DVWA 实验报告：5、文件上传 File Upload

文章更新于：2020-05-16

一、安全等级：Low

1.1、源码

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' ] );

    // Can we move the file to the upload folder?
    if( !move_uploaded_file( $_FILES[ 'uploaded' ][ 'tmp_name' ], $target_path ) ) {
        // No
        echo '
Your image was not uploaded.
';
    }
    else {
        // Yes!
        echo "
{$target_path} succesfully uploaded!
";
    }
}

?>

1.2、攻击

这时我们写一个一句话木马测试上传。

ok
 @eval($_POST['test']) ?>

我们根据提示的路径尝试访问：

访问成功，接下来测试是否可用。

这里使用蚁剑连接：

添加之后，双击数据连接成功：

二、安全等级：Medium

2.1、源码

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" ) &&
        ( $uploaded_size < 100000 ) ) {

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

?> 

2.2、攻击

1. 我们发现 php 文件上传不上去了

2.使用 BP 拦截改后缀

改掉后缀之后实际上传的是 test.php 文件，且可正常解析、连接。

3. 至于上传 .png 后缀之后再用文件去包含。
   我测试的时候也正常解析了，但是去连的时候，因为那个页面需要登录才能看到，所以返回数据为空，连接失败。

4. .php 文件 + .png 文件的图片马，我没有测试成功。

三、安全等级：High

3.1、源码

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);
    $uploaded_size = $_FILES[ 'uploaded' ][ 'size' ];
    $uploaded_tmp  = $_FILES[ 'uploaded' ][ 'tmp_name' ];

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

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

?> 

3.2、攻击

使用 合成图片马的方式进行攻击

copy a.jpg/b + b.php/a  hack.jpg

我没有测试成功。

四、安全等级：Impossible

4.1、源码

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;
    $temp_file     = ( ( ini_get( 'upload_tmp_dir' ) == '' ) ? ( sys_get_temp_dir() ) : ( ini_get( 'upload_tmp_dir' ) ) );
    $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 );
            imagejpeg( $img, $temp_file, 100);
        }
        else {
            $img = imagecreatefrompng( $uploaded_tmp );
            imagepng( $img, $temp_file, 9);
        }
        imagedestroy( $img );

        // 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 "
${target_file} succesfully uploaded!
";
        }
        else {
            // No
            echo '
Your image was not uploaded.
';
        }

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

// Generate Anti-CSRF token
generateSessionToken();

?> 

4.2、攻击

Impossible级别的代码对上传文件进行了重命名（为md5值，导致%00截断无法绕过过滤规则），
加入Anti-CSRF token防护CSRF攻击，
同时对文件的内容作了严格的检查，
导致攻击者无法上传含有恶意脚本的文件。

五、Enjoy！