The Tor Browser Hacking Guide

Welcome to the Official Tor Browser Hacking Guide. This page is meant to give you an overview of how to get started with Tor Browser development.

This page covers building the browser, debugging the browser, how we communicate and use trac to organize our issues and development process, what goes into the browser itself, and also provides links to other development resources and information.

Ways to Build Tor Browser

The first thing you probably want to know is how to obtain the very latest (and sometimes greatest) Tor Browser builds, and how to build your own version of the Tor Browser from our source code. Well wait no further.

Nightly Builds

Currently, nightly builds are available ​on a .onion site managed by boklm who is part of the Tor Browser team.

As with all of our builds, it should be possible to reproduce byte-for-byte identical versions of all of those binaries from source. To learn how to do that, read on.

Building Official Tor Browser Release Binaries

Our build system is based on ​rbm, which is developed by boklm. rbm is using ​runc to provide a clean, controlled, reproducible build environment in a fully automated fashion. We further wrap rbm with our own helper scripts that download and authenticate inputs, and automate building and assembling each component piece of the browser into a final set of output packages for Linux, MacOS, and Windows. This is done with code in the ​tor-browser-build repository.

This system enables us to provide secure, verifiable, byte-for-byte reproducible builds to ensure the integrity of our binaries and to protect the build process from compromise. We have written a pair of blog posts that describe in more detail ​why this is important, and the ​technical details behind how this previously got achieved when using the ​Gitian system, if you are curious. The new build system based on rbm is working similarly and is facing pretty much the same issues.

To build the Tor Browser, you need essentially a Linux system with runc support. Once that is done, check out a copy of the tor-browser-build repo with:

git clone https://git.torproject.org/builders/tor-browser-build.git
cd tor-browser-build

After that you might need to install the additional dependencies ​mentioned in the README file and you should be able to run 'make', 'make alpha', 'make nightly', or 'make testbuild' to build the entire bundle for all three platforms. The build scripts will detect any additional packages or configuration you need to perform on your system.

Inside that directory you will also see a ​README.BUILD_ERRORS file with further information, should you run into any issues.

Reproducing an Existing Build

The Tor Browser build process is using signed tags for official builds. Stable tags follow the scheme 'tbb-X.X.X-buildN' where 'X' are figures building the version number (like '7.5') and 'buildN' specifies the build number for this particular browser version (e.g. 'build3'). Tags for the alpha releases are similar but contain an 'a' in it like 'tbb-8.0a1-build3'.

Once you know which version you want to reproduce check out the tag containing the latest build number and start doing a 'make' if it is a stable version or 'make alpha' if it is part of the alpha series.

At the end of the build you should end up with a 'sha256sums-unsigned-build.txt' file containing all the SHA-256 sums of the bundles and related packages in alpha/unsigned/your-tor-browser-version (or release/unsigned/your-tor-browser-version, respectively). They should match the official hash sums we have produced.

Be aware that this process is not fully future-proof. In particular, if Debian has updated their development tool chain since the bundles have been built, you may encounter differences between your resulting bundles and the original binaries. This should be rare, however, as we use only the "Long Term Support" or "Oldstable" of Debian in our build VMs. The only reason they should change the tool chain is in the event of serious security issues in the development tools themselves.

Partial Builds

This section is mostly of interest to developers making changes to Tor Browser or its components, and who wish to test their patches.

Building Just Firefox

If you want to just develop on the browser without messing with gitian (for example, to have incremental rebuilds of just the files you modify), the best way is to build a new browser distribution and copy the result over an existing Tor Browser directory. Clone the ​Tor Browser repo.

To build it, from the top directory of the tor-browser repo, do:

# Install a subset of the packages listed in
# https://gitweb.torproject.org/builders/tor-browser-bundle.git/tree/gitian/descriptors/linux/gitian-firefox.yml#l8
# Mostly, we don't need `libiw-dev` or `faketime`, but we *do* need `pkg-config`.

sudo torsocks apt-get install \
    --no-install-suggests --no-install-recommends \
    zip \
    unzip \
    libglib2.0-dev \
    libgconf2-dev \
    libgtk2.0-dev \
    libdbus-1-dev \
    libdbus-glib-1-dev \
    yasm \
    libasound2-dev \
    libcurl4-openssl-dev \
    libxt-dev \
    mesa-common-dev \
    autoconf \
    autoconf2.13 \
    libtool \
    hardening-wrapper \
    libgstreamer-plugins-base0.10-dev \
    pkg-config \
    g++ \
    libpulse-dev

