Buffer Overflow Attacks

• Computer Systems

Buffer Overflow

• In C, many strings-related functions do not check the bound.
• It may start to overwrite a fixed-sized array.
• A savvy users may put a long input array, overwriting the return address with desired value.

Preventing Such Exploits

• Use better functions.
  • scanf → sscanf
  • gets → getline
  • strcpy → strncpy
  • strcat → strncat
• Use Canary Values
  • Compiler inserts random unique values--canary values--before return address
  • If the canary values are modified, crash.
• Address Space Layout Randomization (ASLR)