云函数调用同城配送接口返回签名错误，我是严格按照文档上加密签名的，为什么一直报签名错误

// cloudfunctions/cityDelivery/utils/signature.js

const crypto = require('crypto')

class WechatAPISignature {

  constructor(privateKey, keySn, appid) {

    // 清理私钥格式

    this.privateKey = privateKey.replace(/^  /gm, '').trim()

    this.keySn = keySn

    this.appid = appid

  }

  generateSignature(urlPath, timestamp, postData) {

    try {

      console.log('=== 签名生成详细过程 ===')

      // 严格按照官方格式拼接：url_path\nappid\ntimestamp\npostdata

      const signString = `${urlPath}\n${this.appid}\n${timestamp}\n${postData}`

      console.log('签名组件:')

      console.log('1. URL Path:', urlPath)

      console.log('2. AppID:', this.appid)  

      console.log('3. Timestamp:', timestamp)

      console.log('4. PostData长度:', postData.length)

      console.log('完整签名字符串前200字符:', signString.substring(0, 200))

      const data_buffer = Buffer.from(signString, 'utf-8')

      // 使用正确的签名参数

      const signature = crypto.sign(

        'RSA-SHA256',

        data_buffer, 

        {

          key: this.privateKey,

          padding: crypto.constants.RSA_PKCS1_PSS_PADDING,

          saltLength: 32 // 明确指定salt长度，与文档一致

        }

      )

      const signatureBase64 = signature.toString('base64')

      console.log('签名生成成功，长度:', signatureBase64.length)

      return signatureBase64

    } catch (error) {

      console.error('签名生成失败:', error)

      throw error

    }

  }

}

module.exports = WechatAPISignature