webhook: Implement controller-runtime webhook server with CipherSuite…

…s knob (#65)

* webhook: Override the controller-runtime server

The current controller-runtime allow to configure TLS min version but it
does not allow to configure the cipher suites. This change copy the
server from the controller-runtime library to allow modifications.

Signed-off-by: Quique Llorente <[email protected]>

* webhook: Add CipherSuites to server

To configure TLS CipherSuites this change add a new field to the Server
struct to set the strings representing them, they will be passed to the
underlaying tls.Config.

Signed-off-by: Quique Llorente <[email protected]>

pkg/webhook/internal/httpserver/server.go

@@ -0,0 +1,32 @@
+/*
+Copyright 2022 The Kube Admission Webhook 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 httpserver
+
+import (
+	"net/http"
+	"time"
+)
+
+// New returns a new server with sane defaults.
+func New(handler http.Handler) *http.Server {
+	return &http.Server{
+		Handler:           handler,
+		MaxHeaderBytes:    1 << 20,
+		IdleTimeout:       90 * time.Second, // matches http.DefaultTransport keep-alive timeout
+		ReadHeaderTimeout: 32 * time.Second,
+	}
+}

pkg/webhook/internal/metrics/metrics.go

@@ -0,0 +1,85 @@
+/*
+Copyright 2022 The Kube Admission Webhook 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 metrics
+
+import (
+	"net/http"
+
+	"github.com/prometheus/client_golang/prometheus"
+	"github.com/prometheus/client_golang/prometheus/promhttp"
+
+	"sigs.k8s.io/controller-runtime/pkg/metrics"
+)
+
+var (
+	// RequestLatency is a prometheus metric which is a histogram of the latency
+	// of processing admission requests.
+	RequestLatency = prometheus.NewHistogramVec(
+		prometheus.HistogramOpts{
+			Name: "kaw_latency_seconds",
+			Help: "Histogram of the latency of processing admission requests",
+		},
+		[]string{"webhook"},
+	)
+
+	// RequestTotal is a prometheus metric which is a counter of the total processed admission requests.
+	RequestTotal = func() *prometheus.CounterVec {
+		return prometheus.NewCounterVec(
+			prometheus.CounterOpts{
+				Name: "kaw_requests_total",
+				Help: "Total number of admission requests by HTTP status code.",
+			},
+			[]string{"webhook", "code"},
+		)
+	}()
+
+	// RequestInFlight is a prometheus metric which is a gauge of the in-flight admission requests.
+	RequestInFlight = func() *prometheus.GaugeVec {
+		return prometheus.NewGaugeVec(
+			prometheus.GaugeOpts{
+				Name: "kaw_requests_in_flight",
+				Help: "Current number of admission requests being served.",
+			},
+			[]string{"webhook"},
+		)
+	}()
+)
+
+func init() {
+	metrics.Registry.MustRegister(RequestLatency, RequestTotal, RequestInFlight)
+}
+
+// InstrumentedHook adds some instrumentation on top of the given webhook.
+func InstrumentedHook(path string, hookRaw http.Handler) http.Handler {
+	lbl := prometheus.Labels{"webhook": path}
+
+	lat := RequestLatency.MustCurryWith(lbl)
+	cnt := RequestTotal.MustCurryWith(lbl)
+	gge := RequestInFlight.With(lbl)
+
+	// Initialize the most likely HTTP status codes.
+	cnt.WithLabelValues("200")
+	cnt.WithLabelValues("500")
+
+	return promhttp.InstrumentHandlerDuration(
+		lat,
+		promhttp.InstrumentHandlerCounter(
+			cnt,
+			promhttp.InstrumentHandlerInFlight(gge, hookRaw),
+		),
+	)
+}