# On Ubuntu 17.10 gcc and g++ are version 7
# when used firefox gets a bunch of weird rendering issues so we have to force usage of gcc and g++ version 6

sudo torsocks apt-get install gcc-6 g++-6

# Add following lines to .mozconfig in tor-browser root:
export CC=gcc-6
export CXX=g++-6

# Generate the configure scripts:
make $CONFIGURE_ARGS -f client.mk configure CONFIGURE_ARGS="--with-tor-browser-version=tbb-nightly --with-distribution-id=org.torproject --enable-update-channel=default --enable-bundled-fonts"

# And... compile:
make $MAKEOPTS -f client.mk build
make -C obj-* package INNER_MAKE_PACKAGE=true

# Point the INSTDIR at an existing TBB directory:
export INSTDIR="$HOME/tbb/test/tor-browser_en-US"

# Move the compiled firefox on top of the old TBB browser dir:
cp -a obj-*/dist/firefox/* $INSTDIR/Browser/

# If you want a smaller binary to copy into a vm/other machine for tests:
strip --strip-all $INSTDIR/Browser/*
rm -f $INSTDIR/Browser/firefox-bin

If that completes successfully, then your fresh build of Firefox should exist at $INSTDIR/Browser/firefox. Free the lizard.

Building Just Tor Launcher Or Torbutton

If you are only modifying one of our support addons (such as Tor Launcher or Torbutton) then you only need to create a new XPI and then copy it into an existing bundle.

For Tor Launcher:

# Point the INSTDIR at an existing TBB directory:
export INSTDIR="$HOME/tbb/test/tor-browser_en-US"

git clone https://git.torproject.org/tor-launcher.git
cd tor-launcher
# do some work
make package # should give you an xpi under ./pkg. Note the full filename and version in the output
cp pkg/tor-launcher-0.2.7.6.xpi $INSTDIR/Browser/TorBrowser/Data/Browser/profile.default/extensions/tor-launcher@torproject.org.xpi

For Torbutton:

# Point the INSTDIR at an existing TBB directory:
export INSTDIR="$HOME/tbb/test/tor-browser_en-US"

git clone https://git.torproject.org/torbutton.git
cd torbutton
# do some work
./makexpi.sh # Will create an xpi in pkg, but you need to find the version for the next step
cp pkg/torbutton-1.9.3.1.xpi $INSTDIR/Browser/TorBrowser/Data/Browser/profile.default/extensions/torbutton@torproject.org.xpi

Now, you should be able to start Tor Browser in $INSTDIR normally. To run multiple copies at once, see the next section.

Building Orfox

This section is of interest to developers making changes to Tor Browser Mobile or its components (e.g. Orbot), and who wish to test their patches.

Orfox

First, you need to check out a copy of the Orfox browser and fetch all sub modules with:

git clone https://github.com/guardianproject/Orfox.git
cd Orfox
git submodule update --init --recursive

Later, instead of downloading dependency by dependency, you can use Mozilla bootstrap command to download all of them at once.

cd external/tor-browser
./mach bootstrap

Now we need to use the Orfox mozconfig and update it.

export MOZCONFIG=`pwd`"/external/tor-browser/.mozconfig-orfox-release"

Open the .mozconfig-orfox-release file and replace the $NDK_BASE and $SDK_BASE with the path to the installed Android NDK and SDK, respectively.

Now we can build it and generate the APK

./mach configure
./mach build
./mach package
./mach build-backend -b AndroidEclipse

That is it, if you want to run it, you can use the Android adb tool or

./mach run

It will install and run in your android device.

Orbot

If you want to modify Orbot, this section is for you:

Dependencies

Dependency	version
Android SDK Tools	25
Android Build Tools	26.0.2
Android NDK	r11b

Fetching and Building

First, you need to check out a copy of the orbot repo with:

git clone https://github.com/n8fr8/orbot.git
cd orbot
git submodule update --init --recursive

To build it (in debug mode), from the top directory of the orbot repo, do:

./gradlew assembleDebug

The command will generate an APK (self signed) that can be used in you device or simulator.

Running Multiple Tor Browsers

Now that you have a developer build (or several builds), you probably want to know how to run more than one of them at once. There are two main ways to do this: reusing an existing Tor process, and launching Tor process on a new pair of SOCKS and Control ports.

