Question

I am writing a stream that needs to be aligned to a particular size. What is the right way of appending null (or any value) without exposing sensitive areas of RAM outside Array.Copy?

For example, I need to “round up” byteArray.Length to the value of pad:

 byte[] byteArray = Encoding.ASCII.GetBytes(preStream);
 long pad = (minBlobEntrySize * databaseCount) - byteArray.Length;
 Array.Copy(byteArray, 0, buffer, relativeOffset2, byteArray.Length);

And I know that the following is wrong since it may expose sensitive data:

  Array.Copy(byteArray, 0, buffer, relativeOffset2, byteArray.Length + pad);

What is the correct way to handle this?

Answer 1

Looks like the Array.Resize method should do what you want here.

byte[] byteArray = Encoding.ASCII.GetBytes(preStream);
long pad = (minBlobEntrySize * databaseCount) - byteArray.Length;
Array.Resize(ref byteArray, byteArray.Length + pad);
Array.Copy(byteArray, 0, buffer, relativeOffset2, byteArray.Length);

Note that you don’t need the + pad in the Copy method as the length will be the resized one.