cmd/containerboot,kube,ipn/store/kubestore: allow interactive login on kube, check Secret create perms, allow empty state Secret (#11326)

cmd/containerboot,kube,ipn/store/kubestore: allow interactive login and empty state Secrets, check perms * Allow users to pre-create empty state Secrets * Add a fake internal kube client, test functionality that has dependencies on kube client operations. * Fix an issue where interactive login was not allowed in an edge case where state Secret does not exist * Make the CheckSecretPermissions method report whether we have permissions to create/patch a Secret if it's determined that these operations will be needed Updates tailscale/tailscale#11170 Signed-off-by: Irbe Krumina <irbe@tailscale.com>
2024-04-29 17:03:48 +01:00
parent 1e6cdb7d86
commit 1452faf510
6 changed files with 366 additions and 77 deletions
@@ -8,6 +8,7 @@ package main
 import (
 	"context"
 	"encoding/json"
+	"errors"
 	"fmt"
 	"log"
 	"net/http"
@@ -18,20 +19,6 @@ import (
 	"tailscale.com/tailcfg"
 )

-// findKeyInKubeSecret inspects the kube secret secretName for a data
-// field called "authkey", and returns its value if present.
-func findKeyInKubeSecret(ctx context.Context, secretName string) (string, error) {
-	s, err := kc.GetSecret(ctx, secretName)
-	if err != nil {
-		return "", err
-	}
-	ak, ok := s.Data["authkey"]
-	if !ok {
-		return "", nil
-	}
-	return string(ak), nil
-}
-
 // storeDeviceInfo writes deviceID into the "device_id" data field of the kube
 // secret secretName.
 func storeDeviceInfo(ctx context.Context, secretName string, deviceID tailcfg.StableNodeID, fqdn string, addresses []netip.Prefix) error {
@@ -88,9 +75,59 @@ func deleteAuthKey(ctx context.Context, secretName string) error {
 	return nil
 }

-var kc *kube.Client
+var kc kube.Client

-func initKube(root string) {
+// setupKube is responsible for doing any necessary configuration and checks to
+// ensure that tailscale state storage and authentication mechanism will work on
+// Kubernetes.
+func (cfg *settings) setupKube(ctx context.Context) error {
+	if cfg.KubeSecret == "" {
+		return nil
+	}
+	canPatch, canCreate, err := kc.CheckSecretPermissions(ctx, cfg.KubeSecret)
+	if err != nil {
+		return fmt.Errorf("Some Kubernetes permissions are missing, please check your RBAC configuration: %v", err)
+	}
+	cfg.KubernetesCanPatch = canPatch
+
+	s, err := kc.GetSecret(ctx, cfg.KubeSecret)
+	if err != nil && kube.IsNotFoundErr(err) && !canCreate {
+		return fmt.Errorf("Tailscale state Secret %s does not exist and we don't have permissions to create it. "+
+			"If you intend to store tailscale state elsewhere than a Kubernetes Secret, "+
+			"you can explicitly set TS_KUBE_SECRET env var to an empty string. "+
+			"Else ensure that RBAC is set up that allows the service account associated with this installation to create Secrets.", cfg.KubeSecret)
+	} else if err != nil && !kube.IsNotFoundErr(err) {
+		return fmt.Errorf("Getting Tailscale state Secret %s: %v", cfg.KubeSecret, err)
+	}
+
+	if cfg.AuthKey == "" && !isOneStepConfig(cfg) {
+		if s == nil {
+			log.Print("TS_AUTHKEY not provided and kube secret does not exist, login will be interactive if needed.")
+			return nil
+		}
+		keyBytes, _ := s.Data["authkey"]
+		key := string(keyBytes)
+
+		if key != "" {
+			// This behavior of pulling authkeys from kube secrets was added
+			// at the same time as the patch permission, so we can enforce
+			// that we must be able to patch out the authkey after
+			// authenticating if you want to use this feature. This avoids
+			// us having to deal with the case where we might leave behind
+			// an unnecessary reusable authkey in a secret, like a rake in
+			// the grass.
+			if !cfg.KubernetesCanPatch {
+				return errors.New("authkey found in TS_KUBE_SECRET, but the pod doesn't have patch permissions on the secret to manage the authkey.")
+			}
+			cfg.AuthKey = key
+		} else {
+			log.Print("No authkey found in kube secret and TS_AUTHKEY not provided, login will be interactive if needed.")
+		}
+	}
+	return nil
+}
+
+func initKubeClient(root string) {
 	if root != "/" {
 		// If we are running in a test, we need to set the root path to the fake
 		// service account directory.