KnoppiLights Upload

The Challenge:

Provide a method for students to turn in project files from a Knoppix based Live-CD and/or VmWare VM.

Solutions considered: Email - using mailx - a command line mailer
  • Curl - a command line utility to communicate with web forms
  • Worked on both in parallel in beginning -


    Try No. 1:
    (cat mesgfile ; uuencode image.jpg image.jpg ) | mailx -s 'KnoppiLights' 
    Try No. 2:
    #!/usr/bin/perl -w
    use Net::SMTP;
    $smtp = Net::SMTP->new('my.address',
                            Debug =>1);
    $smtp->datasend("From: whinnery\@my.address\n");
    $smtp->datasend("To: Peter Whinnery\n");
    $smtp->datasend("Subject: Lightlab mail test\n");
    $smtp->datasend("A simple test 3 message\n");
    $smtp->datasend("A second line of text.\n");

    Was able to send file via email with tools from the Net:Smpt perl module. Univ account marked it as spam.


    With this client/server solution I had to consider both ends of the transaction. With email I only had control of the client end.

    Server Side

    CGI scripts are programs that output their results as web pages. Output is html. I Found an example 'file upload' cgi script (in perl) on the web and installed on webserver.

    Client Side

    Sent file w/ curl from Knoppix disk. Chose this method as one to persue and implement in LightLab.

    Edited example script:

    Added security - Run from Virtual Machine

    Lost remote access to office webserver (UPS died) on a Friday - too lazy to go in and troubleshoot - forced me to setup Apache (webserver) on a Virtual Machine (VMWare). Used a non-graphic install of Ubuntu. Set Apache to listen on port 8080 (non-standard). Images are uploaded to a password protected directory.

    Cool Stuff



    #!/usr/bin/perl -T
     # A sample file upload script
     use strict;
     use warnings;
     use CGI;
     use CGI::Carp qw(fatalsToBrowser); # Remove for production use
     $CGI::POST_MAX = 1024 * 100;  # maximum upload filesize is 100K
     sub save_file($);
     # Build the form
    my $q = new CGI;
     print $q->header;
     print $q->start_html(
         -title => "An example file upload web page",
     print $q->h3('Use this form to upload a local file to the web server'),
         -name => 'main_form');
     print 'Enter a filename, or click on the browse button to choose one: ',
         -name   => 'filename',
        	  -size   => 40,
     	  -maxlength => 80);
        print $q->hr;
     print $q->submit(-value => 'Upload the file');
     print $q->hr;
        print $q->end_form;
        # Look for uploads that exceed $CGI::POST_MAX
        if (!$q->param('filename') && $q->cgi_error()) {
         print $q->cgi_error();
         print <<'EOT';

    The file you are attempting to upload exceeds the maximum allowable file size.

    Please refer to your system administrator EOT print $q->hr, $q->end_html; exit 0; } # # Upload the file # if ($q->param()) { save_file($q); } print $q->end_html; exit 0; #------------------------------------------------------------- sub save_file($) { my ($q) = @_; my ($bytesread, $buffer); my $num_bytes = 1024; my $totalbytes; my $filename = $q->upload('filename'); my $untainted_filename; if (!$filename) { print $q->p('You must enter a filename before you can upload it'); return; } # Untaint $filename if ($filename =~ /^([-\@:\/\\\w.]+)$/) { $untainted_filename = $1; } else { die <<"EOT"; Unsupported characters in the filename "$filename". Your filename may only contain alphabetic characters and numbers, and the characters '_', '-', '\@', '/', '\\' and '.' EOT } if ($untainted_filename =~ m/\.\./) { die <<"EOT"; Your upload filename may not contain the sequence '..' Rename your file so that it does not include the sequence '..', and try again. EOT } my $file = "/tmp/$untainted_filename"; print "Uploading $filename to $file
    "; # If running this on a non-Unix/non-Linux/non-MacOS platform, be sure to # set binmode on the OUTFILE filehandle, refer to # perldoc -f open # and # perldoc -f binmode open (OUTFILE, ">", "$file") or die "Couldn't open $file for writing: $!"; while ($bytesread = read($filename, $buffer, $num_bytes)) { $totalbytes += $bytesread; print OUTFILE $buffer; } die "Read failure" unless defined($bytesread); unless (defined($totalbytes)) { print "

    Error: Could not read file ${untainted_filename}, "; print "or the file was zero length."; } else { print "

    Done. File $filename uploaded to $file ($totalbytes bytes)"; } close OUTFILE or die "Couldn't close $file: $!"; } #-------------------------------------------------------------