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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.
//! Implementation for Windows UWP targets. After deprecation of Windows XP
//! and Vista, this can supersede the `RtlGenRandom`-based implementation.
use crate::Error;
use core::{ffi::c_void, num::NonZeroU32, ptr};
const BCRYPT_USE_SYSTEM_PREFERRED_RNG: u32 = 0x00000002;
extern "system" {
fn BCryptGenRandom(
hAlgorithm: *mut c_void,
pBuffer: *mut u8,
cbBuffer: u32,
dwFlags: u32,
) -> u32;
}
pub fn getrandom_inner(dest: &mut [u8]) -> Result<(), Error> {
// Prevent overflow of u32
for chunk in dest.chunks_mut(u32::max_value() as usize) {
let ret = unsafe {
BCryptGenRandom(
ptr::null_mut(),
chunk.as_mut_ptr(),
chunk.len() as u32,
BCRYPT_USE_SYSTEM_PREFERRED_RNG,
)
};
// NTSTATUS codes use two highest bits for severity status
match ret >> 30 {
0b01 => {
info!("BCryptGenRandom: information code 0x{:08X}", ret);
}
0b10 => {
warn!("BCryptGenRandom: warning code 0x{:08X}", ret);
}
0b11 => {
error!("BCryptGenRandom: failed with 0x{:08X}", ret);
// We zeroize the highest bit, so the error code will reside
// inside the range of 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 compiler
// is not smart enough to figure out it yet.
let code = unsafe { NonZeroU32::new_unchecked(code) };
return Err(Error::from(code));
}
_ => (),
}
}
Ok(())
}
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