password hashing: the right way

Password Hashing: The Right Way

Jeremy Kendall - Memphis PHPJanuary 28, 2014

Wednesday, January 29, 14

I love to code


I love to code

I’m terribly forgetful


I love to code


I take pictures


I love to code


I take pictures

I work at OpenSky


I’m a Little Off My Game


What Qualifies Me To Talk About Security?


Not Much


Not MuchBut that will work in our favor ...


Cryptography is Hard


Cryptography is HardPro Tip: Leave it to the experts


The Wrong Way

<?php

class SecurityFail{ // Encrypt Passwords for Highest Level of Security. static public function encrypt($pword) { return md5($pword); }

}

http://csiphp.com/blog/2012/02/16/encrypt-passwords-for-highest-level-of-security/




The Right Way

http://php.net/manual/en/ref.password.php




The Awesomer Way


Password Hashing Functions


Password Hashing FunctionsPro Tip: Use password_compat for PHP 5.3.7+


Password Hashing FunctionsPro Tip: Use password_compat for PHP 5.3.7+

Pro Tip: Use phpass for PHP <= 5.3.6


password_hash

http://www.php.net/manual/en/function.password-hash.php




password_hash

‣ Creates a new password hash





password_hash


‣ Strong, one-way hashing algorithm





password_hash



‣ PASSWORD_DEFAULT or PASSWORD_BCRYPT





password_hash



‣ PASSWORD_DEFAULT or PASSWORD_BCRYPT

‣ Optional cost and salt





password_hash





password_hash

‣ Always use PASSWORD_DEFAULT





password_hash


‣ Your DB’s password field should be varchar(255)





password_hash



‣ Do not use your own salt





password_hash



‣ Do not use your own salt

‣ Check for an appropriate cost using the example script in the manual





password_hash

$hash = password_hash('secret pass', PASSWORD_DEFAULT);

// or

$options = array('cost' => 12);$hash = password_hash('secret pass', PASSWORD_DEFAULT, $options);


password_verify


password_verify

‣ Verifies that a password matches a hash


password_verify

‣ Verifies that a password matches a hash

‣ Uh, yeah, that’s about it


password_verify

$valid = password_verify($_POST['pass'], $hashFromDb);


password_needs_rehash



‣ Checks password to see if it needs to be updated



‣ Checks password to see if it needs to be updated

‣ Uses both hash and cost to check current hash



$needsRehash = password_needs_rehash($hashFromDb, PASSWORD_DEFAULT);

// or

$options = array('cost' => 12);$needsRehash = password_needs_rehash($hashFromDb, PASSWORD_DEFAULT, $options);


That’s Awesome and Secure


But Could It Be Awesomer, Securer, and Easier?


Password Validator


Password Validator

‣ Validates passwords against password_hash


Password Validator


‣Will rehash when needed


Password Validator



‣Will upgrade legacy passwords


Password Validator




‣ Requires PHP 5.3.7+


Password Validator




‣ Requires PHP 5.3.7+

‣ (No version for <=5.3.6 is in the works)


Password Validator

use JeremyKendall\Password\PasswordValidator;use JeremyKendall\Password\Result as ValidationResult;

$passwordHash = password_hash('password', PASSWORD_DEFAULT);

$validator = new PasswordValidator();$result = $validator->isValid('password', $passwordHash);

$valid = $result->isValid();$code = $result->getCode();

// $valid = true// $code = ValidationResult::SUCCESS


Password Validatoruse JeremyKendall\Password\PasswordValidator;use JeremyKendall\Password\Result as ValidationResult;

$options = array('cost' => 9);$passwordHash = password_hash('password', PASSWORD_DEFAULT, $options);

$validator = new PasswordValidator();$validator->setOptions($options);$result = $validator->isValid('password', $passwordHash);

$valid = $result->isValid();$code = $result->getCode();

// $valid = true// $code = ValidationResult::SUCCESS


Password Validatoruse JeremyKendall\Password\PasswordValidator;use JeremyKendall\Password\Result as ValidationResult;

$options = array('cost' => 9);$passwordHash = password_hash('password', PASSWORD_DEFAULT, $options);

$validator = new PasswordValidator();

// Remember, default cost is 10, so a cost 9 hash gets rehashed$result = $validator->isValid('password', $passwordHash);

$valid = $result->isValid();$code = $result->getCode();$hash = $result->getPassword();

// $valid = true// $code = ValidationResult::SUCCESS_PASSWORD_REHASHED// $hash = the new, rehashed password. Save it!


Fine, But We’re Not Using password_hash Yet ...


