How to overwrite a function return address on a stack?
The canonical method for exploiting a stack-based buffer overflow is to overwrite the function return address with a pointer to attacker-controlled data (usually on the stack itself).
How many bytes are needed to overwrite a stack buffer?
A twelve-character input thus requires thirteen bytes to store, the input followed by the sentinel zero byte. The zero byte then ends up overwriting a memory location that’s one byte beyond the end of the buffer.)
When does a command line argument overwrite the stack?
C. – “AAAAAAAAAAAAAAAAAAAA\\\\” is the first command line argument. Notice in figure C above, when an argument larger than 11 bytes is supplied on the command line foo () overwrites local stack data, the saved frame pointer, and most importantly, the return address.
What happens when you overfill a buffer on the stack?
Stack buffer overflow is a type of the more general programming malfunction known as buffer overflow (or buffer overrun). Overfilling a buffer on the stack is more likely to derail program execution than overfilling a buffer on the heap because the stack contains the return addresses for all active function calls.
What happens when a stack buffer is overwritten?
As such, if a stack buffer is overwritten during a memory copy operation, the error is noticed before execution returns from the copy function. When this happens, an exception is raised, which is passed back up the exception handler hierarchy until it finally hits the OS’s default exception handler.
How is a security Cookie computed on a function?
On function entry, the allocated space is loaded with a security cookie that is computed once at module load. On function exit, and during frame unwinding on 64-bit operating systems, a helper function is called to make sure that the value of the cookie is still the same.