DVWA practice - brute force cracking

Damn Vulnerable Web App (DVWA), Literal translation Damn vulnerable Web application , It's based on PHP/MySQL Very fragile web application . Its main goal is to help security professionals test their skills and tools in a legitimate environment , help Web Developers have a better understanding of protection Web The application process , And help teachers / Students teach... In a classroom environment / Study Web Application security .

1.DVWA stay kali Installation tutorial on

Be careful not to configure ReCAPTCHA No problem . Others can follow the steps in the following tutorial .

https://www.cnblogs.com/JetpropelledSnake/p/9128613.html

2.DVWA Brute Force Brute force

LOW

Reference link ：https://blog.csdn.net/qq_42357070/article/details/81109775

Add ：

1.GET Method

You can see , stay low Below grade ,form The way to form is GET Method .GET Method will query the string in URL It shows that , Will be cached 、 Save in browser history 、 There is a length limit . adopt GET The characteristics of the method can be seen , When dealing with sensitive data , use GET The method is very unsafe . Generally in form In the form , The methods used are POST Method .

2. Source code parsing

<?php

//isset Function function ： The variable does not exist or the variable exists but the value is NULL, return FALSE; Variable exists and the value is not NULL, return TRUE
// Here to determine whether you clicked login
if( isset( $_GET[ 'Login' ] ) ) {
    
    // Get username
    $user = $_GET[ 'username' ];

    // Get password
    $pass = $_GET[ 'password' ];
    $pass = md5( $pass );

    // Check the database  Here I directly query the database 
    $query  = "SELECT * FROM `users` WHERE user = '$user' AND password = '$pass';";
    //mysqli_query(connection, query, resultmode) Execute a query on a database 
    //die Function outputs a message , And exit the current script 
    $result = mysqli_query($GLOBALS["___mysqli_ston"],  $query ) or die( '<pre>' . ((is_object($GLOBALS["___mysqli_ston"])) ? mysqli_error($GLOBALS["___mysqli_ston"]) : (($___mysqli_res = mysqli_connect_error()) ? $___mysqli_res : false)) . '</pre>' );
	//mysqli_num_rows Returns the number of rows in the result 
    if( $result && mysqli_num_rows( $result ) == 1 ) {
    
        // Get users details
        // Take a row in the result as an associative array ,avatar Generally refers to the user's Avatar 
        $row    = mysqli_fetch_assoc( $result );
        $avatar = $row["avatar"];

        // Login successful
        echo "<p>Welcome to the password protected area {
      $user}</p>";
        echo "<img src=\"{
      $avatar}\" />";
    }
    else {
    
        // Login failed
        echo "<pre><br />Username and/or password incorrect.</pre>";
    }

    ((is_null($___mysqli_res = mysqli_close($GLOBALS["___mysqli_ston"]))) ? false : $___mysqli_res);
}

?> 

3. Four labels

Sniper The sniper Set for each location payload, It is suitable for testing a single request parameter in the vulnerability

​ Number of requests = Number of positions *payload Number

Battering ram Big wooden hammer All positions are set to the same payload, It is suitable for putting the same input into multiple positions

​ Number of requests =payload Number

Pitchfork Fork Different positions use different payload Group , When attacking, all groups are iterated synchronously , It is suitable for inserting different but related inputs in different positions

​ Number of requests = Multiple payload The smallest in each group payload Number

Cluster Bomb cluster bomb Use several different payload Group , Iterate over each group when attacking , It is suitable for inserting different and irrelevant inputs in different positions

​ Number of requests = various payload In the group payload Product of quantity

4.SQL Inject

Reference link ：https://ctf-wiki.github.io/ctf-wiki/web/sqli-zh/

The universal password that can be used this time ：

1.admin'-- perhaps admin'#

Notice the space after the horizontal line

because -- and # It's an interline comment , The condition part of the query statement in the source code becomes where user = 'admin', So we can get a correct query result .

2.admin' or '1' = '1
The condition part becomes where user = 'admin' or '1' = '1' and password = '', because and Part of the statement connection has high priority ,'1' = '1' and password = '' Certainly not , So it is equivalent to executing conditional statements where user = 'admin', You can get a correct query result .

In fact, simplify this into admin' or ' You can also get the correct results .

For things like ' or '1' = '1 Universal statement , The conditional statement becomes where user = '' or '1' = '1' and password = '', Because there is no record with empty user name , So return error .

When constructing omnipotent statements , Also consider whether the query parameter is a string , If it's a string , Then the number of quotation marks should be appropriate .

MEDIUM

stay medium In the version ,$user and $password Variables are subject to the following restrictions ：

$user = ((isset($GLOBALS["___mysqli_ston"]) && is_object($GLOBALS["___mysqli_ston"])) ? mysqli_real_escape_string($GLOBALS["___mysqli_ston"],  $user ) : ((trigger_error("[MySQLConverterToo] Fix the mysql_escape_string() call! This code does not work.", E_USER_ERROR)) ? "" : ""));

mysqli_real_escape_string() Function escape in SQL Special characters in strings used in statements .

Characters that will be escaped include ： NUL （ASCII 0）,\n,\r,\,’," and Control-Z.

So now SQL Statement injection is no longer valid .

HIGH

Compared with before , Joined again ：

![2](C:\Users\15810\Desktop\2.PNG)// Check Anti-CSRF token
checkToken( $_REQUEST[ 'user_token' ], $_SESSION[ 'session_token' ], 'index.php' );

// Remove the backslash , If there are two consecutive backslashes, remove one 
$user = stripslashes( $user ); 

// Login failed
sleep( rand( 0, 3 ) ); 

// Generate Anti-CSRF token
generateSessionToken(); 

Each time the user submits, a random token, Deposit in session in , And set expiration time . When the user submits again , Check token Whether it is consistent or expired .

