gcs-sidecar framework

This commit makes the high level changes needed for gcs-sidecar
- Starts sidecar as service
- Dereferences the various valid rpc requests
- Adds code to invoke refs formatter

Note: This commit does not add invokers to the code for new
ResourceTypes like SecurityPolicy, CWCOWBlockCIMs,
Container scratch formatting etc. This will come in along
with functional tests in later PRs.
There are some TODO comments in the code which will be
addressed in upcoming PRs as well.

To make this initialization of the gcs-sidecar flow complete,
certain high level code for the policy enforcement have been
brought into this commit from Mahati's changes.
Example: internal/gcs-sidecar/policy.go, internal/gcs-sidecar/host.go
and helper functions in internal/gcs-sidecar/host.go.
Hence adding her as co-author in this commit.
The rest of the policy framework code will be brought in by Mahati
as follow up PRs.

Co-authored-by: <[email protected]>

Signed-off-by: Kirtana Ashok <[email protected]>

Author: kiashok

cmd/gcs-sidecar/main.go

@@ -0,0 +1,241 @@
+//go:build windows
+// +build windows
+
+package main
+
+import (
+	"context"
+	"flag"
+	"fmt"
+	"net"
+	"os"
+
+	"github.com/Microsoft/go-winio"
+	"github.com/Microsoft/hcsshim/internal/gcs/prot"
+	shimlog "github.com/Microsoft/hcsshim/internal/log"
+	"github.com/Microsoft/hcsshim/internal/oc"
+	"github.com/Microsoft/hcsshim/pkg/securitypolicy"
+	"github.com/sirupsen/logrus"
+	"go.opencensus.io/trace"
+	"golang.org/x/sys/windows"
+	"golang.org/x/sys/windows/svc"
+	"golang.org/x/sys/windows/svc/debug"
+
+	sidecar "github.com/Microsoft/hcsshim/internal/gcs-sidecar"
+)
+
+var (
+	defaultLogFile  = "C:\\gcs-sidecar-logs.log"
+	defaultLogLevel = "trace"
+)
+
+type handler struct {
+	fromsvc chan error
+}
+
+// Accepts new connection and closes listener.
+func acceptAndClose(ctx context.Context, l net.Listener) (net.Conn, error) {
+	var conn net.Conn
+	ch := make(chan error)
+	go func() {
+		var err error
+		conn, err = l.Accept()
+		ch <- err
+	}()
+	select {
+	case err := <-ch:
+		l.Close()
+		return conn, err
+	case <-ctx.Done():
+	}
+	l.Close()
+	err := <-ch
+	if err == nil {
+		return conn, err
+	}
+
+	if ctx.Err() != nil {
+		return nil, ctx.Err()
+	}
+	return nil, err
+}
+
+func (h *handler) Execute(args []string, r <-chan svc.ChangeRequest, status chan<- svc.Status) (bool, uint32) {
+	const cmdsAccepted = svc.AcceptStop | svc.AcceptShutdown | svc.Accepted(windows.SERVICE_ACCEPT_PARAMCHANGE)
+
+	status <- svc.Status{State: svc.StartPending, Accepts: 0}
+	// unblock runService()
+	h.fromsvc <- nil
+
+	status <- svc.Status{State: svc.Running, Accepts: cmdsAccepted}
+
+loop:
+	for c := range r {
+		switch c.Cmd {
+		case svc.Interrogate:
+			status <- c.CurrentStatus
+		case svc.Stop, svc.Shutdown:
+			logrus.Println("Shutting service...!")
+			break loop
+		case svc.Pause:
+			status <- svc.Status{State: svc.Paused, Accepts: cmdsAccepted}
+		case svc.Continue:
+			status <- svc.Status{State: svc.Running, Accepts: cmdsAccepted}
+		default:
+			logrus.Printf("Unexpected service control request #%d", c)
+		}
+	}
+
+	status <- svc.Status{State: svc.StopPending}
+	return false, 1
+}
+
+func runService(name string, isDebug bool) error {
+	h := &handler{
+		fromsvc: make(chan error),
+	}
+
+	var err error
+	go func() {
+		if isDebug {
+			err = debug.Run(name, h)
+			if err != nil {
+				logrus.Errorf("Error running service in debug mode.Err: %v", err)
+			}
+		} else {
+			err = svc.Run(name, h)
+			if err != nil {
+				logrus.Errorf("Error running service in Service Control mode.Err %v", err)
+			}
+		}
+		h.fromsvc <- err
+	}()
+
+	// Wait for the first signal from the service handler.
+	logrus.Tracef("waiting for first signal from service handler\n")
+	return <-h.fromsvc
