Improve the error message when URL form encoding is received.

pkg/interceptors/github/github.go

@@ -30,6 +30,9 @@ import (
 	"k8s.io/client-go/kubernetes"
 )
 
+// ErrInvalidContentType is returned when the content-type is not a JSON body.
+var ErrInvalidContentType = errors.New("form parameter encoding not supported, please change the hook to send JSON payloads")
+
 type Interceptor struct {
 	KubeClientSet          kubernetes.Interface
 	Logger                 *zap.SugaredLogger
@@ -49,6 +52,9 @@ func NewInterceptor(gh *triggersv1.GitHubInterceptor, k kubernetes.Interface, ns
 func (w *Interceptor) ExecuteTrigger(request *http.Request) (*http.Response, error) {
 	payload := []byte{}
 	var err error
+	if v := request.Header.Get("Content-Type"); v == "application/x-www-form-urlencoded" {
+		return nil, ErrInvalidContentType
+	}
 
 	if request.Body != nil {
 		defer request.Body.Close()

pkg/interceptors/github/github_test.go

@@ -259,3 +259,26 @@ func TestInterceptor_ExecuteTrigger_Signature(t *testing.T) {
 		})
 	}
 }
+
+func TestInterceptor_ExecuteTrigger_with_invalid_content_type(t *testing.T) {
+	ctx, _ := rtesting.SetupFakeContext(t)
+	logger, _ := logging.NewLogger("", "")
+	kubeClient := fakekubeclient.Get(ctx)
+	request := &http.Request{
+		Body: ioutil.NopCloser(bytes.NewBufferString("somepayload")),
+		Header: http.Header{
+			"Content-Type":    []string{"application/x-www-form-urlencoded"},
+			"X-Hub-Signature": []string{"foo"},
+		},
+	}
+	w := &Interceptor{
+		KubeClientSet:          kubeClient,
+		GitHub:                 &triggersv1.GitHubInterceptor{},
+		Logger:                 logger,
+		EventListenerNamespace: metav1.NamespaceDefault,
+	}
+	_, err := w.ExecuteTrigger(request)
+	if err != ErrInvalidContentType {
+		t.Fatalf("got error %v, want %v", err, ErrInvalidContentType)
+	}
+}