Adjust BufferSource for sandbox.

src/workerd/api/blob.c++

@@ -129,7 +129,7 @@ jsg::BufferSource wrap(jsg::Lock& js, kj::Array<byte> data) {
   // the underlying v8::BackingStore is supposed to free the buffer when
   // it is done with it. Unfortunately ASAN complains about a leak that
   // will require more investigation.
-  // return jsg::BufferSource(js, jsg::BackingStore::from(kj::mv(data)));
+  // return jsg::BufferSource(js, jsg::BackingStore::from(js, kj::mv(data)));
 }
 
 kj::ArrayPtr<const kj::byte> getPtr(jsg::BufferSource& source) {

src/workerd/api/crypto/crypto.h

@@ -208,7 +208,7 @@ class CryptoKey: public jsg::Object {
         KJ_CASE_ONEOF(array, BigInteger) {
           if (fixPublicExp) {
             auto expCopy = kj::heapArray<kj::byte>(array.asPtr());
-            jsg::BackingStore expBack = jsg::BackingStore::from(kj::mv(expCopy));
+            jsg::BackingStore expBack = jsg::BackingStore::from(js, kj::mv(expCopy));
             return {name, modulusLength, jsg::BufferSource(js, kj::mv(expBack)), hash};
           } else {
             return {name, modulusLength, kj::heapArray(array.asPtr()), hash};
@@ -218,7 +218,7 @@ class CryptoKey: public jsg::Object {
           // Should only happen if the flag is enabled and an algorithm field is cloned twice.
           KJ_ASSERT(fixPublicExp == true);
           auto expCopy = kj::heapArray<kj::byte>(source.asArrayPtr());
-          jsg::BackingStore expBack = jsg::BackingStore::from(kj::mv(expCopy));
+          jsg::BackingStore expBack = jsg::BackingStore::from(js, kj::mv(expCopy));
           return {name, modulusLength, jsg::BufferSource(js, kj::mv(expBack)), hash};
         }
       }

src/workerd/api/streams/standard-test.c++

@@ -24,16 +24,16 @@ void preamble(auto callback) {
 }
 
 v8::Local<v8::Value> toBytes(jsg::Lock& js, kj::String str) {
-  return jsg::BackingStore::from(str.asBytes().attach(kj::mv(str))).createHandle(js);
+  return jsg::BackingStore::from(js, str.asBytes().attach(kj::mv(str))).createHandle(js);
 }
 
 jsg::BufferSource toBufferSource(jsg::Lock& js, kj::String str) {
-  auto backing = jsg::BackingStore::from(str.asBytes().attach(kj::mv(str))).createHandle(js);
+  auto backing = jsg::BackingStore::from(js, str.asBytes().attach(kj::mv(str))).createHandle(js);
   return jsg::BufferSource(js, kj::mv(backing));
 }
 
 jsg::BufferSource toBufferSource(jsg::Lock& js, kj::Array<kj::byte> bytes) {
-  auto backing = jsg::BackingStore::from(kj::mv(bytes)).createHandle(js);
+  auto backing = jsg::BackingStore::from(js, kj::mv(bytes)).createHandle(js);
   return jsg::BufferSource(js, kj::mv(backing));
 }
 

src/workerd/jsg/buffersource-test.c++

@@ -48,7 +48,7 @@ struct BufferSourceContext: public jsg::Object, public jsg::ContextGlobal {
   }
 
   BufferSource makeBufferSource(jsg::Lock& js) {
-    return BufferSource(js, BackingStore::from(kj::arr<kj::byte>(1, 2, 3)));
+    return BufferSource(js, BackingStore::from(js, kj::arr<kj::byte>(1, 2, 3)));
   }
 
