S4000 — Pointers to unmanaged memory should not be visible

Why is this an issue?

Pointer and unmanaged function pointer types such as IntPtr, UIntPtr, int* etc. are used to access unmanaged memory, usually in order to use C or C++ libraries. If such a pointer is not secured by making it private, internal or readonly, it can lead to a vulnerability allowing access to arbitrary locations.

Noncompliant code example

using System;

namespace MyLibrary
{
  public class MyClass
  {
    public IntPtr myPointer;  // Noncompliant
    protected UIntPtr myOtherPointer; // Noncompliant
  }
}

Compliant solution

using System;

namespace MyLibrary
{
  public class MyClass
  {
    private IntPtr myPointer;
    protected readonly UIntPtr myOtherPointer;
  }
}