1. Chapter 3.3 - User authorization & safety Maciej Mensfeld Presented by: Maciej Mensfeld User authorization & safety maciej@mensfeld.pl dev.mensfeld.pl github.com/mensfeld senior ruby developer@wordwatch.com senior ruby developer@furioustribe.com

2. Chapter 3.3 - User authorization & safety Maciej Mensfeld Presented by: Maciej Mensfeld User authorization & safety maciej@mensfeld.pl dev.mensfeld.pl github.com/mensfeld senior ruby developer@wordwatch.com senior ruby developer@furioustribe.com

3. Ruby on Rails: User authorization & safety Maciej Mensfeld Please… …ask me to slow down, if I speak to quickly; …ask me again, if I forget; …ask questions, if anything i say is not clear; …feel free to share your own observations User authorization & safety

4. Chapter 3.3 - User authorization & safety Maciej Mensfeld Let’s start with a naive approach! Password Login DB Password Login DB

5. Chapter 3.3 - User authorization & safety Maciej Mensfeld And… let’s do it! User model (or an update if already exist) rails g migration NAME login: string, null: false, unique: true password: string, null: false

6. Chapter 3.3 - User authorization & safety Maciej Mensfeld Quite good but… What’s wrong with this approach?

7. Chapter 3.3 - User authorization & safety Maciej Mensfeld But we don’t have any data that… Most of stolen data can be used somehow!

8. Chapter 3.3 - User authorization & safety Maciej Mensfeld Simple case study SHA + Salt @ Shippuuden.pl

9. Maciej Mensfeld You should not use MD5 You should not use MD5(MD5) Any Hash algorithm can be broken with bruteforce attack Any bruteforce attack can be faster with rainbow tables It is way easier when passwords are short :) Static vs dynamic salt md5(md5), sha2(sha2) Chapter 3.3 - User authorization & safety Simple case study

10. Secure Salted Password Hashing Maciej Mensfeld Chapter 3.3 - User authorization & safety

11. Secure Salted Password Hashing Maciej Mensfeld Chapter 3.3 - User authorization & safety

12. Maciej Mensfeld What is a cryptographic hash? A cryptographic hash function is a deterministic procedure that takes an arbitrary block of data and returns a fixed-size bit string, the (cryptographic) hash value, such that an accidental or intentional change to the data will change the hash value. The data to be encoded is often called the “message,” and the hash value is sometimes called the message digest or simply digest. 4e2ecff8f8be5a7d4d8821266d956d844aa5b8eebd5983edbaaa6fa7fc9bc9e21 de42d443f50d8608a79f6507b7e95c6d4a913615c85710f86a40bc23cdc5d5d

13. Chapter 3.3 - User authorization & safety Maciej Mensfeld Passwords should not be weak! When we store users passwords in our systems (databases, files, etc), they should be safe. If we get hacked and our database will get stolen, passwords should be protected. No one should be able to read them. Most users have one password for all their web-activities, so if this password get stolen, probably cracker will be able to log in into victim Facebook, Twitter and any other web accounts. But what about brute-force attacks? Any password should be validated before use. They should not be to short or two simple. We can do it by using regular expression: ^(?=.*\d)(?=.*([a-z]|[A-Z]))([\x20-\x7E]){8,40}$

14. Maciej Mensfeld Chapter 3.3 - User authorization & safety Salt, salt, salt How tu generate and use salt? The easiest way is to use one, global salt. Example: As you can see above – using salt will dramatically increase password power. One global salt has one major and really big disadvantage. If two users have same password they will also have same output hash. So, if we have a lot of users and some of them have same hashed password, we need to figure out only one hash and we will have access to accounts of the rest of users with same hash. We can also generate our own rainbow table dedicated for our cryptographic hash function and salt.

15. Maciej Mensfeld Chapter 3.3 - User authorization & safety Salt, salt, salt To protect against such behaviours we should use uniq per user salt. How to generate such salt? Combine some per user data and some random stuff. Example: We store salt with password hash. Don’t worry – it is safe. Since each user has his own uniq hash, there does not exist any general rainbow table. Mix password, dynamic and static salt and you will be safe. Furthermore, when mixing salts and password in a uniq way – until cracker steals database and source codes, he will not know how to generate rainbow tables. Example:

16. Maciej Mensfeld Chapter 3.3 - User authorization & safety Let’s implement! require ‘digest/sha2’ What do we need? Password and password confirmation salt (persisted) hashed_password (persisted) Login Logout password checker hashed password generator salt generator

17. Maciej Mensfeld Chapter 3.3 - User authorization & safety Spec for User model Put the test spec into test/units directory ruby -Itest./test/units/user_test.rb

18. Ruby: User authorization & safety Maciej Mensfeld Live long and prosper! Presented by: Maciej Mensfeld maciej@mensfeld.pl dev.mensfeld.pl github.com/mensfeld