Node.js `crypto.final` make the encrypted result is different to PHP `mcrypt_encrypt`

Question

At first, Node.js crypto.

// Both of key and IV are hex-string, but I hide them in Stackoverflow.

var secretKey  = new Buffer('aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa', 'hex'), // 48 chars
    iv         = new Buffer('bbbbbbbbbbbbbbbb', 'hex'); // 16 chars
var str        = 'This string will be encrypted.';
var cipher     = crypto.createCipheriv('des-ede3-cbc', secretKey, iv),
    cryptedStr = cipher.update(str, 'utf8', 'base64') + cipher.final('base64');

Then, PHP mcrypt.

$key    = pack('H*', "aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa"); 
$iv     = pack('H*', "bbbbbbbbbbbbbbbb"); 
$string = 'This string will be encrypted.';
$text   = mcrypt_encrypt(MCRYPT_3DES, $key, $string, MCRYPT_MODE_CBC, $iv);
$text_base64 = base64_encode($text);

Problem.

In the same string, same algorithm and same encoding.

Still there is a little part not match that is cipher.final().

Below is the real sample output.

// Node.js output.
UKBI17EIHKNM2EU48ygsjil5r58Eo1csByAIFp9GhUw=
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
    Same part

// PHP output.
UKBI17EIHKNM2EU48ygsjil5r58Eo1csAY4C0JZoyco=
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
    Same part

Why cipher.final() make results different?

How could make the same results in Node.js on condition that don't modify PHP code.

The node.js example results in an error: http://runnable.com/VUcebtM0NhY3v9v5/output — Gergo Erdosi, May 04 '15 at 07:24
I see, I don't know how to make it visible. Anyway, the error is: "buffer.js:348 ret = this.parent.hexWrite(string, this.offset + offset, length); TypeError: Invalid hex string". — Gergo Erdosi, May 04 '15 at 07:31
@GergoErdosi, you right. I fixed it. Because previous article that I wrote the odd chars for Buffer. — Husky, May 04 '15 at 07:34
I dont know which is correct. But I must be follow the PHP result. I used Node.js to connect other people's PHP system. — Husky, May 04 '15 at 07:48
The problem is in the padding which I told you already in the previous question. — Artjom B., May 04 '15 at 08:34

Artjom B. · Accepted Answer · 2015-05-04T21:19:20.567

Since you can't change your PHP code, you will need to modify the node.js code.

The problem is that node.js' crypto module uses only PKCS#7 padding, whereas PHP uses only zero padding. You can however disable padding in node.js (setAutoPadding(false)) to implement your own zero padding:

function zeroPad(buf, blocksize){
    if (typeof buf === "string") {
        buf = new Buffer(buf, "utf8");
    }
    var pad = new Buffer((blocksize - (buf.length % blocksize)) % blocksize);
    pad.fill(0);
    return Buffer.concat([buf, pad]);
}

And use it like this:

var secretKey  = new Buffer('aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa', 'hex'), // 48 chars
    iv         = new Buffer('bbbbbbbbbbbbbbbb', 'hex'); // 16 chars
var str        = 'This string will be encrypted.';
var cipher     = crypto.createCipheriv('des-ede3-cbc', secretKey, iv);
cipher.setAutoPadding(false);

var cryptedStr = cipher.update(zeroPad(str, 8), 'utf8', 'base64') + cipher.final('base64');

console.log(cryptedStr);

Output:

UKBI17EIHKNM2EU48ygsjil5r58Eo1csAY4C0JZoyco=

Here is an implementation of a matching unpad function:

function zeroUnpad(buf, blocksize){
    var lastIndex = buf.length;
    while(lastIndex >= 0 && lastIndex > buf.length - blocksize - 1) {
        lastIndex--;
        if (buf[lastIndex] != 0) {
            break;
        }
    }
    return buf.slice(0, lastIndex + 1).toString("utf8");
}

return Buffer.concat([buf, new Buffer(Array((blocksize - (buf.length % blocksize)) % blocksize).join('00'), 'hex')]); — Husky, May 04 '15 at 21:02
This line `new Buffer(num)` , seem get the random output. So I make it be ('00', 'hex') — Husky, May 04 '15 at 21:04
Turns out the buffer needs to be filled. It is not guaranteed that it is filled with zero bytes. I changed for a clearer implementation. For some reason it worked the first time I tested this. I also added an unpad function — Artjom B., May 04 '15 at 21:20

Node.js `crypto.final` make the encrypted result is different to PHP `mcrypt_encrypt`

At first, Node.js crypto.

Then, PHP mcrypt.

Problem.

1 Answers1