1383495 - Spoofing Navigator API platform as Win64 when resisting fingerprinting is enabled

Status: RESOLVED FIXED

(Core :: DOM: Security, defect, P3)

Description

[Simon Mainey]

User Agent: Mozilla/5.0 (Windows NT 6.1; Win64; x64; rv:54.0) Gecko/20100101 Firefox/54.0
Build ID: 20170628075643

Steps to reproduce:

Firefox 56+, enable privacy.resistFingerprinting and test various methods of obtaining platform



Actual results:

Firefox 56+, the spoofed value is 32bit (win32) - see bug 1333651


Expected results:

Starting with 56, Mozilla will start 32-bit to 64-bit

[1] https://wiki.mozilla.org/Firefox/Win64
[2] https://bugzilla.mozilla.org/show_bug.cgi?id=1274659

Keeping an eye on metrics ( https://metrics.mozilla.com/firefox-hardware-report/ ), change the spoofed version to 64bit (win64) including the useragent when 64bit becomes more than 50%

Attention Arthur Edelstein [:arthuredelstein], Tim Huang[:timhuang], Tor Uplift

Comment 1

[Christoph Kerschbaumer [:ckerschb]]

Ethan, can you triage this one please?

Comment 2

[Ethan Tseng [:ethan]]

(In reply to Simon Mainey from comment #0)
> Expected results:
> Starting with 56, Mozilla will start 32-bit to 64-bit
> Keeping an eye on metrics (
> https://metrics.mozilla.com/firefox-hardware-report/ ), change the spoofed
> version to 64bit (win64) including the useragent when 64bit becomes more
> than 50%

This reason to spoof the value navigator.platform with 64-bit sounds fair to me.

Arthur and Tim, what would you think?

Comment 3

[Tim Huang[:timhuang]]

LGTM

Comment 4

[Simon Mainey]

I would also say that if you are spoofing the FF version ("rounded to the **nearest** 10" - my emphasis, straight from code comments - see https://reviewboard.mozilla.org/r/147474/diff/4#index_header ), then a FF60 32bit (in reality a FF56) looks ridiculous on the face of it, so I would even say this could land in FF56 - then again a FF60 looks strange as well right now.

Comment 5

[Ethan Tseng [:ethan]]

Per discussion in a meeting, Arthur agreed to spoof the value as win64 instead of win32.

Comment 6

[Simon Mainey]

Ethan: would it also be possible to revisit the version number spoofing. Rounding to the nearest 10 will highlight users that have privacy.resistFingerprinting=true when it rounds up and the spoofed value isn't even available - as will happen with 56. (also what happens when it ends in a 5 currently, does this become eg 50 or 60? I am aware this does not land until 56, just posing the question)

Would it not be better to code for
If version ends in 1 to 7, round down
If version ends in 8 or 9, round up
If version ends in zero, do nothing

Comment 7

[Simon Mainey]

On second thoughts, that doesn't cover those on Beta or Nightly. I know the idea is to make the subset of users with privacy.resistFingerprinting=true identical, and in this regard we could put anything. But why make this value stand out. Maybe it better to **always** round DOWN.

Comment 8

[Ethan Tseng [:ethan]]

(In reply to Simon Mainey from comment #4)
> I would also say that if you are spoofing the FF version ("rounded to the
> **nearest** 10" - my emphasis, straight from code comments - see
> https://reviewboard.mozilla.org/r/147474/diff/4#index_header ), then a FF60
> 32bit (in reality a FF56) looks ridiculous on the face of it, so I would
> even say this could land in FF56 - then again a FF60 looks strange as well
> right now.

Hi Simon,

Thank you for bring up this issue.
The commit message and code comments are not accurate.
According to the real code,
http://searchfox.org/mozilla-central/source/netwerk/protocol/http/nsHttpHandler.cpp#463
the spoofed value of Firefox version is always rounded down.

On Firefox 57, the spoofed value is "Firefox/50.0".

We should only update the code comments in this case.  :)

Comment 9

[Ethan Tseng [:ethan]]

Attachment: Bug 1383495 - Spoof navigator.platform as win64 when resisting fingerprinting is enabled

1. Change the spoofed version from "Win32" to "Win64".
2. Correct the code comment about the spoofed version.

Comment 10

[Ethan Tseng [:ethan]]

Hi Ehsan,
This is a minor change. Could you please review it?

