7 if(grep(/\-\-help/i, @ARGV))
9 print << 'ENDOFHELPTEXT';
10 # CGIservlet:
11 # A HTTPd "connector" for running CGI scripts on unix systems as WWW
12 # accessible Web sites. The servlet starts a true HTTP daemon that channels
13 # HTTP requests to forked daughter processes. CGIservlet.pl is NOT a
14 # full fledged server. Moreover, this servlet is definitely NOT intended
15 # as a replacement of a real server (e.g., Apache). It's design goal was
16 # SIMPLICITY, and not mileage.
18 # Note that a HTTP server can be accessed on your local machine WITHOUT
19 # internet access (but WITH a DNS?):
20 # use "http://localhost[:port]/[path]" or "http://127.0.0.1[:port]/[path]"
21 # as the URL. It is also easy to restrict access to the servlet to localhost
22 # users (i.e., the computer running the servlet).
24 # Suggested uses:
25 # - A testbed for CGI-scripts and document-trees outside the primary server.
26 # When developing new scripts and services, you don't want to mess up your
27 # current Web-site. CGIservlet is an easy way to start a temporary (private)
28 # server. CGIservlet allows to test separate HTTP server components, e.g.,
29 # user authentication, in isolation.
31 # - A special purpose temporary server (WWW everywhere/anytime).
32 # We run identification and other experiments over the inter-/intra-net using
33 # CGI-scripts. This means a lot of development and changes and only little
34 # actual run-time. The people doing this do not want "scripting" access to our
35 # departmental server with all its restrictions and security. So we need a
36 # small, lightweigth, easy-to-configure server that can be run by each
37 # investigator on her own account (and risk).
39 # - Interactive WWW presentations.
40 # Not everyone is content with the features of "standard" office presentation
41 # software. HTML and its associated browsers are an alternative (especially
42 # under Linux). However, you need a server to realize the full interactive
43 # nature of the WWW. CGIservlet with the necessary scripts can be run from
44 # a floppie (a Web server in 100 kB). The CGIservlet can actually run a
45 # (small) web site from RAM, without disk access (if you DO NOT use the
46 # 2>pid.log redirection on startup).
47 # With the "localhost" or "127.0.0.1" id in your browser you can use the
48 # servlet standalone.
50 # When the servlet is started with the -r option, only requests from "localhost"
51 # or "127.0.0.1" are accepted (default) or from addresses indicated after the
52 # -r switch.
54 # Running demo's and more information can be found at
55 # http://www.fon.hum.uva.nl/rob/OSS/OSS.html
58 ############################################################################
60 # Changes (document ALL changes with date, name and email here):
62 # 29 May 2012 - Added .log -> / to @RegAliasTranslation, blocks attempts to read
63 # log files.
64 # 22 May 2012 - Blocked "hidden" files and directories starting with "." in
65 # default @RegAliasTranslation. Removed obsolete CVS reference.
66 # 21 May 2012 - Inserted the -m[emory] switch for loading and serving from RAM.
67 # The option was mentioned in the manual, but the cli switch was
68 # never added.
69 # 22 Jul 2003 - Plain output using binary print io. `cat ...`
70 # 22 Jul 2003 - Added 'use CGI::Carp qw(fatalsToBrowser);' line
71 # for debugging. Standard this is commented out
72 # for security reasons (suggested by Jochen_Hayek@ACM.org).
73 # 22 Jul 2003 - Added error checking to doarg (suggested by Jochen_Hayek@ACM.org)
74 # 22 Jul 2003 - Removed SERVER_PORT from HTTP_HOST (Bug found by Jochen_Hayek@ACM.org)
75 # 22 Jul 2003 - Updated documentation. Added CGIservlet directory
76 # to the search path of CGIservletSETUP.pl
77 # 20 May 2003 - Made sure recycled (double) pid's do not mess up the
78 # @brood list and added a --help switch.
79 # 20 May 2003 - Added a maximum running time for child processes
80 # with command line switch -xterm.
81 # 15 Jan 2002 - Version 1.3
82 # 19 Oct 2001 - Included browsing of directories and a new -s
83 # security switch. With security toggled of
84 # directories can be browsed and all mime-types
85 # are served, either as 'text/plain' or as
86 # 'application/octed-stream'.
87 # 18 May 2001 - Added some HTTP header lines.
88 # 13 Jun 2000 - Included the possibility to add POST request
89 # to GET query-strings (and change the request
90 # method). The -l ($Maxlength) maximum length
91 # option now covers POST requests too.
92 # 8 Dec 1999 - Included hooks for compression when running from RAM.
93 # 2 Dec 1999 - Autoflush enabled.
94 # 2 Dec 1999 - Allow running a Web Site from RAM.
95 # 2 Dec 1999 - Changed the behavior of CGIservletSETUP. CGIservlet
96 # will eval ALL setup files, the one in the CGIscriptor
97 # subdirectory (if any) AND the one in the current
98 # directory. (also added a close(SETUP) command)
99 # 26 Nov 1999 - Added some minimal security for 'automatic', out of
100 # the box installation.
101 # 26 Nov 1999 - Made the text/osshell mime-type functional (i.e.,
102 # without any scripts, implement a dynamic web server)
103 # Linited to '.cgi' extension.
104 # 26 Nov 1999 - Added aliasing of URL paths, both one-to-one lookups
105 # and full regular expression, i.e., $Path =~ s/.../.../g
106 # replace commands
107 # 28 Sep 1999 - Made all client supplied HTTP parameter names lowercase
108 # to handle inconsistencies in case use.
109 # 29 Jul 1999 - Allowed for a SETUP configuration file 'CGIservletSETUP.pl'.
110 # Use $beginarg from the 'CGIscriptor/' directory if it exists.
111 # (R.J.J.H.vanSon@uva.nl)
114 ############################################################################
116 # Known bugs
118 # 23 Mar 2000 - An odd server side network error is reported by Netscape
119 # when a Post is initiated from a Javascript Submit of a
120 # <FORM>. This was found on Red Hat 6.1 Linux with perl 5.00503,
121 # 5.00503 and 5.6.0. But not on IRIX or Red Hat 5.0, 7.x.
123 ############################################################################
126 # Inner workings:
127 # Whenever an HTTP request is received, the specified CGI script is
128 # started inside a child process as if it was inside a real server (e.g.,
129 # Apache). The evironment variables are set more or less as in Apache.
