fix: address Copilot PR review comments

- toast.js: fix enforceMaxToasts() infinite loop by splicing the toast from
  activeToasts synchronously before calling dismiss(), so the array length
  decreases each iteration
- apt_runner.go: guard GetUpdateLog against panic when id < 8 chars; return
  an error instead of slicing out of bounds
- Remove toast.test.html from static/ (publicly served); test harness should
  not ship in production builds
- Add validateSnapshotID() to reject snapshot IDs containing path separators
  or other unsafe characters, preventing path traversal in updates.go,
  apt_runner.go, and pm_apt.go
- Restore systemd hardening: add ProtectHome=read-only, PrivateTmp=true, and
  ProtectKernelTunables=true while keeping NoNewPrivileges=false and omitting
  ProtectSystem=strict (agent needs write access to /etc and /var)

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

Author: sarg3nt

gearbox-agent/deploy/gearbox-agent.service

@@ -26,11 +26,14 @@ Restart=always
 RestartSec=5
 
 # Security hardening
-# Note: ProtectSystem is intentionally not set to "strict" because gearbox-agent
-# needs broad system access for package management (apt install/upgrade),
-# service control, HAProxy config, certificate management, and system reboots.
+# Note: ProtectSystem=strict cannot be used because gearbox-agent needs write
+# access to /etc (HAProxy config, certificates) and /var (package management,
+# data dir). ProtectHome=read-only is set since the agent runs as root and only
+# needs read access to home directories.
 NoNewPrivileges=false
-ProtectHome=no
+ProtectHome=read-only
+PrivateTmp=true
+ProtectKernelTunables=true
 
 # Logging
 StandardOutput=journal

gearbox-agent/internal/gears/updates/apt_runner.go

@@ -397,6 +397,9 @@ func (r *AptRunner) failOperation(op *AptOperation, errorMsg string) {
 
 // StartRestore begins a streaming snapshot restore operation.
 func (r *AptRunner) StartRestore(snapshotID string) (string, error) {
+	if err := validateSnapshotID(snapshotID); err != nil {
+		return "", err
+	}
 	operationID := uuid.New().String()
 	ctx, cancel := context.WithCancel(context.Background())
 
@@ -674,6 +677,9 @@ func (r *AptRunner) ListUpdateLogs(limit int) ([]UpdateLog, error) {
 
 // GetUpdateLog returns a specific update log with full output.
 func (r *AptRunner) GetUpdateLog(id string) (*UpdateLog, error) {
+	if len(id) < 8 {
+		return nil, fmt.Errorf("invalid log ID")
+	}
 	entries, err := os.ReadDir(updateLogsDir)
 	if err != nil {
 		return nil, fmt.Errorf("failed to read update logs directory: %w", err)

gearbox-agent/internal/gears/updates/pm_apt.go

@@ -482,6 +482,9 @@ func (a *aptPackageManager) CreateSnapshot(reason string) (*AptSnapshot, error)
 }
 
 func (a *aptPackageManager) RestoreSnapshot(snapshotID string) error {
+	if err := validateSnapshotID(snapshotID); err != nil {
+		return err
+	}
 	snapshotDir := "/var/lib/gearbox-agent/snapshots"
 	snapshotFile := fmt.Sprintf("%s/%s.selections", snapshotDir, snapshotID)
 

gearbox-agent/internal/gears/updates/updates.go

@@ -300,6 +300,17 @@ func (c *UpdatesCollector) CancelReboot() error {
 
 // --- Snapshot Management ---
 
+// validSnapshotID matches only safe snapshot IDs (timestamp + hex suffix, no path separators).
+var validSnapshotID = regexp.MustCompile(`^[A-Za-z0-9_-]+$`)
+
+// validateSnapshotID returns an error if id is empty or contains path-unsafe characters.
+func validateSnapshotID(id string) error {
+	if id == "" || !validSnapshotID.MatchString(id) {
+		return fmt.Errorf("invalid snapshot ID")
+	}
+	return nil
+}
+
 // CreateSnapshot creates a package snapshot for rollback capability.
 // The snapshot format depends on the active package manager.
 func (c *UpdatesCollector) CreateSnapshot(reason string) (*AptSnapshot, error) {
@@ -421,6 +432,9 @@ func computeDowngrades(versionsFile string) []string {
 
 // DeleteSnapshot removes a snapshot.
 func (c *UpdatesCollector) DeleteSnapshot(snapshotID string) error {
+	if err := validateSnapshotID(snapshotID); err != nil {
+		return err
+	}
 	snapshotDir := "/var/lib/gearbox-agent/snapshots"
 
 	selectionsPath := fmt.Sprintf("%s/%s.selections", snapshotDir, snapshotID)
@@ -461,6 +475,9 @@ type SnapshotPreview struct {
 
 // PreviewRestore computes what changes restoring a snapshot would make without applying them.
 func (c *UpdatesCollector) PreviewRestore(snapshotID string) (*SnapshotPreview, error) {
+	if err := validateSnapshotID(snapshotID); err != nil {
+		return nil, err
+	}
 	snapshotDir := "/var/lib/gearbox-agent/snapshots"
 	selectionsFile := fmt.Sprintf("%s/%s.selections", snapshotDir, snapshotID)
 	versionsFile := fmt.Sprintf("%s/%s.versions", snapshotDir, snapshotID)

gearbox/static/js/utils/toast.js

@@ -319,8 +319,10 @@
 
 	function enforceMaxToasts() {
 		while (activeToasts.length > DEFAULTS.maxToasts) {
-			// Remove the oldest toast (first in array)
-			dismiss(activeToasts[0]);
+			// Splice synchronously so the length decreases each iteration,
+			// then dismiss (which animates out and does a no-op splice later).
+			var oldest = activeToasts.splice(0, 1)[0];
+			dismiss(oldest);
 		}
 	}