fuchsia_cprng/
lib.rs

1// Copyright 2019 The Fuchsia Authors. All rights reserved.
2// Use of this source code is governed by a BSD-style license that can be
3// found in the LICENSE file.
4
5//! Type-safe bindings for the Zircon kernel's CPRNG.
6
7#![no_std]
8#![deny(warnings)]
9
10/// Draw random bytes from the kernel's CPRNG to fill the given buffer.
11///
12/// Wraps the
13/// [zx_cprng_draw](https://fuchsia.googlesource.com/fuchsia/+/master/zircon/docs/syscalls/cprng_draw.md)
14/// syscall.
15pub fn cprng_draw(buffer: &mut [u8]) {
16    unsafe { zx_cprng_draw(buffer.as_mut_ptr(), buffer.len()) };
17}
18
19#[link(name = "zircon")]
20extern "C" {
21    fn zx_cprng_draw(buffer: *mut u8, length: usize);
22}
23
24#[cfg(test)]
25mod tests {
26    use super::*;
27
28    #[test]
29    fn cprng() {
30        let mut buffer = [0; 20];
31        cprng_draw(&mut buffer);
32        let mut first_zero = 0;
33        let mut last_zero = 0;
34        for _ in 0..30 {
35            let mut buffer = [0; 20];
36            cprng_draw(&mut buffer);
37            if buffer[0] == 0 {
38                first_zero += 1;
39            }
40            if buffer[19] == 0 {
41                last_zero += 1;
42            }
43        }
44        assert_ne!(first_zero, 30);
45        assert_ne!(last_zero, 30);
46    }
47
48    #[test]
49    fn cprng_large() {
50        let mut buffer = [0; 1024];
51        cprng_draw(&mut buffer);
52
53        for mut s in buffer.chunks_mut(256) {
54            cprng_draw(&mut s);
55        }
56    }
57}
fuchsia_cprng/lib.rs

fuchsia_cprng/
lib.rs
