AES-256-CFB Stream

AESStreamFilter.php

<?php
/**
 * Created by IntelliJ IDEA.
 * User: xts
 * Date: 15/5/20
 * Time: 10:05PM
 */
 
 namespace xts;

class AESStreamFilter {
    private $key;
    private $iv;
    private $tail = '';
    private $isDecrypt;

    public function __construct($key, $iv, $isDecrypt=false) {
        $this->key = $key;
        $this->iv = $iv;
        $this->isDecrypt = $isDecrypt;
    }
    public function filter($data) {
        if (strlen($data) == 0)
            return '';
        $tl = strlen($this->tail);
        if ($tl)
            $data = $this->tail . $data;
        if ($this->isDecrypt)
            $b = openssl_decrypt($data, 'aes-256-cfb', $this->key, OPENSSL_RAW_DATA, $this->iv);
        else
            $b = openssl_encrypt($data, 'aes-256-cfb', $this->key, OPENSSL_RAW_DATA, $this->iv);
        $result = substr($b, $tl);
        $dataLength = strlen($data);
        $mod16 = $dataLength%16;
        if ($dataLength >= 16) {
          $iPos = -($mod16 + 16);
          if ($this->isDecrypt)
              $this->iv = substr($data, $iPos, 16);
          else
              $this->iv = substr($b, $iPos, 16);
        }
        $this->tail = $mod16!=0 ? substr($data, -$mod16):'';
        return $result;
    }
}

// Example
$dataToEncrypt = array(
  'Shadowsocks is ',
  'a secure socks5 proxy, designed to protect your Internet traffic. ',
  'Aa ',
  '我是中文汉字',
  'bB ',
);

$key = openssl_random_pseudo_bytes(32); // 256bit Key Length
$iv  = openssl_random_pseudo_bytes(16); // 128bit AES Block Length

$enc = new AESStreamFilter($key, $iv);

$crypto = '';
foreach ($dataToEncrypt as $data) {
  $crypto .= $enc->filter($data);
}

echo openssl_decrypt($crypto, 'aes-256-cfb', $key, OPENSSL_RAW_DATA, $iv), "\n";

$text = 'This is a test for my aes-256-cfb stream program with some 中文字符.';
$crypto = openssl_encrypt($text, 'aes-256-cfb', $key, OPENSSL_RAW_DATA, $iv);
$parts[] = substr($crypto, 0, 7);
$parts[] = substr($crypto, 7, 8);
$parts[] = substr($crypto, 15, 17);
$parts[] = substr($crypto, 32, 2);
$parts[] = substr($crypto, 34, 12);
$parts[] = substr($crypto, 46);

$dec = new AESStreamFilter($key, $iv, true);
$text = '';
foreach ($parts as $part) {
  $text .= $dec->filter($part);
}
echo $text, "\n";