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by chjj 20 days ago
I think they made the right call on that. It's unclear to me whether hiding the OS is even possible. There's just too much OS-specific behavior that happens inside (and outside) a web browser. It's hard to account for all of it.

OS rendering differences can likely betray you even when canvas extraction is blocked/noised. At least one tor-browser dev has publicly confirmed that you can't even hide the difference between X11 and Wayland[1], nevermind two entirely different OSes.

[1] https://forum.torproject.org/t/linux-is-it-alright-to-run-th...
1 comments
coppsilgold 20 days ago
It's not surprising that JS would out you, what I am wondering if whether or not volunteering OS information is foolish when it may not be possible to determine without JS.

Why give up information when you don't have to? Some people disable JS at least some of the time.

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chjj 20 days ago
> Why give up information when you don't have to?

Yeah, I generally agree with that viewpoint, but you are giving up that information, even without JS.

Your TCP stack can be fingerprinted through long enough observation. Windows, Mac, and Linux all look different on a network level. It's not as simple `if XYZ then OS = Windows`, it's more holistic/probabilistic, but it's possible nonetheless.

e.g. One thing that bugs me about arch linux is that they recently changed the kernel default TCP keepalive time to be shorter (much shorter[1]), making arch users stand out a lot. So, not only can a fingerprinter identify your OS, they might be able to pin down your exact distro based on TCP behavior alone.

I guess my point is that hiding the OS would be a massive amount of effort to plug a hole that cannot be plugged without effectively controlling the entire OS. TB/MVB is limited in what it can do by itself.

[1] https://rfc.archlinux.page/0051-tcp-keepalive/

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coppsilgold 20 days ago
> TCP stack can be fingerprinted

How does that apply to Tor? It uses custom packets. The entry node may be able to obtain a TCP fingerprint but that's all.

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chjj 20 days ago
It doesn't. This case applies more to MVB.
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