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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 wasm-bindgen
extern crate std;
use core::cell::RefCell;
use core::mem;
use std::thread_local;
use wasm_bindgen::prelude::*;
use crate::error::{BINDGEN_CRYPTO_UNDEF, BINDGEN_GRV_UNDEF};
use crate::Error;
#[derive(Clone, Debug)]
enum RngSource {
Node(NodeCrypto),
Browser(BrowserCrypto),
}
// 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: RefCell<Option<RngSource>> = RefCell::new(None);
);
pub fn getrandom_inner(dest: &mut [u8]) -> Result<(), Error> {
assert_eq!(mem::size_of::<usize>(), 4);
RNG_SOURCE.with(|f| {
let mut source = f.borrow_mut();
if source.is_none() {
*source = Some(getrandom_init()?);
}
match source.as_ref().unwrap() {
RngSource::Node(n) => n.random_fill_sync(dest),
RngSource::Browser(n) => {
// see https://developer.mozilla.org/en-US/docs/Web/API/Crypto/getRandomValues
//
// where it says:
//
// > A QuotaExceededError DOMException is thrown if the
// > requested length is greater than 65536 bytes.
for chunk in dest.chunks_mut(65536) {
n.get_random_values(chunk)
}
}
};
Ok(())
})
}
fn getrandom_init() -> Result<RngSource, Error> {
// First up we need to detect if we're running in node.js or a
// browser. To do this we get ahold of the `this` object (in a bit
// of a roundabout fashion).
//
// Once we have `this` we look at its `self` property, which is
// only defined on the web (either a main window or web worker).
let this = Function::new("return this").call(&JsValue::undefined());
assert!(this != JsValue::undefined());
let this = This::from(this);
let is_browser = this.self_() != JsValue::undefined();
if !is_browser {
return Ok(RngSource::Node(node_require("crypto")));
}
// If `self` is defined then we're in a browser somehow (main window
// or web worker). Here we want to try to use
// `crypto.getRandomValues`, but if `crypto` isn't defined we assume
// we're in an older web browser and the OS RNG isn't available.
let crypto = this.crypto();
if crypto.is_undefined() {
return Err(BINDGEN_CRYPTO_UNDEF);
}
// Test if `crypto.getRandomValues` is undefined as well
let crypto: BrowserCrypto = crypto.into();
if crypto.get_random_values_fn().is_undefined() {
return Err(BINDGEN_GRV_UNDEF);
}
// Ok! `self.crypto.getRandomValues` is a defined value, so let's
// assume we can do browser crypto.
Ok(RngSource::Browser(crypto))
}
#[wasm_bindgen]
extern "C" {
type Function;
#[wasm_bindgen(constructor)]
fn new(s: &str) -> Function;
#[wasm_bindgen(method)]
fn call(this: &Function, self_: &JsValue) -> JsValue;
type This;
#[wasm_bindgen(method, getter, structural, js_name = self)]
fn self_(me: &This) -> JsValue;
#[wasm_bindgen(method, getter, structural)]
fn crypto(me: &This) -> JsValue;
#[derive(Clone, Debug)]
type BrowserCrypto;
// TODO: these `structural` annotations here ideally wouldn't be here to
// avoid a JS shim, but for now with feature detection they're
// unavoidable.
#[wasm_bindgen(method, js_name = getRandomValues, structural, getter)]
fn get_random_values_fn(me: &BrowserCrypto) -> JsValue;
#[wasm_bindgen(method, js_name = getRandomValues, structural)]
fn get_random_values(me: &BrowserCrypto, buf: &mut [u8]);
#[wasm_bindgen(js_name = require)]
fn node_require(s: &str) -> NodeCrypto;
#[derive(Clone, Debug)]
type NodeCrypto;
#[wasm_bindgen(method, js_name = randomFillSync, structural)]
fn random_fill_sync(me: &NodeCrypto, buf: &mut [u8]);
}