Adding an Application Rule to Allow Dynamic Edge Traversal

Article
05/31/2018
This example adds an application rule to allow dynamic edge traversal using the Windows Firewall with Advanced Security APIs.
In order for Windows Firewall to dynamically allow edge traversal traffic, the following two items must be done:
The application must use the IPV6_PROTECTION_LEVEL socket option on the listening socket and set it to PROTECTION_LEVEL_UNRESTRICTED when the application wants to allow edge traffic.
The Windows Firewall rule added for the application must set edge traversal option to NET_FW_EDGE_TRAVERSAL_TYPE_DEFER_TO_APP.
This sample only illustrates one of the edge traversal option values. For more information on these values, see NET_FW_EDGE_TRAVERSAL_TYPE.
/********************************************************************
Copyright (C) Microsoft. All Rights Reserved.

Abstract:
    This C++ file includes sample code that adds a firewall rule with
 EdgeTraversalOptions (one of the EdgeTraversalOptions values).

********************************************************************/

#include <windows.h>
#include <stdio.h>
#include <netfw.h>
#include <strsafe.h>

#pragma comment(lib, "ole32.lib")
#pragma comment(lib, "oleaut32.lib")

#define STRING_BUFFER_SIZE  500     


// Forward declarations
HRESULT    WFCOMInitialize(INetFwPolicy2** ppNetFwPolicy2);
void       WFCOMCleanup(INetFwPolicy2* pNetFwPolicy2);
HRESULT    AddFirewallRuleWithEdgeTraversal(__in INetFwPolicy2 *pNetFwPolicy2);


int __cdecl wmain()
{
    HRESULT hrComInit = S_OK;
    HRESULT hr = S_OK;
    INetFwPolicy2 *pNetFwPolicy2 = NULL;

    // Initialize COM.
    hrComInit = CoInitializeEx(
                    0,
                    COINIT_APARTMENTTHREADED
                    );

    // Ignore RPC_E_CHANGED_MODE; this just means that COM has already been
    // initialized with a different mode. Since we don't care what the mode is,
    // we'll just use the existing mode.
    if (hrComInit != RPC_E_CHANGED_MODE)
    {
        if (FAILED(hrComInit))
        {
            wprintf(L"CoInitializeEx failed: 0x%08lx\n", hrComInit);
            goto Cleanup;
        }
    }

    // Retrieve INetFwPolicy2
    hr = WFCOMInitialize(&amp;pNetFwPolicy2);
    if (FAILED(hr))
    {
        goto Cleanup;
    }

    // Add firewall rule with EdgeTraversalOption=DeferApp (Windows7+) if available 
    //   else add with Edge=True (Vista and Server 2008).
    AddFirewallRuleWithEdgeTraversal(pNetFwPolicy2);

Cleanup:

    // Release INetFwPolicy2
    WFCOMCleanup(pNetFwPolicy2);

    // Uninitialize COM.
    if (SUCCEEDED(hrComInit))
    {
        CoUninitialize();
    }
   
    return 0;
}

// Add firewall rule with EdgeTraversalOption=DeferApp (Windows7+) if available 
//   else add with Edge=True (Vista and Server 2008).
HRESULT    AddFirewallRuleWithEdgeTraversal(__in INetFwPolicy2 *pNetFwPolicy2)
{
    HRESULT hr = S_OK;
    INetFwRules *pNetFwRules = NULL;
    
    INetFwRule  *pNetFwRule = NULL;
    INetFwRule2 *pNetFwRule2 = NULL;

    WCHAR pwszTemp[STRING_BUFFER_SIZE] = L"";

    BSTR RuleName = NULL;
    BSTR RuleGroupName = NULL;
    BSTR RuleDescription = NULL;
    BSTR RuleAppPath = NULL;


    //  For localization purposes, the rule name, description, and group can be 
    //    provided as indirect strings. These indirect strings can be defined in an rc file.
    //  Examples of the indirect string definitions in the rc file -
    //    127                     "EdgeTraversalOptions Sample Application"
    //    128                     "Allow inbound TCP traffic to application EdgeTraversalOptions.exe"
    //    129                     "Allow EdgeTraversalOptions.exe to receive inbound traffic for TCP protocol 
    //                          from remote machines located within your network as well as from 
    //                          the Internet (i.e from outside of your Edge device like Firewall or NAT"

