Add authentication and improve server side configuration

RemoteExec.Server/Middleware/ApiKeyAuthenticationMiddleware.cs

@@ -0,0 +1,123 @@
+using Microsoft.Extensions.Options;
+using Microsoft.Extensions.Primitives;
+
+using RemoteExec.Server.Configuration;
+
+using System.Collections.Concurrent;
+
+namespace RemoteExec.Server.Middleware;
+
+public class ApiKeyAuthenticationMiddleware
+{
+    private readonly RequestDelegate _next;
+    private readonly ILogger<ApiKeyAuthenticationMiddleware> _logger;
+    private readonly ConcurrentDictionary<string, ApiKeyConfiguration> _apiKeys;
+
+    public ApiKeyAuthenticationMiddleware(
+        RequestDelegate next,
+        IOptionsMonitor<AuthenticationConfiguration> authOptions,
+        ILogger<ApiKeyAuthenticationMiddleware> logger)
+    {
+        _next = next;
+        _logger = logger;
+
+        // Build lookup dictionary from configuration
+        _apiKeys = new ConcurrentDictionary<string, ApiKeyConfiguration>();
+
+        // Initial load
+        LoadApiKeys(authOptions.CurrentValue);
+
+        // Watch for configuration changes
+        _ = authOptions.OnChange(LoadApiKeys);
+    }
+
+    private void LoadApiKeys(AuthenticationConfiguration config)
+    {
+        _apiKeys.Clear();
+
+        if (config.ApiKeys == null || config.ApiKeys.Count == 0)
+        {
+            _logger.LogWarning("No API keys configured. All requests will be rejected.");
+            return;
+        }
+
+        foreach (ApiKeyConfiguration apiKey in config.ApiKeys.Where(k => k.Enabled))
+        {
+            if (string.IsNullOrWhiteSpace(apiKey.Key))
+            {
+                _logger.LogWarning("Skipping empty API key configuration");
+                continue;
+            }
+
+            if (_apiKeys.TryAdd(apiKey.Key, apiKey))
+            {
+                _logger.LogInformation(
+                    "Registered API key: {Description}",
+                    apiKey.Description ?? "No description");
+            }
+            else
+            {
+                _logger.LogWarning(
+                    "Duplicate API key found and skipped: {Description}",
+                    apiKey.Description ?? "No description");
+            }
+        }
+
+        _logger.LogInformation("Loaded {Count} active API keys", _apiKeys.Count);
+    }
+
+    public async Task InvokeAsync(HttpContext context)
+    {
+        // Skip authentication for health checks
+        if (context.Request.Path.StartsWithSegments("/health"))
+        {
+            await _next(context);
+            return;
+        }
+
+        // Check if any API keys are configured
+        if (_apiKeys.IsEmpty)
+        {
+            _logger.LogError("No API keys configured. Rejecting request to {Path}", context.Request.Path);
+
+            context.Response.StatusCode = 503;
+
+            await context.Response.WriteAsync("Service is not properly configured");
+            return;
+        }
+
+        // Check for API key in header
+        if (!context.Request.Headers.TryGetValue("X-API-Key", out StringValues extractedApiKey))
+        {
+            _logger.LogWarning("API Key missing from request to {Path} from {RemoteIp}", context.Request.Path, context.Connection.RemoteIpAddress);
+
+            context.Response.StatusCode = 401;
+
+            await context.Response.WriteAsync("API Key is missing");
+            return;
+        }
+
+        string providedKey = extractedApiKey.ToString();
+
+        // Validate API key
+        if (!_apiKeys.TryGetValue(providedKey, out ApiKeyConfiguration? apiKeyConfig))
+        {
+            _logger.LogWarning("Invalid API Key provided for request to {Path} from {RemoteIp}",
+                context.Request.Path,
+                context.Connection.RemoteIpAddress);
+            context.Response.StatusCode = 401;
+            await context.Response.WriteAsync("Invalid API Key");
+            return;
+        }
+
+        // Store API key info in HttpContext for potential use in controllers
+        context.Items["ApiKeyDescription"] = apiKeyConfig.Description;
+        context.Items["ApiKey"] = providedKey;
+
+        _logger.LogDebug("Authenticated request to {Path} using key: {Description}",
+            context.Request.Path,
+            apiKeyConfig.Description ?? "No description");
+
+        await _next(context);
+    }
+}