in reply to Not Strictly A perl question.

It's Perl enough for me. I'm a bit tired so you don't get the full answer, but here's the quick rundown.

When you put a link in a webpage, the browser loads the HTML, then loads the images as if you were following links to the images. In short, an <img src="lalala"> tag acts exactly like a <a href="lalala"> tag. There is no problem at all with having the target of a img tag being a cgi.

So your img tag becomes <img src="image_server.pl?image=goodpic.jpg>.

The CGI becomes:



#!/usr/local/bin/perl -w

use CGI qw/:all/;
my $query = CGI::new();
my $file = $query->param("image");

open ( IMAGE, $file );
while ( <IMAGE> ) {
        print $_;
        }
        
exit ;

[download]

You are on the right track. A lot of sites have "image servers" - web servers that just host images. Cuts down the load on any one server. I'll let someone else shout about security, but consider what could happen if someone typed "image_server.pl?image=/etc/password" into their browser...

____________________
Jeremy
I didn't believe in evil until I dated it.

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Re: Re: Not Strictly A perl question.
by Zaxo (Archbishop) on Jul 01, 2001 at 00:19 UTC

    I'll fill out some of the bits jepri left out

    As it stands the code has a classic cgi security hole. It trusts user input for file system locations (e.g. ?image=/etc/passwd). Here is a safer rewrite:

    #!/usr/local/bin/perl -wT

use strict;
use CGI qw/:all/;

my %images = (
    'tophat'=> {
        'path'=>"/usr/somewhere/way/out/of/reach/Top Hat.jpeg",
        'mime'=>"image/jpeg"},
    'racecar'=> {
        'path'=>"/usr/somewhere/way/out/of/reach/Bugatti.png",
        'mime'=>"image/png"},
    #etc...
);

my $query = CGI::new();
my $file = $query->param("image");

$|=1;
if (defined $images{$file}) {
    print $query->header({-type=>$images{$file}{'mime'}});}
    open ( IMAGE, $images{$file}{'path'} );
    print while ( <IMAGE> );
    close(IMAGE);
}
else {
    print $query->header({-type=>'text/html',
                          -status=>"404 File Not Found"});
}

exit ;

    [download]

    This is a forgiving approach to bad input, more BOFHish to log and play games.

    After Compline,
    Zaxo

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