okay

main/admin.php

@@ -33,6 +33,18 @@ if ($_SERVER['REQUEST_METHOD'] === 'POST') {
             $stmt = $db->prepare('UPDATE users SET is_blocked = 0 WHERE username = ?');
             $stmt->execute([$username]);
             $success = "User $username has been unbanned";
+        } elseif ($_POST['action'] === 'preventive_ban') {
+            if (!preg_match('/^[a-zA-Z0-9_]+$/', $username)) {
+                $error = "Invalid username format";
+            } else {
+                $stmt = $db->prepare('INSERT INTO banned_usernames (username) VALUES (?)');
+                try {
+                    $stmt->execute([$username]);
+                    $success = "Username $username has been preventively banned";
+                } catch (PDOException $e) {
+                    $error = "Username already banned";
+                }
+            }
         }
     }
 }
@@ -100,6 +112,15 @@ $users = $stmt->fetchAll(PDO::FETCH_ASSOC);
             <div class="success"><?= htmlspecialchars($success) ?></div>
         <?php endif; ?>
 
+        <div class="preventive-ban">
+            <h2>Preventive Ban</h2>
+            <form method="post" class="ban-form">
+                <input type="text" name="username" placeholder="Username to ban" required pattern="[a-zA-Z0-9_]+" maxlength="50">
+                <input type="hidden" name="action" value="preventive_ban">
+                <button type="submit" class="ban-btn">Ban Username</button>
+            </form>
+        </div>
+
         <table class="admin-table">
             <thead>
                 <tr>

main/register.php

@@ -31,27 +31,33 @@ if ($_SERVER['REQUEST_METHOD'] === 'POST') {
         } else if (strlen($pgp_key) > 4096) {
             $error = 'PGP key is too long';
         } else {
-            $stmt = $db->prepare('SELECT COUNT(*) FROM registrations WHERE created_at > DATE_SUB(NOW(), INTERVAL 1 HOUR)');
+            $stmt = $db->prepare('SELECT COUNT(*) FROM banned_usernames WHERE username = ?');
-            $stmt->execute();
+            $stmt->execute([$username]);
-            $count = $stmt->fetchColumn();
+            if ($stmt->fetchColumn() > 0) {
-
+                $error = 'This username is not allowed';
-            if ($count >= 20) {
-                $error = 'Registration limit exceeded';
             } else {
-                try {
+                $stmt = $db->prepare('SELECT COUNT(*) FROM registrations WHERE created_at > DATE_SUB(NOW(), INTERVAL 1 HOUR)');
-                    $stmt = $db->prepare('INSERT INTO users (username, password, pgp_key, login_attempts, last_attempt) VALUES (?, ?, ?, 0, NOW())');
+                $stmt->execute();
-                    $stmt->execute([
+                $count = $stmt->fetchColumn();
-                        $username, 
-                        password_hash($password, PASSWORD_DEFAULT, ['cost' => 12]), 
-                        $pgp_key
-                    ]);
 
-                    $stmt = $db->prepare('INSERT INTO registrations () VALUES ()');
+                if ($count >= 20) {
-                    $stmt->execute();
+                    $error = 'Registration limit exceeded';
+                } else {
+                    try {
+                        $stmt = $db->prepare('INSERT INTO users (username, password, pgp_key, login_attempts, last_attempt) VALUES (?, ?, ?, 0, NOW())');
+                        $stmt->execute([
+                            $username, 
+                            password_hash($password, PASSWORD_DEFAULT, ['cost' => 12]), 
+                            $pgp_key
+                        ]);
                         
-                    $success = 'Registration successful';
+                        $stmt = $db->prepare('INSERT INTO registrations () VALUES ()');
-                } catch (PDOException $e) {
+                        $stmt->execute();
-                    $error = 'Username already exists';
+                        
+                        $success = 'Registration successful';
+                    } catch (PDOException $e) {
+                        $error = 'Username already exists';
+                    }
                 }
             }
         }

sql/migrate.sql

@@ -22,3 +22,9 @@ DELIMITER ;
 
 CALL migrate_if_needed();
 DROP PROCEDURE IF EXISTS migrate_if_needed;
+
+CREATE TABLE IF NOT EXISTS banned_usernames (
+    id INT AUTO_INCREMENT PRIMARY KEY,
+    username VARCHAR(50) NOT NULL UNIQUE,
+    created_at TIMESTAMP DEFAULT CURRENT_TIMESTAMP
+);