encryption: it's for more than just password - tek13

ENCRYPTIONIt’s For More Than Just Passwords

1Thursday, May 16, 13

JOHN CONGDON


JOHN CONGDON

•PHP Developer Since 2003


JOHN CONGDON

•PHP Developer Since 2003• SDPHP User Group Organizer


JOHN CONGDON

•PHP Developer Since 2003• SDPHP User Group Organizer• Sr PHP Developer for Networx Online


JOHN CONGDON

•PHP Developer Since 2003• SDPHP User Group Organizer• Sr PHP Developer for Networx Online•PhoneBurner.com


JOHN CONGDON

•PHP Developer Since 2003• SDPHP User Group Organizer• Sr PHP Developer for Networx Online•PhoneBurner.com•MeetingBurner.com


JOHN CONGDON

•PHP Developer Since 2003• SDPHP User Group Organizer• Sr PHP Developer for Networx Online•PhoneBurner.com•MeetingBurner.com• FaxBurner.com


JOHN CONGDON

•PHP Developer Since 2003• SDPHP User Group Organizer• Sr PHP Developer for Networx Online•PhoneBurner.com•MeetingBurner.com• FaxBurner.com• I Am Not A Cryptographer


Hashing

Encryption

Today’s Discussion Points


Plain Text

$username = $_POST[‘username’];$password = $_POST[‘password’];

$user = getUserByUserName($username);

if ($user->password == $password) { $valid = true;} else { $valid = false;}


Plain Text: Vulnerabilities

SQL-Injection gives you every users password


Cryptographic Hashing



Wikipedia Definition: A cryptographic hash function is a hash function; that is, an algorithm that takes an arbitrary block of data and returns a fixed-size bitstring, the (cryptographic) hash value, such that any (accidental or intentional) change to the data will (with very high probability) change the hash value. The data to be encoded are often called the "message," and the hash value is sometimes called the message digest or simply digest.


https://en.wikipedia.org/wiki/Hash_function


https://en.wikipedia.org/wiki/Algorithm


https://en.wikipedia.org/wiki/Data


https://en.wikipedia.org/wiki/Bit




HASH

“message” “digest”












HASH


“unicorn” “1abcb33beeb811dca15f0ac3e47b88d9”










Cryptographic Hashing: One Way


Cryptographic Hashing: One Way

HASH


“unicorn” “1abcb33beeb811dca15f0ac3e47b88d9”


Cryptographic Hashing: Algorithms

<?phpprint_r(hash_algos());?>Array( [0] => md2 [1] => md4 [2] => md5 [3] => sha1 [4] => sha224 [5] => sha256 [6] => sha384 [7] => sha512 [8] => ripemd128 [9] => ripemd160 [10] => ripemd256 [11] => ripemd320 [12] => whirlpool [13] => tiger128,3

[14] => tiger160,3 [15] => tiger192,3 [16] => tiger128,4 [17] => tiger160,4 [18] => tiger192,4 [19] => snefru [20] => snefru256 [21] => gost [22] => adler32 [23] => crc32 [24] => crc32b [25] => salsa10 [26] => salsa20 [27] => haval128,3 [28] => haval160,3 [29] => haval192,3 [30] => haval224,3 [31] => haval256,3 [32] => haval128,4

[33] => haval160,4 [34] => haval192,4 [35] => haval224,4 [36] => haval256,4 [37] => haval128,5 [38] => haval160,5 [39] => haval192,5 [40] => haval224,5 [41] => haval256,5)


Cryptographic Hashing: Vulnerabilities

SQL-Injection gives you every users hashed password


Rainbow Table Example: Searched for a Hash


Salting Cryptographic Hashes



Wikipedia Definition: In cryptography, a salt is random data that are used as an additional input to a one-way function that hashes a password or passphrase.

A new salt is randomly generated for each password. In a typical setting, the salt and the password are concatenated and processed with a cryptographic hash function, and the resulting output (but not the original password) is stored with the salt in a database.


https://en.wikipedia.org/wiki/Cryptography


https://en.wikipedia.org/wiki/Random_Number_Generator


https://en.wikipedia.org/wiki/One-way_function




https://en.wikipedia.org/wiki/Password


https://en.wikipedia.org/wiki/Passphrase


https://en.wikipedia.org/wiki/Cryptographic_hash_function





$hash = md5(‘RAND_SALT’ . $_POST[‘password’]);



















$hash = md5(‘RAND_SALT’ . $_POST[‘password’]);

RAND_SALT must come from a cryptographically secure source.Not From (rand, mt_rand, or uniqid)Use (/dev/urandom, mcrypt, openssl)
















Today’s Best Practice: BCrypt



•Slower by design



•Slower by design•Configurable to help withstand the test of time (cost param)



•Slower by design•Configurable to help withstand the test of time (cost param)•Should be configured to take 0.25 to 0.50 a second



•Slower by design•Configurable to help withstand the test of time (cost param)•Should be configured to take 0.25 to 0.50 a second•Start with a cost of 10, use higher if possible


