y0QDb99w

1#![feature(maybe_uninit)]
2
3mod ralloc {
4    use ::std::{
5        mem::MaybeUninit,
6        ops::{Deref, DerefMut},
7        ptr,
8    };
9
10    pub struct ZeroDropBox<T> /* = */ (Box< MaybeUninit<T> >);
11
12    impl<T> Drop for ZeroDropBox<T>
13    {
14        fn drop (
15        self: &mut Self,
16        )
17        { unsafe {
18            ptr::drop_in_place(self.0.as_mut_ptr());
19            ptr::write_volatile(
20              Box::deref_mut(&mut self.0),
21              MaybeUninit::zeroed(),
22            );
23            // we could even go as far as to zero the pointer itself ...
24        }}
25    }
26    
27    impl<T> From<T> for ZeroDropBox<T>
28    {
29        #[inline(always)]
30        fn from (inline_value: T) -> Self
31        {
32            ZeroDropBox(
33                Box::new(
34                    MaybeUninit::new(
35                        inline_value
36                    )
37                )
38            )
39        }
40    }
41    
42    impl<T> Deref for ZeroDropBox<T>
43    {
44        type Target = T;
45        
46        #[inline]
47        fn deref (
48            self: &Self,
49        ) -> &Self::Target
50        { unsafe {
51            self.0.get_ref()
52        }}
53    }
54    impl<T> DerefMut for ZeroDropBox<T>
55    {
56        #[inline]
57        fn deref_mut (
58            self: &mut Self,
59        ) -> &mut Self::Target
60        { unsafe {
61            self.0.get_mut()
62        }}
63    }
64}
65pub use self::ralloc::ZeroDropBox;
66
67fn main ()
68{
69    let secret_key = ZeroDropBox::from([42_u8; 16]);
70    dbg!(&secret_key as &[u8; 16]);
71    let secret_key_after_free: &[u8; 16] = unsafe {
72        &*(&secret_key as &[u8; 16] as *const _)
73    };
74    ::std::mem::drop(secret_key);
75    dbg!(secret_key_after_free);
76}