#!/usr/bin/perl

use CGI::Carp qw(fatalsToBrowser);
use Net::DNS;
use Socket;

my $url = my $path = $ENV{'REQUEST_URI'};
my $host = $ENV{'HTTP_HOST'};
my $referrer = $ENV{'HTTP_REFERER'};
my $useragent = $ENV{'USER_AGENT'};
my $content_type;
$path =~ s#/([^/])*$##;

GETCONTENT: $content_type = &get_content_type;

&print_gif if $content_type =~ /image/;
&print_text;
exit;

sub print_text { print "Content-type: $content_type\n\n<!-- -->\n"; ex
+it }

sub print_gif {
    # Prints a transparent GIF. Adapted from code created by Turnstep:
    # http://www.perlmonks.org/index.pl?node_id=7974
    print "Content-Length: 43\nContent-type: image/gif\n\n";
    printf "GIF89a\1\0\1\0%c\0\0%c%c%c\0\0\0%s,\0\0\0\0\1\0\1\0\0%c%c%
+c\1\0;",
     144,0,0,0,1?pack("c8",33,249,4,5,16,0,0,0):"",2,2,4;
    exit;
}

sub nslookup {
    my $host = shift;
    my $dns = new Net::DNS::Resolver;
    my $query = $dns->search($host);
    if ($query) {
        for $rr ($query->answer) {
            next unless $rr->type eq "A";
            return $rr->address;
        }
    }
    else {
        die "lookup of $host failed: ", $dns->errorstring, "\n";
    }
}
sub get_content_type {

    my ($type, $location);
    my $addr = &nslookup($host);
    my $proto = getprotobyname('tcp');
    my $inet = inet_aton($addr);

    socket(S,PF_INET,SOCK_STREAM,$proto) || die "Couldn't open socket:
+ $!";

    if (connect(S,pack "SnA4x8",2,80,$inet)) {
        select (S);
        $| = 1;
        print "GET $url HTTP/1.0\r\n";
        print "Referer: $referrer\r\n";
        print "User-Agent: $useragent\r\n\r\n";
        while (<S>) {
            if (/^Content-type:\s*(.*)(?:\;|\n)/i) { $type = $1 }
            if (/^Location:\s*(.*)$/i) { $location = $1 }
            last if /^\s*$/; # Close the connection after getting the 
+headers
        }
        select (STDOUT);
        close S;
    } else { die "Couldn't connect to $host : $!" }

    if ($location) { # We've been redirected
        if ($location =~ m#^http://([^/]*)/(.*)$#) {
            $host = $1;
            $url = "/$2";
            }
        else {
            $url = ($location =~ /^$path/o) ? $location : "$path/$loca
+tion";
        }
        goto GETCONTENT;
    }
    return $type;
}
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