    
    //    Examples of using indirect strings -
    //    hr = StringCchPrintfW(pwszTemp, STRING_BUFFER_SIZE, L"@EdgeTraversalOptions.exe,-128");
    hr = StringCchPrintfW(pwszTemp, STRING_BUFFER_SIZE, L"Allow inbound TCP traffic to application EdgeTraversalOptions.exe");
    if (FAILED(hr))
    {
        wprintf(L"Failed to compose a resource identifier string: 0x%08lx\n", hr);
        goto Cleanup;        
    }
    RuleName = SysAllocString(pwszTemp);
    if (NULL == RuleName)
    {
        wprintf(L"\nERROR: Insufficient memory\n");
        goto Cleanup;
    }
    //    Examples of using indirect strings -
    //    hr = StringCchPrintfW(pwszTemp, STRING_BUFFER_SIZE, L"@EdgeTraversalOptions.exe,-127");
    hr = StringCchPrintfW(pwszTemp, STRING_BUFFER_SIZE, L"EdgeTraversalOptions Sample Application");
    if (FAILED(hr))
    {
        wprintf(L"Failed to compose a resource identifier string: 0x%08lx\n", hr);
        goto Cleanup;        
    }
    RuleGroupName = SysAllocString(pwszTemp);  // Used for grouping together multiple rules
    if (NULL == RuleGroupName)
    {
        wprintf(L"\nERROR: Insufficient memory\n");
        goto Cleanup;
    }
    //    Examples of using indirect strings -
    //    hr = StringCchPrintfW(pwszTemp, STRING_BUFFER_SIZE, L"@EdgeTraversalOptions.exe,-129");
    hr = StringCchPrintfW(pwszTemp, STRING_BUFFER_SIZE, L"Allow EdgeTraversalOptions.exe to receive \
       inbound traffic for TCP protocol from remote machines located within your network as well as \
       from the Internet (i.e from outside of your Edge device like Firewall or NAT)");
    if (FAILED(hr))
    {
        wprintf(L"Failed to compose a resource identifier string: 0x%08lx\n", hr);
        goto Cleanup;        
    }
    RuleDescription = SysAllocString(pwszTemp);
    if (NULL == RuleDescription)
    {
        wprintf(L"\nERROR: Insufficient memory\n");
        goto Cleanup;
    }

    RuleAppPath = SysAllocString(L"%ProgramFiles%\\EdgeTraversalOptions\\EdgeTraversalOptions.exe");
    if (NULL == RuleAppPath)
    {
        wprintf(L"\nERROR: Insufficient memory\n");
        goto Cleanup;
    }

    hr = pNetFwPolicy2->get_Rules(&amp;pNetFwRules);

    if (FAILED(hr))
    {
        wprintf(L"Failed to retrieve firewall rules collection : 0x%08lx\n", hr);
        goto Cleanup;        
    }

    hr = CoCreateInstance(
        __uuidof(NetFwRule),    //CLSID of the class whose object is to be created
        NULL, 
        CLSCTX_INPROC_SERVER, 
        __uuidof(INetFwRule),   // Identifier of the Interface used for communicating with the object
        (void**)&amp;pNetFwRule);

    if (FAILED(hr))
    {
        wprintf(L"CoCreateInstance for INetFwRule failed: 0x%08lx\n", hr);
        goto Cleanup;        
    }

    hr = pNetFwRule->put_Name(RuleName);
    if ( FAILED(hr) )
    {
        wprintf(L"Failed INetFwRule::put_Name failed with error: 0x %x.\n", hr);
        goto Cleanup;
    }

    hr = pNetFwRule->put_Grouping(RuleGroupName);
    if ( FAILED(hr) )
    {
        wprintf(L"Failed INetFwRule::put_Grouping failed with error: 0x %x.\n", hr);
        goto Cleanup;
    }

    hr = pNetFwRule->put_Description(RuleDescription);
    if ( FAILED(hr) )
    {
        wprintf(L"Failed INetFwRule::put_Description failed with error: 0x %x.\n", hr);
        goto Cleanup;
    }

