🚀 go-pugleaf

buzz@toxicavenger.bear.com (Buzz Moschetti) writes:

>Here is a "model" safe setuid program -- thanks to all who sent
>me mail with suggestions.  Features include:
>[...]
>Can anyone add anything else?  Are we secure yet?

Besides closing file descriptors > 2, you will want to make sure that
file descriptors 0,1,2 are open.  Strange things can happen otherwise.
The following code fragment should do:

#include <sys/types.h>
#include <sys/stat.h>
 ...

    struct stat st;
    int     i;

    /* Make sure fd 0,1,2 are open. */

    for (i = 0; i < 3; i++) {
	if (fstat(i, &st) == -1 && open("/", 2) != i) {
	    perror("open /");
	    exit(1);
	}
    }