1 // Copyright 2018 Developers of the Rand project.
2 //
3 // Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
4 // https://www.apache.org/licenses/LICENSE-2.0> or the MIT license
5 // <LICENSE-MIT or https://opensource.org/licenses/MIT>, at your
6 // option. This file may not be copied, modified, or distributed
7 // except according to those terms.
8 use crate::Error;
9
10 extern crate std;
11 use std::thread_local;
12
13 use js_sys::Uint8Array;
14 use wasm_bindgen::{prelude::*, JsCast};
15
16 // Maximum is 65536 bytes see https://developer.mozilla.org/en-US/docs/Web/API/Crypto/getRandomValues
17 const BROWSER_CRYPTO_BUFFER_SIZE: usize = 256;
18
19 enum RngSource {
20 Node(NodeCrypto),
21 Browser(BrowserCrypto, Uint8Array),
22 }
23
24 // JsValues are always per-thread, so we initialize RngSource for each thread.
25 // See: https://github.com/rustwasm/wasm-bindgen/pull/955
26 thread_local!(
27 static RNG_SOURCE: Result<RngSource, Error> = getrandom_init();
28 );
29
getrandom_inner(dest: &mut [u8]) -> Result<(), Error>30 pub(crate) fn getrandom_inner(dest: &mut [u8]) -> Result<(), Error> {
31 RNG_SOURCE.with(|result| {
32 let source = result.as_ref().map_err(|&e| e)?;
33
34 match source {
35 RngSource::Node(n) => {
36 if n.random_fill_sync(dest).is_err() {
37 return Err(Error::NODE_RANDOM_FILL_SYNC);
38 }
39 }
40 RngSource::Browser(crypto, buf) => {
41 // getRandomValues does not work with all types of WASM memory,
42 // so we initially write to browser memory to avoid exceptions.
43 for chunk in dest.chunks_mut(BROWSER_CRYPTO_BUFFER_SIZE) {
44 // The chunk can be smaller than buf's length, so we call to
45 // JS to create a smaller view of buf without allocation.
46 let sub_buf = buf.subarray(0, chunk.len() as u32);
47
48 if crypto.get_random_values(&sub_buf).is_err() {
49 return Err(Error::WEB_GET_RANDOM_VALUES);
50 }
51 sub_buf.copy_to(chunk);
52 }
53 }
54 };
55 Ok(())
56 })
57 }
58
getrandom_init() -> Result<RngSource, Error>59 fn getrandom_init() -> Result<RngSource, Error> {
60 let global: Global = js_sys::global().unchecked_into();
61 if is_node(&global) {
62 let crypto = require("crypto").map_err(|_| Error::NODE_CRYPTO)?;
63 return Ok(RngSource::Node(crypto));
64 }
65
66 // Assume we are in some Web environment (browser or web worker). We get
67 // `self.crypto` (called `msCrypto` on IE), so we can call
68 // `crypto.getRandomValues`. If `crypto` isn't defined, we assume that
69 // we are in an older web browser and the OS RNG isn't available.
70 let crypto = match (global.crypto(), global.ms_crypto()) {
71 (c, _) if c.is_object() => c,
72 (_, c) if c.is_object() => c,
73 _ => return Err(Error::WEB_CRYPTO),
74 };
75
76 let buf = Uint8Array::new_with_length(BROWSER_CRYPTO_BUFFER_SIZE as u32);
77 Ok(RngSource::Browser(crypto, buf))
78 }
79
80 // Taken from https://www.npmjs.com/package/browser-or-node
is_node(global: &Global) -> bool81 fn is_node(global: &Global) -> bool {
82 let process = global.process();
83 if process.is_object() {
84 let versions = process.versions();
85 if versions.is_object() {
86 return versions.node().is_string();
87 }
88 }
89 false
90 }
91
92 #[wasm_bindgen]
93 extern "C" {
94 type Global; // Return type of js_sys::global()
95
96 // Web Crypto API (https://www.w3.org/TR/WebCryptoAPI/)
97 #[wasm_bindgen(method, getter, js_name = "msCrypto")]
ms_crypto(this: &Global) -> BrowserCrypto98 fn ms_crypto(this: &Global) -> BrowserCrypto;
99 #[wasm_bindgen(method, getter)]
crypto(this: &Global) -> BrowserCrypto100 fn crypto(this: &Global) -> BrowserCrypto;
101 type BrowserCrypto;
102 #[wasm_bindgen(method, js_name = getRandomValues, catch)]
get_random_values(this: &BrowserCrypto, buf: &Uint8Array) -> Result<(), JsValue>103 fn get_random_values(this: &BrowserCrypto, buf: &Uint8Array) -> Result<(), JsValue>;
104
105 // Node JS crypto module (https://nodejs.org/api/crypto.html)
106 #[wasm_bindgen(catch, js_name = "module.require")]
require(s: &str) -> Result<NodeCrypto, JsValue>107 fn require(s: &str) -> Result<NodeCrypto, JsValue>;
108 type NodeCrypto;
109 #[wasm_bindgen(method, js_name = randomFillSync, catch)]
random_fill_sync(this: &NodeCrypto, buf: &mut [u8]) -> Result<(), JsValue>110 fn random_fill_sync(this: &NodeCrypto, buf: &mut [u8]) -> Result<(), JsValue>;
111
112 // Node JS process Object (https://nodejs.org/api/process.html)
113 #[wasm_bindgen(method, getter)]
process(this: &Global) -> Process114 fn process(this: &Global) -> Process;
115 type Process;
116 #[wasm_bindgen(method, getter)]
versions(this: &Process) -> Versions117 fn versions(this: &Process) -> Versions;
118 type Versions;
119 #[wasm_bindgen(method, getter)]
node(this: &Versions) -> JsValue120 fn node(this: &Versions) -> JsValue;
121 }
122