These uploads might consume all resources the server has available which will result in a DOS attack. * check if you can upload a shell.php but with the header of a png file 89 50 4E 47 0D 0A 1A 0A and the mimetype set to image/png. Confirm the change by issuing file to see if the edit was successful. in php, insert new bytes with ctrl-a, write over the new bytes and save/exit like in nano. * the null-byte \00 in a string has a special meaning and lead to various vulnerabilities. characters, resulting in %2e%2e%2f or %252e%252e%252f respectively. * you can sometimes bypass this kind of sanitization by url encoding, or even double url encoding, the. also check what happens if the value is encoded. * check what happens if the filename contains. * the server will form the storage path of the file by combining the storage folder with the filename. * check if the name of the uploaded file is modified (added timestamp or guid) or if it will replace/overwrite an existing file. * the server has to give the stored file a name. * check if the uploaded file is stored in an (public) accessible folder. * simple websites will run on a single server and thus, store the files on the same server as the website is served from. Once the file is sent to the server a backend filter might be applied.īackend filtering might check for file -name, -size, mimetype and -content.īe aware that these checks might apply to multiple files in a single request.ĭepending on the filesize the request might span over multiple multi-part requests. If the web application requires javascript use Burp/ZAProxy to modify the responded javascript to allow all file/mime types and disable all security checks to ease your pentester life.įrontend filtering might check for file -name, -size, mimetype, modification date and -content. Nowadays modern web applications tend to check file uploads on the client side via javascript and html-annotations before they are sent to the server.īecause javascript is executed on the clientside it's quite easy to omit it completely or catch the required data for the upload-request and issue it ourself. Upload an allowed file and catch request/response with ZAProxy/Burp. Check with gobuster dir -url -w /usr/share/seclists/Discovery/Web-Content/common.txt what directories exists.Ĭheck with echo | httpx -tech-detect -title -status-code -path /,/login what technology the sub/site is using.
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