Login Forms

Overview of Login Forms

• Custom login forms are common in web applications, serving as primary authentication mechanisms.

• They consist of HTML forms with input fields for username and password, and a submit button.

Basic Structure of a Login Form

• Example HTML structure:

  <form action="/login" method="post">
    <label for="username">Username:</label>
    <input type="text" id="username" name="username"><br><br>
    <label for="password">Password:</label>
    <input type="password" id="password" name="password"><br><br>
    <input type="submit" value="Submit">
  </form>

• Submits a POST request to the server with the credentials.

Understanding HTTP POST Requests

• POST request includes:

  • URL endpoint (e.g., /login)

  • Content-Type header (e.g., application/x-www-form-urlencoded)

  • Body containing username and password as key-value pairs.

Brute-Forcing with Hydra

• Hydra is a tool for automating login attempts against forms.

• Command structure:

  hydra [options] target http-post-form "path:params:condition_string"

Condition Strings in Hydra

• Failure Condition (F=...): Identifies failed login attempts by checking for specific error messages.

• Success Condition (S=...): Identifies successful logins, often through HTTP status codes or specific content in the response.

Manual Inspection of Login Forms

• Use browser developer tools to inspect the HTML and network requests.

• Key points to note:

  • Method: POST

  • Input field names: username and password

Proxy Interception

• Tools like Burp Suite or OWASP ZAP can intercept and analyze network traffic for more complex forms.

Constructing the Params String for Hydra

• The params string includes:

  • Path to the form

  • Key-value pairs for username and password

  • Failure condition for identifying unsuccessful attempts

Example Params String

• For a form with:

  • Path: /

  • Username field: username

  • Password field: password

  • Failure message: "Invalid credentials"

  The params string would be:

  /:username=^USER^&password=^PASS^:F=Invalid credentials

Running Hydra

• Download necessary wordlists for usernames and passwords.

• Example Hydra command:

  hydra -L top-usernames-shortlist.txt -P 2023-200_most_used_passwords.txt -f SERVER_IP -s SERVER_PORT http-post-form "/:username=^USER^&password=^PASS^:F=Invalid credentials"

Important Notes

• Ensure the params string is accurate for successful attacks.

• After finding valid credentials, log in to retrieve any necessary flags or information.