OpenBSD Journal

e2k19 Hackathon Report: At e2k19 nobody can hear you scream (Claudio Jeker)

Contributed by Peter N. M. Hansteen on from the cooled crypto dept.

Fresh from the just concluded e2k19 hackathon, Claudio Jeker (claudio@) writes in:

After 2 years it was once again time to pack skis and snowshoes, put a satellite dish onto a sledge and hike through the snowy rockies to the Elk Lakes hut.

I did not really have much of a plan what I wanted to work on but there were a few things I wanted to look into. One of them was rpki-client and the fact that it was so incredibly slow. Since Bob beck@ was around I started to ask him innocent X509 questions ... as if there are innocent X509 questions! Mainly about the abuse of the X509_STORE in rpki-client. Pretty soon it was clear that rpki-client did it all wrong and most of the X509 verification had to be rewritten. Instead of only storing the root certificates in the store and passing the intermediate certs as a chain to the verification function rpki-client threw everything into it. The X509_STORE is just not built for such an abuse and so it was no wonder that this was slow.

Lucky me I pulled benno@ with me into this dark hole of libcrypto code. He managed to build up an initial diff to pass the chains as a STACK_OF(X509) and together we managed to get it working. A big thanks goes to ingo@ who documented most of the functions we had to use. Have a look at STACK_OF(3) and sk_pop_free(3) to understand why benno@ and I slowly turned crazy.

Our next challenge was to only load the necessary certificate revocation list into the X509_STORE_CTX. While doing those changes it became obvious that some of the data structures needed better lookup functions. Looking up certificates was done using a linear lookup and so we replaced the internal certificate and CRL tables with RB trees for fast lookups. deraadt@ also joined the rpki-client commit fest and changed the output code to use rename(2) so that files are replaced in an atomic operation. Thanks to this rpki-client can now be safely run from cron (there is an example in the default crontab).

I did not plan to spend most of my week hacking on rpki-client but in the end I'm happy that I did and the result is fairly impressive. Working with libcrypto code and especially X509 was less than pleasant. Our screams of agony died away in the snowy rocky mountains and made Bob deep dive into UVM with a smile since he knew that benno@ and I had it worse.

In case you wonder thanks to all changes at e2k19 rpki-client improved from over 20min run time to validate all VRPS to roughly 1min to do the same job. A factor 20 improvement!

Thanks to Theo, Bob and Howie to make this possible. To all the cooks for the great food and to Xplornet for providing us with Internet at the hut.

(Comments are closed)

  1. By Edward Ahlsen-Girard (Ed) on

    Glad to see that no extraordinary measures were required to maintain stove discipline.


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