/******************************************************************************
PacketFilter::AddRemoveFilter - This method adds or removes a filter to an
existing interface.
*******************************************************************************/
DWORD PacketFilter::AddRemoveFilter( bool bAdd )
{
DWORD dwFwAPiRetCode = ERROR_BAD_COMMAND;
UINT64 filterid;
WCHAR openvpnpath[MAX_PATH];
FWP_BYTE_BLOB *openvpnblob = NULL;
try
{
if( bAdd )
{
FWPM_FILTER0 Filter = {0};
FWPM_FILTER_CONDITION0 Condition[2] = {0};
// Get OpenVPN exe path
GetModuleFileName(NULL, openvpnpath, MAX_PATH);
if (FwpmGetAppIdFromFileName0(openvpnpath, &openvpnblob) != ERROR_SUCCESS)
return ERROR_BAD_COMMAND;
// Prepare filter.
Filter.subLayerKey = m_subLayerGUID;
Filter.displayData.name = FIREWALL_SERVICE_NAMEW;
Filter.weight.type = FWP_EMPTY;
Filter.filterCondition = Condition;
Filter.numFilterConditions = 2;
// First filter. Block IPv4 DNS requests from openvpn.exe.
Filter.layerKey = FWPM_LAYER_ALE_AUTH_CONNECT_V4;
Filter.action.type = FWP_ACTION_BLOCK;
// First condition
Condition[0].fieldKey = FWPM_CONDITION_IP_REMOTE_PORT;
Condition[0].matchType = FWP_MATCH_EQUAL;
Condition[0].conditionValue.type = FWP_UINT16;
Condition[0].conditionValue.uint16 = 53;
Condition[1].fieldKey = FWPM_CONDITION_ALE_APP_ID;
Condition[1].matchType = FWP_MATCH_NOT_EQUAL;
Condition[1].conditionValue.type = FWP_BYTE_BLOB_TYPE;
Condition[1].conditionValue.byteBlob = openvpnblob;
/* Filter.layerKey = FWPM_LAYER_ALE_AUTH_CONNECT_V4;
Filter.action.type = FWP_ACTION_PERMIT;
*/
// Add filter condition to our interface. Save filter id in filterids.
dwFwAPiRetCode = ::FwpmFilterAdd0( m_hEngineHandle,
&Filter,
NULL,
&filterid);
printf("Filter (Block IPv4 DNS) added with ID=%I64d\r\n", filterid);
filterids.push_back(filterid);
// Second filter. Block IPv6 DNS requests from svchost.exe.
Filter.layerKey = FWPM_LAYER_ALE_AUTH_CONNECT_V6;
// Add filter condition to our interface. Save filter id in filterids.
dwFwAPiRetCode = ::FwpmFilterAdd0(m_hEngineHandle,
&Filter,
NULL,
&filterid);
printf("Filter (Block IPv6 DNS) added with ID=%I64d\r\n", filterid);
filterids.push_back(filterid);
// Third filter. Permit all IPv4 traffic from TAP.
Filter.action.type = FWP_ACTION_PERMIT;
Filter.layerKey = FWPM_LAYER_ALE_AUTH_CONNECT_V4;
Condition[1].fieldKey = FWPM_CONDITION_IP_LOCAL_INTERFACE;
Condition[1].matchType = FWP_MATCH_EQUAL;
Condition[1].conditionValue.type = FWP_UINT64;
for (std::vector<uint64_t>::iterator tapluid = tapluids.begin();
tapluid != tapluids.end(); ++tapluid) {
uint64_t tapluid64 = *tapluid;
Filter.layerKey = FWPM_LAYER_ALE_AUTH_CONNECT_V4;
Condition[1].conditionValue.uint64 = &tapluid64;
// Add filter condition to our interface. Save filter id in filterids.
dwFwAPiRetCode = ::FwpmFilterAdd0(m_hEngineHandle,
&Filter,
NULL,
&filterid);
printf("Filter (Permit all IPv4 traffic from TAP) added with ID=%I64d\r\n", filterid);
filterids.push_back(filterid);
// Forth filter. Permit all IPv6 traffic from TAP.
Filter.layerKey = FWPM_LAYER_ALE_AUTH_CONNECT_V6;
// Add filter condition to our interface. Save filter id in filterids.
dwFwAPiRetCode = ::FwpmFilterAdd0(m_hEngineHandle,
&Filter,
NULL,
&filterid);
printf("Filter (Permit all IPv6 traffic from TAP) added with ID=%I64d\r\n", filterid);
filterids.push_back(filterid);
}
}
else
{
for (int i = 0; i < filterids.size(); i++) {
dwFwAPiRetCode = ::FwpmFilterDeleteById0(m_hEngineHandle,
filterids[i]);
}
filterids.clear();
}
}
catch(...)
