fix(server): do not get client by id for introspection (#467)

As introspection is a Oauth mechanism for resource servers only,
it does not make sense to get an oidc client by ID.
The original OP did not do this and now we make the server behavior similar.

pkg/op/server.go

@@ -127,7 +127,7 @@ type Server interface {
 	// Introspect handles the OAuth 2.0 Token Introspection endpoint.
 	// https://datatracker.ietf.org/doc/html/rfc7662
 	// The recommended Response Data type is [oidc.IntrospectionResponse].
-	Introspect(context.Context, *ClientRequest[oidc.IntrospectionRequest]) (*Response, error)
+	Introspect(context.Context, *Request[IntrospectionRequest]) (*Response, error)
 
 	// UserInfo handles the UserInfo endpoint and returns Claims about the authenticated End-User.
 	// https://openid.net/specs/openid-connect-core-1_0.html#UserInfo
@@ -329,7 +329,7 @@ func (UnimplementedServer) DeviceToken(ctx context.Context, r *ClientRequest[oid
 	return nil, unimplementedGrantError(oidc.GrantTypeDeviceCode)
 }
 
-func (UnimplementedServer) Introspect(ctx context.Context, r *ClientRequest[oidc.IntrospectionRequest]) (*Response, error) {
+func (UnimplementedServer) Introspect(ctx context.Context, r *Request[IntrospectionRequest]) (*Response, error) {
 	return nil, unimplementedError(r)
 }
 

pkg/op/server_http.go

@@ -102,7 +102,7 @@ func (s *webServer) createRouter() {
 	s.endpointRoute(s.endpoints.Authorization, s.authorizeHandler)
 	s.endpointRoute(s.endpoints.DeviceAuthorization, s.withClient(s.deviceAuthorizationHandler))
 	s.endpointRoute(s.endpoints.Token, s.tokensHandler)
-	s.endpointRoute(s.endpoints.Introspection, s.withClient(s.introspectionHandler))
+	s.endpointRoute(s.endpoints.Introspection, s.introspectionHandler)
 	s.endpointRoute(s.endpoints.Userinfo, s.userInfoHandler)
 	s.endpointRoute(s.endpoints.Revocation, s.withClient(s.revocationHandler))
 	s.endpointRoute(s.endpoints.EndSession, s.endSessionHandler)
@@ -136,7 +136,21 @@ func (s *webServer) withClient(handler clientHandler) http.HandlerFunc {
 }
 
 func (s *webServer) verifyRequestClient(r *http.Request) (_ Client, err error) {
-	if err = r.ParseForm(); err != nil {
+	cc, err := s.parseClientCredentials(r)
+	if err != nil {
+		return nil, err
+	}
+	return s.server.VerifyClient(r.Context(), &Request[ClientCredentials]{
+		Method: r.Method,
+		URL:    r.URL,
+		Header: r.Header,
+		Form:   r.Form,
+		Data:   cc,
+	})
+}
+
+func (s *webServer) parseClientCredentials(r *http.Request) (_ *ClientCredentials, err error) {
+	if err := r.ParseForm(); err != nil {
 		return nil, oidc.ErrInvalidRequest().WithDescription("error parsing form").WithParent(err)
 	}
 	cc := new(ClientCredentials)
@@ -160,13 +174,7 @@ func (s *webServer) verifyRequestClient(r *http.Request) (_ Client, err error) {
 	if cc.ClientAssertion != "" && cc.ClientAssertionType != oidc.ClientAssertionTypeJWTAssertion {
 		return nil, oidc.ErrInvalidRequest().WithDescription("invalid client_assertion_type %s", cc.ClientAssertionType)
 	}
-	return s.server.VerifyClient(r.Context(), &Request[ClientCredentials]{
-		Method: r.Method,
-		URL:    r.URL,
-		Header: r.Header,
-		Form:   r.Form,
-		Data:   cc,
-	})
+	return cc, nil
 }
 
 func (s *webServer) authorizeHandler(w http.ResponseWriter, r *http.Request) {
@@ -378,8 +386,13 @@ func (s *webServer) deviceTokenHandler(w http.ResponseWriter, r *http.Request, c
 	resp.writeOut(w)
 }
 
-func (s *webServer) introspectionHandler(w http.ResponseWriter, r *http.Request, client Client) {
-	if client.AuthMethod() == oidc.AuthMethodNone {
+func (s *webServer) introspectionHandler(w http.ResponseWriter, r *http.Request) {
+	cc, err := s.parseClientCredentials(r)
+	if err != nil {
+		WriteError(w, r, err, s.getLogger(r.Context()))
+		return
+	}
+	if cc.ClientSecret == "" && cc.ClientAssertion == "" {
 		WriteError(w, r, oidc.ErrInvalidClient().WithDescription("client must be authenticated"), s.getLogger(r.Context()))
 		return
 	}
@@ -392,7 +405,7 @@ func (s *webServer) introspectionHandler(w http.ResponseWriter, r *http.Request,
 		WriteError(w, r, oidc.ErrInvalidRequest().WithDescription("token missing"), s.getLogger(r.Context()))
 		return
 	}
-	resp, err := s.server.Introspect(r.Context(), newClientRequest(r, request, client))
+	resp, err := s.server.Introspect(r.Context(), newRequest(r, &IntrospectionRequest{cc, request}))
 	if err != nil {
 		WriteError(w, r, err, s.getLogger(r.Context()))
 		return