Using an Existing Tor Process

Let's assume that Tor process is listening on port 9150 for SOCKS, and 9151 for the control port.

export TOR_SOCKS_PORT=9150
export TOR_CONTROL_PORT=9151
export TOR_CONTROL_COOKIE_AUTH_FILE=~/tbb/tor-browser_en-US/Browser/TorBrowser/Data/Tor/control_auth_cookie
export TOR_SKIP_LAUNCH=1

cd $INSTDIR # from the 'Partial Builds' section above
./start-tor-browser.desktop

Launching Tor with an Alternate SOCKS and Control port

If you need to test Tor Launcher changes, you probably want to launch the Tor process too. Here's a quick hack to put that on a different port pair (9250 and 9251):

export TOR_SOCKS_PORT=9250
export TOR_CONTROL_PORT=9251
unset TOR_SKIP_LAUNCH
unset TOR_CONTROL_COOKIE_AUTH_FILE

cd $INSTDIR   # From the 'Partial Builds' section above
sed -i -e 's/Port 915/Port 925/' ./Browser/TorBrowser/Data/Tor/torrc-defaults
./start-tor-browser.desktop

Tor Browser Team Communication and Organizational Patterns

The Tor Browser development team is very geographically distributed. We use a few different written forms of communication to discuss development over the Internet: Mailing lists, IRC, and this bug tracker. We also hold weekly IRC meetings.

Communication Mechanisms and Meetings

The mailinglist for Tor Browser development discussion is ​tbb-dev. You can also subscribe to the list of Tor Browser code commits via ​tbb-commits. All updates to Tor Browser specific bugs are sent to ​tbb-bugs. Release tags and test builds are posted to ​tor-qa for community review and testing.

Our primary mode of day-to-day communication is the #tor-dev IRC channel on irc.oftc.net (port 6697 is ssl). We hold weekly meetings on this IRC channel at 19:00 UTC on Mondays. For details on our meeting format, please see the ​original meeting announcement post (note however that the time has changed since that posting).

How we use Trac

For historical reasons, Tor Browser tickets are spread across several Trac components: "Tor bundles/installation", "TorBrowserButton", "Firefox Patch Issues", and "Tor Launcher". We are considering consolidating many of these components and switching to keywords instead, but that hasn't happened yet.

Trac Keywords

What follows is a partial list of trac keywords we use to categorize issues, independent of the component they actually arise in.

tbb-crash

Tickets that represent reported crash or hang issues

tbb-usability

Tickets that represent usability issues. Has many subcategories as suffixes of tbb-usability.

tbb-usability-stoppoint

Tickets that represent usability issues that cause users to be unable to use TBB (this is a subset of the previous query)

tbb-helpdesk-frequent

Tickets that represent frequently encountered support issues or blog/twitter commentary

tbb-linkability

Tickets that represent a violation of our identifier unlinkability ​Privacy Requirement.

tbb-fingerprinting

Tickets that represent a violation of our fingerprinting unlinkability ​Privacy Requirement. There are many subcategories of this tag as suffixes.

tbb-disk-leak

Tickets that represent a violation of our Disk Avoidance ​Security Requirement.

tbb-newnym

Tickets for problems with "New Identity"

tbb-testcase

Tickets for which we would like to have an automated testcase to prevent regressions.

tbb-security

Tickets for hardening TBB against exploitation.

tbb-needs

Tickets in other Tor components that TBB needs solved.

tbb-mobile

Tickets for work on Tor Browser for mobile in particular

tbb-spec

Tickets for work on Tor Browser's design documentation

tbb-security-slider

Tickets for work on Tor Browser's security slider

In addition to this list, if you would like someone to review a patch, you should set the state of that ticket to "needs review" and tag it that that person's name, followed by the year, the month, and the letter 'R'. For example: MikePerry201311R.

Design and Core Components

Ok, so you've got the lay of the land now, and want to really dive in. Here's how everything is organized.

Design Document

At a high level, Tor Browser development is driven by the design document: ​The Design and Implementation of the Tor Browser. This document specifies the ​Design Requirements and Philosophy that guides our development decisions and our modifications to Firefox, provides an ​adversary model, and provides a ​high level description of the actual changes we have made to Firefox.

Component Source Repositories

The Tor Browser is actually built from several components. Here are the main ones specific to the browser itself.

Firefox Branch Repo

We maintain a branch of the latest Firefox "​Extended Support Release" (ESR) series, to which we have applied multiple patches to satisfy our design requirements and build security needs.

