文件上傳之後端黑白名單繞過

2021 年 8 月 7 日
筆記
網絡安全學習

文件上傳常見驗證

1. 後綴名

黑名單：後端代碼中明確不讓上傳的文件後綴名。
比如：asp、php、jsp、aspx、cgi、war等
白名單：後端代碼中明確可以上傳文件的類型
比如：jpg、png、zip、rar、gif····

php5、phtml等格式未出現在黑名單中可以繞過，此類型與搭建平台的設置有關。

2. 文件類型

文件類型在http頭信息中又稱MIME信息。
具體表現在http頭中的content-type信息中。

3. 文件頭信息

文件頭是位於文件開頭的一段承擔一定任務的數據，一般都在開頭的部分。
常見文件的文件頭：
JPEG (jpg)，文件頭：FFD8FF
PNG (png)，　文件頭：89504E47 文件尾：0000000049454E44AE426082
GIF (gif)，文件頭：47494638
ZIP Archive (zip)，文件頭：504B0304 文件尾：00000000
TIFF (tif)，文件頭：49492A00
Windows Bitmap (bmp)，　文件頭：424D
CAD (dwg)，文件頭：41433130
Adobe Photoshop (psd)，文件頭：38425053
Rich Text Format (rtf)，文件頭：7B5C727466
XML (xml)，文件頭：3C3F786D6C
HTML (html)，文件頭：68746D6C3E
Email [thorough only] (eml)，文件頭：44656C69766572792D646174653A
Outlook Express (dbx)，文件頭：CFAD12FEC5FD746F
Outlook (pst)，文件頭：2142444E
MS Word/Excel (xls.or.doc)，文件頭：D0CF11E0
MS Access (mdb)，文件頭：5374616E64617264204A
WordPerfect (wpd)，文件頭：FF575043
Adobe Acrobat (pdf)，文件頭：255044462D312E
Quicken (qdf)，文件頭：AC9EBD8F
Windows Password (pwl)，文件頭：E3828596
RAR Archive (rar)，文件頭：52617221
Wave (wav)，文件頭：57415645
AVI (avi)，文件頭：41564920
Real Audio (ram)，文件頭：2E7261FD
Real Media (rm)，文件頭：2E524D46
MPEG (mpg)，文件頭：000001BA
MPEG (mpg)，文件頭：000001B3
Quicktime (mov)，文件頭：6D6F6F76
Windows Media (asf)，文件頭：3026B2758E66CF11
MIDI (mid)，文件頭：4D546864

相關靶場分析

1. upload-labs第2關(MIME繞過)

查看源碼：

$is_upload = false;
$msg = null;
if (isset($_POST['submit'])) {
    if (file_exists(UPLOAD_PATH)) {
        if (($_FILES['upload_file']['type'] == 'image/jpeg') || ($_FILES['upload_file']['type'] == 'image/png') || ($_FILES['upload_file']['type'] == 'image/gif')) {
            $temp_file = $_FILES['upload_file']['tmp_name'];
            $img_path = UPLOAD_PATH . '/' . $_FILES['upload_file']['name']            
            if (move_uploaded_file($temp_file, $img_path)) {
                $is_upload = true;
            } else {
                $msg = '上傳出錯！';
            }
        } else {
            $msg = '文件類型不正確，請重新上傳！';
        }
    } else {
        $msg = UPLOAD_PATH.'文件夾不存在,請手工創建！';
    }
}

通過代碼分析，此關是判斷上傳的文件類型是否在白名單中，在就上傳，否則上傳失敗。
繞過方法為修改上傳文件類型為白名單中的任意一個即可。

2. upload-labs第3關(特殊解析後綴繞過)

查看源碼：

$is_upload = false;
$msg = null;
if (isset($_POST['submit'])) {
    if (file_exists(UPLOAD_PATH)) {
        $deny_ext = array('.asp','.aspx','.php','.jsp');//拒絕的後綴名
        $file_name = trim($_FILES['upload_file']['name']);//去除接收過來的文件名中的空格
        $file_name = deldot($file_name);//刪除文件名末尾的點
        $file_ext = strrchr($file_name, '.');//將「.」前面的內容截斷
        $file_ext = strtolower($file_ext); //轉換為小寫
        $file_ext = str_ireplace('::$DATA', '', $file_ext);//去除字符串::$DATA
        $file_ext = trim($file_ext); //收尾去空

        if(!in_array($file_ext, $deny_ext)) {
            $temp_file = $_FILES['upload_file']['tmp_name'];
            $img_path = UPLOAD_PATH.'/'.date("YmdHis").rand(1000,9999).$file_ext;            
            if (move_uploaded_file($temp_file,$img_path)) {
                 $is_upload = true;
            } else {
                $msg = '上傳出錯！';
            }
        } else {
            $msg = '不允許上傳.asp,.aspx,.php,.jsp後綴文件！';
        }
    } else {
        $msg = UPLOAD_PATH . '文件夾不存在,請手工創建！';
    }
}

