Friendly, easy, lightweight, self-hostable CAPTCHA service. https://captcheck.netsyms.com
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<?php
require __DIR__ . '/required.php';
header("Content-Type: application/json");
// Oldest session allowed
$session_min_date = date("Y-m-d H:i:s", strtotime("-" . SESSION_EXPIRE_MINUTES . " minutes"));
// Delete old sessions
$old_sessions = $database->select("sessions", "sid", ["timestamp[<]" => $session_min_date]);
$database->delete("scrambled_answers", ["sid" => $old_sessions]);
$database->delete("sessions", ["sid" => $old_sessions]);
switch ($VARS['action']) {
case "ping":
$out = ["status" => "OK", "pong" => true];
exit(json_encode($out));
case "new":
// generate unique session ID that has an essentially zero chance of being a duplicate.
// Contains a hash of a secure random number, a hash of the user's IP, and 23 uniqid() characters.
$skey = uniqid(substr(hash("md5", mt_rand()), 3, 5) . hash("md5", getUserIP()), true);
$answers = $database->select('answers', ['aid', 'aname']);
shuffle($answers);
$answers = array_slice($answers, 0, 5);
//var_dump($answers);
$correct_answer = $answers[mt_rand(0, count($answers) - 1)];
$scrambled = ["real" => [], "fake" => []];
foreach ($answers as $a) {
$scrambled["real"][] = $a['aid'];
$scrambled["fake"][] = substr(hash("md5", mt_rand()), 0, 20);
}
$database->insert("sessions", ["skey" => $skey, "aid" => $correct_answer['aid'], "expired" => 0, "#timestamp" => "NOW()"]);
$sid = $database->id();
$scrambled_insert = [];
for ($i = 0; $i < count($scrambled['real']); $i++) {
$scrambled_insert[] = ["sid" => $sid, "aid" => $scrambled['real'][$i], "acode" => $scrambled['fake'][$i]];
}
$database->insert("scrambled_answers", $scrambled_insert);
$resp = [
"session" => $skey,
"question" => $correct_answer['aname'],
"answers" => $scrambled["fake"]
];
exit(json_encode($resp));
case "img":
if (!$database->has('sessions', ['skey' => $VARS['s']])) {
sendError("Missing or invalid session ID.", "client");
}
$sid = $database->get('sessions', 'sid', ['skey' => $VARS['s']]);
if (!$database->has("scrambled_answers", ["AND" => ["sid" => $sid, "acode" => $VARS['c']]])) {
sendError("Missing or invalid image code.", "client");
}
$imgid = $database->get("scrambled_answers", ["[>]answers" => ["aid" => "aid"]], 'aimg', ["AND" => ["sid" => $sid, "acode" => $VARS['c']]]);
/* Load image, add some black/white noise, and send */
header('Content-Type: image/png');
$imgpath = __DIR__ . "/images/" . $imgid . ".png";
if (DEBUG) {
file_put_contents("debug", $imgpath . "\n", FILE_APPEND);
}
$img = imagecreatefrompng($imgpath);
imageAlphaBlending($img, true);
imageSaveAlpha($img, true);
$black = imagecolorallocate($img, 0, 0, 0);
$white = imagecolorallocate($img, 255, 255, 255);
for ($i = 0; $i < 512; $i++) {
imagesetpixel($img, mt_rand(0, 63), mt_rand(0, 63), $black);
}
for ($i = 0; $i < 256; $i++) {
imagesetpixel($img, mt_rand(0, 63), mt_rand(0, 63), $white);
}
imagepng($img);
exit();
case "verify":
if (!$database->has('sessions', ['skey' => $VARS['session_id']])) {
echo json_encode(["session" => $VARS['session_id'], "result" => false, "msg" => "Session invalid."]);
exit();
}
$sid = $database->get('sessions', 'sid', ['skey' => $VARS['session_id']]);
$expired = ($database->get('sessions', 'expired', ['skey' => $VARS['session_id']]) == 1 ? true : false);
if ($expired) {
echo json_encode(["session" => $VARS['session_id'], "result" => false, "msg" => "Session key already used."]);
exit();
}
if (!$database->has("scrambled_answers", ["AND" => ["sid" => $sid, "acode" => $VARS['answer_id']]])) {
echo json_encode(["session" => $VARS['session_id'], "result" => false, "msg" => "Answer invalid."]);
exit();
}
$aid = $database->get('scrambled_answers', 'aid', ["AND" => ["sid" => $sid, "acode" => $VARS['answer_id']]]);
if ($database->has('sessions', ["AND" => ["sid" => $sid, "aid" => $aid]])) {
echo json_encode(["session" => $VARS['session_id'], "result" => true]);
} else {
echo json_encode(["session" => $VARS['session_id'], "result" => false, "msg" => "Answer incorrect."]);
}
$database->update("sessions", ['expired' => 1], ["sid" => $sid]);
exit();
default:
sendError("Bad Request", "client");
}