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use rand_core::{RngCore, CryptoRng, Error, ErrorKind, impls};
#[allow(unused)]
use rngs;
#[derive(Debug)]
pub struct EntropyRng {
source: Source,
}
#[derive(Debug)]
enum Source {
Os(Os),
Custom(Custom),
Jitter(Jitter),
None,
}
impl EntropyRng {
pub fn new() -> Self {
EntropyRng { source: Source::None }
}
}
impl Default for EntropyRng {
fn default() -> Self {
EntropyRng::new()
}
}
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> {
let mut reported_error = None;
if let Source::Os(ref mut os_rng) = self.source {
match os_rng.fill(dest) {
Ok(()) => return Ok(()),
Err(err) => {
warn!("EntropyRng: OsRng failed \
[trying other entropy sources]: {}", err);
reported_error = Some(err);
},
}
} else if Os::is_supported() {
match Os::new_and_fill(dest) {
Ok(os_rng) => {
debug!("EntropyRng: using OsRng");
self.source = Source::Os(os_rng);
return Ok(());
},
Err(err) => { reported_error = reported_error.or(Some(err)) },
}
}
if let Source::Custom(ref mut rng) = self.source {
match rng.fill(dest) {
Ok(()) => return Ok(()),
Err(err) => {
warn!("EntropyRng: custom entropy source failed \
[trying other entropy sources]: {}", err);
reported_error = Some(err);
},
}
} else if Custom::is_supported() {
match Custom::new_and_fill(dest) {
Ok(custom) => {
debug!("EntropyRng: using custom entropy source");
self.source = Source::Custom(custom);
return Ok(());
},
Err(err) => { reported_error = reported_error.or(Some(err)) },
}
}
if let Source::Jitter(ref mut jitter_rng) = self.source {
match jitter_rng.fill(dest) {
Ok(()) => return Ok(()),
Err(err) => {
warn!("EntropyRng: JitterRng failed: {}", err);
reported_error = Some(err);
},
}
} else if Jitter::is_supported() {
match Jitter::new_and_fill(dest) {
Ok(jitter_rng) => {
debug!("EntropyRng: using JitterRng");
self.source = Source::Jitter(jitter_rng);
return Ok(());
},
Err(err) => { reported_error = reported_error.or(Some(err)) },
}
}
if let Some(err) = reported_error {
Err(Error::with_cause(ErrorKind::Unavailable,
"All entropy sources failed",
err))
} else {
Err(Error::new(ErrorKind::Unavailable,
"No entropy sources available"))
}
}
}
impl CryptoRng for EntropyRng {}
trait EntropySource {
fn new_and_fill(dest: &mut [u8]) -> Result<Self, Error>
where Self: Sized;
fn fill(&mut self, dest: &mut [u8]) -> Result<(), Error>;
fn is_supported() -> bool { true }
}
#[allow(unused)]
#[derive(Clone, Debug)]
struct NoSource;
#[allow(unused)]
impl EntropySource for NoSource {
fn new_and_fill(dest: &mut [u8]) -> Result<Self, Error> {
Err(Error::new(ErrorKind::Unavailable, "Source not supported"))
}
fn fill(&mut self, dest: &mut [u8]) -> Result<(), Error> {
unreachable!()
}
fn is_supported() -> bool { false }
}
#[cfg(feature="rand_os")]
#[derive(Clone, Debug)]
pub struct Os(rngs::OsRng);
#[cfg(feature="rand_os")]
impl EntropySource for Os {
fn new_and_fill(dest: &mut [u8]) -> Result<Self, Error> {
let mut rng = rngs::OsRng::new()?;
rng.try_fill_bytes(dest)?;
Ok(Os(rng))
}
fn fill(&mut self, dest: &mut [u8]) -> Result<(), Error> {
self.0.try_fill_bytes(dest)
}
}
#[cfg(not(feature="std"))]
type Os = NoSource;
type Custom = NoSource;
#[cfg(not(target_arch = "wasm32"))]
#[derive(Clone, Debug)]
pub struct Jitter(rngs::JitterRng);
#[cfg(not(target_arch = "wasm32"))]
impl EntropySource for Jitter {
fn new_and_fill(dest: &mut [u8]) -> Result<Self, Error> {
let mut rng = rngs::JitterRng::new()?;
rng.try_fill_bytes(dest)?;
Ok(Jitter(rng))
}
fn fill(&mut self, dest: &mut [u8]) -> Result<(), Error> {
self.0.try_fill_bytes(dest)
}
}
#[cfg(target_arch = "wasm32")]
type Jitter = NoSource;
#[cfg(test)]
mod test {
use super::*;
#[test]
fn test_entropy() {
let mut rng = EntropyRng::new();
let n = (rng.next_u32() ^ rng.next_u32()).count_ones();
assert!(n >= 2);
}
}