I am writing log for my application at a path saying :-
"C:\Folder1\Folder2\Myfile.txt" (Configurable)
if this file does not exist I am creating folder structure and file inside my code(If there is no C drive I pop up a message saying log directory doesnt exist).
In code review a colleague said that I should not create folder and files using code rather should ask the client to create the file and only perform write operation on this file.
He says there are security issues with this but not sure what, so I thought of posting it here.
Please help me deciding whether I should create file if not exist or ask the client to create on every installation.
What are the security implications with the first approach?
The write issues are that the user trying to create in the C root folder, may not have permissions to create it there. Never assume the user is an admin always.
Also this is the problem with windows' UAC which will be a problem.
Yes there could be issues. Your program will most likely run under the interative user account and therefore be subject to any UAC conditions imposed on it.
One approach, if this is just a log file, would be to use a temporary file, so use:
http://msdn.microsoft.com/en-us/library/system.io.path.gettempfilename.aspx
This should be created in a an area local to the logged on user that should allow writing of files.
The security issue i see is the ability of your web application to access and write the files inside the directory (configurable, as you mentioned).
To verify the the access by checking the permissions given to the account under which your apppool is running
or through code see this
No code is inherently unsafe. This all depends on how rest of your code looks like, but as a general rule of thumb you should limit which files your application can access and how it can access them. Limit this as much as possible, without damaging your applications functionality.
Security vulnerabilities which may come from this is allowing user to read file which he shouldn't read, or write to an important file and damage it that way. For example, if file path is being created using user input, user may modify the path so that he accesses file which is not allowed to access.
If you create a path like so:
string filePath = "c:\\mysafefolder\\" + fileName;
and user enters a relative path, for example ..\Windows\Passwords.txt he will effectively gain access to c:\windows\passwords.txt.
If you configure your application to block access to any part of file system except mysafefolder, this attempt to read a secret file will fail.
This is just an example of what might happen, and why it is a good idea to limit your application permissions. Your code might be perfectly safe at this point, but limiting permissions is thinking ahead.
Related
I'm using FAC and adding a new access rule to write.exe. When I right click and check the properties it shows the new rule with "Deny" checked for write. However when I run the write.exe it still is able to write.
Is there a different way for modifying a file's access?
It looks like you are misinterpreting how file permissions work. You don't give 'files' permission to write something, you can only give users or groups permissions to do stuff.
An executable file always runs with the credentials of the user that invoked the program. If that user has permissions to write files in a certain location, the program will be able to do so.
You can change the permissions on the target (the folder or file being written to), for example by making it read only for everyone.
Okay, so I am creating a c# winforms application.
I want to write/read from binary data file. But, I want to put that file in a folder somewhere and I do not want anyone to be able to delete or edit the file. I only want the program that uses the file to be able to access it.
Is this possible? I looked into MSDN's structure on file security and as I researched it I saw people complain that if you limit the file to a user then that person can just override the privileges and make it editable.
Also, I thought about how this would actually work considering in essence I would like a process to edit the file only and that process could have varying process ID's if it is opened and closed over time, seems tough.
Any thoughts?
Even though this will not satisfy all your requirements you can try IsolatedStorage (System.IO.IsolatedStorage Namespace).
How to write and read file in IsolatedStorage
The System.IO.IsolatedStorage namespace contains types that allow the
creation and use of isolated stores. With these stores, you can read
and write data that less trusted code cannot access and prevent the
exposure of sensitive information that can be saved elsewhere on the
file system. Data is stored in compartments that are isolated by the
current user and by the assembly in which the code exists.
Additionally, data can be isolated by domain. Roaming profiles can be
used in conjunction with isolated storage so isolated stores will
travel with the user's profile. The IsolatedStorageScope enumeration
indicates different types of isolation. For more information about
when to use isolated storage
You can prevent file access while your program is running if you open it exclusively.
However, when the program is not running, the file is no longer protected. So someone would just need to kill the program in order to access the file.
In order to protect the file while your program is not running, you'd need to set up a user account and assign it a password which is only known to the program. Then set the permissions of the file so that only your user can access the file.
However, any administrator can take over the ownership of the file, so even permission protection is useless.
Finally, someone can even take the hard disk out of the PC and read the raw data.
You might also think about whether you want to protect the file or the file content. If the file content is sensitive, think about encryption.
It really depends on your needs, which option to choose.
If you have control over the target filesystem prior to install then setup some file permissions and go from there. The user accessing the folder will need read permissions at minimum.
Run the app under a security group and assign persmissions to the folder and files with that security group. Revoke access for others and make it readonly
Windows 10 version 1709 introduced Controlled Folder Access. This allows you to whitelist applications that can modify certain folders. You cannot restrict Read access.
well, I have the same issue and I did some research on this subject and I found that secure your information in a accesspoint database or any other Microsoft data base with password and only one specific app that have the password will have the permission to do read/write to these information.
My application basically creates an XML file in C:\ProgramData\MyAppFolder and dumps config settings in it.
I need to allow even standard users to have permission to add or delete settings to these config files. Right now I see that standard users only have read/execute permission but not "Full Control".
I've seen other questions being answered with ways to modify permissions to that particular folder but I don't want to change the default permission level, since it might be reset by a system admin.
If C:\ProgramData can't give that access to all users, is there any folder that best suits the needs of application?
EDIT:
My initial question might be misleading. I don't want to give rights to users, but rather allow the application to modify the XML file when it is run by all users.
DECISION:
I think changing the permissions while creating the folder in ProgramData is the only option.
