module ActiveModel::SecurePassword::ClassMethods

# File activemodel/lib/active_model/secure_password.rb, line 61
def has_secure_password(attribute = :password, validations: true)
  # Load bcrypt gem only when has_secure_password is used.
  # This is to avoid ActiveModel (and by extension the entire framework)
  # being dependent on a binary library.
  begin
    require "bcrypt"
  rescue LoadError
    $stderr.puts "You don't have bcrypt installed in your application. Please add it to your Gemfile and run bundle install"
    raise
  end

  include InstanceMethodsOnActivation.new(attribute)

  if validations
    include ActiveModel::Validations

    # This ensures the model has a password by checking whether the password_digest
    # is present, so that this works with both new and existing records. However,
    # when there is an error, the message is added to the password attribute instead
    # so that the error message will make sense to the end-user.
    validate do |record|
      record.errors.add(attribute, :blank) unless record.send("#{attribute}_digest").present?
    end

    validates_length_of attribute, maximum: ActiveModel::SecurePassword::MAX_PASSWORD_LENGTH_ALLOWED
    validates_confirmation_of attribute, allow_blank: true
  end
end

Adds methods to set and authenticate against a BCrypt password. This mechanism requires you to have a XXX_digest attribute. Where XXX is the attribute name of your desired password.

The following validations are added automatically:

• Password must be present on creation

• Password length should be less than or equal to 72 bytes

• Confirmation of password (using a XXX_confirmation attribute)

If confirmation validation is not needed, simply leave out the value for XXX_confirmation (i.e. don't provide a form field for it). When this attribute has a nil value, the validation will not be triggered.

For further customizability, it is possible to suppress the default validations by passing validations: false as an argument.

Add bcrypt (~> 3.1.7) to Gemfile to use has_secure_password:

gem 'bcrypt', '~> 3.1.7'

Example using Active Record (which automatically includes ActiveModel::SecurePassword):

# Schema: User(name:string, password_digest:string, recovery_password_digest:string)
class User < ActiveRecord::Base
  has_secure_password
  has_secure_password :recovery_password, validations: false
end

user = User.new(name: 'david', password: '', password_confirmation: 'nomatch')
user.save                                                       # => false, password required
user.password = 'mUc3m00RsqyRe'
user.save                                                       # => false, confirmation doesn't match
user.password_confirmation = 'mUc3m00RsqyRe'
user.save                                                       # => true
user.recovery_password = "42password"
user.recovery_password_digest                                   # => "$2a$04$iOfhwahFymCs5weB3BNH/uXkTG65HR.qpW.bNhEjFP3ftli3o5DQC"
user.save                                                       # => true
user.authenticate('notright')                                   # => false
user.authenticate('mUc3m00RsqyRe')                              # => user
user.authenticate_recovery_password('42password')               # => user
User.find_by(name: 'david').try(:authenticate, 'notright')      # => false
User.find_by(name: 'david').try(:authenticate, 'mUc3m00RsqyRe') # => user