注意两个base64编码不一样；

policy 用Base64.encode编码

signature 用CryotoJS.enc.Base64.stringify编码

困扰了我两天，终于解决！(如果不是这个问题，看是不是权限问题，多看官方文档)

import CryotoJS from "crypto-js";
import Base64 from "base-64";
import oss from "ali-oss";

async function getSTS() {
  let { data } = await axios.get("/getSTS")
  state.ossClient = new oss({
    accessKeyId: data.AccessKeyId,
    accessKeySecret: data.AccessKeySecret,
    stsToken: data.SecurityToken,
    refreshSTSToken: async () => {
      const data = axios.get("/getSTS")
      return {
        accessKeyId: data.AccessKeyId,
        accessKeySecret: data.AccessKeySecret,
        stsToken: data.SecurityToken,
      }
    },
    refreshSTSTokenInterval: 300000,
    bucket: "wallpaper2023",
    endpoint: "oss-cn-chengdu.aliyuncs.com"
  })
  let policy = {
    "expiration": data.Expiration, //设置该Policy的失效时间，超过这个失效时间之后，就没有办法通过这个policy上传文件了
    "conditions": [
      ["content-length-range", 0, 1048576000] // 设置上传文件的大小限制
    ]
  }
  let policyBase64 = Base64.encode(JSON.stringify(policy))
  state.uploadData.policy = policyBase64
  state.uploadData.OSSAccessKeyId = data.AccessKeyId
  state.uploadData.signature = CryotoJS.enc.Base64.stringify(CryotoJS.HmacSHA1(policyBase64, data.AccessKeySecret))
  state.uploadData['x-oss-security-token'] = data.SecurityToken
}