BUUCTF 加固題 Ezsql WriteUp-有解無憂

文章目錄

- 想直接要加固代碼的點這里
- - 題目
  - 一、查看
  - 二、進入目標機器加固
  - - 修改前的檔案：
    - 添加如下代碼：
    - 修改后的檔案
  - 三、Check

想直接要加固代碼的點這里

題目

靶機地址解釋：

第一行：目標機器 WEB 服務地址

第二行：目標機器 SSH 地址以及埠

第三行：Check 服務訪問地址

修復方法：

SSH 連接上目標機器，用戶 ctf，密碼 123456，
對目標機器上的服務進行加固，
訪問 Check 服務的 /check進行 check，
若回傳 True，則訪問 /flag 可獲得 /flag，
每次 check 后目標機器會重置，

一、查看

訪問目標機器web服務地址，發現是一個登陸界面

利用萬能密碼登錄成功

用戶名：admin' or 1=1#

密碼： 任意

登陸成功，本題就是讓加固這個登陸界面，以防止sql注入即可獲取flag，

二、進入目標機器加固

根據給的地址和埠ssh連接目標機器，進入/var/www/html目錄

加固index.php，查看它的原始碼

修改前的檔案：

<!DOCTYPE html>
<html lang="zh">
<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge,chrome=1">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>讓我訪問</title>
    <link href="http://cdn.bootcss.com/bootstrap/3.3.7/css/bootstrap.min.css" rel="stylesheet">
    <link href="http://cdn.bootcss.com/font-awesome/4.6.3/css/font-awesome.min.css" rel="stylesheet">
    <link rel="stylesheet" type="text/css" href="css/htmleaf-demo.css">
    <style type="text/css">
        .form-bg {
            padding: 2em 0;
        }

        .form-horizontal {
            background: #ffffff;
            padding-bottom: 40px;
            border-radius: 15px;
            text-align: center;
        }

        .form-horizontal .heading {
            display: block;
            font-size: 35px;
            font-weight: 700;
            padding: 35px 0;
            border-bottom: 1px solid #f0f0f0;
            margin-bottom: 30px;
        }

        .form-horizontal .form-group {
            padding: 0 40px;
            margin: 0 0 25px 0;
            position: relative;
        }

        .form-horizontal .form-control {
            background: #f0f0f0;
            border: none;
            border-radius: 20px;
            box-shadow: none;
            padding: 0 20px 0 45px;
            height: 40px;
            transition: all 0.3s ease 0s;
        }

        .form-horizontal .form-control:focus {
            background: #e0e0e0;
            box-shadow: none;
            outline: 0 none;
        }

        .form-horizontal .form-group i {
            position: absolute;
            top: 12px;
            left: 60px;
            font-size: 17px;
            color: #c8c8c8;
            transition: all 0.5s ease 0s;
        }

        .form-horizontal .form-control:focus + i {
            color: #00b4ef;
        }

        .form-horizontal .fa-question-circle {
            display: inline-block;
            position: absolute;
            top: 12px;
            right: 60px;
            font-size: 20px;
            color: #808080;
            transition: all 0.5s ease 0s;
        }

        .form-horizontal .fa-question-circle:hover {
            color: #000;
        }

        .form-horizontal .main-checkbox {
            float: left;
            width: 20px;
            height: 20px;
            background: #11a3fc;
            border-radius: 50%;
            position: relative;
            margin: 5px 0 0 5px;
            border: 1px solid #11a3fc;
        }

        .form-horizontal .main-checkbox label {
            width: 20px;
            height: 20px;
            position: absolute;
            top: 0;
            left: 0;
            cursor: pointer;
        }

        .form-horizontal .main-checkbox label:after {
            content: "";
            width: 10px;
            height: 5px;
            position: absolute;
            top: 5px;
            left: 4px;
            border: 3px solid #fff;
            border-top: none;
            border-right: none;
            background: transparent;
            opacity: 0;
            -webkit-transform: rotate(-45deg);
            transform: rotate(-45deg);
        }

        .form-horizontal .main-checkbox input[type=checkbox] {
            visibility: hidden;
        }

        .form-horizontal .main-checkbox input[type=checkbox]:checked + label:after {
            opacity: 1;
        }

