ipn/ipnlocal: fix cert storage in Kubernetes

We were checking against the wrong directory, instead if we
have a custom store configured just use that.

Fixes #7588
Fixes #7665

Signed-off-by: Maisem Ali <maisem@tailscale.com>
(cherry picked from commit 8a11f76a0d)

cmd/tailscaled/depaware.txt

@@ -212,7 +212,7 @@ tailscale.com/cmd/tailscaled dependencies: (generated by github.com/tailscale/de
         tailscale.com/ipn/ipnstate                                   from tailscale.com/control/controlclient+
         tailscale.com/ipn/localapi                                   from tailscale.com/ipn/ipnserver
         tailscale.com/ipn/policy                                     from tailscale.com/ipn/ipnlocal
-        tailscale.com/ipn/store                                      from tailscale.com/cmd/tailscaled
+        tailscale.com/ipn/store                                      from tailscale.com/cmd/tailscaled+
    L    tailscale.com/ipn/store/awsstore                             from tailscale.com/ipn/store
    L    tailscale.com/ipn/store/kubestore                            from tailscale.com/ipn/store
         tailscale.com/ipn/store/mem                                  from tailscale.com/ipn/store+

ipn/ipnlocal/cert.go

@@ -35,6 +35,8 @@ import (
 	"tailscale.com/hostinfo"
 	"tailscale.com/ipn"
 	"tailscale.com/ipn/ipnstate"
+	"tailscale.com/ipn/store"
+	"tailscale.com/ipn/store/mem"
 	"tailscale.com/types/logger"
 	"tailscale.com/version"
 	"tailscale.com/version/distro"
@@ -150,13 +152,21 @@ type certStore interface {
 var errCertExpired = errors.New("cert expired")
 
 func (b *LocalBackend) getCertStore() (certStore, error) {
+	switch b.store.(type) {
+	case *store.FileStore:
+	case *mem.Store:
+	default:
+		if hostinfo.GetEnvType() == hostinfo.Kubernetes {
+			// We're running in Kubernetes with a custom StateStore,
+			// use that instead of the cert directory.
+			// TODO(maisem): expand this to other environments?
+			return certStateStore{StateStore: b.store}, nil
+		}
+	}
 	dir, err := b.certDir()
 	if err != nil {
 		return nil, err
 	}
-	if hostinfo.GetEnvType() == hostinfo.Kubernetes && dir == "/tmp" {
-		return certStateStore{StateStore: b.store}, nil
-	}
 	return certFileStore{dir: dir}, nil
 }
 

ipn/ipnlocal/local.go

@@ -298,7 +298,7 @@ func NewLocalBackend(logf logger.Logf, logid string, store ipn.StateStore, diale
 		statsLogf:      logger.LogOnChange(logf, 5*time.Minute, time.Now),
 		e:              e,
 		pm:             pm,
-		store:          pm.Store(),
+		store:          store,
 		dialer:         dialer,
 		backendLogID:   logid,
 		state:          ipn.NoState,