1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85
// Copyright 2019 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. //! Interface to the random number generator of the operating system. // Note: keep this code in sync with the rand_os crate! use getrandom::getrandom; use crate::{CryptoRng, RngCore, Error, impls}; /// A random number generator that retrieves randomness from from the /// operating system. /// /// This is a zero-sized struct. It can be freely constructed with `OsRng`. /// /// The implementation is provided by the [getrandom] crate. Refer to /// [getrandom] documentation for details. /// /// This struct is only available when specifying the crate feature `getrandom` /// or `std`. When using the `rand` lib, it is also available as `rand::rngs::OsRng`. /// /// # Blocking and error handling /// /// It is possible that when used during early boot the first call to `OsRng` /// will block until the system's RNG is initialised. It is also possible /// (though highly unlikely) for `OsRng` to fail on some platforms, most /// likely due to system mis-configuration. /// /// After the first successful call, it is highly unlikely that failures or /// significant delays will occur (although performance should be expected to /// be much slower than a user-space PRNG). /// /// # Usage example /// ``` /// use rand_core::{RngCore, OsRng}; /// /// let mut key = [0u8; 16]; /// OsRng.fill_bytes(&mut key); /// let random_u64 = OsRng.next_u64(); /// ``` /// /// [getrandom]: https://crates.io/crates/getrandom #[derive(Clone, Copy, Debug, Default)] pub struct OsRng; impl CryptoRng for OsRng {} impl RngCore for OsRng { fn next_u32(&mut self) -> u32 { impls::next_u32_via_fill(self) } fn next_u64(&mut self) -> u64 { impls::next_u64_via_fill(self) } fn fill_bytes(&mut self, dest: &mut [u8]) { if let Err(e) = self.try_fill_bytes(dest) { panic!("Error: {}", e); } } fn try_fill_bytes(&mut self, dest: &mut [u8]) -> Result<(), Error> { getrandom(dest)?; Ok(()) } } #[test] fn test_os_rng() { let x = OsRng.next_u64(); let y = OsRng.next_u64(); assert!(x != 0); assert!(x != y); } #[test] fn test_construction() { let mut rng = OsRng::default(); assert!(rng.next_u64() != 0); }