Should You Cleanse User Passwords Before Hashing in PHP?

PHP Password Handling: Ditch the Old Password Cleaning Methods

Many PHP developers are used to cleaning data when dealing with passwords. However, when using PHP's password_hash() function, this step is not only redundant, but also reduces security.

Why is it not recommended to clean your password?

• Code redundancy: Adding sanitization mechanisms for passwords increases code complexity.
• No security benefit: Hashed passwords pose no SQL injection threat, so the additional sanitization is redundant from a security perspective.
• Reduce password entropy: Trimming or cleaning a password may remove characters that contribute to its uniqueness and strength. For example, removing spaces from a password significantly reduces its entropy value.

Advantages of direct hashing without cleaning

Prevent SQL injection:

Hashing algorithm converts the password into a secure format, even if the password contains malicious characters, the SQL engine cannot misinterpret it.

Flexibility:

Allowing users to use any length, spaces, or special characters in their passwords can increase password complexity and make it more resistant to brute force attacks.

Hash mechanism:

PASSWORD_BCRYPT (Default Hash Algorithm) Generates a 60-character hash containing a random salt and the hashed password. This ensures that each user's hash is unique even if the password is the same.

Examples of consequences of password cleaning:

Consider the following password:

<code>I'm a "dessert topping" & a <floor wax>!</code>

Applying common sanitization methods before hashing yields dramatically different results:

• trim: Remove trailing spaces.
• htmlentities/htmlspecialchars: Change special characters such as quotes and angle brackets.
• addslashes: Adds escape characters before special characters.
• strip_tags: Remove HTML tags.

Using any of these methods before hashing will cause differences in the password verification process, requiring the same sanitization method to be applied before each verification.

Conclusion

Sanitizing user-supplied passwords before hashing them is an unnecessary practice that reduces security and increases code complexity. It is recommended to use password_hash() directly to store passwords securely without additional cleanup steps.

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