ShaREing Is Caring

Halvar Flake (halvar.flake@zynamics.com)Sebastian Porst (sebastian.porst@zynamics.com)

He has a problem

Huge DisassembledBinary

Statically linked library he is not aware of

If he only knew ...

EScript.api(Adobe ReaderJavaScript Engine)

libjs (Spider Monkey)Open-Source JavaScript library

He has a problem

PresentGuessingstringsFLIRT signatures

FutureBinCrowd

Demo

AdvantagesDisassembly vs. Source Notice vulnerable code Find other uses

Question: What else usesthis vulnerable function?

Answer: [ List of Programs ]

AcroForm.api

Vulnerable libtiff

Technical Intermezzo A:Finding Functions

We need fast lookup!

Compilers screw with us …

For now we have three ways ...

So how does one store functions?

Random register assignmentReordering instructionsSwitching mnemonics

Small Prime Product

• Positive 64-bit integer number

• Characteristic for a function

• Small prime for each mnemonic

• Multiply

• Two functions are considered equal if they have the same list of mnemonics

– Order of mnemonics is ignored

• Match quality: High

MD-Index

• Structural lookup in a database would be great

• Erm … but a graph is not a number

• We want a hash function for graphs!

MD-Index

80-Bit Hash Value

Result: Fast DB lookup forparticular functions

MD-Index

• Take every edge in the graph

• For every edge, construct 5-tuple:

– # of incoming edges in the source

– # of outgoing edges in the source

– # of incoming edges in the target

– # of outgoing edges in the target

– Topological order of the edge in the graph

• So a graph gives us a set of vectors

MD-Index

• A set of vectors is not exactly a number

• Embed each vector into the reals:

– Map to

– It’s a 5-dimensional vector space over Q

– Each element is also “just” a number

• Use

• Now mix all the results:

MD-Index

80-Bit Hash Value

Result: Fast DB lookup forparticular functions

MD-Index with calls

• Just the flowgraph is too false-positive prone

• Encode the call positions, too

• Result: Hash function for flowgraph with calls at particular locations

3-tiered lookup

• Does the prime product match?

– If yes, high confidence in correct match

• Does the MD-Index with calls match?

– If yes, medium confidence in correct match

• Does the MD-Index without calls match?

– If yes, low confidence in correct match

Problems

• Comparison process is not very robust to changes in flow graphs

– BinDiff can do a lot more

– For most uses sufficient

• Comparison does not work for tiny functions

– Where tiny means less than 8 edges

– Context is not considered

She has a problem

Dozens of previously analyzed rootkits

New suspicious file

If she only knew

She came across that malware author two years ago

He reused his rootkit hiding code and she documented it back then

Demo

AdvantagesRemember the past Import earlier results Simplify the future

Technical Intermezzo B:Calculating scores for files

How to find similar files?

Remember fuzzyness

Here is what we do ...

So we have this database, but ...

One file typically containsseveral different statically linkedand dynamically importedlibraries

Calculating a file score

• Calculate a score that depends on the number of matches weighted by their quality

• The higher the score, the more significant functions are shared by two files

Problems

• We are still working on score calculation

• Desired score depends on goal

– Comment porting, library identification, ...

They have a problem

Complex team with different sub-teams

Information flow restricted by clearance levels

If they only knew ...

BinCrowd manages different access levels in a centralized way

No data transfer from high clearance people to low clearance people

They have another problem

Different members use different tools

Making new information available to other members is difficult

If they only knew ...

BinCrowd makes iteasy to exchange information between different toolsIndividual members can use whatever tools they want

No Demo

(BinNavi Plugin is not yet ready)

AdvantagesCentral database of

knowledgeControlled transfer of

informationSynchronize information

from different tools

Technical Intermezzo C:Use BinCrowd

How do you actually access it?

We host a free community server

Here is what you need ...

So we have this database, but ...

We have a prepopulated databasewhere you can download andupload information.

Software you need

• IDA Pro 5.6

• IDAPython 1.3.2

• A BinCrowd account (free)

• The BinCrowd IDA Pro Plugin

– http://github.com/zynamics

Usage

• Register BinCrowd account

• Download the BinCrowd IDA Plugin

• Load BinCrowd IDA Plugin using ALT-9 in IDA

• Read the readme.txt file to find out what CTRL-1, CTRL-2, CTRL-3, and CTRL-4 do

New IDB

Download prior results

Analyze IDB

Upload new Results Workflow

Best practices

• Name your input files likeprogram.version.compiler.optimization_level.xxx

A fair warning

• Passwords are transmitted in plain-text

• Database will be reset randomly during beta

– All data will be lost, accounts will be kept

• Cross-site request forgeries are a dime a dozen

Credits and Thanks

• Nathan Fain

– For getting the first version of BinCrowd off theground

Credits and Thanks

• Christian Ketterer

– For designing the web interface

• American Greetings

– Thanks in advance for not suing us over our liberal use of care bears when you guys find this presentation

BinCrowd can be used for free!

Give it a try athttp://bincrowd.zynamics.com