Can somebody tell me how to prevent exe file from being uploaded in a website , even if exe file is inside zip file( exe file in a new folder and new folder is then zipped and uploaded)?
Allow the users to upload the file (if is ZIP) and do a server-side check by unpacking the archive and evaluating its content.
Short answer: you can't.
Pedantic answer: Don't have users upload files.
Long answer:
What code is handling this uploaded file? What are you doing with it? This is where the security needs to happen. You can explicitly check the file extension in the post handler, but that only gets you so far, as you've already determined.
Some tips:
-Drop files in a secure location outside the web root.
-Don't give your ASP.NET process user more permissions than it needs
-Give them unique server-generated names and proper extensions.
-Do not call Shell.Execute on user-uploaded files. Duh.
What exactly are you trying to prevent here? Your question is difficult to answer as-is.
Related
In my asp.net web application, I read the xml file for obtaining a key. If file is not present I show a form to enter the key details and then create the file.
First problem: My app does not recognize the file even if its there.
Second problem: I am running application on the server. When writing, rather overwriting the file, browser shows the username, password prompt before writing the file. If I enter admin credentials it allows to create a file.
I have checked all possible combinations of permissions on the file / folders, but could not resolve the problem.
Any ideas, what I could be missing here?
You read the xml file but is it as a part of your solution? If yes, are you reading it through relative path i.e. are you using Server.MapPath to read it like Server.MapPath("~/Files.test.xml")? Once you use relative path, I don't think it will ask you credentials as it still is in your project directory.
It should work. I am also reading and writing files in my web application.
If it still does not work, please tell me the way you are reading file.
Thanks,
If I'm hosting a website, say at http://www.example.com, how can I find files that are in the same folder as index.html if I DON'T know the filenames?
So for example, if there are these files in there:
http://www.example.com/test.txt
http://www.example.com/test1.txt
Can anyone see this list of files? If so, how can I hide them, but make each one accessible to someone who knows the names? I don't want to use a password system, if possible.
If you put index.html in that directory, so no files will be listed. If you allow to upload to that directory, so i can upload some php script to list all files in directory. IF you don't know file name, you can try to guess it :)
You can use bruteforce tools such as dirbuster, or you can look at the "/robots.txt" file for some clues on what's on the website.
By the way, you should keep in mind that most of web servers nowadays have rights management implemented, so even if there is such file on the server it may not allow you access to it without authentication.
Some hosting providers provide an option to specify whether directory listings are allowed. If enabled, and a client requests a URL for a folder that does not contain a default HTML file (index.html, default.html, default.aspx, etc), then the web server will serve up an HTML file containing a listing of the files in that folder. It is rare that this option is ever enabled, though.
but you should be accurate while inserting names of files in URL or else you can use pen-test tool which will list out some of the names for free.for attempts ot full listing of files you'll need to be a paid member i guess
Suppose we have a example.exe file.
we first put that file in a new folder
and then zip that folder with any zipping software,
Can we prevent that zipped folder upload in a website?
how can we do that?
You cannot prevent it, because you can't tell what the browser is going to submit before it submits it. All you can do is when the file arrives on the server, check the file extension - if it's an exe (or a .zip and you open it up and find an .exe) then reject it.
You can use something like SWFupload to get a handle on the file before it's uploaded, but the best that'll do is tell you the name of the file.
Besides, they could just take "example.exe" change the name to "example.txt" and still upload it...
You check on the server. Checking with javascript in form.onsubmit is dumb because its quite simple to post a form with a file to the same URL and skip your super secure javascript powered page.
In my asp.net web application, I have a folder in which I have a few html and jpeg files. some of these files do not need a user to login while the others do. How do I exclude the files that are free for view to be displayed without logging in while still maintaining the user to login for viewing other files in the same folder using just the config file. I wasnt able to find something relevant in the config file or maybe I overlooked it. If anyone knows please reply.
Thanks.
I've tried to answer this as well as I can but the sentence:
How do I exclude the files that are free for view to be displayed without logging in while still maintaining the user to login for viewing other files in the same folder using just the config file.
..is a bit confusing!
The files that need to be authenticated are the ones that are handled by the asp.net handler such as .aspx files. jpegs and other static files bypass this so can be viewed without authentication. The handler aspnet_isapi only handles certain files but you can configure it to handle more file extensions (or all files) by configuring extension mappings in IIS.
Personally, I would put all files I wanted to be unprotected in a folder with permissions to allow anyone to view that folder, set the aspnet_isapi handler to handle all files and then protect your other folders according to your application's needs.
Depending on what you want to do (as your question isn't that clear), you may or may not be able to achieve what you want just from the config file but hopefully this answer will give you the information you need to make your own conclusions on that.
The server is IIS7.
Is there a way to disable web.config files in subfolders?
I am asking because, I have a folder on the web server that is for uploads. When someone uploads files, a new folder is created for the user's session and the files they upload go in the folder.
So the path to uploads would be like this:
~/uploads/3F2504E0-4F89-11D3-9A0C-0305E82C3301/somefile.txt
In the ~/uploads/ directory there is a web.config file that removes all http handlers except the static file handler and adds a wildcard mime type. So every file that a user uploads will only ever be served statically.
If a user uploads a web.config file, I want to disallow any of the settings in that file from being applied.
How can I do this?
EDIT
Could I just make the upload folder an application that is a member of an application pool configured to run in Classic mode instead of Integrated Pipeline mode? That way it wouldn't even care about a web.config file.
EDIT 2
Is there another type of webserver I could install for serving all files statically? I could just access the files through a different port. Is there some software that I can be sure wont run any scripts and is safe.
I simply wouldn't allow them to upload a file with that name. In fact, I normally wouldn't trust any filename that the user gave me... makes a great candidate for an injection-style attack.
Ok I have a different angle on this...
What if your uploads folder was not part of the website and instead part of the file system? This way ASP.NET is not processing requests to the folder and thus web.config wouldn't be loaded by the ASP.NET runtime.
You'd have to give your app pool's account read/write access to the file system where these files are stored, but I think it better fits what you're trying to accomplish.
Obviously it could be done in code.
If the folders always exist, you could pre-populate with a web.config with no (significant) content and an ACL to ensure it cannot be overwritten, but looking at the path it I suspect you create the upload folders dynamically which means this would not work.
I don't believe there is a way to tell IIS not to use a web.config (but I could be wrong). Personally, I would add a check to my save code and rename the file.
Why not just check the filename first to prevent the user from uploading a file named web.config? You're probably going to want to check for other things too before allowing the upload - files that are too big, etc.