[tor-dev] Design for an exit relay scanner: feedback appreciated

ra r.a at posteo.net
Thu Oct 10 11:39:19 UTC 2013

On Wednesday 09 October 2013 23:44:18 Philipp Winter wrote:
> I am working on a Python-based exit relay scanner which should detect
> malicious and misbehaving exits.  The design should have a reasonable
> balance between being fast/parallel and stressing the network as little as
> possible.
> I came up with the following three steps:
> 1.  Spawn a "parent" Tor process to get an up-to-date consensus.
> 2.1 For every selected exit relay, spawn a lightweight Tor process.
> 2.2 The consensus is copied from the "parent" process to the lightweight
>     process' data directory.  That way, the consensus has to be downloaded
> only once.
> 2.3 Every lightweight Tor process has the following configuration:
>     ---
>     SOCKSPort auto
>     ControlPort 0
>     __DisablePredictedCircuits 1
>     UseEntryGuards 0
>     FetchServerDescriptors 0
>     DataDirectory <data_directory>
>     ExitNodes <exit_relay>
>     ---
>     Entry guards are not used to distribute the load.  Predicted circuits
> are disabled to prevent expensive creation of circuits which would not be
> used anyway.  In addition, I am considering adding "EntryNodes" or
> "Bridge" to concentrate the first hop's load on machines under my control.
> 3.  torsocks is then used to establish decoy connections over the
> respective exit relay.  After that, the process is terminated.
> Any thoughts on how to further improve the design or ideas for a better
> one?

There is no need to spawn multiple Tor processes if you do circuit building 
and stream handling on your own.

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