---
url: /gst-manager-whmcs/features/file-integrity.md
description: >-
  How GST Manager verifies its own files with HMAC-SHA256 — the four issue
  types, the component breakdown, and the Sync Status panel with Auto-Sync, Sync
  All, and template sync to your themes.
---

# File Integrity

GST Manager maintains cryptographic verification of its installed files:

* **Tamper detection:** Validates module files against HMAC-SHA256 baselines.
* **Automated alerts:** Flags modified, missing, or unauthorized files under **Global Settings → Sync Status**.
* **Template management:** Syncs verified GST invoice templates to active WHMCS themes.

![GST Manager file-integrity and sync panel](/gst-manager-whmcs/img/gst-file-integrity-panel.png)
*Addons → GST Manager → Global Settings → Sync Status*

::: info How it works
Each module file is cryptographically hashed with an **HMAC-SHA256** signature. GST Manager detects unauthorized modifications to both file contents and internal signature records.
:::

## The four issue types

| Issue | Meaning |
| --- | --- |
| **Tampered** | File contents modified from the original release |
| **Missing** | Required module file is absent |
| **Added** | Unrecognized file detected in module directories |
| **HMAC Invalid** | Signature record mismatch indicating record-level tampering |

A clean system reports zero issues across all categories.

## The component breakdown

Files are audited and grouped by component:

| Component | What it covers |
| --- | --- |
| **Core** | Main application logic and business rules |
| **Templates** | GST invoice templates deployed to WHMCS themes |
| **Hooks** | WHMCS event listeners and workflow hooks |
| **Main** | Module entry point and bootstrap files |

The panel records the **last snapshot time**, created on activation and refreshed after every sync.

## The Sync Status panel

Manage theme templates and synchronization under **Global Settings → Sync Status**:

* **Auto-Sync:** Redeploys templates automatically if mismatches are detected during admin page loads.
* **Theme Sync Status table:** Displays sync status for `invoicepdf.tpl` and `invoicepdffooter.tpl` per theme.
* **Sync All:** Overwrites and redeploys verified templates across all installed themes.

Successful operations return *"Templates synced successfully."*

::: tip Keep your active theme in sync
WHMCS theme updates can overwrite custom template files. Keep Auto-Sync enabled or trigger **Sync All** after theme updates to maintain PDF invoice layout integrity.
:::

## Where to go next

* [Setup Wizard](/gst-manager-whmcs/features/setup-wizard) — Step 7 deploys the templates
* [Configuration](/gst-manager-whmcs/configuration) — where templates and settings live
* Back to the [overview](/gst-manager-whmcs/)