        .form-horizontal .text {
            float: left;
            margin-left: 7px;
            line-height: 20px;
            padding-top: 5px;
            text-transform: capitalize;
        }

        .form-horizontal .btn {
            float: right;
            font-size: 14px;
            color: #fff;
            background: #00b4ef;
            border-radius: 30px;
            padding: 10px 25px;
            border: none;
            text-transform: capitalize;
            transition: all 0.5s ease 0s;
        }

        @media only screen and (max-width: 479px) {
            .form-horizontal .form-group {
                padding: 0 25px;
            }

            .form-horizontal .form-group i {
                left: 45px;
            }

            .form-horizontal .btn {
                padding: 10px 20px;
            }
        }
    </style>
</head>
<body>
<div class="htmleaf-container">
    <header class="htmleaf-header">
        <h1>我還可以教你，敦 dua 郎哦，</h1>
        <div class="htmleaf-links">
        </div>
    </header>
    <div class="demo form-bg">
        <div class="container">
            <div class="row">
                <div class="col-md-offset-3 col-md-6">
                    <form class="form-horizontal" method="get" action="">
                        <span class="heading">讓我訪問</span>
                        <div class="form-group">
                            <input type="text" class="form-control" id="inputEmail3" placeholder="用戶名" name="username">
                        </div>
                        <div class="form-group help">
                            <input type="password" class="form-control" id="inputPassword3" placeholder="密碼"
                                   name="password">
                        </div>
                        <div class="form-group help">
                            <input type="submit" class="form-control" id="inputSubmit">
                        </div>
                    </form>
                </div>
            </div>
        </div>
    </div>
    <div class="related">
    </div>
</div>
</body>
</html>
<h4 style="text-align: center; color: #000000">
<?php
error_reporting(0);
include 'dbConnect.php';
$username = $_GET['username'];
$password = $_GET['password'];
if (isset($_GET['username']) && isset($_GET['password'])) {
    $sql = "SELECT * FROM users WHERE username = '$username' AND password = '$password'";
    $result = $mysqli->query($sql);
    if (!$result)
        die(mysqli_error($mysqli));
    $data = $result->fetch_all(); // 從結果集中獲取所有資料
    if (!empty($data)) {
        echo '登錄成功！';
    } else {
        echo "用戶名或密碼錯誤";
    }
}
?>
</h4>

添加如下代碼：

$username = addslashes($username);
$password = addslashes($password);

以下是W3school對 addslashes() 函式的解釋

addslashes() 函式回傳在預定義字符之前添加反斜杠的字串，
預定義字符是：

單引號（’）
雙引號（"）
反斜杠（\）
NULL

該函式可用于為存盤在資料庫中的字串以及資料庫查詢陳述句準備字串，

修改后的檔案

<!DOCTYPE html>
<html lang="zh">
<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge,chrome=1">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>讓我訪問</title>
    <link href="http://cdn.bootcss.com/bootstrap/3.3.7/css/bootstrap.min.css" rel="stylesheet">
    <link href="http://cdn.bootcss.com/font-awesome/4.6.3/css/font-awesome.min.css" rel="stylesheet">
    <link rel="stylesheet" type="text/css" href="css/htmleaf-demo.css">
    <style type="text/css">
        .form-bg {
            padding: 2em 0;
        }

        .form-horizontal {
            background: #ffffff;
            padding-bottom: 40px;
            border-radius: 15px;
            text-align: center;
        }

        .form-horizontal .heading {
            display: block;
            font-size: 35px;
            font-weight: 700;
            padding: 35px 0;
            border-bottom: 1px solid #f0f0f0;
            margin-bottom: 30px;
        }

        .form-horizontal .form-group {
            padding: 0 40px;
            margin: 0 0 25px 0;
            position: relative;
        }

        .form-horizontal .form-control {
            background: #f0f0f0;
            border: none;
            border-radius: 20px;
            box-shadow: none;
            padding: 0 20px 0 45px;
            height: 40px;
            transition: all 0.3s ease 0s;
        }

        .form-horizontal .form-control:focus {
            background: #e0e0e0;
            box-shadow: none;
            outline: 0 none;
        }

