PHP encryption / decryption adding padded characters - php

Question

I'm trying to create a simple Encryption class but the resulting string is being padded with non-ascii characters. I've tried rtrim(), converting to utf8, etc. as mentioned in some other answers. What exactly am I missing? Here is what the characters show up when pasting the results into Notepad++
Pastebin containing the characters here. Appears as 't' in html, but copying that into notepad shows the random bits of data after it.
class Crypter implements ICrypter {
private $Key;
private $Algo;
public function __construct($Algo = MCRYPT_BLOWFISH) {
$this->Key = substr('key', 0, mcrypt_get_key_size($Algo, MCRYPT_MODE_ECB));
$this->Algo = $Algo;
}
public function Encrypt($data) {
//$iv_size = mcrypt_get_iv_size($this->Algo, MCRYPT_MODE_ECB);
//$iv = mcrypt_create_iv($iv_size, MCRYPT_RAND);
$blocksize = mcrypt_get_block_size('blowfish', 'ecb'); // get block size
$pkcs = $blocksize - (strlen($data) % $blocksize); // get pkcs5 pad length
$data.= str_repeat(chr($pkcs), $pkcs); // append pkcs5 padding to the data
$crypt = mcrypt_encrypt($this->Algo, $this->Key, $data, MCRYPT_MODE_ECB);
return rtrim(base64_encode($crypt));
}
public function Decrypt($data) {
$crypt = base64_decode($data);
$iv_size = mcrypt_get_iv_size($this->Algo, MCRYPT_MODE_ECB);
$iv = mcrypt_create_iv($iv_size, MCRYPT_RAND);
$decrypt = mcrypt_decrypt($this->Algo, $this->Key, $crypt, MCRYPT_MODE_ECB, $iv);
return rtrim($decrypt);
}
}

Answer 1

You need to handle the padding in the decryption same as the encryption. Here is a working example of your code:
<?php
class Crypter{
private $Key;
private $Algo;
public function __construct($Algo = MCRYPT_BLOWFISH) {
$this->Key = substr('key', 0, mcrypt_get_key_size($Algo, MCRYPT_MODE_ECB));
$this->Algo = $Algo;
}
public function Encrypt($data) {
//$iv_size = mcrypt_get_iv_size($this->Algo, MCRYPT_MODE_ECB);
//$iv = mcrypt_create_iv($iv_size, MCRYPT_RAND);
$blocksize = mcrypt_get_block_size('blowfish', 'ecb'); // get block size
$pkcs = $blocksize - (strlen($data) % $blocksize); // get pkcs5 pad length
$data.= str_repeat(chr($pkcs), $pkcs); // append pkcs5 padding to the data
$crypt = mcrypt_encrypt($this->Algo, $this->Key, $data, MCRYPT_MODE_ECB);
return rtrim(base64_encode($crypt));
}
public function Decrypt($data) {
$crypt = base64_decode($data);
$iv_size = mcrypt_get_iv_size($this->Algo, MCRYPT_MODE_ECB);
$iv = mcrypt_create_iv($iv_size, MCRYPT_RAND);
$decrypt = mcrypt_decrypt($this->Algo, $this->Key, $crypt, MCRYPT_MODE_ECB, $iv);
$block = mcrypt_get_block_size('blowfish', 'ecb');
$pad = ord($decrypt[($len = strlen($decrypt)) - 1]);
return substr($decrypt, 0, strlen($decrypt) - $pad);
}
}
$crypter = new Crypter();
$data = "Some data to encrypt";
$encryptedData = $crypter->Encrypt($data);
$decryptedData = $crypter->Decrypt($encryptedData);
echo "Decrypted Data = [$decryptedData]\n";
Notice the three lines I replaced your original Decrypt() return line with.