130 # Note that CGIservlet only uses a SINGLE script for ALL requests.
131 # No attemps for security are made, it is the script's responsibility to
132 # check access rights and the validity of the request.
133 # When no scripts are given, CGIservlet runs as a bare bone WWW server
134 # configurable to execute scripts (the default setting is as a
135 # STATIC server).
137 # Author and copyright (c) :
138 # Rob van Son
139 # email:
140 # R.J.J.H.vanSon@gmail.com
141 # r.v.son@nki.nl
142 # NKI/AVL Amsterdam
144 # copying freely from the mhttpd server by Jerry LeVan (levan@eagle.eku.edu)
145 # Date: July 22, 2012
146 # Version:1.301
147 # Env: Perl 5.002 and later
150 ################################################################################
152 # LICENSE #
154 # This program is free software; you can redistribute it and/or #
155 # modify it under the terms of the GNU General Public License #
156 # as published by the Free Software Foundation; either version 2 #
157 # of the License, or (at your option) any later version. #
159 # This program is distributed in the hope that it will be useful, #
160 # but WITHOUT ANY WARRANTY; without even the implied warranty of #
161 # MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the #
162 # GNU General Public License for more details. #
164 # You should have received a copy of the GNU General Public License #
165 # along with this program; if not, write to the Free Software #
166 # Foundation, Inc., 59 Temple Place - Suite 330, #
167 # Boston, MA 02111-1307, USA. #
169 ################################################################################
171 # Note: CGIservlet.pl was directly inspired by Jerry LeVan's
172 # (levan@eagle.eku.edu) simple mhttpd server which again was
173 # inspired by work of others. CGIservlet is used as a bare bones
174 # socket server for a single CGI script at a time.
176 # Use: CGIservlet.pl -<switch> <argument> 2>pid.log & (sh/bash)
177 # CGIservlet.pl -<switch> <argument> >&pid.log & (csh)
179 # The servlet prints out pid and port number on STDERR. It is
180 # adviced to store these in a separate file (this will become the
181 # error log).
182 # NOTE: When running CGIservlet from a Memmory Image (i.e. RAM),
183 # do NOT redirect the error output to a file, but use something
184 # like MAILTO or /dev/null!
186 # Stop: sh pid.log (kills the server process)
188 # The first line in the file that receives STDERR output is a command
189 # to stop CGIservlet.
191 # examples:
192 # CGIservlet.pl -p 2345 -d /cgi-bin/CGIscriptor.pl -t /WWW 2>pid.log &
193 # CGIservlet.pl -p 8080 -b 'require "CGIscriptor.pl";' -t $PWD -e \
194 # 'Handle_Request();' 2>pid.log &
196 # The following example settings implement a static WWW server using 'cat'
197 # (and prohibiting Queries):
198 # -p 8008
199 # -t `pwd`
200 # -b ''
201 # -e
202 # '$ENV{QUERY_STRING}="";$ENV{PATH_INFO}=~/\.([\w]+)$/; "Content-type: ".$mimeType{uc($1)}."\n\n";'
203 # -d 'cat -u -s'
204 # -w '/index.html'
205 # -c 32
206 # -l 512
208 # This is identical to the (static) behaviour of CGIservlet when
209 # -e '' -d '' -x '' is used.
210 # The CGIservlet command should be run from the intended server-root directory.
212 # Another setting will use a package 'CGIscriptor.pl' with a function
213 # 'HandleRequest()' to implement an interactive WWW server with inline
214 # Perl scripting:
215 # -p 8080
216 # -t `pwd`
217 # -b 'require "CGIscriptor.pl";'
218 # -e 'HandleRequest();'
219 # -d ''
220 # -w '/index.html'
221 # -c 32
222 # -l 32767
224 # Look below or in the CGIservletSETUP.pl file for the current default
225 # settings.
228 # ###############################################################################
230 # There are many switches to tailor the workings of CGIservlet.pl.
231 # Some are fairly esoteric and you should only look for them if you
232 # need something special urgently. When building a Web site,
233 # the specific options you need will "suggest" themselves (e.g., port
234 # number, script, or server-root directory). Most default settings
235 # should work fine.
237 # You can add your own configuration in a file called
238 # 'CGIservletSETUP.pl'. This file will be executed ("eval"-ed)
239 # after the default setup, but before the command line options take
240 # effect. CGIservlet looks for the SETUP file in the startup directory
241 # and in the CGIscriptor subdirectory.
242 # (Note that the $beginarg variable is evaluated AFTER the setup file).
244 # In any case, it is best to change the default settings instead of
245 # using the option switches. All defaults are put in a single block.
247 # switches and arguments:
248 # Realy important
249 # -p[ort] port number
250 # For example -p 2345
251 # Obviously the port CGIservlet listenes to. Suggested Default: -p 8008
253 # -a[lias] Alias1 RealURL1 ...
254 # For example -a '/Stimulus.aifc' '/catAIFC.xmr'
255 # Replaces the given Alias URL path by its real URL path. Accepts full
256 # regular expressions too (identified by NON-URL characters).
257 # That is, on each request it performs (in order):
258 # if($AliasTranslation{$Path})
259 # {
260 # $Path = $AliasTranslation{$Path};
262 # elsif(@RegAliasTranslation)
263 # {
264 # my $i;
265 # for($i=0; $i<scalar(@RegAliasTranslation); ++$i)
266 # {
267 # my $Alias = $RegAliasTranslation[$i];
268 # my $RealURL = $RegURLTranslation[$i];
269 # last if ($Path =~ s#$Alias#$RealURL#g);
270 # };
271 # };
272 # The effects can be quite drastic, so be
273 # carefull. Note also, that entering many Regular Expression
274 # aliases could slow down your servlet. Checking stops after
275 # the first match.
276 # Full regular expression alias translations are done in the
277 # order given! They are recognized as Aliases containing
278 # regexp's (i.e., non-URL) operator characters like '^' and
279 # '$'.
280 # Note: The command line is NOT a good place for entering
281 # Aliases, change the code below or add aliases to
282 # CGIservletSETUP.pl.
284 # --help
285 # Prints the manual
287 # Script related
288 # -b[egin] perl commands
289 # For example -b 'require "CGIscriptor.pl";' or
290 # 'require "/WWW/cgi-bin/XMLelement.pl";'
291 # Perl commands evaluated at server startup
293 # -d[o] perl script file
294 # For example -d '/WWW/cgi-bin/CGIscriptor.pl'
295 # The actual CGI-script started as a perl {do "scriptfile"} command.