These branches live in the ​tor-browser git repo. The branches are named for the Firefox version they are based off of, along with an integer signifying a rebase number. To learn which branch a particular build uses, inspect its version file. The version file lists a tag for the specific commit used. This tag is derived from the branch name and an additional specific build number.

Torbutton

​Torbutton is an addon with a long and storied history. It originated as ProxyButton (a simple Firefox addon to toggle proxy settings), which was rethemed by Scott Squires and configured specifically for Tor's proxy settings. After that initial work, Mike Perry began development to address the numerous security issues that arose when browser state from non-Tor activity leaked into Tor browsing mode, and vice-versa. This toggle mode was ​deprecated in favor of a standalone browser several years back.

As a result, Torbutton contains a lot of cruft code specific to the toggle behavior that has not yet been removed, but is otherwise inactive. However, it still provides a few privacy features by way of observers and other extension-level changes to Firefox to improve privacy and Tor security.

Tor Launcher

​Tor Launcher is a Firefox addon that acts as a Tor Controller. It handles launching and configuring Tor for use with the browser. It also is compatible with Thunderbird, InstantBird, and XULRunner, and is used by the ​Tails project as well.

HTTPS-Everywhere

​HTTPS-Everywhere contains tens of thousands of URL rewrite rules to enforce HTTPS for sites that support both HTTP and HTTPS URL schemes.

NoScript

We don't modify NoScript directly, however we do have a number of preferences changes to it and other addons in the ​tor-browser-bundle preferences file in the bundle layout directories.

If you're interested in bisecting or otherwise tracking down a particular NoScript change, bug, or issue, avian2 maintains a complete ​git repository for NoScript, with one commit per NoScript release (including alphas, betas, and rc releases).

Pluggable Transports

Tor Browser includes several ​pluggable transports, which are a network traffic transformation layer to help avoid censorship and filtering mechanisms. If you are interested in getting your own pluggable transport added to the bundle, the FTE transport work is a good example to follow.

The original ticket for FTE is a good starting point. It resulted in a ​clean branch that merged easily.

Pluggable Transport Bridges are specified in ​the bridge_prefs.js configuration file in the Bundle Skeleton directory.

Debugging the Tor Browser

There are a few different ways to debug the Tor Browser, depending on the component involved. We'll focus on the extensions and the browser itself here.

Enabling debug logs in extensions

To enable extension debug logging, set these preferences in your about:config:

SETTING NAME	VALUE
extensions.torbutton.loglevel	2
extensions.torbutton.logmethod	0
extensions.https_everywhere.LogLevel	2
extensions.https_everywhere.log_to_stdout	true
extensions.torlauncher.loglevel	2
extensions.torlauncher.logmethod	0

Lower levels are more verbose, but if you go much below 2, you will likely be overwhelmed and/or the browser will be extremely slow.

If you want to save your logs to a file, you need to use the --log argument to start-tor-browser.desktop. It takes an optional filename. Without a filename, it writes tor-browser.log in the current directory:

$ ./start-tor-browser.desktop --log
$ tail -f tor-browser.log

Using the Javascript Debugger

XXX: Write or link to some documentation on using Venkman/JSD for extension debugging. There are two options for this: Venkman and the in-browser debugger. For TBB pre-5.0, Venkman was the way (​https://addons.mozilla.org/en-us/firefox/addon/javascript-debugger/). However, it is no longer supported. Instead, the built-in debugger must be used: ​https://developer.mozilla.org/en-US/docs/Debugging_JavaScript#JavaScript_Debugger

Using gdb

Using Debug Symbols

If you're going to use GDB to debug an issue, the first thing you want is debug symbols. Tor Browser builds detached debug symbols for tor and firefox.

In the bundle release download directory there should be a tor-browser-linux64-debug.zip file. Unfortunately, the directory structure of the debug zip doesn't exactly match what you need in order for gdb to find the symbols automatically. For the tor-browser-linux symbols, unzip the file in the bundle root directory, and then relocate it to the .debug subdirectory of Browser, like so:

$ cd tor-browser_en-US
$ wget https://dist.torproject.org/torbrowser/5.0a3/tor-browser-linux64-debug.zip
$ unzip tor-browser-linux64-debug.zip
$ mv Debug/Browser Browser/.debug
$ gdb ./Browser/firefox

At this point, gdb should find all of the Firefox symbols automatically upon every invocation, and you can either attach to an existing process ID or launch firefox directly, as described in the following sections below.

