1 files changed, 161 insertions, 0 deletions
diff --git a/third_party/rust/getrandom/src/js.rs b/third_party/rust/getrandom/src/js.rs
new file mode 100644
index 0000000000..d031282261
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+++ b/third_party/rust/getrandom/src/js.rs
@@ -0,0 +1,161 @@
+// 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::{mem::MaybeUninit, thread_local};
+
+use js_sys::{global, Function, Uint8Array};
+use wasm_bindgen::{prelude::wasm_bindgen, JsCast, JsValue};
+
+// Size of our temporary Uint8Array buffer used with WebCrypto methods
+// Maximum is 65536 bytes see https://developer.mozilla.org/en-US/docs/Web/API/Crypto/getRandomValues
+const WEB_CRYPTO_BUFFER_SIZE: usize = 256;
+// Node.js's crypto.randomFillSync requires the size to be less than 2**31.
+const NODE_MAX_BUFFER_SIZE: usize = (1 << 31) - 1;
+
+enum RngSource {
+    Node(NodeCrypto),
+    Web(WebCrypto, 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 [MaybeUninit<u8>]) -> Result<(), Error> {
+    RNG_SOURCE.with(|result| {
+        let source = result.as_ref().map_err(|&e| e)?;
+
+        match source {
+            RngSource::Node(n) => {
+                for chunk in dest.chunks_mut(NODE_MAX_BUFFER_SIZE) {
+                    // SAFETY: chunk is never used directly, the memory is only
+                    // modified via the Uint8Array view, which is passed
+                    // directly to JavaScript. Also, crypto.randomFillSync does
+                    // not resize the buffer. We know the length is less than
+                    // u32::MAX because of the chunking above.
+                    // Note that this uses the fact that JavaScript doesn't
+                    // have a notion of "uninitialized memory", this is purely
+                    // a Rust/C/C++ concept.
+                    let res = n.random_fill_sync(unsafe {
+                        Uint8Array::view_mut_raw(chunk.as_mut_ptr() as *mut u8, chunk.len())
+                    });
+                    if res.is_err() {
+                        return Err(Error::NODE_RANDOM_FILL_SYNC);
+                    }
+                }
+            }
+            RngSource::Web(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(WEB_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);
+                    }
+
+                    // SAFETY: `sub_buf`'s length is the same length as `chunk`
+                    unsafe { sub_buf.raw_copy_to_ptr(chunk.as_mut_ptr() as *mut u8) };
+                }
+            }
+        };
+        Ok(())
+    })
+}
+
+fn getrandom_init() -> Result<RngSource, Error> {
+    let global: Global = global().unchecked_into();
+
+    // Get the Web Crypto interface if we are in a browser, Web Worker, Deno,
+    // or another environment that supports the Web Cryptography API. This
+    // also allows for user-provided polyfills in unsupported environments.
+    let crypto = match global.crypto() {
+        // Standard Web Crypto interface
+        c if c.is_object() => c,
+        // Node.js CommonJS Crypto module
+        _ if is_node(&global) => {
+            // If module.require isn't a valid function, we are in an ES module.
+            match Module::require_fn().and_then(JsCast::dyn_into::<Function>) {
+                Ok(require_fn) => match require_fn.call1(&global, &JsValue::from_str("crypto")) {
+                    Ok(n) => return Ok(RngSource::Node(n.unchecked_into())),
+                    Err(_) => return Err(Error::NODE_CRYPTO),
+                },
+                Err(_) => return Err(Error::NODE_ES_MODULE),
+            }
+        }
+        // IE 11 Workaround
+        _ => match global.ms_crypto() {
+            c if c.is_object() => c,
+            _ => return Err(Error::WEB_CRYPTO),
+        },
+    };
+
+    let buf = Uint8Array::new_with_length(WEB_CRYPTO_BUFFER_SIZE as u32);
+    Ok(RngSource::Web(crypto, buf))
+}
+
+// Taken from https://www.npmjs.com/package/browser-or-node
+fn is_node(global: &Global) -> bool {
+    let process = global.process();
+    if process.is_object() {
+        let versions = process.versions();
+        if versions.is_object() {
+            return versions.node().is_string();
+        }
+    }
+    false
+}
+
+#[wasm_bindgen]
+extern "C" {
+    // Return type of js_sys::global()
+    type Global;
+
+    // Web Crypto API: Crypto interface (https://www.w3.org/TR/WebCryptoAPI/)
+    type WebCrypto;
+    // Getters for the WebCrypto API
+    #[wasm_bindgen(method, getter)]
+    fn crypto(this: &Global) -> WebCrypto;
+    #[wasm_bindgen(method, getter, js_name = msCrypto)]
+    fn ms_crypto(this: &Global) -> WebCrypto;
+    // Crypto.getRandomValues()
+    #[wasm_bindgen(method, js_name = getRandomValues, catch)]
+    fn get_random_values(this: &WebCrypto, buf: &Uint8Array) -> Result<(), JsValue>;
+
+    // Node JS crypto module (https://nodejs.org/api/crypto.html)
+    type NodeCrypto;
+    // crypto.randomFillSync()
+    #[wasm_bindgen(method, js_name = randomFillSync, catch)]
+    fn random_fill_sync(this: &NodeCrypto, buf: Uint8Array) -> Result<(), JsValue>;
+
+    // Ideally, we would just use `fn require(s: &str)` here. However, doing
+    // this causes a Webpack warning. So we instead return the function itself
+    // and manually invoke it using call1. This also lets us to check that the
+    // function actually exists, allowing for better error messages. See:
+    //   https://github.com/rust-random/getrandom/issues/224
+    //   https://github.com/rust-random/getrandom/issues/256
+    type Module;
+    #[wasm_bindgen(getter, static_method_of = Module, js_class = module, js_name = require, catch)]
+    fn require_fn() -> Result<JsValue, JsValue>;
+
+    // Node JS process Object (https://nodejs.org/api/process.html)
+    #[wasm_bindgen(method, getter)]
+    fn process(this: &Global) -> Process;
+    type Process;
+    #[wasm_bindgen(method, getter)]
+    fn versions(this: &Process) -> Versions;
+    type Versions;
+    #[wasm_bindgen(method, getter)]
+    fn node(this: &Versions) -> JsValue;
+}