羊城杯2020 a_piece_of_java

catch me if you can

F12拿到flag

actf{y0u_caught_m3!_0101ff9abc2a724814dfd1c85c766afc7fbd88d2cdf747d8d9ddbf12d68ff874}

Celeste Speedrunning Association

看题目意思好像要时间破个记录，访问/play路由有个按钮，点了后告诉我没有破记录，用hackbar看一眼有个POST参数start,猜测是通过当前时间减去这个start的时间值来算记录时间的，那就把start的值改大一点，让时间是负的就可以拿到flag

actf{wait_until_farewell_speedrun}

shortcircuit

随便传入账号密码不对，hackbar也没显示传参，F12查看源码发现一段js

const swap = (x) => {
    let t = x[0]
    x[0] = x[3]
    x[3] = t

    t = x[2]
    x[2] = x[1]
    x[1] = t

    t = x[1]
    x[1] = x[3]
    x[3] = t

    t = x[3]
    x[3] = x[2]
    x[2] = t

    return x
}

const chunk = (x, n) => {
    let ret = []

    for(let i = 0; i < x.length; i+=n){
        ret.push(x.substring(i,i+n))
    }

    return ret
}

const check = (e) => {
    if (document.forms[0].username.value === "admin") {
        if (swap(chunk(document.forms[0].password.value, 30)).join("") == "7e08250c4aaa9ed206fd7c9e398e2}actf{cl1ent_s1de_sucks_544e67ef12024523398ee02fe7517fffa92516317199e454f4d2bdb04d9e419ccc7") {
            location.href = "/win.html"
        }
    }
}

根据题意是把密码每30个字符分为一组，然后通过swap函数交换四段字符位置，输出结果为7e08250c4aaa9ed206fd7c9e398e2}actf{cl1ent_s1de_sucks_544e67ef12024523398ee02fe7517fffa92516317199e454f4d2bdb04d9e419ccc7,先把四段字符分开看

7e08250c4aaa9ed206fd7c9e398e2}
actf{cl1ent_s1de_sucks_544e67e
f12024523398ee02fe7517fffa9251
6317199e454f4d2bdb04d9e419ccc7

按照swap函数的定义，这段字符原本的顺序是4132，所以正确的密码是

actf{cl1ent_s1de_sucks_544e67e6317199e454f4d2bdb04d9e419ccc7f12024523398ee02fe7517fffa92517e08250c4aaa9ed206fd7c9e398e2}

即flag

directory

纯爆破，在burpsuite中用Intruder模块爆破，在3054.html找到flag

actf{y0u_f0und_me_b51d0cde76739fa3}

Celeste Tunneling Association

查看源码：

# run via `uvicorn app:app --port 6000`
import os

SECRET_SITE = b"flag.local"
FLAG = os.environ['FLAG']

async def app(scope, receive, send):
    assert scope['type'] == 'http'

    headers = scope['headers']

    await send({
        'type': 'http.response.start',
        'status': 200,
        'headers': [
            [b'content-type', b'text/plain'],
        ],
    })

    # IDK malformed requests or something
    num_hosts = 0
    for name, value in headers:
        if name == b"host":
            num_hosts += 1

    if num_hosts == 1:
        for name, value in headers:
            if name == b"host" and value == SECRET_SITE:
                await send({
                    'type': 'http.response.body',
                    'body': FLAG.encode(),
                })
                return

    await send({
        'type': 'http.response.body',
        'body': b'Welcome to the _tunnel_. Watch your step!!',
    })

可知，要求请求中host值为flag.local获得flag，hackbar发包不成功，用python写个脚本发包获取flag：

import requests

headers = {
    "Host": "flag.local"
}

response = requests.get("https://pioneer.tailec718.ts.net/", headers=headers)
print(response.text)

actf{reaching_the_core__chapter_8}

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