可能将内存数据从一个ios应用泄漏到另一个？

Question

Preface: I'm not an iOS developer and know next to nothing about the iOS security model. So forgive me if this question is truly dumb. :)

Consider an app, called MyApp, that does the following when launched:

1. Dynamically allocates a chunk of memory, say using malloc().
2. Loads some sensitive data over the network and stores it in that chunk of memory.
3. Sits there doing nothing.

Now consider the following scenario:

1. User launches MyApp.
2. User closes MyApp.
3. User launches SomeOtherApp.

My question: If SomeOtherApp also dynamically allocates memory is it possible that one of the buffers returned by the OS will contain the sensitive data placed there by the (now closed) invocation of MyApp?

Or are the contents of RAM treated as part of the sandbox in which an app runs?

Answer 1

Theoretically once the user closes the app (you have to make sure that the app is closed and not just running in the background) the memory that was allocated to that process is deallocated and returned.

To quote from a tutorial on ARC:

"With Automatic Reference Counting enabled, the compiler will automatically insert retain, release and autorelease in the correct places in your program. You no longer have to worry about any of this, because the compiler does it for you."

So when an app closes, all references to any objects which had some sort of memory allocation will be cleared because there will be no objects to reference when the app is not running.

The reason that I say that you have to make sure that it is closed is because some apps, by default, will not close when you press the home button, but will in fact continue to run in the background. This might cause a potential security threat, but unlikely. To ensure that NO memory is still being held on to by that app, make sure that it actually fully closes each time. Make sure that the code is done right and that the person who is writing it, knows and is keeping track of the memory that he allocates.

If security is a big issue, then make sure that all of the memory that does get allocated get properly deallocated in your code. Then make sure that you do an insane amount of testing for memory leaks and whatnot to make sure that no object is left lying with some amount of memory.

I would just like to say that I am not a professional on memory management of even ARC, so it would be best to check with a couple other sources to ensure that my answer is correct.

If I have spoken in err, someone hit me.