Update to 0.1.11 conformance tests

Author: stephentoub

Directory.Packages.props

@@ -7,7 +7,7 @@
     <MicrosoftExtensionsVersion>10.2.0</MicrosoftExtensionsVersion>
     <!-- Pin the conformance tester Node package version for CI stability.
          Keep in sync npm install step at ci-build-test.yml -->
-    <McpConformanceVersion>0.1.10</McpConformanceVersion>
+    <McpConformanceVersion>0.1.11</McpConformanceVersion>
   </PropertyGroup>
 
   <!-- Product dependencies shared -->

src/Common/Polyfills/System/IO/StreamExtensions.cs

@@ -1,7 +1,6 @@
 using ModelContextProtocol;
 using System.Buffers;
 using System.Runtime.InteropServices;
-using System.Text;
 
 #if !NET
 namespace System.IO;

src/ModelContextProtocol.AspNetCore/AuthorizationFilterSetup.cs

@@ -3,7 +3,6 @@
 using Microsoft.AspNetCore.Authorization;
 using Microsoft.Extensions.DependencyInjection;
 using Microsoft.Extensions.Options;
-using ModelContextProtocol.Protocol;
 using ModelContextProtocol.Server;
 
 namespace ModelContextProtocol.AspNetCore;

src/ModelContextProtocol.AspNetCore/DnsRebindingProtectionMiddleware.cs

@@ -0,0 +1,113 @@
+using Microsoft.AspNetCore.Builder;
+using Microsoft.AspNetCore.Http;
+using Microsoft.Extensions.Logging;
+using Microsoft.Net.Http.Headers;
+using System.Net;
+using System.Text.Json;
+
+namespace ModelContextProtocol.AspNetCore;
+
+/// <summary>
+/// Middleware that provides DNS rebinding protection for MCP servers by validating
+/// Host and Origin headers on requests to localhost servers.
+/// </summary>
+/// <remarks>
+/// <para>
+/// DNS rebinding attacks can allow malicious websites to bypass browser same-origin policy
+/// and make requests to localhost services. This middleware helps protect against such attacks
+/// by validating that Host and Origin headers match expected localhost values.
+/// </para>
+/// <para>
+/// Use <see cref="McpApplicationBuilderExtensions.UseMcpDnsRebindingProtection"/> to enable this middleware.
+/// </para>
+/// </remarks>
+/// <remarks>
+/// Initializes a new instance of the <see cref="DnsRebindingProtectionMiddleware"/> class.
+/// </remarks>
+internal sealed partial class DnsRebindingProtectionMiddleware(
+    RequestDelegate next,
+    ILogger<DnsRebindingProtectionMiddleware> logger)
+{
+    private readonly RequestDelegate _next = next;
+    private readonly ILogger<DnsRebindingProtectionMiddleware> _logger = logger;
+
+    /// <summary>
+    /// Processes the HTTP request and validates Host and Origin headers for localhost servers.
+    /// </summary>
+    public async Task InvokeAsync(HttpContext context)
+    {
+        // Only apply protection to localhost servers
+        var localEndpoint = context.Connection.LocalIpAddress;
+        bool isLocalhostServer = localEndpoint is null ||
+                                 IPAddress.IsLoopback(localEndpoint) ||
+                                 localEndpoint.Equals(IPAddress.IPv6Loopback);
+
+        if (isLocalhostServer)
+        {
+            // Validate Host header
+            var host = context.Request.Host.Host;
+            if (!IsLocalhost(host))
+            {
+                LogInvalidHostHeader(host);
+                await WriteJsonRpcErrorResponseAsync(context, $"Forbidden: Invalid Host header '{host}' for localhost server");
+                return;
+            }
+
+            // Validate Origin header if present
+            if (context.Request.Headers.TryGetValue(HeaderNames.Origin, out var originValues) &&
+                originValues.FirstOrDefault() is string origin &&
+                Uri.TryCreate(origin, UriKind.Absolute, out var originUri) &&
+                !IsLocalhost(originUri.Host))
+            {
+                LogInvalidOriginHeader(origin);
+                await WriteJsonRpcErrorResponseAsync(context, $"Forbidden: Invalid Origin header '{origin}' for localhost server");
+                return;
+            }
+        }
+
+        await _next(context).ConfigureAwait(false);
+    }
+
+    private static bool IsLocalhost(string host)
+    {
+        if (!string.IsNullOrWhiteSpace(host))
+        {
+            if (host.Equals("localhost", StringComparison.OrdinalIgnoreCase) ||
+                host.Equals("[::1]") ||
+                host.Equals("127.0.0.1"))
+            {
+                return true;
+            }
+
+            if (IPAddress.TryParse(host, out var ip))
+            {
+                return IPAddress.IsLoopback(ip);
+            }
+        }
+
+        return false;
+    }
+
+    private static Task WriteJsonRpcErrorResponseAsync(HttpContext context, string message)
+    {
+        context.Response.StatusCode = StatusCodes.Status403Forbidden;
+        context.Response.ContentType = "application/json";
+        return context.Response.WriteAsync($$"""
+            {
+                "jsonrpc": "2.0",
+                "error":
+                {
+                    "code": -32000,
+                    "message": "{{JsonEncodedText.Encode(message)}}"
+                },
+                "id": null
+            }
+            """);
+    }
+
+    [LoggerMessage(Level = LogLevel.Warning, Message = "Rejected request with invalid Host header '{Host}' for localhost server. This may indicate a DNS rebinding attack.")]
+    private partial void LogInvalidHostHeader(string? host);
+
+    [LoggerMessage(Level = LogLevel.Warning, Message = "Rejected request with invalid Origin header '{Origin}' for localhost server. This may indicate a DNS rebinding attack.")]
+    private partial void LogInvalidOriginHeader(string origin);
+}

