Adding upstream version 0.28.1.

Signed-off-by: Daniel Baumann <daniel@debian.org>

tools/archive/extract.go

@@ -0,0 +1,77 @@
+package archive
+
+import (
+	"archive/zip"
+	"fmt"
+	"io"
+	"os"
+	"path/filepath"
+	"strings"
+)
+
+// Extract extracts the zip archive at "src" to "dest".
+//
+// Note that only dirs and regular files will be extracted.
+// Symbolic links, named pipes, sockets, or any other irregular files
+// are skipped because they come with too many edge cases and ambiguities.
+func Extract(src, dest string) error {
+	zr, err := zip.OpenReader(src)
+	if err != nil {
+		return err
+	}
+	defer zr.Close()
+
+	// normalize dest path to check later for Zip Slip
+	dest = filepath.Clean(dest) + string(os.PathSeparator)
+
+	for _, f := range zr.File {
+		err := extractFile(f, dest)
+		if err != nil {
+			return err
+		}
+	}
+
+	return nil
+}
+
+// extractFile extracts the provided zipFile into "basePath/zipFileName" path,
+// creating all the necessary path directories.
+func extractFile(zipFile *zip.File, basePath string) error {
+	path := filepath.Join(basePath, zipFile.Name)
+
+	// check for Zip Slip
+	if !strings.HasPrefix(path, basePath) {
+		return fmt.Errorf("invalid file path: %s", path)
+	}
+
+	r, err := zipFile.Open()
+	if err != nil {
+		return err
+	}
+	defer r.Close()
+
+	// allow only dirs or regular files
+	if zipFile.FileInfo().IsDir() {
+		if err := os.MkdirAll(path, os.ModePerm); err != nil {
+			return err
+		}
+	} else if zipFile.FileInfo().Mode().IsRegular() {
+		// ensure that the file path directories are created
+		if err := os.MkdirAll(filepath.Dir(path), os.ModePerm); err != nil {
+			return err
+		}
+
+		f, err := os.OpenFile(path, os.O_WRONLY|os.O_CREATE|os.O_TRUNC, zipFile.Mode())
+		if err != nil {
+			return err
+		}
+		defer f.Close()
+
+		_, err = io.Copy(f, r)
+		if err != nil {
+			return err
+		}
+	}
+
+	return nil
+}