/
windows.rs
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/
windows.rs
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// Copyright 2018 Developers of the Rand project.
//
// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
// https://www.apache.org/licenses/LICENSE-2.0> or the MIT license
// <LICENSE-MIT or https://opensource.org/licenses/MIT>, at your
// option. This file may not be copied, modified, or distributed
// except according to those terms.
use crate::{util::raw_chunks, Error};
use core::{ffi::c_void, num::NonZeroU32, ptr};
const BCRYPT_USE_SYSTEM_PREFERRED_RNG: u32 = 0x00000002;
#[link(name = "bcrypt")]
extern "system" {
fn BCryptGenRandom(
hAlgorithm: *mut c_void,
pBuffer: *mut u8,
cbBuffer: u32,
dwFlags: u32,
) -> u32;
}
pub unsafe fn getrandom_inner(dst: *mut u8, len: usize) -> Result<(), Error> {
// Prevent overflow of u32
raw_chunks(dst, len, u32::max_value() as usize, |cdst, clen| {
// BCryptGenRandom was introduced in Windows Vista
let ret = BCryptGenRandom(
ptr::null_mut(),
cdst,
clen as u32,
BCRYPT_USE_SYSTEM_PREFERRED_RNG,
);
// NTSTATUS codes use the two highest bits for severity status.
if ret >> 30 == 0b11 {
// We zeroize the highest bit, so the error code will reside
// inside the range designated for OS codes.
let code = ret ^ (1 << 31);
// SAFETY: the second highest bit is always equal to one,
// so it's impossible to get zero. Unfortunately the type
// system does not have a way to express this yet.
let code = NonZeroU32::new_unchecked(code);
Err(Error::from(code))
} else {
Ok(())
}
})
}