discourse/app/controllers/session_controller.rb

require_dependency 'rate_limiter'

class SessionController < ApplicationController

  skip_before_filter :redirect_to_login_if_required
  skip_before_filter :check_xhr, only: ['sso', 'sso_login', 'become']

  def csrf
    render json: {csrf: form_authenticity_token }
  end

  def sso
    if SiteSetting.enable_sso
      redirect_to DiscourseSingleSignOn.generate_url(params[:return_path] || '/')
    else
      render nothing: true, status: 404
    end
  end

  # For use in development mode only when login options could be limited or disabled.
  # NEVER allow this to work in production.
  def become
    raise Discourse::InvalidAccess.new unless Rails.env.development?
    user = User.find_by_username(params[:session_id])
    raise "User #{params[:session_id]} not found" if user.blank?

    log_on_user(user)
    redirect_to "/"
  end

  def sso_login
    unless SiteSetting.enable_sso
      render nothing: true, status: 404
      return
    end

    sso = DiscourseSingleSignOn.parse(request.query_string)
    if !sso.nonce_valid?
      render text: "Timeout expired, please try logging in again.", status: 500
      return
    end

    return_path = sso.return_path
    sso.expire_nonce!

    if user = sso.lookup_or_create_user
      if SiteSetting.must_approve_users? && !user.approved?
        # TODO: need an awaiting approval message here
      else
        log_on_user user
      end
      redirect_to return_path
    else
      render text: "unable to log on user", status: 500
    end
  end

  def create

    unless allow_local_auth?
      render nothing: true, status: 500
      return
    end

    RateLimiter.new(nil, "login-hr-#{request.remote_ip}", 30, 1.hour).performed!
    RateLimiter.new(nil, "login-min-#{request.remote_ip}", 6, 1.minute).performed!

    params.require(:login)
    params.require(:password)

    return invalid_credentials if params[:password].length > User.max_password_length

    login = params[:login].strip
    login = login[1..-1] if login[0] == "@"

    if user = User.find_by_username_or_email(login)

      # If their password is correct
      unless user.confirm_password?(params[:password])
        invalid_credentials
        return
      end

      # If the site requires user approval and the user is not approved yet
      if login_not_approved_for?(user)
        login_not_approved
        return
      end

      # User signed on with username and password, so let's prevent the invite link
      # from being used to log in (if one exists).
      Invite.invalidate_for_email(user.email)
    else
      invalid_credentials
      return
    end

    if user.suspended?
      failed_to_login(user)
      return
    end

    if ScreenedIpAddress.block_login?(user, request.remote_ip)
      not_allowed_from_ip_address(user)
      return
    end

    (user.active && user.email_confirmed?) ? login(user) : not_activated(user)
  end

  def forgot_password
    params.require(:login)

    unless allow_local_auth?
      render nothing: true, status: 500
      return
    end

    RateLimiter.new(nil, "forgot-password-hr-#{request.remote_ip}", 6, 1.hour).performed!
    RateLimiter.new(nil, "forgot-password-min-#{request.remote_ip}", 3, 1.minute).performed!

    user = User.find_by_username_or_email(params[:login])
    if user.present?
      email_token = user.email_tokens.create(email: user.email)
      Jobs.enqueue(:user_email, type: :forgot_password, user_id: user.id, email_token: email_token.token)
    end

    json = { result: "ok" }
    unless SiteSetting.forgot_password_strict
      json[:user_found] = user.present?
    end

    render json: json

  rescue RateLimiter::LimitExceeded
    render_json_error(I18n.t("rate_limiter.slow_down"))
  end

  def current
    if current_user.present?
      render_serialized(current_user, CurrentUserSerializer)
    else
      render nothing: true, status: 404
    end
  end

  def destroy
    reset_session
    log_off_user
    render nothing: true
  end

  private

  def allow_local_auth?
    !SiteSetting.enable_sso && SiteSetting.enable_local_logins
  end

  def login_not_approved_for?(user)
    SiteSetting.must_approve_users? && !user.approved? && !user.admin?
  end

  def invalid_credentials
    render json: {error: I18n.t("login.incorrect_username_email_or_password")}
  end

  def login_not_approved
    render json: {error: I18n.t("login.not_approved")}
  end

  def not_activated(user)
    render json: {
      error: I18n.t("login.not_activated"),
      reason: 'not_activated',
      sent_to_email: user.find_email || user.email,
      current_email: user.email
    }
  end

  def not_allowed_from_ip_address(user)
    render json: {error: I18n.t("login.not_allowed_from_ip_address", username: user.username)}
  end

  def failed_to_login(user)
    message = user.suspend_reason ? "login.suspended_with_reason" : "login.suspended"

    render json: { error: I18n.t(message, { date: I18n.l(user.suspended_till, format: :date_only),
                                            reason: user.suspend_reason}) }
  end

  def login(user)
    log_on_user(user)
    render_serialized(user, UserSerializer)
  end

end