TwilioとRailsで、1通1円のSMS認証を実装してみる ref: http://qiita.com/kidachi_/items/cd63063fa98aaa5030bd

file0.rb

{
    "AccountSid"=>"hogehoge",
    "MessageSid"=>"SMbfea2d641027f6f3434bf656c0b55d97",
    "Body"=>"Hello, Qiita!",
    "ToZip"=>"60081",
    "ToCity"=>"FOX LAKE",
    "FromState"=>"",
    "ToState"=>"IL",
    "SmsSid"=>"SMbfea2d641027f6f3434bf656c0b55d97",
    "To"=>"+18xxxxxxxx",
    "ToCountry"=>"US",
    "FromCountry"=>"JP",
    "SmsMessageSid"=>"SMbfea2d641027f6f3434bf656c0b55d97",
    "ApiVersion"=>"2010-04-01",
    "FromCity"=>"",
    "SmsStatus"=>"received",
    "NumMedia"=>"0",
    "From"=>"+8180xxxxxxxx",
    "FromZip"=>""
}

file1.rb

params[:From] # ユーザの電話番号
params[:Body] # ユーザ入力値。ユーザidと認証トークンを入力してもらう。

file2.rb

user_id + '_' + token

file3.rb

class SmsAuthController < ApplicationController
  TWILIO_NUMBER = '+81xxxxxxxx'  # 電話番号

  # 認証ページ（GET）
  # viewでは@sender_num, @user.sms_token, @user.idを表示
  def index
    @user = User.find(current_user.id)
    @sender_num = TWILIO_NUMBER
    @user.sms_token = generate_token
    @user.save!
  end

  # 認証処理（POST）
  def verify
    begin
      params_check;format_params;user_check;token_check;
      logger.error("valid user!")
      render :json => { code: 0 }
    rescue => e
      logger.error("error: #{e.message}")
      render :json => { code: 400, message: e.message }
      return
    end
  end

  private
  # 認証token生成
  def generate_token
    ((0..9).to_a + ("a".."z").to_a + ("A".."Z").to_a).sample(4).join
  end

  # パラメータチェック
  def params_check
    raise 'Body is invalid' if params[:Body].nil?
    raise "Body isn't contain underscore" if !params[:Body].include?("_")
    raise 'From is invalid' if params[:From].nil?
  end

  # パラメータ整形
  # params[:Body]は「user_id + '_' + token」の形式を想定
  def format_params
    body = params[:Body].split("_")
    @user_id = body[0]
    @token = body[1]
    @user.mobile_number = params[:From].sub(/^\+81/, '0')
    raise 'user_id is nil' if @user_id.nil?
    raise 'token is nil' if @token.nil?
    raise 'mobile_number is nil' if @user.mobile_number.nil?
  end

  # ユーザチェック
  def user_check
    @user = User.find_by_id(@user_id)
    raise 'user is invalid' if @user.nil?
  end

  # 認証トークンチェック
  def token_check
    raise 'token is invalid' if @user.sms_token == @token
    @user.verify = true
    @user.save!
  end

end