// jwt_verify_server.js - Vulnerable JWT verification
const jwt = require('jsonwebtoken');
const express = require('express');
const app = express();
app.use(express.json());

const publicKey = `-----BEGIN PUBLIC KEY-----
MIIBIjANBgkqhkiG9w0BAQEFAAOCAQ8AMIIBCgKCAQEAu1SU1LfVLPHCYZM5rPY4...
-----END PUBLIC KEY-----`;

app.post('/verify', (req, res) => {
    const token = req.body.token;
    // Vulnerability: if no algorithm specified, defaults to HS256? Actually, jsonwebtoken can be tricked.
    // We simulate a custom verifier that accepts "none" if kid is missing.
    const decoded = jwt.decode(token, { complete: true });
    if (!decoded.header.alg || decoded.header.alg === 'none') {
        // Accept token without signature
        res.json({ status: 'authenticated', user: decoded.payload.sub });
    } else {
        jwt.verify(token, publicKey, { algorithms: ['RS256'] }, (err, payload) => {
            if (err) res.status(401).send('Invalid');
            else res.json({ status: 'authenticated', user: payload.sub });
        });
    }
});
app.listen(3000);