I have a scenario where a user will have access to a one-time-url.
When the user clicks on the URL, specific files will be available to that user.
I have many files on the site but would only like certain files to be accessible by that user.
I have though about generating an authenticated cookie and using forms based auth and applying permissions to a certain folder, but I need authorization on indiviual files. and the files will constintly be changing.
What would be the best way to give a user only access to specific files? (I won't display the other files, but I still do not want other files available if they are typed in the URL)
I would create an .ashx (handler file) and have that serve the files to the user (load into memory and then write the contents out by pushing the file to the content stream). That way the end user never has permissions to the actual files on the system but can still access them. Your code can then control when and how long each file is available to a user.
I would provide an abstraction around the actual file retrieval. That way the user never sees file name. Something like www.example.com/File.aspx?id=SOMERANDOMGUID
That RANDOMGUID could reference a file in the back end.
If you have lots of disk space, one way to accomplish this is to copy the files to a randomly-generated folder, so that the URL to a user's files is unique for each user.
I think it would be easier if your files are associated with an ID and the path is kept in the database. This way you can pull the files using the ID.
Related
I've run into a problem using Moodle 3.2. I'm uploading mp3-files to be played in a quiz. I have the license to use those files for that specific purpose, but I am not the owner. Thus, I would like to ensure that nobody without a Moodle account can access these files.
However, the path to the files can be extracted from the source code and once you have the path, anybody can access the file. Is there any way to protect the file so only registered users can access it, even if they have the direct path?
Thank you so much!
All the best
Dom
EDIT: I've learned that files actually are encrypted by login - I just had the login cookie remaining in several browsers and thus was able to access them.
Are the files served by moodleinstallation/pluginfile.php/? This would include login/permission checks
In my asp.net website, users can upload multiple files, which reside in 'upload' folder on server's hard drive. I am saving the files by renaming them with username + original file name
Example : if I upload file 'user.text' and my code is 1000, then the file will be saved in upload folder with name '1000_user.Text'. This is for identification of file against a particular user.
Now, when admin logs in application and selects a user, he should be able to see all files uploaded by him/her. Files should be in downloadable format to him.
How can I achieve the same? I have totally no idea, how to go for it ?
This is not how you ask a question on SO. Anyway already a piece of advice :
Store your files OUTSIDE of the webroot, and use a script in your website to get the files and render it to the user. This is for security reason : if someone manages to upload a malicious file, you don't want him to be able to execute it from the web.
Store file info and upload info in a database : who uploaded what and when ? Relying on file name isn't a good idea. You could also store the file in the database eventually (as a BLOB), but I prefer the good old filesystem
I can suggest you couple of ways based on feasibility. Approach 1 - If you can make database changes, when user is uploading a file you should save dynamically generated filename against the user in database. This way when admin logs in and wants to see all the files uploaded by user, you just need to make a database query and show them in a grid. When user clicks on the file name, you can fetch the file from harddisk and allow it to download to admin.
If database change is not feasible, your task will be more difficult. You will have to query in your directory with username in all the files. You can make use of LINQ to make this task little easier to you. Once you have got all the list, show it to admin.
I would recommend you to save metadata about the file on the database (like original file name and username). Then you could use this metadata to find the files that the user have uploaded. Give the files a file name on disk that is based on a unique ID in the database table. That way a user can upload several files with the same name. Make sure that this folder is not located within you application so that they are accessible with a url for security reasons.
The most recommended way to achieve this is to use a database, it is same as a module of Gallery where a user has albums and some pictures in albums. Admin can view each user's album and pictures in the album. you have to introduce two tables in your database. I having the category information of files being uploaded (master table) and other table having the info about the files itself (details table).
The other way is to create a hierarchal folder directory for each user for file categories in your application and then recursively read the directories and fields and then list them up to show them to application users. this would be costly i guess when number of files will increase.