296 # The PATH_INFO and the QUERY are pushed on @ARGV.
298 # -x shell command
299 # -qx shell command
300 # -exec shell command
301 # OS shell script or command, e.g., -x 'CGIscriptor.pl' or
302 # -x '/WWW/cgi-bin/my-script'
303 # The actual CGI-script started as `my-script \'$Path\' \'$QueryString\'`.
304 # -qx and -exec[ute] are aliases of -x. For security reasons, Paths or
305 # queries containing '-quotes are rejected.
307 # -e[val] perl commands
308 # For example -e 'Handle_Request();'
309 # The argument is evaluated as perl code. The actual CGI-script
310 # can be loaded once with -b 'require module.pm' and you only have to
311 # call the central function(s).
313 # WWW-tree related
314 # -t[extroot] path
315 # For example -t "$PWD" or -t "/WWW/documents"
316 # The root of the server hierachy. Defaults to the working directory
317 # at startup time (`pwd`)
319 # -w[elcome] filepath
320 # For example -w "/index.html" (default)
321 # The default welcome page used when no path is entered. Note that
322 # this path can point to anything (or nothing real at all).
324 # Security related
325 # The following arguments supply some rudimentary security. It is the
326 # responsibility of the script to ensure that the requests are indeed
327 # "legal".
329 # -c[hildren] maximum child processes
330 # For example -c 32
331 # The maximum number of subprocesses started. If there are more requests,
332 # the oldest requests are "killed". This should take care of "zombie"
333 # processes and server overloading. Note that new requests will be
334 # serviced irrespective of the success of killing it's older siblings.
336 # -xtime maximum running time of a child
337 # For example -xtime 36000
338 # The maximum time a child may run in seconds. After a new request has
339 # been servised, all children that have run for longer than this time
340 # will be killed. This stops runaway processes, often connected to
341 # web-crawlers.
343 # -l[ength] maximum length of HTTP request in bytes
344 # For example -l 32768
345 # This prevents overloading the server with enormous queries. Reading of
346 # requests simply stops when this limit is reached. This DOES affect
347 # POST requests. If the combined length of the COMPLETE HTTP request,
348 # including headers, exceeds this limit, the whole request is dropped.
350 # -r[estrict] [Remote-address [Remote-host]]
351 # For example -r 127.0.0.1 (default of -r)
352 # A space separated list of client IP addresses and/or domain names that
353 # should be serviced. Default, i.e., '-r' without any addresses or domain
354 # names, is the localhost IP address '127.0.0.1'.
355 # When using CGIservlet for local purposes only (e.g., development or a
356 # presentation), it would be unsafe to allow others to access the servlet.
357 # If -r is used (or the corresponding @RemoteAddr or @RemoteHost lists are
358 # filled in the code below), all requests from clients whose Remote-address
359 # or Remote-host do not match the indicated addresses will be rejected.
360 # Partial addresses and domain names are allowed. Matching is done according
361 # to Remote-addr =~ /^\Q$pattern\E/ (front to back) and
362 # Remote-host =~ /\Q$pattern\E$/ (back to front)
364 # -s[ecure]
365 # No arguments.
366 # A toggle switch that blocks all access to files with undefined
367 # mime-types (or to serve ascii files as "text/plain"), and blocking directory
368 # browsing. Defaults to blocking what is not explicitely allowed.
370 # -m[emory]
371 # No arguments.
372 # Reads complete Web site into memory and runs from this image.
373 # Set $UseRAMimage = 1; to activate memory-only running.
374 # Under certain circumstance, this can improve security.
375 # Note, however, that running osshellscripts from this image
376 # makes any "security" related claims very shaky.
378 # Speedup
379 # -n[oname]
380 # No arguments.
381 # Retrieving the domain name of the Client (i.e., Remote-host) is a
382 # very slow process and normally useless. To skip it, enter this
383 # option. Note that you cannot use '-r Remote-host' anymore after
384 # you enter -n, only IP addresses will work.
386 # Configuration with the CGIservletSETUP.pl file
388 # You can add your own configuration in a file
389 # called 'CGIservletSETUP.pl'. This file will be executed ("eval"-ed)
390 # after the default setup, but before the command line options take
391 # effect. CGIservlet looks for the SETUP file in the startup directory
392 # and in the CGIservlet and CGIscriptor subdirectories.
393 # (Note that the $beginarg variable is evaluated even later).
395 # Changing POST to GET requests
397 # CGIservlet normally only handles requests with the GET method. Processing
398 # the input from POST requests is left to the reading application. POST
399 # requests add some extra complexity to processing requests. Sometimes,
400 # the reading application doesn't handle POST requests. CGIservlet
401 # already has to manage the HTTP request. Therefore, it can easily
402 # handle the POST request. If the variable $POSTtoGET is set to any
403 # non-false value, the content of whole POST request is added to the
404 # QUERY_STRING environment variable (preceeded by a '&' if necessary).
405 # The content-length is set to 0. If $POSTtoGET equals 'GET', the method
406 # will also be changed to 'GET'.
408 # remarks:
409 # All of the arguments of -d, -e, and -x are processed sequentially
410 # in this order. This might not be what you want so you should be
411 # carefull when using multiple executable arguments.
412 # If none of the executable arguments is DEFINED (i.e., they are entered
413 # as -d '' -e '' -x ''), each request is treated as a simple
414 # text-retrieval. THIS CAN BE A SECURITY RISK!
416 # The wiring of an interactive web-server, which also calls shell
417 # scripts with the extension '.cgi', is in place. You can
418 # "activate" it by changing the "my $ExecuteOSshell = 0;" line to
419 # "my $ExecuteOSshell = 1;".
420 # If you have trouble doing this, it might be a good idea
421 # to reconsider using a dynamic web server. Executing shell
422 # scripts inside a web server is a rather dangerous practise.
424 # CGIservlet can run its "standard" web server from memory.
425 # At startup, all files are read into a hash table. Upon
426 # request, the contents of the file are placed in the
427 # environment variable: CGI_FILE_CONTENTS.
428 # No further disk access is necessary. This means that:
429 # 1 CGIservlet can run a WWW site from a removable disk,
430 # e.g., a floppy
431 # 2 The web servlet can run without any read or write privilege.