Attaching an already running TBB

You can attach a gdb instance to an already running TBB firefox process. To do this, find the pid of your running TBB firefox, then tell gdb to attach the running process (note that on some systems you may need to run gdb as root for this to work):

$ for p in `pgrep firefox` ; do ps -v $p ; done
[...find the pid for your TBB firefox...]
$ gdb ./Browser/firefox
(gdb) attach <pid>

Starting firefox from inside gdb

Starting firefox inside gdb:

 $ gdb ./Browser/firefox
 (gdb) set env LD_LIBRARY_PATH=Browser/TorBrowser/Tor
 (gdb) run -profile Browser/TorBrowser/Data/Browser/profile.default

Generating and debugging core files

If you have a condition that crashes Tor Browser in an unreliable way, one helpful step is to generate a core file for crashes that do happen. To do this, before launching Tor Browser, run:

$ ulimit -c unlimited

Then, when Tor Browser crashes, a core file should show up in Browser/core. To debug this core, run:

$ gdb ./Browser/firefox ./Browser/core

You can then use the usual gdb commands (backtrace, print, up, down, etc) to inspect the stack, variables, and program state at the time of the crash.

Debugging ASan/selfrando builds

If you need to debug a hardened build that includes ​ASan and ​selfrando you have two options.

Temporarily disable selfrando

If you set the environmental variable SELFRANDO_skip_shuffle, selfrando will be disabled and gdb will work as usual. E.g.:

$ gdb -ex "set env LD_LIBRARY_PATH=$PWD/Browser/TorBrowser/Tor" -ex "set env SELFRANDO_skip_shuffle=" \
        -ex 'set env ASAN_OPTIONS="detect_leaks=0,abort_on_error=1"' -ex "set env NSS_DISABLE_HW_AES=1" \
        --args Browser/firefox -profile Browser/TorBrowser/Data/Browser/profile.default/

Convert ASan's stack trace message

This method can be used only to debug a crash. Start Tor Browser with Browser/start-tor-browser -v. After the browser crashes, you will see one or more stack traces that look like this:

==3896==ERROR: AddressSanitizer: heap-use-after-free on address 0x6040003b85e0 at pc 0x7f5dff50f35d bp 0x7ffe516e3a90 sp 0x7ffe516e3a88
READ of size 4 at 0x6040003b85e0 thread T0
SRAT init
    #0 0x7f5dff50f35c  (/path/to/directory/tor-browser/Browser/libxul.so+0x4af0a9a)
    #1 0x7f5dfe153916  (/path/to/directory/tor-browser/Browser/libxul.so+0x4af0d32)
    #2 0x7f5e001ae7f6  (/path/to/directory/tor-browser/Browser/libxul.so+0x392d7e8)
[...]
    #43 0x418d98  (/path/to/directory/tor-browser/Browser/firefox+0x4089dc)
    #44 0x7f5e0b0d8f44 in __libc_start_main (/lib/x86_64-linux-gnu/libc.so.6+0x21f44)
    #45 0x41e9dc  (/path/to/directory/tor-browser/Browser/firefox+0x408e34)

To get a meaningful stack trace you need to install a symbolizer (you can install clang and use llvm-symbolizer). Then, copy the relevant text from ASan's output, pipe it trough convert-asan-to-symbolizer.py​ and then into the symbolizer. E.g.:

$ xsel -b | ./convert-asan-to-symbolizer.py | llvm-symbolizer-3.4

The script assumes that debug information is available in Browser/.debug (see Using Debug Symbols).

Using dtrace

Dtrace is a very powerful tracing and debugging system that requires kernel support, however all the grown-up Operating Systems support it (not supported by Linux). Like many of the powerful creations of Unix, dtrace immediately gave rise to an orgy of one-liners. That is, one-line dtrace programs that perform a useful task! Like awk, there are many such dtrace one-liners that people have documented and are still useful today, often with little or no modification. In fact, you can utilize both dtrace and awk in the same command pipeline to create something even more expressive!

The IllumOS (the new OpenSolaris) kernel has support for Linux zones which can run native x86 32bit and 64bit binaries in an isolated environment. They have done such a good job at this Linux binary system call emulation that it can run all the normal stuff including systemd and other monstrosities such as htop. ;-p My Debian 8 image indeed acts like a normal Debian 8 system... although it is definitely not running the Linux kernel.

