nwrickert
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| reply to EGeezer
Re: Is Portknocking "Real" Security?
Based on what I've read here, it appears that portknocking can be a useful part of an SSH implementation. But why port knocking?
Couldn't you achieve the same thing with a udp listener that can open the firewall for a particular connection in response to an encrypted and digitally signed udp packet? It seems to me that this would be more effective and simpler to implement. Moreover, it would work behind a NAT router, where I would only have to forward that one udp port instead of all of the ports that would be needed for port knocking.
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EGeezer
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| I'm not disputing that there are other ways to provide security. I'm just observing that knocking appears to provide a layer of security that would provide some protection. That's what I got from reading Daniel's article. I still don't see how the hacker in the scenario would proceed.
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Daniel
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2 edits | reply to nwrickert
Moreover, it would work behind a NAT router, where I would only have to forward that one udp port instead of all of the ports that would be needed for port knocking.
Holy God. You mean you've been arguing all this time against it and you don't even know how it works?
Portknocking only opens ONE (1) port, e.g. 22 for SSH.
»www.portknocking.org/
One source address, one port, for a short amount of time. And what you're talking about is called SPA, and it was mentioned earlier in the thread. I agree that it's an interesting alternative to the portknocking implementation, but ultimately it's pretty much the same.
The firewall is closed, but when the trusted client sends a secret stimuli the firewall opens up JUST FOR THEM -- keeping the rest of the world locked out. This is the same for both portknocking and SPA.
But dude...do you see now?
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nwrickert
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| said by Daniel  :Holy God. You mean you've been arguing all this time against it and you don't even know how it works? Portknocking only opens ONE (1) port, e.g. 22 for SSH. If you could avoid these unwarranted insults, perhaps intelligent discussion might break out.
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Daniel
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clubs: | Fair enough, my bad. I got a bit rowdy.
So, yeah...it's just one port, man. Does this change anything for you?
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TheWiseGuy
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| reply to nwrickert
said by nwrickert :But why port knocking? Couldn't you achieve the same thing with a udp listener that can open the firewall for a particular connection in response to an encrypted and digitally signed udp packet? It seems to me that this would be more effective and simpler to implement. Moreover, it would work behind a NAT router, where I would only have to forward that one udp port instead of all of the ports that would be needed for port knocking. That would be SPA or Single Packet Authorization.
(See the link I posted earlier)
Technically I would consider both a form of Port Knocking, since I believe the definition of port knocking used in the paper is valid and I expect there will be newer forms of Port Knocking that will add strength to port knocking as a security layer.
said by Sebastien Jeanquier :
"In broad terms, port knocking is a method for transmitting information across closed ports, with the aim of authenticating users before allowing them, and only them, to access a protected service.." Both SPA and the "Port Knocking Perl Prototype" seem to have strengths and weaknesses.
As examples
If you run SPA it can be attacked off line via a dictionary or Brute force attack.
With either method if you run a "listener" of some sort to check if the authorization should be granted you run the risk of the "listener" having a vulnerability. While the writer of the paper indicates that
said by Sebastien Jeanquier :
The knock daemon has the ability to read knocks out of the firewall log, or directly off of the wire using libpcap. Due to the way that this implementation deals directly with the bit-representation of the knocked ports, it would be quite difficult to compromise the daemon itself with maliciously crafted packets. See page 32 for his full discussion which is interesting.
IMO if you run the "Port Knocking Perl Prototype" you can in theory simply check the logs of the firewall and remove almost all of this risk.
I liked qrkx 's summary earlier, and agree with Daniel Port Knocking (including SPA) does add a layer of security, it is not the foolproof but no layer is foolproof. I also agree with you that "social engineering techniques" are the primary risk against a secured system/server but that does not make Port Knocking any less of a layer.
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nwrickert
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1 edit | reply to Daniel
So, yeah...it's just one port, man. Does this change anything for you? According to the doc "encoded in the form of connection attempts to closed ports, in which the port sequence forms the encoding,". You can't have much of a port sequence with only one port. In other words, it isn't going to work too well when you are behind an external firewall/router.
So sure, you add a security layer of some sort. But I have to remove an existing security layer (the external firewall), to be able to use it. In that case, when you are behind a typical NAT box, it may be a net loss in security.
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TheWiseGuy
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1 edit | Does this help?
»www.portknocking.org/view/about/requirements
Edit:
Assuming you want to run the server on a specific IP and do not need to dynamically select the IP, you should be able to forward the port (you would need to anyway) to the firewalled server and then read the logs as they come into that server. So I assume
whose rules can be dynamically modified.
is not absolutely needed for the router. I believe it needs to be able to log via syslog. |
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nwrickert
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| Does this help? From the linked reference, "Any *NIX host running IPCHAINS/IPTABLES is suitable."
However, most inexpensive broadband routers are not suitable. So this is mostly a geek technique, particularly for those enthralled by the gee-whiz nature of the methodology.
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TheWiseGuy
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| Not really, again if the router can log packets via syslog to the server machine, all you need to do is forward the Port to the firewalled server. The server then opens or closes its own port.
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Daniel
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1 edit | reply to nwrickert
However, most inexpensive broadband routers are not suitable. So this is mostly a geek technique, particularly for those enthralled by the gee-whiz nature of the methodology.
Ah, now I see where you're coming from. So if a security layer doesn't work on "inexpensive broadband routers" then it's essentially a toy technology? I think this illustrates why you're completely disjointed from those who are in support of this technology as a layer: you're thinking of things from a home/SOHO standpoint, and we're coming at it from a corporate perspective.
No offense to you, but this has largely been an enterprise discussion all along, so busting out now with "this doesn't work on my Linksys" isn't really a strong argument.
At any rate, can we agree that for corporate situations (where they're not likely to be using broadband routers) this is a decent layer? If so then I'll definitely agree that it might be overkill for the average home setup. 
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nwrickert
sand groper
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Geneva, IL | So if a security layer doesn't work on "inexpensive broadband routers" then it's essentially a toy technology? I never said that.
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Daniel
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clubs:
| said by nwrickert :However, most inexpensive broadband routers are not suitable. So this is mostly a geek technique, particularly for those enthralled by the gee-whiz nature of the methodology.
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nwrickert
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| Industrial CISCO routers are not using IP tables either. And if the firewall were running on CISCO equipment at our work, there is no way our servers would be given access to the firewall logs on those routers.
I provided an example with the broadband routers. I didn't say that's the only example.
I used broadband routers as my example, because I had already commented on them earlier in an earlier post. What you wrote in response to that earlier post was wrong and insulting.
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