432 # 3 The integrity of the Web-site contents can be secured at the
433 # level you want
435 # To compres the memory (RAM) immage, you should hook the
436 # compression function to
437 # $CompressRAMimage = sub { return shift;};
438 # and the decompression function to
439 # $DecompressRAMimage = sub { return shift;};
442 ENDOFHELPTEXT
443 exit;
445 ###################################################################################
447 require 5.002;
448 use strict; # Should realy be used!
449 use Socket;
450 use Carp; # could come in handy (can be missed, I think)
452 # For debugging: uncommenting the use-line below will send
453 # nicely formanted output to the client. However, it is
454 # generally not a good idea to enable clients to test your
455 # scripts and look for holes (SECURITY).
456 # use CGI::Carp qw(fatalsToBrowser);
458 $| = 1; # Autoflush (i'm not sure whether this is usefull)
460 my $version = "1.301";
461 my $program = "CGIservlet.pl";
463 ##################################################################
465 # print some information to STDERR, e.g., the process number #
467 ##################################################################
468 sub logmsg { print STDERR "kill -KILL $$;exit;\n", # Stop CGIservlet
469 "$0 $$: @_ at ", scalar localtime, "\n" }
471 ############################################################
473 # Parse arguments (you can define DEFAULT VALUES here) #
475 ############################################################
477 my $port = 8008; # The port number
479 # Add POST requests to the QUERY_STRING, change method to
480 # GET if the value is 'GET'
481 my $POSTtoGET = 0; # Add POST requests to the query string
483 # (Fast) direct translation of full URL paths
484 my %AliasTranslation = (); # Alias => RealURL pairs (ONLY paths)
485 # Regular expression alias translation, in order of application
486 # (this can be quite slow)
487 my @RegAliasTranslation = ('^(\..*|.*/\..*)$','\.htm$', '^.*\.log$'); # Full regular expression alias/url pairs: URL
488 my @RegURLTranslation = ('/','.html', '/'); # Full regular expression alias/url pairs: PATH
490 my $textroot = $ENV{'PWD'} || `pwd`; # current working directory
491 chomp($textroot); # Remove nasty newline, if present
492 my $doarg = ''; # do "filename",
494 my $beginarg = ''; # eval($Argument) at the start of the program
495 my $evalarg = ''; # eval($Argument) for each request
496 my $execarg = ''; # execute `command \'$textroot$Path\' \'$QueryString\'`
498 my $welcome = '/index.html'; # Default path
500 # Rudimentary security, overflow detection
501 my $MaxBrood = 32; # Maximum number of running children
502 my $MaxTime = 36000; # Maximum time a child may run in seconds
503 my $MaxLength = 2**15; # Maximum Request Length
504 my $Secure = 1; # Block browsing directories and text files or not
506 # If one of the following lists contains any client addresses or names, all others are
507 # blocked (be carefull, your site will be inaccessible if you misspell them).
508 my @RemoteHost = (); # Accepted Hosts, suggest: localhost
509 my @RemoteAddr = (); # Accepted IP addresses, suggest: @RemoteAddr=('127.0.0.1')
510 my $DefaultRemoteAddr = '127.0.0.1'; # default, use localhost IP address
511 my $NONAME = 0; # if 1, do NOT ask for REMOTE_HOST (faster)
513 # Store the whole Web Site in a hash table and use this RAM memory image (if non-zero)
514 my $UseRAMimage = 0;
515 # Empty function handlers for data compression
516 # In general, these must be redefined in the $beginarg
517 my $CompressRAMimage = sub { return shift;};
518 my $DecompressRAMimage = sub { return shift;};
520 # Execute shell CGI scripts when no -d, -e, or -x are supplied
521 my $ExecuteOSshell = 0; # Do you REALY want this? It is dangerous
523 #################################################################
525 # Configure CGIservlet with a setup file (overides the #
526 # default settings, but not the command line options). #
527 # Note that, if it exists, the setup file in the CGIscriptor #
528 # subdirectory is processed EVEN if there is a SETUP file #
529 # in the current directory. #
531 #################################################################
532 # There exists a CGIservlet subdirectory and it contains
533 # a CGIservletSETUP.pl file
534 if((-e './CGIservlet/CGIservletSETUP.pl') &&
535 open(SETUP, '<./CGIservlet/CGIservletSETUP.pl'))
537 # Get the setup code
538 my $SetupCode = join("", <SETUP>);
539 # 'Eval' is used to ensure that the values are entered in the current
540 # package (contrary to what 'do' and 'require' do).
541 (eval $SetupCode) || die "$! $@\n";
542 close(SETUP);
544 # There exists a CGIscriptor subdirectory and it contains
545 # a CGIservletSETUP.pl file
546 if((-e './CGIscriptor/CGIservletSETUP.pl') &&
547 open(SETUP, '<./CGIscriptor/CGIservletSETUP.pl'))
549 # Get the setup code
550 my $SetupCode = join("", <SETUP>);
551 # 'Eval' is used to ensure that the values are entered in the current
552 # package (contrary to what 'do' and 'require' do).
553 (eval $SetupCode) || die "$! $@\n";
554 close(SETUP);
556 # There is a CGIservletSETUP.pl file in the current directory
557 if((-e './CGIservletSETUP.pl') &&
558 open(SETUP, '<./CGIservletSETUP.pl'))
560 # Get the setup code
561 my $SetupCode = join("", <SETUP>);
562 # 'Eval' is used to ensure that the values are entered in the current
563 # package (contrary to what 'do' and 'require' do).
