UPLAOD-LABS2-编程知识

less7

任务

拿到一个shell服务器

提示

禁止上传所有可以解析的后缀

发现所有可以解析的后缀都被禁了

查看一下源代码

$is_upload = false;
$msg = null;
if (isset($_POST['submit'])) {if (file_exists($UPLOAD_ADDR)) {$deny_ext = array(".php",".php5",".php4",".php3",".php2",".html",".htm",".phtml",".pHp",".pHp5",".pHp4",".pHp3",".pHp2",".Html",".Htm",".pHtml",".jsp",".jspa",".jspx",".jsw",".jsv",".jspf",".jtml",".jSp",".jSpx",".jSpa",".jSw",".jSv",".jSpf",".jHtml",".asp",".aspx",".asa",".asax",".ascx",".ashx",".asmx",".cer",".aSp",".aSpx",".aSa",".aSax",".aScx",".aShx",".aSmx",".cEr",".sWf",".swf",".htaccess");$file_name = trim($_FILES['upload_file']['name']);$file_ext = strrchr($file_name, '.');$file_ext = strtolower($file_ext); //转换为小写$file_ext = str_ireplace('::$DATA', '', $file_ext);//去除字符串::$DATA$file_ext = trim($file_ext); //首尾去空if (!in_array($file_ext, $deny_ext)) {if (move_uploaded_file($_FILES['upload_file']['tmp_name'], $UPLOAD_ADDR . '/' . $_FILES['upload_file']['name'])) {$img_path = $UPLOAD_ADDR . '/' . $file_name;$is_upload = true;}} else {$msg = '此文件不允许上传';}} else {$msg = $UPLOAD_ADDR . '文件夹不存在,请手工创建！';}
}

第六关的源代码

$is_upload = false;
$msg = null;
if (isset($_POST['submit'])) {if (file_exists($UPLOAD_ADDR)) {$deny_ext = array(".php",".php5",".php4",".php3",".php2",".html",".htm",".phtml",".pHp",".pHp5",".pHp4",".pHp3",".pHp2",".Html",".Htm",".pHtml",".jsp",".jspa",".jspx",".jsw",".jsv",".jspf",".jtml",".jSp",".jSpx",".jSpa",".jSw",".jSv",".jSpf",".jHtml",".asp",".aspx",".asa",".asax",".ascx",".ashx",".asmx",".cer",".aSp",".aSpx",".aSa",".aSax",".aScx",".aShx",".aSmx",".cEr",".sWf",".swf",".htaccess");$file_name = trim($_FILES['upload_file']['name']);$file_name = deldot($file_name);//删除文件名末尾的点$file_ext = strrchr($file_name, '.');$file_ext = strtolower($file_ext); //转换为小写$file_ext = str_ireplace('::$DATA', '', $file_ext);//去除字符串::$DATAif (!in_array($file_ext, $deny_ext)) {if (move_uploaded_file($_FILES['upload_file']['tmp_name'], $UPLOAD_ADDR . '/' . $_FILES['upload_file']['name'])) {$img_path = $UPLOAD_ADDR . '/' . $file_name;$is_upload = true;}} else {$msg = '此文件不允许上传';}} else {$msg = $UPLOAD_ADDR . '文件夹不存在,请手工创建！';}
}

通过源码我们发现，第七关少了删除文件名末尾的

 $file_name = deldot($file_name) //删除文件末尾的点

第七关没有对末尾的点进行一定的限制，那么就可以用了，在文件的末尾加上一个点看看

上传了3.php，然后在文件末尾加上一个点，文件上传成功

less8

提示

禁止上传.php|.php5|.php4|.php3|.php2|php1|.html|.htm|.phtml|.pHp|.pHp5|.pHp4|.pHp3|.pHp2|pHp1|.Html|.Htm|.pHtml|.jsp|.jspa|.jspx|.jsw|.jsv|.jspf|.jtml|.jSp|.jSpx|.jSpa|.jSw|.jSv|.jSpf|.jHtml|.asp|.aspx|.asa|.asax|.ascx|.ashx|.asmx|.cer|.aSp|.aSpx|.aSa|.aSax|.aScx|.aShx|.aSmx|.cEr|.sWf|.swf|.htaccess后缀文件

