server/submission.php

<?php

function show($file)
{
    if (file_exists($file))
        print file_get_contents($file);
    else
        header("HTTP/1.1 403 Forbidden");
}

$filename = intval($_GET["team"])."-".intval($_GET["theme"])."-".urlencode($_GET["exercice"]);
$file = __DIR__."/submission/".$filename;


if (file_exists($file))
    show(__DIR__."/teams/".intval($_GET["team"])."/".urlencode($_GET["theme"])."/".urlencode($_GET["exercice"])."/submission/serr/index.html");

else if (!empty($_POST["solution"]) && !empty($_GET["team"]) && !empty($_GET["theme"]) && !empty($_GET["exercice"]))
{
    $algos = array("md5", "sha1", "sha256", "sha384", "sha512", "whirlpool");
    $content = "";
    foreach($algos as $algo)
    {
      $cnt = hash($algo, $filename, true);
      // Encrypt twice on long key
      $key = hash($algo, $_POST["solution"]);

      $kfirst = pack('H*', substr($key, 0, 64));
      $cnt = mcrypt_encrypt(MCRYPT_SERPENT, $kfirst, $cnt, MCRYPT_MODE_ECB);

      if (strlen($key) > 64)
      {
	$ksec = pack('H*', substr($key, 64, 64));
	$cnt = mcrypt_encrypt(MCRYPT_SERPENT, $ksec, $cnt, MCRYPT_MODE_ECB);
      }

      $content .= bin2hex($cnt)."\n";
    }

    file_put_contents($file, $content, LOCK_EX);

    show(__DIR__."/teams/".intval($_GET["team"])."/".urlencode($_GET["theme"])."/".urlencode($_GET["exercice"])."/submission/index.html");
}

else
    show(__DIR__."/teams/".intval($_GET["team"])."/".urlencode($_GET["theme"])."/".urlencode($_GET["exercice"])."/submission/gerr/index.html");