564 (eval $SetupCode) || die "-e $SetupCode: $! $@\n";
565 close(SETUP);
568 ######################################
570 # process arguments and defaults #
572 ######################################
574 while ($_ = shift(@ARGV))
576 # With switches
577 if(/\-p/is) # Port
579 $port = shift(@ARGV);
581 elsif(/\-d/is) # Do
583 $doarg = shift(@ARGV);
585 elsif(/\-(x|qx|exec)/is) # Execute
587 $execarg = shift(@ARGV);
589 elsif(/\-b/is) # Begin
591 $beginarg = shift(@ARGV);
593 elsif(/\-e/is) # Evaluate
595 $evalarg = shift(@ARGV);
597 elsif(/\-t/is) # Textroot
599 $textroot = shift(@ARGV);
601 elsif(/\-w/is) # Default welcome page
603 $welcome = shift(@ARGV);
605 elsif(/\-c/is) # Maximum Children
607 $MaxBrood = shift(@ARGV) || $MaxBrood;
609 elsif(/\-xtime/is) # Maximum running time
611 $MaxTime = shift(@ARGV) || $MaxTime;
613 elsif(/\-l/is) # Maximum Length
615 $MaxLength = shift(@ARGV) || $MaxLength;
617 elsif(/\-m/is) # Run from RAM
619 $UseRAMimage = 1;
621 elsif(/\-a/is) # Aliases
623 while(@ARGV && $ARGV[0] !~ /^\-/) # while not a parameter
625 my $Alias = shift(@ARGV);
626 my $RealURL = $ARGV[0] !~ /^\-/ ? shift(@ARGV) : "";
627 next unless $Alias && $RealURL;
628 # Store the alias
629 # Simple straight translations
630 unless($Alias =~ m/[\Q^$*&@!\?(){}[];:\E]/)
632 $AliasTranslation{$Alias} = $RealURL;
634 else # Full regular expressions
636 push(@RegAliasTranslation, $Alias);
637 push(@RegURLTranslation, $RealURL);
642 elsif(/\-r/is) # Remote host or address
644 while(@ARGV && $ARGV[0] !~ /^\-/) # while not a parameter
646 my $Remote = shift(@ARGV);
647 if($Remote =~ /[\d\.]+/) # A host IP address
649 push(@RemoteAddr, $Remote);
651 else # A host domain name, less secure
653 push(@RemoteHost, $Remote);
657 # Use the default Remote Host (Client) IP address (e.g., localhost)
658 # if no addresses or domain names are entered.
659 push(@RemoteAddr, $DefaultRemoteAddr) unless @RemoteAddr || @RemoteHost;
661 elsif(/\-s/is) # Secure or not
663 $Secure = !$Secure; # Toggle blocking directory browsing and ASCII file access
665 elsif(/\-n/is) # Do NOT extract Remote host
667 $NONAME = 1;
669 else # perform unreliable magick without switches
671 if(/^[0-9]+$/ && $_ > 1024) # A (large) number must be a port
673 $port = $_;
675 elsif(-T && /\.pl$/) # Text file with extension .pl is a Perl file
677 $doarg = $_;
679 elsif(-T && /\.pm$/) # Text file with extension .pm is a Perl module file
681 $beginarg = $_;
683 elsif(-x) # Executables can be executed
685 $execarg = $_;
687 elsif(-d) # A directory can only be the root
689 $textroot = $_;
691 elsif(-T && /^\// && /\.html$/) # An html file path is the default path
693 $welcome = $_;
695 elsif(-T) # A text file is something to do
697 $doarg = $_;
699 elsif(/[\s\{\`\[\@\%]/) # I give up, just try it
701 $evalarg = shift(@ARGV);
706 ################################################
708 # All argument values are known. #
709 # Initialize environment variables. #
710 # (should be accessible to eval($beginarg)) #
712 ################################################
714 # Initialize %ENV
715 $ENV{'SERVER_SOFTWARE'} = "$program $version";
716 $ENV{'GATEWAY_INTERFACE'} = "CGI/1.1";
717 $ENV{'SERVER_PORT'} = "$port";
718 $ENV{'CGI_HOME'} = $textroot;
719 $ENV{'SERVER_ROOT'} = $textroot; # Server Root Directory
720 $ENV{'DOCUMENT_ROOT'} = $textroot; # Server Root Directory
721 $ENV{'SCRIPT_NAME'} = $doarg.$execarg.$evalarg; # Combine executable arguments
723 ################################################
725 # The initial argument should be evaluated #
727 ################################################
729 eval($beginarg) if $beginarg;
731 ################################################
733 # The initial argument has been evaluated #
735 ################################################
737 # Socket related code
738 my $proto = getprotobyname('tcp');
739 $port = $1 if $port =~ /(\d+)/; # untaint port number
741 socket(Server, PF_INET, SOCK_STREAM, $proto) || die "socket: $!";
742 setsockopt(Server, &SOL_SOCKET, &SO_REUSEADDR,
743 pack("l", 1)) || die "setsockopt: $!";
744 bind(Server, sockaddr_in($port, INADDR_ANY)) || die "bind: $!";
745 listen(Server,SOMAXCONN) || die "listen: $!";
748 # Report start of server
749 logmsg "server started on port $port";
751 # Set up SIG vector (every signal will kill the process that receives it)
752 $SIG{CHLD} = 'IGNORE';
753 $SIG{'KILL'} = "SigHandler";
754 $SIG{'TERM'} = "SigHandler";
755 $SIG{'QUIT'} = "SigHandler";
756 $SIG{'HUP'} = "SigHandler";
758 # Define text mime types served if no scripts are defined
759 # Note that the "text/osshell" mime-type is executed by CGIservlet ITSELF!
760 # You should remove it if you don't want that!
