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src: remove TOCTOU race condition when encoding SAB-backed Buffers #63517

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src: remove TOCTOU race condition when encoding SAB-backed Buffers #63517

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e209dbe
src: remove TOCTOU race condition when encoding SAB-backed `Buffer`s
aduh95 May 22, 2026
dc2be31
fixup! src: remove TOCTOU race condition when encoding SAB-backed `Bu…
aduh95 May 23, 2026
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16 changes: 14 additions & 2 deletions src/encoding_binding.cc
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Original file line number Diff line number Diff line change
Expand Up @@ -418,15 +418,20 @@ void BindingData::DecodeUTF8(const FunctionCallbackInfo<Value>& args) {
Environment* env = Environment::GetCurrent(args); // list, flags

CHECK_GE(args.Length(), 1);
auto isShared = args[0]->IsSharedArrayBuffer();

if (!(args[0]->IsArrayBuffer() || args[0]->IsSharedArrayBuffer() ||
args[0]->IsArrayBufferView())) {
if (!(args[0]->IsArrayBuffer() || isShared || args[0]->IsArrayBufferView())) {
return node::THROW_ERR_INVALID_ARG_TYPE(
env->isolate(),
"The \"list\" argument must be an instance of SharedArrayBuffer, "
"ArrayBuffer or ArrayBufferView.");
}

if (args[0]->IsArrayBufferView()) {
Local<v8::ArrayBufferView> view = args[0].As<v8::ArrayBufferView>();
isShared = view->Buffer()->IsSharedArrayBuffer();
}

ArrayBufferViewContents<char> buffer(args[0]);

bool ignore_bom = args[1]->IsTrue();
Expand All @@ -435,6 +440,13 @@ void BindingData::DecodeUTF8(const FunctionCallbackInfo<Value>& args) {
const char* data = buffer.data();
size_t length = buffer.length();

std::unique_ptr<char[]> data_copy;
if (isShared && length != 0) {
data_copy.reset(new char[length]);
memcpy(data_copy.get(), data, length);
data = data_copy.get();
}

if (!ignore_bom && length >= 3) {
if (memcmp(data, "\xEF\xBB\xBF", 3) == 0) {
data += 3;
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24 changes: 18 additions & 6 deletions src/node_buffer.cc
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Original file line number Diff line number Diff line change
Expand Up @@ -567,19 +567,31 @@ void StringSlice(const FunctionCallbackInfo<Value>& args) {
THROW_AND_RETURN_UNLESS_BUFFER(env, args[0]);
ArrayBufferViewContents<char> buffer(args[0]);

if (buffer.length() == 0)
return args.GetReturnValue().SetEmptyString();
auto buffer_length = buffer.length();
const char* data_ptr = buffer.data();

Local<ArrayBufferView> view = args[0].As<ArrayBufferView>();

if (buffer_length == 0) return args.GetReturnValue().SetEmptyString();

size_t start = 0;
size_t end = 0;
THROW_AND_RETURN_IF_OOB(ParseArrayIndex(env, args[1], 0, &start));
THROW_AND_RETURN_IF_OOB(ParseArrayIndex(env, args[2], buffer.length(), &end));
if (end < start) end = start;
THROW_AND_RETURN_IF_OOB(Just(end <= buffer.length()));
THROW_AND_RETURN_IF_OOB(ParseArrayIndex(env, args[2], buffer_length, &end));
if (end <= start) return args.GetReturnValue().SetEmptyString();
THROW_AND_RETURN_IF_OOB(Just(end <= buffer_length));
size_t length = end - start;

std::unique_ptr<char[]> data_copy;
if (view->Buffer()->IsSharedArrayBuffer()) {
data_copy.reset(new char[length]);
memcpy(data_copy.get(), data_ptr + start, length);
data_ptr = data_copy.get();
start = 0;
}

Local<Value> ret;
if (StringBytes::Encode(isolate, buffer.data() + start, length, encoding)
if (StringBytes::Encode(isolate, data_ptr + start, length, encoding)
.ToLocal(&ret)) {
args.GetReturnValue().Set(ret);
}
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