86 lines
2.5 KiB
Rust
86 lines
2.5 KiB
Rust
// Copyright 2019 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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//! Interface to the random number generator of the operating system.
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// Note: keep this code in sync with the rand_os crate!
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use getrandom::getrandom;
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use crate::{CryptoRng, RngCore, Error, impls};
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/// A random number generator that retrieves randomness from from the
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/// operating system.
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///
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/// This is a zero-sized struct. It can be freely constructed with `OsRng`.
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///
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/// The implementation is provided by the [getrandom] crate. Refer to
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/// [getrandom] documentation for details.
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///
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/// This struct is only available when specifying the crate feature `getrandom`
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/// or `std`. When using the `rand` lib, it is also available as `rand::rngs::OsRng`.
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///
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/// # Blocking and error handling
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///
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/// It is possible that when used during early boot the first call to `OsRng`
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/// will block until the system's RNG is initialised. It is also possible
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/// (though highly unlikely) for `OsRng` to fail on some platforms, most
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/// likely due to system mis-configuration.
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///
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/// After the first successful call, it is highly unlikely that failures or
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/// significant delays will occur (although performance should be expected to
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/// be much slower than a user-space PRNG).
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///
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/// # Usage example
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/// ```
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/// use rand_core::{RngCore, OsRng};
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///
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/// let mut key = [0u8; 16];
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/// OsRng.fill_bytes(&mut key);
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/// let random_u64 = OsRng.next_u64();
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/// ```
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///
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/// [getrandom]: https://crates.io/crates/getrandom
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#[derive(Clone, Copy, Debug, Default)]
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pub struct OsRng;
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impl CryptoRng for OsRng {}
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impl RngCore for OsRng {
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fn next_u32(&mut self) -> u32 {
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impls::next_u32_via_fill(self)
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}
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fn next_u64(&mut self) -> u64 {
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impls::next_u64_via_fill(self)
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}
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fn fill_bytes(&mut self, dest: &mut [u8]) {
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if let Err(e) = self.try_fill_bytes(dest) {
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panic!("Error: {}", e);
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}
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}
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fn try_fill_bytes(&mut self, dest: &mut [u8]) -> Result<(), Error> {
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getrandom(dest)?;
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Ok(())
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}
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}
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#[test]
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fn test_os_rng() {
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let x = OsRng.next_u64();
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let y = OsRng.next_u64();
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assert!(x != 0);
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assert!(x != y);
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}
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#[test]
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fn test_construction() {
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let mut rng = OsRng::default();
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assert!(rng.next_u64() != 0);
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}
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