50 lines
1.7 KiB
Rust
50 lines
1.7 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, 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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pub fn getrandom_inner(dest: &mut [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(),
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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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// 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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