ShaREing is Caring

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

He has a problem Huge Disassembled Binary Statically linked library he is not aware of

If he only knew ... EScript.api (Adobe Reader JavaScript Engine) libjs (Spider Monkey) Open-Source JavaScript library

He has a problem Present Guessing strings FLIRT signatures Future BinCrowd

Advantages Disassembly vs. Source Notice vulnerable code Find other uses Question: What else uses AcroForm.api this vulnerable function? Vulnerable libtiff Answer: [ List of Programs ]

Technical Intermezzo A: Finding Functions

So how does one store functions? We need fast lookup! Compilers screw with us … Random register assignment Reordering instructions Switching mnemonics For now we have three ways ...

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 for particular 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 for particular 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

Advantages Remember the past Import earlier results Simplify the future

Technical Intermezzo B: Calculating scores for files

So we have this database, but ... How to find similar files? Remember fuzzyness One file typically contains several different statically linked and dynamically imported libraries Here is what we do ...

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 it easy to exchange information between different tools Individual members can use whatever tools they want

No Demo (BinNavi Plugin is not yet ready)

Advantages Central database of Controlled transfer of Synchronize information knowledge information from different tools

Technical Intermezzo C: Use BinCrowd

So we have this database, but ... How do you actually access it? We host a free community server We have a prepopulated database where you can download and upload information. Here is what you need ...

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 Upload new Download Results Workflow prior results Analyze IDB

Best practices • Name your input files like program.version.compiler.optimization_level.x xx

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 the ground

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 at http://bincrowd.zynamics.com

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ShaREing is Caring

by zynamics GmbH on Apr 26, 2010

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ShaREing is Caring — Presentation Transcript