密钥与 Token 轮换

// 服务端签发用户 Token（Open API 签名，AppSecret 只在服务端）
import { createHash, randomBytes } from 'node:crypto';

const nonce = randomBytes(8).toString("hex");
const timestamp = String(Date.now());
const signature = createHash("sha1").update(APP_SECRET + nonce + timestamp).digest("hex");

const res = await fetch(`${SERVER_URL}/im/v2/user/token/issue`, {
  method: "POST",
  headers: {
    "content-type": "application/json",
    "App-Key": APP_KEY,
    Nonce: nonce,
    Timestamp: timestamp,
    Signature: signature,
  },
  body: JSON.stringify({ userId: "alice" }),
});
const body = await res.json();
// body.data: { token, userId, expireAt }；把 token 返回给客户端（不要返回 AppSecret）

// 接收端验签（Node）：必须用原始 body 字节，不能 JSON.parse 后再序列化。
import { createHmac, timingSafeEqual } from "node:crypto";

export function verify(rawBody, headers, currentSecret, previousSecret) {
  const ts = Number(headers["x-im-timestamp"]);
  if (!Number.isFinite(ts) || Math.abs(Date.now() - ts) > 300000) return false;
  const nonce = headers["x-im-nonce"] || "";
  const got = String(headers["x-im-signature"] || "").toLowerCase();
  for (const secret of [currentSecret, previousSecret].filter(Boolean)) {
    const want = createHmac("sha256", secret).update(`${ts}.${nonce}.${rawBody}`).digest("hex");
    if (want.length === got.length && timingSafeEqual(Buffer.from(want), Buffer.from(got))) return true;
  }
  return false;
}