The host's global zone can be used to dtrace native Linux and Solaris zones. Tor Browser Bundle runs fine using the Linux zones.

Isolating tor applications with SmartOS

onion -> noVNC http -> vnc4server -> tbb

more dtrace examples ​https://wiki.smartos.org/display/DOC/DTrace

dtrace examples for Tor Browser Bundle

Many of these examples collect dtrace probe information until the operator hits control-c. I found many dtrace exmamples. Here's some that might be useful:

Which files does firefox open?

dtrace -n 'lx-syscall::open*:entry /execname == "firefox"/ { printf("%s %s", execname, copyinstr(arg0)); }
'
dtrace: description 'lx-syscall::open*:entry ' matched 6 probes
CPU     ID                    FUNCTION:NAME
  0   3874                       open:entry firefox /dev/urandom
  0   3874                       open:entry firefox /home/human/tor-browser_en-US/Browser/TorBrowser/Tor/libcanberra.so.0
  0   3874                       open:entry firefox /etc/ld.so.cache
  0   3874                       open:entry firefox /lib/x86_64-linux-gnu/libcanberra.so.0
  0   3874                       open:entry firefox /usr/lib/x86_64-linux-gnu/libcanberra.so.0
  0   3874                       open:entry firefox /lib/libcanberra.so.0
  0   3874                       open:entry firefox /usr/lib/libcanberra.so.0
  0   3874                       open:entry firefox /home/human/tor-browser_en-US/Browser/TorBrowser/Tor/libcanberra.so.0
  0   3874                       open:entry firefox /etc/ld.so.cache
  0   3874                       open:entry firefox /lib/x86_64-linux-gnu/libcanberra.so.0
  0   3874                       open:entry firefox /usr/lib/x86_64-linux-gnu/libcanberra.so.0
  0   3874                       open:entry firefox /lib/libcanberra.so.0
  0   3874                       open:entry firefox /usr/lib/libcanberra.so.0
  0   3874                       open:entry firefox /dev/urandom
  0   3874                       open:entry firefox /dev/urandom
^C

syscall frequency count

dtrace -n 'lx-syscall:::entry /pid == 44622/ { @num[probefunc] = count(); }'
dtrace: description 'lx-syscall:::entry ' matched 676 probes
^C

  read                                                            725
  write                                                           725
  writev                                                         1400
  futex                                                          3548
  poll                                                           5686
  recvmsg                                                        6911
  clock_gettime                                                 17440

function and module top 10 frequency count lx_proc_func_count.d

#!/usr/sbin/dtrace -s
pid$target:::entry { 
@a[probemod,probefunc] = count(); 
}
END { trunc(@a,10); }

./lx_proc_func_count.d -p 44622
dtrace: script './lx_proc_func_count.d' matched 30865 probes
^C
CPU     ID                    FUNCTION:NAME
  0      2                             :END 

  firefox                                             realloc                                                       31609
  libmozalloc.so                                      moz_xmalloc                                                   33383
  libmozalloc.so                                      moz_free                                                      36504
  firefox                                             malloc                                                        50687
  firefox                                             free                                                          54604
  libpthread.so.0                                     pthread_self                                                  58444
  libpthread.so.0                                     pthread_getspecific                                           69741
  libpthread.so.0                                     pthread_mutex_unlock                                         204393
  libpthread.so.0                                     pthread_mutex_lock                                           204394
  libpthread.so.0                                     __pthread_mutex_unlock_usercnt                          

lxsockopt.d

#!/usr/sbin/dtrace -s
 
#pragma D option quiet
 
/**
PROTO values can be found here:
https://en.wikipedia.org/wiki/List_of_IP_protocol_numbers
SOCKOPT values can be found here:
https://github.com/joyent/illumos-joyent/blob/master/usr/src/lib/brand/lx/lx_brand/common/socket.c
*/
BEGIN
{
        printf("%6s %20s %5s %s\n", "PID", "NAME", "PROTO", "SOCKOPT");
}
 
lx-syscall::setsockopt:entry
{
        printf("%6d %20s %5d %d\n", pid, execname, arg1, arg2);
}

