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How would it be identified as anything other than a routine cert rotation? You would have to have proof that you were being served different certs for the same

by 5ilv3r 10y ago

How would it be identified as anything other than a routine cert rotation? You would have to have proof that you were being served different certs for the same endpoint from different devices or locations, AND find someone who cares and is not under some influence. That sounds difficult for you, but easy for a central entity to detect. Ads follow me around between devices and locations, so I am quite sure a certificate could.

schoen 10y ago
The certificate is presented when fairly little information has been sent by your browser, so it's tough to target it more specifically than source IP address and OS/browser. There are a lot of ideas for catching this and some of them are starting to work, like HPKP pinning and preloads, and in the long run Certificate Transparency (including not accepting certs that haven't been publicly disclosed). If you use HTTPS Everywhere, you have an option to submit certs that you see to the EFF SSL Observatory. I don't mean to minimize the threat; I think there are lots of sites and browsers against which misissued certs can still be successfully used today without detection, and it's important to keep working on making that no longer true.
pfg 10y ago
If a site uses key pinning (e.g. via HPKP), the site is in control of telling you which keys are acceptable, so there would be no way to pretend it's a routine rotation after your first site visit (unless the site is cooperating, in which case you're screwed anyway). Certificate Transparency would also help here, as it would allow site owners to monitor the logs for any certificates they did not request. This is more about detection as opposed to prevention (though the chilling effect of easier detection would help with prevention, I suppose). Admittedly, this is probably something only a couple of large, security-conscious organizations do (like, for example, Facebook, which detected that someone was issuing certificates against internal policy, though not maliciously in that case).

by 5ilv3r 10y ago

schoen 10y ago

The certificate is presented when fairly little information has been sent by your browser, so it's tough to target it more specifically than source IP address and OS/browser. There are a lot of ideas for catching this and some of them are starting to work, like HPKP pinning and preloads, and in the long run Certificate Transparency (including not accepting certs that haven't been publicly disclosed). If you use HTTPS Everywhere, you have an option to submit certs that you see to the EFF SSL Observatory. I don't mean to minimize the threat; I think there are lots of sites and browsers against which misissued certs can still be successfully used today without detection, and it's important to keep working on making that no longer true.

pfg 10y ago

If a site uses key pinning (e.g. via HPKP), the site is in control of telling you which keys are acceptable, so there would be no way to pretend it's a routine rotation after your first site visit (unless the site is cooperating, in which case you're screwed anyway). Certificate Transparency would also help here, as it would allow site owners to monitor the logs for any certificates they did not request. This is more about detection as opposed to prevention (though the chilling effect of easier detection would help with prevention, I suppose). Admittedly, this is probably something only a couple of large, security-conscious organizations do (like, for example, Facebook, which detected that someone was issuing certificates against internal policy, though not maliciously in that case).