1690976 - (CVE-2021-23973) MediaError message property can leak information about cross-origin media resource

Status: RESOLVED FIXED

(Core :: Audio/Video: Playback, defect, P2)

Description

[Andreas Pehrson [:pehrsons]]

Similarly to bug 1450853, but while decoding instead of loading -- and setting the error through this path. I don't think this could leak any response status, but it can leak information about the content of the media resource. Things like this or this.

+++ This bug was initially created as a clone of Bug #1450853 +++

User Agent: Mozilla/5.0 (X11; Ubuntu; Linux x86_64; rv:58.0) Gecko/20100101 Firefox/58.0
Build ID: 20180208173149

Steps to reproduce:

1- Visit: https://output.jsbin.com/nejatopusi
2- Enter a URL in the input box, click the "Test" button
The URL will be loaded as the src of an audio element.

Actual results:

The message property of the MediaError interface contains a different string for resources that loads successfully. This allows an attacker to infer the response status for a cross-origin resource.

Expected results:

Cross-origin response status should not be detectable by scripts unless necessary CORS headers are sent by the server.

Comment 1

[Andreas Pehrson [:pehrsons]]

Attachment: Bug 1690976 - Add a mochitest checking that third-party ERR_DECODE messages are defaulted. r?bryce

Comment 2

[Andreas Pehrson [:pehrsons]]

Attachment: Bug 1690976 - Don't reveal error details for CORS-cross-origin decoding errors. r?bryce!,r?sstreich!

Comment 3

[Sebastian Hengst [:aryx] (needinfo me if it's about an intermittent or backout)]

Landed:
https://hg.mozilla.org/integration/autoland/rev/ff2dd7ee09b6281c248b046757c69dab70bb77e7
https://hg.mozilla.org/integration/autoland/rev/d119750e84691214a66216a053cb4a69209d0a2a

Backed out for failing modified test_decode_error_crossorigin.html:

https://hg.mozilla.org/integration/autoland/rev/283cfdca9a408ba3ac2e1c8b458e40eb1937d594

Push with failures: https://treeherder.mozilla.org/jobs?repo=autoland&group_state=expanded&resultStatus=testfailed%2Cbusted%2Cexception%2Cretry%2Cusercancel%2Crunnable&revision=d119750e84691214a66216a053cb4a69209d0a2a
Failure log: https://treeherder.mozilla.org/logviewer?job_id=329195723&repo=autoland

[task 2021-02-08T09:37:13.402Z] 09:37:13 INFO - TEST-PASS | dom/media/test/test_decode_error_crossorigin.html | At least one test led to src-not-supported
[task 2021-02-08T09:37:13.402Z] 09:37:13 INFO - Buffered messages finished
[task 2021-02-08T09:37:13.404Z] 09:37:13 INFO - TEST-UNEXPECTED-FAIL | dom/media/test/test_decode_error_crossorigin.html | At least one test led to a decode error
[task 2021-02-08T09:37:13.405Z] 09:37:13 INFO - SimpleTest.ok@SimpleTest/SimpleTest.js:417:16
[task 2021-02-08T09:37:13.405Z] 09:37:13 INFO - manager.onFinished@dom/media/test/test_decode_error_crossorigin.html:62:7
[task 2021-02-08T09:37:13.406Z] 09:37:13 INFO - MediaTestManager/this.nextTest@dom/media/test/manifest.js:2201:14
[task 2021-02-08T09:37:13.406Z] 09:37:13 INFO - MediaTestManager/this.finished@dom/media/test/manifest.js:2162:12
[task 2021-02-08T09:37:13.407Z] 09:37:13 INFO - startTest/<@dom/media/test/test_decode_error_crossorigin.html:36:13

Comment 4

[Sebastian Hengst [:aryx] (needinfo me if it's about an intermittent or backout)]

Landed:
https://hg.mozilla.org/integration/autoland/rev/c6c868eaf91531c82873e67950d457313d47d1f1
https://hg.mozilla.org/integration/autoland/rev/ed0ab9078607e373de6cc25ff31c28fc1c0e0120

Backed out for linting failure:

https://hg.mozilla.org/integration/autoland/rev/a83f064d141bd883af8a97d0d1a4cdfe3eee6967

Failure log: https://treeherder.mozilla.org/logviewer?job_id=329206209&repo=autoland
TEST-UNEXPECTED-ERROR | /builds/worker/checkouts/gecko/dom/media/test/test_decode_error_crossorigin.html:17:9 | 'ok' is assigned a value but never used. (no-unused-vars)

Comment 5

[Sebastian Hengst [:aryx] (needinfo me if it's about an intermittent or backout)]

Add a mochitest checking that third-party ERR_DECODE messages are defaulted. r=bryce
https://hg.mozilla.org/integration/autoland/rev/6c6ddcf74d79a7429dfaa315673174399b51bc4a
Don't reveal error details for CORS-cross-origin decoding errors. r=sstreich,bryce
https://hg.mozilla.org/integration/autoland/rev/7c861a1895759bd3878692c4e01f17a9b1a6847b
https://hg.mozilla.org/mozilla-central/rev/6c6ddcf74d79
https://hg.mozilla.org/mozilla-central/rev/7c861a189575

Comment 6

[Andreas Pehrson [:pehrsons]]

Comment on attachment 9201357 [details]
Bug 1690976 - Don't reveal error details for CORS-cross-origin decoding errors. r?bryce!,r?sstreich!

Beta/Release Uplift Approval Request

• User impact if declined: An adversary could figure out certain details about a media file on a third-party origin if we are able to load it but during playback exhibit an error.
• Is this code covered by automated tests?: Yes
• Has the fix been verified in Nightly?: No
• Needs manual test from QE?: No
• If yes, steps to reproduce:
• List of other uplifts needed: None
• Risk to taking this patch: Low
• Why is the change risky/not risky? (and alternatives if risky): This simply adds a case where we change the message component of an error to a default string. No threading changes, no lifetime changes.
• String changes made/needed:

ESR Uplift Approval Request

• If this is not a sec:{high,crit} bug, please state case for ESR consideration:
• User impact if declined: An adversary could figure out certain details about a media file on a third-party origin if we are able to load it but during playback exhibit an error.
• Fix Landed on Version: 87
• Risk to taking this patch: Low
• Why is the change risky/not risky? (and alternatives if risky): This simply adds a case where we change the message component of an error to a default string. No threading changes, no lifetime changes.
• String or UUID changes made by this patch:

Comment 7

[Pascal Chevrel:pascalc]

Comment on attachment 9201357 [details]
Bug 1690976 - Don't reveal error details for CORS-cross-origin decoding errors. r?bryce!,r?sstreich!

Approved for beta and esr, thanks.

Comment 8

[Julien Cristau [:jcristau]]

https://hg.mozilla.org/releases/mozilla-beta/rev/fb6be6072428
https://hg.mozilla.org/releases/mozilla-beta/rev/20ccf69d0a55

Comment 9

[Ryan VanderMeulen [:RyanVM]]

https://hg.mozilla.org/releases/mozilla-esr78/rev/3d7ae36fd0f1
https://hg.mozilla.org/releases/mozilla-esr78/rev/ad344d451325

Comment 10

[Tom Ritter [:tjr]]

Attachment: advisory.txt