How can I implement robust and secure zip file extraction in Go, addressing potential issues like file descriptor leaks and ZipSlip vulnerabilities?

Effortless Zip File Extraction with Go

Unzipping files in Go can be a breeze with the help of the zip package. By utilizing its capabilities, you can easily extract the contents of compressed archives.

Original Code:

func Unzip(src, dest string) error {
    r, err := zip.OpenReader(src)
    if err != nil {
        return err
    }
    defer r.Close()

    for _, f := range r.File {
        rc, err := f.Open()
        if err != nil {
            return err
        }
        defer rc.Close()

        path := filepath.Join(dest, f.Name)
        if f.FileInfo().IsDir() {
            os.MkdirAll(path, f.Mode())
        } else {
            f, err := os.OpenFile(
                path, os.O_WRONLY|os.O_CREATE|os.O_TRUNC, f.Mode())
            if err != nil {
                return err
            }
            defer f.Close()

            _, err = io.Copy(f, rc)
            if err != nil {
                return err
            }
        }
    }

    return nil
}

Enhanced Code:

To further improve the code and avoid file descriptor issues, consider the following enhancements:

1. Create the destination directory (dest) if it doesn't exist (os.MkdirAll).
2. Encapsulate file extraction and writing in a closure to eliminate stacking of defer .Close() calls.
3. Add error handling to Close() operations.
4. Implement a check for ZipSlip (directory traversal) vulnerabilities.

func Unzip(src, dest string) error {
    r, err := zip.OpenReader(src)
    if err != nil {
        return err
    }
    defer func() {
        if err := r.Close(); err != nil {
            panic(err)
        }
    }()

    os.MkdirAll(dest, 0755)

    extractAndWriteFile := func(f *zip.File) error {
        rc, err := f.Open()
        if err != nil {
            return err
        }
        defer func() {
            if err := rc.Close(); err != nil {
                panic(err)
            }
        }()

        path := filepath.Join(dest, f.Name)

        if !strings.HasPrefix(path, filepath.Clean(dest) + string(os.PathSeparator)) {
            return fmt.Errorf("illegal file path: %s", path)
        }

        if f.FileInfo().IsDir() {
            os.MkdirAll(path, f.Mode())
        } else {
            os.MkdirAll(filepath.Dir(path), f.Mode())
            f, err := os.OpenFile(path, os.O_WRONLY|os.O_CREATE|os.O_TRUNC, f.Mode())
            if err != nil {
                return err
            }
            defer func() {
                if err := f.Close(); err != nil {
                    panic(err)
                }
            }()

            _, err = io.Copy(f, rc)
            if err != nil {
                return err
            }
        }
        return nil
    }

    for _, f := range r.File {
        err := extractAndWriteFile(f)
        if err != nil {
            return err
        }
    }

    return nil
}

With these enhancements, you can now efficiently and securely unzip files in Go.

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