cmd/k8s-operator,k8s-operator/sessionrecording: support recording kubectl exec sessions over WebSockets (#12947)

cmd/k8s-operator,k8s-operator/sessionrecording: support recording WebSocket sessions

Kubernetes currently supports two streaming protocols, SPDY and WebSockets.
WebSockets are replacing SPDY, see
https://github.com/kubernetes/enhancements/issues/4006.
We were currently only supporting SPDY, erroring out if session
was not SPDY and relying on the kube's built-in SPDY fallback.

This PR:

- adds support for parsing contents of 'kubectl exec' sessions streamed
over WebSockets

- adds logic to distinguish 'kubectl exec' requests for a SPDY/WebSockets
sessions and call the relevant handler

Updates tailscale/corp#19821

Signed-off-by: Irbe Krumina <irbe@tailscale.com>
Co-authored-by: Tom Proctor <tomhjp@users.noreply.github.com>

k8s-operator/sessionrecording/spdy/frame_test.go

@@ -9,11 +9,15 @@ import (
 	"bytes"
 	"compress/zlib"
 	"encoding/binary"
+	"fmt"
 	"io"
 	"net/http"
 	"reflect"
 	"strings"
 	"testing"
+	"time"
+
+	"math/rand"
 
 	"github.com/google/go-cmp/cmp"
 	"go.uber.org/zap"
@@ -200,6 +204,29 @@ func Test_spdyFrame_parseHeaders(t *testing.T) {
 	}
 }
 
+// Test_spdyFrame_ParseRand calls spdyFrame.Parse with randomly generated bytes
+// to test that it doesn't panic.
+func Test_spdyFrame_ParseRand(t *testing.T) {
+	zl, err := zap.NewDevelopment()
+	if err != nil {
+		t.Fatal(err)
+	}
+	r := rand.New(rand.NewSource(time.Now().UnixNano()))
+	for i := range 100 {
+		n := r.Intn(4096)
+		b := make([]byte, n)
+		_, err := r.Read(b)
+		if err != nil {
+			t.Fatalf("error generating random byte slice: %v", err)
+		}
+		sf := &spdyFrame{}
+		f := func() {
+			sf.Parse(b, zl.Sugar())
+		}
+		testPanic(t, f, fmt.Sprintf("[%d] Parse panicked running with byte slice of length %d: %v", i, n, r))
+	}
+}
+
 // payload takes a control frame type and a map with 0 or more header keys and
 // values and returns a SPDY control frame payload with the header as SPDY zlib
 // compressed header name/value block. The payload is padded with arbitrary
@@ -291,3 +318,13 @@ func header(hs map[string]string) http.Header {
 	}
 	return h
 }
+
+func testPanic(t *testing.T, f func(), msg string) {
+	t.Helper()
+	defer func() {
+		if r := recover(); r != nil {
+			t.Fatal(msg, r)
+		}
+	}()
+	f()
+}