feat: Multi Cluster Support

internal/test/kubernetes.go

@@ -8,15 +8,10 @@ func KubeConfigFake() *clientcmdapi.Config {
 	fakeConfig := clientcmdapi.NewConfig()
 	fakeConfig.Clusters["fake"] = clientcmdapi.NewCluster()
 	fakeConfig.Clusters["fake"].Server = "https://127.0.0.1:6443"
-	fakeConfig.Clusters["additional-cluster"] = clientcmdapi.NewCluster()
 	fakeConfig.AuthInfos["fake"] = clientcmdapi.NewAuthInfo()
-	fakeConfig.AuthInfos["additional-auth"] = clientcmdapi.NewAuthInfo()
 	fakeConfig.Contexts["fake-context"] = clientcmdapi.NewContext()
 	fakeConfig.Contexts["fake-context"].Cluster = "fake"
 	fakeConfig.Contexts["fake-context"].AuthInfo = "fake"
-	fakeConfig.Contexts["additional-context"] = clientcmdapi.NewContext()
-	fakeConfig.Contexts["additional-context"].Cluster = "additional-cluster"
-	fakeConfig.Contexts["additional-context"].AuthInfo = "additional-auth"
 	fakeConfig.CurrentContext = "fake-context"
 	return fakeConfig
 }

internal/test/mock_server.go

@@ -73,10 +73,14 @@ func (m *MockServer) Kubeconfig() *api.Config {
 }
 
 func (m *MockServer) KubeconfigFile(t *testing.T) string {
-	kubeconfig := filepath.Join(t.TempDir(), "config")
-	err := clientcmd.WriteToFile(*m.Kubeconfig(), kubeconfig)
+	return KubeconfigFile(t, m.Kubeconfig())
+}
+
+func KubeconfigFile(t *testing.T, kubeconfig *api.Config) string {
+	kubeconfigFile := filepath.Join(t.TempDir(), "config")
+	err := clientcmd.WriteToFile(*kubeconfig, kubeconfigFile)
 	require.NoError(t, err, "Expected no error writing kubeconfig file")
-	return kubeconfig
+	return kubeconfigFile
 }
 
 func WriteObject(w http.ResponseWriter, obj runtime.Object) {

pkg/api/toolsets.go

@@ -10,8 +10,29 @@ import (
 )
 
 type ServerTool struct {
-	Tool    Tool
-	Handler ToolHandlerFunc
+	Tool               Tool
+	Handler            ToolHandlerFunc
+	ClusterAware       *bool
+	TargetListProvider *bool
+}
+
+// IsClusterAware indicates whether the tool can accept a "cluster" or "context" parameter
+// to operate on a specific Kubernetes cluster context.
+// Defaults to true if not explicitly set
+func (s *ServerTool) IsClusterAware() bool {
+	if s.ClusterAware != nil {
+		return *s.ClusterAware
+	}
+	return true
+}
+
+// IsTargetListProvider indicates whether the tool is used to provide a list of targets (clusters/contexts)
+// Defaults to false if not explicitly set
+func (s *ServerTool) IsTargetListProvider() bool {
+	if s.TargetListProvider != nil {
+		return *s.TargetListProvider
+	}
+	return false
 }
 