PHP 5.5 Password Hashing APIhttp://www.php.net/manual/en/ref.password.php


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


PHP 5.5 Password Hashing API







array password_get_info(string $hash)Returns 3 elementsalgorithm: Constant valuealgoName: bcryptoptions: the options provided to password_hash

Array( [algo] => 1 [algoName] => bcrypt [options] => Array ( [cost] => 11 )

)






boolean password_needs_rehash ( string $hash , string $algo [, string $options ] )

Assuming password_verify was successful above:

if (password_needs_rehash($hash, PASSWORD_DEFAULT, $options)) { $user->password = password_hash($password....); $user->update();}




I Lied: PHP >= 5.3.7 Password Hashing API

https://github.com/ircmaxell/password_compat

A forward compatible password API implementation that will work until you are ready to upgrade to 5.5. This will work for all versions of PHP that has the $2y fix.

Upgrading to 5.5 will not break your current code if you use this library.




Example: Creating a user

<?phprequire 'password.php';

$hash = password_hash($_POST[‘password’], PASSWORD_DEFAULT);if ($hash === false) { //handle this error case somehow...}

$user = Model_User::createNewUser($_POST[‘username’]);$user->setPassword($hash);$user->update();


Example: Logging a user in

<?phprequire 'password.php';

$user = Model_User::getUserByUserName($_POST[‘username’]);if (password_verify($_POST[‘password’], $user->password)) { return true;} else { die(“Invalid credentials”);}


Example: Logging a user in and checking for rehash

...$user = Model_User::getUserByUserName($_POST[‘username’]);if (password_verify($_POST[‘password’], $user->password)) { if (password_needs_rehash($user->password, $algo, $options)) { $hash = password_hash($_POST[‘password’], PASSWORD_DEFAULT, $options);

$user->setPassword($hash); $user->update(); }...


http://blog.ircmaxell.com/2013/01/password-storage-talk-at-php-benelux-13.htmlWant More? Get Statistics Here

One of my favorite data points from Anthony’s slides


http://blog.ircmaxell.com/2013/01/password-storage-talk-at-php-benelux-13.html

http://blog.ircmaxell.com/2013/01/password-storage-talk-at-php-benelux-13.html

Questions on Password Hashing?


More Than Just Passwords



We may store more sensitive data than just passwords.




Passwords are easy, we don’t care about the original value.





Decryption makes original value usable by us.





Decryption makes original value usable by us.

•Credit Card Info•Social Security Numbers•Date of Birth•Personally Identifiable Information


AVOID ENCRYPTION AT ALL COSTS!



Clarification: Avoid keeping any data that you need to encrypt.




Before deciding to keep any of this information, ask yourself why you need it.





Is the risk of potentially leaking this information worth the reward?






Are there alternative solutions?






Are there alternative solutions?Example: Credit card companies usually offer a token solution.


Symmetric vs Asymmetric



Symmetric

Only one shared keySame key encrypts and decryptsEasiest to understand



Symmetric

Only one shared keySame key encrypts and decryptsEasiest to understand

Asymmetric

Two keys (Public & Private)Encryption/DecryptionPublic key encryptsPrivate key decrypts

Signing/VerifyingPrivate key signsPublic key verifies


Common Asymmetric Uses

SSH KeysHTTPS / SSLPGP: Pretty Good Privacy Email Files Really any message


Keys, Ciphers, Modes, and Initialization Vectors Oh My!



• Keys, should be easy to understand (KEEP IT SECRET)



• Keys, should be easy to understand (KEEP IT SECRET)• Ciphers



• Keys, should be easy to understand (KEEP IT SECRET)• Ciphers• Deterministic algorithm (Ex: 3DES, Blowfish, TwoFish)



• Keys, should be easy to understand (KEEP IT SECRET)• Ciphers• Deterministic algorithm (Ex: 3DES, Blowfish, TwoFish)• Modes



• Keys, should be easy to understand (KEEP IT SECRET)• Ciphers• Deterministic algorithm (Ex: 3DES, Blowfish, TwoFish)• Modes• Determines how the key stream is used (never cross them)




• Avoid ECB (Electronic Code Book)




• Avoid ECB (Electronic Code Book)• (Use CBC or CFB, Cipher Block Chaining / Cipher FeedBack)




• Avoid ECB (Electronic Code Book)• (Use CBC or CFB, Cipher Block Chaining / Cipher FeedBack)• Initialization Vectors




• Avoid ECB (Electronic Code Book)• (Use CBC or CFB, Cipher Block Chaining / Cipher FeedBack)• Initialization Vectors• Similar to SALT in hashing (It’s not a secret)




• Avoid ECB (Electronic Code Book)• (Use CBC or CFB, Cipher Block Chaining / Cipher FeedBack)• Initialization Vectors• Similar to SALT in hashing (It’s not a secret)• Must be random per encrypted text


Example: Encrypt using crypt

$crypt_key = ‘xxxxxxxxxxxxxxxxxxxxxxxxxxx’;$message = ‘My Credit Card Number is 4123123412341234’;$iv_size = mcrypt_get_iv_size(MCRYPT_BLOWFISH, MCRYPT_MODE_CBC);$iv = mcrypt_create_iv($iv_size, MCRYPT_DEV_URANDOM);

$cipher = mcrypt_encrypt( MCRYPT_BLOWFISH, $crypt_key, $message, MCRYPT_MODE_CBC, $iv);


HMAC: Hash-based Message Authentication Code

Using a separate key, this will give us a signature letting us know that the data has not been tampered with.

