PHP equivalent of a Node encryption function - php

Question

I am trying to get a php equivalent of this node function to be able to encrypt some data in php before decrypting it in node
/**
* Encrypts an object with aes-256-cbc to use as a token
* #param {any} data An object to encrypt
* #param {string} secret The secret to encrypt the data with
* #returns {string}
*/
static encrypt(data, secret) {
const iv = randomBytes(16);
const cipher = createCipheriv('aes-256-cbc', secret, iv);
return `${cipher.update(JSON.stringify(data), 'utf8', 'base64') + cipher.final('base64')}.${iv.toString('base64')}`;
}
This is the php function I have come up with, along with the necessary helper functions
/**
* Encrypts an object with aes-256-cbc to use as a token
* #param $data An object to encrypt
* #param $secret The secret to encrypt data with
* #return \Illuminate\Http\Response
*/
public function encrypt($data, $secret)
{
$method = 'AES-256-CBC';
$data = static::getPaddedText($data);
$iv = static::generateIv();
$ciphertext = openssl_encrypt(json_encode($data), $method, $secret, OPENSSL_RAW_DATA, $iv);
$ciphertext_64 = base64_encode(utf8_encode($ciphertext));
$iv_64 = base64_encode($iv);
return "$ciphertext_64.$iv_64";
}
private static function getPaddedText(string $plainText): string
{
$blocksize = 8;
$textLength = strlen($plainText);
if ($textLength % $blocksize) {
$plainText = str_pad($plainText, $textLength + $blocksize - $textLength % $blocksize, "\0");
}
return $plainText;
}
public static function generateIv(): string
{
$ivLength = 16;
$success = false;
$random = openssl_random_pseudo_bytes($ivLength, $success);
if (!$success) {
$random = random_bytes($ivLength);
}
return $random;
}
But I dont think it is exactly the same as when decrypting it with this function
/**
* Decrypts an object with aes-256-cbc to use as a token
* #param {string} token An data to decrypt
* #param {string} secret The secret to decrypt the data with
* #returns {any}
*/
static decrypt(token, secret) {
const [data, iv] = token.split('.');
const decipher = createDecipheriv('aes-256-cbc', secret, Buffer.from(iv, 'base64'));
return JSON.parse(decipher.update(data, 'base64', 'utf8') + decipher.final('utf8'));
}
I get this error EVP_DecryptFinal_ex:wrong final block length

Answer 1

Looks like you aren't padding your text with nulls to ensure you have block sizes that are exactly eight characters long. In pother words, your string needs to be a multiple of eight in length. Padding your string with nulls will accomplish that for you without changing its value.
class AES256Encryption
{
public const BLOCK_SIZE = 8;
public const IV_LENGTH = 16;
public const CIPHER = 'AES-256-CBC';
public static function generateIv(): string
{
$success = false;
$random = openssl_random_pseudo_bytes(static::IV_LENGTH, $success);
if (!$success) {
$random = random_bytes(static::IV_LENGTH);
}
return $random;
}
private static function getPaddedText(string $plainText): string
{
$textLength = strlen($plainText);
if ($textLength % static::BLOCK_SIZE) {
$plainText = str_pad($plainText, $textLength + static::BLOCK_SIZE - $textLength % static::BLOCK_SIZE, "\0");
}
return $plainText;
}
public static function encrypt(string $plainText, string $key, string $iv): string
{
$plainText = static::getPaddedText($plainText);
return base64_encode(openssl_encrypt($plainText, static::CIPHER, $key, OPENSSL_RAW_DATA, $iv));
}
public static function decrypt(string $encryptedText, string $key, string $iv): string
{
return openssl_decrypt(base64_decode($encryptedText), static::CIPHER, $key, OPENSSL_RAW_DATA, $iv);
}
}
Usage:
$key = 'secretkey';
$iv = AES256Encryption::generateIv();
$text = 'The quick brown fox jumps over the lazy dog';
$encryptedText = AES256Encryption::encrypt($text, $key, $iv);
$decryptedText = AES256Encryption::decrypt($encryptedText, $key, $iv);
printf('Original Text: %s%s', $text, PHP_EOL);
printf('Encrypted : %s%s', $encryptedText, PHP_EOL);
printf('Decrypted : %s%s', $decryptedText, PHP_EOL);
Output:
Original Text: The quick brown fox jumps over the lazy dog
Encrypted : 1J+0tGHzn67WA7kJGjp9malmv0w+tcl0t8YnC+F9Y9IZWMDeBH4+k9TyuznF77cWe1SGUWa6Pb6r/i0xmH+ajg==
Decrypted : The quick brown fox jumps over the lazy dog
Your usage:
// Your encoding usage:
$key = 'secret';
$iv = AES256Encryption::generateIv();
$text = 'The quick brown fox jumps over the lazy dog';
$encryptedText = AES256Encryption::encrypt($text, $key, $iv);
$finalString = $encryptedText . bin2hex($iv);
// Your decoding usage:
$iv = hex2bin(substr($finalString, -32, 32));
$decryptedText = AES256Encryption::decrypt($encryptedText, $key, $iv);
printf('Original Text : %s%s', $text, PHP_EOL);
printf('Encrypted : %s%s', $encryptedText, PHP_EOL);
printf('Encrypted w/Iv: %s%s', $finalString, PHP_EOL);
printf('Decrypted : %s%s', $decryptedText, PHP_EOL);
Output:
Original Text : The quick brown fox jumps over the lazy dog
Encrypted : +JsjXFPdyTycYrc2fOb1edLKNksEUHzEGxwRewBlA8yxBWZZV2y/EVIwk0g9g17dtxAaTGZvYaf2y9+oTCvLWg==
Encrypted w/Iv: +JsjXFPdyTycYrc2fOb1edLKNksEUHzEGxwRewBlA8yxBWZZV2y/EVIwk0g9g17dtxAaTGZvYaf2y9+oTCvLWg==54993615360ff641a952a553e1500568
Decrypted : The quick brown fox jumps over the lazy dog
Generating the IV can be more robust as random_bytes() can throw an exception.