And if that's not possible, CommonDocuments is the way to go.
Thanks Eve.
I would use a folder in the Environment.SpecialFolder enum.
Example:
var path = Environment.GetFolderPath(Environment.SpecialFolder.ApplicationData);
Assuming you have an installer for your application, your installer can create a subfolder in the common appdata directory (aka C:\ProgramData) which your application will have read/write access to. Depending on your choice of installation technology you can set the permissions on that folder as well, although that may be overkill. I know with WiX basically all you have to do is a per-machine installation and make sure that sub folder gets created.
Users should not be allowed to write arbitrary data to this directory. This is equivalent to regular users being able to modify the C:\Users\AllUsers directory. If users need to be modifying this directory you have serious design flaws and should reconsider this approach. What should happen is the users are given GUI interface to interact with that manipulates these values behind the scenes without giving them direct access, similar to how getters/setters work in most programming languages. Needless to say it is a very large security hole when regular users can corrupt a system for other users.
UPDATE
I don't want to give users direct access to the file. My question
might have been misleading. I want to allow the program to have full
control on the file even when it being run by all users. I'm actually
doing this: "users are given GUI interface to interact with that
manipulates these values behind the scenes without giving them direct
access"
This article which has far too much information to post here, will provide details on remaining secure as to not leak permissions. The first thing you want to do is make sure that your application user is in its own group and cannot login/have any special permissions. What you can than do is have this group added to the directory with write permissions, which would allow this application to perform these tasks. If that is not possible you will need to work within UAC to not break the security of the system as is detailed in the article above.
Second Update
Thanks for the link. Any suggestions on some other folder which can do
the job, rather than messing with the permissions?
Sure you can write it into the directory where the application is written to, i.e. C:\Program Files\Some Awesome Program, this keeps everything in one place, and you only have to worry about your user/group and anything that the person who installed it has allowed for. It also prevents other people from messing with it unless of course they are administrators.
In a WPF application I use .txt files for holding some information. An application can read and write data from/to .txt file. Everything is OK, but the problem is that, to achieve this purpose, I have to grant writing access rights to these files for a user of an application and so, he/she gets the possibility to edit these files manually.
How could I set editing .txt files access rights for an application without granting the same level of rights to a user?
Edited (added):
After getting some comments and answers, I put the question this way (just to make my question more clear and not restricted to user access rights scope): How I could prevent the user from changing the file manually?
Encrypt it, or digital sign it
I'm going to presume that you are not trying to prevent the user from changing the file manually, you just want to prevent the extra step of specifically assigning rights to the file.
You are most likely writing to a file that is in a protected area (an area that became protected after UAC was introduced). To avoid this, write your file to one of the "approved" areas, such as %APPDATA%. Here is a list of a few more (assuming C is your boot drive):
C:\Users\username\Documents
C:\Users\username\AppData\Local
C:\Users\username\AppData\Roaming
C:\Users\Public\Documents
C:\ProgramData
This article has a whole bunch of info around that which you can cherry pick bits from.
This might be an overkill, but you could create a service that runs on a different user account, which can edit the file. Then your application would use that service to access the file.
This way you can prevent unwanted changes and/or log every change to the file.
I have a windows Application that stores certain files in a directory. I would like to know if there is a way in .net that I can restrict users not to have access to that directly (by just going to that directory in windows, and grab files) so only my application can add/verify/delete a file in that directory.
Could you use the Isolated Storage in .Net? While, it isn't necessarily restricted away from your users it may be a lot harder to find.... (stores under the local settings\application data\isolated storage for the logged in user)
Via code you work with it by using / importing the System.Io.IsolatedStorage and then you can create directories, files, etc... normal.
You also don't have to keep track of the actual directory on the HD it's in as .Net manages this. Maybe a nice plus.
This is only possible if your application runs with different credentials than the user running the application.
By default all applications run with the credentials of the user who launched the process. This means the application has the same directory and file restrictions as the user. Without a different account, the application can only decrease it's ability to access the file system, not increase it.
Dealing with the file system is evil in general. Even if you could get the user to not play in that directory you still can't trust the results will be in the exact same state as you left them. It's possible for other users, physical disk corruption or any number of other things to corrupt your files.
The only way to sanely program the file system is to expect failure from the start and count yourself lucky when it actually works.
The application needs to run as a specific user - and that user will always have the same rights as your application. You can, potentially, make a service that runs as an administrator to prevent standard users from accessing a directory, but the administrator will still be able to change things in the directory.
I suggest you look for another approach for your problem. There are potentially alternatives - perhaps you should consider keeping some type of encrypted hash on the directory contents. That would at least allow you to verify that the contents have not been changed, although it won't prevent the change from occurring.
As others have mentioned, you need the application to act as a different user than the ones currently logged in. You should look into 'impersonation', here are some links that can get you started on getting your application to act as a different user when performing certain tasks:
http://csharptuning.blogspot.com/2007/06/impersonation-in-c.html
http://www.codeproject.com/KB/cs/cpimpersonation1.aspx
The easiest (although not secure in any way) method, would be to use a hidden folder, which the users know nothing about. so \servername\hiddenfiles$
A more secure alternative would be to change the credentials the program is using to access the folder. Is it necessary for them to access it as themselves?
An alternative would be to create a dummy account for each user, where they do not know the password. Make it relate to their windows login, so domain\myname becomes domain\mynamehidden. Then use this to connect to the directory.
This will ensure everything can be audited nicely too.
Look at FileSystemWatcher - it doesn't prevent from changes in directory, but allows to notify program about changes in dir.