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Security: MichalisKat/MySchoolChecks

Security

SECURITY.md

Security & Credential Management — MySchool Checks

This document is intended for Microsoft Store submission reviewers, security auditors, and developers contributing to the project.
Repository: https://github.com/MichalisKat/myschool-checks

Overview

MySchool Checks authenticates to the Greek Ministry of Education's e-myschool.gr portal and sends automated email notifications via SMTP. This requires storing user credentials securely on the end user's machine.

As of v2.0, the application stores NO credentials in plain text. All sensitive data is protected using the operating system's native secure credential store.

Credential Storage Architecture

What is stored — and where

Credential Storage Location Plain text?
MySchool username (ΑΜ) Windows Credential Manager ✗ Encrypted
MySchool password Windows Credential Manager ✗ Encrypted
Email (SMTP) password Windows Credential Manager ✗ Encrypted
FROM_EMAIL (display) local_settings.json ✓ Non-sensitive
FROM_NAME local_settings.json ✓ Non-sensitive
SMTP_HOST / SMTP_PORT local_settings.json ✓ Non-sensitive

Windows Credential Manager (DPAPI)

On Windows, the application uses the keyring library, which stores credentials in the Windows Credential Manager via the Data Protection API (DPAPI).

  • Credentials are encrypted with a key derived from the user's Windows login credentials.
  • No third-party encryption library is used — this is native OS functionality.
  • Credentials are accessible only to the user account that stored them.
  • Credentials survive application reinstallation (they live in the OS, not the app folder).

Registry path (Windows): Control Panel\User Accounts\Credential Manager → Windows Credentials → entry named MySchoolChecksPlus

The local_settings.json file

The configuration file at %LOCALAPPDATA%\MySchoolChecksPlus\data\local_settings.json contains only non-sensitive settings such as display name, email address, and SMTP server hostname. No passwords or authentication tokens are stored here.

Example of a clean (post-migration) local_settings.json:

{
  "FROM_NAME": "Σχολείο ΔΠΕ",
  "FROM_EMAIL": "itdipea@sch.gr",
  "SMTP_HOST": "mail.sch.gr",
  "SMTP_PORT": 587
}

First-Time Setup Flow

When a user installs the application for the first time:

  1. The application checks Windows Credential Manager for stored credentials via encryption.credentials_exist().
  2. If credentials are missing, the user is prompted to enter them via setup_credentials.py (or the built-in setup wizard).
  3. Credentials are stored in Windows Credential Manager via keyring.set_password().
  4. The application never writes passwords to disk at any point in this flow.

For users upgrading from an older version that stored credentials in local_settings.json, the setup_credentials.py --migrate command performs a one-time migration:

  • Reads credentials from the old JSON file.
  • Stores them in Windows Credential Manager.
  • Removes the sensitive fields from the JSON file.
  • Creates a local_settings.json.bak backup.

Microsoft Store Compliance

This application complies with Microsoft Store policies regarding credential and data handling:

Policy requirement How we comply
No plain-text passwords in files or registry Credentials stored exclusively in Windows Credential Manager (DPAPI)
Use of OS-native security APIs keyring library delegates to Windows Credential Manager, not a custom crypto implementation
User data isolation DPAPI encrypts per-user; no other user or process can read the credentials
Transparent data handling This document and in-app messages explain exactly what is stored and where
No credential exfiltration Credentials are read only for MySchool portal login and SMTP auth; no telemetry or remote transmission

Relevant Source Files

File Purpose
encryption.py Core credential store/retrieve/delete/migrate functions
setup_credentials.py First-time setup wizard; also handles migration from legacy JSON
main_credentials_integration.py Integration guide showing how main.py loads credentials from keyring

Dependencies

keyring>=24.0.0

The keyring library is a well-maintained, MIT-licensed Python package with 5M+ weekly downloads. On Windows it uses pywin32 under the hood to interface with the native Credential Manager API.

PyPI: https://pypi.org/project/keyring/
Source: https://github.com/jaraco/keyring

Threat Model

Threat Mitigation
Attacker reads local_settings.json File contains no credentials — only public configuration values
Attacker reads app source / decompiles executable Source contains no credentials — credentials are read at runtime from OS keychain
Attacker with physical access to the machine Same access as any app using Windows Credential Manager; mitigated by OS-level user login security
Credential leak via logs encryption.py uses Python logging module; credential values are never logged

Contact

For security disclosures or questions, contact the maintainer via the GitHub repository.

There aren't any published security advisories