Check local file permissions

Challenge

Implement int is_secret_file_safe(const char *path) returning:

• 1 if the file at path is mode 600 (read+write owner only),
• 0 if it exists but has any other permission bits set,
• -1 if it can't be stat'd.

Detects accidentally world-readable secret files — a common cause of credential leaks in misconfigured deployments.

Starter code

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

int is_secret_file_safe(const char *path) {
    /* TODO */
    return -1;
}