DSP-ADX 价格解密逻辑 Typescript 版

dsp-adx-price-decrypt.ts

import * as crypto from 'crypto'

const HMAC_ALGORITHM = 'HmacSHA1'
const ekey = Buffer.from('9527')
const ikey = Buffer.from('2840')

const mergeBytes = (...args: Uint8Array[]) => {
  return Buffer.concat(args)
}

const bytesToLong = (b: Buffer) => b.readBigInt64BE()
const longToBytes = (n: bigint) => {
  const b = Buffer.alloc(8)
  b.writeBigInt64BE(n)
  return b
}

const decrypt = (encyptStr: string) => {
  const decode = Buffer.from(encyptStr, 'base64')
  const ekeyMac = crypto.createHmac('sha1', ekey)
  const ikeyMac = crypto.createHmac('sha1', ikey)

  const length = decode.length
  const impressionIdBytes = decode.subarray(0, 16)
  const priceBytes = decode.subarray(16, length - 4)
  const requestSign = decode.subarray(length - 4, length)

  const requestIdMac = ekeyMac.update(impressionIdBytes).digest()
  const requestIdMacPart = requestIdMac.subarray(0, 8)

  const temp = requestIdMacPart.readBigInt64BE()
  const price = priceBytes.readBigInt64BE() ^ temp

  const data = ikeyMac
    .update(mergeBytes(longToBytes(price), impressionIdBytes))
    .digest()
  const sign = data.subarray(0, 4)

  for (let i = 0; i < 4; ++i) {
    if (sign[i] !== requestSign[i]) {
      throw new Error('参数有误，验签失败')
    }
  }

  return price
}

// decrypt('MTIzNDU2Nzg5MTIzNDU2N-9-9pSOh7qyG_4KZg==') // 1010
export default decrypt