prize_p2

原创于 2025-04-01 09:04:18 发布 · 226 阅读

0 ·

CC 4.0 BY-SA版权

文章标签：

#网络安全 #NSSCTF

题目

const { randomBytes } = require('crypto');
const express = require('express');
const fs = require('fs');
const fp = '/app/src/flag.txt';
const app = express();
const flag = Buffer(255);
const a = fs.open(fp, 'r', (err, fd) => {
    fs.read(fd, flag, 0, 44, 0, () => {
        fs.rm(fp, () => {});
    });
});

app.get('/', function (req, res) {
    res.set('Content-Type', 'text/javascript;charset=utf-8');
    res.send(fs.readFileSync(__filename));
});

app.get('/hint', function (req, res) {
    res.send(flag.toString().slice(0, randomBytes(1)[0]%32));
})

// 随机数预测或者一天之后
app.get('/getflag', function (req, res) {
    res.set('Content-Type', 'text/javascript;charset=utf-8');
    try {
        let a = req.query.a;
        if (a === randomBytes(3).toString()) {
            res.send(fs.readFileSync(req.query.b));
        } else {
            const t = setTimeout(() => {
                res.send(fs.readFileSync(req.query.b));
            }, parseInt(req.query.c)?Math.max(86400*1000, parseInt(req.query.c)):86400*1000);
        }
    } catch {
        res.send('?');
    }
})

app.listen(80, '0.0.0.0', () => {
    console.log('Start listening')
});