 type Toolset interface {

pkg/api/toolsets_test.go

@@ -0,0 +1,47 @@
+package api
+
+import (
+	"testing"
+
+	"github.com/stretchr/testify/suite"
+	"k8s.io/utils/ptr"
+)
+
+type ToolsetsSuite struct {
+	suite.Suite
+}
+
+func (s *ToolsetsSuite) TestServerTool() {
+	s.Run("IsClusterAware", func() {
+		s.Run("defaults to true", func() {
+			tool := &ServerTool{}
+			s.True(tool.IsClusterAware(), "Expected IsClusterAware to be true by default")
+		})
+		s.Run("can be set to false", func() {
+			tool := &ServerTool{ClusterAware: ptr.To(false)}
+			s.False(tool.IsClusterAware(), "Expected IsClusterAware to be false when set to false")
+		})
+		s.Run("can be set to true", func() {
+			tool := &ServerTool{ClusterAware: ptr.To(true)}
+			s.True(tool.IsClusterAware(), "Expected IsClusterAware to be true when set to true")
+		})
+	})
+	s.Run("IsTargetListProvider", func() {
+		s.Run("defaults to false", func() {
+			tool := &ServerTool{}
+			s.False(tool.IsTargetListProvider(), "Expected IsTargetListProvider to be false by default")
+		})
+		s.Run("can be set to false", func() {
+			tool := &ServerTool{TargetListProvider: ptr.To(false)}
+			s.False(tool.IsTargetListProvider(), "Expected IsTargetListProvider to be false when set to false")
+		})
+		s.Run("can be set to true", func() {
+			tool := &ServerTool{TargetListProvider: ptr.To(true)}
+			s.True(tool.IsTargetListProvider(), "Expected IsTargetListProvider to be true when set to true")
+		})
+	})
+}
+
+func TestToolsets(t *testing.T) {
+	suite.Run(t, new(ToolsetsSuite))
+}

pkg/config/config.go

@@ -6,6 +6,11 @@ import (
 	"github.com/BurntSushi/toml"
 )
 
+const (
+	ClusterProviderKubeConfig = "kubeconfig"
+	ClusterProviderInCluster  = "in-cluster"
+)
+
 // StaticConfig is the configuration for the server.
 // It allows to configure server specific settings and tools to be enabled or disabled.
 type StaticConfig struct {
@@ -49,6 +54,12 @@ type StaticConfig struct {
 	StsScopes            []string `toml:"sts_scopes,omitempty"`
 	CertificateAuthority string   `toml:"certificate_authority,omitempty"`
 	ServerURL            string   `toml:"server_url,omitempty"`
+	// ClusterProviderStrategy is how the server finds clusters.
+	// If set to "kubeconfig", the clusters will be loaded from those in the kubeconfig.
+	// If set to "in-cluster", the server will use the in cluster config
+	ClusterProviderStrategy string `toml:"cluster_provider_strategy,omitempty"`
+	// ClusterContexts is which context should be used for each cluster
+	ClusterContexts map[string]string `toml:"cluster_contexts"`
 }
 
 func Default() *StaticConfig {

pkg/http/authorization.go

@@ -1,8 +1,11 @@
 package http
 
 import (
+	"bytes"
 	"context"
+	"encoding/json"
 	"fmt"
+	"io"
 	"net/http"
 	"strings"
 
@@ -20,7 +23,44 @@ import (
 
 type KubernetesApiTokenVerifier interface {
 	// KubernetesApiVerifyToken TODO: clarify proper implementation
-	KubernetesApiVerifyToken(ctx context.Context, token, audience string) (*authenticationapiv1.UserInfo, []string, error)
+	KubernetesApiVerifyToken(ctx context.Context, token, audience, cluster string) (*authenticationapiv1.UserInfo, []string, error)
+	// GetTargetParameterName returns the parameter name used for target identification in MCP requests
+	GetTargetParameterName() string
+}
+
+// extractTargetFromRequest extracts cluster parameter from MCP request body
+func extractTargetFromRequest(r *http.Request, targetName string) (string, error) {
+	if r.Body == nil {
+		return "", nil
+	}
+
+	// Read the body
+	body, err := io.ReadAll(r.Body)
+	if err != nil {
+		return "", err
+	}
+
+	// Restore the body for downstream handlers
+	r.Body = io.NopCloser(bytes.NewBuffer(body))
+
+	// Parse the MCP request
+	var mcpRequest struct {
+		Params struct {
+			Arguments map[string]interface{} `json:"arguments"`
+		} `json:"params"`
+	}
+
+	if err := json.Unmarshal(body, &mcpRequest); err != nil {
+		// If we can't parse the request, just return empty cluster (will use default)
+		return "", nil
+	}
+
+	// Extract target parameter
+	if cluster, ok := mcpRequest.Params.Arguments[targetName].(string); ok {
+		return cluster, nil
+	}
+
+	return "", nil
 }
 