Decorator Pattern

http://en.wikipedia.org/wiki/Decorator_pattern




Decorator Pattern

‣Wrap an object





Decorator Pattern

‣Wrap an object

‣ Change its behavior





Decorator Pattern

‣Wrap an object

‣ Change its behavior

‣ Dynamically attach additional responsibilities





PasswordValidatorInterface

interface PasswordValidatorInterface{ public function isValid($password, $passwordHash, $identity = null);

public function rehash($password);

public function setOptions(array $options);

public function getOptions();}


Upgrade Decorator


Upgrade Decorator

‣ Used when you’re not already using password_hash ...


Upgrade Decorator


‣ ... but you’re ready to do things the right way


Upgrade Decorator



‣ Accepts an instance of PasswordValidatorInterface ...


Upgrade Decorator



‣ Accepts an instance of PasswordValidatorInterface ...

‣ ... and a validation callback


Upgrade Decorator

// Somewhere in your authentication scriptif (hash('sha512', $password) === $passwordHash) { $valid = true;}

$valid = false;


Upgrade Decorator

// Same authentication check expressed as a callback$validationCallback = function ($password, $passwordHash) { if (hash('sha512', $password) === $passwordHash) { return true; }

return false;};


Upgrade Decorator

$validator = new UpgradeDecorator( new PasswordValidator(), $validationCallback);

$passwordHash = hash('sha512', 'password');$result = $validator->isValid('password', $passwordHash);

$valid = $result->isValid();$code = $result->getCode();$hash = $result->getPassword();

// $valid = true// $code = ValidationResult::SUCCESS_PASSWORD_REHASHED// $hash = the new, rehashed password. Save it!


Fine, But Now I Have to Test for SUCCESS_PASSWORD_REHASHED

Every Time


Storage Decorator


Storage Decorator

‣ Automatically stores all rehashed passwords


Storage Decorator


‣ Accepts two constructor args:


Storage Decorator



‣ Instance of PasswordValidatorInterface


Storage Decorator



‣ Instance of PasswordValidatorInterface

‣ Instance of StorageInterface


StorageInterface

interface StorageInterface{ /** * Updates user's password in persistent storage * * @param string $identity Unique user identifier * @param string $password New password hash */ public function updatePassword($identity, $password);}


UserDaouse JeremyKendall\Password\Storage\StorageInterface;

class UserDao implements StorageInterface{ protected $db;

public function __construct(\PDO $db) { $this->db = $db; }

public function updatePassword($identity, $newPasswordHash) { $sql = 'UPDATE users SET passwordHash = :passwordHash WHERE identity = :identity'; $stmt = $this->db->prepare($sql); $stmt->execute(array('passwordHash' => $newPasswordHash, 'identity' => $identity));

return $this->find($identity); }}


Storage Decorator

use JeremyKendall\Password\Decorator\StorageDecorator;

$validator = new StorageDecorator($upgradeDecorator, $userDao);

// Uses the optional third argument for PasswordValidatorInterface::isValid()$result = $validator->isValid('password', $passwordHash, '[email protected]');

// Result is the same as any other validation attempt except ...// ... ValidationResult::SUCCESS_PASSWORD_REHASHED hashes are automatically persisted!


mailto:[email protected]

mailto:[email protected]

Recap


Recap

‣ Use the new PHP password hashing functions


Recap


‣ Use Password Validator to make it dead simple


Recap



‣ If you’re not at PHP 5.5, use password_compat


Recap




‣ If you’re not at PHP 5.3.7+, UPGRADE


Recap





‣ If you can’t upgrade, use OpenWall’s phpass


Recap





‣ If you can’t upgrade, use OpenWall’s phpass

‣ DO NOT ROLL YOUR OWN


Resources


Resources

‣ PHP Password Hashing Functions: http://php.net/password


http://php.net/password


Resources


‣ Original password_hash RFC: https://wiki.php.net/rfc/password_hash




https://wiki.php.net/rfc/password_hash


Resources



‣ Password Validator: https://github.com/jeremykendall/password-validator






https://github.com/jeremykendall/password-validator


Resources




‣ password_compat: https://github.com/ircmaxell/password_compat








https://github.com/ircmaxell/password_compat


Resources




‣ password_compat: https://github.com/ircmaxell/password_compat

‣ OpenWall phpass: http://www.openwall.com/phpass/










http://www.openwall.com/phpass/

http://www.openwall.com/phpass/

Thanks!

[email protected]

http://about.me/jeremykendall

@jeremykendall

http://365.jeremykendall.net






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