源代码

$is_upload = false;
$msg = null;
if (isset($_POST['submit'])) {if (file_exists($UPLOAD_ADDR)) {$deny_ext = array(".php",".php5",".php4",".php3",".php2",".html",".htm",".phtml",".pHp",".pHp5",".pHp4",".pHp3",".pHp2",".Html",".Htm",".pHtml",".jsp",".jspa",".jspx",".jsw",".jsv",".jspf",".jtml",".jSp",".jSpx",".jSpa",".jSw",".jSv",".jSpf",".jHtml",".asp",".aspx",".asa",".asax",".ascx",".ashx",".asmx",".cer",".aSp",".aSpx",".aSa",".aSax",".aScx",".aShx",".aSmx",".cEr",".sWf",".swf",".htaccess");$file_name = trim($_FILES['upload_file']['name']);$file_name = deldot($file_name);//删除文件名末尾的点$file_ext = strrchr($file_name, '.');$file_ext = strtolower($file_ext); //转换为小写$file_ext = trim($file_ext); //首尾去空if (!in_array($file_ext, $deny_ext)) {if (move_uploaded_file($_FILES['upload_file']['tmp_name'], $UPLOAD_ADDR . '/' . $_FILES['upload_file']['name'])) {$img_path = $UPLOAD_ADDR . '/' . $file_name;$is_upload = true;}} else {$msg = '此文件不允许上传';}} else {$msg = $UPLOAD_ADDR . '文件夹不存在,请手工创建！';}
}

也是观察的源代码，发现没有对pHp6进行限制，就先上传一个看看，发现是可以的

这个显然有点勉强，从源代码着手看看

与第七关的代码对比一下，这一关没有字符串的限制

$file_ext = str_ireplace('::$DATA', '', $file_ext);//去除字符串::$DATA

在文件的末尾加上::$DATA看看eg 3.php::$DATA

less9

只允许上传.jpg|.png|.gif后缀的文件

源代码

$is_upload = false;
$msg = null;
if (isset($_POST['submit'])) {if (file_exists($UPLOAD_ADDR)) {$deny_ext = array(".php",".php5",".php4",".php3",".php2",".html",".htm",".phtml",".pHp",".pHp5",".pHp4",".pHp3",".pHp2",".Html",".Htm",".pHtml",".jsp",".jspa",".jspx",".jsw",".jsv",".jspf",".jtml",".jSp",".jSpx",".jSpa",".jSw",".jSv",".jSpf",".jHtml",".asp",".aspx",".asa",".asax",".ascx",".ashx",".asmx",".cer",".aSp",".aSpx",".aSa",".aSax",".aScx",".aShx",".aSmx",".cEr",".sWf",".swf",".htaccess");$file_name = trim($_FILES['upload_file']['name']);$file_name = deldot($file_name);//删除文件名末尾的点$file_ext = strrchr($file_name, '.');$file_ext = strtolower($file_ext); //转换为小写$file_ext = str_ireplace('::$DATA', '', $file_ext);//去除字符串::$DATA$file_ext = trim($file_ext); //首尾去空if (!in_array($file_ext, $deny_ext)) {if (move_uploaded_file($_FILES['upload_file']['tmp_name'], $UPLOAD_ADDR . '/' . $_FILES['upload_file']['name'])) {$img_path = $UPLOAD_ADDR . '/' . $file_name;$is_upload = true;}} else {$msg = '此文件不允许上传';}} else {$msg = $UPLOAD_ADDR . '文件夹不存在,请手工创建！';}
}

发现它先将后缀名后的‘.’删除，然后删除空格

先按照提示的上传jpg，是可以的上传的

从代码出发

只过滤了一次点，那么就用上两个点

“点+空格+点”过滤，抓包之后进行修改

3.php. .

也是可以的

less10

从文件名中去除.php|.php5|.php4|.php3|.php2|php1|.html|.htm|.phtml|.pHp|.pHp5|.pHp4|.pHp3|.pHp2|pHp1|.Html|.Htm|.pHtml|.jsp|.jspa|.jspx|.jsw|.jsv|.jspf|.jtml|.jSp|.jSpx|.jSpa|.jSw|.jSv|.jSpf|.jHtml|.asp|.aspx|.asa|.asax|.ascx|.ashx|.asmx|.cer|.aSp|.aSpx|.aSa|.aSax|.aScx|.aShx|.aSmx|.cEr|.sWf|.swf|.htaccess字符！

