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src: don't overwrite non-writable vm globals #11109

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src: don't overwrite non-writable vm globals #11109

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27 changes: 18 additions & 9 deletions src/node_contextify.cc
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Original file line number Diff line number Diff line change
Expand Up @@ -383,19 +383,28 @@ class ContextifyContext {
if (ctx->context_.IsEmpty())
return;

auto attributes = PropertyAttribute::None;
bool is_declared =
ctx->global_proxy()->HasRealNamedProperty(ctx->context(),
property).FromJust();
ctx->global_proxy()->GetRealNamedPropertyAttributes(ctx->context(),
property)
.To(&attributes);
bool read_only =
static_cast<int>(attributes) &
static_cast<int>(PropertyAttribute::ReadOnly);

if (is_declared && read_only)
return;

// true for x = 5
// false for this.x = 5
// false for Object.defineProperty(this, 'foo', ...)
// false for vmResult.x = 5 where vmResult = vm.runInContext();
bool is_contextual_store = ctx->global_proxy() != args.This();

bool set_property_will_throw =
args.ShouldThrowOnError() &&
!is_declared &&
is_contextual_store;
if (!is_declared && args.ShouldThrowOnError() && is_contextual_store)
return;

if (!set_property_will_throw) {
ctx->sandbox()->Set(property, value);
}
ctx->sandbox()->Set(property, value);
}


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13 changes: 13 additions & 0 deletions test/parallel/test-vm-context.js
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Expand Up @@ -75,3 +75,16 @@ assert.throws(function() {
// https://github.com/nodejs/node/issues/6158
ctx = new Proxy({}, {});
assert.strictEqual(typeof vm.runInNewContext('String', ctx), 'function');

// https://github.com/nodejs/node/issues/10223
ctx = vm.createContext();
vm.runInContext('Object.defineProperty(this, "x", { value: 42 })', ctx);
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Nit: These tests can be logically grouped. Can you group them in blocks?

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Which groups did you have in mind?

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Maybe something like this?

{
  // https://github.com/nodejs/node/issues/10223
  const ctx = vm.createContext();

  {
    vm.runInContext('Object.defineProperty(this, "x", { value: 42 })', ctx);
    assert.strictEqual(ctx.x, 42);
    assert.strictEqual(vm.runInContext('x', ctx), 42);
  }

  {
    vm.runInContext('x = 0', ctx);                      // Does not throw but x...
    assert.strictEqual(vm.runInContext('x', ctx), 42);  // ...should be unaltered.
  }

  {
    assert.throws(() => vm.runInContext('"use strict"; x = 0', ctx),
                  /Cannot assign to read only property 'x'/);
    assert.strictEqual(vm.runInContext('x', ctx), 42);
  }

}

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Blocks in JS Code look weird to me. I added some extra blank lines. OK like this?

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Cool :-) This looks clean to my eyes now.

assert.strictEqual(ctx.x, 42);
assert.strictEqual(vm.runInContext('x', ctx), 42);

vm.runInContext('x = 0', ctx); // Does not throw but x...
assert.strictEqual(vm.runInContext('x', ctx), 42); // ...should be unaltered.

assert.throws(() => vm.runInContext('"use strict"; x = 0', ctx),
/Cannot assign to read only property 'x'/);
assert.strictEqual(vm.runInContext('x', ctx), 42);