Date: Wed, 09 Jul 2008 20:13:02 +0200 From: Florian Weimer <fw@...eb.enyo.de> To: oss-security@...ts.openwall.com Subject: Re: DNS vulnerability: other relevant software * Mark J. Cox: >> Additionally, Debian has noted (DSA 1605-1) that the GNU libc stub >> resolver could benefit from random query source ports as well, but >> no patches are currently available to implement this: > > Note that GNU libc stub resolver when used with a recent kernel > (2.6.24+) will give you random UDP source ports on each request > because of this Linux commit: > > http://git.kernel.org/?p=linux/kernel/git/torvalds/linux-2.6.git;a=commit;h=32c1da70810017a98aa6c431a5494a302b6b9a30 Is net_random() cryptographically secure? The paper referenced in the source doesn't talk about this. > Vendors may with to consider backporting that kernel patch as an > effective mitigation without requiring glibc changes (and with the > advantage of being able to be have a customized range using > ip_local_port_range etc) This still leaves the transaction ID generation to deal with. It's rdtsc on amd64 (don't know if this is good enough), but gettimeofday-based on some other architectures.
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