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> First: no, not only is it not true that we must trust the DNS, but not having to trust the DNS is literally part of the thesis statement of SSL/TLS. Uh. Cert
by garaetjjte 10y ago
> First: no, not only is it not true that we must trust the DNS, but not having to trust the DNS is literally part of the thesis statement of SSL/TLS.
Uh. Certificates are issued by checking DNS entries, and you are saying that we don't have to trust it.
- tptacek 10y agoThat is correct, yes.
- snowwrestler 10y agoYour usual example here is how hard it is to get a domain-auth cert for google.com, but what about a small e-commerce site? What should they do to prevent a bad guy from getting a domain-auth cert by spoofing DNS? Honestly asking for my education (and others).
- tptacek 10y agoThey should get an OV cert and use HPKP for their domain. That is: if they're worried that a state-level attacker is going to MITM their users with a fake certificate.
- rocqua 10y agoOV certs do almost nothing to prevent MITM attacks. Unless you expect users to recognize when an OV cert is replaced with a DV one. Moreover, HPKP means that I have to trust my first visit to a site. Any new site could be MITMed. Heck, HPKP means that anyone that gets to MITM your domain can wreck it for however long a Pin is valid.
- snowwrestler 10y agoThanks. Is that attack only available to state-level attackers? I thought that--absent the measures you detail above--it was possible for a criminal enterprise to fool a CA into issuing a domain-authenticated cert.
- tptacek 10y agoThe attack is too complicated for fraudsters, because it's multi-stage. They have to perpetrate a heist to get the certificate, and then another heist to MITM people to use the certificate (you can potentially use the DNS for both attacks, but they're still different attacks). DNS spoofing is not common in the real world, because it has low payoff.
- snowwrestler 10y agoThank you.