Golang des-cbc

package descrypt

import (
	"bytes"
	"crypto/cipher"
	"crypto/des"
	"crypto/md5"
	"encoding/base64"
	"encoding/hex"
	"fmt"
	"net/url"
	"strconv"
	"strings"
	"time"
)

func PKCS5Padding(ciphertext []byte, blockSize int) []byte {
    
	padding := blockSize - len(ciphertext)%blockSize
	padtext := bytes.Repeat([]byte{
    byte(padding)}, padding)
	return append(ciphertext, padtext...)
}

func PKCS5UnPadding(origData []byte) []byte {
    
	length := len(origData)
	unpadding := int(origData[length-1])
	return origData[:(length - unpadding)]
}

func HexToByte(hex string) []byte {
    
	length := len(hex) / 2
	slice := make([]byte, length)
	rs := []rune(hex)
	for i := 0; i < length; i++ {
    
		s := string(rs[i*2 : i*2+2])
		value, _ := strconv.ParseInt(s, 16, 10)
		slice[i] = byte(value & 0xFF)
	}
	return slice
}

func DesEncryptHash(key string, src string) string {
    
	m := md5.New()
	m.Write([]byte(src))
	data := string(HexToByte(hex.EncodeToString(m.Sum(nil)))) + src
	return DesEncrypt(key, []byte(data))
}

func DesEncrypt(key string, data []byte) string {
    
	keyByte := HexToByte(key[:16])
	iv := HexToByte(key[16:])
	block, err := des.NewCipher(keyByte)
	if err != nil {
    
		panic(err)
	}
	data = PKCS5Padding(data, block.BlockSize())
	mode := cipher.NewCBCEncrypter(block, iv)
	out := make([]byte, len(data))
	mode.CryptBlocks(out, data)
	encoded := base64.StdEncoding.EncodeToString(out)
	return encoded
}

func DesDecryptHash(key string, src string) string {
    
	dec := DesDecrypt(key, src)
	res := dec[16:]
	m := md5.New()
	m.Write([]byte(res))
	mm := hex.EncodeToString(m.Sum(nil))
	h := hex.EncodeToString([]byte(dec[:16]))
	if mm != h {
    
		return ""
	}
	return res
}

func DesDecrypt(key, src string) string {
    
	keyByte := HexToByte(key[:16])
	iv := HexToByte(key[16:])
	enc, _ := base64.StdEncoding.DecodeString(src)
	block, err := des.NewCipher(keyByte)
	if err != nil {
    
		panic(err)
	}
	mode := cipher.NewCBCDecrypter(block, iv)
	plaintext := make([]byte, len(enc))
	mode.CryptBlocks(plaintext, enc)
	plaintext = PKCS5UnPadding(plaintext)
	return string(plaintext)
}