pkg/op/server_http_test.go

@@ -1001,14 +1001,12 @@ func Test_webServer_introspectionHandler(t *testing.T) {
 	tests := []struct {
 		name    string
 		decoder httphelper.Decoder
-		client  Client
 		r       *http.Request
 		want    webServerResult
 	}{
 		{
 			name:    "decoder error",
 			decoder: schema.NewDecoder(),
-			client:  newClient(clientTypeUserAgent),
 			r:       httptest.NewRequest(http.MethodPost, "/", strings.NewReader("foo=bar")),
 			want: webServerResult{
 				wantStatus: http.StatusBadRequest,
@@ -1018,8 +1016,7 @@ func Test_webServer_introspectionHandler(t *testing.T) {
 		{
 			name:    "public client",
 			decoder: testDecoder,
-			client:  newClient(clientTypeNative),
-			r:       httptest.NewRequest(http.MethodPost, "/", strings.NewReader("foo=bar")),
+			r:       httptest.NewRequest(http.MethodPost, "/", strings.NewReader("client_id=123")),
 			want: webServerResult{
 				wantStatus: http.StatusBadRequest,
 				wantBody:   `{"error":"invalid_client", "error_description":"client must be authenticated"}`,
@@ -1028,8 +1025,7 @@ func Test_webServer_introspectionHandler(t *testing.T) {
 		{
 			name:    "token missing",
 			decoder: testDecoder,
-			client:  newClient(clientTypeWeb),
-			r:       httptest.NewRequest(http.MethodPost, "/", strings.NewReader("foo=bar")),
+			r:       httptest.NewRequest(http.MethodPost, "/", strings.NewReader("client_id=123&client_secret=SECRET")),
 			want: webServerResult{
 				wantStatus: http.StatusBadRequest,
 				wantBody:   `{"error":"invalid_request", "error_description":"token missing"}`,
@@ -1038,8 +1034,7 @@ func Test_webServer_introspectionHandler(t *testing.T) {
 		{
 			name:    "unimplemented Introspect called",
 			decoder: testDecoder,
-			client:  newClient(clientTypeWeb),
-			r:       httptest.NewRequest(http.MethodPost, "/", strings.NewReader("token=xxx")),
+			r:       httptest.NewRequest(http.MethodPost, "/", strings.NewReader("client_id=123&client_secret=SECRET&token=xxx")),
 			want: webServerResult{
 				wantStatus: UnimplementedStatusCode,
 				wantBody:   `{"error":"server_error", "error_description":"/ not implemented on this server"}`,
@@ -1053,7 +1048,7 @@ func Test_webServer_introspectionHandler(t *testing.T) {
 				decoder: tt.decoder,
 				logger:  slog.Default(),
 			}
-			runWebServerClientTest(t, s.introspectionHandler, tt.r, tt.client, tt.want)
+			runWebServerTest(t, s.introspectionHandler, tt.r, tt.want)
 		})
 	}
 }

pkg/op/server_legacy.go

@@ -315,13 +315,30 @@ func (s *LegacyServer) DeviceToken(ctx context.Context, r *ClientRequest[oidc.De
 	return NewResponse(resp), nil
 }
 
-func (s *LegacyServer) Introspect(ctx context.Context, r *ClientRequest[oidc.IntrospectionRequest]) (*Response, error) {
+func (s *LegacyServer) authenticateResourceClient(ctx context.Context, cc *ClientCredentials) (string, error) {
+	if cc.ClientAssertion != "" {
+		if jp, ok := s.provider.(ClientJWTProfile); ok {
+			return ClientJWTAuth(ctx, oidc.ClientAssertionParams{ClientAssertion: cc.ClientAssertion}, jp)
+		}
+		return "", oidc.ErrInvalidClient().WithDescription("client_assertion not supported")
+	}
+	if err := s.provider.Storage().AuthorizeClientIDSecret(ctx, cc.ClientID, cc.ClientSecret); err != nil {
+		return "", oidc.ErrUnauthorizedClient().WithParent(err)
+	}
+	return cc.ClientID, nil
+}
+
+func (s *LegacyServer) Introspect(ctx context.Context, r *Request[IntrospectionRequest]) (*Response, error) {
+	clientID, err := s.authenticateResourceClient(ctx, r.Data.ClientCredentials)
+	if err != nil {
+		return nil, err
+	}
 	response := new(oidc.IntrospectionResponse)
 	tokenID, subject, ok := getTokenIDAndSubject(ctx, s.provider, r.Data.Token)
 	if !ok {
 		return NewResponse(response), nil
 	}
-	err := s.provider.Storage().SetIntrospectionFromToken(ctx, response, tokenID, subject, r.Client.GetID())
+	err = s.provider.Storage().SetIntrospectionFromToken(ctx, response, tokenID, subject, clientID)
 	if err != nil {
 		return NewResponse(response), nil
 	}

pkg/op/token_intospection.go

@@ -65,3 +65,8 @@ func ParseTokenIntrospectionRequest(r *http.Request, introspector Introspector)
 
 	return req.Token, clientID, nil
 }
+
+type IntrospectionRequest struct {
+	*ClientCredentials
+	*oidc.IntrospectionRequest
+}