Converting existing password hash to Devise

Question

I'm trying to convert an existing Admin model to Devise. We already have a password hash but it's obviously not Devise compatible. What I would like to do is accept the login form and check the provided password against the encrypted password. If it's not correct, use the old hash to check the password and if it matches, empty the old password_hash field and set Devise's password to the provided password and save the model.

What's the best way to move forward? I suspect that I need to override something, perhaps in a custom controller, but I'm not entirely sure how to proceed.

Answer 1

You can let Devise do the "hard work" of encrypting the password with the new crypt scheme, as shown in https://gist.github.com/1704632:

class User < ActiveRecord::Base
  alias :devise_valid_password? :valid_password?

  def valid_password?(password)
    begin
      super(password)
    rescue BCrypt::Errors::InvalidHash
      return false unless Digest::SHA1.hexdigest(password) == encrypted_password
      logger.info "User #{email} is using the old password hashing method, updating attribute."
      self.password = password
      true
    end
  end
end

Answer 2

Using the bcrypt encryptor in Devise, this is what I ended up doing with my legacy data:

In models/user.rb

# Because we have some old legacy users in the database, we need to override Devises method for checking if a password is valid.
# We first ask Devise if the password is valid, and if it throws an InvalidHash exception, we know that we're dealing with a
# legacy user, so we check the password against the SHA1 algorithm that was used to hash the password in the old database.
alias :devise_valid_password? :valid_password?
def valid_password?(password)
  begin
    devise_valid_password?(password)
  rescue BCrypt::Errors::InvalidHash
    Digest::SHA1.hexdigest(password) == encrypted_password
  end
end

As you can see, devise throws an InvalidHash exception when it encounters an invalid hash, which it would do when authenticating a legacy user. I use this to fall back to the hashing-algorithm used to create the original legacy hash.

It doesn't change the password though, but that could simply be added to the method if needed.