 // AuthorizationMiddleware validates the OAuth flow for protected resources.
@@ -128,7 +168,12 @@ func AuthorizationMiddleware(staticConfig *config.StaticConfig, oidcProvider *oi
 			}
 			// Kubernetes API Server TokenReview validation
 			if err == nil && staticConfig.ValidateToken {
-				err = claims.ValidateWithKubernetesApi(r.Context(), staticConfig.OAuthAudience, verifier)
+				targetParameterName := verifier.GetTargetParameterName()
+				cluster, clusterErr := extractTargetFromRequest(r, targetParameterName)
+				if clusterErr != nil {
+					klog.V(2).Infof("Failed to extract cluster from request, using default: %v", clusterErr)
+				}
+				err = claims.ValidateWithKubernetesApi(r.Context(), staticConfig.OAuthAudience, cluster, verifier)
 			}
 			if err != nil {
 				klog.V(1).Infof("Authentication failed - JWT validation error: %s %s from %s, error: %v", r.Method, r.URL.Path, r.RemoteAddr, err)
@@ -198,9 +243,9 @@ func (c *JWTClaims) ValidateWithProvider(ctx context.Context, audience string, p
 	return nil
 }
 
-func (c *JWTClaims) ValidateWithKubernetesApi(ctx context.Context, audience string, verifier KubernetesApiTokenVerifier) error {
+func (c *JWTClaims) ValidateWithKubernetesApi(ctx context.Context, audience, cluster string, verifier KubernetesApiTokenVerifier) error {
 	if verifier != nil {
-		_, _, err := verifier.KubernetesApiVerifyToken(ctx, c.Token, audience)
+		_, _, err := verifier.KubernetesApiVerifyToken(ctx, c.Token, audience, cluster)
 		if err != nil {
 			return fmt.Errorf("kubernetes API token validation error: %v", err)
 		}

pkg/http/http_test.go

@@ -292,7 +292,7 @@ func TestHealthCheck(t *testing.T) {
 		})
 	})
 	// Health exposed even when require Authorization
-	testCaseWithContext(t, &httpContext{StaticConfig: &config.StaticConfig{RequireOAuth: true, ValidateToken: true}}, func(ctx *httpContext) {
+	testCaseWithContext(t, &httpContext{StaticConfig: &config.StaticConfig{RequireOAuth: true, ValidateToken: true, ClusterProviderStrategy: config.ClusterProviderKubeConfig}}, func(ctx *httpContext) {
 		resp, err := http.Get(fmt.Sprintf("http://%s/healthz", ctx.HttpAddress))
 		if err != nil {
 			t.Fatalf("Failed to get health check endpoint with OAuth: %v", err)
@@ -313,7 +313,7 @@ func TestWellKnownReverseProxy(t *testing.T) {
 		".well-known/openid-configuration",
 	}
 	// With No Authorization URL configured
-	testCaseWithContext(t, &httpContext{StaticConfig: &config.StaticConfig{RequireOAuth: true, ValidateToken: true}}, func(ctx *httpContext) {
+	testCaseWithContext(t, &httpContext{StaticConfig: &config.StaticConfig{RequireOAuth: true, ValidateToken: true, ClusterProviderStrategy: config.ClusterProviderKubeConfig}}, func(ctx *httpContext) {
 		for _, path := range cases {
 			resp, err := http.Get(fmt.Sprintf("http://%s/%s", ctx.HttpAddress, path))
 			t.Cleanup(func() { _ = resp.Body.Close() })
@@ -333,7 +333,12 @@ func TestWellKnownReverseProxy(t *testing.T) {
 		_, _ = w.Write([]byte(`NOT A JSON PAYLOAD`))
 	}))
 	t.Cleanup(invalidPayloadServer.Close)
-	invalidPayloadConfig := &config.StaticConfig{AuthorizationURL: invalidPayloadServer.URL, RequireOAuth: true, ValidateToken: true}
+	invalidPayloadConfig := &config.StaticConfig{
+		AuthorizationURL:        invalidPayloadServer.URL,
+		RequireOAuth:            true,
+		ValidateToken:           true,
+		ClusterProviderStrategy: config.ClusterProviderKubeConfig,
+	}
 	testCaseWithContext(t, &httpContext{StaticConfig: invalidPayloadConfig}, func(ctx *httpContext) {
 		for _, path := range cases {
 			resp, err := http.Get(fmt.Sprintf("http://%s/%s", ctx.HttpAddress, path))
@@ -358,7 +363,12 @@ func TestWellKnownReverseProxy(t *testing.T) {
 		_, _ = w.Write([]byte(`{"issuer": "https://example.com","scopes_supported":["mcp-server"]}`))
 	}))
 	t.Cleanup(testServer.Close)
-	staticConfig := &config.StaticConfig{AuthorizationURL: testServer.URL, RequireOAuth: true, ValidateToken: true}
+	staticConfig := &config.StaticConfig{
+		AuthorizationURL:        testServer.URL,
+		RequireOAuth:            true,
+		ValidateToken:           true,
+		ClusterProviderStrategy: config.ClusterProviderKubeConfig,
+	}
 	testCaseWithContext(t, &httpContext{StaticConfig: staticConfig}, func(ctx *httpContext) {
 		for _, path := range cases {
 			resp, err := http.Get(fmt.Sprintf("http://%s/%s", ctx.HttpAddress, path))
@@ -401,7 +411,12 @@ func TestWellKnownOverrides(t *testing.T) {
 			}`))
 	}))
 	t.Cleanup(testServer.Close)
-	baseConfig := config.StaticConfig{AuthorizationURL: testServer.URL, RequireOAuth: true, ValidateToken: true}
+	baseConfig := config.StaticConfig{
+		AuthorizationURL:        testServer.URL,
+		RequireOAuth:            true,
+		ValidateToken:           true,
+		ClusterProviderStrategy: config.ClusterProviderKubeConfig,
+	}
 	// With Dynamic Client Registration disabled
 	disableDynamicRegistrationConfig := baseConfig
 	disableDynamicRegistrationConfig.DisableDynamicClientRegistration = true
@@ -488,7 +503,7 @@ func TestMiddlewareLogging(t *testing.T) {
 
