I'm working on a VB.NET (2010) project that will need to write text files to the end user's computer. I have read online that due to some user's security settings, that the safest place to write files to is the Application Data folder.
But what I would like to do (if possible) is allow the user to select where they want the files written to, via a SaveToFile dialog (I am using a SaveFileDialog in combination with My.Computer.FileSystem.WriteAllText).
So my question is... if I use a SaveFileDialog (as opposed to saving a file without using a dialog), does that mean that my files will always be written to wherever the user selects?
Or is it possible that the user could select a location (ie their "desktop"), and it would not write the file there, due to their security settings? (UAC, Firewall, etc).
If the latter is possible, is there anything I can suggest to the user that they can do that would enable my program to write files to wherever they select, and it would work 100% of the time?
Like maybe... if they right-click on my program's exe file and go to Properties > Security, and make sure the 'Write' permission is allowed, will that do the trick? Or is there more to it than that?
And does it mke any difference whether or not they are logged into their computer as "admin"?
I've read a lot of conflicting things about all of this online, so I'm just trying to getting a better understanding of it all so that I know how to proceed.
Thanks!
The [Save As] dialog will only let the users select a folder they have read and write acceess to and that is done for you by the Operating system . So that is the best option in my openion
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I have a text file. Now I have changed its file type from .txt to .abc. My VB.NET program loads the text into textboxes from that file. After changing the file type, however, other apps like NotePad and Word are able to open and read my .abc file.
Is there any way that only my application will be able to open/read from the file and no other app would be able to do so? What I mean is, suppose I have a PhotoShop document .psd file, no other app, rather that photoshop itself, can open it. How do I make my file unreadable by other apps?
There is no way to prevent an app that you don't develop from opening any file. The extensions are just there for helping us humans, and maybe a bit for the computer to know the default app you select for an extension.
Like you said, a .txt file can be opened by many many apps. You can open a .txt file with Notepad, Firefox, VSCode, and many others.
Same way, a .psd file can be opened by many many apps. You can open that .psd file with Photoshop, but also Notepad, Firefox, and VSCode, and probably the same apps as above.
The difference is which apps can read and understand the file.
In order to make a file not understandable by other apps, you need to make it into a format that cannot recognize, because you planned it "in secret".
Like Visual Vincent said above, you could encrypt the file in a way, or you can have a binary file, that basically only your app knows know to understand.
Since you dont own the app you want the file to be understood by, then you either have to accept that it can be opened by any app that can open files, or you can try to encrypt the file outside the app, or like zipping it with a password, and then decrypting or unzipping when you want to use it.
Firstly, any file can be read unless it is still open by a particular process or service. Even PhotoShop files can be 'read' by NotePad - try it!
So, an attempt at my first answer...
You can try a couple of methods to prevent opening the file, for instance, applying a file lock. As an example, SQL Server .mdf files are locked by the SQL Server service. This happens because the files are maintained in an open state, however; your application would have to remain running to keep these files open. Technically, though, the files can still be copied.
Another way is to set the hidden attribute for the file. This hides the file from the less savvy users, but it will be displayed if the user show's hidden files.
And my second answer: You refer to the format of files by saying only PhotoShop can read or write its own files (not true, but I know what you're saying).
The format of the file must be decided by yourself. You must determine how you are going to store the data that you output from your application. It looks like you have been attempting to write your application data into a text file. Perhaps you should try writing to binary files instead. Binary files, while not encrypted, as suggested by Visual Vincent in the comments to your question, still provide a more tailored approach to storing your data.
Binary files write raw binary data instead of humanised text. For instance, if you write an integer to the file it will appear as a string of four bytes, not your usual 123456789 textual format.
So, you really need to clarify what data you want to write to the file, decide on a set structure to your file (as you also have to be able to read it back in to your application) and then be able to write the information.
I've written a Python program with some UI and froze it using PyInstaller. The program writes to an xml document in the same directory, but not all of the users on the network have write permissions to this file. Rather than give everyone permissions to write to this file, is there a way to set the program's permissions to enable it to write there? That way regardless of who runs it the program will write to the xml, but any user who didn't originally have write permissions won't be able to go manually change any of the data in the file.
A stated by #c_str in the comments you can run the process as another user on windows.
On Linux you can also use setuid and setguid to let process have his owner´s permission instead of runner user permissions.
Even though this works, both methods are questionable as stated by #c_str in the comments above.
Hello can anyone explain me or give me some examples of how to lock a folder with VB.net.
I want to chose folder, set password for it and then lock it.
When i try to open that folder i want my app to popup asking for password, if password is ok then unlock folder if not do nothing.
I know how to do all except this autorun of my app when folder is accessed.
Thank you!
Your scheme as you described it doesn't mention encrypting files, and without encryption use of such "locking" is questionable.
Now, encryption or not, your only solution is a filesystem filter driver which will ask the password when the file is accessed, and then will allow or deny opening of the file (and on-the-fly encryption/decryption must be performed as well).
VB.NET can't be used to write a kernel-mode driver (you need deep knowledge of C and Windows internals and about 6 months of work to create a driver). You can use our CallbackFilter product, which provides a driver and lets you write business logic in user-mode.
on the Microsoft forum there is the following solution, maybe it's useful to you: http://social.microsoft.com/forums/en-US/softwareresources/thread/9a0f17af-928e-4732-a3ba-90d54ed961ea ; you may create the file they suggest dinamically by your software and then manage it.
I am writing a program in vb.net that requires a user to log in before he can use the application. The main user is created when the program is installed, similar to how windows works when it is installed.
