mcp: add to route config, 401 when unauthenticated (#5578)

authorize/check_response.go

@@ -98,6 +98,9 @@ func (a *Authorize) handleResultDenied(
 	case invalidClientCertReason(reasons):
 		denyStatusCode = httputil.StatusInvalidClientCertificate
 		denyStatusText = httputil.DetailsText(httputil.StatusInvalidClientCertificate)
+	case request.Policy.IsMCP():
+		denyStatusCode = http.StatusUnauthorized
+		denyStatusText = httputil.DetailsText(http.StatusUnauthorized)
 	}
 
 	return a.deniedResponse(ctx, in, denyStatusCode, denyStatusText, nil)
@@ -216,7 +219,7 @@ func (a *Authorize) requireLoginResponse(
 	options := a.currentConfig.Load().Options
 	state := a.state.Load()
 
-	if !a.shouldRedirect(in) {
+	if !a.shouldRedirect(in, request) {
 		return a.deniedResponse(ctx, in, http.StatusUnauthorized, "Unauthenticated", nil)
 	}
 
@@ -268,7 +271,7 @@ func (a *Authorize) requireWebAuthnResponse(
 		return a.okResponse(result.Headers), nil
 	}
 
-	if !a.shouldRedirect(in) {
+	if !a.shouldRedirect(in, request) {
 		return a.deniedResponse(ctx, in, http.StatusUnauthorized, "Unauthenticated", nil)
 	}
 
@@ -353,7 +356,11 @@ func (a *Authorize) userInfoEndpointURL(in *envoy_service_auth_v3.CheckRequest)
 	return urlutil.NewSignedURL(a.state.Load().sharedKey, debugEndpoint).Sign(), nil
 }
 
-func (a *Authorize) shouldRedirect(in *envoy_service_auth_v3.CheckRequest) bool {
+func (a *Authorize) shouldRedirect(in *envoy_service_auth_v3.CheckRequest, request *evaluator.Request) bool {
+	if request.Policy.IsMCP() {
+		return false
+	}
+
 	requestHeaders := in.GetAttributes().GetRequest().GetHttp().GetHeaders()
 	if requestHeaders == nil {
 		return true

authorize/check_response_test.go

@@ -113,6 +113,18 @@ func TestAuthorize_handleResult(t *testing.T) {
 		assert.NoError(t, err)
 		assert.Equal(t, 495, int(res.GetDeniedResponse().GetStatus().GetCode()))
 	})
+	t.Run("mcp-route-unauthenticated", func(t *testing.T) {
+		res, err := a.handleResult(context.Background(),
+			&envoy_service_auth_v3.CheckRequest{},
+			&evaluator.Request{
+				Policy: &config.Policy{MCP: &config.MCP{}},
+			},
+			&evaluator.Result{
+				Allow: evaluator.NewRuleResult(false, criteria.ReasonUserUnauthenticated),
+			})
+		assert.NoError(t, err)
+		assert.Equal(t, 401, int(res.GetDeniedResponse().GetStatus().GetCode()))
+	})
 }
 
 func TestAuthorize_okResponse(t *testing.T) {

config/custom.go

@@ -665,3 +665,17 @@ func (f JWTIssuerFormat) Valid() bool {
 	_, ok := knownJWTIssuerFormats[f]
 	return ok
 }
+
+func MCPFromPB(src *configpb.MCP) *MCP {
+	if src == nil {
+		return nil
+	}
+	return &MCP{}
+}
+
+func MCPToPB(src *MCP) *configpb.MCP {
+	if src == nil {
+		return nil
+	}
+	return &configpb.MCP{}
+}

config/policy.go

@@ -202,8 +202,14 @@ type Policy struct {
 	Policy *PPLPolicy `mapstructure:"policy" yaml:"policy,omitempty" json:"policy,omitempty"`
 
 	DependsOn []string `mapstructure:"depends_on" yaml:"depends_on,omitempty" json:"depends_on,omitempty"`
+
+	// MCP is an experimental support for Model Context Protocol upstreams
+	MCP *MCP `mapstructure:"mcp" yaml:"mcp,omitempty" json:"mcp,omitempty"`
 }
 
+// MCP is an experimental support for Model Context Protocol upstreams configuration
+type MCP struct{}
+
 // RewriteHeader is a policy configuration option to rewrite an HTTP header.
 type RewriteHeader struct {
 	Header string `mapstructure:"header" yaml:"header" json:"header"`
@@ -316,6 +322,7 @@ func NewPolicyFromProto(pb *configpb.Route) (*Policy, error) {
 		KubernetesServiceAccountToken:     pb.GetKubernetesServiceAccountToken(),
 		KubernetesServiceAccountTokenFile: pb.GetKubernetesServiceAccountTokenFile(),
 		LogoURL:                           pb.GetLogoUrl(),
+		MCP:                               MCPFromPB(pb.GetMcp()),
 		Name:                              pb.GetName(),
 		PassIdentityHeaders:               pb.PassIdentityHeaders,
 		Path:                              pb.GetPath(),
@@ -470,6 +477,7 @@ func (p *Policy) ToProto() (*configpb.Route, error) {
 		KubernetesServiceAccountToken:     p.KubernetesServiceAccountToken,
 		KubernetesServiceAccountTokenFile: p.KubernetesServiceAccountTokenFile,
 		LogoUrl:                           p.LogoURL,
+		Mcp:                               MCPToPB(p.MCP),
 		Name:                              p.Name,
 		PassIdentityHeaders:               p.PassIdentityHeaders,
 		Path:                              p.Path,
@@ -824,6 +832,11 @@ func (p *Policy) IsForKubernetes() bool {
 	return p.KubernetesServiceAccountTokenFile != "" || p.KubernetesServiceAccountToken != ""
 }
 
+// IsMCP returns true if the route is for the Model Context Protocol upstream server.
+func (p *Policy) IsMCP() bool {
+	return p != nil && p.MCP != nil
+}
+
 // IsTCP returns true if the route is for TCP.
 func (p *Policy) IsTCP() bool {
 	return strings.HasPrefix(p.From, "tcp")

pkg/grpc/config/config.proto

@@ -52,7 +52,7 @@ enum BearerTokenFormat {
   BEARER_TOKEN_FORMAT_IDP_IDENTITY_TOKEN = 3;
 }
 
-// Next ID: 72.
+// Next ID: 73.
 message Route {
   message StringList { repeated string values = 1; }
 
@@ -143,8 +143,12 @@ message Route {
   optional string idp_client_secret = 56;
   optional StringList idp_access_token_allowed_audiences = 69;
   bool show_error_details = 59;
+
+  optional MCP mcp = 72;
 }
 
+message MCP {}
+
 message PPLPolicy { bytes raw = 1; }
 
 message Policy {