源代码

$is_upload = false;
$msg = null;
if (isset($_POST['submit'])) {if (file_exists($UPLOAD_ADDR)) {$deny_ext = array("php","php5","php4","php3","php2","html","htm","phtml","jsp","jspa","jspx","jsw","jsv","jspf","jtml","asp","aspx","asa","asax","ascx","ashx","asmx","cer","swf","htaccess");$file_name = trim($_FILES['upload_file']['name']);$file_name = str_ireplace($deny_ext,"", $file_name);if (move_uploaded_file($_FILES['upload_file']['tmp_name'], $UPLOAD_ADDR . '/' . $file_name)) {$img_path = $UPLOAD_ADDR . '/' .$file_name;$is_upload = true;}} else {$msg = $UPLOAD_ADDR . '文件夹不存在,请手工创建！';}
}

$file_name = str_ireplace($deny_ext,"", $file_name); //这段代码是去除黑名单里面的名称

换句话说就是文件后缀没有了，那么就可以双写绕过，后面也是试了一下pHp6也是可以的

less11

提示

本pass上传路径可控

源代码

$is_upload = false;
$msg = null;
if(isset($_POST['submit'])){$ext_arr = array('jpg','png','gif');$file_ext = substr($_FILES['upload_file']['name'],strrpos($_FILES['upload_file']['name'],".")+1);if(in_array($file_ext,$ext_arr)){$temp_file = $_FILES['upload_file']['tmp_name'];$img_path = $_GET['save_path']."/".rand(10, 99).date("YmdHis").".".$file_ext;if(move_uploaded_file($temp_file,$img_path)){$is_upload = true;}else{$msg = '上传失败！';}}else{$msg = "只允许上传.jpg|.png|.gif类型文件！";}
}

1.$ext_arr = array('jpg','png','gif'); 这里使用了数组做了一个白名单，也就是只能上传这三种类型的文件

2.$file_ext = substr($_FILES['upload_file']['name'],strrpos($_FILES['upload_file']['name'],".")+1);

截取文件名的后缀从点的位置开始截取，并且使用的是循环的方式截取，不是采用一次性

对($_FILES['upload_file']['name']进行验证，也是对上面代码的进一步验证，限制文件的类型

3. if(in_array($file_ext,$ext_arr)){ 判断上传的文件名后缀是否在白名单中，如果在进入循环。

4. $temp_file = $_FILES['upload_file']['tmp_name']; 进入循环，给上传的文件放在一个临时的目录下，并且生成一个临时文件名

5.$img_path = $_GET['save_path']."/".rand(10, 99).date("YmdHis").".".$file_ext;（这一步是关键）

使用$_GET['save_path']接受自定义的路径，并且随机从10，99的数组在随机生成一个文件名，

在拼接上$file_Ext 前面截取的后缀名。

6.(move_uploaded_file($temp_file,$img_path)){

最终将前面保存的$temp_file临时文件移动到$img_path

借鉴一下其他师傅的

原理：

00截断利用的是php的漏洞，php的基础是C语言实现的，在C语言中认为%00是结束的符号，所以就基础了c的特性，在PHP<5.3.4的版本中，在进行存储文件时碰见了move_uploaded_file这个函数的时候，这个函数读取到hex值为00的字符，认为读取结束，就终止了后面的操作，出现00截断

绕过思路：

首先使用的是白名单，从代码中可以看出他首先对上传的文件名的后缀进行了验证。

所以在第一步上传$_FILES['upload_file']['name']，文件名的时候必须后缀是.jpg.png.gif的格式。绕过后缀名的验证后，进入到循环。最后重点他保存的文件是

$img_path = $_GET['save_path']."/".rand(10, 99).date("YmdHis").".".$file_ext;，由上传路径决定的，原参数$_GET['save_path']，save_path=../upload/。那么上传路径可控的。我们就使用%00截断，把上传的路径修改为文件名。最后利用move_uploade_file这个函数发挥出%00截断的功能。

假如我们没有使用%00截断前最终上传的文件名可能是

../upload/ 237298 .png

$_GET['save_path'] rand(10, 99).date("YmdHis") $file_ext;

使用%00截断后

../upload/1.php%00 237298 .png

$_GET['save_path'] rand(10, 99).date("YmdHis") $file_ext;