過濾條件為：

過濾後綴名asp,aspx,php,jsp
去除接收過來的文件名中的空格
刪除文件名末尾的點
將「.」前面的內容截斷
後綴名轉換為小寫
去除文件後綴含有::$DATA字符串變為空
收尾去掉空格
繞過方法為：使用特殊的後綴名，php5,phml等
原因是apache服務器可以解析php5、php3、phtml格式的文件為php格式的文件。

3. upload-labs第4關(.htaccess上傳漏洞)

源碼分析：

$is_upload = false;
$msg = null;
if (isset($_POST['submit'])) {
    if (file_exists(UPLOAD_PATH)) {
        $deny_ext = array(".php",".php5",".php4",".php3",".php2",".php1",".html",".htm",".phtml",".pht",".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",".ini");
        $file_name = trim($_FILES['upload_file']['name']);
        $file_name = deldot($file_name);//刪除文件名末尾的點
        $file_ext = strrchr($file_name, '.');
        $file_ext = strtolower($file_ext); //轉換為小寫
        $file_ext = str_ireplace('::$DATA', '', $file_ext);//去除字符串::$DATA
        $file_ext = trim($file_ext); //收尾去空

        if (!in_array($file_ext, $deny_ext)) {
            $temp_file = $_FILES['upload_file']['tmp_name'];
            $img_path = UPLOAD_PATH.'/'.$file_name;
            if (move_uploaded_file($temp_file, $img_path)) {
                $is_upload = true;
            } else {
                $msg = '上傳出錯！';
            }
        } else {
            $msg = '此文件不允許上傳!';
        }
    } else {
        $msg = UPLOAD_PATH . '文件夾不存在,請手工創建！';
    }
}

可以看到限制上傳的文件後綴名增多。
我們在本地創建.htaccess文件，

先將此文件上傳至服務器。目的是在.htaccess文件所在的目錄中所有格式文件按.htaccess文件規定的方式執行。
再上傳一個名為shana.jpg的馬即可。
訪問//127.0.0.1/upload-labs/upload/shana.jpg

4. upload-labs第5關(只進一次過濾檢驗)

源碼分析：

$is_upload = false;
$msg = null;
if (isset($_POST['submit'])) {
    if (file_exists(UPLOAD_PATH)) {
        $deny_ext = array(".php",".php5",".php4",".php3",".php2",".html",".htm",".phtml",".pht",".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);//刪除文件名末尾的點
        $file_ext = strrchr($file_name, '.');
        $file_ext = strtolower($file_ext); //轉換為小寫
        $file_ext = str_ireplace('::$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)) {
            $temp_file = $_FILES['upload_file']['tmp_name'];
            $img_path = UPLOAD_PATH.'/'.$file_name;
            if (move_uploaded_file($temp_file, $img_path)) {
                $is_upload = true;
            } else {
                $msg = '上傳出錯！';
            }
        } else {
            $msg = '此文件類型不允許上傳！';
        }
    } else {
        $msg = UPLOAD_PATH . '文件夾不存在,請手工創建！';
    }
}

可知，過濾掉更多後綴名，且將.htaccess也過濾掉了。
只進行了一次過濾檢驗，可以使用”.php. .”繞過

5. upload-labs第6關(大小寫繞過)

源碼：

$is_upload = false;
$msg = null;
if (isset($_POST['submit'])) {
    if (file_exists(UPLOAD_PATH)) {
        $deny_ext = array(".php",".php5",".php4",".php3",".php2",".html",".htm",".phtml",".pht",".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",".ini");
        $file_name = trim($_FILES['upload_file']['name']);
        $file_name = deldot($file_name);//刪除文件名末尾的點
        $file_ext = strrchr($file_name, '.');
        $file_ext = str_ireplace('::$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)) {
            $temp_file = $_FILES['upload_file']['tmp_name'];
            $img_path = UPLOAD_PATH.'/'.date("YmdHis").rand(1000,9999).$file_ext;
            if (move_uploaded_file($temp_file, $img_path)) {
                $is_upload = true;
            } else {
                $msg = '上傳出錯！';
            }
        } else {
            $msg = '此文件類型不允許上傳！';
        }
    } else {
        $msg = UPLOAD_PATH . '文件夾不存在,請手工創建！';
    }
}

源碼中沒有大小寫過濾。
上傳”.PHp”可繞過

6. upload-labs第7關(後綴名末尾加空格繞過)

源碼;