    hr = pNetFwRule->put_Direction(NET_FW_RULE_DIR_IN);
    if ( FAILED(hr) )
    {
        wprintf(L"Failed INetFwRule::put_Direction failed with error: 0x %x.\n", hr);
        goto Cleanup;
    }

    hr = pNetFwRule->put_Action(NET_FW_ACTION_ALLOW);
    if ( FAILED(hr) )
    {
        wprintf(L"Failed INetFwRule::put_Action failed with error: 0x %x.\n", hr);
        goto Cleanup;
    }

    hr = pNetFwRule->put_ApplicationName(RuleAppPath);
    if ( FAILED(hr) )
    {
        wprintf(L"Failed INetFwRule::put_ApplicationName failed with error: 0x %x.\n", hr);
        goto Cleanup;
    }

    hr = pNetFwRule->put_Protocol(6);  // TCP
    if ( FAILED(hr) )
    {
        wprintf(L"Failed INetFwRule::put_Protocol failed with error: 0x %x.\n", hr);
        goto Cleanup;
    }

    hr = pNetFwRule->put_Profiles(NET_FW_PROFILE2_DOMAIN | NET_FW_PROFILE2_PRIVATE);
    if ( FAILED(hr) )
    {
        wprintf(L"Failed INetFwRule::put_Profiles failed with error: 0x %x.\n", hr);
        goto Cleanup;
    }

    hr = pNetFwRule->put_Enabled(VARIANT_TRUE);
    if ( FAILED(hr) )
    {
        wprintf(L"Failed INetFwRule::put_Enabled failed with error: 0x %x.\n", hr);
        goto Cleanup;
    }


    // Check if INetFwRule2 interface is available (i.e Windows7+)
    // If supported, then use EdgeTraversalOptions
    // Else use the EdgeTraversal boolean flag.

    if (SUCCEEDED(pNetFwRule->QueryInterface(__uuidof(INetFwRule2), (void**)&amp;pNetFwRule2)))
    {
        hr = pNetFwRule2->put_EdgeTraversalOptions(NET_FW_EDGE_TRAVERSAL_TYPE_DEFER_TO_APP);
        if ( FAILED(hr) )
        {
            wprintf(L"Failed INetFwRule::put_EdgeTraversalOptions failed with error: 0x %x.\n", hr);
            goto Cleanup;
        }
    }
    else
    {
        hr = pNetFwRule->put_EdgeTraversal(VARIANT_TRUE);
        if ( FAILED(hr) )
        {
            wprintf(L"Failed INetFwRule::put_EdgeTraversal failed with error: 0x %x.\n", hr);
            goto Cleanup;
        }
    }

    hr = pNetFwRules->Add(pNetFwRule);
    if (FAILED(hr))
    {
        wprintf(L"Failed to add firewall rule to the firewall rules collection : 0x%08lx\n", hr);
        goto Cleanup;        
    }

    wprintf(L"Successfully added firewall rule !\n");

Cleanup:
   
    SysFreeString(RuleName);
    SysFreeString(RuleGroupName);
    SysFreeString(RuleDescription);
    SysFreeString(RuleAppPath);

    if (pNetFwRule2 != NULL)
    {
        pNetFwRule2->Release();
    }

    if (pNetFwRule != NULL)
    {
        pNetFwRule->Release();
    }

    if (pNetFwRules != NULL)
    {
        pNetFwRules->Release();
    }

    return hr;
}


// Instantiate INetFwPolicy2
HRESULT WFCOMInitialize(INetFwPolicy2** ppNetFwPolicy2)
{
    HRESULT hr = S_OK;

    hr = CoCreateInstance(
        __uuidof(NetFwPolicy2), 
        NULL, 
        CLSCTX_INPROC_SERVER, 
        __uuidof(INetFwPolicy2), 
        (void**)ppNetFwPolicy2);

    if (FAILED(hr))
    {
        wprintf(L"CoCreateInstance for INetFwPolicy2 failed: 0x%08lx\n", hr);
        goto Cleanup;        
    }

Cleanup:
    return hr;
}


// Release INetFwPolicy2
void WFCOMCleanup(INetFwPolicy2* pNetFwPolicy2)
{
    // Release the INetFwPolicy2 object (Vista+)
    if (pNetFwPolicy2 != NULL)
    {
        pNetFwPolicy2->Release();
    }
}
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