Explore Hydra Module-Specific Options

Introduction

In this lab, we will explore the HTTP POST options available in Hydra, focusing on how to effectively target services that use HTTP POST for authentication. We'll learn how to specify usernames and passwords, as well as the URL to which the POST request should be sent.

This lab will guide you through reviewing HTTP POST options with the -U flag, setting up an HTTP POST form, running Hydra with specific -m options, and validating the POST attack. You'll learn how to use Hydra to brute-force login credentials when targeting services that use HTTP POST for authentication.

Skills Graph

Review HTTP POST Options with -U

In this step, we will explore the HTTP POST options available in Hydra using the -U flag. The -U flag is used to specify a username when performing a POST request. This is particularly useful when the target service requires a username to be sent as part of the POST data.

Before we dive into the practical example, let's understand the basic concept of HTTP POST requests. HTTP POST is a method used to send data to a server to create or update a resource. Unlike GET requests, POST requests carry the data in the request body, making them suitable for sending larger amounts of data, such as form submissions.

Hydra is a powerful tool for brute-forcing login credentials. When targeting services that use HTTP POST for authentication, we need to provide Hydra with the necessary information, including the username and password fields, as well as the URL to which the POST request should be sent.

The -U option in Hydra allows you to specify a single username to be used for all login attempts. This is useful when you already know the username and only need to brute-force the password.

Let's see how to use the -U option with a simple example. Suppose we want to attack a web application that uses HTTP POST for login, and we know the username is testuser. We can use the following Hydra command:

hydra -l testuser -P ~/project/password.txt "/login.php:username=^USER^&password=^PASS^:F=Invalid username or password" < target_ip > http-post-form

In this command:

• hydra: The command to invoke Hydra.
• -l testuser: Specifies the username as testuser. Note that we are using -l instead of -U here. -l specifies a single username, while -U specifies a file containing a list of usernames.
• -P ~/project/password.txt: Specifies the path to the password list file. Make sure you have a password.txt file in your ~/project directory. You can create one using nano:

nano ~/project/password.txt

Add some common passwords to the file, one password per line, for example:

password
123456
qwerty

Save the file and exit nano.

• <target_ip>: Replace this with the IP address of the target server. For this lab, you'll need to replace this with the actual IP address of the server you are attacking. We will assume the target IP is 127.0.0.1 for demonstration purposes.
• http-post-form: Specifies that we are using the HTTP POST form module.
• "/login.php:username=^USER^&password=^PASS^:F=Invalid username or password": This is the most important part. It tells Hydra how to construct the POST request.
  • /login.php: The URL to which the POST request should be sent.
  • username=^USER^&password=^PASS^: The POST data. ^USER^ and ^PASS^ are placeholders that Hydra will replace with the username and password, respectively.
  • F=Invalid username or password: This tells Hydra what string to look for in the response to determine if the login attempt failed. If Hydra finds this string, it knows that the login attempt was unsuccessful.

Now, let's run the command with the example IP address:

hydra -l testuser -P ~/project/password.txt 127.0.0.1 http-post-form "/login.php:username=^USER^&password=^PASS^:F=Invalid username or password"

This command will attempt to brute-force the password for the testuser account using the passwords in the password.txt file. Hydra will send HTTP POST requests to the /login.php URL with the username and password fields set accordingly. If Hydra finds a valid password, it will display it on the screen.

This example demonstrates the basic usage of the -l option with the http-post-form module. In the following steps, we will explore more advanced options and techniques for attacking HTTP POST forms with Hydra.

Set Up HTTP POST Form

In this step, we will set up a simple HTTP POST form that we can use as a target for our Hydra attacks. We'll create a basic HTML form and a PHP script to handle the form submission. This will allow us to understand how Hydra interacts with HTTP POST forms and how to craft the correct Hydra command.

First, let's create the HTML form. We'll create a file named login.html in the ~/project directory.

nano ~/project/login.html

Now, paste the following HTML code into the file:

<!DOCTYPE html>
<html>
  <head>
    <title>Login Form</title>
  </head>
  <body>
    <h1>Login</h1>
    <form method="post" action="login.php">
      <label for="username">Username:</label><br />
      <input type="text" id="username" name="username" /><br /><br />
      <label for="password">Password:</label><br />
      <input type="password" id="password" name="password" /><br /><br />
      <input type="submit" value="Login" />
    </form>
  </body>
</html>

This HTML code creates a simple login form with two input fields: username and password. The form uses the POST method and submits the data to login.php.

Save the file and exit nano.

Next, we need to create the login.php script to handle the form submission. Create a file named login.php in the ~/project directory:

nano ~/project/login.php

Now, paste the following PHP code into the file:

<?php
$username = $_POST['username'];
$password = $_POST['password'];

if ($username == 'testuser' && $password == 'password') {
  echo "Login successful!";
} else {
  echo "Invalid username or password";
}
?>

This PHP script retrieves the username and password from the POST data and checks if they match the hardcoded values testuser and password. If the credentials are correct, it prints "Login successful!"; otherwise, it prints "Invalid username or password".

Save the file and exit nano.

