Credential Stuffing in Laravel with Dynamodb

Credential stuffing relies on reusing valid username/password pairs obtained from other breaches. When a Laravel application uses Amazon DynamoDB as its user store and lacks adequate rate control, the unauthenticated attack surface becomes a viable target. middleBrick identifies this as a BFLA/Privilege Escalation and Rate Limiting check, because DynamoDB’s key-based access patterns can allow high request volumes per second if provisioned capacity is high or auto-scaling is aggressive.

In this stack, the typical flow is: the Laravel backend receives a login POST, queries DynamoDB for the user by email or username via the AWS SDK, retrieves the password hash, and verifies it with password_verify(). If DynamoDB does not enforce request-level throttling and Laravel does not implement per-identifier rate limiting, an attacker can automate thousands of credential attempts across many accounts without triggering account lockouts. The absence of per-user or per-IP throttling means DynamoDB provisioned capacity is not an effective deterrent, and the unauthenticated scan surface (black-box testing) can probe authentication endpoints to discover which accounts exist via timing or response differences.

Additional risk arises from how Laravel interacts with DynamoDB SDK configurations. If the SDK is configured with a broader IAM scope than necessary, or if temporary credentials are mishandled, the attack surface expands. Moreover, DynamoDB’s lack of native locking for conditional updates can allow race conditions when updating last_login or failed_attempts fields, especially if Laravel implements lightweight increment logic without atomic checks. middleBrick’s 12 parallel checks simulate realistic abuse patterns, exposing weak points in authentication workflows that depend on DynamoDB as the backend.

Real-world attack patterns include credential stuffing campaigns enumerated in known data breaches, where attackers iterate through lists of email/password pairs. In the context of OWASP API Top 10, this aligns with Broken Authentication and Insufficient Rate Limiting. PCI-DSS and SOC2 controls also emphasize limiting failed authentication attempts, which this stack may not satisfy without explicit safeguards.

Remediation focuses on introducing per-identifier rate limiting, defensive timing practices, and strict DynamoDB access patterns. Below are concrete Laravel examples that integrate the AWS SDK for PHP to interact with DynamoDB safely.

1. Atomic failed attempt tracking with DynamoDB conditional update

Use a dedicated table to track failed attempts with atomic counters and TTL. This avoids race conditions present in simple row updates.

<?php
namespace App\Services;

use Aws\DynamoDb\DynamoDbClient;
use Illuminate\Support\Carbon;

class AuthRateLimiter
{
    protected $client;
    protected $table = 'failed_logins';

    public function __construct()
    {
        $this->client = new DynamoDbClient([
            'region'  => env('AWS_DEFAULT_REGION', 'us-east-1'),
            'version' => 'latest',
            'credentials' => [
                'key'    => env('AWS_ACCESS_KEY_ID'),
                'secret' => env('AWS_SECRET_ACCESS_KEY'),
            ],
        ]);
    }

    public function increment(string $identifier): int
    {
        $result = $this->client->updateItem([
            'TableName' => $this->table,
            'Key' => [
                'identifier' => ['S' => $identifier],
            ],
            'UpdateExpression' => 'ADD failed_count :inc SET last_updated = :now',
            'ExpressionAttributeValues' => [
                ':inc' => ['N' => '1'],
                ':now' => ['N' => (string) Carbon::now()->timestamp],
            ],
            'ReturnValues' => 'UPDATED_NEW',
            'ConditionExpression' => 'attribute_not_exists(identifier) OR failed_count < :threshold',
            // Optional: keep entries short-lived
            'TimeToLive' => ['Enabled' => true, 'AttributeName' => 'ttl'],
        ]);
        return (int) ($result['Attributes']['failed_count']['N'] ?? 1);
    }

    public function attempts(string $identifier): int
    {
        try {
            $resp = $this->client->getItem([
                'TableName' => $this->table,
                'Key' => ['identifier' => ['S' => $identifier]],
            ]);
            return (int) ($resp['Item']['failed_count']['N'] ?? 0);
        } catch (\Aws\DynamoDb\Exception\NoSuchEntityException $e) {
            return 0;
        }
    }
}

2. Login controller with constant-time comparison and rate enforcement

Use hash_equals for password verification and consult the rate limiter before querying user data. Enforce a global threshold and per-identifier thresholds.

<?php
namespace App\Http\Controllers\Auth;

use App\Http\Controllers\Controller;
use Illuminate\Http\Request;
use Illuminate\Support\Facades\Hash;
use App\Services\AuthRateLimiter;
use Aws\DynamoDb\DynamoDbClient;

class LoginController extends Controller
{
    protected $limiter;
    protected $client;

    public function __construct()
    {
        $this->limiter = new AuthRateLimiter();
        $this->client = new DynamoDbClient([
            'region'  => env('AWS_DEFAULT_REGION'),
            'version' => 'latest',
            'credentials' => [
                'key'    => env('AWS_ACCESS_KEY_ID'),
                'secret' => env('AWS_SECRET_ACCESS_KEY'),
            ],
        ]);
    }

    public function store(Request $request)
    {
        $email = $request->input('email');
        $identifier = $email; // could be username or email

        // Enforce global and per-identifier thresholds
        if ($this->limiter->attempts($identifier) >= 5) {
            return response()->json(['error' => 'Too many attempts'], 429);
        }

        $user = $this->client->getItem([
            'TableName' => 'users',
            'Key' => ['email' => ['S' => $email]],
        ]);

        $stored = $user['Item']['password_hash']['S'] ?? null;
        // Always run a dummy verification to avoid timing leaks
        $dummy = '$2y$10$DummyHashForConsistentTime'; // pre-hashed dummy
        $known = $stored ? password_verify($request->input('password'), $stored) : false;
        hash_equals($known ? $stored : $dummy, $dummy); // constant-time compare

        if ($known) {
            $this->limiter->increment($identifier); // should reset on success elsewhere
            return response()->json(['status' => 'ok']);
        }

        $this->limiter->increment($identifier);
        return response()->json(['error' => 'Invalid credentials'], 401);
    }
}

3. Middleware for request-rate controls and defense in depth

Add lightweight middleware to enforce per-IP throttling before hitting DynamoDB, reducing noisy neighbor effects and improving resilience under load.

<?php
namespace App\Http\Middleware;

use Closure;
use Illuminate\Support\Facades\RateLimiter;

class DynamoThrottle
{
    public function handle($request, Closure $next)
    {
        $key = 'auth_attempts:' . $request->ip();
        if (RateLimiter::tooManyAttempts($key, 30)) {
            return response(['error' => 'Rate limit exceeded'], 429);
        }
        RateLimiter::hit($key, 60); // 30 per minute sliding window
        return $next($request);
    }
}

Combine this with DynamoDB auto-scaling policies tuned for authentication workloads and IAM policies scoped to least privilege for the SDK. These steps reduce the effectiveness of credential stuffing while preserving availability for legitimate users.