nodejs大文件分片加密解密

　　承接之前博客：nodejs向加密文件指定位置插入内容

　　我们需要对大文件进行处理，并需要真实的进度，那么就需要分片加密和解密。

1、前端分片

// 分片上传
async burst (ks, cryType, id) {
  let _home = this.$refs.home
  let successNum = 0
  let index = 0
  let start = 0
  let end = 0
  this.burstOneByOne(_home, successNum, index, start, end, ks, cryType, id)
},
async burstOneByOne (_home, successNum, index, start, end, ks, cryType, id) {
  let _size = _home.curSize
  let bytesPerPiece = 1024 * 1024 * 3 // 3M一个分片
  let totalPieces = Math.ceil(_size / bytesPerPiece) // 切片总数
  if (start < _size) {
    end = start + bytesPerPiece
    if (end >= _size) end = _size // 匹配最后一个分片的情况
    let _params = {
      start: start,
      end: end,
      index: index,
      filepath: _home.curPath,
      filename: _home.curFile,
      ks: ks,
      cryType: cryType
    }
    if (id) {
      _params.fileId = id
    }
    let res = await burstFileApi(_params)
    if (res.status) {
      successNum++
      this.percentage = (100 * successNum / totalPieces).toFixed(2) - 0
      start = end
      index++
      if (index < totalPieces) {
        this.burstOneByOne(_home, successNum, index, start, end, ks, cryType, id)
      } else {
        if (id) {
          this.submitFileKdRelation(id) // 加密完成上报密钥与文件关系
        }              
        this.$refs.home.fetchData()
        return
      }
    }
  }
},

　　我们分片并使用递归，一个成功才接着下一个，主要是思路，ks、fileId等很多是特殊的加密解密前处理，获取加解密相关参数的东西，可以不理会

2、后端合并

　　主要使用fs.appendFile的方法

　　加解密的东西

var AES_conf = {
  key: '54F0853FD5D8D2FD61CE33309B0D0273', // 密钥
  iv: 'A19820BCE43576DF', // 偏移向量
  padding: 'PKCS7Padding', // 补全值
  code: 'JeOW0ix7'
}
function aesEncryptNew (buff, key, iv) {
  let cipher = crypto.createCipheriv('aes-256-cbc', key, iv)
  let crypted = cipher.update(buff, '', 'hex')
  crypted += cipher.final('hex')
  return crypted
}
function aesDecryptNew (buff, key, iv) {
  let decipher = crypto.createDecipheriv('aes-256-cbc', key, iv)
  return decipher.update(buff, 'hex', '')
}

　　文件合并的东西

function burstFile (query) {
  return new Promise((resolve, reject) => {
    let { start, end, filepath, filename, index, ks, cryType, fileId } = query
    let _path = path.join(filepath, filename)
    let buff = fs.readFileSync(_path)
    if (cryType === 'decry') { // 如果解密的话需要剔除掉前面的40个头信息
      buff = buff.slice(40)
    }
    let bufferFile = buff.slice(start, end)
    encryptBurstFile(bufferFile, _path, ks, cryType, index, fileId).then(_ => {
      resolve()
    }).catch(err => {
      console.log('err', err)
      reject(err)
    })
  })
}
function encryptBurstFile (buff, _path, ks, cryType, index, fileId) {
  return new Promise(function (resolve, reject) {
    let key = AES_conf.key
    if (ks) {
      key = ks
    }
    let iv = AES_conf.iv
    let buffEnc = cryType === 'encry' ? aesEncryptNew(buff, key, iv) : aesDecryptNew(buff, key, iv)
    let _newPath = ''
    if (cryType === 'encry') {
      _newPath = _path + '.mc.bin'
      if (index === '0') { // 如果是加密的第一个分片，需要加上头信息code
        let code = AES_conf.code + fileId
        fs.appendFileSync(_newPath, code, 'utf8')
      }
      fs.appendFileSync(_newPath, Buffer.from(buffEnc, 'hex'))
    } else {
      _newPath = _path.replace(/.mc.bin/g, '')
      fs.appendFileSync(_newPath, buffEnc)
    }
    resolve(_newPath)
  })
}