 func TestAuthorizationUnauthorized(t *testing.T) {
 	// Missing Authorization header
-	testCaseWithContext(t, &httpContext{StaticConfig: &config.StaticConfig{RequireOAuth: true, ValidateToken: true}}, func(ctx *httpContext) {
+	testCaseWithContext(t, &httpContext{StaticConfig: &config.StaticConfig{RequireOAuth: true, ValidateToken: true, ClusterProviderStrategy: config.ClusterProviderKubeConfig}}, func(ctx *httpContext) {
 		resp, err := http.Get(fmt.Sprintf("http://%s/mcp", ctx.HttpAddress))
 		if err != nil {
 			t.Fatalf("Failed to get protected endpoint: %v", err)
@@ -513,7 +528,7 @@ func TestAuthorizationUnauthorized(t *testing.T) {
 		})
 	})
 	// Authorization header without Bearer prefix
-	testCaseWithContext(t, &httpContext{StaticConfig: &config.StaticConfig{RequireOAuth: true, ValidateToken: true}}, func(ctx *httpContext) {
+	testCaseWithContext(t, &httpContext{StaticConfig: &config.StaticConfig{RequireOAuth: true, ValidateToken: true, ClusterProviderStrategy: config.ClusterProviderKubeConfig}}, func(ctx *httpContext) {
 		req, err := http.NewRequest("GET", fmt.Sprintf("http://%s/mcp", ctx.HttpAddress), nil)
 		if err != nil {
 			t.Fatalf("Failed to create request: %v", err)
@@ -538,7 +553,7 @@ func TestAuthorizationUnauthorized(t *testing.T) {
 		})
 	})
 	// Invalid Authorization header
-	testCaseWithContext(t, &httpContext{StaticConfig: &config.StaticConfig{RequireOAuth: true, ValidateToken: true}}, func(ctx *httpContext) {
+	testCaseWithContext(t, &httpContext{StaticConfig: &config.StaticConfig{RequireOAuth: true, ValidateToken: true, ClusterProviderStrategy: config.ClusterProviderKubeConfig}}, func(ctx *httpContext) {
 		req, err := http.NewRequest("GET", fmt.Sprintf("http://%s/mcp", ctx.HttpAddress), nil)
 		if err != nil {
 			t.Fatalf("Failed to create request: %v", err)
@@ -569,7 +584,7 @@ func TestAuthorizationUnauthorized(t *testing.T) {
 		})
 	})
 	// Expired Authorization Bearer token
-	testCaseWithContext(t, &httpContext{StaticConfig: &config.StaticConfig{RequireOAuth: true, ValidateToken: true}}, func(ctx *httpContext) {
+	testCaseWithContext(t, &httpContext{StaticConfig: &config.StaticConfig{RequireOAuth: true, ValidateToken: true, ClusterProviderStrategy: config.ClusterProviderKubeConfig}}, func(ctx *httpContext) {
 		req, err := http.NewRequest("GET", fmt.Sprintf("http://%s/mcp", ctx.HttpAddress), nil)
 		if err != nil {
 			t.Fatalf("Failed to create request: %v", err)
