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Diffstat (limited to 'rand/rand_core/src/os.rs')
-rw-r--r-- | rand/rand_core/src/os.rs | 85 |
1 files changed, 85 insertions, 0 deletions
diff --git a/rand/rand_core/src/os.rs b/rand/rand_core/src/os.rs new file mode 100644 index 0000000..fc23a57 --- /dev/null +++ b/rand/rand_core/src/os.rs @@ -0,0 +1,85 @@ +// 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); +} |