1746186 - reportError() / self.onerror does not follow the specification

Status: RESOLVED FIXED

(Core :: DOM: Core & HTML, defect)

Description

[Anne (:annevk)]

As per https://html.spec.whatwg.org/#report-the-error we should not allow the message (and other arguments to onerror) be supplied by script, but

self.onerror=(a, b, c, d, e) => console.log(a,b,c,d,e)
self.reportError({lineNumber:1,columnNumber:2,fileName:3,message:'alert\x281\x29'})

shows we do.

Per investigation by Jan it's likely that https://searchfox.org/mozilla-central/rev/dc323d0d9a3b722ca8ff0d1b2b752e5bd00dab9b/js/src/jsexn.cpp#513-523 is the culprit here, hence filing it against the JS component as a start. I suggest that we essentially remove the duck-typing there, at least when it comes to non-chrome code, but ideally we just don't have it.

This came up on Twitter in https://twitter.com/portswiggerres/status/1470746433838059524. (Note that even if the message comes from us this might not completely solve the problem as shown in http://www.thespanner.co.uk/2012/05/01/xss-technique-without-parentheses/, but there's no reason for us to be different from Chrome for the above case. We might want to argue for less implementation-defined messages based on this.)

Comment 1

[Tom S [:evilpie]]

We should probably investigate if we can remove WithSideEffects completely, considering that devtools handle this stuff themself anyway.

However in this specific case we can just change the callers: https://searchfox.org/mozilla-central/rev/dc323d0d9a3b722ca8ff0d1b2b752e5bd00dab9b/dom/base/nsGlobalWindowInner.cpp#4179 and https://searchfox.org/mozilla-central/rev/dc323d0d9a3b722ca8ff0d1b2b752e5bd00dab9b/dom/workers/WorkerScope.cpp#312

Comment 2

[Tom S [:evilpie]]

Attachment: Bug 1746186 - Don't observablely sniff objects in reportError(). r?smaug

Comment 3

[Pulsebot]

Pushed by [e-mail]:
https://hg.mozilla.org/integration/autoland/rev/41fb31da1ab6
Don't observablely sniff objects in reportError(). r=smaug

Comment 4

[Web Platform Test Sync Bot (Matrix: #interop:mozilla.org)]

Created web-platform-tests PR https://github.com/web-platform-tests/wpt/pull/32144 for changes under testing/web-platform/tests

Comment 5

[Marian-Vasile Laza]

https://hg.mozilla.org/mozilla-central/rev/41fb31da1ab6

Comment 6

[Web Platform Test Sync Bot (Matrix: #interop:mozilla.org)]

Upstream PR merged by moz-wptsync-bot