Inconsistent hash with Spring Boot BCryptPasswordEncoder matches() method [duplicate]

Question

In my project, I'm using BCryptPasswordEncoder as a way to encode my passwords. As long as I don't shut my machine off, everything works fine, however, when re-running my code, BCryptpasswordEncoder gets re-initialized as well, resetting its hash, making the matches() method not work with the passwords in my storage, which were created with the previous hash.

Here is the piece of code I am talking about:

        PasswordEncoder encoder = new BCryptPasswordEncoder();
        User u = this.dataSource.getUserByUsername(username);
        String passwordEncoded = encoder.encode(password);
        if (u == null) {
            return "No such user";
        } else {
            if (encoder.matches(password, u.getPassword())) {
                return passwordEncoded;
            } else {
                return "Incorrect password";
            }
        }

I know that keeping a consistent hash would defeat the purpose of encoding in general, but the way it is now, shutting anything off renders all my previous user entries in my repository useless. Is there anything I can about this?

Answer 1

BCryptpasswordEncoder automatically salts the passwords. The specific salt that they append to the password is randomly generated every time it is initialized.

When you reinitialize BCryptpasswordEncoder, you are generating a new salt to append to the password, so naturally, the results would be different.

You can find out how to overcome this problem here