How to Handle the Amazon EC2 SES SMTP Credentials Leak

Securing Your SES SMTP Credentials on EC2

It is imperative that you safeguard your SES SMTP credentials, particularly if you are sending emails with PHP and cPanel webmail (Exim). These credentials have been compromised on several occasions recently, leading to the sending of unsanctioned spam emails from your primary domain email address.

This post addresses possible security holes and provides doable solutions to safeguard your SES SMTP credentials on PHP Amazon EC2 host running Rocky 9. You may prevent future hacks into your email system by being aware of the risks and taking the recommended security precautions.

Command	Description
openssl_encrypt()	Utilizes the chosen cipher and key to encrypt data. used to safely store SMTP login information.
openssl_decrypt()	Restores previously encrypted data by decrypting it. used to get the original SMTP login information.
file_get_contents()	Converts every word in the file to a string. utilized to import the encryption key from a safe place.
file_put_contents()	Adds information to a file. utilized to safely store encrypted SMTP credentials.
PHPMailer\PHPMailer\PHPMailer	A PHP email sender class that is derived from the PHPMailer package.
sed -i "s/command"	Stream editor command to make in-place file modifications. used to update the decrypted credentials in the Exim settings.
systemctl restart	Relaunches a system application. used to update the configuration of the Exim service and restart it.

Knowing How to Address the SES SMTP Credentials Leak

The included scripts are made to protect and handle SES SMTP credentials in order to stop misuse and illegal access. The first PHP script shows how to use the function to encrypt SMTP credentials, ensuring that private data is kept safe. To prevent unwanted access, the credentials are encrypted using a secure key and kept in a file. To read the encryption key and store the encrypted credentials, utilize the and functions, respectively. By using this technique, it is made sure that even if the saved file is accessed, the credentials cannot be read without the encryption key.

The purpose of the second PHP script is to decode the encrypted SMTP credentials and use them to send emails. The credentials are decrypted using the function and then made available for use in the email sending procedure. To send emails using the decrypted SMTP credentials, the software integrates with PHPMailer. It is easier to set up and send secure emails when PHPMailer is used. The shell script is also made to update the Exim configuration with the credentials that have been decrypted. To ensure that the new configuration is applied right away, it utilizes the command to make changes to the Exim configuration file and the command to restart the Exim service.

//php
// Load encryption key from a secure location
$encryption_key = file_get_contents('/path/to/secure/key');
// SMTP credentials
$smtp_user = 'your_smtp_user';
$smtp_pass = 'your_smtp_password';
// Encrypt credentials
$encrypted_user = openssl_encrypt($smtp_user, 'aes-256-cbc', $encryption_key, 0, $iv);
$encrypted_pass = openssl_encrypt($smtp_pass, 'aes-256-cbc', $encryption_key, 0, $iv);
// Store encrypted credentials in a file
file_put_contents('/path/to/secure/credentials', $encrypted_user . "\n" . $encrypted_pass);
//

//php
// Load encryption key and credentials from secure location
$encryption_key = file_get_contents('/path/to/secure/key');
$credentials = file('/path/to/secure/credentials');
$encrypted_user = trim($credentials[0]);
$encrypted_pass = trim($credentials[1]);
// Decrypt credentials
$smtp_user = openssl_decrypt($encrypted_user, 'aes-256-cbc', $encryption_key, 0, $iv);
$smtp_pass = openssl_decrypt($encrypted_pass, 'aes-256-cbc', $encryption_key, 0, $iv);
// Use decrypted credentials to send email
// Example using PHPMailer
use PHPMailer\PHPMailer\PHPMailer;
$mail = new PHPMailer();
$mail->isSMTP();
$mail->Host = 'email-smtp.us-east-1.amazonaws.com';
$mail->SMTPAuth = true;
$mail->Username = $smtp_user;
$mail->Password = $smtp_pass;
$mail->SMTPSecure = 'tls';
$mail->Port = 587;
// ... additional email setup ...
//

#!/bin/bash
# Load encryption key and credentials from secure location
encryption_key=$(cat /path/to/secure/key)
credentials=$(cat /path/to/secure/credentials)
encrypted_user=$(echo "$credentials" | head -n 1)
encrypted_pass=$(echo "$credentials" | tail -n 1)
# Decrypt credentials
smtp_user=$(echo "$encrypted_user" | openssl enc -aes-256-cbc -d -a -A -k "$encryption_key")
smtp_pass=$(echo "$encrypted_pass" | openssl enc -aes-256-cbc -d -a -A -k "$encryption_key")
# Update Exim configuration
sed -i "s/smtp_user = .*/smtp_user = $smtp_user/" /etc/exim/exim.conf
sed -i "s/smtp_pass = .*/smtp_pass = $smtp_pass/" /etc/exim/exim.conf
# Restart Exim service
systemctl restart exim

Improving SES-Based Email Security on EC2

Developing a thorough security plan for your email system is crucial, in addition to encrypting and safely storing SMTP credentials. Using Amazon EC2 security groups to limit access to your SMTP ports is one practical solution. Unauthorized access can be decreased by restricting access to particular IP addresses or ranges. Moreover, you can lessen the impact of any leaks by changing your SES SMTP credentials on a regular basis.

Enabling logging and monitoring on your SES account and EC2 instance is another essential step. By putting AWS CloudTrail and Amazon CloudWatch into practice, you may monitor and investigate any questionable activity pertaining to your email system. By taking a proactive stance, you can keep your email communications secure and intact by quickly recognizing and responding to security events.

1. How can I limit EC2 users' ability to access my SMTP ports?
2. To restrict access to your SMTP ports to particular IP addresses or ranges, use Amazon EC2 security groups.
3. Why would you want to encrypt your SMTP credentials?
4. By encrypting SMTP credentials, you can be sure that they are difficult to read or use even in the event of illegal access.
5. How often should my SES SMTP credentials be changed?
6. Rotating your SES SMTP credentials is advised every ninety-days, or sooner if you think there may have been a leak.
7. What resources can I utilize to keep an eye out for questionable activity on my email system?
8. Make use of and to keep an eye on and assess email system-related activity.
9. How can I keep my encryption key safe?
10. Keep your encryption key safe, like in a hardware security module (HSM) or AWS Secrets Manager.
11. Why should I send emails using PHPMailer?
12. A reliable and user-friendly interface for sending emails securely via SMTP is offered by PHPMailer.
13. What should I do in the event that my SMTP credentials are compromised?
14. To avoid similar problems in the future, revoke the compromised credentials right away, issue fresh ones, and look into the source of the leak.
15. How can I update the Exim setup with new credentials automatically?
16. To edit the Exim configuration file, use a shell script that contains the commands. Then, use to apply the changes.

It's essential to keep your SES SMTP credentials secure to avoid misuse and illegal access. Vulnerabilities can be greatly decreased by limiting access using security groups and encrypting credentials. Furthermore, keeping an eye on your system's activities and changing your credentials on a regular basis might aid in the detection and prevention of security breaches. By putting these procedures into place, you may safeguard your domain's reputation and have a more secure email communication system.