Struct ZeroDrop

pub struct ZeroDrop<T>(/* private fields */)
where
    T: Copy;

Zeroing drop wrapper type for Copy type.

Assuming T: Copy, a ZeroDrop<T> wraps a Box<T> and zeros it when dropped. We must use Box because LLVM moves data on the stack willy nilly.

let p : *const [u8; 32];
let s = zerodrop::ZeroDrop::new_copy(&[3u8; 32]);  
p = &*s;
std::mem::drop(s);
unsafe { assert_eq!(*p,[0u8; 32]); }

We recommend abstracting usage of ZeroDrop as follows because ZeroDrop does not mlock data.

type Secret<T> = ZeroDrop<T> where T: Copy+Default;

We similarly encurage wrapping ZeroDrop yourself so as to limit where and how secret data can be used in your code, including avoiding any trait magic that seems overly subtle.

struct MySecret(pub ZeroDrop<[u8; 32]>);

Implementations

impl<T> ZeroDrop<T>

where T: Copy,

Create a ZeroDrop<T> for a T: Copy consisting of a Box<T> that will be zeroed when dropped.

pub fn new_insecure(t: T) -> ZeroDrop<T>

Insecure as t likely gets placed on the stack

pub fn new_box(b: Box<T>) -> ZeroDrop<T>

Use provided Box<T>

pub unsafe fn new_uninitialized() -> ZeroDrop<T>

Secure but unsafe

pub fn new_copy(t: &T) -> ZeroDrop<T>

Allocate box and copy data into it from reference

pub unsafe fn zero_out(&mut self)

pub fn new_zeroed() -> ZeroDrop<T>

Trait Implementations

impl<T> AsMut<T> for ZeroDrop<T>

where T: Copy,

Delegate AsMut<_> to Box

fn as_mut(&mut self) -> &mut T

Converts this type into a mutable reference of the (usually inferred) input type.

impl<T> AsRef<T> for ZeroDrop<T>

where T: Copy,

Delegate AsRef<_> to Box

fn as_ref(&self) -> &T

Converts this type into a shared reference of the (usually inferred) input type.

impl<T> Borrow<T> for ZeroDrop<T>

where T: Copy,

Delegate Borrow<_> to Box

fn borrow(&self) -> &T

Immutably borrows from an owned value.

impl<T> BorrowMut<T> for ZeroDrop<T>

where T: Copy,

Delegate BorrowMut<_> to Box

fn borrow_mut(&mut self) -> &mut T

Mutably borrows from an owned value.

impl<T> Clone for ZeroDrop<T>

where T: Copy,

Clone the underlying Box

fn clone(&self) -> ZeroDrop<T>

Returns a copy of the value.

fn clone_from(&mut self, source: &ZeroDrop<T>)

Performs copy-assignment from source.

impl<T> Debug for ZeroDrop<T>

where T: Copy + Debug,

fn fmt(&self, f: &mut Formatter<'_>) -> Result

Formats the value using the given formatter.

impl<T> Default for ZeroDrop<T>

where T: Copy + Default,

fn default() -> ZeroDrop<T>

Returns the “default value” for a type.

impl<T> Deref for ZeroDrop<T>

where T: Copy,

Delegate Deref to Box

type Target = T

The resulting type after dereferencing.

fn deref(&self) -> &T

Dereferences the value.

impl<T> DerefMut for ZeroDrop<T>

where T: Copy,

Delegate DerefMut to Box

fn deref_mut(&mut self) -> &mut T

Mutably dereferences the value.

impl<T> Drop for ZeroDrop<T>

where T: Copy,

Zero a ZeroDrop<T> when dropped.

fn drop(&mut self)

Executes the destructor for this type.