Add rate limiting on login and password reset endpoints

Track attempts per IP in a rate_limits table with a sliding time
window. Login allows 5 failed attempts per 15 min, password reset
allows 3 requests per 15 min. Old entries are purged automatically.

1 files changed, 60 insertions, 0 deletions

diff --git a/src/app/RateLimiter.php b/src/app/RateLimiter.php
new file mode 100644
index 0000000..07b46ba
--- /dev/null
+++ b/src/app/RateLimiter.php
@@ -0,0 +1,60 @@
+<?php
+
+declare(strict_types=1);
+// Rate limiter: prevents brute-force attacks by tracking how many times an IP
+// performs a given action (e.g. login, password reset) within a sliding time window.
+
+namespace App;
+
+class RateLimiter
+{
+    private \PDO $pdo;
+
+    public function __construct()
+    {
+        $this->pdo = Database::getInstance()->getPdo();
+    }
+
+    /**
+     * Check whether the given IP has exceeded the allowed number of attempts
+     * for an action within the time window.
+     */
+    public function isLimited(string $ip, string $action, int $maxAttempts, int $windowSeconds): bool
+    {
+        // Clean up old entries first so the table doesn't grow forever
+        $this->purge($action, $windowSeconds);
+
+        $stmt = $this->pdo->prepare(
+            'SELECT COUNT(*) FROM rate_limits
+             WHERE ip = :ip AND action = :action
+             AND attempted_at > DATE_SUB(NOW(), INTERVAL :window SECOND)'
+        );
+        $stmt->execute(['ip' => $ip, 'action' => $action, 'window' => $windowSeconds]);
+
+        return (int) $stmt->fetchColumn() >= $maxAttempts;
+    }
+
+    /**
+     * Record an attempt for the given IP and action.
+     */
+    public function record(string $ip, string $action): void
+    {
+        $stmt = $this->pdo->prepare(
+            'INSERT INTO rate_limits (ip, action) VALUES (:ip, :action)'
+        );
+        $stmt->execute(['ip' => $ip, 'action' => $action]);
+    }
+
+    /**
+     * Remove entries older than the window so the table stays small.
+     */
+    private function purge(string $action, int $windowSeconds): void
+    {
+        $stmt = $this->pdo->prepare(
+            'DELETE FROM rate_limits
+             WHERE action = :action
+             AND attempted_at <= DATE_SUB(NOW(), INTERVAL :window SECOND)'
+        );
+        $stmt->execute(['action' => $action, 'window' => $windowSeconds]);
+    }
+}