Should I Cleanse User Passwords Before Hashing Them?

Cleansing User Passwords

When developing secure applications, developers often consider cleansing passwords provided by users before storing them encrypted. However, applying cleansing mechanisms to passwords before hashing presents certain complications.

Avoid Cleansing Passwords Before Hashing

It is paramount to refrain from cleansing passwords using functions such as escape_string(), htmlspecialchars(), or addslashes(). The primary reason for this is that such preprocessing is redundant and unnecessary.

Hashes generated by PHP's password_hash() function, which is commonly used for password storage, do not pose SQL injection threats. The hashing process converts the password into a hash that cannot be exploited by SQL injection.

Hashes Offer Security Without Cleansing

Hashing functions do not assign special meaning to specific characters; therefore, no cleansing is required for security purposes. By allowing users to specify any password they desire, including spaces and special characters, hashing ensures the password's security, regardless of its contents.

Storage Considerations

While the default hashing method (PASSWORD_BCRYPT) generates a 60-character wide hash, it is recommended to allocate more space for storage, such as VARCHAR(255) or TEXT, to accommodate potential future changes in hashing algorithms.

Example of Ineffectiveness of Cleansing

Consider the password "I'm a "dessert topping" & a !". Applying various sanitizing methods yields different results:

• trim() removes trailing spaces
• htmlentities() and htmlspecialchars() encode special characters and double quotes
• addslashes() adds escape characters
• strip_tags() removes HTML tags

However, these transformations have no impact on the security of the hashed password. password_verify() will only succeed if the same cleansing method is applied to both the provided password and the hashed equivalent retrieved from the database.

Conclusion

In conclusion, avoid cleansing passwords before hashing with password_hash(). Doing so is unnecessary and introduces complexities. Instead, rely on the security provided by hashing algorithms and consider their potential storage requirements.

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