Fuzzing zeromq

Sep 18, 2012 | categories: python, zeromq, fedora View Comments

So, my project for Fedora Infrastructure (fedmsg) connects around with zeromq. Way back in the Spring of this year, skvidal suggested that I "fuzz" it and see what happens, "fuzz" meaning try to cram random bits down its tubes.

I have a little pair of python scripts that I carry around in my ~/scratch/ dir to debug various zeromq situations. One of the scripts is topics_pub.py; it binds to an endpoint and publishes messages on topics. The other is topics_sub.py which connects to an endpoint and prints messages it receives to stdout.

To fuzz the subscriber, I had it connect to a garbage source built with /dev/random and netcat. In one terminal, I ran:

$ cat /dev/random | nc -l 3005

and in the other, I ran:

$ python topics_sub.py "tcp://*:3005"

... and nothing happened.

To fuzz the publisher, I hooked /dev/random up to telnet:

$ python topics_pub.py "tcp://"
$ cat /dev/random | telnet 3005

... and it didn't fall over. Encouraging.

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