cmd/containerboot: fix nil pointer exception (cherry-pick of #14357, #14358) (#14359)

* cmd/containerboot: guard kubeClient against nil dereference (#14357)

A method on kc was called unconditionally, even if was not initialized,
leading to a nil pointer dereference when TS_SERVE_CONFIG was set
outside Kubernetes.

Add a guard symmetric with other uses of the kubeClient.

Signed-off-by: Bjorn Neergaard <bjorn@neersighted.com>
(cherry picked from commit 8b1d01161b)

* cmd/containerboot: don't attempt to write kube Secret in non-kube environments (#14358)

Signed-off-by: Irbe Krumina <irbe@tailscale.com>
(cherry picked from commit 0cc071f154)

* cmd/containerboot: don't attempt to patch a Secret field without permissions (#14365)

Signed-off-by: Irbe Krumina <irbe@tailscale.com>
(cherry picked from commit 6e552f66a0)

Updates tailscale/tailscale#14354

cmd/containerboot/kube.go

@@ -24,6 +24,7 @@ import (
 type kubeClient struct {
 	kubeclient.Client
 	stateSecret string
+	canPatch    bool // whether the client has permissions to patch Kubernetes Secrets
 }
 
 func newKubeClient(root string, stateSecret string) (*kubeClient, error) {

cmd/containerboot/main.go

@@ -331,8 +331,10 @@ authLoop:
 		if err := client.SetServeConfig(ctx, new(ipn.ServeConfig)); err != nil {
 			log.Fatalf("failed to unset serve config: %v", err)
 		}
-		if err := kc.storeHTTPSEndpoint(ctx, ""); err != nil {
-			log.Fatalf("failed to update HTTPS endpoint in tailscale state: %v", err)
+		if hasKubeStateStore(cfg) {
+			if err := kc.storeHTTPSEndpoint(ctx, ""); err != nil {
+				log.Fatalf("failed to update HTTPS endpoint in tailscale state: %v", err)
+			}
 		}
 	}
 

cmd/containerboot/serve.go

@@ -72,8 +72,10 @@ func watchServeConfigChanges(ctx context.Context, path string, cdChanged <-chan
 		if err := updateServeConfig(ctx, sc, certDomain, lc); err != nil {
 			log.Fatalf("serve proxy: error updating serve config: %v", err)
 		}
-		if err := kc.storeHTTPSEndpoint(ctx, certDomain); err != nil {
-			log.Fatalf("serve proxy: error storing HTTPS endpoint: %v", err)
+		if kc != nil && kc.canPatch {
+			if err := kc.storeHTTPSEndpoint(ctx, certDomain); err != nil {
+				log.Fatalf("serve proxy: error storing HTTPS endpoint: %v", err)
+			}
 		}
 		prevServeConfig = sc
 	}

cmd/containerboot/settings.go

@@ -214,6 +214,7 @@ func (cfg *settings) setupKube(ctx context.Context, kc *kubeClient) error {
 		return fmt.Errorf("some Kubernetes permissions are missing, please check your RBAC configuration: %v", err)
 	}
 	cfg.KubernetesCanPatch = canPatch
+	kc.canPatch = canPatch
 
 	s, err := kc.GetSecret(ctx, cfg.KubeSecret)
 	if err != nil {