cmd/k8s-operator,k8s-operator/sessionrecording,sessionrecording,ssh/tailssh: refactor session recording functionality (#12945)

cmd/k8s-operator,k8s-operator/sessionrecording,sessionrecording,ssh/tailssh: refactor session recording functionality

Refactor SSH session recording functionality (mostly the bits related to
Kubernetes API server proxy 'kubectl exec' session recording):

- move the session recording bits used by both Tailscale SSH
and the Kubernetes API server proxy into a shared sessionrecording package,
to avoid having the operator to import ssh/tailssh

- move the Kubernetes API server proxy session recording functionality
into a k8s-operator/sessionrecording package, add some abstractions
in preparation for adding support for a second streaming protocol (WebSockets)

Updates tailscale/corp#19821

Signed-off-by: Irbe Krumina <irbe@tailscale.com>

k8s-operator/sessionrecording/hijacker_test.go

@@ -0,0 +1,112 @@
+// Copyright (c) Tailscale Inc & AUTHORS
+// SPDX-License-Identifier: BSD-3-Clause
+
+//go:build !plan9
+
+package sessionrecording
+
+import (
+	"context"
+	"errors"
+	"fmt"
+	"io"
+	"net"
+	"net/http"
+	"net/netip"
+	"net/url"
+	"testing"
+	"time"
+
+	"go.uber.org/zap"
+	"tailscale.com/client/tailscale/apitype"
+	"tailscale.com/k8s-operator/sessionrecording/fakes"
+	"tailscale.com/tailcfg"
+	"tailscale.com/tsnet"
+	"tailscale.com/tstest"
+)
+
+func Test_Hijacker(t *testing.T) {
+	zl, err := zap.NewDevelopment()
+	if err != nil {
+		t.Fatal(err)
+	}
+	tests := []struct {
+		name                        string
+		failOpen                    bool
+		failRecorderConnect         bool // fail initial connect to the recorder
+		failRecorderConnPostConnect bool // send error down the error channel
+		wantsConnClosed             bool
+		wantsSetupErr               bool
+	}{
+		{
+			name: "setup succeeds, conn stays open",
+		},
+		{
+			name:                "setup fails, policy is to fail open, conn stays open",
+			failOpen:            true,
+			failRecorderConnect: true,
+		},
+		{
+			name:                "setup fails, policy is to fail closed, conn is closed",
+			failRecorderConnect: true,
+			wantsSetupErr:       true,
+			wantsConnClosed:     true,
+		},
+		{
+			name:                        "connection fails post-initial connect, policy is to fail open, conn stays open",
+			failRecorderConnPostConnect: true,
+			failOpen:                    true,
+		},
+		{
+			name:                        "connection fails post-initial connect, policy is to fail closed, conn is closed",
+			failRecorderConnPostConnect: true,
+			wantsConnClosed:             true,
+		},
+	}
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			tc := &fakes.TestConn{}
+			ch := make(chan error)
+			h := &Hijacker{
+				connectToRecorder: func(context.Context, []netip.AddrPort, func(context.Context, string, string) (net.Conn, error)) (wc io.WriteCloser, rec []*tailcfg.SSHRecordingAttempt, _ <-chan error, err error) {
+					if tt.failRecorderConnect {
+						err = errors.New("test")
+					}
+					return wc, rec, ch, err
+				},
+				failOpen: tt.failOpen,
+				who:      &apitype.WhoIsResponse{Node: &tailcfg.Node{}, UserProfile: &tailcfg.UserProfile{}},
+				log:      zl.Sugar(),
+				ts:       &tsnet.Server{},
+				req:      &http.Request{URL: &url.URL{}},
+			}
+			ctx := context.Background()
+			_, err := h.setUpRecording(ctx, tc)
+			if (err != nil) != tt.wantsSetupErr {
+				t.Errorf("spdyHijacker.setupRecording() error = %v, wantErr %v", err, tt.wantsSetupErr)
+				return
+			}
+			if tt.failRecorderConnPostConnect {
+				select {
+				case ch <- errors.New("err"):
+				case <-time.After(time.Second * 15):
+					t.Errorf("error from recorder conn was not read within 15 seconds")
+				}
+			}
+			timeout := time.Second * 20
+			// TODO (irbekrm): cover case where an error is received
+			// over channel and the failure policy is to fail open
+			// (test that connection remains open over some period
+			// of time).
+			if err := tstest.WaitFor(timeout, func() (err error) {
+				if tt.wantsConnClosed != tc.IsClosed() {
+					return fmt.Errorf("got connection state: %t, wants connection state: %t", tc.IsClosed(), tt.wantsConnClosed)
+				}
+				return nil
+			}); err != nil {
+				t.Errorf("connection did not reach the desired state within %s", timeout.String())
+			}
+			ctx.Done()
+		})
+	}
+}