+}
+
+func main() {
+	logLevel := flag.String("loglevel",
+		defaultLogLevel,
+		"Logging Level: trace, debug, info, warning, error, fatal, panic.")
+	logFile := flag.String("logfile",
+		defaultLogFile,
+		"Logging Target. Default is at C:\\gcs-sidecar-logs.log inside UVM")
+
+	flag.Usage = func() {
+		fmt.Fprintf(os.Stderr, "\nUsage of %s:\n", os.Args[0])
+		flag.PrintDefaults()
+		fmt.Fprintf(os.Stderr, "Examples:\n")
+		fmt.Fprintf(os.Stderr, "    %s -loglevel=trace -logfile=C:\\sidecarLogs.log \n", os.Args[0])
+	}
+
+	flag.Parse()
+
+	ctx := context.Background()
+	logFileHandle, err := os.OpenFile(*logFile, os.O_RDWR|os.O_CREATE|os.O_SYNC|os.O_TRUNC, 0666)
+	if err != nil {
+		fmt.Printf("error opening file: %v", err)
+	}
+	defer logFileHandle.Close()
+
+	logrus.AddHook(shimlog.NewHook())
+
+	level, err := logrus.ParseLevel(*logLevel)
+	if err != nil {
+		logrus.Fatal(err)
+	}
+	logrus.SetLevel(level)
+	logrus.SetOutput(logFileHandle)
+	trace.ApplyConfig(trace.Config{DefaultSampler: trace.AlwaysSample()})
+	trace.RegisterExporter(&oc.LogrusExporter{})
+
+	if err := windows.SetStdHandle(windows.STD_ERROR_HANDLE, windows.Handle(logFileHandle.Fd())); err != nil {
+		logrus.WithError(err).Error("error redirecting handle")
+		return
+	}
+	os.Stderr = logFileHandle
+
+	chsrv := make(chan error)
+	go func() {
+		defer close(chsrv)
+
+		if err := runService("gcs-sidecar", false); err != nil {
+			logrus.Errorf("error starting gcs-sidecar service: %v", err)
+		}
+
+		chsrv <- err
+	}()
+
+	select {
+	case <-ctx.Done():
+		logrus.Error("context deadline exceeded")
+		return
+	case r := <-chsrv:
+		if r != nil {
+			logrus.Error(r)
+			return
+		}
+	}
+
+	// 1. Start external server to connect with inbox GCS
+	listener, err := winio.ListenHvsock(&winio.HvsockAddr{
+		VMID:      prot.HvGUIDLoopback,
+		ServiceID: prot.WindowsGcsHvsockServiceID,
+	})
+	if err != nil {
+		logrus.WithError(err).Errorf("error starting listener for sidecar <-> inbox gcs communication")
+		return
+	}
+
+	var gcsListener net.Listener = listener
+	gcsCon, err := acceptAndClose(ctx, gcsListener)
+	if err != nil {
+		logrus.WithError(err).Errorf("error accepting inbox GCS connection")
+		return
+	}
+
+	// 2. Setup connection with external gcs connection started from hcsshim
+	hvsockAddr := &winio.HvsockAddr{
+		VMID:      prot.HvGUIDParent,
+		ServiceID: prot.WindowsSidecarGcsHvsockServiceID,
+	}
+
+	logrus.WithFields(logrus.Fields{
+		"hvsockAddr": hvsockAddr,
+	}).Tracef("Dialing to hcsshim external bridge at address %v", hvsockAddr)
+	shimCon, err := winio.Dial(ctx, hvsockAddr)
+	if err != nil {
+		logrus.WithError(err).Errorf("error dialing hcsshim external bridge")
+		return
+	}
+
+	// gcs-sidecar can be used for non-confidentail hyperv wcow
+	// as well. So we do not always want to check for initialPolicyStance
+	var initialEnforcer securitypolicy.SecurityPolicyEnforcer
+	// TODO (kiashok/Mahati): The initialPolicyStance is set to allow
+	// only for dev. This will eventually be set to allow/deny depending on
+	// on whether SNP is supported or not.
+	initialPolicyStance := "allow"
+	switch initialPolicyStance {
+	case "allow":
+		initialEnforcer = &securitypolicy.OpenDoorSecurityPolicyEnforcer{}
+		logrus.Tracef("initial-policy-stance: allow")
+	case "deny":
+		initialEnforcer = &securitypolicy.ClosedDoorSecurityPolicyEnforcer{}
+		logrus.Tracef("initial-policy-stance: deny")
+	default:
+		logrus.Error("unknown initial-policy-stance")
+	}
+
+	// 3. Create bridge and initializa
+	brdg := sidecar.NewBridge(shimCon, gcsCon, initialEnforcer)
+	brdg.AssignHandlers()
+
+	// 3. Listen and serve for hcsshim requests.
+	err = brdg.ListenAndServeShimRequests()
+	if err != nil {
+		logrus.WithError(err).Errorf("failed to serve request")
+	}
+}