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Merge pull request #273 from dhardy/next-float
Small changes from experimental branch
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,141 @@ | ||
| // Copyright 2018 The Rust Project Developers. See the COPYRIGHT | ||
| // file at the top-level directory of this distribution and at | ||
| // https://rust-lang.org/COPYRIGHT. | ||
| // | ||
| // 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. | ||
|
|
||
| //! Entropy generator, or wrapper around external generators | ||
|
|
||
| use {RngCore, Error, impls}; | ||
| use {OsRng, JitterRng}; | ||
|
|
||
| /// An RNG provided specifically for seeding PRNGs. | ||
| /// | ||
| /// Where possible, `EntropyRng` retrieves random data from the operating | ||
| /// system's interface for random numbers ([`OsRng`]); if that fails it will | ||
| /// fall back to the [`JitterRng`] entropy collector. In the latter case it will | ||
| /// still try to use [`OsRng`] on the next usage. | ||
| /// | ||
| /// This is either a little slow ([`OsRng`] requires a system call) or extremely | ||
| /// slow ([`JitterRng`] must use significant CPU time to generate sufficient | ||
| /// jitter). It is recommended to only use `EntropyRng` to seed a PRNG (as in | ||
| /// [`thread_rng`]) or to generate a small key. | ||
| /// | ||
| /// [`OsRng`]: os/struct.OsRng.html | ||
| /// [`JitterRng`]: jitter/struct.JitterRng.html | ||
| /// [`thread_rng`]: fn.thread_rng.html | ||
| #[derive(Debug)] | ||
| pub struct EntropyRng { | ||
| rng: EntropySource, | ||
| } | ||
|
|
||
| #[derive(Debug)] | ||
| enum EntropySource { | ||
| Os(OsRng), | ||
| Jitter(JitterRng), | ||
| None, | ||
| } | ||
|
|
||
| impl EntropyRng { | ||
| /// Create a new `EntropyRng`. | ||
| /// | ||
| /// This method will do no system calls or other initialization routines, | ||
| /// those are done on first use. This is done to make `new` infallible, | ||
| /// and `try_fill_bytes` the only place to report errors. | ||
| pub fn new() -> Self { | ||
| EntropyRng { rng: EntropySource::None } | ||
| } | ||
| } | ||
|
|
||
| impl RngCore for EntropyRng { | ||
| 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]) { | ||
| self.try_fill_bytes(dest).unwrap_or_else(|err| | ||
| panic!("all entropy sources failed; first error: {}", err)) | ||
| } | ||
|
|
||
| fn try_fill_bytes(&mut self, dest: &mut [u8]) -> Result<(), Error> { | ||
| fn try_os_new(dest: &mut [u8]) -> Result<OsRng, Error> | ||
| { | ||
| let mut rng = OsRng::new()?; | ||
| rng.try_fill_bytes(dest)?; | ||
| Ok(rng) | ||
| } | ||
|
|
||
| fn try_jitter_new(dest: &mut [u8]) -> Result<JitterRng, Error> | ||
| { | ||
| let mut rng = JitterRng::new()?; | ||
| rng.try_fill_bytes(dest)?; | ||
| Ok(rng) | ||
| } | ||
|
|
||
| let mut switch_rng = None; | ||
| match self.rng { | ||
| EntropySource::None => { | ||
| let os_rng_result = try_os_new(dest); | ||
| match os_rng_result { | ||
| Ok(os_rng) => { | ||
| debug!("EntropyRng: using OsRng"); | ||
| switch_rng = Some(EntropySource::Os(os_rng)); | ||
| } | ||
| Err(os_rng_error) => { | ||
| warn!("EntropyRng: OsRng failed [falling back to JitterRng]: {}", | ||
| os_rng_error); | ||
| match try_jitter_new(dest) { | ||
| Ok(jitter_rng) => { | ||
| debug!("EntropyRng: using JitterRng"); | ||
| switch_rng = Some(EntropySource::Jitter(jitter_rng)); | ||
| } | ||
| Err(_jitter_error) => { | ||
| warn!("EntropyRng: JitterRng failed: {}", | ||
| _jitter_error); | ||
| return Err(os_rng_error); | ||
| } | ||
| } | ||
| } | ||
| } | ||
| } | ||
| EntropySource::Os(ref mut rng) => { | ||
| let os_rng_result = rng.try_fill_bytes(dest); | ||
| if let Err(os_rng_error) = os_rng_result { | ||
| warn!("EntropyRng: OsRng failed [falling back to JitterRng]: {}", | ||
| os_rng_error); | ||
| match try_jitter_new(dest) { | ||
| Ok(jitter_rng) => { | ||
| debug!("EntropyRng: using JitterRng"); | ||
| switch_rng = Some(EntropySource::Jitter(jitter_rng)); | ||
| } | ||
| Err(_jitter_error) => { | ||
| warn!("EntropyRng: JitterRng failed: {}", | ||
| _jitter_error); | ||
| return Err(os_rng_error); | ||
| } | ||
| } | ||
| } | ||
| } | ||
| EntropySource::Jitter(ref mut rng) => { | ||
| if let Ok(os_rng) = try_os_new(dest) { | ||
| debug!("EntropyRng: using OsRng"); | ||
| switch_rng = Some(EntropySource::Os(os_rng)); | ||
| } else { | ||
| return rng.try_fill_bytes(dest); // use JitterRng | ||
| } | ||
| } | ||
| } | ||
| if let Some(rng) = switch_rng { | ||
| self.rng = rng; | ||
| } | ||
| Ok(()) | ||
| } | ||
| } |
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