Re: [Tails-dev] Tails 0.14 vs. iceweasel 10.0.9esr-1

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Author: sajolida
Date:  
To: The Tails public development discussion list
Subject: Re: [Tails-dev] Tails 0.14 vs. iceweasel 10.0.9esr-1
On 27/10/12 16:22, Ague Mill wrote:
> intrigeri:
>> a quickly tested ISO image, based on Tails 0.14~rc1, built from our
>> feature/torbrowser Git branch, should be available there in a hour or
>> so:
>>
>> http://dl.amnesia.boum.org/tails/testing/tails-i386-feature_torbrowser-0.14~rc1-20121024/
>>
>> It ships with iceweasel 10.0.9esr-1+tails1, that is iceweasel
>> 10.0.9esr-1 patched with (almost all) the torbrowser patches.
>
> I have done some tests and reviews.
>
> It lead me to discover a fingerprint issue related to window sizes. It
> also affects the TorBrowserBundle and has been reported here:
> https://trac.torproject.org/projects/tor/ticket/7222
>
> No comments on the implementation, except maybe that
> 0019-Adapt-Steven-Michaud-s-Mac-crashfix-patch.patch looks Mac only. But
> then, no harm done in applying it to our custom Iceweasel sources.
>
> So far, so good. My opinion is to push that to rc2. :)


I used that ISO while playing with browser fingerprint to compare Tails
0.14~rc2 and TBB 2.2.39-4. It worked fine.

The only difference I found (apart from the issue Ague discovered) is
about fonts detected using JavaScript.

Both Panopticlick and BrowserSpy only list fonts using Flash, so it is
not listing any font for neither Tails nor TBB. From what I understood,
there is no straight-forward technique to list available fonts using
JavaScript. The techniques I found rather check whether a given font is
available by comparing the graphical characteristics of a sample text
with the expected expected result with the original font.

Two of the tools I used showed differences between Tails and TBB:

http://ip-check.info/

I have no clue on how this number is calculated but it surely differs.
It also differs from the number of fonts returned for my non-torified
browser on the same system as the TBB.

Tails 0.14~rc2 gets 48 fonts installed.
TBB 2.2.39-4 gets 3 fonts installed.

http://www.lalit.org/lab/javascript-css-font-detect/

This one uses the technique described above to check for a set of 23
common fonts.

Tails gets 9 fonts out of 33.
TBB gets 33 fonts out of 33, even though some of them are not installed
on the system.

My question is does this difference in behavior make sense? Can it be
related to any existing TBB patch?