Comment 11

[(no longer active)]

(In reply to Ethan Tseng [:ethan] from comment #10)
> Hi Ehsan,
> This is a minor change. Could you please review it?

Sure.  :-)  No need to needinfo BTW, setting the review flag is enough.

Comment 12

[(no longer active)]

Comment on attachment 8895658 [details] [diff] [review]
Bug 1383495 - Spoof navigator.platform as win64 when resisting fingerprinting is enabled

Review of attachment 8895658 [details] [diff] [review]:
-----------------------------------------------------------------

Thanks!  It would be nice to uplift this into 56 if possible.  Do you mind nominating this for beta approval please?  It's pretty low risk so I hope the release managers will approve it.

Comment 13

[Ethan Tseng [:ethan]]

(In reply to :Ehsan Akhgari (needinfo please, extremely long backlog) from comment #12)
> Thanks!  It would be nice to uplift this into 56 if possible.  Do you mind
> nominating this for beta approval please?  It's pretty low risk so I hope
> the release managers will approve it.

Sure!  I will nominate it after it's landed in central.
Thank you, Ehsan.

Comment 14

[Simon Mainey]

"The browser version will be rounded down to the multiple of 10"

Sounds a bit weird to me, can we change "the" to "a"

"The browser version will be rounded down to a multiple of 10"

Comment 15

[Ethan Tseng [:ethan]]

(In reply to Simon Mainey from comment #14)
> "The browser version will be rounded down to the multiple of 10"
> Sounds a bit weird to me, can we change "the" to "a"
> "The browser version will be rounded down to a multiple of 10"

You are right. I'll fix it. Thanks!

Comment 16

[Ethan Tseng [:ethan]]

Attachment: Spoofing Navigator API platform as win64 when resisting fingerprinting is enabled

1. Update commit message "r=Ehsan".
2. Fix a grammar error based on comment 14.

Comment 17

[Ethan Tseng [:ethan]]

https://treeherder.mozilla.org/#/jobs?repo=try&revision=785b86858b3657fa5efdf6347b587f0dec4c55af

Comment 18

[Pulsebot]

Pushed by [e-mail]:
https://hg.mozilla.org/integration/mozilla-inbound/rev/5451feeb0448
Spoof Navigator API platform as win64 when resisting fingerprinting is enabled. r=ehsan

Comment 19

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

https://hg.mozilla.org/mozilla-central/rev/5451feeb0448

Comment 20

[Ethan Tseng [:ethan]]

Comment on attachment 8896179 [details] [diff] [review]
Spoofing Navigator API platform as win64 when resisting fingerprinting is enabled

Approval Request Comment
[Feature/Bug causing the regression]: N/A
[User impact if declined]: The spoofed value of platform would not be convincing
[Is this code covered by automated tests?]: Yes
[Has the fix been verified in Nightly?]: Yes
[Needs manual test from QE? If yes, steps to reproduce]: No
[List of other uplifts needed for the feature/fix]: N/A
[Is the change risky?]: No
[Why is the change risky/not risky?]: Only two constant definitions were changed
[String changes made/needed]: N/A

Also, Ehsan suggested to uplift this to Beta. See comment 12.

Comment 21

[Gerry Chang [:gchang]]

Comment on attachment 8896179 [details] [diff] [review]
Spoofing Navigator API platform as win64 when resisting fingerprinting is enabled

Fix a Spoofing Navigator API platform value. Beta56+. Should be in 56.0b3.

Comment 22

[Ryan VanderMeulen [:RyanVM]]

https://hg.mozilla.org/releases/mozilla-beta/rev/428d62670f7e

Comment 23

[Anna]

OSCPU should also be changed to 'Windows NT 6.1; Win64; x64', see http://browserspy.dk/showprop.php?navigator with and w/o resistFingerprinting on a Windows 7 x64 with Firefox x64

Comment 24

[Ethan Tseng [:ethan]]

(In reply to Anna from comment #23)
> OSCPU should also be changed to 'Windows NT 6.1; Win64; x64', see
> http://browserspy.dk/showprop.php?navigator with and w/o
> resistFingerprinting on a Windows 7 x64 with Firefox x64

You are right. Thanks for pointing this out.
I will file a bug to change this.

Comment 25

[Ethan Tseng [:ethan]]

Reference for Navigator.oscpu:
https://developer.mozilla.org/en-US/docs/Web/API/Navigator/oscpu
http://docs.w3cub.com/dom/navigator/oscpu/