c526c898b3
* Add in a RtlGenRandom fallback for non-UWP Windows In some instances BCryptRandom will fail when RtlGenRandom will work. On UWP, we might be unable to actually use RtlGenRandom. Thread the needle and use RtlGenRandom when we have to, when we're able. See also rust-lang/rust#108060 Fixes #314 * style suggestion Co-authored-by: Artyom Pavlov <newpavlov@gmail.com> * appease clippy --------- Co-authored-by: Artyom Pavlov <newpavlov@gmail.com>
67 lines
2.3 KiB
Rust
67 lines
2.3 KiB
Rust
// Copyright 2018 Developers of the Rand project.
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//
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// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
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// https://www.apache.org/licenses/LICENSE-2.0> or the MIT license
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// <LICENSE-MIT or https://opensource.org/licenses/MIT>, at your
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// option. This file may not be copied, modified, or distributed
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// except according to those terms.
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use crate::Error;
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use core::{ffi::c_void, mem::MaybeUninit, num::NonZeroU32, ptr};
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const BCRYPT_USE_SYSTEM_PREFERRED_RNG: u32 = 0x00000002;
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#[link(name = "bcrypt")]
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extern "system" {
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fn BCryptGenRandom(
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hAlgorithm: *mut c_void,
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pBuffer: *mut u8,
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cbBuffer: u32,
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dwFlags: u32,
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) -> u32;
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}
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// Forbidden when targetting UWP
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#[cfg(not(target_vendor = "uwp"))]
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#[link(name = "advapi32")]
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extern "system" {
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#[link_name = "SystemFunction036"]
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fn RtlGenRandom(RandomBuffer: *mut c_void, RandomBufferLength: u32) -> u8;
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}
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pub fn getrandom_inner(dest: &mut [MaybeUninit<u8>]) -> Result<(), Error> {
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// Prevent overflow of u32
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for chunk in dest.chunks_mut(u32::max_value() as usize) {
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// BCryptGenRandom was introduced in Windows Vista
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let ret = unsafe {
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BCryptGenRandom(
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ptr::null_mut(),
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chunk.as_mut_ptr() as *mut u8,
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chunk.len() as u32,
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BCRYPT_USE_SYSTEM_PREFERRED_RNG,
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)
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};
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// NTSTATUS codes use the two highest bits for severity status.
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if ret >> 30 == 0b11 {
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// Failed. Try RtlGenRandom as a fallback.
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#[cfg(not(target_vendor = "uwp"))]
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{
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let ret =
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unsafe { RtlGenRandom(chunk.as_mut_ptr() as *mut c_void, chunk.len() as u32) };
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if ret != 0 {
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continue;
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}
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}
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// We zeroize the highest bit, so the error code will reside
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// inside the range designated for OS codes.
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let code = ret ^ (1 << 31);
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// SAFETY: the second highest bit is always equal to one,
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// so it's impossible to get zero. Unfortunately the type
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// system does not have a way to express this yet.
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let code = unsafe { NonZeroU32::new_unchecked(code) };
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return Err(Error::from(code));
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}
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}
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Ok(())
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}
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