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Message-ID: <871upgi1pl.fsf@mid.deneb.enyo.de>
Date: Mon, 27 Feb 2012 19:13:42 +0100
From: Florian Weimer <fw@...eb.enyo.de>
To: oss-security@...ts.openwall.com
Subject: Re: Attack on badly configured Netfilter-based firewalls
* Eric Leblond:
> I've discovered a generic attack on firewall using Application Level
> Gateway (like Netfilter or Checkpoint).
This is rediscovered every two to five years. Here's mine
(from 2005, but it's been proposed before):
<http://www.enyo.de/fw/security/java-firewall/>
> Secure use of iptables and connection tracking helpers:
> http://home.regit.org/netfilter-en/secure-use-of-helpers/
I think your filters aren't effective against sandboxed Java code on
the client.
I think there are other client-side sandboxes which allow de-facto
unrestricted access (with server cooperation). Doesn't Flash require
just a policy file on the server to open up arbitrary ports?
You could exclude the magic Silverlight port range:
| One additional restriction on using the sockets classes is that the
| destination port range that a network application is allowed to
| connect to must be within the range of 4502-4534.
<http://msdn.microsoft.com/en-us/library/cc645032%28v=vs.95%29.aspx>
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