Brave returning wrong OS version for MacOS

[ibeckermayer]

Description

The browser appears to be returning the wrong OS version, causing problems with Duo.

Steps to Reproduce

1. Attempt to authenticate with Duo with a certain minimum OS version requirement
2. Get "macOS update required. Your operating system needs to be updated before you can log in." despite running the latest version of macOS.

Actual result:

Expected result:

I should be able to follow through with login.

Reproduces how often:

Every time

Brave version (brave://version info)

Brave	1.56.20 Chromium: 115.0.5790.171 (Official Build) (arm64)
Revision	cf9067bf10d8f798c24643029af1d24e275646d6-refs/branch-heads/5790@{#1924}
OS	macOS Version 13.5.1 (Build 22G90)

Version/Channel Information:

• Can you reproduce this issue with the current release? Yes
• Can you reproduce this issue with the beta channel? Didn't check
• Can you reproduce this issue with the nightly channel? Didn't check

Other Additional Information:

• Does the issue resolve itself when disabling Brave Shields? Yes
• Does the issue resolve itself when disabling Brave Rewards? Didn't check
• Is the issue reproducible on the latest version of Chrome? No, Chrome works fine.

Miscellaneous Information:

Unfortunately I'm not sure how Duo is determining this information. navigator.platform and navigator.userAgent are returning the same things for me in both Chrome and Brave.

[pilgrim-brave]

Investigated this, and it is something we are doing intentionally. brave/brave-core#18154 added a "clamp" on navigator.userAgentData platformVersion so the third value is always 0. (For example, current Mac OS version is 13.5.2, but Brave intentionally returns 13.5.0.)

[mkarolin]

@ibeckermayer, could you, please, try going to brave://flags, searching for clamp-platform-version-client-hint and switching it to Disabled, then relaunching the browser and authenticating with Duo?

[ibeckermayer]

@mkarolin yes: that solves it.

[mkarolin]

Fixed via Griffin and brave/brave-core#20136

[mkarolin]

Marked as QA/No because Griffin change has already been tested by @kjozwiak