An example of finding apk file by its hash

find_file_by_hash.go

package main

import (
	"crypto/md5"
	"flag"
	"fmt"
	"io"
	"log"
	"os"
	"path/filepath"
	"strings"
)

func getHash(location string) (string, error) {
	f, err := os.Open(location)
	if err != nil {
		return "", fmt.Errorf("open %s failed: %w", location, err)
	}
	defer f.Close()

	h := md5.New()
	if _, err := io.Copy(h, f); err != nil {
		return "", fmt.Errorf("copy hashing failed: %w", err)
	}

	return fmt.Sprintf("%x", h.Sum(nil)), nil
}

func main() {
	var hash string
	var dir string
	flag.StringVar(&hash, "hash", "cd3bbabf0b1987526e97ed63c27af5c1", "enter your hash")
	flag.StringVar(&dir, "dir", "/", "enter lookup path")
	flag.Parse()

	fmt.Println("Search file by hash", hash)

	err := filepath.Walk("/",
		func(path string, info os.FileInfo, err error) error {
			if err != nil {
				return err
			}
			if info.IsDir() { // skip directory
				return nil
			}
			if !strings.HasSuffix(path, ".apk") {
				return nil // skip non-apk file
			}
			h, err := getHash(path)
			if err != nil {
				return err
			}

			// break the loop
			if h == hash {
				return fmt.Errorf("%s has hash: %s", path, h)
			}
			return nil
		})
	if err != nil {
		log.Println(err)
	}

}