add: gitea tools

Filters/McpAuthFilter.cs

@@ -0,0 +1,53 @@
+using System.Net;
+using Microsoft.Extensions.Primitives;
+
+namespace Alchegos.MCP.Filters;
+
+public class McpAuthFilter : IEndpointFilter
+{
+    private readonly ILogger<McpAuthFilter> _logger;
+
+    public McpAuthFilter(ILogger<McpAuthFilter> logger)
+    {
+        _logger = logger;
+    }
+
+    public async ValueTask<object?> InvokeAsync(EndpointFilterInvocationContext context, EndpointFilterDelegate next)
+    {
+        var expectedToken = Environment.GetEnvironmentVariable("MCP_API_KEY");
+
+        if (string.IsNullOrEmpty(expectedToken))
+        {
+            _logger.LogCritical("Required environment variable 'MCP_API_KEY' is not set.");
+            return Results.StatusCode((int)HttpStatusCode.InternalServerError);
+        }
+
+        var httpContext = context.HttpContext;
+
+        if (!httpContext.Request.Headers.TryGetValue("X-Api-Key", out StringValues receivedTokenValues) || receivedTokenValues.Count == 0)
+        {
+            _logger.LogWarning("MCP request rejected: Missing 'X-Api-Key' header.");
+            return Results.Unauthorized();
+        }
+
+        var receivedToken = receivedTokenValues.ToString();
+        if (!SecureCompare(receivedToken, expectedToken))
+        {
+            _logger.LogWarning("MCP request rejected: Invalid API Key provided.");
+            return Results.Unauthorized();
+        }
+
+        _logger.LogInformation("MCP request authenticated successfully.");
+        return await next(context);
+    }
+    
+    private static bool SecureCompare(string a, string b)
+    {
+        a ??= string.Empty;
+        b ??= string.Empty;
+        if (a.Length != b.Length) return false;
+        int diff = 0;
+        for (int i = 0; i < a.Length; i++) diff |= a[i] ^ b[i];
+        return diff == 0;
+    }
+}