761 my %mimeType = (
762 'HTML'=> "text/html",
763 'TXT' => "text/plain",
764 'PL' => "text/plain", # This is incorrect, of course
765 'JPG' => "image/jpeg",
766 'JPEG' => "image/jpeg",
767 'GIF' => "image/gif",
768 'AU' => "audio/basic",
769 'AIF' => "audio/aiff",
770 'AIFC' => "audio/aiff",
771 'AIFF' => "audio/aiff",
772 'GZ' => "application/gzip",
773 'TGZ' => "application/tar",
774 #'CGI' => "text/osshell", # Executes SERVER side shell scripts, HIGHLY DANGEROUS
775 'WAV' => "audio/wav",
776 'OGG' => "audio/x-vorbis",
777 'PDF' => "application/pdf",
778 'PS' => "application/postscript"
781 ################################################
783 # Fill the RAM image of the web site #
785 ################################################
787 my %WWWramImage = ();
788 if($UseRAMimage)
790 my $TotalSize = 0;
791 my @WWWfilelist = `find $textroot ! -type l ! -type d -print`;
792 my $WWWfile;
793 foreach $WWWfile (@WWWfilelist)
795 chomp($WWWfile);
796 # Skip unsupported file types
797 $WWWfile =~ /\.(\w+)$/;
798 my $WWWfileExtension = uc($1);
799 next unless $mimeType{$WWWfileExtension};
800 # Store GnuZipped image of file
801 $WWWramImage{$WWWfile} = "";
802 open(FILEIN, "<$WWWfile") || die "$WWWfile could not be opened: $!\n";
803 my $Buffer;
804 while(sysread(FILEIN, $Buffer, 1024))
806 $WWWramImage{$WWWfile} .= $Buffer;
808 # Apply compression
809 my $CompressedPtr = &$CompressRAMimage(\${WWWramImage{$WWWfile}});
810 $WWWramImage{$WWWfile} = $$CompressedPtr;
811 $TotalSize += length($WWWramImage{$WWWfile});
814 # Report size of Web RAM image
815 print STDERR "Total number of $TotalSize bytes read in memory image\n";
818 ################################################
820 # The RAM image of the web site has been #
821 # filled. #
823 ################################################
825 # Map HTTP request parameters to Environment variables
826 # HTTP request => Environment variable
827 my %HTTPtype = (
828 'content-length' => 'CONTENT_LENGTH', # Necessary for POST
829 'user-agent' => 'HTTP_USER_AGENT',
830 'accept' => 'HTTP_ACCEPT',
831 'content-type' => 'CONTENT_TYPE',
832 'auth-type' => 'AUTH_TYPE',
833 'ident' => 'REMOTE_IDENT',
834 'referer' => 'HTTP_REFERER',
835 'user' => 'REMOTE_USER',
836 'address' => 'REMOTE_ADDR',
837 'connection' => 'HTTP_CONNECTION',
838 'accept-language' => 'HTTP_ACCEPT_LANGUAGE',
839 'accept-encoding' => 'HTTP_ACCEPT_ENCODING',
840 'accept-charset' => 'HTTP_ACCEPT_CHARSET',
841 'host' => 'HTTP_HOST'
844 ###############################################################################
846 # Now we start with the real work. When there is a request, get the required #
847 # values and fork a child to service it. #
849 ###############################################################################
851 my @brood = ();
852 my %StartTime = (); # Start time of the children
853 my $child;
855 # When someone knocks on the door
856 for (;;)
858 my $paddr;
860 if(!($paddr = accept(Client,Server)) ) # Knock knock
862 exit 1; # This went terrribly wrong
865 # Fork to child and parent
866 if(($child =fork()) == 0)
868 # this is the child
869 my ($port,$iaddr) = sockaddr_in($paddr);
870 my $address = inet_ntoa($iaddr); # The IP address of the Client
871 # The following is EXTREMELY slow and generally unnecessary.
872 # Use -n or set $NONAME = 1; if you don't need it.
873 my $name = $NONAME ? '' : gethostbyaddr($iaddr,AF_INET);
874 my @Input = ();
877 # Before doing anything else, check whether the client should be
878 # served at all.
879 # Is IP addr on the list?
880 if(@RemoteAddr && !grep(/^\Q$address\E/, @RemoteAddr))
882 print STDERR "Reject $address $name\n";
883 exit 1;
885 # Is name on the list?
886 if(@RemoteHost && !grep(/\Q$name\E$/, @RemoteHost))
888 print STDERR "Reject $name $address\n";
889 exit 1;
893 # Grab a line without using buffered input... Important for
894 # Post methods since they have to read the Client input stream.
896 my $string = "";
897 my $ch = "";
898 my $HTTPlength = 0;
899 alarm 120 ; # prevent deadly spin if other end goes away
900 while(sysread(Client, $ch, 1)>0)
902 $string .= $ch;
903 ++$HTTPlength;
904 last if $HTTPlength > $MaxLength; # Protect against overflow
906 next if $ch eq "\r"; # skip <cr>
907 if($ch eq "\n")
909 last unless $string =~ /\S/; # stop if empty line
910 push (@Input, split(' ', $string)); # Collect input in list
911 $string = "";
914 alarm 0; # clear alarm
916 # Extract input arguments
917 my $method = shift(@Input);
918 my $Request = shift(@Input);
919 my $protocol = shift(@Input);
920 my ($Path, $QueryString) = split('\?', $Request);
922 # Get rest of Input
923 my $HTTPparameter;
924 my %HTTPtable = ();
925 while($HTTPparameter = lc(shift(@Input)))
927 chop($HTTPparameter);
928 $HTTPtable{$HTTPparameter} = "";
929 while(@Input && $Input[0] !~ /\:$/)
931 $HTTPtable{$HTTPparameter} .= " " if $HTTPtable{$HTTPparameter};
932 $HTTPtable{$HTTPparameter} .= shift(@Input);
935 # Host can get the :SERVER_PORT appended. Set the correct SERVER_PORT
936 # and remove it from the host.
937 if($HTTPtable{'host'})
939 # Store current port number
940 if($HTTPtable{'host'} =~ /\:(\d+)\s*$/)
942 $ENV{'SERVER_PORT'} = $1;
944 # Remove port number from host
945 $HTTPtable{'host'} =~ s/\:(\d+)\s*$//g;
948 # Translate the Aliases
949 $Path = GetAlias($Path);
951 # HTTP servers should always add the default path
952 $Path = $welcome if !$Path || $Path eq '/'; # The common default path
954 # Set fixed environment variables
955 $ENV{'PATH_INFO'} = "$Path";
956 $ENV{'QUERY_STRING'} = "$QueryString";
957 $ENV{'PATH_TRANSLATED'} = "$textroot$Path";
958 $ENV{'SERVER_PROTOCOL'} = "$protocol";
959 $ENV{'REQUEST_METHOD'} = "$method";
960 $ENV{'REMOTE_ADDR'} = "$address"; # The IP address of the Client
961 $ENV{'REMOTE_HOST'} = "$name";
963 # Load all request information in the %ENV.
964 # MUST be done with a pre-defined list of parameter names (security).
965 foreach $HTTPparameter (keys(%HTTPtype))
967 my $Label = $HTTPtype{$HTTPparameter};
968 # The following adds environment variables FROM THE REQUEST.
969 # It is a VERY, VERY bad idea to just use the client supplied
970 # parameter names!
