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Chapter 3.3 - User authorization & safety
Maciej Mensfeld
Presented by:
Maciej Mensfeld
User authorization & safety
github.com/mensfeld
senior ruby [email protected] ruby [email protected]
Chapter 3.3 - User authorization & safety
Maciej Mensfeld
Presented by:
Maciej Mensfeld
User authorization & safety
github.com/mensfeld
senior ruby [email protected] ruby [email protected]
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
Chapter 3.3 - User authorization & safety
Maciej Mensfeld
Let’s start with a naive approach!
Password
LoginDB
Password
LoginDB
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: truepassword: string, null: false
Chapter 3.3 - User authorization & safety
Maciej Mensfeld
Quite good but…
What’s wrong with this approach?
Chapter 3.3 - User authorization & safety
Maciej Mensfeld
But we don’t have any data that…
Most of stolen data can be used somehow!
Chapter 3.3 - User authorization & safety
Maciej Mensfeld
Simple case study
SHA + Salt @ Shippuuden.pl
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
Secure Salted Password Hashing
Maciej Mensfeld
Chapter 3.3 - User authorization & safety
Secure Salted Password Hashing
Maciej Mensfeld
Chapter 3.3 - User authorization & safety
Chapter 3.3 - User authorization & safety
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.
4e2ecff8f8be5a7d4d8821266d956d844aa5b8eebd5983edbaaa6fa7fc9bc9e21de42d443f50d8608a79f6507b7e95c6d4a913615c85710f86a40bc23cdc5d5d
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}$
^(?=.*\d)(?=.*([a-z]|[A-Z]))([\x20-\x7E]){8,40}$
Maciej Mensfeld
Chapter 3.3 - User authorization & safety
Salt, salt, saltHow 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.
Maciej Mensfeld
Chapter 3.3 - User authorization & safety
Salt, salt, saltTo 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:
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
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
Ruby: User authorization & safety
Maciej Mensfeld
Live long and prosper!
Presented by:
Maciej Mensfeld
github.com/mensfeld