README

This is a library for rate-limiting both brute-force attempts (like invalid credentials) and ordinary requests.

Features

• can be used to limit brute-force attempts;
• can be used for request rate limiting;
• uses leaky / token bucket algorithm. This means that user does not have to wait for next hour or day - additional attempts are possible as time goes by. This also means that requests does not come in big batches when every hour starts;
• handles race-conditions. This is important for brute-force limiting. For example, if 1000 requests are issued at the same time to check same user's password, only configured number of attempts will be possible;
• can have several limits configured for single use-case (for example maximum of 100 requests per minute and 200 per hour);
• does not make assumptions about where and what it's used for - it can be used with user identifiers, API tokens, IP addresses or any other data to group usages.

Installation

composer require maba/gentle-force

Usage

<?php

use Maba\GentleForce\RateLimit\UsageRateLimit;
use Maba\GentleForce\RateLimitProvider;
use Maba\GentleForce\Throttler;
use Maba\GentleForce\Exception\RateLimitReachedException;

$rateLimitProvider = new RateLimitProvider();
$rateLimitProvider->registerRateLimits('credentials_error', [
    // allow 3 errors per hour; 2 additional errors if no errors were made during last hour
    (new UsageRateLimit(3, 3600))->setBucketedUsages(2),
    // allow 10 errors per day
    new UsageRateLimit(10, 3600 * 24),
]);
$rateLimitProvider->registerRateLimits('api_request', [
    // - allow 10 requests each minute;
    // - user can "save up" hour of usage if not using API.
    //   This means up to 610 requests at once, after that - 10 requests per minute,
    //   which could again save-up up to 610.
    (new UsageRateLimit(10, 60))->setBucketedPeriod(3600),
]);

$throttler = new Throttler(new \Predis\Client([
    'host' => '127.0.0.1',
]), $rateLimitProvider);

// rate limiting:
try {
    $result = $throttler->checkAndIncrease('api_request', $_SERVER['REMOTE_ADDR']);
    header('Requests-Available', $result->getUsagesAvailable());
    
} catch (RateLimitReachedException $exception) {
    header('Wait-For', $exception->getWaitForInSeconds(), 429);
    return;
}

// brute-force limiting:
try {
    // we must increase error count in-advance before even checking credentials
    // this avoids race-conditions with lots of requests
    $credentialsResult = $throttler->checkAndIncrease('credentials_error', $_POST['username']);
} catch (RateLimitReachedException $exception) {
    echo sprintf('Too much password tries for user. Please try after %s seconds', $exception->getWaitForInSeconds());
    return;
}

$credentialsValid = checkCredentials($_POST['username'], $_POST['password']);

if ($credentialsValid) {
    // as we've increased error count in advance, we need to decrease it if everything went fine
    $credentialsResult->decrease();
    
    // log user into system
}

Alternatives

Actually, there are quite many of them.

Unfortunately, as some provide additional features (like different storage methods: file, memcached etc.), none were found with these criteria:

• usable for brute-forcing (only on errors), not for all requests;
• abstract, so that limiting by user, IP and other identifiers would be possible;
• rate limiting algorithm that would not block for too long for a legitimate user;
• free of race-conditions where actual limit would not work correctly on high load.

Some of reviewed alternatives: RateLimitInterface, rate-limiter, LosRateLimit, Rate-limit, rate-limit, php-ratelimiter, tokenbucket, brute-force, LoginGateBundle, tresholds-governor, throttle, PeerjUserSecurityBundle, php-ratelimiter, RateLimitBundle, CybBotDetectBunble, CCDNUserSecurityBundle, limit-number-calls-bundle, rate-limiter-php, flaps, token-bucket

Semantic versioning

This library follows semantic versioning.

See Symfony BC rules for basic information about what can be changed and what not in the API.

Running tests

Functional tests require Redis and several PHP extensions for forking, so that behaviour on high traffic could be tested. So, generally, it's easier to run them in docker.

composer update
cd docker
docker-compose up -d
docker exec -it gentle_force_test_php vendor/bin/phpunit
docker-compose down

Contributing

Feel free to create issues and give pull requests.

You can fix any code style issues using this command:

vendor/bin/php-cs-fixer fix --config=.php_cs