Category Archives: MacOS X Lion

On MacOS 10.7 dyld randomization

First article for the blog, let’s talk about something I had in mind for a while.
There has been a lot of talk about the introduced full ASLR on MacOS X Lion, so as soon as I had my hands on the OS I wanted to check which were the changes introduced.

Let’s start from the very beginning, Mach-O. In order to understand what are the differences introduced in Lion, we need to first give a look at a Mach-O built on two different OSes, we will take as a reference Snow Leopard. Let’s build this simple code for test:

int main()
  while (1) {}
  return 0;

If we compile that code on Lion, no specific option passed to gcc, we will notice a difference from the very same code compiled on Snow Leopard. The difference is the presence of the flag MH_PIE (Position Independent):
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