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Re: [tor-bugs] #5837 [Tor bundles/installation]: Use IDA Pro and/or BinDiff to inspect releases
#5837: Use IDA Pro and/or BinDiff to inspect releases
--------------------------------------+-------------------------------------
Reporter: mikeperry | Owner: cypherpunks
Type: project | Status: new
Priority: major | Milestone:
Component: Tor bundles/installation | Version:
Keywords: volunteer | Parent: #5292
Points: | Actualpoints:
--------------------------------------+-------------------------------------
Old description:
> We have some concerning issues with our build processes. It's hard to
> really know for sure that the build machines are secure and not tampered
> with. See for example #5689. The most likely situation there is that AV
> signature engines fucking suck, and were false positives. However, the
> real fix is not simply scanning the build machines with more shitty AV
> software (although it was a fine, rational first step -- I'm not hating
> on you, Erinn). The real fix is unfortunately much harder: We need to
> ensure that the same source produces the same binaries everywhere: #3688.
>
> Other than build reproduction, it's nearly fucking impossible to know
> that the binaries you get actually come from the source you wrote and
> audited. A handful of Open Source projects have figured it out (see
> comments in #3688), but it's actually pretty darn hard on Windows, if not
> impossible.
>
> As a stop-gap solution, it's occurred to me that we might be able to
> crowdsource hobbyists and people looking to learn reversing (or if we're
> really lucky, some people who already have these skills) to both help
> verify previous builds, and give us the input we need to proceed on
> #3688.
>
> If you have access to IDA Pro
> ([http://blog.zynamics.com/2011/12/05/bindiff-4-0-available-today/
> BinDiff] will help, but is an extra $200 extension to IDA Pro and is not
> required), you can participate as follows:
>
> 1. Download a signed TBB release from
> https://www.torproject.org/dist/torbrowser/.
>
> 2. Compile your own TBB bundle. This is somewhat tricky. Sebastian has
> instructions for Mac OS in
> https://gitweb.torproject.org/torbrowser.git/tree/master:/docs/buildmachine_setups.
> Windows and Linux instructions should arrive there soon.
>
> If you succeed in producing an independent build, it will be useful to
> post a link to it here for others to begin analyzing. However, you'll
> want to use a VM when inspecting random anonymous people's builds: IDA
> Pro is of course not immune to exploits against itself.
>
> 3. BinDiff the resulting packaging exe as well as the exes contained
> therein.
>
> If you lack BinDiff, you should consider focusing your efforts on MacOS
> and Linux packages, which should produce substantially more similar
> builds than Windows, especially if you build the Linux TBB on Debian
> Lenny and the Mac one on MacOS 10.7 with Xcode 4 (which are our build
> machine setups). Start with using the 'cmp' (and/or hexdump and diff)
> UNIX commands to find the differing sections of the binaries, and then
> use IDA Pro to inspect those sections. More advanced tools to find
> minimal binary edit differences may also be useful if the differences the
> basic tools find are large. http://jojodiff.sourceforge.net/ is an
> example of one such tool, but there probably are others.
>
> You should be able to use IDA Pro for any platform to analyze binaries
> for any other platform. You do not need to buy the MacOS copy to analyze
> MacOS binaries.
>
> 4. Use normal UNIX diff on the non-exe components (for example, conf
> files, shell scripts, contents of Firefox jars and addon sources).
>
> 5. Write up the significant differences.
>
> We need to make the above a semi-regular part of our development process
> to periodically verify our build integrity.
>
> Writing up the differences you find will also be useful for us to help us
> work towards #3688, especially for Mac and Linux builds (which are likely
> pretty darn close.. It's probably only some timestamps and symbol names
> that differ if you use the same platform and compiler).
>
> If you want to be extra-helpful, you can write up a detailed howto
> (and/or just paste the ones you find that already exist) on the process
> itself to make it even easier for others to learn and participate.
>
> We'll need to do this often.. Perhaps not for every release, but at least
> randomly on some builds every once and a while. Also, BinDiffing archived
> signed TBB copies from https://archive.torproject.org/tor-package-
> archive/torbrowser/ will be useful, too, so no need to wait for future
> releases. You can start today. The source tarballs are in that directory
> as well, with -src.tar.gz instead of a language and arch. However, to get
> the actual git sources for an old release:
>
> {{{
> git clone git://git.torproject.org/torbrowser.git
> cd torbrowser
> git tag -l
> git checkout torbrowser-2.2.35-9.1
> }}}
>
> Git will tell you that you can't commit anything that way, but that
> shouldn't matter to you.
