var crypto = require('crypto')
function WXBizDataCrypt(appId, sessionKey) {
this.appId = appId
this.sessionKey = sessionKey
}
WXBizDataCrypt.prototype.decryptData = function (encryptedData, iv) {
// base64 decode
var sessionKey = new Buffer(this.sessionKey, 'base64')
encryptedData = new Buffer(encryptedData, 'base64')
iv = new Buffer(iv, 'base64')
try {
// 解密
var decipher = crypto.createDecipheriv('aes-128-cbc', sessionKey, iv)
// 设置自动 padding 为 true，删除填充补位
decipher.setAutoPadding(true)
var decoded = decipher.update(encryptedData, 'binary', 'utf8')
decoded += decipher.final('utf8')
decoded = JSON.parse(decoded)
} catch (err) {
throw new Error('Illegal Buffer')
}
if (decoded.watermark.appid !== this.appId) {
throw new Error('Illegal Buffer')
}
return decoded
}
module.exports = WXBizDataCrypt