        .form-horizontal .form-group i {
            position: absolute;
            top: 12px;
            left: 60px;
            font-size: 17px;
            color: #c8c8c8;
            transition: all 0.5s ease 0s;
        }

        .form-horizontal .form-control:focus + i {
            color: #00b4ef;
        }

        .form-horizontal .fa-question-circle {
            display: inline-block;
            position: absolute;
            top: 12px;
            right: 60px;
            font-size: 20px;
            color: #808080;
            transition: all 0.5s ease 0s;
        }

        .form-horizontal .fa-question-circle:hover {
            color: #000;
        }

        .form-horizontal .main-checkbox {
            float: left;
            width: 20px;
            height: 20px;
            background: #11a3fc;
            border-radius: 50%;
            position: relative;
            margin: 5px 0 0 5px;
            border: 1px solid #11a3fc;
        }

        .form-horizontal .main-checkbox label {
            width: 20px;
            height: 20px;
            position: absolute;
            top: 0;
            left: 0;
            cursor: pointer;
        }

        .form-horizontal .main-checkbox label:after {
            content: "";
            width: 10px;
            height: 5px;
            position: absolute;
            top: 5px;
            left: 4px;
            border: 3px solid #fff;
            border-top: none;
            border-right: none;
            background: transparent;
            opacity: 0;
            -webkit-transform: rotate(-45deg);
            transform: rotate(-45deg);
        }

        .form-horizontal .main-checkbox input[type=checkbox] {
            visibility: hidden;
        }

        .form-horizontal .main-checkbox input[type=checkbox]:checked + label:after {
            opacity: 1;
        }

        .form-horizontal .text {
            float: left;
            margin-left: 7px;
            line-height: 20px;
            padding-top: 5px;
            text-transform: capitalize;
        }

        .form-horizontal .btn {
            float: right;
            font-size: 14px;
            color: #fff;
            background: #00b4ef;
            border-radius: 30px;
            padding: 10px 25px;
            border: none;
            text-transform: capitalize;
            transition: all 0.5s ease 0s;
        }

        @media only screen and (max-width: 479px) {
            .form-horizontal .form-group {
                padding: 0 25px;
            }

            .form-horizontal .form-group i {
                left: 45px;
            }

            .form-horizontal .btn {
                padding: 10px 20px;
            }
        }
    </style>
</head>
<body>
<div class="htmleaf-container">
    <header class="htmleaf-header">
        <h1>我還可以教你，敦 dua 郎哦，</h1>
        <div class="htmleaf-links">
        </div>
    </header>
    <div class="demo form-bg">
        <div class="container">
            <div class="row">
                <div class="col-md-offset-3 col-md-6">
                    <form class="form-horizontal" method="get" action="">
                        <span class="heading">讓我訪問</span>
                        <div class="form-group">
                            <input type="text" class="form-control" id="inputEmail3" placeholder="用戶名" name="username">
                        </div>
                        <div class="form-group help">
                            <input type="password" class="form-control" id="inputPassword3" placeholder="密碼"
                                   name="password">
                        </div>
                        <div class="form-group help">
                            <input type="submit" class="form-control" id="inputSubmit">
                        </div>
                    </form>
                </div>
            </div>
        </div>
    </div>
    <div class="related">
    </div>
</div>
</body>
</html>
<h4 style="text-align: center; color: #000000">
<?php
error_reporting(0);
include 'dbConnect.php';
$username = $_GET['username'];
$password = $_GET['password'];

$username = addslashes($username);
$password = addslashes($password);


if (isset($_GET['username']) && isset($_GET['password'])) {
        $sql = "SELECT * FROM users WHERE username = '$username' AND password = '$password'";
        $result = $mysqli->query($sql);
        if (!$result)
            die(mysqli_error($mysqli));
        $data = $result->fetch_all(); // 從結果集中獲取所有資料
        if (!empty($data)) {
            echo '登錄成功！';
        } 
    else { echo "用戶名或密碼錯誤"; }
}
?>
</h4>

三、Check

再次進行萬能密碼登錄發現已經不行了，然后就訪問Check服務進行check

在這里插入圖片描述

然后訪問flag，發現flag已經出來了

在這里插入圖片描述

轉載請註明出處，本文鏈接：https://www.uj5u.com/qita/413272.html

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