>
> Note that this whole process is a fantastic exercise in learning basic
> reverse engineering skills. Diffing vendor patches and malware updates is
> a common practice in the field. It's a useful skill to learn, if you have
> the time.
>
> Good luck!
New description:
We have some concerning issues with our build processes. It's hard to
really know for sure that the build machines are secure and not tampered
with. See for example #5689. The most likely situation there is that AV
signature engines fucking suck, and were false positives. However, the
real fix is not simply scanning the build machines with more shitty AV
software (although it was a fine, rational first step -- I'm not hating on
you, Erinn). The real fix is unfortunately much harder: We need to ensure
that the same source produces the same binaries everywhere: #3688.
Other than build reproduction, it's nearly fucking impossible to know that
the binaries you get actually come from the source you wrote and audited.
A handful of Open Source projects have figured it out (see comments in
#3688), but it's actually pretty darn hard on Windows, if not impossible.
As a stop-gap solution, it's occurred to me that we might be able to
crowdsource hobbyists and people looking to learn reversing (or if we're
really lucky, some people who already have these skills) to both help
verify previous builds, and give us the input we need to proceed on #3688.
If you have access to IDA Pro
([http://blog.zynamics.com/2011/12/05/bindiff-4-0-available-today/
BinDiff] will help, but is an extra $200 extension to IDA Pro and is not
required), you can participate as follows:
1. Download a signed TBB release from
https://www.torproject.org/dist/torbrowser/.
2. Compile your own TBB bundle. This is somewhat tricky. Sebastian has
instructions for Mac OS in
https://gitweb.torproject.org/torbrowser.git/tree/master:/docs/buildmachine_setups.
Windows and Linux instructions should arrive there soon.
3. Analyze/BinDiff the resulting packaging exe as well as the exes
contained therein.
If you lack BinDiff, you should consider focusing your efforts on MacOS
and Linux packages, which should produce substantially more similar builds
than Windows, especially if you build the Linux TBB on Debian Lenny and
the Mac one on MacOS 10.7 with Xcode 4 (which are our build machine
setups). Start with using the 'cmp' (and/or hexdump and diff) UNIX
commands to find the differing sections of the binaries, and then use IDA
Pro to inspect those sections (quickest way: Just use the search tool for
a long hex string surrounding the difference).
More advanced tools to find minimal binary edit differences may also be
useful if the differences the basic tools find are large.
http://jojodiff.sourceforge.net/ is an example of one such tool, but there
probably are others.
Be sure to verify the difference that IDA and/or BinDiff decodes is the
same as a simple diff tool finds (cmp or jojodiff). The simple diff tool
is less likely to be fooled than IDA.
You should be able to use IDA Pro for any platform to analyze binaries for
any other platform. You do not need to buy the MacOS copy to analyze MacOS
binaries.
4. Use normal UNIX diff on the non-exe components (for example, conf
files, shell scripts, contents of Firefox jars and addon sources).
5. Write up the significant differences.
We need to make the above a semi-regular part of our development process
to periodically verify our build integrity.
Writing up the differences you find will also be useful for us to help us
work towards #3688, especially for Mac and Linux builds (which are likely
pretty darn close.. It's probably only some timestamps and symbol names
that differ if you use the same platform and compiler).
If you want to be extra-helpful, you can write up a detailed howto (and/or
just paste the ones you find that already exist) on the process itself to
make it even easier for others to learn and participate.
We'll need to do this often.. Perhaps not for every release, but at least
randomly on some builds every once and a while. Also, BinDiffing archived
signed TBB copies from https://archive.torproject.org/tor-package-
archive/torbrowser/ will be useful, too, so no need to wait for future
releases. You can start today. The source tarballs are in that directory
as well, with -src.tar.gz instead of a language and arch. However, to get
the actual git sources for an old release:
{{{
git clone git://git.torproject.org/torbrowser.git
cd torbrowser
git tag -l
git checkout torbrowser-2.2.35-9.1
}}}
Git will tell you that you can't commit anything that way, but that
shouldn't matter to you.
Note that this whole process is a fantastic exercise in learning basic
reverse engineering skills. Diffing vendor patches and malware updates is
a common practice in the field. It's a useful skill to learn, if you have
the time.
Good luck!
--
Comment(by mikeperry):
Changes to description: Give a few more hints to illuminate the diffing
process. We may not actually want to rely fully on what BinDiff and IDA
say.
--
Ticket URL: <https://trac.torproject.org/projects/tor/ticket/5837#comment:9>
Tor Bug Tracker & Wiki <https://trac.torproject.org/>
The Tor Project: anonymity online
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