mcp: scaffolding of /.pomerium/mcp routes (#5580)

internal/mcp/handler.go

@@ -1,5 +1,18 @@
 package mcp
 
+import (
+	"context"
+	"net/http"
+	"path"
+
+	"github.com/gorilla/mux"
+	"github.com/rs/cors"
+	oteltrace "go.opentelemetry.io/otel/trace"
+
+	"github.com/pomerium/pomerium/config"
+	"github.com/pomerium/pomerium/pkg/telemetry/trace"
+)
+
 const (
 	DefaultPrefix = "/.pomerium/mcp"
 
@@ -9,3 +22,39 @@ const (
 	revocationEndpoint    = "/revoke"
 	tokenEndpoint         = "/token"
 )
+
+type Handler struct {
+	prefix string
+	trace  oteltrace.TracerProvider
+}
+
+func New(
+	ctx context.Context,
+	prefix string,
+	_ *config.Config,
+) (*Handler, error) {
+	tracerProvider := trace.NewTracerProvider(ctx, "MCP")
+	return &Handler{
+		prefix: prefix,
+		trace:  tracerProvider,
+	}, nil
+}
+
+// HandlerFunc returns a http.HandlerFunc that handles the mcp endpoints.
+func (srv *Handler) HandlerFunc() http.HandlerFunc {
+	r := mux.NewRouter()
+	r.Use(cors.New(cors.Options{
+		AllowedMethods: []string{http.MethodGet, http.MethodPost, http.MethodOptions},
+		AllowedOrigins: []string{"*"},
+		AllowedHeaders: []string{"content-type", "mcp-protocol-version"},
+	}).Handler)
+	r.Methods(http.MethodOptions).HandlerFunc(func(w http.ResponseWriter, _ *http.Request) {
+		w.WriteHeader(http.StatusNoContent)
+	})
+	r.Path(path.Join(srv.prefix, registerEndpoint)).Methods(http.MethodPost).HandlerFunc(srv.RegisterClient)
+	r.Path(path.Join(srv.prefix, authorizationEndpoint)).Methods(http.MethodGet).HandlerFunc(srv.Authorize)
+	r.Path(path.Join(srv.prefix, oauthCallbackEndpoint)).Methods(http.MethodGet).HandlerFunc(srv.OAuthCallback)
+	r.Path(path.Join(srv.prefix, tokenEndpoint)).Methods(http.MethodPost).HandlerFunc(srv.Token)
+
+	return r.ServeHTTP
+}

internal/mcp/handler_authorization.go

@@ -0,0 +1,10 @@
+package mcp
+
+import (
+	"net/http"
+)
+
+// Authorize handles the /authorize endpoint.
+func (srv *Handler) Authorize(w http.ResponseWriter, _ *http.Request) {
+	w.WriteHeader(http.StatusNotImplemented)
+}

internal/mcp/handler_oauth_callback.go

@@ -0,0 +1,9 @@
+package mcp
+
+import (
+	"net/http"
+)
+
+func (srv *Handler) OAuthCallback(w http.ResponseWriter, _ *http.Request) {
+	w.WriteHeader(http.StatusNotImplemented)
+}

internal/mcp/handler_register_client.go

@@ -0,0 +1,11 @@
+package mcp
+
+import (
+	"net/http"
+)
+
+// RegisterClient handles the /register endpoint.
+// It is used to register a new client with the MCP server.
+func (srv *Handler) RegisterClient(w http.ResponseWriter, _ *http.Request) {
+	w.WriteHeader(http.StatusNotImplemented)
+}

internal/mcp/handler_token.go

@@ -0,0 +1,10 @@
+package mcp
+
+import (
+	"net/http"
+)
+
+// Token handles the /token endpoint.
+func (srv *Handler) Token(w http.ResponseWriter, _ *http.Request) {
+	w.WriteHeader(http.StatusNotImplemented)
+}

proxy/handlers.go

@@ -24,6 +24,9 @@ func (p *Proxy) registerDashboardHandlers(r *mux.Router, opts *config.Options) *
 	h := httputil.DashboardSubrouter(r)
 	h.Use(middleware.SetHeaders(httputil.HeadersContentSecurityPolicy))
 
+	// model context protocol
+	h.PathPrefix("/mcp").Handler(p.mcp.HandlerFunc())
+
 	// special pomerium endpoints for users to view their session
 	h.Path("/").Handler(httputil.HandlerFunc(p.userInfo)).Methods(http.MethodGet)
 	h.Path("/device-enrolled").Handler(httputil.HandlerFunc(p.deviceEnrolled))

proxy/proxy.go

@@ -18,6 +18,7 @@ import (
 	"github.com/pomerium/pomerium/internal/handlers/webauthn"
 	"github.com/pomerium/pomerium/internal/httputil"
 	"github.com/pomerium/pomerium/internal/log"
+	"github.com/pomerium/pomerium/internal/mcp"
 	"github.com/pomerium/pomerium/internal/telemetry/metrics"
 	"github.com/pomerium/pomerium/pkg/cryptutil"
 	"github.com/pomerium/pomerium/pkg/storage"
@@ -63,6 +64,7 @@ type Proxy struct {
 	webauthn       *webauthn.Handler
 	tracerProvider oteltrace.TracerProvider
 	logoProvider   portal.LogoProvider
+	mcp            *mcp.Handler
 }
 
 // New takes a Proxy service from options and a validation function.
@@ -74,12 +76,18 @@ func New(ctx context.Context, cfg *config.Config) (*Proxy, error) {
 		return nil, err
 	}
 
+	mcp, err := mcp.New(ctx, mcp.DefaultPrefix, cfg)
+	if err != nil {
+		return nil, fmt.Errorf("proxy: failed to create mcp handler: %w", err)
+	}
+
 	p := &Proxy{
 		tracerProvider: tracerProvider,
 		state:          atomicutil.NewValue(state),
 		currentConfig:  atomicutil.NewValue(&config.Config{Options: config.NewDefaultOptions()}),
 		currentRouter:  atomicutil.NewValue(httputil.NewRouter()),
 		logoProvider:   portal.NewLogoProvider(),
+		mcp:            mcp,
 	}
 	p.OnConfigChange(ctx, cfg)
 	p.webauthn = webauthn.New(p.getWebauthnState)