DVWA——File Upload

File Upload

Low

<?php 

if( isset( $_POST[ 'Upload' ] ) ) { 
    // Where are we going to be writing to? 
    $target_path  = DVWA_WEB_PAGE_TO_ROOT . "hackable/uploads/"; 
    $target_path .= basename( $_FILES[ 'uploaded' ][ 'name' ] );                         //basename() 函數返回路徑中的文件名部分

    // Can we move the file to the upload folder? 
    if( !move_uploaded_file( $_FILES[ 'uploaded' ][ 'tmp_name' ], $target_path ) ) {     //move_uploaded_file() 函數將上傳的文件移動到新位置
        // No 
        echo '<pre>Your image was not uploaded.</pre>'; 
    } 
    else { 
        // Yes! 
        echo "<pre>{$target_path} succesfully uploaded!</pre>"; 
    } 
} 

?> 

服務器對上傳文件的類型沒有做任何過濾，存在上傳漏洞

可以上傳一句話木馬然後菜刀連接

Medium

<?php 

if( isset( $_POST[ 'Upload' ] ) ) { 
    // Where are we going to be writing to? 
    $target_path  = DVWA_WEB_PAGE_TO_ROOT . "hackable/uploads/"; 
    $target_path .= basename( $_FILES[ 'uploaded' ][ 'name' ] ); 

    // File information 
    $uploaded_name = $_FILES[ 'uploaded' ][ 'name' ]; 
    $uploaded_type = $_FILES[ 'uploaded' ][ 'type' ]; 
    $uploaded_size = $_FILES[ 'uploaded' ][ 'size' ]; 

    // Is it an image? 
    if( ( $uploaded_type == "image/jpeg" || $uploaded_type == "image/png" ) &&      //限制文件上傳類型爲圖片格式並且限制了尺寸
        ( $uploaded_size < 100000 ) ) { 

        // Can we move the file to the upload folder? 
        if( !move_uploaded_file( $_FILES[ 'uploaded' ][ 'tmp_name' ], $target_path ) ) { 
            // No 
            echo '<pre>Your image was not uploaded.</pre>'; 
        } 
        else { 
            // Yes! 
            echo "<pre>{$target_path} succesfully uploaded!</pre>"; 
        } 
    } 
    else { 
        // Invalid file 
        echo '<pre>Your image was not uploaded. We can only accept JPEG or PNG images.</pre>'; 
    } 
} 

?> 

可以上傳一句話木馬，改後綴爲.png

但這樣並不能直接菜刀連接，還需要抓包改filename爲.php格式纔可以

除此之外，在php版本小於5.3.4的服務器中，當Magic_quote_gpc=Off時，可以使用%00截斷

把文件名後綴改爲.php%00.png即可通過文件類型檢查
抓包可以看到文件類型爲image/png

但是服務器卻認爲它是一個php文件解析

High

<?php 

if( isset( $_POST[ 'Upload' ] ) ) { 
    // Where are we going to be writing to? 
    $target_path  = DVWA_WEB_PAGE_TO_ROOT . "hackable/uploads/"; 
    $target_path .= basename( $_FILES[ 'uploaded' ][ 'name' ] ); 

    // File information 
    $uploaded_name = $_FILES[ 'uploaded' ][ 'name' ]; 
    $uploaded_ext  = substr( $uploaded_name, strrpos( $uploaded_name, '.' ) + 1);     //獲取文件擴展名.之後的名字，strrpos()返回字符串'.'在另一字符串$uploaded_name最後一次出現的位置
    $uploaded_size = $_FILES[ 'uploaded' ][ 'size' ]; 
    $uploaded_tmp  = $_FILES[ 'uploaded' ][ 'tmp_name' ];                             //接受臨時文件路徑

    // Is it an image? 
    if( ( strtolower( $uploaded_ext ) == "jpg" || strtolower( $uploaded_ext ) == "jpeg" || strtolower( $uploaded_ext ) == "png" ) &&     //驗證擴展名和文件大小
        ( $uploaded_size < 100000 ) && 
        getimagesize( $uploaded_tmp ) ) {         //getimagesize() 函數用於獲取圖像大小及相關信息，成功返回一個數組，如果沒有圖片頭，則會報錯
        // Can we move the file to the upload folder? 
        if( !move_uploaded_file( $uploaded_tmp, $target_path ) ) { 
            // No 
            echo '<pre>Your image was not uploaded.</pre>'; 
        } 
        else { 
            // Yes! 
            echo "<pre>{$target_path} succesfully uploaded!</pre>"; 
        } 
    } 
    else { 
        // Invalid file 
        echo '<pre>Your image was not uploaded. We can only accept JPEG or PNG images.</pre>'; 
    } 
} 

