From 1df4503b859a2b7b2b7f9c5bcf400f61cc29d349 Mon Sep 17 00:00:00 2001
From: Chao Xu <xuchao@google.com>
Date: Thu, 22 Apr 2021 23:17:39 +0000
Subject: [PATCH] Switch the order of adding SNICert and creating
 LoopbackClientConfig

---
 .../server/options/serving_with_loopback.go   |  6 ++-
 .../options/serving_with_loopback_test.go     | 51 +++++++++++++++++++
 2 files changed, 55 insertions(+), 2 deletions(-)
 create mode 100644 staging/src/k8s.io/apiserver/pkg/server/options/serving_with_loopback_test.go

diff --git a/staging/src/k8s.io/apiserver/pkg/server/options/serving_with_loopback.go b/staging/src/k8s.io/apiserver/pkg/server/options/serving_with_loopback.go
index 9f9a42f81b0..2317be82d26 100644
--- a/staging/src/k8s.io/apiserver/pkg/server/options/serving_with_loopback.go
+++ b/staging/src/k8s.io/apiserver/pkg/server/options/serving_with_loopback.go
@@ -60,10 +60,14 @@ func (s *SecureServingOptionsWithLoopback) ApplyTo(secureServingInfo **server.Se
 		return fmt.Errorf("failed to generate self-signed certificate for loopback connection: %v", err)
 	}
 
+	// Write to the front of SNICerts so that this overrides any other certs with the same name
+	(*secureServingInfo).SNICerts = append([]dynamiccertificates.SNICertKeyContentProvider{certProvider}, (*secureServingInfo).SNICerts...)
+
 	secureLoopbackClientConfig, err := (*secureServingInfo).NewLoopbackClientConfig(uuid.New().String(), certPem)
 	switch {
 	// if we failed and there's no fallback loopback client config, we need to fail
 	case err != nil && *loopbackClientConfig == nil:
+		(*secureServingInfo).SNICerts = (*secureServingInfo).SNICerts[1:]
 		return err
 
 	// if we failed, but we already have a fallback loopback client config (usually insecure), allow it
@@ -71,8 +75,6 @@ func (s *SecureServingOptionsWithLoopback) ApplyTo(secureServingInfo **server.Se
 
 	default:
 		*loopbackClientConfig = secureLoopbackClientConfig
-		// Write to the front of SNICerts so that this overrides any other certs with the same name
-		(*secureServingInfo).SNICerts = append([]dynamiccertificates.SNICertKeyContentProvider{certProvider}, (*secureServingInfo).SNICerts...)
 	}
 
 	return nil
diff --git a/staging/src/k8s.io/apiserver/pkg/server/options/serving_with_loopback_test.go b/staging/src/k8s.io/apiserver/pkg/server/options/serving_with_loopback_test.go
new file mode 100644
index 00000000000..f87b2fafe44
--- /dev/null
+++ b/staging/src/k8s.io/apiserver/pkg/server/options/serving_with_loopback_test.go
@@ -0,0 +1,51 @@
+/*
+Copyright 2021 The Kubernetes Authors.
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+    http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+*/
+
+package options
+
+import (
+	"net"
+	"testing"
+
+	"k8s.io/apiserver/pkg/server"
+	"k8s.io/client-go/rest"
+)
+
+func TestEmptyMainCert(t *testing.T) {
+	secureServingInfo := &server.SecureServingInfo{}
+	var loopbackClientConfig *rest.Config
+
+	s := (&SecureServingOptions{
+		BindAddress: net.ParseIP("127.0.0.1"),
+	}).WithLoopback()
+	ln, err := net.Listen("tcp", "127.0.0.1:0")
+	if err != nil {
+		t.Fatalf("failed to listen on 127.0.0.1:0")
+	}
+	defer ln.Close()
+	s.Listener = ln
+	s.BindPort = ln.Addr().(*net.TCPAddr).Port
+
+	if err := s.ApplyTo(&secureServingInfo, &loopbackClientConfig); err != nil {
+		t.Errorf("unexpected error: %v", err)
+	}
+	if loopbackClientConfig == nil {
+		t.Errorf("unexpected empty loopbackClientConfig")
+	}
+	if e, a := 1, len(secureServingInfo.SNICerts); e != a {
+		t.Errorf("expected %d SNICert, got %d", e, a)
+	}
+}