[hackerone] Extend font randomization fingerprinting protections to also cover src:local

[pes10k]

Currently Brave allows sites to access a random subset of user fonts, to cause fingerprinters get a different fingerprint for each site, for each browser session.

However, recently researchers notified use src:local to have Chrome bypass these protections and query all installed fonts again. We should also apply our randomize font fingerprinting protections against alternative ways of accessing user fonts, like src:local

These researchers will be credited on HackerOne.

https://hackerone.com/reports/1598008

credit: xlin

[stephendonner]

@pilgrim-brave @pes10k mind providing a testcase for this, please? 🙏

[pes10k]

@stephendonner https://dev-pages.brave.software/fingerprinting/fonts.html

[LaurenWags]

@pes10k to confirm - checking src:local case on that page for all platforms and then Pseudo Fonts on macOS only is sufficient?

btw - confirmed this with @pes10k 👍🏻

[stephendonner]

Verified PASSED using

Brave	1.44.85 Chromium: 105.0.5195.127 (Official Build) beta (x86_64)
Revision	912488396852bf658ab32465980c0b93a3c27a83-refs/branch-heads/5195@{#1109}
OS	macOS Version 11.7 (Build 20G817)

Steps:

Followed the steps to reproduce from https://dev-pages.brave.software/fingerprinting/fonts.html and https://dev-pages.bravesoftware.com/fingerprinting/fonts.html

Font setup	more

Confirmed the rendered texts were the same, as well as their width dimensions.

https://dev-pages.brave.software/fingerprinting/fonts.html

src:local	Pseudo Fonts

https://dev-pages.bravesoftware.com/fingerprinting/fonts.html

src:local	Pseudo Fonts

[MadhaviSeelam]

Verification PASSED using

Brave | 1.44.85 Chromium: 105.0.5195.127 (Official Build) beta (64-bit)
-- | --
Revision | 912488396852bf658ab32465980c0b93a3c27a83-refs/branch-heads/5195@{#1109}
OS | Windows 11 Version 21H2 (Build 22000.978)

1. Installed 1.44.85
2. launched Brave
3. open brave://settings/shields
4. confirmed Prevent sites from fingerprinting me based on my language preferences setting is ON/Enabled
5. confirmed Block fingerprinting setting is Standard
6. visit https://dev-pages.bravesoftware.com/fingerprinting/fonts.html
7. downloaded Fredoka one font as per the instructions on the page
8. clicked Start tests

Confirmed the rendered texts were the same, as well as their width dimensions.

Ex1	Ex2

[stephendonner]

Removing QA/Test-All-Platforms and replacing with OS/Windows and OS/macOS due to the feature not being enabled on Linux, per https://dev-pages.bravesoftware.com/fingerprinting/fonts.html:

[kjozwiak]

Removed OS/Android after speaking with @pilgrim-brave & @pes10k. The above hasn't been implemented in Android yet so there's nothing that QA can do in terms of verification on Android.