Buffer Overflow Protections

Canaries

Buffer overflow protection

• Insert a random “canary” value between the return address and the rest of the stack frame.
• Check if it’s intact before returning. Abort if changed.
• Any stack-smash attack will have to overwrite the canary to get to the return address.
• Use a different random value each time the program is executed.

Address Randomization

Address Space Layout Randomization

• Put stack at different random location each time program is executed
• Put heap at different random location as well
• Good: defeat attempts to address known locations
• Bad: make debug harder