971 $ENV{$Label} = $HTTPtable{$HTTPparameter} unless exists($ENV{$Label});
972 # (The last part prevents overwriting existing environment variables)
975 # SECURITY: Check length of POST request. Stop if request is too long
976 die if $HTTPlength + $ENV{'CONTENT_LENGTH'} > $MaxLength;
978 # If POST requests are unwanted, they can be added tot the query string
979 # NOTE: the method is set to GET if $POSTtoGET equals 'GET', otherwise,
980 # the method stays POST and only the content length is set to 0
981 if($POSTtoGET && $ENV{'REQUEST_METHOD'} =~ /^POST$/i)
983 my $POSTlength = $ENV{'CONTENT_LENGTH'} || 0;
984 my $ReadBytes = 1;
986 # Add '&' if there is a query string already
987 if($ENV{'QUERY_STRING'})
989 # Before we add something to the string, check length again
990 die if $HTTPlength + $ENV{'CONTENT_LENGTH'} + 1 > $MaxLength;
991 # Now add the '&'
992 $ENV{'QUERY_STRING'} .= '&';
995 # Read Client
996 while($POSTlength > 0 && $ReadBytes > 0)
998 my $Read = "";
999 $ReadBytes = sysread(Client, $Read, $POSTlength);
1000 $ENV{'QUERY_STRING'} .= $Read;
1001 $POSTlength -= $ReadBytes;
1004 # All has been read, the content length becomes 0
1005 $ENV{'CONTENT_LENGTH'} = 0;
1006 # Method can change
1007 $ENV{'REQUEST_METHOD'} = 'GET' if $POSTtoGET eq 'GET';
1011 # Connect STDOUT and STDIN to the client
1012 open(STDIN, "<&Client");
1013 open(STDOUT, ">&Client");
1014 print STDOUT "HTTP/1.1 200 OK\n"; # Supply HTTP protocol information
1015 print STDOUT "Date: ".gmtime()." GMT\n"; # Current date
1016 print STDOUT "Server: $program $version\n"; # This program
1017 print STDOUT "Connection: close\n"; # Don't allow persistent connections
1019 # Start processing of request (note that ALL scripts will be executed if
1020 # present, i.e., if -d, -x, and -e are entered, they are alle processed).
1022 # If in memory-only mode, store the requested file in an environment
1023 # variable: CGI_FILE_CONTENTS
1024 undef($ENV{'CGI_FILE_CONTENTS'}); # Make sure the ENV var doesn't exist
1025 if($UseRAMimage)
1027 my $DecompressedPtr = &$DecompressRAMimage(\${WWWramImage{"$textroot$Path"}});
1028 $ENV{'CGI_FILE_CONTENTS'} = $$DecompressedPtr;
1029 # Decompression does not seem to work
1032 # do perl script
1033 @ARGV = ("$textroot$Path", $QueryString);
1034 # This was suggested by Jochen_Hayek@ACM.org
1035 if($doarg)
1037 # The perl script should do the printing
1038 my ($return) = do "$doarg";
1040 warn "couldn't parse $doarg: $@" if $@;
1041 warn "couldn't $doarg: $!" unless defined $return;
1042 warn "couldn't run $doarg" unless $return;
1045 # evaluate perl command
1046 print STDOUT eval($evalarg) if $evalarg;
1048 # execute shell command
1049 if($execarg)
1051 my $shellscript = $execarg;
1053 # Attempts to use Paths or Queries containing '-quotes are rejected.
1054 # Executing these would compromise security.
1055 die "Quotes in path: $textroot$Path\n" if "$textroot$Path" =~ /\'/;
1056 $shellscript .= " '$textroot$Path'" if $Path;
1058 die "Quotes in query: $QueryString\n" if $QueryString =~ /\'/;
1059 $shellscript .= " '$QueryString'" if $QueryString;
1060 $shellscript = qx{$shellscript};
1061 print STDOUT $shellscript;
1064 # Output files if no scripts are given (actually, this should be
1065 # handled by a script). Unknown mimetypes are killed.
1066 # This is more or less a functional (dynamic) Web server in itself.
1067 unless($doarg || $execarg || $evalarg) # Request not already handled
1069 die ".. trick: $address $name $Path $QueryString\n"
1070 if $Path =~ m@\.\./@ ; # No tricks!
1072 # Handle mime-types and directory browsing
1073 $Path =~ /\.([\w]+)$/; # Get extension
1074 my $extension = uc($1);
1075 my $browse = ($Path =~ m@/\s*$@ || -d "$textroot$Path") ? 1 : 0;
1076 my $mime = $browse ? "" : $mimeType{$extension};
1078 # Serve up text and binary files unless they the $Secure option is given
1079 $mime = "text/plain" if !$mime && !$browse && (-T "$textroot$Path") && !$Secure;
1080 $mime = "application/octet-stream" if !$mime && !$browse && (-B "$textroot$Path") && !$Secure;
1082 # Remove final / in directory paths
1083 $Path =~ s@/\s*$@@g;
1085 # Block illegal mime-types
1086 die "Illegal mime type:$extension\n" unless $mime || $browse; # illegal mime's are killed
1088 # Print out the document
1089 if(($mime eq 'text/osshell') && $ExecuteOSshell) # Don't use this unless you know what you're doing
1091 # Note that CGI scripts must supply their own content type
1092 # Some rudimentary security tests
1093 # Kill child if the path contains any non-URL characters
1094 die "ATTACK: ADDR:$ENV{'REMOTE_ADDR'} HOST:$ENV{'REMOTE_HOST'} URL=$Path '$QueryString'\n"
1095 if $Path =~ m@[^\w\-\.\/]@; # Exclusive list of allowed characters
1096 # If you want to execute server side shell scripts, use the 'text/osshell'
1097 # mime-type (see above) but remember that there is NO SECURITY implemented
1098 # whatsoever.
1099 # IF YOU DIDN'T GET THE MESSAGE YET, YOU COULD NOW OPEN YOUR COMPUTER TO THE WHOLE
1100 # INTERNET TO PLAY WITH!