   BufferSource makeArrayBuffer(jsg::Lock& js) {

src/workerd/jsg/buffersource.h

@@ -69,19 +69,29 @@ using BufferSourceViewConstructor = v8::Local<v8::Value> (*)(Lock&, BackingStore
 // the byte length, offset, element size, and constructor type allowing the view to be
 // recreated.
 //
-// The BackingStore can be safely used outside of the isolate lock and can even be passed
-// into another isolate if necessary.
+// The BackingStore must be created in a particular isolate, but it can be
+// safely used outside of the isolate lock.  It cannot be passed to a different
+// isolate, unless they are in the same isolate group, which means they are in
+// the same sandbox.
 class BackingStore {
 public:
   template <BufferSourceType T = v8::Uint8Array>
-  static BackingStore from(kj::Array<kj::byte> data) {
+  static BackingStore from(Lock& js, kj::Array<kj::byte> data) {
     // Creates a new BackingStore that takes over ownership of the given kj::Array.
+    // The bytes may be moved if they are not inside the sandbox already.
     size_t size = data.size();
-    auto ptr = new kj::Array<byte>(kj::mv(data));
-    return BackingStore(
-        v8::ArrayBuffer::NewBackingStore(ptr->begin(), size,
-            [](void*, size_t, void* ptr) { delete reinterpret_cast<kj::Array<byte>*>(ptr); }, ptr),
-        size, 0, getBufferSourceElementSize<T>(), construct<T>, checkIsIntegerType<T>());
+    if (js.v8Isolate->GetGroup().SandboxContains(data.begin())) {
+      auto ptr = new kj::Array<byte>(kj::mv(data));
+      return BackingStore(
+          v8::ArrayBuffer::NewBackingStore(ptr->begin(), size,
+              [](void*, size_t, void* ptr) { delete reinterpret_cast<kj::Array<byte>*>(ptr); }, ptr),
+          size, 0, getBufferSourceElementSize<T>(), construct<T>, checkIsIntegerType<T>());
+    } else {
+      auto result = BackingStore(v8::ArrayBuffer::NewBackingStore(js.v8Isolate, size), size, 0,
+          getBufferSourceElementSize<T>(), construct<T>, checkIsIntegerType<T>());
+      memcpy(result.asArrayPtr().begin(), data.begin(), size);
+      return result;
+    }
   }
 
   // Creates a new BackingStore of the given size.
@@ -437,7 +447,7 @@ class BufferSourceWrapper {
 };
 
 inline BufferSource Lock::arrayBuffer(kj::Array<kj::byte> data) {
-  return BufferSource(*this, BackingStore::from<v8::ArrayBuffer>(kj::mv(data)));
+  return BufferSource(*this, BackingStore::from<v8::ArrayBuffer>(*this, kj::mv(data)));
 }
 
 }  // namespace workerd::jsg

src/workerd/jsg/jsg.h

@@ -2602,7 +2602,8 @@ class Lock {
   BufferSource bytes(kj::Array<kj::byte> data) KJ_WARN_UNUSED_RESULT;
 
   // Returns a jsg::BufferSource whose underlying JavaScript handle is an ArrayBuffer
-  // as opposed to the default Uint8Array.
+  // as opposed to the default Uint8Array.  May copy and move the bytes if they are
+  // not in the right sandbox.
   BufferSource arrayBuffer(kj::Array<kj::byte> data) KJ_WARN_UNUSED_RESULT;
 
   enum RegExpFlags {

src/workerd/jsg/jsvalue.c++

@@ -462,7 +462,7 @@ JsValue Lock::rangeError(kj::StringPtr message) {
 }
 
 BufferSource Lock::bytes(kj::Array<kj::byte> data) {
-  return BufferSource(*this, BackingStore::from(kj::mv(data)));
+  return BufferSource(*this, BackingStore::from(*this, kj::mv(data)));
 }
 
 JsSymbol Lock::symbol(kj::StringPtr str) {

src/workerd/jsg/value.h

@@ -931,9 +931,6 @@ class ArrayBufferWrapper {
       //   impossible to support unifying Array<T> and Vector<T> in the future (i.e. making all
       //   Array<T>s growable). So it may be best to stick with allocating an Array<byte> on the
       //   heap after all...
-
-      fprintf(stderr, "begin is %p\n", begin);
-
       auto ownerPtr = new kj::Array<byte>(kj::mv(value));
 
       std::unique_ptr<v8::BackingStore> backing =