src/ModelContextProtocol.AspNetCore/McpApplicationBuilderExtensions.cs

@@ -0,0 +1,47 @@
+using ModelContextProtocol.AspNetCore;
+
+namespace Microsoft.AspNetCore.Builder;
+
+/// <summary>
+/// Extension methods for adding MCP middleware to an <see cref="IApplicationBuilder"/>.
+/// </summary>
+public static class McpApplicationBuilderExtensions
+{
+    /// <summary>
+    /// Adds DNS rebinding protection middleware for MCP servers running on localhost.
+    /// </summary>
+    /// <param name="app">The <see cref="IApplicationBuilder"/>.</param>
+    /// <returns>The <see cref="IApplicationBuilder"/> for chaining.</returns>
+    /// <remarks>
+    /// <para>
+    /// This method provides protection against DNS rebinding attacks by validating that both
+    /// Host and Origin headers (when present) resolve to localhost addresses.
+    /// </para>
+    /// <para>
+    /// DNS rebinding attacks can allow malicious websites to bypass browser same-origin policy and make requests
+    /// to localhost services. This protection is recommended for any MCP server that binds to localhost.
+    /// </para>
+    /// <para>
+    /// For more information, see the <see href="https://github.com/modelcontextprotocol/typescript-sdk/security/advisories/GHSA-w48q-cv73-mx4w">MCP SDK security advisory</see>.
+    /// </para>
+    /// </remarks>
+    /// <example>
+    /// <code>
+    /// var builder = WebApplication.CreateBuilder(args);
+    /// builder.Services.AddMcpServer().WithHttpTransport();
+    /// 
+    /// var app = builder.Build();
+    /// app.UseMcpDnsRebindingProtection(); // Add before MapMcp()
+    /// app.MapMcp();
+    /// app.Run();
+    /// </code>
+    /// </example>
+    public static IApplicationBuilder UseMcpDnsRebindingProtection(this IApplicationBuilder app)
+    {
+        ArgumentNullException.ThrowIfNull(app);
+
+        app.UseMiddleware<DnsRebindingProtectionMiddleware>();
+
+        return app;
+    }
+}

src/ModelContextProtocol.Core/Authentication/ClientOAuthOptions.cs

@@ -23,6 +23,25 @@ public sealed class ClientOAuthOptions
     /// </remarks>
     public string? ClientSecret { get; set; }
 
+    /// <summary>
+    /// Gets or sets the private key in PEM format for JWT client assertion (private_key_jwt).
+    /// </summary>
+    /// <remarks>
+    /// When provided along with <see cref="JwtSigningAlgorithm"/>, the client will use JWT client 
+    /// assertion (private_key_jwt) for token endpoint authentication instead of client_secret.
+    /// This is typically used for machine-to-machine authentication with client_credentials grant.
+    /// </remarks>
+    public string? JwtPrivateKeyPem { get; set; }
+
+    /// <summary>
+    /// Gets or sets the signing algorithm for JWT client assertion.
+    /// </summary>
+    /// <remarks>
+    /// Common values include "RS256", "RS384", "RS512", "ES256", "ES384", "ES512".
+    /// This property is only used when <see cref="JwtPrivateKeyPem"/> is provided.
+    /// </remarks>
+    public string? JwtSigningAlgorithm { get; set; }
+
     /// <summary>
     /// Gets or sets the HTTPS URL pointing to this client's metadata document.
     /// </summary>