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Exploitation possibilities of memory related vulnerabilities

Exploitation possibilities of memory related vulnerabilities. László ERDŐDI, PhD, CEH, SSCP Óbuda University, John von Neumann Faculty of Informatics, Department of Software Technology. ISCD2013, 2-3. September 2013. Memory corruption vulnerabilities since 2002.

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Exploitation possibilities of memory related vulnerabilities

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  1. Exploitation possibilities of memory related vulnerabilities László ERDŐDI, PhD, CEH, SSCP Óbuda University, John von Neumann Faculty of Informatics, Department of Software Technology ISCD2013, 2-3. September 2013

  2. Memory corruption vulnerabilities since 2002 CVE 2013-4974CVE 2013-4206CVE 2013-3348 400 300 200 100 2002 2005 2008 2011

  3. Virtual address space Local variables, method parameters, exception handling data, return adresses Virtual memory Physical memory Dynamically linked shared libraries (libc) Dynamic variables Global variables Compiled code

  4. Main causes and exploitation methods • Lack of input validation within methods (strcpy, gets, etc): stack based overflow (placing harmful code to the stack, ROP, JOP) • Dynamic memory allocation problems (use after free, double free vulnerabilities) heap overflow (function pointer overwrite + heap spray) • Exception handling errors (SEH overwrite) • Others

  5. Classic example of buffer overflow Stack … Method1(a) { d : fixed size array copy a to d } Method2() { Method(a); } … a Code segment d

  6. Avoiding memory execution protection (return to libc)

  7. Avoiding DEP: Return oriented programming (ROP) Shacham, 2007 • Executable code will not be placed on the stack only series of memory addresses and parameters Memory addr 1 Memory addr 2 Parameter 1 Parameter 2 Memory addr 3 Parameter 4 Instruction 1 ret Instruction 3 ret Instruction 2 ret

  8. Jump oriented programming (JOP)Bletsch, Jiang, Freeh 2011 • Attack execution without using stack (not sensible for stack cookie-ra and returnless kernel, it can be used in the case of register machines) Dispatcher gadget Increasing the index pointer Jumping to current address Instruction 1 jmp Instruction 2 jmp Dispatcher table: Memory addr1 Memory addr2 Parameter 1 Parameter 2 Memory addr3 Parameter4 Instruction 3 jmp

  9. Protection against memory corruption SEH chain rewrite + Return address checking? +control flow integrity? ROP JOP Heap overflow (double free, use after free) ? Unhandled exceptions Stack overflow Return to libc

  10. Jump Oriented Programming – dispatcher gadgets in shared libraries (Erdődi, 2013)

  11. Jump Oriented Programming – WinExec example for Win32 X86

  12. Return and Jump Oriented Programing requirements of Turing-completeness Kornau: ARM 2009, Buchanen, Roemer: RISC 2008 • Arbitrary code execution • Loading variables from memory • Writing variables to memory • Branches • Cycles • Method calls

  13. Example: How to carry out conditional statements with return-oriented programming? Method 1: Writing the addresses of the false branch and true branch into the writeable memory, setting of the esp according to indirect addressing. 31 gadgets Method 2: Loading the distance between the address of the false branch and true branch in the memory into a register, adding to esp that value if the condition is true17 gadgets Method 3: Applying gadget which carries out the condition evaluation and jumps at the same time 5 gadgets Instruction 1 ret Instruction 3 ret Instruction 2 ret

  14. Description language for return- and jump- oriented programmingwrite: e.g placing „net user add user passw” to the data segmentgadget1: pop reg1 gadget1: pop reg1 write4:address:valuegadget2: pop reg2 gadget2: pop reg2gadget3: mov [reg1], reg2 gadget3: add reg1, reg2 gadget4: pop reg3 gadget5: pop reg4 gadget6: add reg3, reg4 gadget7: mov [reg1], reg3write4:00400000:netwrite4:00400004:userwrite4:00400008: add write:00400000:net user add user passwdwrite4:0040000c: usewrite4:00400010:r pawrite3:00400014:ssw

  15. Description language for return- and jump- oriented programmingwrite:address:valuecall:address:param1:param2: … paramn e.g call:fopen address:filenamestring:filemodif:condition:address_true:address_false

  16. Description language for return- and jump- oriented programmingsample program:1: write:dataseg_addr1:filename_string write:00400000:try.txt 2: call:fopen_address:dataseg_addr1:filemod call:7c560122:00400000:03: if:address_of_gadget_cmp eax,0:6:4 if:77c7d230:6:44: write:dataseg_addr2:name of executable write:00400010:cmd.exe5:call:winexec_addr:dataseg_addr2 call:7d77501c:04000106:call:exitprocess_addr call:7c210254

  17. Summary • Memory related vulnerabilities are extremly dangerous and developing quickly • The tendency is the legitimate code-reuse for attacking (ROP, JOP) • Several open questions still to solve

  18. ROP mai alkalmazásai • Főként a védelem kikapcsolása a cél • No execute bit átállítása • Új szegmens allokálása írható és végrehajtható jellemzőkkel • Visszevezetés stack overflowra • „egyszerű” utasítássorozatok végrehajtása • Elérhető programok: https://github.com/JonathanSalwan/ROPgadget http://www.vnsecurity.net/2010/08/ropeme-rop-exploit-made-easy/

  19. ROP elleni védekezés • Stack cookie-val nagyon szigorú visszatérési cím felülírási védelem • Ret utasítás nélküli kernelek használata (Chen 2009) • „Control flow” figyelés (Davi, 2009) Bletsch, 2009

  20. A legújabb memória korrupciós sérülékenységek

  21. Memória korrupciós hibák kiaknázása • „Control flow” megtörése - Input adat ellőnérzés hiánya - túlcsordulás • Saját kód futtatása • Metódus visszatérési cím felülírása • Metóduscímek memóriarész felülírása • Kivételkezelő kód címének felülírása • Heap láncolt lista címének felülírása • Memória egy más részének felülírása

  22. Stack security cookie

  23. A security cookie megkerülése MS08-067 – netapi32 vulnerability A/B/C/../../E -> A/E MS07-017 – ANI file parsing vulnerability

  24. Heap túlcsordulás – security cookie

  25. Memória manipuláció elleni védekezések • Kivételkezelő kód szoftveres ellenőrzése (Szoftver DEP) • Memória szegmensek hardveres megjelölése csak írhatónak vagy csak végrehajthatónak (Hardver DEP) • Memória szegmensek random elhelyezése (ASLR) Csak írható Csak végrehajtható Csak írható Csak írható Csak végrehajtható

  26. DEP megkerülése • VirtualAlloc metódushívás • HeapCreate metódushívás • SetProcessDEPPolicy metódushívás • NtSetInformationProcess metódushívás • VirtualProtect metódushívás • WriteProcessMemory metódushívás

  27. Címtér randomizálás (ASLR) megkerülése • Memória cím kiszivárogtatás • Nem teljesen véletlenszerű szegmenselhelyezés

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