feat: initial goget release — modern IPv6-first download utility

internal/archive/tar.go

@@ -0,0 +1,134 @@
+//go:build linux || freebsd
+// +build linux freebsd
+
+package archive
+
+import (
+	"archive/tar"
+	"fmt"
+	"io"
+	"os"
+	"path/filepath"
+	"strings"
+	"time"
+)
+
+type tarExtractor struct{ *BaseExtractor }
+
+func NewTarExtractor() *tarExtractor {
+	return &tarExtractor{NewBaseExtractor("tar", []string{".tar"})}
+}
+
+// Extract extracts a tar archive into destDir (streaming-friendly)
+func (t *tarExtractor) Extract(r io.Reader, destDir string) error {
+	tr := tar.NewReader(r)
+
+	for {
+		header, err := tr.Next()
+		if err == io.EOF {
+			break
+		}
+		if err != nil {
+			return fmt.Errorf("failed to read tar header: %w", err)
+		}
+
+		if err := t.extractEntry(header, tr, destDir); err != nil {
+			return err
+		}
+	}
+
+	return nil
+}
+
+// extractEntry extracts a single entry from a tar archive
+func (t *tarExtractor) extractEntry(header *tar.Header, r io.Reader, destDir string) error {
+	// Sanitize path to prevent tar-slip attacks
+	cleanName := filepath.Clean(header.Name)
+	if strings.HasPrefix(cleanName, "..") || filepath.IsAbs(cleanName) {
+		return fmt.Errorf("unsafe path in tar: %s", header.Name)
+	}
+
+	targetPath := filepath.Join(destDir, cleanName)
+
+	switch header.Typeflag {
+	case tar.TypeDir:
+		// Create directory with original permissions
+		return os.MkdirAll(targetPath, os.FileMode(header.Mode))
+
+	case tar.TypeReg:
+		// Create parent directories
+		if err := os.MkdirAll(filepath.Dir(targetPath), 0755); err != nil {
+			return err
+		}
+
+		// Create file with original permissions (mask setuid/setgid/sticky)
+		mode := os.FileMode(header.Mode) & 0777
+		file, err := os.OpenFile(targetPath, os.O_CREATE|os.O_WRONLY|os.O_TRUNC, mode)
+		if err != nil {
+			return err
+		}
+		defer file.Close()
+
+		// Copy contents
+		if _, err := io.Copy(file, r); err != nil {
+			return err
+		}
+
+		// Restore timestamps
+		atime := header.AccessTime
+		if atime.IsZero() {
+			atime = time.Now()
+		}
+		mtime := header.ModTime
+		if mtime.IsZero() {
+			mtime = time.Now()
+		}
+		if err := os.Chtimes(targetPath, atime, mtime); err != nil {
+			// Non-fatal
+		}
+
+		return nil
+
+	case tar.TypeSymlink:
+		// Validate symlink target against path traversal
+		linkTarget := filepath.Clean(header.Linkname)
+		if filepath.IsAbs(linkTarget) || strings.HasPrefix(linkTarget, "..") {
+			return fmt.Errorf("symlink target outside extraction directory: %s", header.Linkname)
+		}
+		if err := os.MkdirAll(filepath.Dir(targetPath), 0755); err != nil {
+			return err
+		}
+		os.Remove(targetPath)
+		return os.Symlink(linkTarget, targetPath)
+
+	case tar.TypeLink:
+		// Hard link - validate target stays within destDir to prevent path traversal
+		cleanTarget := filepath.Clean(header.Linkname)
+		if filepath.IsAbs(cleanTarget) || strings.HasPrefix(cleanTarget, "..") {
+			return fmt.Errorf("hard link target outside extraction directory: %s", header.Linkname)
+		}
+		linkTarget := filepath.Join(destDir, cleanTarget)
+		// Ensure resolved path does not escape destDir
+		if !strings.HasPrefix(linkTarget, destDir+string(filepath.Separator)) && linkTarget != destDir {
+			return fmt.Errorf("hard link target outside extraction directory: %s", header.Linkname)
+		}
+		if err := os.MkdirAll(filepath.Dir(targetPath), 0755); err != nil {
+			return err
+		}
+		return os.Link(linkTarget, targetPath)
+
+	case tar.TypeChar, tar.TypeBlock:
+		// Device files - skip with warning (requires root)
+		return nil
+
+	case tar.TypeFifo:
+		// FIFO - skip (platform-specific)
+		return nil
+
+	default:
+		// Unknown type - skip
+		return nil
+	}
+}
+
+func init() { Register(NewTarExtractor()) }