add SVID check to agent health check

Signed-off-by: James Ribe <manbeardo@gmail.com>

pkg/agent/agent.go

@@ -44,7 +44,8 @@ const (
 )
 
 type Agent struct {
-	c *Config
+	c   *Config
+	sto storage.Storage
 }
 
 // Run the agent
@@ -56,7 +57,8 @@ func (a *Agent) Run(ctx context.Context) error {
 		return err
 	}
 
-	sto, err := storage.Open(a.c.DataDir)
+	var err error
+	a.sto, err = storage.Open(a.c.DataDir)
 	if err != nil {
 		return fmt.Errorf("failed to open storage: %w", err)
 	}
@@ -109,7 +111,7 @@ func (a *Agent) Run(ctx context.Context) error {
 		)
 
 		for {
-			as, err = a.attest(ctx, sto, cat, metrics, nodeAttestor)
+			as, err = a.attest(ctx, a.sto, cat, metrics, nodeAttestor)
 			if err == nil {
 				break
 			}
@@ -136,15 +138,15 @@ func (a *Agent) Run(ctx context.Context) error {
 			}
 		}
 	} else {
-		as, err = a.attest(ctx, sto, cat, metrics, nodeAttestor)
+		as, err = a.attest(ctx, a.sto, cat, metrics, nodeAttestor)
 		if err != nil {
 			return err
 		}
 	}
 
 	svidStoreCache := a.newSVIDStoreCache()
 
-	manager, err := a.newManager(ctx, sto, cat, metrics, as, svidStoreCache, nodeAttestor)
+	manager, err := a.newManager(ctx, a.sto, cat, metrics, as, svidStoreCache, nodeAttestor)
 	if err != nil {
 		return err
 	}
@@ -389,11 +391,14 @@ func (a *Agent) waitForTestDial(ctx context.Context) error {
 
 // CheckHealth is used as a top-level health check for the agent.
 func (a *Agent) CheckHealth() health.State {
-	err := a.checkWorkloadAPI()
-
-	// Both liveness and readiness checks are done by
-	// agents ability to create new Workload API client
-	// for the X509SVID service.
+	err := errors.Join(
+		a.checkWorkloadAPI(),
+		a.checkSVID(),
+	)
+
+	// Both liveness and readiness checks verify that:
+	// - the workload API endpoint is available
+	// - the agent has an SVID
 	// TODO: Better live check for agent.
 	return health.State{
 		Ready: err == nil,
@@ -407,6 +412,20 @@ func (a *Agent) CheckHealth() health.State {
 	}
 }
 
+func (a *Agent) checkSVID() error {
+	if a.sto == nil {
+		return fmt.Errorf("storage not initialized")
+	}
+	svid, _, err := a.sto.LoadSVID()
+	if err != nil {
+		return fmt.Errorf("loading SVID: %w", err)
+	}
+	if svid == nil {
+		return fmt.Errorf("SVID is nil")
+	}
+	return nil
+}
+
 func (a *Agent) checkWorkloadAPI() error {
 	clientOption, err := util.GetWorkloadAPIClientOption(a.c.BindAddress)
 	if err != nil {