This makes blind blasting impossible .

Two methods are given in the reference link , One is Python Script , One is still used burp suite, But use Grep-Extract Extracted from the web page token Information , And then as a payload, Use Pitchfork The attack .

Pay attention to the use of burp suite when ,Options Always follow redirection ：

IMPOSSIBLE

Lock for a period of time after three consecutive login failures . Record the number of consecutive login failures in the database , And the time when the last login failed .

 <?php
// To determine whether these three have value 
if( isset( $_POST[ 'Login' ] ) && isset ($_POST['username']) && isset ($_POST['password']) ) {
    
    // Check Anti-CSRF token
    checkToken( $_REQUEST[ 'user_token' ], $_SESSION[ 'session_token' ], 'index.php' );

    // purify username Input 
    $user = $_POST[ 'username' ];
    $user = stripslashes( $user );
    $user = ((isset($GLOBALS["___mysqli_ston"]) && is_object($GLOBALS["___mysqli_ston"])) ? mysqli_real_escape_string($GLOBALS["___mysqli_ston"],  $user ) : ((trigger_error("[MySQLConverterToo] Fix the mysql_escape_string() call! This code does not work.", E_USER_ERROR)) ? "" : ""));

    // Purify password input 
    $pass = $_POST[ 'password' ];
    $pass = stripslashes( $pass );
    $pass = ((isset($GLOBALS["___mysqli_ston"]) && is_object($GLOBALS["___mysqli_ston"])) ? mysqli_real_escape_string($GLOBALS["___mysqli_ston"],  $pass ) : ((trigger_error("[MySQLConverterToo] Fix the mysql_escape_string() call! This code does not work.", E_USER_ERROR)) ? "" : ""));
    $pass = md5( $pass );

    // Default values
    $total_failed_login = 3;
    $lockout_time       = 15;
    $account_locked     = false;

    // Check the database (Check user information)
    $data = $db->prepare( 'SELECT failed_login, last_login FROM users WHERE user = (:user) LIMIT 1;' );
    $data->bindParam( ':user', $user, PDO::PARAM_STR );
    $data->execute();
    $row = $data->fetch();

    // Check to see if the user has been locked out.
    if( ( $data->rowCount() == 1 ) && ( $row[ 'failed_login' ] >= $total_failed_login ) )  {
    
        // User locked out. Note, using this method would allow for user enumeration!
        //echo "<pre><br />This account has been locked due to too many incorrect logins.</pre>";

        // Calculate when the user would be allowed to login again
        $last_login = strtotime( $row[ 'last_login' ] );
        $timeout    = $last_login + ($lockout_time * 60);
        $timenow    = time();

        /* print "The last login was: " . date ("h:i:s", $last_login) . "<br />"; print "The timenow is: " . date ("h:i:s", $timenow) . "<br />"; print "The timeout is: " . date ("h:i:s", $timeout) . "<br />"; */

        // After three consecutive login failures , Check whether enough time has elapsed since the last login failure 
        if( $timenow < $timeout ) {
    
            $account_locked = true;
            // print "The account is locked<br />";
        }
    }

    // Check the database (if username matches the password)
    $data = $db->prepare( 'SELECT * FROM users WHERE user = (:user) AND password = (:password) LIMIT 1;' );
    $data->bindParam( ':user', $user, PDO::PARAM_STR);
    $data->bindParam( ':password', $pass, PDO::PARAM_STR );
    $data->execute();
    $row = $data->fetch();

    // If its a valid login...
    if( ( $data->rowCount() == 1 ) && ( $account_locked == false ) ) {
    
        // Get users details
        $avatar       = $row[ 'avatar' ];
        $failed_login = $row[ 'failed_login' ];
        $last_login   = $row[ 'last_login' ];

        // Login successful
        echo "<p>Welcome to the password protected area <em>{
      $user}</em></p>";
        echo "<img src=\"{
      $avatar}\" />";

        // Had the account been locked out since last login?
        if( $failed_login >= $total_failed_login ) {
    
            echo "<p><em>Warning</em>: Someone might of been brute forcing your account.</p>";
            echo "<p>Number of login attempts: <em>{
      $failed_login}</em>.<br />Last login attempt was at: <em>${last_login}</em>.</p>";
        }

        // Reset bad login count
        $data = $db->prepare( 'UPDATE users SET failed_login = "0" WHERE user = (:user) LIMIT 1;' );
        $data->bindParam( ':user', $user, PDO::PARAM_STR );
        $data->execute();
    } else {
    
        // Login failed
        sleep( rand( 2, 4 ) );

        // Give the user some feedback
        echo "<pre><br />Username and/or password incorrect.<br /><br/>Alternative, the account has been locked because of too many failed logins.<br />If this is the case, <em>please try again in {
      $lockout_time} minutes</em>.</pre>";

        // Update bad login count
        $data = $db->prepare( 'UPDATE users SET failed_login = (failed_login + 1) WHERE user = (:user) LIMIT 1;' );
        $data->bindParam( ':user', $user, PDO::PARAM_STR );
        $data->execute();
    }

    // Set the last login time
    $data = $db->prepare( 'UPDATE users SET last_login = now() WHERE user = (:user) LIMIT 1;' );
    $data->bindParam( ':user', $user, PDO::PARAM_STR );
    $data->execute();
}

// Generate Anti-CSRF token
generateSessionToken();

?>