What's the smartest way to prevent a textfile (e.g. xml) from being edited by a user?
I need to make sure that the file in which I store the usernames and there privileges for the desktop application can't be simply edited.
Maybe I can generate a certificate of the file and the desktop applications checks this?
I'm using C# in a WinForms app.
You could use File system permissions to prevent editing.
You could use encryption to make editing difficult
You could get a hash value for the file to detect editing.
I think encrypting the file, then decrypting it will be easiest. Though users might still be able to read the contents of the file if they're smart enough. e.g. reading the plain-text from memory
The simplest way is probably to use a database with username and password authentication.
The smartest is to encrypt it so that the data is not available to them.
However, if a user truly wants access to a file on their machine, they will get it. You can make it so that they cannot read anything useful or make useful edits, but if they want to, they will be able to edit the file.
Since your aim is to store users' privileges directly in an XML file, you need a level of security beyond just preventing users from editing the file. Even if you could (hypothetically) impose some restriction at the operating system level against editing the file, any administrative user could just edit the file on a different computer and then overwrite your protected version.
Thus, you have to assume that users can edit the file. The only recourse you have is to be able to identify when they have, and ignore their edits.
The approach you suggest of creating a certificate sounds exactly right. You could either compute a hash for the entire file, or could do so on a user-by-user basis (whichever makes most sense in your context), in either case using a private or secret key to ensure that someone editing the file cannot simply recompute the hash.
IMHO you can not guarantee no one can edit it, but you can encrypt the file to secure the information.
you can not guarantee as any one can boot the machine using disk start up for example and edit the text file simply.
Personally I don't think XML is the appropriate format for storing secure information in this case. The whole point of XML, compared to binary formats, is that it is human readable/editable. Use some kind of encrypted binary format with a known hash/crc that tells you if it's been interfered with if you want total security.
You can use cryptography, but use the DPAPI built into Windows as you will also have to store the encryption key safely, which again is another hassle.
The benefit of using DPAPI is that it uses a key unique to the user or computer, and is never disclosed, even to the programmer! But if you move the file onto another user's profile or computer, it will be unreadable.
If you MUST keep that data in a XML textfile you could consider digitally signing it by your application every time it is modified and checking the digital signature when you read the file.
More details on how to sign XML file and how to verify signature.
But I think it's better to just keep that kind of data in different formats - database, encrypted file, application properties...
Related
I am trying to save the username and password of user at c# console application. Hence there will be just one username and password that must be saved (It is like pin code). I don't want to use a Database for this. Using .txt will be irrational because anyone can see and find txt file and enter program.
I tried to use Properties.Resources but because of Resources are read-only, there is no way of changing password at runtime if user wants to change its password.
Properties.Resources.Admin_Mail = Reading;
It gives error because of the reason I mentioned above.
What should I use, I cannot find any suitable way for this problem on the internet.
I am not sure where you are at in your development journey.
You'll need system.io to read and write to the text file. I would give in a different extension then .txt.
https://learn.microsoft.com/en-us/dotnet/api/system.io?view=net-6.0
Consider using a SecureString type in C#
https://learn.microsoft.com/en-us/dotnet/api/system.security.securestring?view=net-6.0
Encrypt the data stored in the file.
https://learn.microsoft.com/en-us/dotnet/standard/security/encrypting-data
Decrypt the users entry to ensure it matches the file.
https://learn.microsoft.com/en-us/dotnet/standard/security/decrypting-data
There is a StackOverFlow link talking at the actually input.
Password masking console application
Sorry for just linking to references instead of a straightforward code answer, but I not sure of your intent and level of security you wish to provide.
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.
we have created an application like adobe reader to read a special encrypted document file format which does recognize only by our application.
what we want to do is to let user buy the application using his/her account from a website & after that we'll let him/her download that document using this program and start reading it.
here is our concerns:
1) document files should not be read in another user computer which means if user1 gives the raw downloaded file to user2 which has our application in his/her own computer the second user must not be able to read that file
2) after users download their files, they can just read those file offline (not constantly be online to be able to read)
3) this security must not break down easily because these document data are vital & the user information & application must not be hacked and cracked !
4) maybe later we want to have our android/IOS version so the solution must be cross platform
5) solution like providing login mechanism for each document won't work because users are able to give the copy of their own files together with their username & password to other users.
6) file encrypting mechanism must not break down by crackers so that they just decrypt the document & post the free version all around the internet
Do you have any programming method, security mechanism or suggestion ?
You could use public-key (or asymmetric) cryptography. You encrypt the document with the public key of the user. Then only people with access to the private key (ideally: only the user) can decrypt it.
However if the user has access to his own key (and he should), nothing can keep the user from decrypting the document and sharing it with others (or sharing his private key with others).
In the end: if a user, or the program needs access to the unencrypted product and the user has no interest in keeping the document secure, confidentiality can and - if the product is interesting enough - will be broken.
