[tor-dev] Torsocks 2.x issue - Need eyes on that

David Goulet dgoulet at ev0ke.net
Tue Oct 29 19:10:50 UTC 2013

On 29 Oct (14:58:44), Nick Mathewson wrote:
> On Tue, Oct 29, 2013 at 2:38 PM, David Goulet <dgoulet at ev0ke.net> wrote:
> > To be honest, I am not sure what's the right fix here or if there is any
> > way to lookup the symbol in a "special" way that would help here. Any
> > idea or questions are VERY welcome :).
> My first thought -- and I don't know how good it is -- is that perhaps
> you could just *not* look at syscalls that occur during the dlsym
> calls that you launch? In other words, disable the syscall override if
> the current thread is already inside the dlsym() call inside your
> syscall override.

That would work if there is a way I can "differ" the hijack of the
syscall symbol... Unfortunately, this is done at linking time thus
during run time, the syscall symbol is already hijacked by torsocks.

Let say we don't try to lookup the syscall symbol, the issue is that the
original syscall libc pointer will NOT exists within torsocks code so we
can't handle call to syscall() because we can't route it to libc. :S

It's really that we get in a kind of "infinite loop" where dlsym calls
syscall that calls dlsym and so on. But in the first place, we at least
need the libc syscall symbol so we can handle them.


> Would that work?  What would it break, if anything?
> -- 
> Nick
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