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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 WASM via stdweb
extern crate std;
use core::mem;
use stdweb::js;
use stdweb::unstable::TryInto;
use stdweb::web::error::Error as WebError;
use crate::error::{STDWEB_NO_RNG, STDWEB_RNG_FAILED};
use crate::Error;
use std::sync::Once;
#[derive(Clone, Copy, Debug)]
enum RngSource {
Browser,
Node,
}
pub fn getrandom_inner(dest: &mut [u8]) -> Result<(), Error> {
assert_eq!(mem::size_of::<usize>(), 4);
static ONCE: Once = Once::new();
static mut RNG_SOURCE: Result<RngSource, Error> = Ok(RngSource::Node);
// SAFETY: RNG_SOURCE is only written once, before being read.
ONCE.call_once(|| unsafe {
RNG_SOURCE = getrandom_init();
});
getrandom_fill(unsafe { RNG_SOURCE }?, dest)
}
fn getrandom_init() -> Result<RngSource, Error> {
let result = js! {
try {
if (
typeof self === "object" &&
typeof self.crypto === "object" &&
typeof self.crypto.getRandomValues === "function"
) {
return { success: true, ty: 1 };
}
if (typeof require("crypto").randomBytes === "function") {
return { success: true, ty: 2 };
}
return { success: false, error: new Error("not supported") };
} catch(err) {
return { success: false, error: err };
}
};
if js! { return @{ result.as_ref() }.success } == true {
let ty = js! { return @{ result }.ty };
if ty == 1 {
Ok(RngSource::Browser)
} else if ty == 2 {
Ok(RngSource::Node)
} else {
unreachable!()
}
} else {
let _err: WebError = js! { return @{ result }.error }.try_into().unwrap();
error!("getrandom unavailable: {}", _err);
Err(STDWEB_NO_RNG)
}
}
fn getrandom_fill(source: RngSource, dest: &mut [u8]) -> Result<(), Error> {
for chunk in dest.chunks_mut(65536) {
let len = chunk.len() as u32;
let ptr = chunk.as_mut_ptr() as i32;
let result = match source {
RngSource::Browser => js! {
try {
let array = new Uint8Array(@{ len });
self.crypto.getRandomValues(array);
HEAPU8.set(array, @{ ptr });
return { success: true };
} catch(err) {
return { success: false, error: err };
}
},
RngSource::Node => js! {
try {
let bytes = require("crypto").randomBytes(@{ len });
HEAPU8.set(new Uint8Array(bytes), @{ ptr });
return { success: true };
} catch(err) {
return { success: false, error: err };
}
},
};
if js! { return @{ result.as_ref() }.success } != true {
let _err: WebError = js! { return @{ result }.error }.try_into().unwrap();
error!("getrandom failed: {}", _err);
return Err(STDWEB_RNG_FAILED);
}
}
Ok(())
}
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