fix(wasm): enhance data ownership management and ensure secure memory wipe on move

Author: sergei-boiko-trustwallet

wasm/src/WasmData.cpp

@@ -4,6 +4,7 @@
 //
 
 #include "WasmData.h"
+#include "Defer.h"
 
 #include <TrezorCrypto/memzero.h>
 
@@ -12,19 +13,23 @@ using namespace emscripten;
 namespace TW::Wasm {
 
 auto DataToVal(Data&& data) -> val {
-    auto view = val(typed_memory_view(data.size(), data.data()));
-    auto jsArray = val::global("Uint8Array").new_(data.size());
+    Data local = std::move(data);  // take ownership; caller's object is now empty
+    defer {
+        if (!local.empty()) { memzero(local.data(), local.size()); }
+    };
+    auto view = val(typed_memory_view(local.size(), local.data()));
+    auto jsArray = val::global("Uint8Array").new_(local.size());
     jsArray.call<void>("set", view);
-    if (!data.empty()) { memzero(data.data(), data.size()); }
     return jsArray;
 }
 
 auto TWDataToVal(TWData* _Nonnull data) -> val {
+    defer {
+        TWDataDelete(data);
+    };
     auto* v = reinterpret_cast<Data*>(data);
-    auto result = DataToVal(std::move(*v));
-    // v is now moved-from (empty); TWDataDelete skips memzero but frees the object.
-    TWDataDelete(data);
-    return result;
+    Data local = std::move(*v);  // *v is now genuinely empty; local owns the buffer
+    return DataToVal(std::move(local));
 }
 
 } // namespace TW::Wasm