Read this when changing configuration encoding, runtime loading, backup behavior, or administrator configuration access.

# Encoded Configuration Files

## Implementing Files

| File | Key symbols |
|---|---|
| `index.php` | `LoadEncryptedConfig('cfg/config.bin')` during bootstrap |
| `src/Core/System/RuntimeServices.php` | `LoadEncryptedConfig`, `Encrypt`, `Decrypt` |
| `src/Core/Api/AdminController.php` | Admin read/save and backup restoration |
| `cfg/config.ini.example` | Tracked placeholder template for local configuration |
| `cfg/config.ini` | Ignored local plaintext configuration, potentially containing credentials |

## Flow
1. Bootstrap checks the PHP version and asks `RuntimeServices` to load `cfg/config.bin`.
2. The utility decodes it to a temporary file, calls F3 `config()`, then deletes the temporary file.
3. Deployment tooling provisions `cfg/config.bin` before bootstrap; no configuration-generation script is tracked.
4. An administrator can read plaintext through the API or submit replacement text.
5. Save renames the prior runtime config to `.old`, writes the encoded replacement, and restores the backup if writing fails.

## Trust Boundaries

| Boundary | Mechanism | Location |
|---|---|---|
| Runtime config presence | Bootstrap throws when the required file is absent | `RuntimeServices::LoadEncryptedConfig()` |
| Sensitive config disclosure | Numeric permission ID `1` required before reading plaintext | `AdminController::load()` |
| Sensitive config mutation | Numeric permission ID `1` and CSRF validation required | `AdminController::save()` |
| Partial replacement failure | Backup rename and restore attempt after write failure | `AdminController::saveConfiguration()` |
| Local config source | Placeholder template is copied to an ignored local file | `cfg/config.ini.example` |

## Config
- Runtime file: `cfg/config.bin`.
- Backup file: `cfg/config.bin.old`.
- Encoding: `base64_encode(gzcompress())`; decoding is `gzuncompress(base64_decode())`.
- The encoding is reversible; it is not a confidentiality mechanism.

See [configuration spec](../configuration/spec.md) and [commands](../commands.md).