Art of Exploit Writing
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This document discusses the art of exploit writing and penetration testing. It provides an overview of buffer overflow techniques, including stack and heap overflows. It explains the process memory organization and stack structure in computers. The document demonstrates buffer overflow exploits and discusses techniques like fuzzing and avoiding bad characters. The goal is to help security researchers and penetration testers work hard toward mastery of exploit writing through experience over time.
Art of Exploit Writing
- 1. ART OF EXPLOIT WRITING Ashfaq Ansari Security Researcher & Penetration Tester Founder Of: HackSys Team http://hacksys.vfreaks.com/ null Meet @Bangalore – 19th Jan 2013
- 2. Buffer Overflow • Writing more data into a buffer than the allocated size. • Two types: – Stack Overflow corrupt the execution stack by writing past the end of an array (aka. smashing the stack/ stack overflow) – Heap Overflow corrupt the heap
- 3. Process Memory Organization • Fixed by the program Text • Read-only Text Data • Initialized & Uninitialized Data • Static variables are stored here Heap Data • Local variables for functions • Return address and local stack pointer Stack Stack
- 4. The Stack - We Must Know Him • Stack is LIFO – Last In First LIFO Out • PUSH & POP operation Buffer 2 • Dynamically allocate local Buffer 1 Used variables used in functions • Pass parameters to functions, etc. SFP RET • Stack Pointer (SP) points a Info to the top of the stack • Contains return address and local stack pointer b c
- 5. x86 General Purpose Register
- 6. Fuzzing
- 7. Overview • Black Box software testing technique, which helps in finding implementation 1 bugs using malformed /semi-malformed data injection in an automated fashion 2 • Lazy mans tool
- 8. The Stack - Overflow Buffer • Overwritten by A’s & AAAA B’s AAAA 1&2 AAAA BBBB SFP • Overwritten by C’s BBBB CCCC DDDD AAAA • Return Overwritten RET by D’s AAAA AAAA
- 9. Bad Characters x00 x0a x0d NULL n r
- 10. DEMO
- 11. Work Hard Toward Mastery Achieve Mastery Exploits Worked On Get Experienced Get Familiar Time Spent