Extends the browser private-network eval guard to the Camofox backend.
On main, _browser_eval() returned early in Camofox mode before running the
shared private-URL literal pre-scan and before re-checking the page URL
after eval, leaving Camofox as a sibling backend that could execute
browser_console(expression=...) against private/internal targets.
- move the eval private-URL literal pre-scan before the Camofox early return
- add a Camofox current-page private-URL probe via the evaluate endpoint
- withhold Camofox eval results when the page is now private/internal
Follow-up to browser private-network hardening in #56173, #56526, #56664.
Salvage of #56764 by @rayjun (rayoo), cherry-picked to preserve authorship.
The snapshot/vision guards re-check the page URL before returning content,
but browser_console(expression=...) -> _browser_eval returns arbitrary JS
results directly, leaving two same-class bypasses open:
1. Direct fetch: fetch('http://127.0.0.1/secret').then(r=>r.text()) reads
a private endpoint and returns the body — the page URL stays public so
the post-eval recheck never sees it.
2. Navigate-then-read: location.href='http://127.0.0.1/' then a later eval
reads document.body.innerText.
Guard _browser_eval on the same condition as navigate/snapshot/vision
(not local backend, not local sidecar, not allow_private_urls):
- pre-scan the expression for private/always-blocked URL literals
- re-check window.location.href after the eval at both success-return
sites (supervisor fast-path + subprocess fallback)
Probe failures fail-open (matching the snapshot/vision guards).
