Porting python aes ecb to php openssl

Question

I have python code

from Crypto.Cipher import AES


def pad(data):
    block_size = 16
    bytes_to_add = block_size - ((len(data) % block_size) or block_size)
    return data + (b'\0' * bytes_to_add)


cipher = AES.new(b"4452038393672345", AES.MODE_ECB)
body = pad("asa masa".encode('utf-8'))
content = base64.b64encode(cipher.encrypt(body)).decode('ascii')

I see result "sEP5RCWmdQdPYo/eeWVIwg=="

I want to port python code to php using openssl

function pad($data) {
  $block_size = 16;
  $bytes_to_add = $block_size - ((strlen($data) % $block_size) ?: $block_size);
  return $data . str_repeat("\0", $bytes_to_add);
}


$cipher = "AES-128-ECB";
$options = OPENSSL_RAW_DATA;
$plainText = pad("asa masa");
$key = '4452038393672345';
$encryptedText = openssl_encrypt($plainText, $cipher, $key, $options);
$encodedText = base64_encode($encryptedText);

I see result from openssl "c0VQNVJDV21kUWRQWW8vZWVXVkl3dWZPTjExZ21iUG1VQUI0c0EwaktVaz0="

Another code in php

$rawData = openssl_encrypt(pad("asa masa"), 'AES-128-ECB', '4452038393672345');

return "sEP5RCWmdQdPYo/eeWVIwufON11gmbPmUAB4sA0jKUk="

If anyone is interested, do it this way and everything is fine

If anyone is interested, do it this way and everything is fine
$encrypted = openssl_encrypt(pad("asa masa"), 'AES-128-ECB', '4452038393672345',OPENSSL_RAW_DATA | OPENSSL_DONT_ZERO_PAD_KEY | OPENSSL_ZERO_PADDING);
$encrypted=base64_encode($encrypted);

Result is "sEP5RCWmdQdPYo/eeWVIwg=="

Thanks

Answer 1

if we refer to https://www.php.net/manual/en/function.openssl-encrypt.php

options is a bitwise disjunction of the flags OPENSSL_RAW_DATA and OPENSSL_ZERO_PADDING.

OPENSSL_RAW_DATA = 1 (binary: 01) OPENSSL_ZERO_PADDING = 2 (binary: 10)

so:

base64_encode(openssl_encrypt($plainText, $cipher, $key, 0)); // 00 = no flags
c0VQNVJDV21kUWRQWW8vZWVXVkl3dWZPTjExZ21iUG1VQUI0c0EwaktVaz0=

base64_encode(openssl_encrypt($plainText, $cipher, $key, 1)); // 01 = OPENSSL_RAW_DATA
sEP5RCWmdQdPYo/eeWVIwufON11gmbPmUAB4sA0jKUk=

base64_encode(openssl_encrypt($plainText, $cipher, $key, 2)); // 10 = OPENSSL_ZERO_PADDING
c0VQNVJDV21kUWRQWW8vZWVXVkl3Zz09

base64_encode(openssl_encrypt($plainText, $cipher, $key, 3)); // 11 = OPENSSL_RAW_DATA | OPENSSL_ZERO_PADDING
sEP5RCWmdQdPYo/eeWVIwg==

and the pattern repeats since we're only looking for last 2 bits

base64_encode(openssl_encrypt($plainText, $cipher, $key, 4)); // (1)00
c0VQNVJDV21kUWRQWW8vZWVXVkl3dWZPTjExZ21iUG1VQUI0c0EwaktVaz0=

base64_encode(openssl_encrypt($plainText, $cipher, $key, 5)); // (1)01
sEP5RCWmdQdPYo/eeWVIwufON11gmbPmUAB4sA0jKUk=

base64_encode(openssl_encrypt($plainText, $cipher, $key, 6)); // (1)10
c0VQNVJDV21kUWRQWW8vZWVXVkl3Zz09

base64_encode(openssl_encrypt($plainText, $cipher, $key, 7)); // (1)11
sEP5RCWmdQdPYo/eeWVIwg==

OPENSSL_RAW_DATA | OPENSSL_DONT_ZERO_PAD_KEY | OPENSSL_ZERO_PADDING = 1 | 4 | 2 = 7 so we get openssl_encrypt($plainText, $cipher, $key, 7)

by default openssl_encrypt uses PKCS#7 padding which causes "double padding" (your zero pad + PKCS) that's why in you should use OPENSSL_ZERO_PADDING in your case (it's recommended to use default openssl_encrypt padding)

if you visit https://www.base64decode.org/ you can see that c0VQNVJDV21kUWRQWW8vZWVXVkl3dWZPTjExZ21iUG1VQUI0c0EwaktVaz0= is base64 encoded sEP5RCWmdQdPYo/eeWVIwufON11gmbPmUAB4sA0jKUk= and sEP5RCWmdQdPYo/eeWVIwufON11gmbPmUAB4sA0jKUk= is just sEP5RCWmdQdPYo/eeWVIwg== with some additional stuff caused by double padding