Configuration and Secrets Management

Relevant source files

The following files were used as context for generating this wiki page:

• Program.cs
• DEPLOY-GCLOUD.md
• Data/ApplicationDbContext.cs
• Services/OpenAIService.cs
• Controllers/ExamAppController.cs
• PeP.ExamApp/Installer/README.md
• Models/ExamModels.cs
• deploy-gcloud.ps1

The PeP5 application employs a multi-layered configuration strategy to manage settings and secrets across different environments. This approach combines standard ASP.NET Core configuration providers (like appsettings.json), environment-specific files, a database-driven model for dynamic platform settings, and Google Cloud Secret Manager for secure handling of production secrets.

This document outlines the architecture of configuration and secrets management, from application startup and local development to production deployment on Google Cloud. It covers how connection strings, API keys, and other application settings are loaded and accessed by various services.

Configuration Loading

The application's configuration is loaded at startup in Program.cs. It follows the standard ASP.NET Core hierarchical model, where settings from later providers override earlier ones.

The diagram below illustrates the flow of how configuration sources are loaded and prioritized.

Database Connection

The primary database connection string is retrieved from the DefaultConnection key within the ConnectionStrings section of the configuration. This is used to register the ApplicationDbContext.

Sources: Program.cs:10-11

Production Deployment & Secrets

For production environments, the application is designed to be deployed on Google Cloud Platform (GCP) using Cloud Run and Cloud SQL. Sensitive information, particularly the database connection string, is managed using Google Cloud Secret Manager.

Google Cloud Secret Management

The deployment guide specifies a secure method for handling the database connection string:

1. A secret is created in Google Cloud Secret Manager to store the connection string.
2. The Cloud Run service is granted IAM permissions (roles/secretmanager.secretAccessor) to access this secret.
3. The secret is mounted into the Cloud Run service instance as an environment variable (ConnectionStrings__DefaultConnection). This maps the secret's value to the configuration key the application expects.

The diagram below shows the interaction between services in a production environment.

The deployment script (deploy-gcloud.ps1) also facilitates this process by setting up the necessary GCP services and configurations.
Sources: deploy-gcloud.ps1

Production Environment Variables

The following environment variables are configured for the Cloud Run service:

Variable	Description	Source
ConnectionStrings__DefaultConnection	The SQL Server connection string, sourced from Secret Manager.	DEPLOY-GCLOUD.md:65, DEPLOY-GCLOUD.md:80-82
ASPNETCORE_ENVIRONMENT	Set to Production to enable production-specific behaviors.	DEPLOY-GCLOUD.md:80-82
ExamAppUpdate__DownloadUrl	The public URL for downloading the ExamApp installer, typically hosted on Cloud Storage.	DEPLOY-GCLOUD.md:80-82

Sources: DEPLOY-GCLOUD.md:80-82

Application-Level Configuration

In addition to environment-based configuration, PeP5 uses two other mechanisms for managing settings: a database table for platform-wide settings and a dedicated configuration section for the desktop client.

Platform Settings

A PlatformSetting entity allows for dynamic configuration values to be stored and managed in the database. This is ideal for settings that may need to be changed by an administrator without redeploying the application, such as API keys or feature flags.

Data Model

The PlatformSetting model is defined in Models/ExamModels.cs and consists of a key-value pair with an optional description.

Default Settings

On application startup, the database is seeded with a set of default platform settings. This ensures that the application has the necessary configuration keys available from the first run.

Key	Default Value	Description
PlatformName	PeP - Programming Examination Platform	The name of the platform displayed in the UI.
Version	5.0	The current version of the web application.
Company	Infinity Atom	The company name.
Copyright	Copyright 2021 - 2025	The copyright notice.
OpenAIApiKey	"" (empty string)	The API key for the OpenAI service. Must be configured by an admin.
DefaultExamDurationMinutes	120	Default exam duration in minutes.
EmailServer	"" (empty string)	SMTP server for sending emails.
EmailPort	587	Port for the SMTP server.
EmailUsername	"" (empty string)	Username for the SMTP server.
EmailPassword	"" (empty string)	Password for the SMTP server.

Sources: Data/ApplicationDbContext.cs:176-187

Usage Example: OpenAI Service

The OpenAIService demonstrates how these database-driven settings are used. It retrieves the OpenAIApiKey and OpenAIModel from the PlatformSettings table to initialize the OpenAI client. This decouples the service from IConfiguration and allows the API key to be updated in the database at runtime.

// File: Services/OpenAIService.cs:91-95
var apiKeySetting = await _context.PlatformSettings.FirstOrDefaultAsync(s => s.Key == "OpenAIApiKey");
var apiKey = apiKeySetting?.Value;
if (string.IsNullOrWhiteSpace(apiKey))
{
    throw new InvalidOperationException("OpenAI API key is not configured in Platform Settings.");
}

Sources: Services/OpenAIService.cs:91-99, Services/OpenAIService.cs:260-269

Exam App Update Configuration

The configuration for the PeP.ExamApp desktop client auto-updater is managed via the ExamAppUpdate section in appsettings.json. This information is exposed through an API endpoint.

Configuration Structure

The ExamAppUpdate section has the following structure:

Key	Type	Description
Version	string	The latest available version of the Exam App.
DownloadUrl	string	The direct URL to the installer executable.
ReleaseNotes	string	Notes for the new version, displayed to the user.
ReleaseDate	DateTime	The date the update was released.
IsMandatory	bool	If true, the user is forced to update.
MinimumVersion	string	The minimum version required to run the app.
Checksum	string	The SHA256 checksum of the installer file for verification.

Sources: PeP.ExamApp/Installer/README.md:92-102

API Endpoint

The ExamAppController provides an endpoint at GET /api/exam-app/update that reads this configuration section and returns it as a JSON response to the desktop client.

The following sequence diagram shows the update check process.

Summary

PeP5's configuration system is robust and secure, adapting to different operational environments. It uses appsettings.json for base configuration, Google Cloud Secret Manager for production secrets, and a PlatformSettings database table for dynamic, administrator-managed values. This layered approach ensures that sensitive data is protected while providing flexibility for both developers and administrators.