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Anonymous connection

Need​

Proper configuration to prevent anonymous connections and unauthorized access

Context​

  • Requirement of Ruby 2.0 or higher for running the application
  • Usage of Rails framework for building web applications

Description​

Non compliant code​

# config/environments/production.rb
Rails.application.configure do
  config.action_mailer.smtp_settings = {
    address: 'smtp.example.com',
    port: 587,
    domain: 'example.com',
    user_name: 'anonymous',
    password: 'guest',
    authentication: 'plain',
    enable_starttls_auto: true
  }
end

In the above code, the SMTP settings are configured in such a way that allows anonymous connections. The user_name and password are set to 'anonymous' and 'guest' respectively, which are common default credentials and can be easily guessed or known by potential attackers.

These settings are in the config/environments/production.rb file, which is used for the production environment of a Rails application. This means that these settings will be used when the application is deployed in a production environment.

The authentication option is set to 'plain', which means that the credentials are sent in plain text. If an attacker is able to intercept the network traffic, they can easily read these credentials.

The enable_starttls_auto option is set to true, which means that the application will try to use STARTTLS to upgrade the connection to a secure one before sending the credentials. However, if the server does not support STARTTLS, the credentials will be sent in plain text.

This configuration allows anyone to connect to the SMTP server and send emails on behalf of the application, which can be used for spamming or phishing attacks.

Steps​

  • Remove the hardcoded 'user_name' and 'password' values from the SMTP settings.
  • Store the 'user_name' and 'password' securely, such as in environment variables or a configuration file.
  • Ensure that the stored credentials are not accessible to unauthorized users.
  • Implement proper authentication mechanisms for accessing the SMTP server.
  • Configure the SMTP server to require authentication for sending emails.
  • Regularly review and update the SMTP server configuration to ensure it is secure.

Compliant code​

# config/environments/production.rb
Rails.application.configure do
  config.action_mailer.smtp_settings = {
    address: 'smtp.example.com',
    port: 587,
    domain: 'example.com',
    user_name: ENV['SMTP_USERNAME'],
    password: ENV['SMTP_PASSWORD'],
    authentication: 'plain',
    enable_starttls_auto: true
  }
end

The previous code was vulnerable due to the use of hardcoded credentials (user_name and password) in the SMTP settings. This could allow unauthorized users to make anonymous connections to the server and access protected resources.

The updated code fixes this vulnerability by removing the hardcoded credentials and instead retrieving them from environment variables (ENV['SMTP_USERNAME'] and ENV['SMTP_PASSWORD']). This ensures that the credentials are stored securely and are not accessible to unauthorized users.

In addition to this code change, it is recommended to implement proper authentication mechanisms for accessing the SMTP server and to configure the server to require authentication for sending emails. Regularly reviewing and updating the SMTP server configuration will also help to ensure that it remains secure.

References​

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