[dns-operations] Does DNSSEC provide any mitigation for SSL bugs, like Apple's?

Paul Wouters paul at cypherpunks.ca
Mon Feb 24 18:48:06 UTC 2014

On Mon, 24 Feb 2014, DTNX Postmaster wrote:

> Last Friday, Apple released a patch for iOS 6/7 that fixes a bug in
> their recent SSL implementation. Without the fix, iOS is vulnerable to
> MITM attacks by attackers 'in a privileged network position', allowing
> them to intercept and influence SSL connections. OS X Mavericks (10.9)
> is still vulnerable at this time.
> There's been quite a bit of discussion about this over the past few
> days, but DNSSEC has been kind of absent from that.
> I've been wondering whether DNSSEC would provide any mitigation for
> such an attack, if there validating resolver between me and the
> attacker? As this is kind of at the edge of my current understanding of
> things, I figured I'd ask here.

If your zone is signed, and you publish a TLSA record, then you would
be proteced (providing apple does not screw up this code either)

An attacker can with-hold or modify the TLSA DMSSEC record, which should
cause the TLS implementation to hard fail. If the attacker lets the TLSA
record through, then your TLS client knows what to expect, and should
abort when it is something unexpected.

Note though, that TLSA can pin either the CA or the EE cert. If you pin
the CA cert, then an attacker could just get _any_ cert from the same CA
and still subvert you. If you had choosen to pin the EE cert, then the
attack would have failed completely.


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