Improper resource allocation - PHP

Improper resource allocation - PHP

Need

Efficient resource allocation and management

Context

  • Requirement of PHP 7.0 or later for executing the code
  • Usage of Request for making HTTP requests
  • Usage of SomeExpensiveResource for accessing a resource that requires high computational or financial costs

Description

Non compliant code

        public function processUserRequest(Request $request) {
    $data = $request->all();
    $items = [];

    for ($i = 0; $i < $data['count']; $i++) {
        $items[] = new SomeExpensiveResource();
    }

    // Do something with $items

    return response()->json(['status' => 'success']);
}

The above code is a method in a Laravel controller that processes a user request. It retrieves all data from the request and stores it in the $data variable. It then initializes an empty array $items.

Following this, the method enters a for loop, which runs for the number of times specified in $data['count']. In each iteration of the loop, it creates a new instance of SomeExpensiveResource class and adds it to the $items array.

The problem here is that the count of resource allocation is directly controlled by user input ( $data['count']). This means a user could potentially send a request with a very high count value, causing the system to allocate an enormous amount of SomeExpensiveResource instances, which could consume a significant amount of system resources, slowing down the system, or even causing a system crash if the number is large enough.

This is an example of an Improper Resource Allocation vulnerability as the system does not implement any restrictions or limitations on the amount of resources that can be allocated based on user input.

Steps

  • Validate the 'count' parameter to ensure it's within an acceptable range before using it in the loop. This prevents the allocation of an excessive number of resources.
  • Implement a limit for the maximum number of resources that can be allocated at once. This limit should be based on the system's capacity.
  • Consider using a more efficient data structure or algorithm if the current one is causing unnecessary resource allocation.
  • If the 'SomeExpensiveResource' objects are not required immediately, consider using lazy loading or a similar technique to delay their creation until they are actually needed.
  • Free up resources as soon as they are no longer needed to ensure efficient use of system resources.

Compliant code

        public function processUserRequest(Request $request) {
    $data = $request->all();

    // Validate 'count' parameter
    $count = isset($data['count']) && is_numeric($data['count']) ? intval($data['count']) : 0;
    $maxCount = 100; // Set a limit for the maximum number of resources that can be allocated at once

    if ($count > $maxCount) {
        return response()->json(['status' => 'error', 'message' => 'Request exceeds maximum limit.']);
    }

    $items = [];

    for ($i = 0; $i < $count; $i++) {
        $items[] = new SomeExpensiveResource();
    }

    // Do something with $items

    // Free up resources
    $items = null;

    return response()->json(['status' => 'success']);
}

The updated code includes several improvements to address the improper resource allocation vulnerability:

1. Input Validation: The 'count' parameter is validated to ensure it is numeric. If it's not set or not numeric, it defaults to 0.

2. Limiting Resource Allocation: A maximum limit for the number of resources that can be allocated at once is set. If the 'count' parameter exceeds this limit, an error response is returned.

3. Efficient Resource Usage: The 'SomeExpensiveResource' objects are created within the loop based on the 'count' parameter. This ensures that only the required number of resources are allocated.

4. Resource Deallocation: After the 'items' array is no longer needed, it is set to null. This allows the garbage collector to free up the memory used by these objects, ensuring efficient use of system resources.

These changes ensure that the system's resources are used efficiently and prevent potential Denial of Service (DoS) attacks that could occur if an attacker were able to cause the allocation of an excessive number of resources.

References