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// Copyright 2018 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.
//! Implementation for Linux / Android
extern crate libc;
use rand_core::{Error, ErrorKind};
use super::random_device;
use super::OsRngImpl;
use std::io;
use std::io::Read;
use std::fs::{File, OpenOptions};
use std::os::unix::fs::OpenOptionsExt;
use std::sync::atomic::{AtomicBool, ATOMIC_BOOL_INIT, Ordering};
use std::sync::{Once, ONCE_INIT};
#[derive(Clone, Debug)]
pub struct OsRng {
method: OsRngMethod,
initialized: bool,
}
#[derive(Clone, Debug)]
enum OsRngMethod {
GetRandom,
RandomDevice,
}
impl OsRngImpl for OsRng {
fn new() -> Result<OsRng, Error> {
if is_getrandom_available() {
return Ok(OsRng { method: OsRngMethod::GetRandom,
initialized: false });
}
random_device::open("/dev/urandom", &|p| File::open(p))?;
Ok(OsRng { method: OsRngMethod::RandomDevice, initialized: false })
}
fn fill_chunk(&mut self, dest: &mut [u8]) -> Result<(), Error> {
match self.method {
OsRngMethod::GetRandom => getrandom_try_fill(dest, false),
OsRngMethod::RandomDevice => random_device::read(dest),
}
}
fn test_initialized(&mut self, dest: &mut [u8], blocking: bool)
-> Result<usize, Error>
{
static OS_RNG_INITIALIZED: AtomicBool = ATOMIC_BOOL_INIT;
if !self.initialized {
self.initialized = OS_RNG_INITIALIZED.load(Ordering::Relaxed);
}
if self.initialized { return Ok(0); }
let result = match self.method {
OsRngMethod::GetRandom => {
getrandom_try_fill(dest, blocking)?;
Ok(dest.len())
}
OsRngMethod::RandomDevice => {
info!("OsRng: testing random device /dev/random");
let mut file = OpenOptions::new()
.read(true)
.custom_flags(if blocking { 0 } else { libc::O_NONBLOCK })
.open("/dev/random")
.map_err(random_device::map_err)?;
file.read(&mut dest[..1]).map_err(random_device::map_err)?;
Ok(1)
}
};
OS_RNG_INITIALIZED.store(true, Ordering::Relaxed);
self.initialized = true;
result
}
fn method_str(&self) -> &'static str {
match self.method {
OsRngMethod::GetRandom => "getrandom",
OsRngMethod::RandomDevice => "/dev/urandom",
}
}
}
#[cfg(target_arch = "x86_64")]
const NR_GETRANDOM: libc::c_long = 318;
#[cfg(target_arch = "x86")]
const NR_GETRANDOM: libc::c_long = 355;
#[cfg(target_arch = "arm")]
const NR_GETRANDOM: libc::c_long = 384;
#[cfg(target_arch = "aarch64")]
const NR_GETRANDOM: libc::c_long = 278;
#[cfg(target_arch = "s390x")]
const NR_GETRANDOM: libc::c_long = 349;
#[cfg(target_arch = "powerpc")]
const NR_GETRANDOM: libc::c_long = 359;
#[cfg(target_arch = "powerpc64")]
const NR_GETRANDOM: libc::c_long = 359;
#[cfg(target_arch = "mips")] // old ABI
const NR_GETRANDOM: libc::c_long = 4353;
#[cfg(target_arch = "mips64")]
const NR_GETRANDOM: libc::c_long = 5313;
#[cfg(target_arch = "sparc")]
const NR_GETRANDOM: libc::c_long = 347;
#[cfg(target_arch = "sparc64")]
const NR_GETRANDOM: libc::c_long = 347;
#[cfg(not(any(target_arch = "x86_64", target_arch = "x86",
target_arch = "arm", target_arch = "aarch64",
target_arch = "s390x", target_arch = "powerpc",
target_arch = "powerpc64", target_arch = "mips",
target_arch = "mips64", target_arch = "sparc",
target_arch = "sparc64")))]
const NR_GETRANDOM: libc::c_long = 0;
fn getrandom(buf: &mut [u8], blocking: bool) -> libc::c_long {
const GRND_NONBLOCK: libc::c_uint = 0x0001;
if NR_GETRANDOM == 0 { return -1 };
unsafe {
libc::syscall(NR_GETRANDOM, buf.as_mut_ptr(), buf.len(),
if blocking { 0 } else { GRND_NONBLOCK })
}
}
fn getrandom_try_fill(dest: &mut [u8], blocking: bool) -> Result<(), Error> {
let mut read = 0;
while read < dest.len() {
let result = getrandom(&mut dest[read..], blocking);
if result == -1 {
let err = io::Error::last_os_error();
let kind = err.kind();
if kind == io::ErrorKind::Interrupted {
continue;
} else if kind == io::ErrorKind::WouldBlock {
return Err(Error::with_cause(
ErrorKind::NotReady,
"getrandom not ready",
err,
));
} else {
return Err(Error::with_cause(
ErrorKind::Unavailable,
"unexpected getrandom error",
err,
));
}
} else {
read += result as usize;
}
}
Ok(())
}
fn is_getrandom_available() -> bool {
static CHECKER: Once = ONCE_INIT;
static AVAILABLE: AtomicBool = ATOMIC_BOOL_INIT;
if NR_GETRANDOM == 0 { return false };
CHECKER.call_once(|| {
debug!("OsRng: testing getrandom");
let mut buf: [u8; 0] = [];
let result = getrandom(&mut buf, false);
let available = if result == -1 {
let err = io::Error::last_os_error().raw_os_error();
err != Some(libc::ENOSYS)
} else {
true
};
AVAILABLE.store(available, Ordering::Relaxed);
info!("OsRng: using {}", if available { "getrandom" } else { "/dev/urandom" });
});
AVAILABLE.load(Ordering::Relaxed)
}
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