fix state store SetAction panic

The state store SetAction did not correctly cover the case where a nil action is passed as parameter. The unenroll handler might pass a nil action if the unenroll is a auto-unenroll, that means, it does not come from fleet

Also the unenroll handler does checks for a nil state store anymore, it assumes it's valid just as it does for all other dependencies.

changelog/fragments/1725523126-fix-state-store-SetAction-panic.yaml

@@ -0,0 +1,32 @@
+# Kind can be one of:
+# - breaking-change: a change to previously-documented behavior
+# - deprecation: functionality that is being removed in a later release
+# - bug-fix: fixes a problem in a previous version
+# - enhancement: extends functionality but does not break or fix existing behavior
+# - feature: new functionality
+# - known-issue: problems that we are aware of in a given version
+# - security: impacts on the security of a product or a user’s deployment.
+# - upgrade: important information for someone upgrading from a prior version
+# - other: does not fit into any of the other categories
+kind: bug-fix
+
+# Change summary; a 80ish characters long description of the change.
+summary: Fix the Elastic Agent crashing when self unenrolling due to too many authentication failures against Fleet Server
+
+# Long description; in case the summary is not enough to describe the change
+# this field accommodate a description without length limits.
+# NOTE: This field will be rendered only for breaking-change and known-issue kinds at the moment.
+#description:
+
+# Affected component; a word indicating the component this changeset affects.
+component: state-store
+
+# PR URL; optional; the PR number that added the changeset.
+# If not present is automatically filled by the tooling finding the PR where this changelog fragment has been added.
+# NOTE: the tooling supports backports, so it's able to fill the original PR number instead of the backport PR number.
+# Please provide it if you are adding a fragment for a different PR.
+#pr: https://github.com/owner/repo/1234
+
+# Issue URL; optional; the GitHub issue related to this changeset (either closes or is part of).
+# If not present is automatically filled by the tooling with the issue linked to the PR number.
+issue: https://github.com/elastic/elastic-agent/issues/5434

internal/pkg/agent/application/actions/handlers/handler_action_unenroll.go

@@ -92,12 +92,10 @@ func (h *Unenroll) Handle(ctx context.Context, a fleetapi.Action, acker acker.Ac
 	unenrollPolicy := newPolicyChange(ctx, config.New(), a, acker, true)
 	h.ch <- unenrollPolicy
 
-	if h.stateStore != nil {
-		// backup action for future start to avoid starting fleet gateway loop
-		h.stateStore.SetAction(a)
-		if err := h.stateStore.Save(); err != nil {
-			h.log.Warnf("Failed to update state store: %v", err)
-		}
+	// backup action for future start to avoid starting fleet gateway loop
+	h.stateStore.SetAction(a)
+	if err := h.stateStore.Save(); err != nil {
+		h.log.Warnf("Failed to update state store: %v", err)
 	}
 
 	unenrollCtx, cancel := context.WithTimeout(ctx, unenrollTimeout)

internal/pkg/agent/application/actions/handlers/handler_action_unenroll_test.go

@@ -6,12 +6,15 @@ package handlers
 
 import (
 	"context"
+	"path/filepath"
 	"sync/atomic"
 	"testing"
 
 	"github.com/elastic/elastic-agent-client/v7/pkg/client"
 	"github.com/elastic/elastic-agent-client/v7/pkg/proto"
 	"github.com/elastic/elastic-agent/internal/pkg/agent/application/coordinator"
+	"github.com/elastic/elastic-agent/internal/pkg/agent/storage"
+	"github.com/elastic/elastic-agent/internal/pkg/agent/storage/store"
 	"github.com/elastic/elastic-agent/internal/pkg/fleetapi"
 	"github.com/elastic/elastic-agent/pkg/component"
 	"github.com/elastic/elastic-agent/pkg/component/runtime"
@@ -105,7 +108,13 @@ func TestActionUnenrollHandler(t *testing.T) {
 		}
 	}()
 
-	handler := NewUnenroll(log, coord, ch, nil, nil)
+	storePath := filepath.Join(t.TempDir(), "state.json")
+	s, err := storage.NewDiskStore(storePath)
+	require.NoError(t, err, "failed creating DiskStore")
+
+	st, err := store.NewStateStore(log, s)
+	require.NoError(t, err)
+	handler := NewUnenroll(log, coord, ch, nil, st)
 
 	getTamperProtectionFunc := func(enabled bool) func() bool {
 		return func() bool {
@@ -119,9 +128,14 @@ func TestActionUnenrollHandler(t *testing.T) {
 		wantErr              error // Handler error
 		wantPerformedActions int64
 		tamperProtectionFn   func() bool
+		autoUnenroll         bool
 	}{
 		{
-			name: "no running components",
+			name: "fleet unenroll with no running components",
+		},
+		{
+			name:         "auto unenroll with no running components",
+			autoUnenroll: true,
 		},
 		{
 			name: "endpoint no dispatch",
@@ -200,10 +214,17 @@ func TestActionUnenrollHandler(t *testing.T) {
 				handler.tamperProtectionFn = tc.tamperProtectionFn
 			}
 
