Re: [TLS] [pkix] Cert Enumeration and Key Assurance With DNSSEC

Ralph Holz <> Mon, 04 October 2010 15:53 UTC

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Date: Mon, 04 Oct 2010 17:54:36 +0200
From: Ralph Holz <>
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Subject: Re: [TLS] [pkix] Cert Enumeration and Key Assurance With DNSSEC
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> But keep in mind that few TLS clients (such as browsers), currently
> support "pinning" of PKIX-authenticated server certs, so that on future
> connects only the very same server cert (with user-authenticated
> attributes other than DNS f.q.d.n) will be accepted from that server.
> In is very common misbehaviour in TLS clients to accept arbitrary other
> server certs on future connects, as long as the DNS f.q.d.n matches.

I have found during a few tests that some companies which give different
IPs for the same DNS name also run some servers with different certs
than the "main one". A closer look at the certs revealed that they had
been issued for the same domain and had been signed by the same CA, i.
e. they were perfectly valid. Pinning certs would prohibit this kind of

Although I am not sure it is intentional - my thought was that these
servers were just misconfigured (older cert?), as only very few
exhibited this behaviour.

Best regards,