Now, you have a basic HTTP POST form set up. To test it, you would typically need a web server (like Apache or Nginx) running and serving these files. Since we are focusing on Hydra and the LabEx environment doesn't include a pre-configured web server, we will proceed assuming you have a way to access these files through a web server. For example, if you were running a web server locally and serving the ~/project directory, you could access the form by navigating to http://localhost/login.html in your web browser.

In the next step, we will use Hydra to attack this form. We will use the -m option to specify the POST data and the -F option to identify the failure message.

Run with -m Options

In this step, we will use the -m option in Hydra to specify the HTTP POST data directly. This is an alternative to using the http-post-form module, and it gives us more control over the structure of the POST request.

The -m option allows you to define the entire POST request body. You need to specify the username and password placeholders (^USER^ and ^PASS^) within the POST data.

Let's use the login.php form we created in the previous step as our target. We will use the -m option to specify the POST data as username=^USER^&password=^PASS^. We will also use the -l option to specify a single username (testuser) and the -P option to specify the password list file (~/project/password.txt).

Here's the Hydra command we will use:

hydra -l testuser -P ~/project/password.txt "/login.php:username=^USER^&password=^PASS^:F=Invalid username or password" < target_ip > http-post

In this command:

• hydra: The command to invoke Hydra.
• -l testuser: Specifies the username as testuser.
• -P ~/project/password.txt: Specifies the path to the password list file.
• <target_ip>: Replace this with the IP address of the target server. As before, we'll assume the target IP is 127.0.0.1 for demonstration purposes.
• http-post: Specifies that we are using the HTTP POST module.
• "/login.php:username=^USER^&password=^PASS^:F=Invalid username or password": This specifies the URL, POST data, and failure string.
  • /login.php: The URL to which the POST request should be sent.
  • username=^USER^&password=^PASS^: The POST data. ^USER^ and ^PASS^ are placeholders that Hydra will replace with the username and password, respectively.
  • F=Invalid username or password: This tells Hydra what string to look for in the response to determine if the login attempt failed.

Now, let's run the command with the example IP address:

hydra -l testuser -P ~/project/password.txt 127.0.0.1 http-post "/login.php:username=^USER^&password=^PASS^:F=Invalid username or password"

This command will attempt to brute-force the password for the testuser account using the passwords in the password.txt file. Hydra will send HTTP POST requests to the /login.php URL with the specified POST data. If Hydra finds a valid password, it will display it on the screen.

The key difference between this command and the one in Step 1 is the use of http-post instead of http-post-form. The http-post module requires you to specify the entire POST data string using the -m option (which is embedded in the URL string here), while http-post-form automatically constructs the POST data based on the form fields.

This example demonstrates how to use the -m option to specify the POST data directly. In the next step, we will validate the POST attack and see how to capture the successful login.

Validate POST Attack

In this step, we will validate the POST attack by ensuring that Hydra successfully identifies the correct password. To do this effectively, we'll modify our password.txt file to include the correct password, ensuring Hydra finds it. We'll also analyze the output to confirm the successful login.

First, let's modify the ~/project/password.txt file to include the correct password, which is password according to our login.php script.

nano ~/project/password.txt

Add the password password to the file. It's good practice to put it near the beginning for faster results. The file should now look something like this:

password
123456
qwerty

Save the file and exit nano.

Now, run the Hydra command again, using the same command as in the previous step:

hydra -l testuser -P ~/project/password.txt 127.0.0.1 http-post "/login.php:username=^USER^&password=^PASS^:F=Invalid username or password"

This time, Hydra should quickly find the correct password and display it in the output. The output should look similar to this:

Hydra v9.6 (c) 2024 by van Hauser/THC & David Maciejak - Please use caution!

Hydra starting at 2024-10-27 14:30:00
[DATA] 1 task, 1 server, 13 login tries (l:1/p:13), ~1 try per task
[DATA] attacking service http-post on 127.0.0.1
[2;32][http-post] host: 127.0.0.1   login: testuser   password: password
Hydra is finishing at 2024-10-27 14:30:05

The line [http-post] host: 127.0.0.1 login: testuser password: password indicates that Hydra successfully found the password password for the username testuser.

If you don't see this output, double-check the following:

• Make sure the password.txt file contains the correct password (password).
• Make sure the login.php script is correctly configured to check for the username testuser and password password.
• Make sure the Hydra command is correctly formatted, especially the URL, POST data, and failure string.

By successfully running the Hydra command and observing the output, you have validated the POST attack and confirmed that Hydra can successfully brute-force login credentials on an HTTP POST form.

This completes the lab on attacking HTTP POST forms with Hydra. You have learned how to set up a simple HTTP POST form, how to use the -m option to specify the POST data, and how to validate the attack by ensuring that Hydra finds the correct password.

Summary

In this lab, we explored the HTTP POST options in Hydra, focusing on how to brute-force login credentials when a web application uses HTTP POST for authentication. We learned about the -l option to specify a single username for all login attempts, and how to provide Hydra with the necessary information, including the username and password fields, as well as the URL to which the POST request should be sent.

We also reviewed the basic concept of HTTP POST requests, understanding that POST requests carry data in the request body, making them suitable for sending larger amounts of data, such as form submissions. The lab emphasized the importance of providing the correct parameters to Hydra for successful brute-forcing, including the target URL, username field, password field, and a failure message to identify unsuccessful login attempts.