How to pass encrypted string in GET request in php? - php

Question

I am encrypting a string using following class (using inheritance)
class UnsafeCrypto {
const METHOD = 'aes-256-ctr';
/**
* Encrypts (but does not authenticate) a message
*
* #param string $message - plaintext message
* #param string $key - encryption key (raw binary expected)
* #param boolean $encode - set to TRUE to return a base64-encoded
* #return string (raw binary)
*/
public static function encrypt($message, $key, $encode = false)
{
$nonceSize = openssl_cipher_iv_length(self::METHOD);
$nonce = openssl_random_pseudo_bytes($nonceSize);
$ciphertext = openssl_encrypt(
$message,
self::METHOD,
$key,
OPENSSL_RAW_DATA,
$nonce
);
// Now let's pack the IV and the ciphertext together
// Naively, we can just concatenate
if ($encode) {
return base64_encode($nonce.$ciphertext);
}
return $nonce.$ciphertext;
}
/**
* Decrypts (but does not verify) a message
*
* #param string $message - ciphertext message
* #param string $key - encryption key (raw binary expected)
* #param boolean $encoded - are we expecting an encoded string?
* #return string
*/
public static function decrypt($message, $key, $encoded = false)
{
if ($encoded) {
$message = base64_decode($message, true);
if ($message === false) {
throw new Exception('Encryption failure');
}
}
$nonceSize = openssl_cipher_iv_length(self::METHOD);
$nonce = mb_substr($message, 0, $nonceSize, '8bit');
$ciphertext = mb_substr($message, $nonceSize, null, '8bit');
$plaintext = openssl_decrypt(
$ciphertext,
self::METHOD,
$key,
OPENSSL_RAW_DATA,
$nonce
);
return $plaintext;
}
}
Inheriting the class as below.
class SaferCrypto extends UnsafeCrypto {
const HASH_ALGO = 'sha256';
/**
* Encrypts then MACs a message
*
* #param string $message - plaintext message
* #param string $key - encryption key (raw binary expected)
* #param boolean $encode - set to TRUE to return a base64-encoded string
* #return string (raw binary)
*/
public static function encrypt($message, $key, $encode = false)
{
list($encKey, $authKey) = self::splitKeys($key);
// Pass to UnsafeCrypto::encrypt
$ciphertext = parent::encrypt($message, $encKey);
// Calculate a MAC of the IV and ciphertext
$mac = hash_hmac(self::HASH_ALGO, $ciphertext, $authKey, true);
if ($encode) {
return base64_encode($mac.$ciphertext);
}
// Prepend MAC to the ciphertext and return to caller
return $mac.$ciphertext;
}
/**
* Decrypts a message (after verifying integrity)
*
* #param string $message - ciphertext message
* #param string $key - encryption key (raw binary expected)
* #param boolean $encoded - are we expecting an encoded string?
* #return string (raw binary)
*/
public static function decrypt($message, $key, $encoded = false)
{
list($encKey, $authKey) = self::splitKeys($key);
if ($encoded) {
$message = base64_decode($message, true);
if ($message === false) {
throw new Exception('Encryption failure');
}
}
// Hash Size -- in case HASH_ALGO is changed
$hs = mb_strlen(hash(self::HASH_ALGO, '', true), '8bit');
$mac = mb_substr($message, 0, $hs, '8bit');
$ciphertext = mb_substr($message, $hs, null, '8bit');
$calculated = hash_hmac(
self::HASH_ALGO,
$ciphertext,
$authKey,
true
);
if (!self::hashEquals($mac, $calculated)) {
throw new Exception('Encryption failure');
}
// Pass to UnsafeCrypto::decrypt
$plaintext = parent::decrypt($ciphertext, $encKey);
return $plaintext;
}
/**
* Splits a key into two separate keys; one for encryption
* and the other for authenticaiton
*
* #param string $masterKey (raw binary)
* #return array (two raw binary strings)
*/
protected static function splitKeys($masterKey)
{
// You really want to implement HKDF here instead!
return [
hash_hmac(self::HASH_ALGO, 'ENCRYPTION', $masterKey, true),
hash_hmac(self::HASH_ALGO, 'AUTHENTICATION', $masterKey, true)
];
}
/**
* Compare two strings without leaking timing information
*
* #param string $a
* #param string $b
* #ref https://paragonie.com/b/WS1DLx6BnpsdaVQW
* #return boolean
*/
protected static function hashEquals($a, $b)
{
if (function_exists('hash_equals')) {
return hash_equals($a, $b);
}
$nonce = openssl_random_pseudo_bytes(32);
return hash_hmac(self::HASH_ALGO, $a, $nonce) === hash_hmac(self::HASH_ALGO, $b, $nonce);
}
}
Encrypting string as follow.
$email = 'myemail#domain.com';
$key = 'Some key';
$encrypted_email = $encrypted = SaferCrypto::encrypt($message, $key);
String is getting encrypted like this:
óÜCu!>Ò·<x0½“—J ‡l¿Ø ;ƒ;›OøVP#ï 1 Sjñ,(ñúrÛòv–~ºyÍg ÷–´´iƒû
If I pass this with urlencode($string) data is not getting decrypted because hash is not matching because hashEquals method is throwing exception.
What is the proper way to pass encrypted string in GET request?

Answer 1

It's not clear, what is the problem, but you can use base64_encode($encrypted_email) to pass your string as smth like HDo1FaXabDHjfxBkpx7YBHNGVeZ/G8FvI2BoxES2rUu3lvNWRo5G0PImiv9IhENv.
link
When receiving, decode it
$encrypted_email = base64_decode($_GET['enc']);