npm install svg-captcha express-session

const svgCaptcha = require("svg-captcha");
const session = require("express-session");

// 配置会话中间件
app.use(
  session({
    secret: "your-secret-key",
    resave: false,
    saveUninitialized: true,
  })
);

// 生成验证码
app.get("/captcha", (req, res) => {
  const captcha = svgCaptcha.create();
  req.session = req.session || {};
  req.session.captcha = captcha.text;
  res.type("svg");
  res.status(200).send(captcha.data);
});

// 用户登录
app.post("/login", async (req, res) => {
  const { username, password, captcha } = req.body;
  if (req.session.captcha !== captcha) {
    return res.status(400).json({ error: "验证码错误" });
  }
  try {
    const user = await User.findOne({ username, password });
    if (user) {
      res.status(200).json({ message: "登录成功" });
    } else {
      res.status(401).json({ error: "用户名或密码错误" });
    }
  } catch (error) {
    res.status(500).json({ error: "登录失败", details: error.message });
  }
});