Implement on WASM via stdweb and bindgen; add tests

Author: dhardy

.gitignore

@@ -1,3 +1,6 @@
 /target
 **/*.rs.bk
 Cargo.lock
+*.ts
+*.js
+*.wasm

Cargo.toml

@@ -9,6 +9,11 @@ description = "A small cross-platform library to securely get random data (entro
 travis-ci = { repository = "rust-random/getrandom" }
 appveyor = { repository = "rust-random/getrandom" }
 
+[workspace]
+members = [
+    "tests/wasm_bindgen",
+]
+
 [target.'cfg(unix)'.dependencies]
 libc = "0.2"
 

src/lib.rs

@@ -97,9 +97,20 @@
 
 #![no_std]
 
+#![cfg_attr(feature = "stdweb", recursion_limit="128")]
+
 #[cfg(not(target_env = "sgx"))]
 #[macro_use] extern crate std;
 
+// We have to do it here because we load macros
+#[cfg(all(target_arch = "wasm32", not(target_os = "emscripten"),
+          feature = "wasm-bindgen"))]
+extern crate wasm_bindgen;
+#[cfg(all(target_arch = "wasm32", not(target_os = "emscripten"),
+          not(feature = "wasm-bindgen"),
+          feature = "stdweb"))]
+#[macro_use] extern crate stdweb;
+
 #[cfg(any(
     target_os = "android",
     target_os = "netbsd",
@@ -108,8 +119,8 @@
     target_os = "redox",
     target_os = "dragonfly",
     target_os = "haiku",
-    target_os = "emscripten",
     target_os = "linux",
+    target_arch = "wasm32",
 ))]
 mod utils;
 mod error;
@@ -213,3 +224,58 @@ mod_use!(
 pub fn getrandom(dest: &mut [u8]) -> Result<(), Error> {
     getrandom_inner(dest)
 }
+
+// Due to rustwasm/wasm-bindgen#201 this can't be defined in the inner os
+// modules, so hack around it for now and place it at the root.
+#[cfg(all(feature = "wasm-bindgen", target_arch = "wasm32"))]
+#[doc(hidden)]
+#[allow(missing_debug_implementations)]
+pub mod __wbg_shims {
+
+    // `extern { type Foo; }` isn't supported on 1.22 syntactically, so use a
+    // macro to work around that.
+    macro_rules! rust_122_compat {
+        ($($t:tt)*) => ($($t)*)
+    }
+
+    rust_122_compat! {
+        extern crate wasm_bindgen;
+
+        pub use wasm_bindgen::prelude::*;
+
+        #[wasm_bindgen]
+        extern "C" {
+            pub type Function;
+            #[wasm_bindgen(constructor)]
+            pub fn new(s: &str) -> Function;
+            #[wasm_bindgen(method)]
+            pub fn call(this: &Function, self_: &JsValue) -> JsValue;
+
+            pub type This;
+            #[wasm_bindgen(method, getter, structural, js_name = self)]
+            pub fn self_(me: &This) -> JsValue;
+            #[wasm_bindgen(method, getter, structural)]
+            pub fn crypto(me: &This) -> JsValue;
+
+            #[derive(Clone, Debug)]
+            pub 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)]
+            pub fn get_random_values_fn(me: &BrowserCrypto) -> JsValue;
+            #[wasm_bindgen(method, js_name = getRandomValues, structural)]
+            pub fn get_random_values(me: &BrowserCrypto, buf: &mut [u8]);
+
+            #[wasm_bindgen(js_name = require)]
+            pub fn node_require(s: &str) -> NodeCrypto;
+
+            #[derive(Clone, Debug)]
+            pub type NodeCrypto;
+
+            #[wasm_bindgen(method, js_name = randomFillSync, structural)]
+            pub fn random_fill_sync(me: &NodeCrypto, buf: &mut [u8]);
+        }
+    }
+}

src/wasm32_bindgen.rs

@@ -7,3 +7,86 @@
 // except according to those terms.
 
 //! Implementation for WASM via wasm-bindgen
+
+use std::cell::RefCell;
+use std::mem;
+
+use wasm_bindgen::prelude::*;
+
+use super::__wbg_shims::*;
+use super::{Error, UNAVAILABLE_ERROR};
+use super::utils::use_init;
+
+
+#[derive(Clone, Debug)]
+pub enum RngSource {
+    Node(NodeCrypto),
+    Browser(BrowserCrypto),
+}
+
+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| {
+        use_init(f, getrandom_init, |source| {
+            match *source {
+                RngSource::Node(ref n) => n.random_fill_sync(dest),
+                RngSource::Browser(ref 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() {
+        let msg = "self.crypto is undefined";
+        return Err(UNAVAILABLE_ERROR)   // TODO: report msg
+    }
+
+    // Test if `crypto.getRandomValues` is undefined as well
+    let crypto: BrowserCrypto = crypto.into();
+    if crypto.get_random_values_fn().is_undefined() {
+        let msg = "crypto.getRandomValues is undefined";
+        return Err(UNAVAILABLE_ERROR)   // TODO: report msg
+    }
+
+    // Ok! `self.crypto.getRandomValues` is a defined value, so let's
+    // assume we can do browser crypto.
+    Ok(RngSource::Browser(crypto))
+}

src/wasm32_stdweb.rs

@@ -7,3 +7,101 @@
 // except according to those terms.
 
