commit f33dc32759d65bdf39748f5df5dc6d19044b5a85 Author: Mike Perry mikeperry-git@torproject.org Date: Thu Nov 6 14:44:59 2014 -0800

Update design doc for 4.5-alpha-1. --- design-doc/design.xml | 87 ++++++++++++++++++++++++++++++++++--------------- 1 file changed, 60 insertions(+), 27 deletions(-)

diff --git a/design-doc/design.xml b/design-doc/design.xml index 914a84d..6e4bfc1 100644 --- a/design-doc/design.xml +++ b/design-doc/design.xml @@ -40,7 +40,7 @@ This document describes the <link linkend="adversary">adversary model</link>, linkend="Implementation">implementation</link> <!-- and <link linkend="Packaging">packaging</link> and <link linkend="Testing">testing procedures</link> --> of the Tor Browser. It is current as of Tor Browser -4.0. +4.5-alpha-1.

</para> <para> @@ -530,10 +530,14 @@ least <link linkend="fingerprinting">tracking their activities</link>. <listitem><command>History records and other on-disk information</command> <para> + In some cases, the adversary may opt for a heavy-handed approach, such as seizing the computers of all Tor users in an area (especially after narrowing the field by the above two pieces of information). History records and cache -data are the primary goals here. +data are the primary goals here. Secondary goals may include confirming +on-disk identifiers (such as hostname and disk-logged spoofed MAC adddress +history) obtained by other means. + </para> </listitem> </orderedlist> @@ -938,13 +942,6 @@ yet support IPv6). We have also verified that external protocol helpers, such as smb urls and other custom protocol handlers are all blocked.

</para> - <para> - -Numerous other third parties have also reviewed and tested the proxy settings -and have provided test cases based on their work. See in particular <ulink -url="http://decloak.net/%22%3Edecloak.net</ulink>. - - </para> </listitem>

<listitem>Disabling plugins @@ -1407,22 +1404,13 @@ Identity</command> invocations. </para> </listitem> <listitem>Exit node usage - <para><command>Design Goal:</command> - -Every distinct navigation session (as defined by a non-blank Referer header) -MUST exit through a fresh Tor circuit in Tor Browser to prevent exit node -observers from linking concurrent browsing activity. - - </para> - <para><command>Implementation Status:</command> + <para>

-The Tor feature that supports this ability only exists in the 0.2.3.x-alpha -series. <ulink -url="https://trac.torproject.org/projects/tor/ticket/3455%22%3ETicket -#3455</ulink> is the Torbutton ticket to make use of the new Tor -functionality. +All content elements associated with a given URL bar domain (including the +main page) are given a SOCKS username and password for this domain, which +causes Tor to isolate all of these requests on their own set of Tor circuits.

- </para> + </para> </listitem> </orderedlist> <para> @@ -1829,10 +1817,7 @@ the browser can obtain this clock skew via a mechanism similar to that used in <para><command>Implementation Status:</command>

We set the timezone using the TZ environment variable, which is supported on -all platforms. Additionally, we plan to <ulink -url="https://trac.torproject.org/projects/tor/ticket/3652%22%3Eobtain a clock -offset from Tor</ulink>, but this won't be available until Tor 0.2.3.x is in -use. +all platforms.

</para> </listitem> @@ -2037,6 +2022,46 @@ privacy and security issues.

</para> <orderedlist> + <listitem id="security-slider"><command>Security Slider</command> + <para> + +In order to provide vulnerability surface reduction for users that need high +security, we have implemented a "Security Slider" that essentially represents a +tradeoff between usability and security. Using metrics collected from +Mozilla's bugtracker, we analyzed the vulnerability counts of core components, +and used <ulink +url="https://github.com/iSECPartners/publications/tree/master/reports/Tor%20Brows... +gathered from a study performed by iSec Partners</ulink> to inform which +features should be disabled at which security levels. + + </para> + <para> + +The Security Slider consists of four positions. At the lowest security level +(the default), we disable +<command>gfx.font_rendering.graphite.enabled</command> for Latin locales, as +well as <command>gfx.font_rendering.graphite.enabled</command>. At the +medium-low level, we disable most Javascript JIT and related optimizations +(<command>javascript.options.ion.content</command>, +<command>javascript.options.typeinference</command>, +<command>javascript.options.asmjs</command>). We also make HTML5 media +click-to-play (<command>noscript.forbidMedia</command>), and disable WebAudio +(<command>media.webaudio.enabled</command>). At the medium-high level, we +disable the baseline JIT +(<command>javascript.options.baselinejit.content</command>), disable +Javascript entirely all elements that are loaded when the URL bar is not +HTTPS (<command>noscript.globalHttpsWhitelist</command>), and fully disable +graphite font rendering for all locales +(<command>gfx.font_rendering.graphite.enable</command>). At the highest level, +Javascript is fully disabled (<command>noscript.global</command>), as well as +all non-WebM HTML5 codecs (<command>media.ogg.enabled</command>, +<command>media.opus.enabled</command>, <command>media.opus.enabled</command>, +<command>media.DirectShow.enabled</command>, +<command>media.wave.enabled</command>, and +<command>media.apple.mp3.enabled</command>). + + </para> + </listitem> <listitem id="traffic-fingerprinting-defenses"><command>Website Traffic Fingerprinting Defenses</command> <para>

@@ -2146,6 +2171,14 @@ informs the user</ulink> that their browser is out of date.

</para> + <para> + +We also make use of the in-browser Mozilla updater, and have <ulink +url="https://gitweb.torproject.org/tor-browser.git/commitdiff/777695d09e3cff4c79c... +the updater</ulink> to avoid sending OS and Kernel version information as part +of its update pings. + + </para> </listitem>

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