Presentation on Stack overflow and how it works with example based on the paper referenced "Smashing the stack for fun and profit"

1. SMASHING THE STACK FOR FUN AND PROFIT
PRESENTED BY
MD. MASUDUR RAHMAN
MSSE 0404
IIT, DU

2. Outline
1. Problem specification of stack overflow
2. Memory structure
3. Stack overflow with examples
4. Code Injection
5. Discussion
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3. Research Problem
How could a stack be smashed?
 What Buffer Overflows are
 How Buffer Overflow exploit works
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4. Process Memory Organization (1/3) 4

5. Process Memory Organization (2/3) 5

6. Process Memory Organization (3/3) 6

7. Structure of a Stack
Manage Control flow
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8. Stack Operation
 Push
 Procedure prolog/enter/link
 Pop
 Procedure epilog/leave/unlink
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9. Stack Operation with Example 9

10. Stack Overflow 10

11. Stack Overflow Example 11

12. Injecting Shell Code
Shell Code in C
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13. Injecting Shell Code 13

14. Injecting Shell Code 14

15. Another Example of Exploit 15

16. NOP Padding 16

17. Problem with Small Buffer
 Can’t hold Shell Code
 Return address points to another instead of shell code
Solution
 Use Environment variable
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18. Vulnerable Code
 No built-in bound checking
 Functions: strcat(); strcpy(); gets(); etc
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19. Discussion
How to prevent stack overflow attack using bound checking?
 Bound Checking when taking input from outside/untrusted source
 Avoid vulnerable functions
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20. 20

21. Question Set
1. Explain stack overflow with proper example.
2. What is NOP? Why attackers use NOP instruction?
3. Explain the problem with small buffer size an attacker faces
to exploit the buffer? Provide a solution for it?
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