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Use of an insecure channel - SMTP

Need

Secure transmission of confidential information over SMTP

Context

  • Usage of Scala 2.13 for building scalable and high-performance applications
  • Usage of play-mailer for sending emails in a Play Framework application

Description

Non compliant code

import play.api.libs.mailer._

val email = Email(
"Hello",
"From <[email protected]>",
Seq("To <[email protected]>"),
bodyText = Some("A text message"),
bodyHtml = Some("<html><body><p>An <b>html</b> message</p></body></html>")
)

val mailerClient:MailerClient = ???
mailerClient.send(email)

The above code shows an instance where an email is being sent using the Play framework's Mailer API. The Email object is created with the necessary details such as the sender, recipient, and the body of the email.

The vulnerability lies in the configuration of the MailerClient object. In this case, the MailerClient object is not configured to use SSL, which means that the email is sent over an insecure channel.

The SMTP service is a communication protocol used to send and receive emails. When SSL is not used, the emails are sent in plain text over the network. This means that if an attacker is able to intercept the communication, they can read and even modify the contents of the email without any difficulty.

This is a serious security risk, especially when sensitive information is being sent via email.

To fix this, the MailerClient should be configured to use SSL. This will ensure that all emails are sent over a secure channel and cannot be intercepted or modified by attackers.

Steps

  • Configure the SMTP service to use SSL/TLS encryption.
  • Update the code to use a secure channel for sending emails.
  • Ensure that the SMTP server certificate is valid and trusted.
  • Implement proper authentication mechanisms for the SMTP server.
  • Consider using a dedicated email service provider that offers secure email transmission.
  • Regularly update and patch the SMTP server software to address any security vulnerabilities.

Compliant code

import play.api.libs.mailer._

val email = Email(
"Hello",
"From <[email protected]>",
Seq("To <[email protected]>"),
bodyText = Some("A text message"),
bodyHtml = Some("<html><body><p>An <b>html</b> message</p></body></html>")
)

val mailerClient:MailerClient = new SMTPMailer(SMTPConfiguration("smtp.example.com", 587, true))

mailerClient.send(email)

The above code is a fixed version of the previous insecure SMTP configuration. The SMTP service is now configured to use SSL/TLS encryption, which ensures that the data transmitted over the network is secure and cannot be easily intercepted or tampered with.

The SMTPMailer class is initialized with an SMTPConfiguration object, which takes three parameters: the SMTP server address, the port number, and a boolean value indicating whether to use SSL. In this case, we're using "smtp.example.com" as the server address, 587 as the port number (which is the standard port for secure SMTP connections), and true to enable SSL.

The MailerClient is then used to send the email as before. However, now the email will be sent over a secure channel.

Please note that you should replace "smtp.example.com" with the address of your actual SMTP server. Also, ensure that the SMTP server's SSL certificate is valid and trusted to prevent man-in-the-middle attacks.

In addition to this, it's recommended to implement proper authentication mechanisms for the SMTP server to prevent unauthorized access. You might also want to consider using a dedicated email service provider that offers secure email transmission.

Lastly, remember to regularly update and patch the SMTP server software to address any security vulnerabilities.

References