Add captcha to contact form

Signed-off-by: Morris Jobke <hey@morrisjobke.de>

1 files changed, 17 insertions, 1 deletions

diff --git a/page-contactsubmit.php b/page-contactsubmit.php
index 3eea2663..08a0e616 100644
--- a/page-contactsubmit.php
+++ b/page-contactsubmit.php
@@ -40,14 +40,30 @@ if(isset($_POST['email'])) {
         !isset($_POST['email']) ||
         !isset($_POST['organization']) ||
         !isset($_POST['phone']) ||
-        !isset($_POST['comments'])) {
+        !isset($_POST['comments']) ||
+        !isset($_POST['checksum']) ||
+        !isset($_POST['captcha'])) {
         died('We are sorry, but there appears to be a problem with the form you submitted - did you fill in all fields?'); }
     $yourname = $_POST['yourname']; // required
     $organization= $_POST['organization']; // required
     $phone= $_POST['phone']; // required
     $email_from = $_POST['email']; // required
     $comments = $_POST['comments']; // required
+    $checksum = $_POST['checksum']; // required
+    $captcha = $_POST['captcha'];
     $error_message = "";
+    if (strlen($checksum) !== 75 || !strpos($checksum, ':')) {
+        $error_message .= 'The checksum is not valid.<br />';
+    } else {
+        list($salt, $expectedHash) = explode(':', $checksum, 2);
+        $hash = hash('sha256', $salt . $captcha);
+
+        if ($hash !== $expectedHash) {
+            $error_message .= 'The captcha result you entered does not appear to be correct.<br />';
+        }
+    }
+
+
     $email_exp = '/^[A-Za-z0-9._%-]+@[A-Za-z0-9.-]+\.[A-Za-z]{2,10}$/';
   if(!preg_match($email_exp,$email_from)) {
     $error_message .= 'The email address you entered does not appear to be valid.<br />';