feat(auth): introduce scoped based authorization

Signed-off-by: Arda Güçlü <[email protected]>

Author: ardaguclu

pkg/http/authorization.go

@@ -88,6 +88,7 @@ func AuthorizationMiddleware(requireOAuth bool, serverURL string, oidcProvider *
 			// Scopes are likely to be used for authorization.
 			scopes := claims.GetScopes()
 			klog.V(2).Infof("JWT token validated - Scopes: %v", scopes)
+			r = r.WithContext(context.WithValue(r.Context(), mcp.TokenScopesContextKey, scopes))
 
 			// Now, there are a couple of options:
 			// 1. If there is no authorization url configured for this MCP Server,

pkg/http/http.go

@@ -4,13 +4,14 @@ import (
 	"context"
 	"encoding/json"
 	"errors"
-	"github.com/coreos/go-oidc/v3/oidc"
 	"net/http"
 	"os"
 	"os/signal"
 	"syscall"
 	"time"
 
+	"github.com/coreos/go-oidc/v3/oidc"
+
 	"k8s.io/klog/v2"
 
 	"github.com/containers/kubernetes-mcp-server/pkg/config"
@@ -61,7 +62,7 @@ func Serve(ctx context.Context, mcpServer *mcp.Server, staticConfig *config.Stat
 		response := map[string]interface{}{
 			"authorization_servers":    authServers,
 			"authorization_server":     authServers[0],
-			"scopes_supported":         []string{},
+			"scopes_supported":         mcpServer.GetEnabledTools(),
 			"bearer_methods_supported": []string{"header"},
 		}
 

pkg/kubernetes-mcp-server/cmd/root.go

@@ -227,18 +227,6 @@ func (m *MCPServerOptions) Validate() error {
 			klog.Warningf("authorization-url is using http://, this is not recommended production use")
 		}
 	}
-	if m.StaticConfig.ServerURL != "" {
-		u, err := url.Parse(m.StaticConfig.ServerURL)
-		if err != nil {
-			return err
-		}
-		if u.Scheme != "https" && u.Scheme != "http" {
-			return fmt.Errorf("--server-url must be a valid URL")
-		}
-		if u.Scheme == "http" {
-			klog.Warningf("server-url is using http://, this is not recommended production use")
-		}
-	}
 	if m.StaticConfig.JwksURL != "" {
 		u, err := url.Parse(m.StaticConfig.JwksURL)
 		if err != nil {

pkg/kubernetes-mcp-server/cmd/root_test.go

@@ -255,28 +255,3 @@ func TestAuthorizationURL(t *testing.T) {
 		}
 	})
 }
-
-func TestServerURL(t *testing.T) {
-	t.Run("invalid server-url without protocol", func(t *testing.T) {
-		ioStreams, _ := testStream()
-		rootCmd := NewMCPServer(ioStreams)
-		rootCmd.SetArgs([]string{"--version", "--require-oauth", "--port=8080", "--server-url", "example.com:8080", "--authorization-url", "https://example.com/auth"})
-		err := rootCmd.Execute()
-		if err == nil {
-			t.Fatal("Expected error for invalid server-url without protocol, got nil")
-		}
-		expected := "--server-url must be a valid URL"
-		if !strings.Contains(err.Error(), expected) {
-			t.Fatalf("Expected error to contain %s, got %s", expected, err.Error())
-		}
-	})
-	t.Run("valid server-url with https", func(t *testing.T) {
-		ioStreams, _ := testStream()
-		rootCmd := NewMCPServer(ioStreams)
-		rootCmd.SetArgs([]string{"--version", "--require-oauth", "--port=8080", "--server-url", "https://example.com:8080", "--authorization-url", "https://example.com/auth"})
-		err := rootCmd.Execute()
-		if err != nil {
-			t.Fatalf("Expected no error for valid https server-url, got %s", err.Error())
-		}
-	})
-}

pkg/mcp/mcp.go

@@ -19,6 +19,8 @@ import (
 	"github.com/containers/kubernetes-mcp-server/pkg/version"
 )
 
+const TokenScopesContextKey = "TokenScopesContextKey"
+
 type Configuration struct {
 	Profile    Profile
 	ListOutput output.Output
@@ -45,20 +47,29 @@ func (c *Configuration) isToolApplicable(tool server.ServerTool) bool {
 type Server struct {
 	configuration *Configuration
 	server        *server.MCPServer
+	enabledTools  []string
 	k             *internalk8s.Manager
 }
 
 func NewServer(configuration Configuration) (*Server, error) {
+	var serverOptions []server.ServerOption
+	serverOptions = append(serverOptions,
+		server.WithResourceCapabilities(true, true),
+		server.WithPromptCapabilities(true),
+		server.WithToolCapabilities(true),
+		server.WithLogging(),
+		server.WithToolHandlerMiddleware(toolCallLoggingMiddleware),
+	)
+	if configuration.StaticConfig.RequireOAuth {
+		serverOptions = append(serverOptions, server.WithToolHandlerMiddleware(toolScopedAuthorizationMiddleware))
+	}
+
 	s := &Server{
 		configuration: &configuration,
 		server: server.NewMCPServer(
 			version.BinaryName,
 			version.Version,
-			server.WithResourceCapabilities(true, true),
-			server.WithPromptCapabilities(true),
-			server.WithToolCapabilities(true),
-			server.WithLogging(),
-			server.WithToolHandlerMiddleware(toolCallLoggingMiddleware),
+			serverOptions...,
 		),
 	}
 	if err := s.reloadKubernetesClient(); err != nil {
@@ -81,6 +92,7 @@ func (s *Server) reloadKubernetesClient() error {
 			continue
 		}
 		applicableTools = append(applicableTools, tool)
+		s.enabledTools = append(s.enabledTools, tool.Tool.Name)
 	}
 	s.server.SetTools(applicableTools...)
 	return nil
@@ -125,6 +137,10 @@ func (s *Server) GetKubernetesAPIServerHost() string {
 	return s.k.GetAPIServerHost()
 }
 
+func (s *Server) GetEnabledTools() []string {
+	return s.enabledTools
+}
+
 func (s *Server) Close() {
 	if s.k != nil {
 		s.k.Close()
@@ -181,3 +197,16 @@ func toolCallLoggingMiddleware(next server.ToolHandlerFunc) server.ToolHandlerFu
 		return next(ctx, ctr)
 	}
 }
+
+func toolScopedAuthorizationMiddleware(next server.ToolHandlerFunc) server.ToolHandlerFunc {
+	return func(ctx context.Context, ctr mcp.CallToolRequest) (*mcp.CallToolResult, error) {
+		scopes, ok := ctx.Value(TokenScopesContextKey).([]string)
+		if !ok {
+			return NewTextResult("", fmt.Errorf("Authorization failed: Access denied: Tool '%s' requires scope 'mcp:%s' but no scope is available", ctr.Params.Name, ctr.Params.Name)), nil
+		}
+		if !slices.Contains(scopes, "mcp:"+ctr.Params.Name) && !slices.Contains(scopes, ctr.Params.Name) {
+			return NewTextResult("", fmt.Errorf("Authorization failed: Access denied: Tool '%s' requires scope 'mcp:%s' but only scopes %s are available", ctr.Params.Name, ctr.Params.Name, scopes)), nil
+		}
+		return next(ctx, ctr)
+	}
+}