$is_upload = false;
$msg = null;
if (isset($_POST['submit'])) {
    if (file_exists(UPLOAD_PATH)) {
        $deny_ext = array(".php",".php5",".php4",".php3",".php2",".html",".htm",".phtml",".pht",".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",".ini");
        $file_name = $_FILES['upload_file']['name'];
        $file_name = deldot($file_name);//刪除文件名末尾的點
        $file_ext = strrchr($file_name, '.');
        $file_ext = strtolower($file_ext); //轉換為小寫
        $file_ext = str_ireplace('::$DATA', '', $file_ext);//去除字符串::$DATA
        
        if (!in_array($file_ext, $deny_ext)) {
            $temp_file = $_FILES['upload_file']['tmp_name'];
            $img_path = UPLOAD_PATH.'/'.date("YmdHis").rand(1000,9999).$file_ext;
            if (move_uploaded_file($temp_file,$img_path)) {
                $is_upload = true;
            } else {
                $msg = '上傳出錯！';
            }
        } else {
            $msg = '此文件不允許上傳';
        }
    } else {
        $msg = UPLOAD_PATH . '文件夾不存在,請手工創建！';
    }
}

源碼中沒有刪除後綴名末尾空格，可增加空格進行繞過。

7. upload-labs第8關(後綴名加點繞過)

源碼：

$is_upload = false;
$msg = null;
if (isset($_POST['submit'])) {
    if (file_exists(UPLOAD_PATH)) {
        $deny_ext = array(".php",".php5",".php4",".php3",".php2",".html",".htm",".phtml",".pht",".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",".ini");
        $file_name = trim($_FILES['upload_file']['name']);
        $file_ext = strrchr($file_name, '.');
        $file_ext = strtolower($file_ext); //轉換為小寫
        $file_ext = str_ireplace('::$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)) {
            $temp_file = $_FILES['upload_file']['tmp_name'];
            $img_path = UPLOAD_PATH.'/'.$file_name;
            if (move_uploaded_file($temp_file, $img_path)) {
                $is_upload = true;
            } else {
                $msg = '上傳出錯！';
            }
        } else {
            $msg = '此文件類型不允許上傳！';
        }
    } else {
        $msg = UPLOAD_PATH . '文件夾不存在,請手工創建！';
    }
}

分析得缺少刪除末尾的點的操作。
抓包加點進行過濾。

8. upload-labs第9關(::$DATA繞過)

源碼：

$is_upload = false;
$msg = null;
if (isset($_POST['submit'])) {
    if (file_exists(UPLOAD_PATH)) {
        $deny_ext = array(".php",".php5",".php4",".php3",".php2",".html",".htm",".phtml",".pht",".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",".ini");
        $file_name = trim($_FILES['upload_file']['name']);
        $file_name = deldot($file_name);//刪除文件名末尾的點
        $file_ext = strrchr($file_name, '.');
        $file_ext = strtolower($file_ext); //轉換為小寫
        $file_ext = trim($file_ext); //首尾去空
        
        if (!in_array($file_ext, $deny_ext)) {
            $temp_file = $_FILES['upload_file']['tmp_name'];
            $img_path = UPLOAD_PATH.'/'.date("YmdHis").rand(1000,9999).$file_ext;
            if (move_uploaded_file($temp_file, $img_path)) {
                $is_upload = true;
            } else {
                $msg = '上傳出錯！';
            }
        } else {
            $msg = '此文件類型不允許上傳！';
        }
    } else {
        $msg = UPLOAD_PATH . '文件夾不存在,請手工創建！';
    }
}

分析得，少了去除文件名中的::$DATA字符串。
後綴名加::$DATA即可繞過。

9. upload-labs第10關(一次驗證繞過)

方法同第5關

10. upload-labs第11關(後綴名重寫繞過)

源碼:

$is_upload = false;
$msg = null;
if (isset($_POST['submit'])) {
    if (file_exists(UPLOAD_PATH)) {
        $deny_ext = array("php","php5","php4","php3","php2","html","htm","phtml","pht","jsp","jspa","jspx","jsw","jsv","jspf","jtml","asp","aspx","asa","asax","ascx","ashx","asmx","cer","swf","htaccess","ini");

        $file_name = trim($_FILES['upload_file']['name']);
        $file_name = str_ireplace($deny_ext,"", $file_name);
        $temp_file = $_FILES['upload_file']['tmp_name'];
        $img_path = UPLOAD_PATH.'/'.$file_name;        
        if (move_uploaded_file($temp_file, $img_path)) {
            $is_upload = true;
        } else {
            $msg = '上傳出錯！';
        }
    } else {
        $msg = UPLOAD_PATH . '文件夾不存在,請手工創建！';
    }
}

分析得，若上傳是黑名單中的後綴則刪除後綴名。
只需複寫後綴名即可繞過。

11. upload-labs第12關(%00截斷)

$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 = '上傳出錯！';
        }
    } else{
        $msg = "只允許上傳.jpg|.png|.gif類型文件！";
    }
}

分析是取最後一個點後面的格式與白名單進行對比。
使用get傳參，可用%00截斷。繞過

Tags: 網絡安全學習