PHP switch from MCRYPT_MODE_ECB to AES-256-ECB

Question

I am rewriting code to be compatible with PHP 7.2. Old code is

public function encryptPasswordOld($password, $salt)
{
    $key = md5($salt);
    $result = mcrypt_encrypt(MCRYPT_RIJNDAEL_128, $key, $password, MCRYPT_MODE_ECB);
    return base64_encode($result);
}

New code should be according to my research something like this

public function encryptPasswordNew($password, $salt)
{
    $method = 'AES-256-ECB';
    $ivSize = openssl_cipher_iv_length($method);
    $iv = openssl_random_pseudo_bytes($ivSize);
    $key = md5($salt);
    $result = openssl_encrypt($password, $method, $key, OPENSSL_RAW_DATA, $iv);
    return base64_encode($result);
}

but I tried every combination of openssl_encrypt options: OPENSSL_RAW_DATA , OPENSSL_RAW_DATA | OPENSSL_ZERO_PADDING OPENSSL_RAW_DATA | OPENSSL_ZERO_PADDING , OPENSSL_ZERO_PADDING , 0 and still ended up with different result as the old method returns

Answer 1

try to use pkcs5padding on value before encrypt. ie

remember the blocksize should be 8-byte based, ie 8/16/24 etc.

function pkcs5_pad($text, $blocksize)
{
    $pad = $blocksize - (strlen($text) % $blocksize);
    return $text . str_repeat(chr(0), $pad);
}

and encrypt option should be OPENSSL_RAW_DATA | OPENSSL_ZERO_PADDING, ie

openssl_encrypt(pkcs5_pad($value, 16), 'aes-256-ecb', $aes_key, 3, '')