Hi all, as you are very likely all aware, Dan Kaminsky uncovered a major exploit in RFC-compliant DNS caching servers the successful execution of which relies on port prediction/guessing. After quite some research, I have come up with the following facts which I want to cross-check with you guys so I can be _sure_. 1) The --random target for SNAT exists since 2.6.22 to allow 'fixing' of broken DNS servers in your NATted LAN along the lines of iptables -t nat -I POSTROUTING 1 -p udp -s 1.2.3.4 --dport 53 -j SNAT \ --to 1.2.3.4 --random Is that correct? 2) Unless there is a collision, the original UDP source ports for requests are kept the same. I.e. boxes within the NATted LAN which use random UDP ports are secure and neither the 2.4.x nor the 2.6.x series of kernels will make those ports predictable while NATting the packets. Is that correct? 3) Ever since a commit that went into 2.6.24 [1], UDP ports that are NATted are randomized by the NATting forewarder, anyway. This means that any DNS lookup made from within a NATted LAN secured with iptables to a DNS server outside of said NAT is secure by default. Is that correct? Thanks for any and all input. I am sure many people would like clarification on those points. Richard [1] http://git.kernel.org/?p=linux/kernel/git/torvalds/linux-2.6.git;a=commit;h=32c1da70810017a98aa6c431a5494a302b6b9a30 -- To unsubscribe from this list: send the line "unsubscribe netfilter" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
