130 lines
4.7 KiB
Rust
130 lines
4.7 KiB
Rust
// Copyright 2018 Developers of the Rand project.
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//
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// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
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// https://www.apache.org/licenses/LICENSE-2.0> or the MIT license
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// <LICENSE-MIT or https://opensource.org/licenses/MIT>, at your
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// option. This file may not be copied, modified, or distributed
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// except according to those terms.
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use crate::Error;
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extern crate std;
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use std::thread_local;
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use js_sys::{global, Uint8Array};
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use wasm_bindgen::{prelude::wasm_bindgen, JsCast, JsValue};
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// Maximum is 65536 bytes see https://developer.mozilla.org/en-US/docs/Web/API/Crypto/getRandomValues
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const BROWSER_CRYPTO_BUFFER_SIZE: usize = 256;
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enum RngSource {
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Node(NodeCrypto),
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Browser(BrowserCrypto, Uint8Array),
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}
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// JsValues are always per-thread, so we initialize RngSource for each thread.
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// See: https://github.com/rustwasm/wasm-bindgen/pull/955
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thread_local!(
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static RNG_SOURCE: Result<RngSource, Error> = getrandom_init();
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);
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pub(crate) fn getrandom_inner(dest: &mut [u8]) -> Result<(), Error> {
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RNG_SOURCE.with(|result| {
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let source = result.as_ref().map_err(|&e| e)?;
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match source {
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RngSource::Node(n) => {
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if n.random_fill_sync(dest).is_err() {
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return Err(Error::NODE_RANDOM_FILL_SYNC);
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}
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}
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RngSource::Browser(crypto, buf) => {
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// getRandomValues does not work with all types of WASM memory,
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// so we initially write to browser memory to avoid exceptions.
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for chunk in dest.chunks_mut(BROWSER_CRYPTO_BUFFER_SIZE) {
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// The chunk can be smaller than buf's length, so we call to
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// JS to create a smaller view of buf without allocation.
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let sub_buf = buf.subarray(0, chunk.len() as u32);
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if crypto.get_random_values(&sub_buf).is_err() {
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return Err(Error::WEB_GET_RANDOM_VALUES);
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}
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sub_buf.copy_to(chunk);
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}
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}
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};
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Ok(())
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})
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}
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fn getrandom_init() -> Result<RngSource, Error> {
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let global: Global = global().unchecked_into();
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if is_node(&global) {
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let crypto = NODE_MODULE
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.require("crypto")
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.map_err(|_| Error::NODE_CRYPTO)?;
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return Ok(RngSource::Node(crypto));
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}
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// Assume we are in some Web environment (browser or web worker). We get
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// `self.crypto` (called `msCrypto` on IE), so we can call
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// `crypto.getRandomValues`. If `crypto` isn't defined, we assume that
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// we are in an older web browser and the OS RNG isn't available.
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let crypto = match (global.crypto(), global.ms_crypto()) {
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(c, _) if c.is_object() => c,
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(_, c) if c.is_object() => c,
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_ => return Err(Error::WEB_CRYPTO),
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};
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let buf = Uint8Array::new_with_length(BROWSER_CRYPTO_BUFFER_SIZE as u32);
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Ok(RngSource::Browser(crypto, buf))
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}
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// Taken from https://www.npmjs.com/package/browser-or-node
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fn is_node(global: &Global) -> bool {
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let process = global.process();
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if process.is_object() {
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let versions = process.versions();
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if versions.is_object() {
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return versions.node().is_string();
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}
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}
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false
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}
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#[wasm_bindgen]
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extern "C" {
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type Global; // Return type of js_sys::global()
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// Web Crypto API (https://www.w3.org/TR/WebCryptoAPI/)
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#[wasm_bindgen(method, getter, js_name = "msCrypto")]
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fn ms_crypto(this: &Global) -> BrowserCrypto;
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#[wasm_bindgen(method, getter)]
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fn crypto(this: &Global) -> BrowserCrypto;
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type BrowserCrypto;
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#[wasm_bindgen(method, js_name = getRandomValues, catch)]
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fn get_random_values(this: &BrowserCrypto, buf: &Uint8Array) -> Result<(), JsValue>;
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// We use a "module" object here instead of just annotating require() with
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// js_name = "module.require", so that Webpack doesn't give a warning. See:
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// https://github.com/rust-random/getrandom/issues/224
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type NodeModule;
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#[wasm_bindgen(js_name = module)]
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static NODE_MODULE: NodeModule;
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// Node JS crypto module (https://nodejs.org/api/crypto.html)
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#[wasm_bindgen(method, catch)]
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fn require(this: &NodeModule, s: &str) -> Result<NodeCrypto, JsValue>;
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type NodeCrypto;
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#[wasm_bindgen(method, js_name = randomFillSync, catch)]
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fn random_fill_sync(this: &NodeCrypto, buf: &mut [u8]) -> Result<(), JsValue>;
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// Node JS process Object (https://nodejs.org/api/process.html)
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#[wasm_bindgen(method, getter)]
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fn process(this: &Global) -> Process;
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type Process;
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#[wasm_bindgen(method, getter)]
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fn versions(this: &Process) -> Versions;
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type Versions;
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#[wasm_bindgen(method, getter)]
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fn node(this: &Versions) -> JsValue;
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}
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