Stack Three¶
Soal¶
- Dapat menggunakan gdb atau objdump untuk membantu proses penyelesaian
/*
* phoenix/stack-three, by https://exploit.education
*
* The aim is to change the contents of the changeme variable to 0x0d0a090a
*
* When does a joke become a dad joke?
* When it becomes apparent.
* When it's fully groan up.
*
*/
#include <err.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#define BANNER \
"Welcome to " LEVELNAME ", brought to you by https://exploit.education"
char *gets(char *);
void complete_level() {
printf("Congratulations, you've finished " LEVELNAME " :-) Well done!\n");
exit(0);
}
int main(int argc, char **argv) {
struct {
char buffer[64];
volatile int (*fp)();
} locals;
printf("%s\n", BANNER);
locals.fp = NULL;
gets(locals.buffer);
if (locals.fp) {
printf("calling function pointer @ %p\n", locals.fp);
fflush(stdout);
locals.fp();
} else {
printf("function pointer remains unmodified :~( better luck next time!\n");
}
exit(0);
}
Solusi¶
fflush() is typically used for output stream only. Its purpose is to clear (or flush) the output buffer and move the buffered data to console (in case of stdout) or disk (in case of file output stream). Below is its syntax.
return oriented programming