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Insecure authentication method - LDAP

Need​

Secure authentication method for LDAP

Context​

  • Usage of Ruby for building dynamic and object-oriented applications
  • Usage of net-ldap for LDAP (Lightweight Directory Access Protocol) integration

Description​

Non compliant code​

require 'net/ldap'

ldap = Net::LDAP.new
ldap.host = your_server_ip
ldap.port = 389
ldap.auth "joe_user", "opensesame"
if ldap.bind
  # authentication succeeded
else
  # authentication failed
end

In the code above, we are using the Net::LDAP library to connect to an LDAP server and authenticate a user. The ldap.auth method is used to specify the username and password for the LDAP server. The ldap.bind method then attempts to bind to the LDAP server using the provided credentials.

The vulnerability lies in the fact that the password is sent in plain text over the network. This is because we are using the insecure LDAP connection (port 389) instead of LDAPS (port 636) which is the secure version of LDAP that uses SSL/TLS.

Moreover, the code does not validate the SSL certificate of the LDAP server. This means that an attacker could potentially set up a rogue LDAP server with a spoofed SSL certificate, trick the client into connecting to it, and capture the client's credentials when they are sent over the network.

The use of SSL/TLS is especially important when the LDAP server is not in the same secure network as the client. In such cases, the credentials could be intercepted by an attacker who has access to the network traffic. This is known as a "man-in-the-middle" attack.

In addition, the code does not handle failed authentication attempts properly. It simply checks whether the bind operation succeeded or not, but does not take any action in case of failure. This could potentially allow an attacker to carry out a brute force attack by trying different combinations of usernames and passwords until they find the correct one.

Steps​

  • Replace the use of LDAP with a more secure authentication method, such as OAuth or JWT.
  • Implement secure communication between the client and server by using TLS/SSL encryption.
  • Avoid sending passwords over the network in plain-text. Instead, use secure hashing algorithms to store and compare password hashes.
  • Implement strong password policies, including password complexity requirements and regular password expiration.
  • Implement multi-factor authentication to add an extra layer of security.
  • Regularly update and patch the LDAP server software to ensure it is up-to-date with the latest security fixes.
  • Perform regular security audits and penetration testing to identify and address any vulnerabilities in the authentication system.

Compliant code​

require 'net/ldap'
require 'devise'
require 'devise/strategies/database_authenticatable'

class User < ActiveRecord::Base
  devise :database_authenticatable, :registerable,
         :recoverable, :rememberable, :validatable
end

class LdapAuthenticatable < Devise::Strategies::DatabaseAuthenticatable
  def authenticate!
    if params[:user]
      user = User.find_by_email(params[:user][:email])
      if user && user.valid_password?(params[:user][:password])
        success!(user)
      else
        fail
      end
    end
  end
end

The above code replaces the insecure LDAP authentication with a more secure method using the Devise gem in a Ruby on Rails application.

Devise is a flexible authentication solution for Rails based on Warden. It provides a full-featured authentication solution which handles all of the most common user authentication tasks.

In the code, we first require the necessary libraries. We then define a User model that includes various Devise modules. The :database_authenticatable module is responsible for hashing and storing the password in the database, and for authenticating users based on a password. The other modules provide additional features such as user registration, password recovery, remembering users between sessions, and user validation.

We then define a custom authentication strategy LdapAuthenticatable that inherits from Devise::Strategies::DatabaseAuthenticatable. In the authenticate! method, we find the user by email and check if the provided password is valid. If the user exists and the password is valid, we call success! with the user, which will sign the user in. If the user does not exist or the password is not valid, we call fail, which will not sign the user in.

This code ensures that passwords are not sent over the network in plain text, but are hashed and stored in the database. It also allows for the implementation of strong password policies and multi-factor authentication, as provided by Devise.

References​

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