PHP: How to convert UUID to bytes?

Question

So in this project I'm working on I'm currently trying to do a reset-password function which generates a URL which is then given to the user with a secret attached to it to be validated in the backend.

The problem is that the secret needs to be stored in the db (postgresql) in a bytea format. Is there a way to convert a UUID to a bytea format in php? I've tried some different variations of pack and unpack as well as a few functions I found on the interwebs but with no success.

I'm not allowed to alter the db in any way.

Why does it need to be stored in byte format? What difference does it make? — Starx, Mar 21 '18 at 15:13
Because the feature I'm doing is pretty much a way for devs to help a user out by sending them this reset password url, and if it's stored in a wrong format the url sent to the user doesn't actually work. — Johan Lundgren, Mar 21 '18 at 15:17
@Starx not certain for postgres, but i believe that byte-format speeds up indexing and query by UUID. — YvesLeBorg, Mar 21 '18 at 15:17
@YvesLeBorg, Based on the response from OP, I don't think that is what he is after. — Starx, Mar 21 '18 at 15:19
Can you show your implementation of pack? and Why the result is not what you are looking for? — Starx, Mar 21 '18 at 15:19
Possible duplicate: https://stackoverflow.com/a/2484315/1461181 — odan, Mar 21 '18 at 15:20
@YvesLeBorg, :) I didn't know the indexing thing BTW. Thank you :) — Starx, Mar 21 '18 at 15:20
Well the variations I've tried so far (that I remember) is: $dbToken = hex2bin(str_replace("-", "", $token)); $dbToken = pack("H*", str_replace("-", "", $token)); $db = str_replace("-", "", $token); $dbToken = hex2bin($db); — Johan Lundgren, Mar 21 '18 at 15:21

score 4 · Answer 1 · answered Mar 21 '18 at 15:24

4

You can get the bytes from a Ramsey\Uuid\Uuid object like this:

$uuid = \Ramsey\Uuid\Uuid::uuid4();
$bytes = $uuid->getBytes();

answered Mar 21 '18 at 15:24

odan

4,757
5
20
49

true, but that lib loads a truckload of classes and dependancies. I walked away from it. – YvesLeBorg Mar 21 '18 at 15:25
@YvesLeBorg, Which library do you use? – Starx Mar 21 '18 at 15:28
@Starx `openssl_random_pseudo_bytes(16)` , edited my answer. Slick and fastest, lots of benchmarking done. – YvesLeBorg Mar 21 '18 at 15:32

YvesLeBorg · Answer 2 · 2018-03-21T15:32:27.713

FWIW, this is what i do (MySQL context):

/**
 *
 * pack with H* to ensure compatibility with MySQL function UNHEX.
 *
 * @param string $stringGuid
 *
 * @return string 16 bytes long
 *
 * @ref https://stackoverflow.com/questions/2839037/php-mysql-storing-and-retrieving-uuids
 */
function stringGuidAsBinaryGuid($stringGuid)
{
    $binary = pack("H*" , str_replace('-' , '' , $stringGuid));
    return $binary;
}

function binaryGuidAsStringGuid($binaryGuid)
{
    $string = unpack("H*" , $binaryGuid);
    $string = preg_replace(
        "/([0-9a-f]{8})([0-9a-f]{4})([0-9a-f]{4})([0-9a-f]{4})([0-9a-f]{12})/" ,
        "$1-$2-$3-$4-$5" ,
        $string["1"]
    );
    return $string;
}

/***
 *
 * returns a valid GUID, v4 (string, 36 bytes)
 *
 * @link http://php.net/manual/en/function.com-create-guid.php
 *
 * @return string
 *
 */
function GUID()
{

    // prefer strong crypto variant

    if (function_exists('openssl_random_pseudo_bytes') === true) {
        $data    = openssl_random_pseudo_bytes(16);
        $data[6] = chr(ord($data[6]) & 0x0f | 0x40);    // set version to 0100
        $data[8] = chr(ord($data[8]) & 0x3f | 0x80);    // set bits 6-7 to 10
        return vsprintf('%s%s-%s-%s-%s-%s%s%s' , str_split(bin2hex($data) , 4));
    }

    return sprintf(
        '%04X%04X-%04X-%04X-%04X-%04X%04X%04X' ,
        mt_rand(0 , 65535) ,
        mt_rand(0 , 65535) ,
        mt_rand(0 , 65535) ,
        mt_rand(16384 , 20479) ,
        mt_rand(32768 , 49151) ,
        mt_rand(0 , 65535) ,
        mt_rand(0 , 65535) ,
        mt_rand(0 , 65535)
    );

}

PHP: How to convert UUID to bytes?

2 Answers2