 //! Implementation for WASM via stdweb
+
+use std::cell::RefCell;
+use std::mem;
+
+use stdweb::unstable::TryInto;
+use stdweb::web::error::Error as WebError;
+
+use super::{Error, UNAVAILABLE_ERROR, UNKNOWN_ERROR};
+use super::utils::use_init;
+
+#[derive(Clone, Debug)]
+enum RngSource {
+    Browser,
+    Node
+}
+
+thread_local!(
+    static RNG_SOURCE: RefCell<Option<RngSource>> = RefCell::new(None);
+);
+
+pub fn getrandom_inner(mut dest: &mut [u8]) -> Result<(), Error> {
+    assert_eq!(mem::size_of::<usize>(), 4);
+
+    RNG_SOURCE.with(|f| {
+        use_init(f, getrandom_init, |source| getrandom_fill(source, dest))
+    })
+
+}
+
+fn getrandom_init() -> Result<RngSource, Error> {
+    let result = js! {
+        try {
+            if (
+                typeof self === "object" &&
+                typeof self.crypto === "object" &&
+                typeof self.crypto.getRandomValues === "function"
+            ) {
+                return { success: true, ty: 1 };
+            }
+
+            if (typeof require("crypto").randomBytes === "function") {
+                return { success: true, ty: 2 };
+            }
+
+            return { success: false, error: new Error("not supported") };
+        } catch(err) {
+            return { success: false, error: err };
+        }
+    };
+
+    if js!{ return @{ result.as_ref() }.success } == true {
+        let ty = js!{ return @{ result }.ty };
+
+        if ty == 1 { Ok(RngSource::Browser) }
+        else if ty == 2 { Ok(RngSource::Node) }
+        else { unreachable!() }
+    } else {
+        let err: WebError = js!{ return @{ result }.error }.try_into().unwrap();
+        Err(UNAVAILABLE_ERROR)  // TODO: forward err
+    }
+}
+
+fn getrandom_fill(source: &mut RngSource, mut dest: &mut [u8]) -> Result<(), Error> {
+    for chunk in dest.chunks_mut(65536) {
+        let len = chunk.len() as u32;
+        let ptr = chunk.as_mut_ptr() as i32;
+
+        let result = match source {
+            RngSource::Browser => js! {
+                try {
+                    let array = new Uint8Array(@{ len });
+                    self.crypto.getRandomValues(array);
+                    HEAPU8.set(array, @{ ptr });
+
+                    return { success: true };
+                } catch(err) {
+                    return { success: false, error: err };
+                }
+            },
+            RngSource::Node => js! {
+                try {
+                    let bytes = require("crypto").randomBytes(@{ len });
+                    HEAPU8.set(new Uint8Array(bytes), @{ ptr });
+
+                    return { success: true };
+                } catch(err) {
+                    return { success: false, error: err };
+                }
+            }
+        };
+
+        if js!{ return @{ result.as_ref() }.success } != true {
+            let err: WebError = js!{ return @{ result }.error }.try_into().unwrap();
+            return Err(UNKNOWN_ERROR)  // TODO: forward err
+        }
+    }
+    Ok(())
+}

tests/wasm_bindgen/Cargo.toml

@@ -0,0 +1,15 @@
+[package]
+name = "getrandom_wasm_bindgen_test"
+description = "Minimal test crate for getrandom using wasm-bindgen"
+version = "0.1.0"
+authors = ["The Rand Project Developers"]
+publish = false
+license = "MIT/Apache-2.0"
+
+[lib]
+crate-type = ["cdylib"]
+
+[dependencies]
+getrandom = { path = "../..", features = ["wasm-bindgen"] }
+wasm-bindgen = "0.2"
+wasm-bindgen-test = "0.2"

tests/wasm_bindgen/js/index.js

@@ -0,0 +1,5 @@
+'use strict';
+
+const getrandom_wasm_bindgen_test = require('./getrandom_wasm_bindgen_test');
+
+console.log(getrandom_wasm_bindgen_test.test_gen());

tests/wasm_bindgen/src/lib.rs

@@ -0,0 +1,55 @@
+// 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.
+
+// Crate to test WASM with the `wasm-bindgen` lib.
+
+#![doc(html_logo_url = "https://www.rust-lang.org/logos/rust-logo-128x128-blk.png")]
+
+extern crate getrandom;
+extern crate wasm_bindgen;
+extern crate wasm_bindgen_test;
+
+use std::slice;
+use wasm_bindgen_test::*;
+use wasm_bindgen::prelude::*;
+
+use getrandom::getrandom;
+
+#[wasm_bindgen]
+pub fn test_gen() -> i32 {
+    let mut int: i32 = 0;
+    unsafe {
+        let ptr = &mut int as *mut i32 as *mut u8;
+        let slice = slice::from_raw_parts_mut(ptr, 4);
+        getrandom(slice).unwrap();
+    }
+    int
+}
+
+#[wasm_bindgen_test]
+fn test_call() {
+    let mut buf = [0u8; 0];
+    getrandom(&mut buf).unwrap();
+}
+
+#[wasm_bindgen_test]
+fn test_diff() {
+    let mut v1 = [0u8; 1000];
+    getrandom(&mut v1).unwrap();
+
+    let mut v2 = [0u8; 1000];
+    getrandom(&mut v2).unwrap();
+
+    let mut n_diff_bits = 0;
+    for i in 0..v1.len() {
+        n_diff_bits += (v1[i] ^ v2[i]).count_ones();
+    }
+
+    // Check at least 1 bit per byte differs. p(failure) < 1e-1000 with random input.
+    assert!(n_diff_bits >= v1.len() as u32);
+}