1. Buffer Overflows

2. Overflow Overflow can write into existing data or code
Space for 8 chars
Scanf will read a string of any length

3. Overflow
Memory View
Before reading “AndrewScholer”:
After:

4. Reading Safely
scanf("%s", myCString) potentially unsafe
But can specify number of characters to read with %NUMBERs

5. Reading Safely Prevent overflow
fgets(myCString, size, stdin) only reads in size -1 chars
Prevent overflow

6. Stack Attacks Stack contains more than your variables
Information about where function returns to
Where parent function’s stack frame is located

7. Stack Attacks
Imagine c is holding user input…

8. Stack Attacks
Buffer overflow could change where the function returns to, parent’s stack, etc…

9. Heartbleed – Buffer Underflow

10. Heartbleed – Buffer Underflow

11. Heartbleed– Buffer Underflow