Code Breaking Writeup

// initial libraries
const Koa = require('koa')
const sqlite = require('sqlite')
const fs = require('fs')
const views = require('koa-views')
const Router = require('koa-router')
const send = require('koa-send')
const bodyParser = require('koa-bodyparser')
const session = require('koa-session')
const isString = require('underscore').isString
const basename = require('path').basename

const config = JSON.parse(fs.readFileSync('../config.json', {encoding: 'utf-8', flag: 'r'}))

async function main() {
    const app = new Koa()
    const router = new Router()
    const db = await sqlite.open(':memory:')

    await db.exec(`CREATE TABLE "main"."users" (
        "id" INTEGER NOT NULL PRIMARY KEY AUTOINCREMENT,
        "username" TEXT NOT NULL,
        "password" TEXT,
        CONSTRAINT "unique_username" UNIQUE ("username")
    )`)
    await db.exec(`CREATE TABLE "main"."flags" (
        "id" INTEGER NOT NULL PRIMARY KEY AUTOINCREMENT,
        "flag" TEXT NOT NULL
    )`)
    for (let user of config.users) {
        await db.run(`INSERT INTO "users"("username", "password") VALUES ('${user.username}', '${user.password}')`)
    }
    await db.run(`INSERT INTO "flags"("flag") VALUES ('${config.flag}')`)

    router.all('login', '/login/', login).get('admin', '/', admin).get('static', '/static/:path(.+)', static).get('/source', source)

    app.use(views(__dirname + '/views', {
        map: {
            html: 'underscore'
        },
        extension: 'html'
    })).use(bodyParser()).use(session(app))

    app.use(router.routes()).use(router.allowedMethods());

    app.keys = config.signed
    app.context.db = db
    app.context.router = router
    app.listen(3000)
}

function safeKeyword(keyword) {
    if(isString(keyword) && !keyword.match(/(union|select|;|\-\-)/is)) {
        return keyword
    }

    return undefined
}

async function login(ctx, next) {
    if(ctx.method == 'POST') {
        let username = safeKeyword(ctx.request.body['username'])
        let password = safeKeyword(ctx.request.body['password'])

        let jump = ctx.router.url('login')
        if (username && password) {
            let user = await ctx.db.get(`SELECT * FROM "users" WHERE "username" = '${username.toUpperCase()}' AND "password" = '${password.toUpperCase()}'`)

            if (user) {
                ctx.session.user = user

                jump = ctx.router.url('admin')
            }

        }

        ctx.status = 303
        ctx.redirect(jump)
    } else {
        await ctx.render('index')
    }
}

async function static(ctx, next) {
    await send(ctx, ctx.path)
}

async function admin(ctx, next) {
    if(!ctx.session.user) {
        ctx.status = 303
        return ctx.redirect(ctx.router.url('login'))
    }

    await ctx.render('admin', {
        'user': ctx.session.user
    })
}

async function source(ctx, next) {
    await send(ctx, basename(__filename))
}

main()

const fs = require('fs')
const express = require('express')
const bodyParser = require('body-parser')
const lodash = require('lodash')
const session = require('express-session')
const randomize = require('randomatic')

const app = express()
app.use(bodyParser.urlencoded({extended: true})).use(bodyParser.json()) //对post请求的请求体进行解析
app.use('/static', express.static('static'))
app.use(session({
    name: 'thejs.session',
    secret: randomize('aA0', 16), // 随机数
    resave: false,
    saveUninitialized: false
}))
app.engine('ejs', function (filePath, options, callback) { // 模板引擎
    fs.readFile(filePath, (err, content) => {   //读文件 filepath
        if (err) return callback(new Error(err))
        let compiled = lodash.template(content)  //模板化
        let rendered = compiled({...options})   //动态引入变量

        return callback(null, rendered)
    })
})
app.set('views', './views')
app.set('view engine', 'ejs')

app.all('/', (req, res) => {
    let data = req.session.data || {language: [], category: []}
    if (req.method == 'POST') {
        data = lodash.merge(data, req.body) // merge 合并字典
        req.session.data = data
    }

    res.render('index', {
        language: data.language, 
        category: data.category
    })
})

app.listen(3000, () => console.log(`Example app listening on port 3000!`))