1101 # Plain Web site from DISK
1102 unless($UseRAMimage)
1104 print STDOUT `$textroot$Path`; # This is Russian Roulette
1106 else # Use a RAM image of the web site
1108 my $ShellInterpreter = '/usr/bin/sh';
1109 if($ENV{'CGI_FILE_CONTENTS'} =~ /^\#\!\s*([^\r\n]+)/isg)
1111 $ShellInterpreter = $1;
1113 # Execute shell script
1114 open(RAMOUT, "| $ShellInterpreter") || die "ERROR open RAMOUT $ShellInterpreter $textroot$Path $! $@\n";
1115 (print RAMOUT $ENV{'CGI_FILE_CONTENTS'}) || die "ERROR print RAMOUT $ShellInterpreter $textroot$Path $! $@\n";
1116 close(RAMOUT);
1119 elsif($mime)
1121 # Content-type and document
1122 print STDOUT "Content-type: $mime\n\n";
1123 # Plain Web site from DISK
1124 unless($UseRAMimage)
1126 my $String = "";
1127 my $number_of_bytes = 0;
1128 open(BINARY, "<$textroot$Path") || die "$textroot$Path: $!";
1130 # read and write block of 1024 bytes
1131 while($number_of_bytes = sysread(BINARY, $String, 1024))
1133 syswrite(STDOUT, $String, $number_of_bytes); # Actually print the file content
1135 close(BINARY);
1137 # Alternative output using the UNIX shell
1138 # print STDOUT `cat '$textroot$Path'`; # lazy, let the OS do the work
1140 else # Use a RAM image of the web site
1142 print STDOUT $ENV{'CGI_FILE_CONTENTS'};
1146 elsif($browse && !$Secure) # Block directory browsing in the Secure setup
1148 # Content-type and document
1149 print STDOUT "Content-type: text/html\n\n";
1150 opendir(BROWSE, "$textroot$Path") || die "<$textroot$Path: $!\n";
1152 print "<HTML>\n<HEAD>\n<TITLE>$Path</TITLE></HEAD>\n<BODY>\n<H1>$Path</H1>\n<pre>\n<dl>";
1154 my $DirEntry;
1155 foreach $DirEntry (sort {lc($a) cmp lc($b)} readdir(BROWSE))
1157 my $CurrentPath = $Path;
1158 # Handle '..'
1159 if($DirEntry eq '..')
1161 my $ParentDir = $CurrentPath;
1162 $ParentDir =~ s@/[^/]+$@@g;
1163 $ParentDir = '/' unless $ParentDir;
1164 print "<dt> <a href='$ParentDir'><h3>Parent directory</h3></a></dt>\n";
1166 next if $DirEntry !~ /[^\.\/\\\:]/;
1168 # Get aliases
1169 my $Alias = GetAlias("$CurrentPath/$DirEntry");
1170 if($Alias ne "$CurrentPath/$DirEntry")
1172 $Alias =~ m@/([^/]+)$@;
1173 $CurrentPath = $`;
1174 $DirEntry = $1;
1177 my $Date = localtime($^T - (-M "$textroot$CurrentPath/$DirEntry")*3600*24);
1178 my $Size = -s "$textroot$CurrentPath/$DirEntry";
1179 $Size = sprintf("%6.0F kB", $Size/1024);
1180 my $Type = `file $textroot$CurrentPath/$DirEntry`;
1181 $Type =~ s@\s*$textroot$CurrentPath/$DirEntry\s*\:\s*@@ig;
1182 chomp($Type);
1183 print "<dt> <a href='$CurrentPath/$DirEntry'>";
1184 printf("%-40s", $DirEntry."</a>");
1185 print "\t$Size\t$Date\t$Type</dt>\n";
1187 close(BROWSE);
1188 print "</dl></pre></BODY>\n</HTML>\n";
1193 close(STDOUT) || die "STDOUT: $!\n";
1194 close(STDIN) || die "STDIN: $!\n";
1195 close(Client) || die "Client: $!\n";
1197 exit 0; # Kill Child
1199 else
1202 # parent code...some systems will have to worry about waiting
1203 # before they can actually close the link to the Client
1204 my $current_time = time();
1206 # Determine which of the children are actually still alive
1207 # and kill those that have run for too long (probably not connected anymore)
1208 my @old_brood = @brood;
1209 @brood = (); # empty brood
1210 foreach (@old_brood)
1212 # Kill the child if it runs for longer than MaxTime
1213 if(($StartTime{$_} - $current_time) > $MaxTime)
1215 kill "KILL", $_;
1218 # Store children that are alive
1219 if(kill (0, $_)) # Alive?
1221 push(@brood, $_);
1223 else
1225 delete($StartTime{$_});
1229 # Weed out overflow of children (zombies etc.), keep pid for
1230 # removing the StartTime later on
1231 my $oldest;
1232 for($oldest=0; $oldest < scalar(@brood)-$MaxBrood; ++$oldest)
1234 kill "KILL", $brood[$oldest] if $brood[$oldest]; # Remove
1237 # Child pid could be recycled, i.e., $child could be stored
1238 # in @brood already. Remove it
1239 @brood = grep($_ != $child, @brood);
1241 # Push new child on the list
1242 push (@brood, $child);
1243 $StartTime{$child} = $current_time;
1245 close Client; # This is it, ready!
1249 # Interupt handler for shutting down
1250 sub SigHandler
1252 my $sig = shift;
1253 exit 1;
1256 # Subroutine for Aliases
1257 # Uses Global variables: %AliasTranslation, @RegAliasTranslation, and @RegURLTranslation
1258 sub GetAlias # ($Path)->AliasURL
1260 my $Path = shift;
1262 # Translate the Aliases
1263 if($AliasTranslation{$Path})
1265 $Path = $AliasTranslation{$Path};
1267 elsif(@RegAliasTranslation)
1269 my $i;
1270 for($i=0; $i<scalar(@RegAliasTranslation); ++$i)
1272 my $Alias = $RegAliasTranslation[$i];
1273 my $RealURL = $RegURLTranslation[$i];
1274 last if ($Path =~ s#$Alias#$RealURL#g);
1277 return $Path;
1280 =head1 NAME
1282 CGIservlet - a HTTPd "connector" for running CGI scripts on unix systems as WWW
1283 accessible Web sites.
1285 =head1 DESCRIPTION
1287 The servlet starts a true HTTP daemon that channels
1288 HTTP requests to forked daughter processes. Can run
1289 a (small) WWW-site from memory.
1291 =head1 README
1293 Whenever an HTTP request is received, the specified CGI script is
1294 started inside a child process as if it was inside a real server (e.g.,
1295 Apache). The evironment variables are set more or less as in Apache.
1296 Note that CGIservlet only uses a SINGLE script for ALL requests.
1297 No attemps for security are made, it is the script's responsibility to
1298 check access rights and the validity of the request.
1299 Can store the files of Web site in memory and serve them
1300 on request.
1302 =head1 PREREQUISITES
1304 This script requires the C<strict>, Socket and Carp modules.
1306 =head1 COREQUISITES
1308 =pod OSNAMES
1310 Unix
1312 =pod SCRIPT CATEGORIES
1317 =cut