Fingerprinting 2.0: User Agent - follow up to 9190

[LaurenWags]

Per #9190 (comment), #9190 should be tested with 1.17.x when all of the code has landed.

Test plan for both Desktop and Android (per #9190 (comment)):

per @pes10k comment:
i've added a user-agent row to https://dev-pages.brave.software/farbling.html

Things to check:

1. using an android device, hit the "generate fingerprints" button, then click on one of the hash values in that row and make sure that in the popup it says "android device" and not any particular device model
2. in "strict" blocking, you should get different fingerprints across top-level origins and sessions (there aren't a huge number of possible random values here, so if you see an identical fingerprint (for the user-agent row only), its worth checking on the sibling page or on another session to see if you get another fingerprint then)

Original issue description

This is a sub-issue of the larger fingerprint defense reorganization issue: #8787

User Agent String

NavigatorID.userAgent

default protections:

• for devices with OS version numbers, always report MAX(current minor version number, latest version number as of build)
• (only for android) don't report device name in UA, only return "android device" (same as what DDG browser does)

max protections:

• return chrome default UA for each platform
• At end of UA, add [0, 5] additional whitespace characters, as determined by eTLD+1 seed (only for JS reflected value)

(other notes for future consideration)
In default mode, we could probably get by safely with adding [0, 5] additional whitespace characters, as determined by eTLD+1 seed (only for JS reflected value), but for the first time out, lets be very very conservative with the UA and not make any "clever" changes like that.

Also, we could probably get by with adding [0, 3] additional whitespace characters between UA segments, but again, for the first change, lets be conservative.

[LaurenWags]

Verified passed with

Brave | 1.17.55 Chromium: 86.0.4240.111 (Official Build) dev (x86_64)
-- | --
Revision | b8c36128a06ebad76af51591bfec980224db5522-refs/branch-heads/4240@{#1290}
OS | macOS Version 10.14.6 (Build 18G6032)

Verified test plan from description

Using https://dev-pages.brave.software/farbling.html and https://dev-pages.bravesoftware.com/farbling.html, confirmed:

When FP = strict, the "User Agent" row has the same values in each column and the values differ between the two pages

If I relaunch and generate fingerprints again, when FP = strict, the "User Agent" row values differ from previous session (values are not retained on each page per session). Note, issue description notes limited values so duplicate values are possible

Logged #12392 as a follow up for the Worker column value not matching the other values in the User Agent row. Note, this value is the same as when FP = standard or shields are off.

FP=standard

Shields off

---

Verification passed on

Brave	1.17.62 Chromium: 86.0.4240.185 (Official Build) dev (64-bit)
Revision	37e6f852ed18086458552039ad26421aa9fc7acc-refs/branch-heads/4240@{#1377}
OS	Windows 7 Service Pack 1 (Build 7601.24544)

Verified test plan from description

Using https://dev-pages.brave.software/farbling.html and https://dev-pages.bravesoftware.com/farbling.html, confirmed:

When FP = strict, the "User Agent" row has the same values in each column and the values differ between the two pages

If I relaunch and generate fingerprints again, when FP = strict, the "User Agent" row values differ from previous session (values are not retained on each page per session). Note, issue description notes limited values so duplicate values are possible

Encountered #12392

FP=standard


Shields off

---

Verification passed on

Brave	1.17.59 Chromium: 86.0.4240.183 (Official Build) dev (64-bit)
Revision	0b568b034b8f7994697cb341eeca5979b84151cc-refs/branch-heads/4240@{#1374}
OS	Ubuntu 18.04 LTS

Verified test plan from description

Using https://dev-pages.brave.software/farbling.html and https://dev-pages.bravesoftware.com/farbling.html, confirmed:

When FP = strict, the "User Agent" row has the same values in each column and the values differ between the two pages

If I relaunch and generate fingerprints again, when FP = strict, the "User Agent" row values differ from previous session (values are not retained on each page per session). Note, issue description notes limited values so duplicate values are possible

Encountered #12392

FP=standard

Shields off

[srirambv]

Removing Android label as a followup issue #12638 is logged