When Encrypting: Always encrypt first, and then get signature of the Cipher Text.

Store it with your Initialization Vector and Cipher Text.

When Decrypting: Always verify signature first, and then decrypt if matched.


Example: Using HMAC

$crypt_key = ‘xxxxxxxxxxxxxxxxxxxxxxxxxxx’;$hmac_key = ‘yyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyy’;

$hmac = hash_hmac(‘sha512’, $cipher_text, $hmac_key);

//Store it with your encrypted data$encrypted = base64_encode($iv . $cipher . $hmac);


Example: Decrypt using HMAC and crypt

$crypt_key = ‘xxxxxxxxxxxxxxxxxxxxxxxxxxx’;$hmac_key = ‘yyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyy’;$iv_size = mcrypt_get_iv_size(MCRYPT_BLOWFISH, MCRYPT_MODE_CBC);$encrypted = base64_decode($encrypted);$iv = substr($encrypted, 0, $iv_size);$hmac = substr($encrypted, -64);$cipher = substr($encrypted, $iv_size, -64);if ($hmac != hash_hmac(‘sha512’, $cipher, $hmac_key)) { return false; }$message = mcrypt_decrypt( MCRYPT_BLOWFISH, $crypt_key, $cipher, MCRYPT_MODE_CBC, $iv);


Use a Library

http://phpseclib.sourceforge.net/

They’ve done the hard parts, save yourself the headache and just use it.It’s even PHP4+ compatible, so no excuses.




Example: Using phpseclib



$crypt_key = ‘xxxxxxxxxxxxxxxxxxxxxxxxxxx’;$hmac_key = ‘yyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyy’;$message = ‘My Credit Card Number is 4123123412341234’;

require ‘Crypt/DES.php’;require ‘Crypt/Hash.php’;

$des = new Crypt_DES();$des->setKey($crypt_key);$cipher = $des->encrypt($message);

$hash = new Crypt_Hash(‘sha512’);$hash->setKey($hmac_key);$hmac = bin2hex($hash->hash($cipher));



$crypt_key = ‘xxxxxxxxxxxxxxxxxxxxxxxxxxx’;$hmac_key = ‘yyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyy’;$message = ‘My Credit Card Number is 4123123412341234’;


$des = new Crypt_DES();$des->setKey($crypt_key);$cipher = $des->encrypt($message);

$hash = new Crypt_Hash(‘sha512’);$hash->setKey($hmac_key);$hmac = bin2hex($hash->hash($cipher));


$hash = new Crypt_Hash(‘sha512’);$hash->setKey($hmac_key);$verify_hmac = bin2hex($hash->hash($cipher));

if ($verify_hmac == $hmac) { $des = new Crypt_DES(); $des->setKey($crypt_key); $message = $des->decrypt($cipher);}


Encryption !== Protection

Data obtained through SQL Injection attacks or other non system penetration attacks should be relatively secure.

For us to encrypt/decrypt, we must have access to the key. Therefore, any breach of system security, will disclose the key to the attacker, leaving ALL encryption useless.

Apache environment variable, memory, config files, password entered during system startup, do not keep the key private.



There is no such thing as 100% secure.


Other Things To Consider



•Encrypt / decrypt on a separate server.



•Encrypt / decrypt on a separate server. •More overhead and complexity.



•Encrypt / decrypt on a separate server. •More overhead and complexity. •Any server breach can still decrypt data.



•Encrypt / decrypt on a separate server. •More overhead and complexity. •Any server breach can still decrypt data. •With enough thought and monitoring, you can kill the decryption server to limit the damage done.



•Encrypt / decrypt on a separate server. •More overhead and complexity. •Any server breach can still decrypt data. •With enough thought and monitoring, you can kill the decryption server to limit the damage done.•Think about restricting requests per second



Paranoid about password safety? Consider encrypting the hash. Renders SQL-Injection and rainbow tables/brute force useless.

•Encrypt / decrypt on a separate server. •More overhead and complexity. •Any server breach can still decrypt data. •With enough thought and monitoring, you can kill the decryption server to limit the damage done.•Think about restricting requests per second


Credits

I’ve learned a lot while preparing this presentation.

Thanks especially to Anthony Ferrara (@ircmaxell)http://blog.ircmaxell.com


http://blog.ircmaxell.com

http://blog.ircmaxell.com

Questions?


JOHN CONGDON

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https://joind.in/8179




JOHN CONGDON• twitter : @johncongdon






JOHN CONGDON• twitter : @johncongdon • email: [email protected]






JOHN CONGDON• twitter : @johncongdon • email: [email protected]• irc: freednode.net (#sdphp)






encryption: it's for more than just password - tek13

Technology

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cryptographic

simply digest

function thathashes

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