OpenPGP keyservers under attack

by Volker Weber

In the last week of June 2019 unknown actors deployed a certificate spamming attack against two high-profile contributors in the OpenPGP community (Robert J. Hansen and Daniel Kahn Gillmor, better known in the community as "rjh" and "dkg"). This attack exploited a defect in the OpenPGP protocol itself in order to "poison" rjh and dkg's OpenPGP certificates. Anyone who attempts to import a poisoned certificate into a vulnerable OpenPGP installation will very likely break their installation in hard-to-debug ways. Poisoned certificates are already on the SKS keyserver network. There is no reason to believe the attacker will stop at just poisoning two certificates. Further, given the ease of the attack and the highly publicized success of the attack, it is prudent to believe other certificates will soon be poisoned.

This attack cannot be mitigated by the SKS keyserver network in any reasonable time period. It is unlikely to be mitigated by the OpenPGP Working Group in any reasonable time period. Future releases of OpenPGP software will likely have some sort of mitigation, but there is no time frame. The best mitigation that can be applied at present is simple: stop retrieving data from the SKS keyserver network.

There is a personal message in there for the person who did this. Go read the whole thing.

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All true, but read what @FiloSottile has to say about this. The OpenPGP keyserver network was a good idea in its time, just like open SMTP relays were in the ’80s.

Running cryptographic infrastructure that can trivially be damaged beyond repair by bad actors, in today’s environment, is about as reasonable as running an open SMTP relay because it’s convenient.

Chris Ferebee, 2019-07-01

If you ever encounter a PGP key that claims to be mine, don't trust it.

Volker Weber, 2019-07-01

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