fix(cli): confine agent runtime paths

cmd/elydora/plugins/runtime_paths.go

@@ -0,0 +1,128 @@
+package plugins
+
+import (
+	"fmt"
+	"os"
+	"path/filepath"
+	"regexp"
+	"runtime"
+	"strings"
+)
+
+var windowsDeviceName = regexp.MustCompile(
+	`(?i)^(?:con|prn|aux|nul|com[1-9¹²³]|lpt[1-9¹²³])(?:\.|$)`,
+)
+
+// AgentRuntimeRoot returns the local root for all Elydora agent runtimes.
+func AgentRuntimeRoot() (string, error) {
+	home, err := os.UserHomeDir()
+	if err != nil {
+		return "", fmt.Errorf("resolve home directory: %w", err)
+	}
+	root, err := filepath.Abs(filepath.Join(home, ".elydora"))
+	if err != nil {
+		return "", fmt.Errorf("resolve Elydora runtime root: %w", err)
+	}
+	return root, nil
+}
+
+// ResolveAgentRuntimeDirectory confines an agent ID to one portable path segment.
+func ResolveAgentRuntimeDirectory(agentID string) (string, error) {
+	if invalidAgentDirectoryName(agentID) {
+		return "", fmt.Errorf(
+			"invalid agent ID for local storage: %q must be a single non-empty path segment with a portable file name",
+			agentID,
+		)
+	}
+	root, err := AgentRuntimeRoot()
+	if err != nil {
+		return "", err
+	}
+	candidate := filepath.Join(root, agentID)
+	relative, err := filepath.Rel(root, candidate)
+	if err != nil {
+		return "", fmt.Errorf("resolve agent runtime path for %q: %w", agentID, err)
+	}
+	if relative == "." || relative == ".." || filepath.IsAbs(relative) ||
+		strings.HasPrefix(relative, ".."+string(os.PathSeparator)) ||
+		strings.ContainsRune(relative, os.PathSeparator) {
+		return "", fmt.Errorf("agent ID escapes the local storage directory: %q", agentID)
+	}
+	if _, err := RequirePhysicalDirectory(root); err != nil {
+		return "", err
+	}
+	if _, err := RequirePhysicalDirectory(candidate); err != nil {
+		return "", err
+	}
+	return candidate, nil
+}
+
+func invalidAgentDirectoryName(agentID string) bool {
+	if agentID == "" || agentID == "." || agentID == ".." ||
+		strings.ContainsAny(agentID, `<>:"/\|?*`) ||
+		strings.HasPrefix(agentID, " ") || strings.HasSuffix(agentID, ".") ||
+		strings.HasSuffix(agentID, " ") ||
+		windowsDeviceName.MatchString(agentID) {
+		return true
+	}
+	for _, character := range agentID {
+		if character <= 31 {
+			return true
+		}
+	}
+	return false
+}
+
+// EnsurePrivateDirectory creates an owner-only physical directory.
+func EnsurePrivateDirectory(path string) error {
+	if err := os.MkdirAll(path, 0700); err != nil {
+		return fmt.Errorf("create private directory %s: %w", path, err)
+	}
+	info, err := os.Lstat(path)
+	if err != nil {
+		return fmt.Errorf("inspect private directory %s: %w", path, err)
+	}
+	if info.Mode()&os.ModeSymlink != 0 || !info.IsDir() {
+		return fmt.Errorf("private directory path is not a physical directory: %s", path)
+	}
+	if runtime.GOOS != "windows" {
+		if err := os.Chmod(path, 0700); err != nil {
+			return fmt.Errorf("restrict private directory %s: %w", path, err)
+		}
+	}
+	return nil
+}
+
+// PrepareAgentRuntimeDirectory validates and creates the private runtime path.
+func PrepareAgentRuntimeDirectory(agentID string) (string, error) {
+	root, err := AgentRuntimeRoot()
+	if err != nil {
+		return "", err
+	}
+	agentDirectory, err := ResolveAgentRuntimeDirectory(agentID)
+	if err != nil {
+		return "", err
+	}
+	if err := EnsurePrivateDirectory(root); err != nil {
+		return "", err
+	}
+	if err := EnsurePrivateDirectory(agentDirectory); err != nil {
+		return "", err
+	}
+	return agentDirectory, nil
+}
+
+// RequirePhysicalDirectory reports whether a path is an existing physical directory.
+func RequirePhysicalDirectory(path string) (bool, error) {
+	info, err := os.Lstat(path)
+	if os.IsNotExist(err) {
+		return false, nil
+	}
+	if err != nil {
+		return false, fmt.Errorf("inspect agent runtime directory %s: %w", path, err)
+	}
+	if info.Mode()&os.ModeSymlink != 0 || !info.IsDir() {
+		return false, fmt.Errorf("agent runtime path is not a physical directory: %s", path)
+	}
+	return true, nil
+}