The main user can add additional users to the program. I already know that I should store the passwords encrypted. My question is, where should I store the usernames and passwords? The registry, Isolated storage or .config file. I don't want any user to be able to modify/delete that file as the other user would obviously not be able to log in. Also, this file should be accessible for any user that logs into the computer.
The computer is not guaranteed to be connected to the internet, so it must be stored locally.
Thanks
To tell you the truth if someone has the will power to look for the file they will find it, so storage can help up security but I would focus on the contents of the file itself.
You could try to store the data of the application as a encrypted file which could stop the amateur attempts but as you are using the .net framework your program could could be decompiled and any symmetric encryption algorithms could be rendered useless.
I think your best bet would be to either generate a seed according to the computer the program is on, and if decryption fails call home or go into Lock Down.
Another option would be to store the encrypted (encrypted with your symmetric key) file and a hash file (in different locations probably). If the hash of the loaded file then does not match the hash file your program could then call home (If you have a home to call).
This is just a idea, haven't actually tried anything like this.
If you are not able to use windows users/credentials in any way on the machine, then there really is no absolute way to prevent the file from being removed/changed, Since anyone on the computer has the same access as the main user, who needs rights to modify the file in order for him to add users through the program.
The only way to do it for sure is to have the main user logon with a different user name, and set the file permissions on that file/folder to make sure that only the main user has modify permission to the file (and the other user account does not have the right to modify permissions). I know you said it wouldn't work in your environment(which is?) but you might be able to create users and run stuff under different credentials through your code without having the users log on any different.
The only crazy way I can think of is to create a service on the computer that once it starts running, it opens and holds a handle to that file with sharing set such that no other process can open the file for writing. You'd of course have to workout some way for the main user to be able to add users.
I've been working on making my app easier to use for administrators. One of the things I'd really like to do is allow admins to modify other user's settings from within the program -- while still making it possible for regular ol' users to modify their own settings, as my application isn't necessarily only for administrators who want to force users to use specific settings.
I thought of two possible ways of doing this:
1) Move the user setting file path from where it is now (CLSID_APPDATA, commonly Documents and Settings\Username) to a world-accessible path (CLSID_COMMON_APPDATA , commonly Documents and Settings\All Users). Then, save each user's settings to a unique file for the user (probably having a name which equals that of the user's textual SID), so the folder looks something like:
C:\Documents and Settings\All Users\My Company\My Program\settings\123-abc-456-def.settings
C:\Documents and Settings\All Users\My Company\My Program\settings\234-bcd-477-xyz.settings
C:\Documents and Settings\All Users\My Company\My Program\settings\946-hdc-743-ddd.settings
Pros:This allows an admin to see and directly modify any user's settings, because the COMMON_APPDATA path is the same for all users. This is how I'd really like it to be -- it's the most straightforward -- but there's a major con:
Cons:Permissions could be a problem. To allow regular users to save their settings, you'd have to allow users write access to the program's COMMON_APPDATA setting folder.
Of course, when the settings are saved and the setting file created on disk, you'd want to limit write access on the user's setting file to the user who the settings are for, and for admins, so that other limited user's can't modify them.
However, it could be that before a user has a chance to write their own settings from within the program, a savvy, malicious limited user creates a setting file for that specific user, without the knowledge of the user. If the limited user creates the file, that means they own the file... and then that user (who the settings are for) can't modify the settings anymore, unless an admin changes the permissions on the file.
An unlikely situation perhaps, but it still worries me.
2) Instead of moving the setting file path to a globally-accessible path and modifying the user's setting file directly, have my app create and save an "override" file in the app's CLSID_COMMON_APPDATA folder, to allow the admin to override the user's settings.
When my app loads for that user (who's settings were "overridden") it'll detect this file and load it instead of the regular setting file, which is located in CLSID_APPDATA (Documents and Settings\Username).
Pros:Permissions are easy to deal with.
By default, for the Documents and Settings\Username APPDATA folder, only admins and Username can access the files from within. So that in itself protects the user's own regular personal settings from other limited users.
To protect the "override" settings, my app can simply deny write access to the COMMON_APPDATA folder -- where the override file is written -- to all but administrators, and then that's that. These overriding settings will only be modifiable by admins.
Cons:This method is obviously more roundabout. If a user modifies his own regular personal settings, an admin won't see those changes -- the admin can only see the settings he's overriding the user's regular settings with (which he can force the user to use instead).
In some ways, this might be good, but... the fact that it's roundabout turns me off somewhat.
I'm interested to hear what you guys think about this. Which is my best option? I'm personally leaning more towards #2, because while it's less straightforward, it seems to be more secure and isn't so roundabout where it'd be confusing for an admin.
However, I'm also open to suggestions. Is there a superior option you think would work better?
EDIT 7/6/09: I should note that for option #2, the admin could not only override all user's settings with a single override file, but also override an individual user's settings with an override file specific to that user (just like with option #1, that file name would likely be that of the SID of the user who's settings are being overridden). Not sure if that was completely clear in the original post.
Unless there is more than one user account on each computer (i.e. a computer is used by more than one person), option two is the better choice.
Even if there is more than one user account on each computer, I think option two is still a better choice. Worst case, the administrator will have to change settings on a handful of accounts on the same computer instead of one.
If your facility allows random usage of any computer by any person, then option one is the better choice, since option two will make it too difficult to maintain that many different accounts on every computer.
Of course, you can always put the application settings in user folders on the server. That would make it very convenient for an administrator.
If the administrator already has rights to the user's directory where his setting's file is stored, wouldn't that already solve your problem? Either way though, it sounds like option 2 would be best, then you could have a single file that could override say a group of users, then each user have their own settings as well. Just so long as your application is smart enough to tell when to override a setting and when not too, option 2 shouldn't be that much of an issue.