[RFC] Add PASSWORD_BCRYPT_SHA256 to password_hash

Hello, I propose to add a new hashing algorithm to use in password_hash and password_verify. RFC: https://wiki.php.net/rfc/bcrypt_sha256 PR: https://github.com/php/php-src/pull/24073 The existing bcrypt has problems with null bytes and only hashes the first 72 bytes. The proposed PASSWORD_BCRYPT_SHA256 algorithm solves those problems by first hashing the password with HMAC SHA256 before passing it through bcrypt. Tim suggested this in the discussion on my earlier RFC to throw errors on passwords longer than 72 bytes (https://wiki.php.net/rfc/bcrypt_max_password_length). That suggestion receives much criticism because of its backwards incompatibility, and I don't think it is worth pursuing further at the moment. I think this new hash is a gentler way to solve the underlying problem. Regards, Sjoerd Langkemper