vendor/getrandom-0.1.14/src/wasm32_bindgen.rs

   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
   9 //! Implementation for WASM via wasm-bindgen
  10 extern crate std;
  11
  12 use core::cell::RefCell;
  13 use core::mem;
  14 use std::thread_local;
  15
  16 use wasm_bindgen::prelude::*;
  17
  18 use crate::error::{BINDGEN_CRYPTO_UNDEF, BINDGEN_GRV_UNDEF};
  19 use crate::Error;
  20
  21 #[derive(Clone, Debug)]
  22 enum RngSource {
  23     Node(NodeCrypto),
  24     Browser(BrowserCrypto),
  25 }
  26
  27 // JsValues are always per-thread, so we initialize RngSource for each thread.
  28 //   See: https://github.com/rustwasm/wasm-bindgen/pull/955
  29 thread_local!(
  30     static RNG_SOURCE: RefCell<Option<RngSource>> = RefCell::new(None);
  31 );
  32
  33 pub fn getrandom_inner(dest: &mut [u8]) -> Result<(), Error> {
  34     assert_eq!(mem::size_of::<usize>(), 4);
  35
  36     RNG_SOURCE.with(|f| {
  37         let mut source = f.borrow_mut();
  38         if source.is_none() {
  39             *source = Some(getrandom_init()?);
  40         }
  41
  42         match source.as_ref().unwrap() {
  43             RngSource::Node(n) => n.random_fill_sync(dest),
  44             RngSource::Browser(n) => {
  45                 // see https://developer.mozilla.org/en-US/docs/Web/API/Crypto/getRandomValues
  46                 //
  47                 // where it says:
  48                 //
  49                 // > A QuotaExceededError DOMException is thrown if the
  50                 // > requested length is greater than 65536 bytes.
  51                 for chunk in dest.chunks_mut(65536) {
  52                     n.get_random_values(chunk)
  53                 }
  54             }
  55         };
  56         Ok(())
  57     })
  58 }
  59
  60 fn getrandom_init() -> Result<RngSource, Error> {
  61     if let Ok(self_) = Global::get_self() {
  62         // If `self` is defined then we're in a browser somehow (main window
  63         // or web worker). Here we want to try to use
  64         // `crypto.getRandomValues`, but if `crypto` isn't defined we assume
  65         // we're in an older web browser and the OS RNG isn't available.
  66
  67         let crypto = self_.crypto();
  68         if crypto.is_undefined() {
  69             return Err(BINDGEN_CRYPTO_UNDEF);
  70         }
  71
  72         // Test if `crypto.getRandomValues` is undefined as well
  73         let crypto: BrowserCrypto = crypto.into();
  74         if crypto.get_random_values_fn().is_undefined() {
  75             return Err(BINDGEN_GRV_UNDEF);
  76         }
  77
  78         return Ok(RngSource::Browser(crypto));
  79     }
  80
  81     return Ok(RngSource::Node(node_require("crypto")));
  82 }
  83
  84 #[wasm_bindgen]
  85 extern "C" {
  86     type Global;
  87     #[wasm_bindgen(getter, catch, static_method_of = Global, js_class = self, js_name = self)]
  88     fn get_self() -> Result<Self_, JsValue>;
  89
  90     type Self_;
  91     #[wasm_bindgen(method, getter, structural)]
  92     fn crypto(me: &Self_) -> JsValue;
  93
  94     #[derive(Clone, Debug)]
  95     type BrowserCrypto;
  96
  97     // TODO: these `structural` annotations here ideally wouldn't be here to
  98     // avoid a JS shim, but for now with feature detection they're
  99     // unavoidable.
 100     #[wasm_bindgen(method, js_name = getRandomValues, structural, getter)]
 101     fn get_random_values_fn(me: &BrowserCrypto) -> JsValue;
 102     #[wasm_bindgen(method, js_name = getRandomValues, structural)]
 103     fn get_random_values(me: &BrowserCrypto, buf: &mut [u8]);
 104
 105     #[wasm_bindgen(js_name = require)]
 106     fn node_require(s: &str) -> NodeCrypto;
 107
 108     #[derive(Clone, Debug)]
 109     type NodeCrypto;
 110
 111     #[wasm_bindgen(method, js_name = randomFillSync, structural)]
 112     fn random_fill_sync(me: &NodeCrypto, buf: &mut [u8]);
 113 }