./lxsockopt.d 
   PID                 NAME PROTO SOCKOPT
 44622              firefox     6 1
 15388                  tor     1 2
 44622              firefox     6 4
 44622              firefox     6 5
 44622              firefox     6 6
 44622              firefox     6 4
 44622              firefox     6 5
 44622              firefox     6 6
 44622              firefox     1 9
 44622              firefox     6 4
 44622              firefox     6 5
 44622              firefox     6 6
 44622              firefox     1 9

track malloc allocations

dtrace -n 'pid8880::malloc:entry { printf ("Firefox is asking for %d bytes", arg0); }'  

  0  74421                     malloc:entry Firefox is asking for 24 bytes
  0  74421                     malloc:entry Firefox is asking for 48 bytes
  0  74421                     malloc:entry Firefox is asking for 16 bytes
  0  74421                     malloc:entry Firefox is asking for 32 bytes
  0  74421                     malloc:entry Firefox is asking for 16 bytes
  0  74421                     malloc:entry Firefox is asking for 8176 bytes

in real-time, find all the code modules which utilize malloc:

  dtrace -l -n 'pid$1::malloc:entry' 1774

     ID   PROVIDER            MODULE                          FUNCTION NAME
   74421    pid1774           firefox                            malloc entry
   74578    pid1774      LMfd`ld.so.1                            malloc entry
   75306    pid1774 LMfd`libmapmalloc.so.1                            malloc entry
   76053    pid1774    LMfd`libc.so.1                            malloc entry
   84541    pid1774         libc.so.6                            malloc entry
   85794    pid1774 ld-linux-x86-64.so.2                            malloc entry

Bisecting

If you found a bug and want to start bisecting to find the exact commit which introduced the problem you have three major cases to consider.

The easy case

You found your bug is part of either Torbutton, Tor Launcher or HTTPS-Everywhere. In this case you check out the respective repository and do the usual bisecting there. To test the various revisions you can take a clean Tor Browser and load the .xpi's into it. Theoretically, this would work in the NoScript case as well but unfortunately there is no public version control system available and thus if you found a bug in NoScript you need to identify the version it showed first up manually and file a ticket.

The medium difficult case

Okay, you ruled out a bug in one of the extensions we ship and determined it got introduced by one of our Tor Browser patches or changes to the bundling/build process (testing whether the bug occurs in a corresponding vanilla Firefox is helpful here). The first thing you are doing now is finding out which Tor Browser version is the one that introduced the bug. Using the ​Tor Browser archive is a good starting point. If you found the culprit and the bug did not get introduced while switching to a new Firefox ESR (the next section deals with the switching case) chances are high that you don't need to bisect at all. Comparing the changelogs between the last version without the bug and the first version with the bug should be enough in this case. But if the changelogs don't ring a bell and you suspect this is a bug introduced by the build process/bundling looking at the changes introduced in the tor-browser-bundle repository between the two Tor Browser releases should reveal the bad commit. If the changelogs don't help and you suspect an issue with one or more of our Tor Browser patches you need to clone the tor-browser repository and do a normal bisect following the Partial Builds strategy outlined above between the last tor-browser patch of the good Tor Browser and the last tor-browser patch that got into the bad Tor Browser.

The tricky case

The patchset effectively did not change and you are only switching to a new ESR. There could be three reasons for the bad Tor Browser then. The first one: rebasing one or more patches went wrong. The second one: some change in the new ESR is causing the trouble. The third one: a combination of the first two. The strategy to deal with this group of cases is to rule out the first one (and thus the third one as well) and then narrow down the possible patches that could be affected by changes in the new ESR. These patches in turn are applied during bisecting the commits in the mozilla-central repository that made it into the bad Tor Browser.

QA and Testing

Some automated tests are run on nightly builds, and new releases. The main page for the results is ​http://test-reports.tbb.torproject.org/reports/.

If you want to run the test suite yourself, read the ​installation instructions, and the ​usage instructions. You can also learn ​how to add a new test.

The different categories of tests we are running are described below.

Tor Browser Test Suite

This test suite contains a series of tests to check a Tor Browser Bundle. It is used to check different things:

• the binaries included in the bundle are correctly linked and compiled
• the tor daemon is working, with bridges, some pluggable transports and with an http proxy
• some mozill and selenium tests

The list of tests is defined in ​TBBTestSuite/BrowserBundleTests.pm. ​Documentation for adding new tests is available.

This test suite is automatically run in the following cases:

• when a new nightly build is available on ​https://people.torproject.org/~linus/builds/. An email of the results is sent to a list of people defined in config/linus-nightly. You can ask me if you want to be added to this list.