@@ -600,7 +615,7 @@ func TestAuthorizationUnauthorized(t *testing.T) {
 		})
 	})
 	// Invalid audience claim Bearer token
-	testCaseWithContext(t, &httpContext{StaticConfig: &config.StaticConfig{RequireOAuth: true, OAuthAudience: "expected-audience", ValidateToken: true}}, func(ctx *httpContext) {
+	testCaseWithContext(t, &httpContext{StaticConfig: &config.StaticConfig{RequireOAuth: true, OAuthAudience: "expected-audience", ValidateToken: true, ClusterProviderStrategy: config.ClusterProviderKubeConfig}}, func(ctx *httpContext) {
 		req, err := http.NewRequest("GET", fmt.Sprintf("http://%s/mcp", ctx.HttpAddress), nil)
 		if err != nil {
 			t.Fatalf("Failed to create request: %v", err)
@@ -633,7 +648,7 @@ func TestAuthorizationUnauthorized(t *testing.T) {
 	// Failed OIDC validation
 	oidcTestServer := NewOidcTestServer(t)
 	t.Cleanup(oidcTestServer.Close)
-	testCaseWithContext(t, &httpContext{StaticConfig: &config.StaticConfig{RequireOAuth: true, OAuthAudience: "mcp-server", ValidateToken: true}, OidcProvider: oidcTestServer.Provider}, func(ctx *httpContext) {
+	testCaseWithContext(t, &httpContext{StaticConfig: &config.StaticConfig{RequireOAuth: true, OAuthAudience: "mcp-server", ValidateToken: true, ClusterProviderStrategy: config.ClusterProviderKubeConfig}, OidcProvider: oidcTestServer.Provider}, func(ctx *httpContext) {
 		req, err := http.NewRequest("GET", fmt.Sprintf("http://%s/mcp", ctx.HttpAddress), nil)
 		if err != nil {
 			t.Fatalf("Failed to create request: %v", err)
@@ -670,7 +685,7 @@ func TestAuthorizationUnauthorized(t *testing.T) {
 		"aud": "mcp-server"
 	}`
 	validOidcToken := oidctest.SignIDToken(oidcTestServer.PrivateKey, "test-oidc-key-id", oidc.RS256, rawClaims)
-	testCaseWithContext(t, &httpContext{StaticConfig: &config.StaticConfig{RequireOAuth: true, OAuthAudience: "mcp-server", ValidateToken: true}, OidcProvider: oidcTestServer.Provider}, func(ctx *httpContext) {
+	testCaseWithContext(t, &httpContext{StaticConfig: &config.StaticConfig{RequireOAuth: true, OAuthAudience: "mcp-server", ValidateToken: true, ClusterProviderStrategy: config.ClusterProviderKubeConfig}, OidcProvider: oidcTestServer.Provider}, func(ctx *httpContext) {
 		req, err := http.NewRequest("GET", fmt.Sprintf("http://%s/mcp", ctx.HttpAddress), nil)
 		if err != nil {
 			t.Fatalf("Failed to create request: %v", err)
@@ -703,7 +718,7 @@ func TestAuthorizationUnauthorized(t *testing.T) {
 }
 
