Firewall Wizards mailing list archives
Re: GXD vs. SPF
From: "Ryan Russell" <ryanr () sybase com>
Date: Sat, 26 Sep 1998 13:15:12 -0700
I'll have to qualify my answers a bit :)
Generic Proxy security vs. SPF session security. Given a specific traffic session, ignoring the whole packet-level attack catagory:
I wouldn't ignore packet-level attacks, I think that's the pertinant issue, unless I misunderstand what you mean by packet-level attack.
If the GXD simply reassembles segments to TCP windows and passes them on
to
the target, only using sequence numbers to keep track of the TCP session, would a SPF provide better validation of a session than a generic proxy?
If I assume that the SPF doesn't try to do something extra like filter HTTP pieces, etc... then the GXD will be better. I don't know that validation is the right term, but the GXD will do better reformatting of the stream (the stream itself, not the data within the stream.) Put it this way.. one of the things I've asked for in the past in my ideal SPF is that it reassemble fragments, drop option bits (configurably, of course) possibly buffer packets, perhaps making 2 packets into 1, etc. In other words, the default behaviours you get with any simply TCP relay across a host's IP stack. For TCP, all of the "state" that a FW-1 maintains is the same as what a regular IP stacks checks for for all TCP connections. I don't know enough details about it, but I think SOCKS is an example of your GXD.
The security stack would be:
AG SPF GXD Packet Filter
If you want to consider SPFs that only pass or not pass a packet as-is (with perhaps the exception of what's needed to do NAT) then reverse SPF and GXD. This is assuming least secure at the bottom, and most secure at the top. Ryan
Current thread:
- GXD vs. SPF Stout, Bill (Sep 25)
- Re: GXD vs. SPF Paul D. Robertson (Sep 29)
- <Possible follow-ups>
- Re: GXD vs. SPF Ryan Russell (Sep 29)
- Re: GXD vs. SPF Frederick M Avolio (Sep 29)
- RE: GXD vs. SPF Stout, Bill (Sep 29)
- RE: GXD vs. SPF Ryan Russell (Sep 30)
- Re: GXD vs. SPF ark (Sep 30)