Bug 185906 – Unexpected constructor / instanceof behavior when retrieving indexedDB data in an iframe

• Status: RESOLVED
• Resolution: FIXED
• Component: WebCore Misc.

[Maxime Réty]

There's an unexpected behavior in Safari 11.1 after retrieving data from indexedDB inside an iframe: the values cannot be properly checked against constructors with instanceof.

Pseudo code run in an iframe:

  // Store this record in indexedDB
  const record = { array: [1, 2, 3] };

  // Same record retrieved later from indexedDB:
  const record = event.target.result;
  record.array instanceof Array;               // expected true but false in Safari 11.1
  record.array instanceof window.parent.Array; // expected false but true in Safari 11.1

Tested on Safari Version 11.1 (13605.1.33.1.4) on macOS High Sierra 10.13.4.

The issue also occurs for Uint8Array, a.s.o. and probably all "constructed" types.

A lot of libraries and home-made code rely on instanceof to work as expected on values retrieved from indexedDB in an iframe.

Full test case: https://gist.github.com/maximerety/92431f6f4cc9ea8f684de8c124469995

Related issue: https://github.com/feross/buffer/issues/166

[John Vilk]

Created attachment 341118 [details]
Minimal test case

I have attached a minimal test case that demonstrates the issue.

Note: You cannot run this from a file:// URL, as those cannot create IndexedDB databases. I believe Safari also restricts IndexedDB databases in private browsing mode, so it must be a regular browser window.

Expected output (in console) (you see this output in Chrome and Firefox):

Testing in main context!
result.array instanceof Array: true
result.array instanceof window.top.Array: true
Array.isArray(result.array): true
result.arrayBuffer instanceof ArrayBuffer: true
result.arrayBuffer instanceof window.top.ArrayBuffer: true
Testing in iframe context!
result.array instanceof Array: true
result.array instanceof window.top.Array: false
Array.isArray(result.array): true
result.arrayBuffer instanceof ArrayBuffer: true
result.arrayBuffer instanceof window.top.ArrayBuffer: false
test complete.


Actual output:

[Log] Testing in main context! (idb_bug.html, line 36)
[Log] result.array instanceof Array: true (idb_bug.html, line 23)
[Log] result.array instanceof window.top.Array: true (idb_bug.html, line 24)
[Log] Array.isArray(result.array): true (idb_bug.html, line 25)
[Log] result.arrayBuffer instanceof ArrayBuffer: true (idb_bug.html, line 26)
[Log] result.arrayBuffer instanceof window.top.ArrayBuffer: true (idb_bug.html, line 27)
[Log] Testing in iframe context! (about:srcdoc, line 30)
[Log] result.array instanceof Array: false (about:srcdoc, line 19)
[Log] result.array instanceof window.top.Array: true (about:srcdoc, line 20)
[Log] Array.isArray(result.array): true (about:srcdoc, line 21)
[Log] result.arrayBuffer instanceof ArrayBuffer: false (about:srcdoc, line 22)
[Log] result.arrayBuffer instanceof window.top.ArrayBuffer: true (about:srcdoc, line 23)
[Log] test complete. (about:srcdoc, line 30)

[Radar WebKit Bug Importer]

<rdar://problem/40583100>

[Stefan Sechelmann]

Possibly a duplicate of https://bugs.webkit.org/show_bug.cgi?id=182097

[Sihui Liu]

Created attachment 355815 [details]
Patch

[Geoffrey Garen]

Comment on attachment 355815 [details]
Patch

r=me

[WebKit Commit Bot]

Comment on attachment 355815 [details]
Patch

Clearing flags on attachment: 355815

Committed r238676: <https://trac.webkit.org/changeset/238676>

[WebKit Commit Bot]

All reviewed patches have been landed.  Closing bug.

[Sihui Liu]

*** Bug 182097 has been marked as a duplicate of this bug. ***