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Posted 23 Jul 2006


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Open Windows Firewall During Installation

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23 Jul 2006CPOL2 min read
This test code will serve as an MSI custom action to open the Windows firewall after installation.


During the installation of my application, I needed to add it to the Windows firewall as an allowed application and open two ports for another application. This code will function as a custom action during the install to open the firewall on install and close it on uninstall. In trying to keep things as simple as possible, the following C# class library will be called from the setup - openFirewall() and closeFirewall().

First, I generated the FWSetupAction project as a C# class library. After that, I use the properties page to switch the output type to a console application to step through it with the debugger. When it's operational, switch back to the class library for integration with the MSI setup logic and incorporate it as a custom action.

After the initial project creation, rename Class1.cs to Firewall.cs in the Solution Navigator. If you're writing code anew, add the NetFwTypeLib reference first to allow intellisense to help you recognize the terms you'll be coding. This reference will be required for correct compilation, so whether you put it in before coding or after doesn't matter, but it will be needed. To add the reference, right click on References and select Browse. Browse to %windir%\system32\hnetcfg.dll and select it - the NetFwTypeLib will be created.

Edit the Firewall.cs class to have the following code:

using System;
using System.Collections.Generic;
using System.Text;
using System.Reflection;
using NetFwTypeLib;
using Microsoft.Win32;
namespace FWSetupAction
public class Firewall
    protected int[] discoPorts = { 0xD100, 0xD101 };
    protected INetFwProfile fwProfile;

    public void openFirewall()
        ///////////// Firewall Authorize Application ////////////
        String imageFilename = getImageFilename();
        NetFwAuthorizedApplications apps = fwProfile.AuthorizedApplications;
        INetFwAuthorizedApplication app = 
          ( INetFwAuthorizedApplication ) getInstance( "INetAuthApp" );
        app.Name = "Application Name";
        app.ProcessImageFileName = imageFilename;
        apps.Add( app );
        apps = null;

        //////////////// Open Needed Ports /////////////////
        INetFwOpenPorts openports = fwProfile.GloballyOpenPorts;
        foreach( int port in discoPorts )
            INetFwOpenPort openport = 
              ( INetFwOpenPort ) getInstance( "INetOpenPort" );
            openport.Port = port;
            openport.Protocol = NET_FW_IP_PROTOCOL_.NET_FW_IP_PROTOCOL_UDP;
            openport.Name = "New Open Port";
            openports.Add( openport );
        openports = null;
    } // openFirewall

    public void closeFirewall()
        String imageFilename = getImageFilename();
        INetFwAuthorizedApplications apps = fwProfile.AuthorizedApplications;
        apps.Remove( imageFilename );
        apps = null;
        INetFwOpenPorts ports = fwProfile.GloballyOpenPorts;
        ports.Remove( discoPorts[ 0 ], NET_FW_IP_PROTOCOL_.NET_FW_IP_PROTOCOL_UDP );
        ports.Remove( discoPorts[ 1 ], NET_FW_IP_PROTOCOL_.NET_FW_IP_PROTOCOL_UDP );
        ports = null;

    protected string getImageFilename()
        // Get install directory from the registry
        RegistryKey pRegKey = Registry.LocalMachine;
        pRegKey = pRegKey.OpenSubKey( "SOFTWARE\\Company Directory\\AppDir" );
        Object insDir = pRegKey.GetValue( "InstallDir" );
        return insDir + "RVP.exe";

    protected void setProfile()
        // Access INetFwMgr
        INetFwMgr fwMgr = ( INetFwMgr ) getInstance( "INetFwMgr" );
        INetFwPolicy fwPolicy = fwMgr.LocalPolicy;
        fwProfile = fwPolicy.CurrentProfile;
        fwMgr = null;
        fwPolicy = null;

    protected Object getInstance( String typeName )
        if( typeName == "INetFwMgr" )
            Type type = Type.GetTypeFromCLSID(
            new Guid( "{304CE942-6E39-40D8-943A-B913C40C9CD4}" ) );
            return Activator.CreateInstance( type );
        else if( typeName == "INetAuthApp" )
            Type type = Type.GetTypeFromCLSID(
            new Guid( "{EC9846B3-2762-4A6B-A214-6ACB603462D2}" ) );
            return Activator.CreateInstance( type );
        else if( typeName == "INetOpenPort" )
            Type type = Type.GetTypeFromCLSID(
            new Guid( "{0CA545C6-37AD-4A6C-BF92-9F7610067EF5}" ) );
            return Activator.CreateInstance( type );
        else return null;

    static void Main( string[] args )
        Firewall fw = new Firewall();

Once compiled, you're ready to test. Set a breakpoint on each of the firewall entry methods - openFirewall() and closeFirewall(), and step through the program. Use a DOS box to verify the operations. The netsh firewall command will verify the operation of the code:

  • netsh fire show allowed - shows the programs that are allowed
  • netsh fire show port - shows the ports that are open



This article, along with any associated source code and files, is licensed under The Code Project Open License (CPOL)

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Comments and Discussions

GeneralRe: This is not a feature, but a security leak Pin
Don Hamson27-Jul-06 4:23
MemberDon Hamson27-Jul-06 4:23 
GeneralRe: This is not a feature, but a security leak Pin
Member 1127725916-Mar-15 4:16
MemberMember 1127725916-Mar-15 4:16 

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