fix(security): whitelist and validate invoice template types (#4393)

- Add whitelist validation for invoice_type to prevent path traversal and LFI
- Validate invoice_type against allowed values in Sale_lib
- Sanitize invoice_type input in Config controller before saving
- Default to 'invoice' template for invalid types

Security: Prevents arbitrary file inclusion via user-controlled invoice_type config

app/Controllers/Config.php

@@ -942,7 +942,9 @@ class Config extends Secure_Controller
             'work_order_enable'           => $this->request->getPost('work_order_enable') != null,
             'work_order_format'           => $this->request->getPost('work_order_format'),
             'last_used_work_order_number' => $this->request->getPost('last_used_work_order_number', FILTER_SANITIZE_NUMBER_INT),
-            'invoice_type'                => $this->request->getPost('invoice_type')
+            'invoice_type'                => Sale_lib::isValidInvoiceType($this->request->getPost('invoice_type')) 
+                ? $this->request->getPost('invoice_type') 
+                : 'invoice'
         ];
 
         $success = $this->appconfig->batch_save($batch_save_data);

app/Controllers/Sales.php

@@ -755,8 +755,11 @@ class Sales extends Secure_Controller
                 $data['sale_status'] = COMPLETED;
                 $sale_type = SALE_TYPE_INVOICE;
 
-                // The PHP file name is the same as the invoice_type key
-                $invoice_view = $this->config['invoice_type'];
+                $invoice_type = $this->config['invoice_type'];
+                if (!Sale_lib::isValidInvoiceType($invoice_type)) {
+                    $invoice_type = 'invoice';
+                }
+                $invoice_view = $invoice_type;
 
                 // Save the data to the sales table
                 $data['sale_id_num'] = $this->sale->save_value($sale_id, $data['sale_status'], $data['cart'], $customer_id, $employee_id, $data['comments'], $invoice_number, $work_order_number, $quote_number, $sale_type, $data['payments'], $data['dinner_table'], $tax_details);
@@ -1107,6 +1110,9 @@ class Sales extends Secure_Controller
         }
 
         $invoice_type = $this->config['invoice_type'];
+        if (!Sale_lib::isValidInvoiceType($invoice_type)) {
+            $invoice_type = 'invoice';
+        }
         $data['invoice_view'] = $invoice_type;
 
         return $data;

app/Libraries/Sale_lib.php

@@ -88,9 +88,13 @@ class Sale_lib
         return $register_modes;
     }
 
-    /**
-     * @return array
-     */
+    private const ALLOWED_INVOICE_TYPES = [
+        'invoice',
+        'tax_invoice',
+        'custom_invoice',
+        'custom_tax_invoice'
+    ];
+
     public function get_invoice_type_options(): array
     {
         $invoice_types = [];
@@ -101,6 +105,11 @@ class Sale_lib
         return $invoice_types;
     }
 
+    public static function isValidInvoiceType(string $invoice_type): bool
+    {
+        return in_array($invoice_type, self::ALLOWED_INVOICE_TYPES, true);
+    }
+
     /**
      * @return array
      */