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Improper resource allocation

Need​

Efficient resource allocation and management

Context​

  • Usage of Swift for iOS and macOS app development
  • Usage of UIKit for building modern and responsive user interfaces

Description​

Non compliant code​

import UIKit

class ViewController: UIViewController {
    
    var data: [String] = []
    
    override func viewDidLoad() {
        super.viewDidLoad()
        
        for _ in 0..<Int.max {
            data.append("This is a memory leak")
        }
    }
}

In the above Swift code for an iOS application, we are allocating resources improperly which can lead to a memory leak.

In the viewDidLoad() function, we are appending a string "This is a memory leak" to the data array for Int.max times. Int.max is the maximum representable integer in Swift, which is a very large number. This means we are creating a huge number of strings and storing them in the data array. This will consume an enormous amount of memory and can cause the application to crash due to out of memory error.

This is a clear example of improper resource allocation, where resources (memory, in this case) are allocated unnecessarily and inefficiently. This can be exploited by an attacker to cause a Denial of Service (DoS) attack by consuming all available memory resources.

Steps​

  • Identify the unnecessary resource allocation in the code.
  • Review the algorithm or programming practices that lead to the excessive resource allocation.
  • Optimize the algorithm or programming practices to reduce resource consumption.
  • Implement proper resource management techniques, such as releasing unused resources or deallocating memory.
  • Consider using lazy loading or pagination techniques to load and process data in smaller chunks instead of loading everything at once.
  • Validate and sanitize any external inputs to prevent requests that consume excessive resources.
  • Implement rate limiting or other restrictions to control resource consumption by external requests.
  • Test the application thoroughly to ensure that the resource allocation is optimized and controlled.

Compliant code​

import UIKit

class ViewController: UIViewController {
    
    var data: [String] = []
    
    override func viewDidLoad() {
        super.viewDidLoad()
        
        // Limit the number of elements to a reasonable amount
        let limit = 1000
        for _ in 0..<limit {
            data.append("This is not a memory leak anymore")
        }
    }
    
    // Deallocate memory when the view controller is not in use
    deinit {
        data.removeAll()
    }
}

The original code was allocating an enormous amount of resources by appending a string to an array for Int.max times. This is an example of improper resource allocation, which can lead to memory leaks and application crashes.

The fixed code limits the number of elements to a reasonable amount (in this case, 1000). This reduces the amount of memory allocated and prevents the application from crashing due to excessive memory usage.

Additionally, the deinit method is used to deallocate memory when the view controller is not in use. This is a good practice for managing resources in Swift. When the ViewController instance is deallocated, the deinit method is called, and the data array is emptied, freeing up the memory it was using.

This fix addresses the vulnerability by optimizing the algorithm to reduce resource consumption and implementing proper resource management techniques. It's also important to note that any external inputs should be validated and sanitized to prevent requests that consume excessive resources. Furthermore, consider implementing rate limiting or other restrictions to control resource consumption by external requests.

References​

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