make randombytes use runtime.random.getRandomValues (if available)

Author: Face Kapow

js/core/libsodium.js

@@ -133,10 +133,16 @@ module.exports = {
       throw new Error('crypto_aead_chacha20poly1305_decrypt: error decrypting box.');
     }
     return hexToU8(decipher.deciphertext);
-  },
+  }
 };
 
 var justConvertHex = [
+  {
+    funcName: 'randombytes_buf',
+    errorInfo: 'error generating randomness.',
+    dataVerifier: isNumber,
+    argName: 'buffer length'
+  },
   {
     funcName: 'crypto_generichash',
     errorInfo: 'error calculating hash.'
@@ -153,10 +159,11 @@ var justConvertHex = [
 
 for (var i = 0; i < justConvertHex.length; i++) {
   (function(i) {
-    module.exports[justConvertHex[i].funcName] = function(data) {
-      var result = lib[justConvertHex[i].funcName](stringOrU8(data, justConvertHex[i].funcName, 'data', 0));
+    var f = justConvertHex[i];
+    module.exports[f.funcName] = function(data) {
+      var result = lib[f.funcName]((f.dataVerifier ? f.dataVerifier : stringOrU8)(data, f.funcName, (f.argName ? f.argName : 'data'), 0));
       if (!result) {
-        throw new Error(justConvertHex[i].funcName + ': ' + justConvertHex[i].errorInfo);
+        throw new Error(f.funcName + ': ' + (f.errorInfo ? f.errorInfo : 'unknown error.'));
       }
       return hexToU8(result);
     }

src/kernel/kernel-main.cc

@@ -141,18 +141,60 @@ void KernelMain::MakeV8Snapshot() {
 }
 
 const char* runtime_rng_name() {
-    return "runtimejs";
+  return "runtimejs";
 }
 
 uint32_t runtime_rng_random() {
+  // prevent abort()
+  if (GLOBAL_engines()) {
+    v8::Isolate* iv8 = GLOBAL_engines()->cpu_engine()->thread_manager()->current_thread()->IsolateV8();
+    v8::Local<v8::Context> context = iv8->GetCurrentContext();
+
+    v8::Local<v8::Object> global = context->Global();
+    v8::Local<v8::Object> runtimeObj = global->Get(context, v8::String::NewFromUtf8(iv8, "runtime", v8::NewStringType::kNormal).ToLocalChecked()).ToLocalChecked()->ToObject();
+    v8::Local<v8::Object> runtimeRandomObj = runtimeObj->Get(context, v8::String::NewFromUtf8(iv8, "random", v8::NewStringType::kNormal).ToLocalChecked()).ToLocalChecked()->ToObject();
+    v8::Local<v8::Function> runtimeRandomGetRandomValuesFunc = v8::Local<v8::Function>::Cast(runtimeRandomObj->Get(context, v8::String::NewFromUtf8(iv8, "getRandomValues", v8::NewStringType::kNormal).ToLocalChecked()).ToLocalChecked());
+
+    v8::Local<v8::Value> args[1] = { v8::Number::New(iv8, 1) };
+
+    // js equivalent: runtime.random.getRandomValues.apply(undefined, [1])
+    v8::Local<v8::Object> u8Array = runtimeRandomGetRandomValuesFunc->Call(context, v8::Undefined(iv8), 1, args).ToLocalChecked()->ToObject(context).ToLocalChecked();
+    return (uint8_t)(u8Array->Get(0)->ToNumber()->Value());
+  } else {
+    // mainly when libsodium is intialized, which is before V8 is available
+    printf("[randombytes] fallback used\n");
     return 42;
+  }
 }
 
