Defeating public exploit protections (EMET v5.2 and more)

Raghav PandeResearcher @ FireEye

Disclaimer

The Content, Demonstration, Source Code and Programs presented here is "AS IS" without any warranty or conditions of any kind. Also the views/ideas/knowledge expressed here are solely mine and have nothing to do with the company or the organization in which i am currently working.

However in no circumstances neither me nor SecurityXploded is responsible for any damage or loss caused due to use or misuse of the information presented here.

ContentIntroduction to ExploitationPublic ProtectionsBypassPrecisely Targeted

Why Exploits?Difficult to understandNo proper intelCan own a Researcher and Newbie alikeYou really need to know your stuff

InformationTools used are public and freeEMET (Microsoft)Anti Exploit (Malware Bytes)Hitman Alert (Surfright)

Note: They do a very good job in protecting end users, But nothing is perfect.

Kudos to them!

Introduction to Exploitation

Exploits are crafted pieces of Art which can elevate a Software Bug and grant you one time access to Code Execution.Loopholes or Logic BugsMemory CorruptionInformation Disclosure

Introduction to Exploitation

Details

Pre Exploitation or SetupSprayCorruption of Meta-InformationInfoLeak

ExploitationCorruptionPayload Execution

ROPCodeExecution

Post ExploitationMalware

Possible ProtectionsPre Exploitation or Setup

Spray

ExploitationPayload Execution

ROP detectionCodeExecution detection

Post ExploitationMalware

Public Protections3rd Party support

MemProt Rop

CallerCheckStackPivotSimExecFlowLoadLibrary

Shellcode ProtectionOS & Processor supported

ASLR (Enforced)DEP (Enforced)

ExploitationCVE-2012-1876

IE exploitCorruption of HeapData by OverflowROPShellcode to pop calc.exe

HurdlesRop DetectionShellcode DetectionASLRDEP

ExploitationDefeat DEP by ROPDefeat ASLR by memory leak (provided in sample exploit)

Crux of Exploitation Detection techniquesExploitation Detection Hurdles left

ROPShellcode

Defeating protections from Stack based exploits is for next meetup probably.

ExploitationIn the End

Most of browser based vulnerabilities can be used to cover ASLR by leaking memory to form a valid ROP Chain.

Nearly all exploits come down to 1. Spray2. ROP3. Shellcode

So we will focus on bypassing these only.

Protections StackPivot Check (ROP)

ProtectionsCallerCheck & SimExecFlow Check

(ROP)

Protections Payload Check (Shellcode)

Protections EAF Check (EMET)

DifferentiateEMET MBAE HITMAN Alert

Rop StackPivot Yes Yes YesRop CallerCheck Yes (Full) Yes (Dummed) Yes (Dummed)Rop SimExecFlow

Yes No No

Payload (Shellcode)

No Yes Yes

ControlFlow Integrity(Rop)

No No Yes

EAF Yes No NoImage Highjack No Yes Yes

BypassingStackPivotCallerCheckSimExecFlowEAF/Payload CheckCFI

Bypassing Stackpivot

Bypassing Stackpivot

Bypassing CallerCheck & SimExecFlow

Bypassing CFINull out LBR before ApiCallBorrow functions (hard, unless automated)Be Creative (what we did)

Note: We bypassed a public implementation of CFI, doesn’t mean if its implemented another way it can still be bypassed the same way.

Bypassing CFI

Bypassing Payload Check

Bypassing All protections

In All public exploit mitigation toolkits (Generic)

DEMO time

Bypassing All protections

StackPivot

Targeted BypassingEMET

0x779fe695 + poi(0x779fe695 + 1) => 0x37df11d0

Targeted BypassingEMET

0x37df11d0+0x26 => Preserved Function Prologue

Jumping into Preserved Function Prologue bypasses Hook and forms a valid api call chain

Targeted Bypassing “Other Tools”

Just like EMET we can bypass other public and free toolkits as well.However, That is not the scope of this presentation. =)

Conclusion

An attacker who has studied the system can break anything & everything.

Best method of protecting yourself is using a custom protection, and never letting the adversary know what you use.

Queries?