?> 

代碼限制了文件上傳的類型，同時對文件的類型做了判斷
可以將圖片和一句話木馬合成圖片木馬上傳

後用菜刀連接?page=file:///文件路徑/hack.jpg，即可拿到webshell

Impossible

<?php 

if( isset( $_POST[ 'Upload' ] ) ) { 
    // Check Anti-CSRF token 
    checkToken( $_REQUEST[ 'user_token' ], $_SESSION[ 'session_token' ], 'index.php' ); 


    // File information 
    $uploaded_name = $_FILES[ 'uploaded' ][ 'name' ]; 
    $uploaded_ext  = substr( $uploaded_name, strrpos( $uploaded_name, '.' ) + 1); 
    $uploaded_size = $_FILES[ 'uploaded' ][ 'size' ]; 
    $uploaded_type = $_FILES[ 'uploaded' ][ 'type' ]; 
    $uploaded_tmp  = $_FILES[ 'uploaded' ][ 'tmp_name' ]; 

    // Where are we going to be writing to? 
    $target_path   = DVWA_WEB_PAGE_TO_ROOT . 'hackable/uploads/'; 
    //$target_file   = basename( $uploaded_name, '.' . $uploaded_ext ) . '-'; 
    $target_file   =  md5( uniqid() . $uploaded_name ) . '.' . $uploaded_ext;               //uniqid() 函數基於以微秒計的當前時間，生成一個唯一的 ID
    $temp_file     = ( ( ini_get( 'upload_tmp_dir' ) == '' ) ? ( sys_get_temp_dir() ) : ( ini_get( 'upload_tmp_dir' ) ) );        //ini_get()獲取php.ini裏的環境變量的值
    $temp_file    .= DIRECTORY_SEPARATOR . md5( uniqid() . $uploaded_name ) . '.' . $uploaded_ext; 

    // Is it an image? 
    if( ( strtolower( $uploaded_ext ) == 'jpg' || strtolower( $uploaded_ext ) == 'jpeg' || strtolower( $uploaded_ext ) == 'png' ) && 
        ( $uploaded_size < 100000 ) && 
        ( $uploaded_type == 'image/jpeg' || $uploaded_type == 'image/png' ) && 
        getimagesize( $uploaded_tmp ) ) { 

        // Strip any metadata, by re-encoding image (Note, using php-Imagick is recommended over php-GD) 
        if( $uploaded_type == 'image/jpeg' ) { 
            $img = imagecreatefromjpeg( $uploaded_tmp );                  //imagecreatefromjpeg()返回圖片文件的圖像標示，失敗返回false
            imagejpeg( $img, $temp_file, 100);                           //imagejpeg ( image , filename , quality)從image圖像中以filename爲文件名創建一個JPEG圖像
        } 
        else { 
            $img = imagecreatefrompng( $uploaded_tmp ); 
            imagepng( $img, $temp_file, 9); 
        } 
        imagedestroy( $img );    //函數銷燬圖像資源

        // Can we move the file to the web root from the temp folder? 
        if( rename( $temp_file, ( getcwd() . DIRECTORY_SEPARATOR . $target_path . $target_file ) ) ) { 
            // Yes! 
            echo "<pre><a href='${target_path}${target_file}'>${target_file}</a> succesfully uploaded!</pre>"; 
        } 
        else { 
            // No 
            echo '<pre>Your image was not uploaded.</pre>'; 
        } 

        // Delete any temp files 
        if( file_exists( $temp_file ) ) 
            unlink( $temp_file ); 
    } 
    else { 
        // Invalid file 
        echo '<pre>Your image was not uploaded. We can only accept JPEG or PNG images.</pre>'; 
    } 
} 

// Generate Anti-CSRF token 
generateSessionToken(); 

?> 

Impossible代碼已經對文件進行重命名操作。加入了Anti-CSRF token防止CSRF攻擊。