最后保存的文件就变成了

../upload/1.php
因为到%00后面的结束了

思路就是要先上传.php类型的然后%00截断路径,就可以上传成功

less12

提示还是路径可控

源代码

$is_upload = false;
$msg = null;
if(isset($_POST['submit'])){$ext_arr = array('jpg','png','gif');$file_ext = substr($_FILES['upload_file']['name'],strrpos($_FILES['upload_file']['name'],".")+1);if(in_array($file_ext,$ext_arr)){$temp_file = $_FILES['upload_file']['tmp_name'];$img_path = $_POST['save_path']."/".rand(10, 99).date("YmdHis").".".$file_ext;if(move_uploaded_file($temp_file,$img_path)){$is_upload = true;}else{$msg = "上传失败";}}else{$msg = "只允许上传.jpg|.png|.gif类型文件！";}
}

与上一关的差不多，就下面的地方不同

$img_path = $_GET['save_path']."/".rand(10, 99).date("YmdHis").".".$file_ext;

$img_path = $_POST['save_path']."/".rand(10, 99).date("YmdHis").".".$file_ext;

POST方法较为特殊，直接在明文中添加%00不会被服务器解码，得将%00进行url编码后再提交

服务器会自动解码

save_path"=../upload/4.php%00

选中%00进行编码

less13

提示

本pass检查图标内容开头2个字节

源代码

function getReailFileType($filename){$file = fopen($filename, "rb");$bin = fread($file, 2); //只读2字节fclose($file);$strInfo = @unpack("C2chars", $bin);    $typeCode = intval($strInfo['chars1'].$strInfo['chars2']);    $fileType = '';    switch($typeCode){      case 255216:            $fileType = 'jpg';break;case 13780:            $fileType = 'png';break;        case 7173:            $fileType = 'gif';break;default:            $fileType = 'unknown';}    return $fileType;
}$is_upload = false;
$msg = null;
if(isset($_POST['submit'])){$temp_file = $_FILES['upload_file']['tmp_name'];$file_type = getReailFileType($temp_file);if($file_type == 'unknown'){$msg = "文件未知，上传失败！";}else{$img_path = $UPLOAD_ADDR."/".rand(10, 99).date("YmdHis").".".$file_type;if(move_uploaded_file($temp_file,$img_path)){$is_upload = true;}else{$msg = "上传失败";}}
}

检查的是文件头部信息，通过检查文件的前2个字节，检查上传文件二进制的头部信息，来进行判断文件的类型。所以这一关修改后缀是没有用的

使用图片码进行绕过

第一种方法

将图片用编辑器打开，在最后加上<?php phpinfo();?>,图片还是可以正常打开的

第二种方法

准备好一张图片和一句话木马php文件，将其放在桌面上使用命令去合成

copy 1.png/b + 2.php/a 3.png

做好就可以直接上传，显示上传成功

less14

提示

本pass使用getimagesize()检查是否为图片文件

源代码

function isImage($filename){$types = '.jpeg|.png|.gif';if(file_exists($filename)){$info = getimagesize($filename);$ext = image_type_to_extension($info[2]);if(stripos($types,$ext)){return $ext;}else{return false;}}else{return false;}
}$is_upload = false;
$msg = null;
if(isset($_POST['submit'])){$temp_file = $_FILES['upload_file']['tmp_name'];$res = isImage($temp_file);if(!$res){$msg = "文件未知，上传失败！";}else{$img_path = $UPLOAD_ADDR."/".rand(10, 99).date("YmdHis").$res;if(move_uploaded_file($temp_file,$img_path)){$is_upload = true;}else{$msg = "上传失败";}}
}

首先知道函数的意思

getimagesize() 函数用于获取图像大小及相关信息，成功返回一个数组，失败则返回 FALSE 并产生一条 E_WARNING 级的错误信息

array getimagesize ( string $filename [, array &$imageinfo ] )

getimagesize() 函数将测定任何 GIF，JPG，PNG，SWF，SWC，PSD，TIFF，BMP，IFF，JP2，JPX，JB2，JPC，XBM 或 WBMP 图像文件的大小并返回图像的尺寸以及文件类型及图片高度与宽

$info = getimagesize($filename);

