// Copyright 2019 getensh.com. All rights reserved.
// Use of this source code is governed by getensh.com.

package util

import (
	"bytes"
	"crypto/cipher"
	"crypto/des"
)

// CBCDesEncrypt des加密, mode: cbc
func CBCDesEncrypt(key, iv, plainText []byte) ([]byte, error) {
	block, err := des.NewCipher(key)
	if err != nil {
		return nil, err
	}

	blockSize := block.BlockSize()
	origData := pkcs5Padding(plainText, blockSize)
	blockMode := cipher.NewCBCEncrypter(block, iv)
	cryted := make([]byte, len(origData))
	blockMode.CryptBlocks(cryted, origData)
	return cryted, nil
}

// CBCDesDecrypt des解密, mode: cbc
func CBCDesDecrypt(key, iv, cipherText []byte) ([]byte, error) {
	block, err := des.NewCipher(key)
	if err != nil {
		return nil, err
	}

	blockMode := cipher.NewCBCDecrypter(block, iv)
	origData := make([]byte, len(cipherText))
	blockMode.CryptBlocks(origData, cipherText)
	origData = pkcs5UnPadding(origData)
	return origData, nil
}

func pkcs5Padding(src []byte, blockSize int) []byte {
	padding := blockSize - len(src)%blockSize
	padtext := bytes.Repeat([]byte{byte(padding)}, padding)
	return append(src, padtext...)
}

func pkcs5UnPadding(src []byte) []byte {
	length := len(src)
	unpadding := int(src[length-1])
	return src[:(length - unpadding)]
}