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NeT Firewall puts its packet filter between TCP/IP protocol driver and network interfaces. Winpcap installs its own protocol driver which works at the same level as TCP/IP (in parallel) and not intercepted by NeT Firewall. Basically, if you expect high security you should avoid having any other protocls (like winpcap) installed on the system. Primary purpose of NeT Firewall is protecting TCP/IP stack (not winpcap or any other custom protocol).
In general it is possible to intercept other protocols (like winpcap, ndisuio and etc..) in addition to TCP/IP protocol however this approach has some serious disadvantages (may break third-party NDIS intermediate drivers functionality, custom protocols and etc.) and since NeT Firewall is oriented on users who know what happens on their systems it is implemented on the current way.
first of all I excuse for I’m late on answering you, I was busy with university: my porfessor Federico Simonetti of University of Milan says hello to you
My warm regards to Federico, I hope he is doing well 🙂
What I’d like to ask you is: is there any way to make NetFW look at the PORT command in the control connection on 21 TCP port to automatically open the port the server wants to use to transfer data? As an example, Netfilter/IpTables can do it, and other commercial firewalls as well.
Yes this is possible but, heh, not implemented yet and the only known solution is opening port 20 for everyone. 😕 Dynamic rules (temporary rules created under certain conditions) are planned to be implemented, but it still needs time. In the meantime only Stealth 3rd level takes into account FTP protocol realization details so outgoing FTP can work in active mode.
Please send your registration e-mail (registrtion name or any other information we could use) and approximate date of purchase to support@ntkernel.com so we could identify your order.
P.S. Some FTP relative information http://slacksite.com/other/ftp.html
With the FW on 3rd level security if I permit 21/TCP out and I block all the other outgoing traffic passive ftp doesn’t work.
FTP active mode uses two TCP sessions, one on server port 21 is a control channel and another data channel on server port 20. Control channel is established by client and data channel is established by server as a response on PORT command.
In passive mode both control and data channels are established by client. Data channel uses arbitrary ports >1024 on both server and client sides. In you case blocking all outgoig connections except port 21 does not allow client to establish data channel and FTP in passive mode does not work.
The new version of NeT Firewall 2.3.2.3 has been released. We have updated the interpretation of IN/OUT keywords for TCP protocol, now it is applied to incoming/ougoing connections instead of incoming/outgoing packets. For other protocols IN/OUT interpretation remains the same. This should help to avoid missunderstandings in the future.
Basically using atexit() the way you did is not correct, you should pass a static function to atexit() instead of C++ class method. Also, since you are making the windows service you can release interfaces when your service process is stopped instead of using atexit().
From the design point of view I would create a C++ classe to wrap each interface and manipulated adapter thru this class ( ReleaseInterface functionality could be placed into the class destructor). Some more advanced WinpkFilter code can be downloaded from this page http://www.ntkernel.com/w&p.php?id=31 once you are a registered customer.
Well, you are right, but this is not about statefull inspection but the way the rules were originally implemented. IN means incoming packets, OUT means outgoing packets (in current implementation specifying only IN or only OUT for TCP protocol is senseless) and it is not exactly the same as IPFW rules where IN means incoming connection, OUT means outgoing connection for TCP. I agree that this may confuse a bit and probably it makes sense to change this behavoiur in order to avoid missunderstandings. Thanks for pointing this.
The rule you have created allows any system connect your port (from any port) 80 and connecting any your local port from port 80 what really breaks any security. Basically if you want to allow any kind of outgoing connections you are supposed to use on the the Stealth Security levels and create rules to drop undesired outgoing connections and may be some rules to open local ports if you also work as server. High Securty level was designed for servers which are supposed not to go outside world but just open some local ports to provide services for their users.
Adapters are bridged at the Etherent level and still have different IP’s if assigned so.
Does this software work like a bridge under XP with only one IP for the 2 connection?
No.
Regarding MTU: As far as I know, windows default MTU for ethernet adapters is 1500. I always attach a 20 bytes key to outgoing UDP packets.
Can I conclude from this that I might have a problem only with packets whose total length is 1480 bytes or more ?Yes, you will have problems with packets which size is equal or close (so you don’t have 20 bytes in reserve) to MTU. There is a special API in WinpkFilter SetMTUDecrement. In your case if maximum size of the attached data is 20 bytes so you should call SetMTUDecrement with 20 as a parameter, please note that this API adds a driver specific value into the registry and requires reboot to take an effect (driver reads this value from the registry during start up).
Can I catch packets that are directed either to 127.0.0.1 or to the local IP ? are those packets passed down the TCP stack or are they redirected by Windows back to the application at higher levels ?
Packets directed to 127.x.x.x or local IP never reach NDIS level and processed internally by TCP/IP. However, these data can be intercepted at the TDI level http://www.ntkernel.com/w&p.php?id=8 and http://www.ntkernel.com/w&p.php?id=24
Just thought to mentioned that I’m using the runtime libraries that are available at the web site (hxxp://www.ntoskrnl.com/downloads/winpkflt_rtx86.zip).
These binaries have no limitations.
Well, first of all I would start this application under debugger and check where it stops (or what is it doing) when network is frozen. Since this is a packet filtering application the network freeze can be easily caused by application hang (some dead lock or endless loop).
Also, I think it is important to mention that you should set MTU decrement if you are attaching additional data to the packets to the maximum size of the attached data. The total size of the ethernet frame should not exceeed 1514 bytes. I can’t see from your code if any length checks are implemented.
First of all the trial version on site is limited to capture 100 packets per boot.
If you are using full registered version then have you tried to run Local Host Monitor application on that system? If it works fine then the problem is relative to your code (and to advise anything I have to see more than one line), if it also does not intercept packets then it is probably driver relative. Please clarify.
Not sure what exactly code you need, but this question was already discussed here http://www.ntkernel.com/forum/viewtopic.php?t=19 along with some code postings.
That can be a problem, dynamic hooking into system stack (with dynamically loadable NDIS IM driver under Windows 2000+ and dynamic hooking driver for earlier Windows versions) can be implemented bu it less reliable and more complex than static (in case of IM driver reboot still can be required in some cases).