如果上传的文件是php格式就得不到图片的尺寸，就会返回错误，后面的代码就无法执行，文件就没办法成功上传

结合任务

上传一个图片马到服务器，所以上传刚刚做好的图片码看看

include.php?file=/upload/图片的链接,就可以查看了

less15

提示

本pass重新渲染了图片

源代码

$is_upload = false;
$msg = null;
if (isset($_POST['submit'])){// 获得上传文件的基本信息，文件名，类型，大小，临时文件路径$filename = $_FILES['upload_file']['name'];$filetype = $_FILES['upload_file']['type'];$tmpname = $_FILES['upload_file']['tmp_name'];$target_path=$UPLOAD_ADDR.basename($filename);// 获得上传文件的扩展名$fileext= substr(strrchr($filename,"."),1);//判断文件后缀与类型，合法才进行上传操作if(($fileext == "jpg") && ($filetype=="image/jpeg")){if(move_uploaded_file($tmpname,$target_path)){//使用上传的图片生成新的图片$im = imagecreatefromjpeg($target_path);if($im == false){$msg = "该文件不是jpg格式的图片！";}else{//给新图片指定文件名srand(time());$newfilename = strval(rand()).".jpg";$newimagepath = $UPLOAD_ADDR.$newfilename;imagejpeg($im,$newimagepath);//显示二次渲染后的图片（使用用户上传图片生成的新图片）$img_path = $UPLOAD_ADDR.$newfilename;unlink($target_path);$is_upload = true;}}else{$msg = "上传失败！";}}else if(($fileext == "png") && ($filetype=="image/png")){if(move_uploaded_file($tmpname,$target_path)){//使用上传的图片生成新的图片$im = imagecreatefrompng($target_path);if($im == false){$msg = "该文件不是png格式的图片！";}else{//给新图片指定文件名srand(time());$newfilename = strval(rand()).".png";$newimagepath = $UPLOAD_ADDR.$newfilename;imagepng($im,$newimagepath);//显示二次渲染后的图片（使用用户上传图片生成的新图片）$img_path = $UPLOAD_ADDR.$newfilename;unlink($target_path);$is_upload = true;               }}else{$msg = "上传失败！";}}else if(($fileext == "gif") && ($filetype=="image/gif")){if(move_uploaded_file($tmpname,$target_path)){//使用上传的图片生成新的图片$im = imagecreatefromgif($target_path);if($im == false){$msg = "该文件不是gif格式的图片！";}else{//给新图片指定文件名srand(time());$newfilename = strval(rand()).".gif";$newimagepath = $UPLOAD_ADDR.$newfilename;imagegif($im,$newimagepath);//显示二次渲染后的图片（使用用户上传图片生成的新图片）$img_path = $UPLOAD_ADDR.$newfilename;unlink($target_path);$is_upload = true;}}else{$msg = "上传失败！";}}else{$msg = "只允许上传后缀为.jpg|.png|.gif的图片文件！";}
}

这个函数的主要功能就是，使用上传的图片去生成一张新的图片，生成的结果会返回一个变量，

成功返回ture，失败返回false。并且这个函数，可以在他进行重新创建图片的时候，会将我们图片的信息和非图片的信息进行分离，也就是说如果我们在一张图片中加入了代码，那么他会在你上传后把这张图片在新建的时候把其中的代码筛选出来，并且去除。最后只保留你的图片信息，在进行排序重建。

图片的二次渲染的操作就是在imagecreatefrom这里进行的
图片码也是可以的，后面这道题是要重新看看的

less17

提示

需要代码审计

源代码

$is_upload = false;
$msg = null;if(isset($_POST['submit'])){$ext_arr = array('jpg','png','gif');$file_name = $_FILES['upload_file']['name'];$temp_file = $_FILES['upload_file']['tmp_name'];$file_ext = substr($file_name,strrpos($file_name,".")+1);$upload_file = $UPLOAD_ADDR . '/' . $file_name;if(move_uploaded_file($temp_file, $upload_file)){if(in_array($file_ext,$ext_arr)){$img_path = $UPLOAD_ADDR . '/'. rand(10, 99).date("YmdHis").".".$file_ext;rename($upload_file, $img_path);unlink($upload_file);$is_upload = true;}else{$msg = "只允许上传.jpg|.png|.gif类型文件！";unlink($upload_file);}}else{$msg = '上传失败！';}
}

解析

创建了一个只包含图片文件的白名单，随后提取出文件的后缀名，将文件移动至上传目录后再判断是否合法，不合法就删除。我们可以使用条件竞争方法（即在文件被删除之前访问该文件）绕过。此方法需要不停且迅速地上传、访问文件。我们使用BurpSuite和Python进行上传和访问