RtlGenRandom on Windows uses the wrong ABI

[cakarsubasi]

I ran into this issue while while running rdst with miri. The RtlGenRandom function has the following definition:

BOOLEAN RtlGenRandom(
  [out] PVOID RandomBuffer,
  [in]  ULONG RandomBufferLength
);

Which was translated as follows:

fn RtlGenRandom(pBuffer: *mut u8, cbBuffer: usize) -> u32;

However, an ULONG on Windows is 4 bytes long, not pointer sized, and a BOOLEAN (not to be confused with a BOOL) is 1 byte long.

So, the updated signature plus the entropy function in the file should be like this:

use core::ffi::{c_void, c_ulong, c_char};

extern "system" {
	#[link_name = "SystemFunction036"]
	fn RtlGenRandom(pBuffer: *mut c_void, cbBuffer: c_ulong) -> c_char;
}

/// Obtain a random 64-bit number using WinAPI's `RtlGenRandom` function.
pub fn entropy(out: &mut [u8]) -> bool {
	unsafe { RtlGenRandom(out.as_mut_ptr() as *mut c_void, out.len() as u32) == 0 }
}