package aes

import (
    "bytes"
    "crypto/aes"
    "crypto/cipher"
    "encoding/base64"
)

// 加密  aes-128-cbc
func Encrypt(key string, iv string, str string) (string, error) {
    encodeKey := []byte(key)
    encodeIv := []byte(iv)
    encodeStr := []byte(str)

    //获取block块
    block, err := aes.NewCipher(encodeKey)
    if err != nil {
        return "", err
    }
    //补码
    encodeStr = PKCS7Padding(encodeStr, block.BlockSize())
    //加密模式
    blockMode := cipher.NewCBCEncrypter(block, encodeIv)
    //创建明文长度的数组
    dCrypts := make([]byte, len(encodeStr))
    //加密明文
    blockMode.CryptBlocks(dCrypts, encodeStr)
    return base64.StdEncoding.EncodeToString(dCrypts), nil
}

//补码
func PKCS7Padding(origData []byte, blockSize int) []byte {
    //计算需要补几位数
    padding := blockSize - len(origData)%blockSize
    //在切片后面追加char数量的byte(char)
    padtext := bytes.Repeat([]byte{byte(padding)}, padding)
    return append(origData, padtext...)
}

func Decrypt(key string, iv string, str string) (string, error) {
    decodeKey := []byte(key)
    decodeIv := []byte(iv)
    strByte, err := base64.StdEncoding.DecodeString(str)
    if err != nil {
        return "", err
    }
    //获取block块
    block, err := aes.NewCipher(decodeKey)
    if err != nil {
        return "", err
    }
    //解密模式
    blockMode := cipher.NewCBCDecrypter(block, decodeIv)
    //创建明文长度的数组
    decrypted := make([]byte, len(strByte))
    //加密明文
    blockMode.CryptBlocks(decrypted, strByte)
    //去掉字符
    decrypted = PKCS7upPadding(decrypted)
    return string(decrypted), nil
}

// 去掉字符
func PKCS7upPadding(origData []byte) []byte {
    length := len(origData)
    unPadding := int(origData[length-1])
    return origData[:(length - unPadding)]
}