[pkg-gnupg-maint] Bug#931203: gpg has a serious performance problem on flooded certificates

[Daniel Kahn Gillmor]

Package: gnupg
Version: 2.2.16-2
Control: clone -1 -2
Control: affects -1 monkeysphere enigmail sks
Control: found -1 2.2.13-2
Control: found -1 2.2.12-1
Control: found -1 2.1.18-8~deb9u4
Control: forwarded -1 https://dev.gnupg.org/T4592
Control: reassign -2 monkeysphere 0.41-1
Control: retitle -2 monkeysphere-authentication chokes on flooded certificates

When an OpenPGP certificate is flooded with too many certifications, and
a GnuPG installation imports it into `pubring.gpg`, performance of gpg
is atrocious.  I've documented that performance problem at
https://dev.gnupg.org/T4592.

This is apparently breaking people's enigmail installations
(https://dev.gnupg.org/T3972#127338).

This is also an issue for monkeysphere-authentication, because it pulls
keys from the keyserver network and then tries to use them.  Any system
that has monkeysphere-authentication scheduled in a cronjob to pull from
the SKS keyserver network, for example, can get automatic heavy CPU
load, if one of the certificates they're pulling gets flooded like this.

A handful of (complementary) workarounds present themselves as an option
for the monkeysphere (and any other tools that are affected):

 * switch from the keyring format (pubring.gpg) to the keybox format
   (pubring.kbx), which has narrower limits about what it is willing to
   import.

 * do your fetches from the keyserver using "--import-options
   import-clean" -- while this won't fix everything, it'll still be
   useful.

 * fetch keys via other mechanisms, like WKD or DANE, instead of the SKS
   keyserver network.  Unfortunately, this only works for retrieving
   certificates by e-mail address, and requires cooperation from the
   domain owner to set it up.  It also doesn't provide revocation or
   subkey update necessarily, it could go stale.

 * use hkps://keys.openpgp.org instead of the SKS keyserver network --
   this won't let you fetch third-party certifications, but it will let
   you fetch revocations and key material updates.

Ultimately, we'll need a fix in GnuPG, though. (or for tools to move
away from using GnuPG as their OpenPGP implementation)

   --dkg
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