EvoBGP/internal/bundle/extract.go

package bundle

import (
	"fmt"
	"os"
	"path/filepath"
	"strings"
)

// WriteExtractedFiles writes payload files from a verified bundle under root (directories created as needed).
func WriteExtractedFiles(root string, v *VerifiedContents) error {
	return WriteExtractedFilesWithLimits(root, v, Limits{})
}

// WriteExtractedFilesWithLimits confines all filesystem operations to an open
// directory handle. Replacing existing files uses unlink + exclusive creation,
// so existing hard links and symlinks cannot redirect writes outside the root.
func WriteExtractedFilesWithLimits(root string, v *VerifiedContents, limits Limits) error {
	l, err := limits.Normalized()
	if err != nil {
		return err
	}
	if v == nil {
		return fmt.Errorf("bundle: nil verified contents")
	}
	if len(v.Manifest.Files) > l.MaxEntries-2 {
		return ErrLimit
	}
	seen := map[string]bool{}
	var total int64
	for _, fe := range v.Manifest.Files {
		if err := validatePath(fe.Path, l.MaxPathBytes); err != nil {
			return err
		}
		if seen[strings.ToLower(fe.Path)] {
			return fmt.Errorf("bundle: duplicate path %q", fe.Path)
		}
		seen[strings.ToLower(fe.Path)] = true
		data, ok := v.Files[fe.Path]
		if !ok {
			return fmt.Errorf("bundle: missing file %q", fe.Path)
		}
		if int64(len(data)) > l.MaxFileBytes || int64(len(data)) > l.MaxExpandedBytes-total {
			return ErrLimit
		}
		total += int64(len(data))
	}
	root = filepath.Clean(root)
	if err := os.MkdirAll(root, 0o755); err != nil {
		return err
	}
	confined, err := os.OpenRoot(root)
	if err != nil {
		return err
	}
	defer func() { _ = confined.Close() }()
	for _, fe := range v.Manifest.Files {
		data, ok := v.Files[fe.Path]
		if !ok {
			return fmt.Errorf("bundle: missing file %q", fe.Path)
		}
		parts := strings.Split(fe.Path, "/")
		for i := 1; i < len(parts); i++ {
			dir := filepath.FromSlash(strings.Join(parts[:i], "/"))
			if err := confined.Mkdir(dir, 0o755); err != nil && !os.IsExist(err) {
				return err
			}
			info, err := confined.Lstat(dir)
			if err != nil {
				return err
			}
			if !info.IsDir() || info.Mode()&os.ModeSymlink != 0 {
				return fmt.Errorf("bundle: unsafe directory %q", dir)
			}
		}
		dest := filepath.FromSlash(fe.Path)
		info, err := confined.Lstat(dest)
		if err == nil {
			if !info.Mode().IsRegular() {
				return fmt.Errorf("bundle: unsafe destination %q", dest)
			}
			if err = confined.Remove(dest); err != nil {
				return err
			}
		} else if !os.IsNotExist(err) {
			return err
		}
		f, err := confined.OpenFile(dest, os.O_WRONLY|os.O_CREATE|os.O_EXCL, 0o644)
		if err != nil {
			return err
		}
		_, writeErr := f.Write(data)
		closeErr := f.Close()
		if writeErr != nil {
			return writeErr
		}
		if closeErr != nil {
			return closeErr
		}
	}
	return nil
}

// FindMainBirdConf returns the first path ending with bird.conf from extracted manifest order.
func (v *VerifiedContents) FindMainBirdConf() string {
	for _, fe := range v.Manifest.Files {
		if strings.HasSuffix(fe.Path, "bird.conf") {
			return fe.Path
		}
	}
	return ""
}