Скачать или смотреть Converting mcrypt_encrypt to openssl_encrypt

Discover how to seamlessly transition from `mcrypt_encrypt` to `openssl_encrypt` for PHP encryption. Follow our detailed guide to resolve padding issues and enhance security.
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Converting mcrypt_encrypt to openssl_encrypt: A Step-by-Step Guide

If you're working with legacy PHP code, particularly a WordPress plugin that utilizes the obsolete mcrypt library, you may find yourself needing to switch to the more current openssl library for data encryption. However, making this transition isn't always straightforward. Many developers encounter discrepancies in the encrypted outputs when using functions like mcrypt_encrypt versus openssl_encrypt.

In this guide, we will explore a common issue developers face during this transition and outline a comprehensive solution to ensure compatibility between the two encryption methods.

The Problem

While trying to upgrade from mcrypt_encrypt to openssl_encrypt, one developer faced issues where the outputs generated by these methods were inconsistent. After extensive searching for answers, it became apparent that the problem stemmed from padding differences between the two libraries.

Specifics of the Issue

The developer was using both a static initialization vector (IV) and salt, which can contribute to vulnerabilities.

The openssl_encrypt function output was different from mcrypt_encrypt, leading to incompatibility with the external system being interfaced with.

Understanding the Solution

To resolve the encryption disparities between the two functions, we need to delve into two key areas: Base64 encoding and padding. Here's how to achieve similar outcomes from both encryption methods.

Step 1: Adjust Base64 Encoding

In the current implementation of the encryptSSL method, the data is being encoded in Base64 twice: once with an explicit call and once implicitly as a part of the openssl_encrypt function. To fix this, you should adjust the function to remove one of the Base64 encodings.

Action:
Remove the base64_encode call in encryptSSL(). This will help ensure that the data gets encoded only once while maintaining the integrity of the output.

Step 2: Overcoming Padding Differences

mcrypt employs Zero padding, whereas PHP/OpenSSL typically uses PKCS# 7 padding. To align the behavior of openssl_encrypt with that of mcrypt_encrypt, you need to implement explicit Zero padding in your code.

Action:
Implement a function to handle zero-padding and adjust the encryptSSL() method accordingly:

Example Code Adjustment:

[[See Video to Reveal this Text or Code Snippet]]

Implementing Zero Padding

Here is a useful function that can be added to your class to handle Zero padding:

[[See Video to Reveal this Text or Code Snippet]]

Final Thoughts on Changes

With these modifications, your encryptSSL() function should consistently produce outputs equivalent to encryptMCRYPT(). However, it’s essential to note that Zero padding, while used in this case, can be less secure than PKCS# 7 padding.

Important Security Considerations

Initialization Vector (IV) and Salt: Always use randomly generated values instead of static ones. This prevents vulnerabilities and ensures stronger encryption.

PBKDF2 Iteration Count: The iteration count of 100 for PBKDF2 is generally too low, so consider increasing it for better security.

Conclusion

Converting from mcrypt_encrypt to openssl_encrypt can indeed present challenges, particularly with padding and encoding. By following the outlined steps and making the necessary adjustments to your code, you can achieve consistent encryption outputs. Remember to always prioritize security by enhancing your code with best practices regarding IVs, salts, and iteration counts.

Feel free to reach out or leave a comment below if you have further questions or need assistance with your encryption implementations!