Use of an insecure channel - SMTP - Ruby

Need

Secure communication channel for SMTP

Context

1. Usage of Ruby for building web applications and scripting
2. Usage of net/smtp for sending emails via SMTP protocol

Description

Insecure Code Example

require 'net/smtp'

message = <<MESSAGE_END
From: Private User <user@example.com>
To: A Test User <test@example.com>
Subject: SMTP e-mail test

This is a test e-mail message.
MESSAGE_END

Net::SMTP.start('localhost') do |smtp|
  smtp.send_message message, 'user@example.com', 'test@example.com'
end

In the above code snippet, we are using Ruby's `Net::SMTP` library to send an email. The `Net::SMTP.start` method is used to start a SMTP session. Here, the SMTP session is started without any encryption method. The variable `message` is a string that contains the email's content, including the sender, receiver, subject, and body of the email. This string is then passed to `smtp.send_message` method along with the sender's email and the receiver's email. The vulnerability lies in the fact that the SMTP session is started without any security protocol. This means that the email, including its content, sender's email, and receiver's email, is sent in plain text over the network. If an attacker is able to intercept the network traffic, they can read the email's content and get the sender's and receiver's email addresses. This is a serious security issue as it can lead to information disclosure.

Steps

1. Configure the SMTP service to use SSL/TLS encryption.
2. Update the code to use the secure version of the SMTP library.
3. Ensure that the SMTP server certificate is valid and trusted.
4. Verify that the SMTP server is configured to only accept encrypted connections.
5. Implement proper authentication mechanisms for the SMTP server.
6. Encrypt the sensitive information before sending it over the SMTP channel.

Secure Code Example

require 'net/smtp'

message = <<MESSAGE_END
From: Private User <user@example.com>
To: A Test User <test@example.com>
Subject: SMTP e-mail test

This is a test e-mail message.
MESSAGE_END

Net::SMTP.start('localhost', 
                :port => 587,
                :domain => 'your.host.name',
                :user_name => 'user',
                :password => 'password',
                :authentication => :plain,
                :enable_starttls_auto => true) do |smtp|
  smtp.send_message message, 'user@example.com', 'test@example.com'
end

The updated code now uses the secure version of the SMTP library. The `Net::SMTP.start` method is now configured to use SSL/TLS encryption by setting the `:enable_starttls_auto` option to `true`. This ensures that the connection to the SMTP server is encrypted, protecting the confidentiality of the information being sent. The `:port` option is set to `587`, which is the standard port for secure SMTP connections. The `:domain` option should be set to your host name. The `:user_name` and `:password` options are used for authentication with the SMTP server. These should be replaced with the actual username and password for your SMTP server. The `:authentication` option is set to `:plain`, which means that the username and password are sent in plain text. However, because the connection is encrypted with SSL/TLS, this information is secure. Before sending sensitive information over the SMTP channel, it should be encrypted. This can be done using various encryption algorithms, depending on the specific requirements of your application.

References

Last updated

2023/09/18