checking for possible issues on upload_picture api

res/forum/api/upload_picture.php

@@ -1,6 +1,41 @@
 <?php
 
-$status = 0;
+include("../../global.php");
+session_start();
 
+if (!isset($_SESSION["username"])) goto fail;
+
+$out = $database -> query("SELECT username, admin FROM user WHERE BINARY username=\"" . $_SESSION["username"] . "\" AND admin=\"1\"");
+
+if ($out -> num_rows != 1)
+{
+    fail:
+    echo "nope";
+    header("Location: ../../../index.php");
+    return;
+}
+
+$status = 0;
+$supported_formats = array("jpg", "jpeg", "png", "webp");
+
+if (!isset($_FILES["file_upload"]))
+{
+    $status = 1;
+    goto send;
+}
+
+if (!isset($_POST["name"]))
+{
+    $status = 2;
+    goto send;
+}
+
+if (!in_array(strtolower(pathinfo($_FILES["file_upload"]["name"], PATHINFO_EXTENSION)), $supported_formats))
+{
+    $status = 3;
+    goto send;
+}
+
+send:
 header('Content-type: application/json');
 echo json_encode(["status" => $status]);