Dealing with Passwords in Java Applications: 5 Best Practices You Should Follow

 In modern Java applications—whether core Java applications or enterprise-level web applications—working with passwords is inevitable. Passwords are sensitive pieces of information, just like Social Security Numbers (SSNs), and if you’re handling real human data in systems such as online banking or healthcare portals, it’s critical to implement best practices for dealing with passwords securely.

Below, I’ll share five essential best practices that I’ve learned and recommend for managing passwords, particularly when you are handling authentication and authorization. While these tips are a good starting point, be sure to tailor them to your application’s requirements and security policies.

1) Use SSL/TLS to Transfer Username and Password

When users send passwords over the network, it is crucial to use SSL/TLS to encrypt the communication. This ensures that sensitive information is protected from eavesdroppers. Tools like LDAP and Active Directory are commonly used for storing usernames, passwords, and roles. However, you must ensure that passwords are passed from the user to the LDAP server securely.

Example: In a Java-based web application, you can enforce SSL by configuring your Spring Boot application with:

• server.ssl.key-store=classpath:keystore.jks
• server.ssl.key-store-password=changeit
• server.ssl.key-alias=myalias

This ensures that all HTTP requests to sensitive endpoints are encrypted using HTTPS.

2) Store Passwords in char[] Instead of String

In Java, String objects are immutable, meaning once they are created, their contents cannot be altered. This poses a security risk since strings that contain passwords can be inadvertently stored in memory for longer than intended, and might even be accessible through memory dumps or debugging tools. Since char[] can be manually cleared after use, it’s a better option for storing passwords.

Example:

char[] password = {'s', 'e', 'c', 'r', 'e', 't'};
// Do your authentication...
Arrays.fill(password, ' '); // Clear password from memory

3) Encrypt or Hash Passwords Before Storing

Never store passwords in plain text! Always hash or encrypt passwords before storing them in a database. Hashing with a salt ensures that even identical passwords result in different hashes, adding an extra layer of protection against brute-force attacks.

Example: Use a secure hashing algorithm like PBKDF2, bcrypt, or Argon2.

import org.springframework.security.crypto.bcrypt.BCryptPasswordEncoder;

BCryptPasswordEncoder passwordEncoder = new BCryptPasswordEncoder();
String hashedPassword = passwordEncoder.encode("myPassword123");

This hash can now be safely stored in the database. When authenticating, you compare the hashed version of the password provided by the user with the stored hash.

4) Clear Passwords as Soon as Possible

The longer sensitive information like passwords or SSNs stays in memory, the higher the risk of it being exposed. Clear passwords as soon as they are no longer needed by overwriting them with dummy values or null.

Example: Once a password is no longer required for authentication, manually clear it:

Arrays.fill(password, ' '); // Wipe the password

5) Do Not Cache Passwords

Never store passwords in memory for future use or to avoid repetitive authentication checks. Caching increases the attack surface. Re-authenticate the user when necessary instead of keeping the password or token in memory.

6) Hide Passwords in the User Interface

When collecting passwords from users, ensure they are not displayed in plain text. Use controls like JPasswordField in desktop applications or the <input type="password"> element in web applications to mask passwords.

Example:

<input type="password" name="userPassword" />

7) Avoid Logging Passwords or Sensitive Information

Sensitive information, including passwords and SSNs, should never be logged or printed to the console. Logging libraries might expose them accidentally through error messages, stack traces, or debug logs. Instead, log only sanitized error messages and handle exceptions carefully.

Example:

try {
    authenticateUser(username, password);
} catch (AuthenticationException e) {
    log.error("Authentication failed for user: {}", username); // Do not log the password
}

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Final Thoughts

The practices mentioned here are just the basics of securing passwords and sensitive data in a Java application. In enterprise environments, stricter and more specialized guidelines may exist. Nevertheless, implementing these practices can greatly reduce the risk of exposing sensitive data and help ensure that your application is more secure.

What other practices do you follow when working with sensitive information in Java? Let me know in the comments below!