Brandon ThomasandClaude Opus 5.5 18c1acdb31 Never crash: hostile form scripts can't overflow the stack ...

boa's parser and compiler recurse once per nesting level and have no limit of their own: about
100 nested parentheses in a field or document script overflowed a 2 MiB stack and aborted the
app, which `catch_unwind` can't stop. `printcraft_js::run` now:
- refuses a script longer than 256 KiB, or one that nests brackets more than 64 deep, chains
  more than 64 prefix operators, or has more than 4096 `?`. Strings and comments are skipped.
  The script fails with an error, as a syntax error would;
- runs the engine on its own thread with a 1 GiB stack, which is address space, committed only
  as it's used. That covers every unbracketed construct a 256 KiB script can nest. A panic
  inside the engine becomes a script error. On wasm the script still runs inline.

Regression tests: `deeply_nested_scripts_fail_instead_of_crashing`, which aborted the test
process before this change, and `ordinary_nesting_still_runs`.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

2026-10-04 13:06:24 -04:00

..

src

Never crash: hostile form scripts can't overflow the stack

2026-10-04 13:06:24 -04:00

Cargo.toml

M6: Acrobat JavaScript: sandboxed boa engine with the forms object model (printcraft-js); custom keystroke/validate/calculate/format scripts, button scripts, document JavaScripts, JavaScript console (⌘J), Preferences ▸ Enable JavaScript; js_run, js_document_scripts, js_set_document_script, form_set_script, js_enabled tools

2026-10-03 04:41:47 -04:00