// pkcs7Padding 填充
func pkcs7Padding(data []byte, blockSize int) []byte {
    //判斷缺少幾位長度。最少1，最多 blockSize
    padding := blockSize - len(data)%blockSize
    //補足位數(shù)。把切片[]byte{byte(padding)}復(fù)制padding個
    padText := bytes.Repeat([]byte{byte(padding)}, padding)
    return append(data, padText...)
}

// pkcs7UnPadding 移除
func pkcs7UnPadding(data []byte) ([]byte, error) {
    length := len(data)
    if length == 0 {
        return nil, errors.New("加密字符串錯誤！")
    }
    //獲取填充的個數(shù)
    unPadding := int(data[length-1])
    return data[:(length - unPadding)], nil
}

// AesEncrypt 加密
func AesEncrypt(data []byte, key []byte) ([]byte, error) {    
    // NewCipher creates and returns a new cipher.Block. The key argument should be the AES key, either 16, 24, or 32 bytes to select AES-128, AES-192, or AES-256.
    block, err := aes.NewCipher(key)
    if err != nil {
        return nil, err
    }
    //判斷加密快的大小
    blockSize := block.BlockSize()
    //填充
    encryptBytes := pkcs7Padding(data, blockSize)
    //初始化加密數(shù)據(jù)接收切片
    crypted := make([]byte, len(encryptBytes))
    //使用cbc加密模式
    blockMode := cipher.NewCBCEncrypter(block, key[:blockSize])
    //執(zhí)行加密
    blockMode.CryptBlocks(crypted, encryptBytes)
    return crypted, nil
}

// AesDecrypt 解密
func AesDecrypt(data []byte, key []byte) ([]byte, error) {
    block, err := aes.NewCipher(key)
    if err != nil {
        return nil, err
    }
    //獲取塊的大小
    blockSize := block.BlockSize()
    //使用cbc
    blockMode := cipher.NewCBCDecrypter(block, key[:blockSize])
    //初始化解密數(shù)據(jù)接收切片
    crypted := make([]byte, len(data))
    //執(zhí)行解密
    blockMode.CryptBlocks(crypted, data)
    //去填充
    crypted, err = pkcs7UnPadding(crypted)
    if err != nil {
        return nil, err
    }
    return crypted, nil
}

func EncryptFile(fileName string) (err error) {
    f, err := os.Open(fileName)
    if err != nil {
        fmt.Println("未找到文件")
        return
    }
    defer f.Close()

    fInfo, _ := f.Stat()
    fLen := fInfo.Size()
    fmt.Println("待處理文件大小:", fLen)
    maxLen := 1024 * 1024 * 100 //100mb  每 100mb 進行加密一次
    var forNum int64 = 0
    getLen := fLen

    if fLen > int64(maxLen) {
        getLen = int64(maxLen)
        forNum = fLen / int64(maxLen)
        fmt.Println("需要加密次數(shù)：", forNum+1)
    }
    // encryptd to file
    ff, err := os.OpenFile("en_"+fileName, os.O_RDWR|os.O_CREATE, 0666)
    if err != nil {
        fmt.Println("文件寫入錯誤")
        return err
    }
    defer ff.Close()
    //循環(huán)加密，并寫入文件
    for i := 0; i < int(forNum+1); i++ {
        a := make([]byte, getLen)
        n, err := f.Read(a)
        if err != nil {
            fmt.Println("文件讀取錯誤")
            return err
        }
        getByte, err := EncryptByAes(a[:n])
        if err != nil {
            fmt.Println("加密錯誤")
            return err
        }
        getBytes := append([]byte(getByte), []byte("\n")...)
        //寫入
        buf := bufio.NewWriter(ff)
        buf.WriteString(string(getBytes[:]))
        buf.Flush()
    }
    ffInfo, _ := ff.Stat()
    fmt.Printf("加密后文件為：%s，文件大小為：%v Byte \n", ffInfo.Name(), ffInfo.Size())
    return nil
}

func(cmd *cobra.Command, args []string) {
    copy(PwdKey, readPass())
    Pwd := []byte("csgo!gogo")
    if ByteSliceEqual(PwdKey, Pwd) {
        //16字節(jié)key
        PwdKey = append(PwdKey, 7, 3, 5, 5, 6, 0, 8)
        if err := DecryptFile(args[0]); err != nil {
            panic(err)
        }
    } else {
        fmt.Println("密碼錯誤")
        os.Exit(1)
    }
}

# ./scode  encode xpower.tar.gz
待處理文件大小: 3397
加密后文件為：en_xpower.tar.gz，文件大小為：4545 Byte

# ./scode  decode en_xpower.tar.gz
ENTER PASSWORD: 
密碼錯誤

# ./scode  decode en_xpower.tar.gz
ENTER PASSWORD: 
待處理文件大小: 4545
解密后文件為：de_en_xpower.tar.gz，文件大小為：3159 Byte