1 col@prowl:~$ ls -al

 2 total 36

 3 drwxr-x---   5 root    col     4096 Oct 23  2016 .

 4 drwxr-xr-x 114 root    root    4096 May 19 15:59 ..

 5 d---------   2 root    root    4096 Jun 12  2014 .bash_history

 6 -r-sr-x---   1 col_pwn col     7341 Jun 11  2014 col

 7 -rw-r--r--   1 root    root     555 Jun 12  2014 col.c

 8 -r--r-----   1 col_pwn col_pwn   52 Jun 11  2014 flag

 9 dr-xr-xr-x   2 root    root    4096 Aug 20  2014 .irssi

10 drwxr-xr-x   2 root    root    4096 Oct 23  2016 .pwntools-cache

11 col@prowl:~$ cat col.c

12 #include <stdio.h>

13 #include <string.h>

14 unsigned long hashcode = 0x21DD09EC;

15 unsigned long check_password(const char* p){

16         int* ip = (int*)p;

17         int i;

18         int res=0;

19         for(i=0; i<5; i++){

20                 res += ip[i];

21         }

22         return res;

23 }

24

25 int main(int argc, char* argv[]){

26         if(argc<2){

27                 printf("usage : %s [passcode]\n", argv[0]);

28                 return 0;

29         }

30         if(strlen(argv[1]) != 20){

31                 printf("passcode length should be 20 bytes\n");

32                 return 0;

33         }

34

35         if(hashcode == check_password( argv[1] )){

36                 system("/bin/cat flag");

37                 return 0;

38         }

39         else

40                 printf("wrong passcode.\n");

41         return 0;

42 }