WebApp Sec mailing list archives
Re: File Upload with changed extension
From: Guillermo Caminer <flaco.webappsec () gmail com>
Date: Tue, 02 Dec 2014 22:42:29 -0300
Hi! There could be a risk involved, if: 1) The image is uploaded inside the Document Root 2) Have some malicious code inside (ex: a php shell) that is not validated 3) The Web Server somehow executes this malicious code (for example, you can put php code inside a GIF, after the magic number, and the web app include/require this file in a php script, then the php engine will execute the php code when it sees the php opening tag, even if it's inside the image) Also, beware of the null byte, or example, can you upload a filename like this phpShell.php%00.jpg? The best practice is: a) Always upload outside the DocRoot b) Do not trust Content-type and filename headers nor the magic number c) Validate the content of the file d) Scan the file with an antivirus e) Be careful if you include/require the file Hope it helps! Best regards. On 02/12/14 15:44, Jyotiranjan Acharya wrote:
If you are able to upload a file with a changed extension, then will that be a problem? For example, you can not ,in any way, upload a .exe or .php/.jsp/.asp file directly into a web App, but you can by changing their extension to .JPG. What is the risk in such a case? This list is sponsored by Cenzic -------------------------------------- Let Us Hack You. Before Hackers Do! It's Finally Here - The Cenzic Website HealthCheck. FREE. Request Yours Now! http://www.cenzic.com/2009HClaunch_Securityfocus --------------------------------------
This list is sponsored by Cenzic -------------------------------------- Let Us Hack You. Before Hackers Do! It's Finally Here - The Cenzic Website HealthCheck. FREE. Request Yours Now! http://www.cenzic.com/2009HClaunch_Securityfocus --------------------------------------
Current thread:
- File Upload with changed extension Jyotiranjan Acharya (Dec 02)
- Re: File Upload with changed extension Guillermo Caminer (Dec 02)
- Re: File Upload with changed extension Tobias Wassermann (Dec 03)
- Re: File Upload with changed extension Seth Art (Dec 03)
- Re: File Upload with changed extension Paul Burbage (Dec 03)
- Re: File Upload with changed extension Tobias Wassermann (Dec 03)
- Re: File Upload with changed extension Guillermo Caminer (Dec 02)
- Re: File Upload with changed extension Michal Zalewski (Dec 03)
- Re: File Upload with changed extension Robin Wood (Dec 04)