This is the problem with .NET it's easily reversed, because of the executables having a lot of meta data stored and that it does not compile to native (asm), but to IL. Your best bet would be to use an obfuscator and something like .NET Seal (However if I am correct it requires the users to be on the net) http://forum.elitevs.net/
Again you want to go cross platform and for C# to do that you'll have to use something like Mono:
http://www.mono-project.com/Main_Page
Although that would require the end user to also have mono.
Now to answer your "points".
1) Make each file and application share some sort of encryption that is unique to each file and application, making sure that the file only matches for the application one user have ex.
User X downloads the application.
User Y downloads the application.
Both downloads are unique with some sort of encryption algorithm or encryption key.
User X downloads Document A.
Document A will be sharing the same algorithm / key as User X's application which makes it unique to him only.
User X gives Document A to User Y.
As User Y's application does not share the same algorithm / key as User X then the Document is not readable.
2) I will referre to what I said first in my answer.
3) I will referre to what I said first in my answer.
4) I will referre to what I said first in my answer. However I want to point out that it's not entirely a bad idea, but it's something that should be taken into consideration if C# really is the language of choice for this.
5) I will reffere to answer #1 here.
6) I will reffere to answer #1 here.
If you are going to allow the user to download the file, then there is going to be no way to 100% secure it. The reason is, there must be a way to decrypt it so that the user can read it. This decryption process must occur on the user's machine, since the program to read it will have to decrypt it and open it on their machine.
Once the program to decrypt it is running on the user's machine, he can reverse engineer it and hack it (assuming he's clever enough).
That being said, there are many way to make it difficult to crack your decryption. Now if you take away the ability to read offline, you have more control. A hacker cannot run a disassembler or decompiler on your remote server.
Hope this info helps
I am working on an application that keeps track and uses files stored on the file system. Users are allowed to open, create, delete and move files in the file system. Meanwhile my application is not constantly running so I can't keep track of all changes real-time. Afterwards my application has to find out what file is whom (i.c. as identified in my application).
The most preferred solution for the users is that the application solves every change itself. Each user-interaction is less preferred.
One of my ideas was to use an attribute of a file and assign a key-value to it so when it has been identified once, it can always been recognized afterwards. But I don't know if there is such an attribute. This article didn't give much hope: There is in Windows file systems a pre computed hash for each file?.
Does somebody know if there is such an attribute I can use? And how can I used it in C#?
Is there anyone who is running up against this problem? And how did you solve it?
I'd like to hear good suggestions.
regards, Jaap
If your files don't leave NTFS, this is easily achievable by alternative data streams, where you can store your data along with files. This is more-or-less good article about ADS: http://www.flexhex.com/docs/articles/alternate-streams.phtml
There is another suitable method - it's very efficient, but also very complicated to use, it requires quite good knowledge about NTFS internals - USN Change Journal; see http://msdn.microsoft.com/en-us/library/windows/desktop/aa363798.aspx. With USN Change Journal, you can "get" very efficiently all files that were changed (even all change events) within specified time period.
Nevertheless, if your files leave NTFS realm, e.g. if it's copied to FAT32, contents of ADS is lost.
Relying on a File attribute is "dangerous" in that some user could alter the attribute while your program isn't running. This could lead you to believe that a certain file is (or isn't) tracked by the program while it really isn't.
I would suggest to keep track of the files in a database, XML, or some other file. When your application starts you read the file/db and check for new/deleted/editted files.
You could store a Hash of the files to find out if a file has been moved/editted. Keeping track of files that are moved AND editted is going to be pretty difficult. (I have no clue how you could achieve it)
PS: Have you considered making your application a Windows service? Having the file-management running in the background no matter if the GUI part of your application is running or not?
Good day, is there any option how to create a box, which cannot be seen from Windows? I would like to insert some files into this box. These files should be accessible only through my application, not from Windows. Thank you in advance.
How many files and how do you need to access them? If they are only for reading and you don't have too many, you always have the option to store them as a resource in your project. Have a look at this link on MSDN on how to store various file types directly inside your assembly.
NOTE: If you are planning on storing passwords or security-sensitive data, you shouldn't use this approach.
Another alternative would be to store you files inside a database. If you were to use something such as SQLite (here is the .Net data provider), Windows would have access to the database file, but not to the files contained within the database (which could be encrypted). Depending on your data, you'd have to store the file information as a binary large object (blob). See here for an example of how to do this.
It depends on the layer of abstraction you want. All files created by an application are at some level accessible by windows, however, you can mask the content of these files (i.e. encrypt them).
Generally speaking, you could still store the files in a folder, and apply encryption. Here's the msdn article on the point. The other issue is where do you store the key used for encryption.
A simple solution is to hard-code the key in some variable. However, if the assembly is decompiled, the key will become apparent. On the other hand, if you want the user that created the files to begin with, to be the only one to access the files, then you can use the Data Protection API.
If your question is how to the hide the box then you can set the "Visible" attribute to false no matter what control you are using for this "box".
if your box does not include a lot of files or not large file, you can try save it in a compress file like .zip and add a password for it. also add the hidden attribute on that box.