Fix: Add type check to hash before passing it to has_equals to prevent warning

[Debarghya-Banerjee]

Trac Ticket: Core-59824

Summary

• This pull request addresses a bug where the hash_equals() function in the wp_check_password() function would throw an error when it received a null value as one of its arguments. This issue occurs when the hash comparison logic inadvertently passes null, causing PHP to raise a TypeError in certain edge cases, especially when a hacker attempts to pass null values in an attack. The fix ensures that both the hash and the plaintext password are properly validated as strings before calling hash_equals() and CheckPassword().

Changes

• Added type checks before invoking the hash_equals() function to ensure both the $hash and the result of md5($password) are valid strings.

• Similarly, added type checks before calling $wp_hasher->CheckPassword() to ensure both $password and $hash are strings.

• The function now gracefully handles invalid or unexpected input (such as null values) by returning false instead of causing a fatal error.

Why is this important?

• This change ensures that the wp_check_password() function will:

  • Avoid throwing errors when invalid inputs (like null) are provided, especially in cases of malicious requests.

  • Improve the robustness of the password-checking process, making it more secure and resilient to unexpected input.

  • Provide greater compatibility with PHP versions that support hash_equals() and newer password hashing protocols.

[github-actions]

The following accounts have interacted with this PR and/or linked issues. I will continue to update these lists as activity occurs. You can also manually ask me to refresh this list by adding the props-bot label.

Core Committers: Use this line as a base for the props when committing in SVN:

Props debarghyabanerjee.

To understand the WordPress project's expectations around crediting contributors, please review the Contributor Attribution page in the Core Handbook.

[github-actions]

Test using WordPress Playground

The changes in this pull request can previewed and tested using a WordPress Playground instance.

WordPress Playground is an experimental project that creates a full WordPress instance entirely within the browser.

Some things to be aware of

• The Plugin and Theme Directories cannot be accessed within Playground.
• All changes will be lost when closing a tab with a Playground instance.
• All changes will be lost when refreshing the page.
• A fresh instance is created each time the link below is clicked.
• Every time this pull request is updated, a new ZIP file containing all changes is created. If changes are not reflected in the Playground instance,
  it's possible that the most recent build failed, or has not completed. Check the list of workflow runs to be sure.

For more details about these limitations and more, check out the Limitations page in the WordPress Playground documentation.

Test this pull request with WordPress Playground.