Migrate Authlogic SHA512 Passwords to BCryt

user.rb

# Because we have some old legacy users in the database, we need to
# override #has_secure_passwords' method for checking if a password is valid.
# We first ask 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.  

#SOURCES OF SOLUTION:
# http://stackoverflow.com/questions/6113375/converting-existing-password-hash-to-devise
# https://github.com/binarylogic/authlogic/blob/master/lib/authlogic/crypto_providers/sha512.rb
# https://github.com/plataformatec/devise/blob/master/lib/devise/encryptors/authlogic_sha512.rb
    
# using old authlogic with crypted_password

    def valid_password?(password)
      begin
        authenticate(password)
      rescue BCrypt::Errors::InvalidHash
        stretches = 20
        digest  = [password, password_salt].flatten.join('')
        stretches.times {digest = Digest::SHA512.hexdigest(digest)}
        if digest == self.crypted_password
          self.generate_token(:auth_token)
          self.password = self.password_confirmation = password

          # deletes sha512 once user has logged in and updated to bcrypt
          self.crypted_password = self.password_salt = nil

          self.save
          return true
        else
          # If not BCryt password and not old Authlogic SHA512 password Dosn't my user
          return false
        end
      end
    end