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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.
use crate::Error;
extern crate std;
use std::thread_local;
use js_sys::Uint8Array;
use wasm_bindgen::prelude::*;
// Maximum is 65536 bytes see https://developer.mozilla.org/en-US/docs/Web/API/Crypto/getRandomValues
const BROWSER_CRYPTO_BUFFER_SIZE: usize = 256;
enum RngSource {
Node(NodeCrypto),
Browser(BrowserCrypto, Uint8Array),
}
// JsValues are always per-thread, so we initialize RngSource for each thread.
// See: https://github.com/rustwasm/wasm-bindgen/pull/955
thread_local!(
static RNG_SOURCE: Result<RngSource, Error> = getrandom_init();
);
pub(crate) fn getrandom_inner(dest: &mut [u8]) -> Result<(), Error> {
RNG_SOURCE.with(|result| {
let source = result.as_ref().map_err(|&e| e)?;
match source {
RngSource::Node(n) => {
if n.random_fill_sync(dest).is_err() {
return Err(Error::NODE_RANDOM_FILL_SYNC);
}
}
RngSource::Browser(crypto, buf) => {
// getRandomValues does not work with all types of WASM memory,
// so we initially write to browser memory to avoid exceptions.
for chunk in dest.chunks_mut(BROWSER_CRYPTO_BUFFER_SIZE) {
// The chunk can be smaller than buf's length, so we call to
// JS to create a smaller view of buf without allocation.
let sub_buf = buf.subarray(0, chunk.len() as u32);
if crypto.get_random_values(&sub_buf).is_err() {
return Err(Error::WEB_GET_RANDOM_VALUES);
}
sub_buf.copy_to(chunk);
}
}
};
Ok(())
})
}
fn getrandom_init() -> Result<RngSource, Error> {
if let Ok(self_) = Global::get_self() {
// If `self` is defined then we're in a browser somehow (main window
// or web worker). We get `self.crypto` (called `msCrypto` on IE), so we
// can call `crypto.getRandomValues`. If `crypto` isn't defined, we
// assume we're in an older web browser and the OS RNG isn't available.
let crypto: BrowserCrypto = match (self_.crypto(), self_.ms_crypto()) {
(crypto, _) if !crypto.is_undefined() => crypto,
(_, crypto) if !crypto.is_undefined() => crypto,
_ => return Err(Error::WEB_CRYPTO),
};
let buf = Uint8Array::new_with_length(BROWSER_CRYPTO_BUFFER_SIZE as u32);
return Ok(RngSource::Browser(crypto, buf));
}
let crypto = MODULE.require("crypto").map_err(|_| Error::NODE_CRYPTO)?;
Ok(RngSource::Node(crypto))
}
#[wasm_bindgen]
extern "C" {
type Global;
#[wasm_bindgen(getter, catch, static_method_of = Global, js_class = self, js_name = self)]
fn get_self() -> Result<Self_, JsValue>;
type Self_;
#[wasm_bindgen(method, getter, js_name = "msCrypto")]
fn ms_crypto(me: &Self_) -> BrowserCrypto;
#[wasm_bindgen(method, getter)]
fn crypto(me: &Self_) -> BrowserCrypto;
type BrowserCrypto;
#[wasm_bindgen(method, js_name = getRandomValues, catch)]
fn get_random_values(me: &BrowserCrypto, buf: &Uint8Array) -> Result<(), JsValue>;
#[wasm_bindgen(js_name = module)]
static MODULE: NodeModule;
type NodeModule;
#[wasm_bindgen(method, catch)]
fn require(this: &NodeModule, s: &str) -> Result<NodeCrypto, JsValue>;
type NodeCrypto;
#[wasm_bindgen(method, js_name = randomFillSync, catch)]
fn random_fill_sync(crypto: &NodeCrypto, buf: &mut [u8]) -> Result<(), JsValue>;
}
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