#-- encoding: UTF-8
#-- copyright
# OpenProject is a project management system.
# Copyright (C) 2012-2014 the OpenProject Foundation (OPF)
#
# This program is free software; you can redistribute it and/or
# modify it under the terms of the GNU General Public License version 3.
#
# OpenProject is a fork of ChiliProject, which is a fork of Redmine. The copyright follows:
# Copyright (C) 2006-2013 Jean-Philippe Lang
# Copyright (C) 2010-2013 the ChiliProject Team
#
# This program is free software; you can redistribute it and/or
# modify it under the terms of the GNU General Public License
# as published by the Free Software Foundation; either version 2
# of the License, or (at your option) any later version.
#
# This program is distributed in the hope that it will be useful,
# but WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
# GNU General Public License for more details.
#
# You should have received a copy of the GNU General Public License
# along with this program; if not, write to the Free Software
# Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301, USA.
#
# See doc/COPYRIGHT.rdoc for more details.
#++

class UserPassword < ActiveRecord::Base
  belongs_to :user, inverse_of: :passwords

  # passwords must never be modified, so doing this on create should be enough
  before_create :salt_and_hash_password!

  attr_accessor :plain_password

  # Checks whether the stored password is the same as a given plaintext password
  def same_as_plain_password?(plain_password)
    UserPassword.secure_equals?(UserPassword.hash_with_salt(plain_password,
                                                            salt),
                                hashed_password)
  end

  def expired?
    days_valid = Setting.password_days_valid.to_i.days
    return false if days_valid == 0
    created_at < (Time.now - days_valid)
  end

  # Returns a 128bits random salt as a hex string (32 chars long)
  def self.generate_salt
    SecureRandom.hex(16)
  end

  # Return password digest
  def self.hash_password(plain_password)
    Digest::SHA1.hexdigest(plain_password)
  end

  # Hash a plaintext password with a given salt
  # The hashed password has following form: SHA1(salt + SHA1(password))
  def self.hash_with_salt(plain_password, salt)
    # We should really use a standard key-derivation function like bcrypt here
    hash_password("#{salt}#{hash_password plain_password}")
  end

  # constant-time comparison algorithm to prevent timing attacks
  def self.secure_equals?(a, b)
    return false if a.blank? || b.blank? || a.bytesize != b.bytesize
    l = a.unpack "C#{a.bytesize}"

    res = 0
    b.each_byte { |byte| res |= byte ^ l.shift }
    res == 0
  end

  private

  def salt_and_hash_password!
    return if plain_password.nil?
    self.salt = UserPassword.generate_salt
    self.hashed_password = UserPassword.hash_with_salt(plain_password,
                                                       salt)
  end
end