• when a new release is tagged on git and available on ​https://people.torproject.org/~user/builds/$version/. The result of the tests is emailed to tor-qa@….

• when a Tor Browser developer created a tbb-qa.yml file to request a build to be test. The result of the tests is emailed to the developer requesting the tests. See the section below for details about requesting tests on custum builds.

VirusTotal uploads

The Windows version of the Tor Browser .exe file is uploaded to virustotal.com to check it with different antivirus. All executable files included in the archive are also uploaded.

The uploads are automatically done in the following cases:

• when a new nightly build is available on ​https://people.torproject.org/~linus/builds/. The results are available on ​http://test-reports.tbb.torproject.org/reports/index-browserbundle_virustotal.html. No emails are sent at the moment (you can ask me if you are interested to receive them).

• when a new release is tagged on git and available on ​https://people.torproject.org/~user/builds/$version/. The results are sent to tor-qa@….

Browser Unit Tests

The Browser Unit Tests are the tests which are included in the Mozilla sources tree (xpcshell and mochitests). The Tor Browser patches can add new tests to be run. Before running those tests, we need to build the sources tree.

We are able to run those tests on a series of commits, and display the differences in the results between each commits and its ancestor.

It is not currently run automatically. In the future, it should be possible to specify a commit or branch to be tested, by editing the tbb-qa.yml file. Until then, you can ask me to edit the config file to test a specific branch or commit.

Rebasing Tests

A prototype for a rebasing tests has been made. The goal is to try to automatically rebase all Tor Browser patches on the master branch of gecko-dev.

It is not yet run automatically.

Requesting testing of a custom build using the tbb-qa.yml file

To request a custom build to be tested, you need an account on people.torproject.org and be listed in the ​config/testrequests file (ask me if you want to be added).

Upload your build to perdulce in directory ~public_html/builds/x.y.z-featureA

Create a file public_html/builds/tbb-qa.yml with permission 744 and a list of build directory names using the YAML syntax:

 ---
 - x.y.z-featureA

You should receive an email on your @torproject.org email address when the tests finished running. Make sure to include a proper sha256sums.txt file and its signature in the respective build directory.

The tbb-qa.yml file can also be used to request other types of tests. Instead of adding a string which is a directory name in your builds directory, you can add a hash table containing the options for your test requests and a 'type' key containing the type of tests you want to run.

For instance the following tbb-qa.yml file can be used to request a test of type 'browserunit' (Tor Browser unit tests) on a specific commit:

---
- type: browserunit
  commit: e1a8bafb44367592b

The following types of tests are available:

Tor Browser Unit Tests (xpcshell and mochitest)

type name: browserunit

Options:

• commit: the commit that you want to build and run tests on. This can be a commit hash, tag or branch.
• esr_branch: using this option means that you want all commits from the Mozilla ESR branch to the selected commit to be tested. Example: esr31.
• git_url: the URL of the git repository containing the selected commit. If unspecified, ​https://git.torproject.org/tor-browser.git is used by default.

FPCentral

FPCentral is a tool which was created by ​Pierre Laperdrix as a Google Summer of Code project. We use this tool to detect changes in the fingerprint of new Tor Browser releases.

An instance of FPCentral is available at the following URL: ​https://fpcentral.tbb.torproject.org/

The git repository containing the sources is at: ​https://gitweb.torproject.org/fpcentral.git/

The tests for the different fingerprint attributes are defined in the ​fingerprint/attributes directory. If you want to add a new test, you will need to create a javascript file containing a function returning an attribute value, and a json file describing this attribute. See the ​README.md file for more details.

When you run the ​fingerprint tests using Tor Browser, it should tell you if all attributes have an acceptable value. The list of acceptable values for each attribute is defined in ​the fingerprint/acceptable/torbrowser70.json file. When adding a new attribute definition, you should also define an acceptable value in this file.

Adding New Default Bridges

1. Once the bridge is running, find its bridge line. For obfs4, the bridge line is in the file <datadir>/pt_state/obfs4_bridgeline.txt. You need to insert the external IP/port, and the fingerprint from the file <datadir>/fingerprint.
2. File a new ticket that contains the bridge line.
   Component: Applications/Tor Browser
   Keywords: tbb-bridges
3. Make a pull request at ​https://github.com/OpenObservatory/ooni-resources that adds the new bridge's IP/port to the file bridge_reachability/tor-bridges-ip-port.csv. (This will cause OONI to start testing the reachability of the new bridge.)

Other Resources