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