Encryption: It's For More Than Just Password - tek13

ENCRYPTION
It’s For MoreThan Just Passwords
1Thursday, May 16, 13

JOHN CONGDON

JOHN CONGDON
•PHP Developer Since 2003

JOHN CONGDON
•SDPHP User Group Organizer

JOHN CONGDON
•Sr PHP Developer for Networx Online

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•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.

H
A
S
H
“message” “digest”

H
A
S
H
“unicorn” “1abcb33beeb811dca15f0ac3e47b88d9”

Cryptographic Hashing: One Way

Cryptographic Hashing: One Way
H
A
S
H
“unicorn” “1abcb33beeb811dca15f0ac3e47b88d9”

Cryptographic Hashing: Algorithms
<?php
print_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.

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

in a database.
$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
•Should be conﬁgured to take 0.25 to 0.50 a second

•Slower by design
•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 API
http://www.php.net/manual/en/ref.password.php

array password_get_info(string $hash)
Returns 3 elements
algorithm: Constant value
algoName: bcrypt
options: 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
<?php
require '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(); 20Thursday, May 16, 13

Example: Logging a user in
<?php
require '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.html
Want More? Get Statistics Here
One of my favorite data points from Anthony’s slides

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 key
Same key encrypts and decrypts
Easiest to understand

Symmetric
Only one shared key
Same key encrypts and decrypts
Easiest to understand
Asymmetric
Two keys (Public & Private)
Encryption/Decryption
Public key encrypts
Private key decrypts
Signing/Verifying
Private key signs
Public key veriﬁes

Common Asymmetric Uses
SSH Keys
HTTPS / SSL
PGP: 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)

• Ciphers

• Ciphers
• Deterministic algorithm (Ex: 3DES, Blowﬁsh,TwoFish)

• Ciphers
• Modes

• Ciphers
• Modes
• Determines how the key stream is used (never cross them)

• Ciphers
• Modes
• Avoid ECB (Electronic Code Book)

• Ciphers
• Modes
• (Use CBC or CFB, Cipher Block Chaining / Cipher FeedBack)

• Ciphers
• Modes
• InitializationVectors

• Ciphers
• Modes
• Similar to SALT in hashing (It’s not a secret)

• Ciphers
• Modes
• 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 CipherText.
Store it with your InitializationVector and CipherText.
When Decrypting:
Always verify signature ﬁrst, and then decrypt if matched.

Example: Using HMAC
$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
$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

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));

$cipher = $des->encrypt($message);
$hmac = bin2hex($hash->hash($cipher));
$verify_hmac = bin2hex($hash->hash($ciph
if ($verify_hmac == $hmac) {
$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.

•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.
•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

Questions?

JOHN CONGDON
PLEASE RATE ON JOIND.IN
https://joind.in/8179

JOHN CONGDON
•twitter: @johncongdon

JOHN CONGDON
•email: john@johncongdon.com

JOHN CONGDON
•email: john@johncongdon.com
•irc: freednode.net (#sdphp)

Encryption: It's For More Than Just Password - tek13

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