{
}
return dwFwAPiRetCode;
}
DWORD
add_block_dns_filters(HANDLE *engine_handle,
int index,
const WCHAR *exe_path,
block_dns_msg_handler_t msg_handler
)
{
FWPM_SESSION0 session = {0};
FWPM_SUBLAYER0 *sublayer_ptr = NULL;
NET_LUID tapluid;
UINT64 filterid;
FWP_BYTE_BLOB *openvpnblob = NULL;
FWPM_FILTER0 Filter = {0};
FWPM_FILTER_CONDITION0 Condition[2] = {0};
DWORD err = 0;
if (!msg_handler)
{
msg_handler = default_msg_handler;
}
/* Add temporary filters which don't survive reboots or crashes. */
session.flags = FWPM_SESSION_FLAG_DYNAMIC;
*engine_handle = NULL;
err = FwpmEngineOpen0(NULL, RPC_C_AUTHN_WINNT, NULL, &session, engine_handle);
CHECK_ERROR(err, "FwpEngineOpen: open fwp session failed");
msg_handler(0, "Block_DNS: WFP engine opened");
/* Check sublayer exists and add one if it does not. */
if (FwpmSubLayerGetByKey0(*engine_handle, &OPENVPN_BLOCK_OUTSIDE_DNS_SUBLAYER, &sublayer_ptr)
== ERROR_SUCCESS)
{
msg_handler(0, "Block_DNS: Using existing sublayer");
FwpmFreeMemory0((void **)&sublayer_ptr);
}
else
{ /* Add a new sublayer -- as another process may add it in the meantime,
* do not treat "already exists" as an error */
err = add_sublayer(OPENVPN_BLOCK_OUTSIDE_DNS_SUBLAYER);
if (err == FWP_E_ALREADY_EXISTS || err == ERROR_SUCCESS)
{
msg_handler(0, "Block_DNS: Added a persistent sublayer with pre-defined UUID");
}
else
{
CHECK_ERROR(err, "add_sublayer: failed to add persistent sublayer");
}
}
err = ConvertInterfaceIndexToLuid(index, &tapluid);
CHECK_ERROR(err, "Convert interface index to luid failed");
err = FwpmGetAppIdFromFileName0(exe_path, &openvpnblob);
CHECK_ERROR(err, "Get byte blob for openvpn executable name failed");
/* Prepare filter. */
Filter.subLayerKey = OPENVPN_BLOCK_OUTSIDE_DNS_SUBLAYER;
Filter.displayData.name = FIREWALL_NAME;
Filter.weight.type = FWP_UINT8;
Filter.weight.uint8 = 0xF;
Filter.filterCondition = Condition;
Filter.numFilterConditions = 2;
/* First filter. Permit IPv4 DNS queries from OpenVPN itself. */
Filter.layerKey = FWPM_LAYER_ALE_AUTH_CONNECT_V4;
Filter.action.type = FWP_ACTION_PERMIT;
Condition[0].fieldKey = FWPM_CONDITION_IP_REMOTE_PORT;
Condition[0].matchType = FWP_MATCH_EQUAL;
Condition[0].conditionValue.type = FWP_UINT16;
Condition[0].conditionValue.uint16 = 53;
Condition[1].fieldKey = FWPM_CONDITION_ALE_APP_ID;
Condition[1].matchType = FWP_MATCH_EQUAL;
Condition[1].conditionValue.type = FWP_BYTE_BLOB_TYPE;
Condition[1].conditionValue.byteBlob = openvpnblob;
err = FwpmFilterAdd0(*engine_handle, &Filter, NULL, &filterid);
CHECK_ERROR(err, "Add filter to permit IPv4 port 53 traffic from OpenVPN failed");
/* Second filter. Permit IPv6 DNS queries from OpenVPN itself. */
Filter.layerKey = FWPM_LAYER_ALE_AUTH_CONNECT_V6;
err = FwpmFilterAdd0(*engine_handle, &Filter, NULL, &filterid);
CHECK_ERROR(err, "Add filter to permit IPv6 port 53 traffic from OpenVPN failed");
msg_handler(0, "Block_DNS: Added permit filters for exe_path");
/* Third filter. Block all IPv4 DNS queries. */
Filter.layerKey = FWPM_LAYER_ALE_AUTH_CONNECT_V4;
Filter.action.type = FWP_ACTION_BLOCK;
Filter.weight.type = FWP_EMPTY;
Filter.numFilterConditions = 1;
err = FwpmFilterAdd0(*engine_handle, &Filter, NULL, &filterid);
CHECK_ERROR(err, "Add filter to block IPv4 DNS traffic failed");
/* Forth filter. Block all IPv6 DNS queries. */
Filter.layerKey = FWPM_LAYER_ALE_AUTH_CONNECT_V6;
err = FwpmFilterAdd0(*engine_handle, &Filter, NULL, &filterid);
CHECK_ERROR(err, "Add filter to block IPv6 DNS traffic failed");
msg_handler(0, "Block_DNS: Added block filters for all interfaces");
/* Fifth filter. Permit IPv4 DNS queries from TAP.
* Use a non-zero weight so that the permit filters get higher priority
* over the block filter added with automatic weighting */
Filter.weight.type = FWP_UINT8;
Filter.weight.uint8 = 0xE;
Filter.layerKey = FWPM_LAYER_ALE_AUTH_CONNECT_V4;
Filter.action.type = FWP_ACTION_PERMIT;
Filter.numFilterConditions = 2;
Condition[1].fieldKey = FWPM_CONDITION_IP_LOCAL_INTERFACE;
Condition[1].matchType = FWP_MATCH_EQUAL;
Condition[1].conditionValue.type = FWP_UINT64;
Condition[1].conditionValue.uint64 = &tapluid.Value;
err = FwpmFilterAdd0(*engine_handle, &Filter, NULL, &filterid);
CHECK_ERROR(err, "Add filter to permit IPv4 DNS traffic through TAP failed");
/* Sixth filter. Permit IPv6 DNS queries from TAP.
* Use same weight as IPv4 filter */
Filter.layerKey = FWPM_LAYER_ALE_AUTH_CONNECT_V6;
err = FwpmFilterAdd0(*engine_handle, &Filter, NULL, &filterid);
CHECK_ERROR(err, "Add filter to permit IPv6 DNS traffic through TAP failed");
msg_handler(0, "Block_DNS: Added permit filters for TAP interface");
out:
if (openvpnblob)
{
FwpmFreeMemory0((void **)&openvpnblob);
}
if (err && *engine_handle)
{
FwpmEngineClose0(*engine_handle);
*engine_handle = NULL;
}
return err;
}
