CODEWITHSUNDEEP
c#filepermissionsuac
njv299
njv299

Reputation: 91

Determining Write Permissions to the Application Folder

I have a C# application, and I need to dump some output to a log file during operation. I am wanting to give the user the option of where to locate the log file, but by the client request it needs to default to the current application location, which is normally /Program Files/.

When I deploy my application on a Win7/Vista machine, though, the application does not write the log file unless I run the program as an Administrator. At the same time, it seems to be silently handling the case where it cannot write the file, as I am currently handling all exceptions being thrown during the file creation and writing process.

I am currently trying to detect lack of write permission by both:

A) Creating a DirectorySecurity object by calling "Directory.GetAccessControl()" and

B) Checking security priviledges with the "SecurityManager.IsGranted(permissions)" method,

but A does not throw an exception when I expect it to, and B returns true every time.

I have seen numerous posts related to this topic, but they all give the solution of just writing to Application.UserAppDataFolder or some variation of it. My client has specifically asked to default to the current Application path, so I need to at least find a way to gracefully warn them when writing the log file is going to silently fail.

Note: My current code works find on Windows XP (since there are no UAC, I assume). Basically all I need to know is why all my calls are telling me that writing the file is going fine, when the file is never created at all unless I am running as Admin.

Thanks!

Upvotes: 6

Views: 3653

Answers (6)

Edward
Edward

Reputation: 11

I am experiencing the same problem. I have an xml file that i am writing to...When I install the app(C sharp) and try to run the application am getting an exception due to write permission. When I change the file permission (give read permission to users) it is working ok..

Upvotes: 1

Kate Gregory
Kate Gregory

Reputation: 18944

There are three ways your app can run - elevated, deliberately not elevated (manifest saying asInvoker), or accidentally not elevated (no manifest). Elevated apps will be able to write to Program Files. Deliberately not elevated apps will get access denied. Accidentally not elevated apps will succeed but the file will be written elsewhere. This last case is what's happening to you. It didn't silently fail. You just don't know where the files are. See http://www.gregcons.com/KateBlog/FindingFilesYoureSureYouWrote.aspx for screenshots.

Therefore if the users insist on the current directory, you should add a manifest requesting asInvoker. You will then get AccessDenied and they will see the error message. I think they are odd for wanting this. Ask them if they are ok with one extra click to find them: if so, keep your app using virtualization (I really disapprove) by having no manifest and then train them to click the Compatibility Files button. My preference: write elsewhere and manifest to asInvoker. My second choice: stick with current directory, no manifest, train them to find virtualized files. My third choice: stick with current directory, manifest to asInvoker, users see error messages when log files are not written, but logs are lost.

Upvotes: 2

Powerlord
Powerlord

Reputation: 88796

Windows Vista and 7 will write files to the Program Files directory just fine.

Well, not really, but the program thinks it's just fine. In reality, the file is written to the current user's VirtualStore directory; that is, in %userprofile%\AppData\Local\VirtualStore\Program Files

You can include a manifest file to disable this behavior for your application to get the results you expect.

Upvotes: 6

crashmstr
crashmstr

Reputation: 28573

Besides Stefan P.'s suggestion to elevate the app to run as admin, you could also modify the installation folder permission on install to to add the Users group to have write access. Then the application would work as well.

Moving the log file location would be the best option though.

Upvotes: 0

Jesper Larsen-Ledet
Jesper Larsen-Ledet

Reputation: 6723

The ultimate test for whether you have the rights to write a file is to open it for writing. I.e. 

try
{
    File.Open(path, FileMode.OpenOrCreate);
    ...
}
catch(SecurityException)
{
   ... it failed for security reasons
}
catch(Exception)
{
   ... it failed for other reasons
}

Upvotes: 0

Stefan P.
Stefan P.

Reputation: 9519

You can force the os to run your app as Admin.

<requestedExecutionLevel level="requireAdministrator" uiAccess="false" />

Upvotes: 2

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