 func TestAuthorizationRequireOAuthFalse(t *testing.T) {
-	testCaseWithContext(t, &httpContext{StaticConfig: &config.StaticConfig{RequireOAuth: false}}, func(ctx *httpContext) {
+	testCaseWithContext(t, &httpContext{StaticConfig: &config.StaticConfig{RequireOAuth: false, ClusterProviderStrategy: config.ClusterProviderKubeConfig}}, func(ctx *httpContext) {
 		resp, err := http.Get(fmt.Sprintf("http://%s/mcp", ctx.HttpAddress))
 		if err != nil {
 			t.Fatalf("Failed to get protected endpoint: %v", err)
@@ -728,7 +743,7 @@ func TestAuthorizationRawToken(t *testing.T) {
 		{"mcp-server", true},  // Audience set, validation enabled
 	}
 	for _, c := range cases {
-		testCaseWithContext(t, &httpContext{StaticConfig: &config.StaticConfig{RequireOAuth: true, OAuthAudience: c.audience, ValidateToken: c.validateToken}}, func(ctx *httpContext) {
+		testCaseWithContext(t, &httpContext{StaticConfig: &config.StaticConfig{RequireOAuth: true, OAuthAudience: c.audience, ValidateToken: c.validateToken, ClusterProviderStrategy: config.ClusterProviderKubeConfig}}, func(ctx *httpContext) {
 			tokenReviewed := false
 			ctx.mockServer.Handle(http.HandlerFunc(func(w http.ResponseWriter, req *http.Request) {
 				if req.URL.EscapedPath() == "/apis/authentication.k8s.io/v1/tokenreviews" {
@@ -777,7 +792,7 @@ func TestAuthorizationOidcToken(t *testing.T) {
 	validOidcToken := oidctest.SignIDToken(oidcTestServer.PrivateKey, "test-oidc-key-id", oidc.RS256, rawClaims)
 	cases := []bool{false, true}
 	for _, validateToken := range cases {
-		testCaseWithContext(t, &httpContext{StaticConfig: &config.StaticConfig{RequireOAuth: true, OAuthAudience: "mcp-server", ValidateToken: validateToken}, OidcProvider: oidcTestServer.Provider}, func(ctx *httpContext) {
+		testCaseWithContext(t, &httpContext{StaticConfig: &config.StaticConfig{RequireOAuth: true, OAuthAudience: "mcp-server", ValidateToken: validateToken, ClusterProviderStrategy: config.ClusterProviderKubeConfig}, OidcProvider: oidcTestServer.Provider}, func(ctx *httpContext) {
 			tokenReviewed := false
 			ctx.mockServer.Handle(http.HandlerFunc(func(w http.ResponseWriter, req *http.Request) {
 				if req.URL.EscapedPath() == "/apis/authentication.k8s.io/v1/tokenreviews" {
@@ -833,13 +848,14 @@ func TestAuthorizationOidcTokenExchange(t *testing.T) {
 	cases := []bool{false, true}
 	for _, validateToken := range cases {
 		staticConfig := &config.StaticConfig{
-			RequireOAuth:    true,
-			OAuthAudience:   "mcp-server",
-			ValidateToken:   validateToken,
-			StsClientId:     "test-sts-client-id",
-			StsClientSecret: "test-sts-client-secret",
-			StsAudience:     "backend-audience",
-			StsScopes:       []string{"backend-scope"},
+			RequireOAuth:            true,
+			OAuthAudience:           "mcp-server",
+			ValidateToken:           validateToken,
+			StsClientId:             "test-sts-client-id",
+			StsClientSecret:         "test-sts-client-secret",
+			StsAudience:             "backend-audience",
+			StsScopes:               []string{"backend-scope"},
+			ClusterProviderStrategy: config.ClusterProviderKubeConfig,
 		}
 		testCaseWithContext(t, &httpContext{StaticConfig: staticConfig, OidcProvider: oidcTestServer.Provider}, func(ctx *httpContext) {
 			tokenReviewed := false