 void runtime_rng_buf(void* const buf, const size_t size) {
-    uint8_t* b = reinterpret_cast<uint8_t*>(buf);
+  uint8_t* b = reinterpret_cast<uint8_t*>(buf);
+
+  // prevent abort()
+  if (GLOBAL_engines()) {
+    v8::Isolate* iv8 = GLOBAL_engines()->cpu_engine()->thread_manager()->current_thread()->IsolateV8();
+    v8::Local<v8::Context> context = iv8->GetCurrentContext();
+
+    v8::Local<v8::Object> global = context->Global();
+    v8::Local<v8::Object> runtimeObj = global->Get(context, v8::String::NewFromUtf8(iv8, "runtime", v8::NewStringType::kNormal).ToLocalChecked()).ToLocalChecked()->ToObject();
+    v8::Local<v8::Object> runtimeRandomObj = runtimeObj->Get(context, v8::String::NewFromUtf8(iv8, "random", v8::NewStringType::kNormal).ToLocalChecked()).ToLocalChecked()->ToObject();
+    v8::Local<v8::Function> runtimeRandomGetRandomValuesFunc = v8::Local<v8::Function>::Cast(runtimeRandomObj->Get(context, v8::String::NewFromUtf8(iv8, "getRandomValues", v8::NewStringType::kNormal).ToLocalChecked()).ToLocalChecked());
+
+    v8::Local<v8::Value> args[1] = { v8::Number::New(iv8, size) };
+
+    // js equivalent: runtime.random.getRandomValues.apply(undefined, [size])
+    v8::Local<v8::Object> u8Array = runtimeRandomGetRandomValuesFunc->Call(context, v8::Undefined(iv8), 1, args).ToLocalChecked()->ToObject(context).ToLocalChecked();
+
     for (size_t i = 0; i < size; ++i) {
-        b[i] = 42;
+      b[i] = (uint8_t)u8Array->Get(i)->ToNumber()->Value();
     }
+  } else {
+    // mainly when libsodium is intialized, which is before V8 is available
+    printf("[randombytes] fallback used\n");
+    for (size_t i = 0; i < size; ++i) {
+      b[i] = 42;
+    }
+  }
 }
 
 void KernelMain::InitSystemBSP(void* mbt) {

src/kernel/native-object.cc

@@ -1131,6 +1131,34 @@ NATIVE_FUNCTION(NativesObject, AllocDMA) {
   args.GetReturnValue().Set(ret);
 }
 
+NATIVE_FUNCTION(LibsodiumObject, RandombytesBuf) {
+  PROLOGUE;
+  USEARG(0);
+  VALIDATEARG(0, NUMBER, "randombytes_buf: argument 0 is not a number.");
+
+  v8::Local<v8::Number> bufNum = arg0->ToNumber(context).ToLocalChecked();
+  unsigned long long bufLen = bufNum->Value();
+
+  unsigned char buf[bufLen];
+  randombytes_buf(buf, bufLen);
+
+  char returnString[(sizeof(buf)/sizeof(unsigned char))*2 + 1];
+
+  for (int i = 0; i < (sizeof(buf)/sizeof(unsigned char)); i++) {
+    sprintf(&returnString[i*2], "%02X", buf[i]);
+  }
+
+  v8::MaybeLocal<v8::String> maybe_ret = v8::String::NewFromUtf8(iv8, returnString, v8::NewStringType::kNormal);
+
+  v8::Local<v8::String> ret;
+  if (!maybe_ret.ToLocal(&ret)) {
+    args.GetReturnValue().SetUndefined();
+    return;
+  }
+
+  args.GetReturnValue().Set(ret);
+}
+
 NATIVE_FUNCTION(LibsodiumObject, BlakeHash) {
   PROLOGUE;
   USEARG(0);

src/kernel/native-object.h

@@ -296,8 +296,10 @@ class LibsodiumObject : public JsObjectWrapper<LibsodiumObject, NativeTypeId::TY
   DECLARE_NATIVE(AuthVerify);
   DECLARE_NATIVE(AEADChaCha20Poly135Encrypt);
   DECLARE_NATIVE(AEADChaCha20Poly135Decrypt);
+  DECLARE_NATIVE(RandombytesBuf);
 
   void ObjectInit(ExportBuilder obj) {
+    obj.SetCallback("randombytes_buf", RandombytesBuf);
     obj.SetCallback("crypto_generichash", BlakeHash);
     obj.SetCallback("crypto_hash_sha256", Sha256Hash);
     obj.SetCallback("crypto_hash_sha512", Sha512Hash);