Add a 'secure' constructor to Random in dart:math returning a cryptographically

runtime/lib/math.cc

Index: runtime/lib/math.cc
diff --git a/runtime/lib/math.cc b/runtime/lib/math.cc
index f4b4626b436091286088a5f2693ee957a3e8ebc8..c1a48ee70602f9001189eb04ed4ed53c5943541b 100644
--- a/runtime/lib/math.cc
+++ b/runtime/lib/math.cc
@@ -93,9 +93,10 @@ static RawTypedData* GetRandomStateArray(const Instance& receiver) {
 
 
 // Implements:
-//   var state = ((_A * (_state[kSTATE_LO])) + _state[kSTATE_HI]) & _MASK_64;
-//   _state[kSTATE_LO] = state & _MASK_32;
-//   _state[kSTATE_HI] = state >> 32;
+//   var state =
+//       ((_A * (_state[_kSTATE_LO])) + _state[_kSTATE_HI]) & (1 << 64) - 1);
+//   _state[_kSTATE_LO] = state & (1 << 32) - 1);
+//   _state[_kSTATE_HI] = state >> 32;
 DEFINE_NATIVE_ENTRY(Random_nextState, 1) {
   GET_NON_NULL_NATIVE_ARGUMENT(Instance, receiver, arguments->NativeArgAt(0));
   const TypedData& array = TypedData::Handle(GetRandomStateArray(receiver));
@@ -145,8 +146,8 @@ uint64_t mix64(uint64_t n) {
 //     hash = 0x5A17;
 //   }
 //   var result = new Uint32List(2);
-//   result[kSTATE_LO] = seed & _MASK_32;
-//   result[kSTATE_HI] = seed >> 32;
+//   result[_kSTATE_LO] = seed & ((1 << 32) - 1);
+//   result[_kSTATE_HI] = seed >> 32;
 //   return result;
 DEFINE_NATIVE_ENTRY(Random_setupSeed, 1) {
   GET_NON_NULL_NATIVE_ARGUMENT(Integer, seed_int, arguments->NativeArgAt(0));
@@ -198,4 +199,25 @@ DEFINE_NATIVE_ENTRY(Random_initialSeed, 0) {
   return CreateRandomState(zone, seed);
 }
 
+
+DEFINE_NATIVE_ENTRY(SecureRandom_getBytes, 1) {
+  GET_NON_NULL_NATIVE_ARGUMENT(Smi, count, arguments->NativeArgAt(0));
+  const intptr_t n = count.Value();
+  ASSERT((n > 0) && (n <= 8));
+  uint8_t buffer[8];
+  Dart_EntropySource entropy_source = isolate->entropy_source_callback();
+  if ((entropy_source == NULL) || !entropy_source(buffer, n)) {
+    const String& error = String::Handle(String::New(
+        "Entropy source is not setup"));

[Lasse Reichstein Nielsen, 2015/10/14 11:08:45]

setup -> set up.

This message is directed at the embedder, but will be seen by the user.
The user can't set up an entropy source, and won't necessarily know what it is.

Maybe: "No source of cryptographically secure random numbers available"

[regis, 2015/10/14 20:22:35]

Done.

+    const Array& args = Array::Handle(Array::New(1));
+    args.SetAt(0, error);
+    Exceptions::ThrowByType(Exceptions::kUnsupported, args);
+  }
+  uint64_t result = 0;
+  for (intptr_t i = 0; i < n; i++) {
+    result = (result << 8) | buffer[i];
+  }
+  return Integer::New(result);
+}
+
 }  // namespace dart