Unblock File from within .net 4 c#

Question

Is there a possibility to unblock a file that is downloaded from the internet from within a c# program. Surfing the internet I have learned, that the information is written in an alternative stream of a (NTFS) file that contains the current zone information (value 3 is from the internet and is interpreted as blocked).

Is there a managed possiblity to either clear or change the zone information (unblock) of a file or is there a managed copy function that copies the files without the zone information? If not, how can I do with PInvoke but without including a foreign assembly (I'm not allowed to do this in a current project).

Contractive

@Sven: Thanks: I thought that I have exactly this written in my question. Is my english so bad? But thanks anyway... :) – Contractive

No, apparently my reading skills are, though. :) In my defense, it's after midnight here. Fwiw, you'll have to use PInvoke, as the .Net System.IO classes don't support alternate data streams. – Groundsill

See #605460 – Subdivision

Answer 1

It's stored in the :Zone.Identifier stream (more < c:\theapp.exe:Zone.Identifier) you need to use the native IO routines to manipulate them, here is a managed wrapper.

Stamina

While this may work for now, it is an implementation detail. The Persistent Zone Identifier object, as mentioned by @citizenmatt, is the bit responsible for creating these. As such, MS may at any time, via Windows update or OS version, change how/where that data is stored. – Contravene

Answer 2

Based on your input I have done the following code:

public class FileUnblocker {
    [DllImport("kernel32", CharSet = CharSet.Unicode, SetLastError = true)]
    [return: MarshalAs(UnmanagedType.Bool)]
    private static extern bool DeleteFile(string name);

    public bool Unblock(string fileName) {
        return DeleteFile(fileName + ":Zone.Identifier");
    }
}

Thanks to Stuart Dunkeld, Alex K(+1) and Sven to show me the direction.

UPDATE I have posted the code here for a feedback if it would work reliable in production environment. If someone want to use it, check out there.

Contractive

Updates like this should be posted as an edit to your question. – Contravene

Answer 3

The official way to manage this identifier is with the PersistentZoneIdentifier COM object: http://msdn.microsoft.com/en-us/library/ms537029(v=vs.85).aspx

Pubescent

Answer 4

I'm using .net 7, I've found these does the same thing.

Unblock:

void UnblockFile(string filePath)
{
    File.Delete(filePath + ":Zone.Identifier");
}

Block:

void BlockFile(string filePath)
{
    File.WriteAllText(filePath + ":Zone.Identifier", "[ZoneTransfer]\r\nZoneId=3");
}

Outpour

Answer 5

If all you want is to unblock files use a powershell command:

dir -r | unblock-files

change directory to the folder containing the files and run that command. The parameter -r is to list files in all sub-folders.

Hanahanae