-			err := handler.Handle(ctx, action, acker)
+			a := new(fleetapi.ActionUnenroll)
+			*a = *action
+			if tc.autoUnenroll {
+				a.IsDetected = true
+			}
+			err := handler.Handle(ctx, a, acker)
 
 			require.ErrorIs(t, err, tc.wantErr)
-			if tc.wantErr == nil {
+
+			// autoUnenroll isn't acked
+			if tc.wantErr == nil && !tc.autoUnenroll {
 				require.Len(t, acker.Acked, 1)
 			}
 			require.Equal(t, tc.wantPerformedActions, coord.performedActions.Load())

internal/pkg/agent/storage/store/state_store.go

@@ -10,6 +10,7 @@ import (
 	"encoding/json"
 	"fmt"
 	"io"
+	"reflect"
 	"sync"
 
 	"github.com/elastic/elastic-agent/internal/pkg/agent/storage"
@@ -169,6 +170,18 @@ func (s *StateStore) SetAction(a fleetapi.Action) {
 	s.mx.Lock()
 	defer s.mx.Unlock()
 
+	if a == nil || reflect.ValueOf(a).IsNil() {
+		s.log.Debugf("trying to set an nil '%T' action, ignoring the action", a)
+		return
+	}
+
+	// the reflect.ValueOf(v).IsNil() is required as the type of 'v' on switch
+	// clause with multiple types will, in this case, preserve the original type.
+	// See details on https://go.dev/ref/spec#Type_switches
+	// Without using reflect accessing the concret type stored in the interface
+	// isn't possible and as a is of type fleetapi.Action and has a concrete
+	// value, a is never nil, neither v is nil as it has the same type of a
+	// on both clauses.
 	switch v := a.(type) {
 	// If any new action type is added, don't forget to update the method's
 	// description.

internal/pkg/agent/storage/store/state_store_test.go

@@ -61,7 +61,93 @@ func createAgentVaultAndSecret(t *testing.T, ctx context.Context, tempDir string
 }
 
 func runTestStateStore(t *testing.T, ackToken string) {
-	log, _ := logger.New("state_store", false)
+	log, _ := logger.NewTesting("state_store")
+
+	t.Run("SetAction corner case", func(t *testing.T) {
+
+		t.Run("nil fleetapi.Action", func(t *testing.T) {
+			var action fleetapi.Action
+
+			storePath := filepath.Join(t.TempDir(), "state.json")
+			s, err := storage.NewDiskStore(storePath)
+			require.NoError(t, err, "failed creating DiskStore")
+
+			store, err := NewStateStore(log, s)
+			require.NoError(t, err)
+			require.Nil(t, store.Action())
+
+			store.SetAction(action)
+			store.SetAckToken(ackToken)
+			err = store.Save()
+			require.NoError(t, err)
+
+			assert.Empty(t, store.Action())
+			assert.Empty(t, store.Queue())
+			assert.Equal(t, ackToken, store.AckToken())
+		})
+
+		t.Run("nil concrete and accepted action", func(t *testing.T) {
+			var actionUnenroll *fleetapi.ActionUnenroll
+			actionPolicyChange := &fleetapi.ActionPolicyChange{
+				ActionID: "abc123",
+			}
+
+			storePath := filepath.Join(t.TempDir(), "state.json")
+			s, err := storage.NewDiskStore(storePath)
+			require.NoError(t, err, "failed creating DiskStore")
+
+			store, err := NewStateStore(log, s)
+			require.NoError(t, err)
+			require.Nil(t, store.Action())
+
+			// 1st set an action
+			store.SetAction(actionPolicyChange)
+			store.SetAckToken(ackToken)
+			err = store.Save()
+			require.NoError(t, err)
+
+			// then try to set a nil action
+			store.SetAction(actionUnenroll)
+			store.SetAckToken(ackToken)
+			err = store.Save()
+			require.NoError(t, err)
+
+			assert.Equal(t, actionPolicyChange, store.Action())
+			assert.Empty(t, store.Queue())
+			assert.Equal(t, ackToken, store.AckToken())
+		})
+
+		t.Run("nil concrete and ignored action", func(t *testing.T) {
+			var actionUnknown *fleetapi.ActionUnknown
+			actionPolicyChange := &fleetapi.ActionPolicyChange{
+				ActionID: "abc123",
+			}
+
+			storePath := filepath.Join(t.TempDir(), "state.json")
+			s, err := storage.NewDiskStore(storePath)
+			require.NoError(t, err, "failed creating DiskStore")
+
+			store, err := NewStateStore(log, s)
+			require.NoError(t, err)
+			require.Nil(t, store.Action())
+
+			// 1st set an action
+			store.SetAction(actionPolicyChange)
+			store.SetAckToken(ackToken)
+			err = store.Save()
+			require.NoError(t, err)
+
+			// then try to set a nil action
+			store.SetAction(actionUnknown)
+			store.SetAckToken(ackToken)
+			err = store.Save()
+			require.NoError(t, err)
+
+			assert.Equal(t, actionPolicyChange, store.Action())
+			assert.Empty(t, store.Queue())
+			assert.Equal(t, ackToken, store.AckToken())
+		})
+	})
 
 	t.Run("store is not dirty on successful save", func(t *testing.T) {
 		storePath := filepath.Join(t.TempDir(), "state.json")