I have a website that reads an xml file, caches the file's object model, and i have web pages that read from the cache. I now want to make that xml file writable by the application pool account that runs the website so it can be managed by the website.
I've heard from peers that making that file writable is a security risk because if a hacker were to hack the website, he could potentially use the app pool account to overwrite that xml file and put whatever he/she wants into that file. However, since that file is read by directly hitting the web cache (and not the xml file) and the application pool account has write access to it, doesn't that mean a hacker can modify the object model that represent the xml file, regardless if the xml file is writable? By modifying the web cache, the hacker could inflict the same damage as if he had access to the web cache. I don't see how making the xml file read-only makes the website safer from hackers.
If I understand correctly, your xml file is read, turned into an object or a collection or some .NET data structure. And presumably only xml files of a certain schema can be successfully read this way.
I guess this depends on if there is something interesting in the xml file. If the xml file is the list of administrators, then as a hypothetical hacker I'd like to modify that file and add my name to the administrators list, which will result in an xml file that still serializes and deserializes to the data structure previous defined in code.
Another way to use write ability, would be to update a price list so that the prices are all free or heavily discounted.
If the XML file is a list of US states, then even if I could modify the list, I'm not sure what I could do with it outside of mischief, which is a larger concern for internet apps than for intranet apps.
I would put the file in the App_Data folder so that it can't be downloaded directly, which will make it harder for a hacker to make correct modifications to it... but security through obscurity is not really a good plan on it's own.
If the hacker were to hack the website, then security is compromised anyway. Allowing write access to the XML on it's own shouldn't be an issue, but I wouldn't give this access to any other files within your website.
I need very advanced and effective method of Preventing Users from Downloading file from website directly in asp.net.
Method should -
limit downloads,
limit time,
limit requests,
etc.
but should be downloadable by active login users
Delete the file from the server.
Any user trying to download it will not longer succeed.
You can put your files into a directory and configure that directory as not accessible by public users.
Store the files in a folder which is not accessible via IIS (i.e., not underneath your web application's root)
Create an .ashx generic handler which takes a file identifier (either filename, or ID of some sort) as a QueryString parameter.
In that .ashx, perform whatever checks you want to perform: is the user logged in? have they downloaded too many files? etc.
Then, if you decide that they should be allowed to download it, set the response headers appropriately and write the file out to Response.OutputStream
I have a flash upload component I want to use to upload multiple files. I'm using it in a MVC app and what I want to happen is that the user picks the files they want to upload, it uploads them and then displays a page showing all the files they have uploaded so they can add a description and select where to save them, and then save the files.
At the moment when files are uploaded the flash component calls a controller to process the files, this bit works fine, I can get the uploaded files and do what I like with them. The problem is is that I cannot just redirect to a View once the controllers done its work, because its the flash component calling the controller, not the page and so nothing happens when you try and do that.
I had attempted to save the files in the session and then forward the user on completion of the upload using some code in the flash actionscript, this however does not work, the session always turns up null. I had also considered actually saving the files to a temp location and then on the displaying page just listing all files in the temp location, but this is then going to involve saving the files twice, once to the temp directory and then to the actual place the user wants to put them, which I assume will be slow.
Any thoughts on the best way to do this?
Is your site using cookie based authentication? If so then the flash uploader needs to include the authentication cookie when uploading otherwise the upload will be seen as coming from a new user - this would explain your null values in the session state. If you are unable to get flash to post the cookie then you'll have to identify the user within the upload URL.
You should keep session state to a minimum or even better not use is at all so storing large amounts of data such as images in it is a bad idea.
With our applications we save all uploaded files to the database and then give them a unique Guid that is then used to retrieved/display them later. Within the database images could be associated with a user and in your case be marked as just uploaded so that when you redirect the user to the additional information page you know which images to display.
but this is then going to involve
saving the files twice, once to the
temp directory and then to the actual
place the user wants to put them
In relation to where the files are saved on the server you should not be allowing the user to determine where the files are saved.