代码如下
#include <stdio.h>
int main(){
unsigned int random;
random = rand(); // random value!
unsigned int key=0;
scanf("%d", &key);
if( (key ^ random) == 0xdeadbeef ){
printf("Good!\n");
system("/bin/cat flag");
return 0;
}
printf("Wrong, maybe you should try 2^32 cases.\n");
return 0;
}rand()并没有真的随机化，manpage里说
If no seed value is provided, the rand() function is automatically seeded with a value of 1.
是用gdb得到这个所谓的随机值，是0x6b8b4567，所以我们输入0x6b8b4567^0xdeadbeef=3039230856就行。