| 1 | // Copyright 2019 Developers of the Rand project. |
| 2 | // |
| 3 | // Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or |
| 4 | // https://www.apache.org/licenses/LICENSE-2.0> or the MIT license |
| 5 | // <LICENSE-MIT or https://opensource.org/licenses/MIT>, at your |
| 6 | // option. This file may not be copied, modified, or distributed |
| 7 | // except according to those terms. |
| 8 | |
| 9 | //! Interface to the random number generator of the operating system. |
| 10 | |
| 11 | use crate::{TryCryptoRng, TryRngCore}; |
| 12 | |
| 13 | /// An interface over the operating-system's random data source |
| 14 | /// |
| 15 | /// This is a zero-sized struct. It can be freely constructed with just `OsRng`. |
| 16 | /// |
| 17 | /// The implementation is provided by the [getrandom] crate. Refer to |
| 18 | /// [getrandom] documentation for details. |
| 19 | /// |
| 20 | /// This struct is available as `rand_core::OsRng` and as `rand::rngs::OsRng`. |
| 21 | /// In both cases, this requires the crate feature `os_rng` or `std` |
| 22 | /// (enabled by default in `rand` but not in `rand_core`). |
| 23 | /// |
| 24 | /// # Blocking and error handling |
| 25 | /// |
| 26 | /// It is possible that when used during early boot the first call to `OsRng` |
| 27 | /// will block until the system's RNG is initialised. It is also possible |
| 28 | /// (though highly unlikely) for `OsRng` to fail on some platforms, most |
| 29 | /// likely due to system mis-configuration. |
| 30 | /// |
| 31 | /// After the first successful call, it is highly unlikely that failures or |
| 32 | /// significant delays will occur (although performance should be expected to |
| 33 | /// be much slower than a user-space |
| 34 | /// [PRNG](https://rust-random.github.io/book/guide-gen.html#pseudo-random-number-generators)). |
| 35 | /// |
| 36 | /// # Usage example |
| 37 | /// ``` |
| 38 | /// use rand_core::{TryRngCore, OsRng}; |
| 39 | /// |
| 40 | /// let mut key = [0u8; 16]; |
| 41 | /// OsRng.try_fill_bytes(&mut key).unwrap(); |
| 42 | /// let random_u64 = OsRng.try_next_u64().unwrap(); |
| 43 | /// ``` |
| 44 | /// |
| 45 | /// [getrandom]: https://crates.io/crates/getrandom |
| 46 | #[derive (Clone, Copy, Debug, Default)] |
| 47 | pub struct OsRng; |
| 48 | |
| 49 | /// Error type of [`OsRng`] |
| 50 | #[derive (Clone, Copy, Debug, PartialEq, Eq)] |
| 51 | pub struct OsError(getrandom::Error); |
| 52 | |
| 53 | impl core::fmt::Display for OsError { |
| 54 | #[inline ] |
| 55 | fn fmt(&self, f: &mut core::fmt::Formatter<'_>) -> core::fmt::Result { |
| 56 | self.0.fmt(f) |
| 57 | } |
| 58 | } |
| 59 | |
| 60 | // NOTE: this can use core::error::Error from rustc 1.81.0 |
| 61 | #[cfg (feature = "std" )] |
| 62 | impl std::error::Error for OsError { |
| 63 | #[inline ] |
| 64 | fn source(&self) -> Option<&(dyn std::error::Error + 'static)> { |
| 65 | std::error::Error::source(&self.0) |
| 66 | } |
| 67 | } |
| 68 | |
| 69 | impl OsError { |
| 70 | /// Extract the raw OS error code (if this error came from the OS) |
| 71 | /// |
| 72 | /// This method is identical to [`std::io::Error::raw_os_error()`][1], except |
| 73 | /// that it works in `no_std` contexts. If this method returns `None`, the |
| 74 | /// error value can still be formatted via the `Display` implementation. |
| 75 | /// |
| 76 | /// [1]: https://doc.rust-lang.org/std/io/struct.Error.html#method.raw_os_error |
| 77 | #[inline ] |
| 78 | pub fn raw_os_error(self) -> Option<i32> { |
| 79 | self.0.raw_os_error() |
| 80 | } |
| 81 | } |
| 82 | |
| 83 | impl TryRngCore for OsRng { |
| 84 | type Error = OsError; |
| 85 | |
| 86 | #[inline ] |
| 87 | fn try_next_u32(&mut self) -> Result<u32, Self::Error> { |
| 88 | getrandom::u32().map_err(op:OsError) |
| 89 | } |
| 90 | |
| 91 | #[inline ] |
| 92 | fn try_next_u64(&mut self) -> Result<u64, Self::Error> { |
| 93 | getrandom::u64().map_err(op:OsError) |
| 94 | } |
| 95 | |
| 96 | #[inline ] |
| 97 | fn try_fill_bytes(&mut self, dest: &mut [u8]) -> Result<(), Self::Error> { |
| 98 | getrandom::fill(dest).map_err(op:OsError) |
| 99 | } |
| 100 | } |
| 101 | |
| 102 | impl TryCryptoRng for OsRng {} |
| 103 | |
| 104 | #[test ] |
| 105 | fn test_os_rng() { |
| 106 | let x = OsRng.try_next_u64().unwrap(); |
| 107 | let y = OsRng.try_next_u64().unwrap(); |
| 108 | assert!(x != 0); |
| 109 | assert!(x != y); |
| 110 | } |
| 111 | |
| 112 | #[test ] |
| 113 | fn test_construction() { |
| 114 | assert!(OsRng.try_next_u64().unwrap() != 0); |
| 115 | } |
| 116 | |